AlAzmi Radhi

8/3/2019 AlAzmi Radhi

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THE EFFECTS OF DIFFERENT SYNTHESIS CONDITIONS ON SODALITECRYSTALMORPHOLOGY

A Thesis Presented toThe Faculty of the

Fritz J. and Dolores H. RussCollege ofEngineering and Technology

Ohio UniversityIn Partial Fulfillment

Of the Requirement for the Degree

Master of Scienceby

Radhi AI-AzmiJune, 2001


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IIIAcknowledgements

I would like to take this opportunity to thank my father, my mother, and my wifefor their support and encouragement. Moreover, I would like to thank my advisor Dr.y alene Young for all the assistance and advice that she has provided throughout thiswork.


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List ofTablesList ofFigures

Table ofContentslV

PagesVI

VII

Chapter I Introduction 11.1 Objective 31.2 Atmospheric Chemistry 31.3 Water Interference 41.4 Water Removal 5

Chapter II2.1

2.2

Literature ReviewZeolitesSodalite

7

78

Chapter II Experimental Methods 113.1 Sodalite Synthesis 113.1.1 Sodalite Base Synthesis 123.2 AnalysisMethod 123.3 X-Ray Diffraction 163.4 Scanning Electron Microscopy 183.5 Water Removal Experiment 20


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3.63.7

Table of Contents (continued)

Regeneration of SodaliteSodalite Non-Interference with NMHC

v

Page2223

Chapter IV Results and Discussion 274.1 Synthesis Results 274.1.1 X-Ray Diffraction Results 274.1.2 Scanning Electron Microscopy Results 334.2 Variables Effect Estimation 364.3 Water Removal Results 394.4 Sodalite Regeneration Results 454.5 Non-Interferencewith NMHC Results 46

Chapter V

References

Conclusions and Recommendations 51

53

Appendix A X-Ray Diffraction Pattern of Sodalite

Appendix B Scanning Electron Microscopy Images

55

69


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VIList of Tables

Pages1-1 Water Content (mg) of one-liter air sample at l bar 52-1 Kinetic Diameter (c ) for different molecules 93-1 Sodalite Test Matrix 153-2 Variables high and low levels 163-3 SOS Standard Gas Composition 244-1 XRD Results for the 32 experiments 284-2 Sodalite spherical crystallite diameter 334-3 Variable effect estimates 364-4 Factorial design analyses input matrix 384-5 Percentage ofwater adsorbed by sodalite from batch number 10 444-6 Percentage ofwater adsorbed by sodalite from batch number 13 444-7 Results from blank and sodalite run 50


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List of Figures

1-1 Scanning Electron Micrograph ofCrystallites from Prior work showingtwo distinct morphologies (Brown, 2000)

VII

Pages

2

2-1 Sodalite ~ - c a g e structure. Vertices present Silicon or Aluminum atoms.Lines represent bridging Oxygen atoms 11

2-2 Sodalite ~ - c a g e stacked 113-1 Simulated XRD powder pattern of sodalite 173-2 Reflection of x-rays from two planes of atoms in a solid 193-3 Scanning electron microscope diagram 213-4 Water removal apparatus 223-5 Water removal apparatus: humid air supply, bypassing sodalite 223-6 Water removal apparatus: humid air supply, through sodalite 233-7 Water removal apparatus: dry air supply, through sodalite 243-8 Organic non-interference test system 263-9 SOS Standard chromatogram output 284-1 XRD pattern for experiment number 7 indicating significant amorphous

material and a crystalline phase other than sodalite 314-2 XRD pattern for experiment number 8 indicating a crystalline phase other

than sodalite 314-3 XRD pattern for experiment number 11 indicating a crystalline phase

other than sodalite 32


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VIIIList of Figures (continued)

Pages4-4 XRD pattern for experiment number 15 indicating a crystalline phase

other than sodalite 324-5 XRD pattern for experiment number 5, typical of sodalite with little or

no amorphous material 334-6 XRD pattern for experiment number 10, typical of sodalite with little or



no amorphous material 344-9 SEM picture of sodalite from batch 22, 2.7 0.3 um crystallites 364-10 SEM picture of sodalite from batch 6, 2.7 0.2 urn crystallites 364-11 SEM picture of sodalite from batch 30, 6.5 0.1 urn crystallites. Note

that crystallites consist of intergrown crystals rather than agglomeratesof individual crystals 37

4-12 SEM picture of sodalite from batch 13,6.9 1.4 um crystallites 374-13 % RH vs. Time for a blank water removal test (no sodalite) 424-14 % RH vs. Time for sodalite batch 10 water removal test 424-15 % RH vs. Time for sodalite batch 13 water removal test 434-16 Water removal test for sodalite10 at 100 ml/min (2.8 0.4 urn) 44


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IXList of Figures (continued)Pages

4-17 Water removal test for sodalitel0 at 60 ml/min 444-18 Water removal test for sodal itel0 at 20 ml/min 454-19 Water removal test for sodalite13 at 100 ml/min (6.9 1.4IJ.rn) 454-20 Water removal test for sodalite13 at 60 rnl/min 464-21 Water removal test for sodalite13 at 20 ml/min 464-22 Sodalite Regeneration at 110C under dry air flow 484-23 Percent Deviation by Compound for Blanks Run Without Sodalite 494-24 Percent Deviation by Compound for Run with Sodalite batch #10

(2.8 0.4 urn) 504-25 Percent Deviation by Compound for Run with Sodalite batch #13

(6.9 1.4 urn) 51

4-26 Percent Deviation by Compound for Run with Sodalite batch #14(4.9 1.9 urn) 52

4-27 Percent change by compound from Randall Brown experiment(Brown, 2000) 52


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CHAPTER IIntroduction

Due to human activities air pollution levels increased dramatically after theindustrial revolution (Brasseur et aI., 1997). Photochemical smog, global climatechange, toxic air pollutants, acidic deposition, and stratospheric ozone depletion areissues which affect every living creature on this plant. Due to the importance of theseissues, great deal of research and development activity is aimed at understanding andhopefully solving some of these problems. An important step toward understanding thechanges in the atmosphere is to identify and measure the trace gases in the atmosphere.Gas chromatography (GC) is one of the instruments widely used to analyze air samples.Yet, even a small amount of water present in an air sample makes the process ofidentifying and quantifying organic trace gases unreliable. Thus the need to separatewater from other gases in air samples is critical in order to accurately identify thesegases.

Sodium sodalite is a rmcroporous zeolite with pore sizes appropriate for theadsorption of water but inaccessible to organic molecules (Breck, 1974). It should,therefore, be useful for drying air samples prior to identification and quantification oftrace organics contained therein. However, tests of sodium sodalite for this purposedemonstrated that the material did, in fact, adsorb and desorb organics, particularlyaromatics (Brown, 2000). Scanning electron microscopy (Figure 1-1) showedcrystallites with both needle-like and spherical morphology, while x-ray diffractionshowed a pattern indicative of sodalite. It appeared that perhaps needle-like crystals of


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2sodalite had combined to form spherical aggregates with micro- and mesoporosity.The pores in these aggregates might be responsible for the adsorption of organics thatare too large to access the microporous structure of sodalite, It was proposed in thecurrent research that by adjusting synthesis conditions; it might be possible to producecrystals with different morphology that are less likely to form these porous aggregates.

In the course of the current research, the needle-like morphology was notreproduced, and it was determined that the needle-like crystals seen in the prior workwere probably a second phase with larger pores than sodalite. Additionally, withhigher-resolution scanning electron microscope the spherical crystallites were seen to besolid, not aggregates of needles. The current study explores the effect of synthesisconditions on sodali te crystal morphology and the suitability of sodalite for use inremoving water vapor from air samples prior to trace organic analysis.

Figure 1-1 Scanning Electron Micrograph ofCrystallites from Prior -workshowing two distinct morphologies (Brown, 2000).


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31.1 ObjectiveIn this study the effect of different synthesis conditions on sodalite crystallite

size was explored, and sodalite with large and small crystallites was tested for theability to remove water from air samples without disturbing their organic content.

1.2 Atmospheric ChemistryNon-methane hydrocarbons (NMHC) are among the important compounds that

interest researchers. Although natural sources are the major contributors of NMHC,almost all human activites related to energy use or transfer result in the release ofNMHC into the atmosphere (Brasseur et al., 1997).

Combustion is also a source of nitrogen oxides (NO and NOz) in theatmosphere. When these pollutants build up to sufficiently high levels, a chain reactionoccurs from their interaction with sunlight in which the N02 is converted to nitrogenoxide (NO) and oxygen atoms that combine with the O2 in the air to produce ozone (03)(Brasseur et al., 1997).

NOz +hv NO + 0 (3p)o (3p) +o. 0 3

(1-1)(1-2)

In the absence of NMHC's, the ozone concentration is held in balance by subsequentreaction with NO.


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4

While NO x (NO + N02) is necessary for the formation of ozone, hydrocarbons areessential for ozone accumulation. Thus NMHC are important players in the productionof photochemical smog, and their concentration is of interest in understanding andregulating smog formation through the following photochemical oxidation cycle:

RH + OH (+ O2) -7 R02 + H2 0 (1-4)R02 +NO (+ O2) -7 (carbonyls) + N02 + H02 (1-5)

N02 + hv (+ O2) -7 NO + 0 3 (1-6)RH + OR (+ 3 O2) -7 (carbonyls) + 0 3 +H02 + H20 (1-7)

In the presence of NMHC, NO reacts with organic peroxy radicals (R02) instead ofwith 0 3, allowing 0 3 to accumulate.

1.3Water InterferenceOne of the factors that can affect gas chromatographic (GC) measurement of

volatile organic compounds is water vapor (Helmig and Vierling, 1995). Even a smallamount ofwater present in air samples analyzed by GC will cause changes in the signalintensities, retention times, and even can extinguish the flame ionization detector flamewhich will make the use of GC to identify and quantify organic compounds unreliable.Moreover, in GC measurements cryogenic freeze-out is often use for sampleconcentration. Water can accumulate as ice during the concentration step which cancause chemical transformations of organic trace gases in the water/ice matrix (Helmig


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5and Vierling, 1995) or prevent flow of the bllik gases (N2 and O2) not intended to betrapped. Furthermore, for GC that use sub-ambient oven temperature with cryogenicoven programming, ice can cause the capillary column to clog. The minimum wateramounts that would cause such a problem, assuming a spherical geometry of an ice pluginside a capillary column of 0.53, 0.32, and 0.23 mm id are 77.9, 17.1, and 6.4 ug,respectively (Helmig and Vierling, 1995). The amount ofwater vapor in the atmospherefor different temperatures and relative humidity (RH), at standard pressure are shown intable 1-1 (Helmig and Vierling, 1995).

Table 1-1. Water Content (mg) of one-liter air sample atlbarT (OC) 20 (%RH) 40 (%RH) 60 (%RH) 80 (%RH) 100 (%RH)10 1.9 3.8 5.6 7.5 9.420 3.5 6.9 10.4 13.8 17.330 6.1 12.2 18.2 24.3 30.440 10.2 20.5 30.7 41.0 51.2

1.4Water RemovalThere are several techniques used to remove water from air samples prior to

injection of the sample into the GC. There are two major approaches:1. Selectively removing water vapor from the sample flow. These techniques

are, passing the sample flow through a trap containing a drying agent such as K2C 03;use of ion exchange membranes (Nation) in the sample flow for water removal;selectively freezing out water at subzero temperature by passing the sample flow'through a cryogenically cooled freezeout trap; condensation of the bulk water in thesample by flowing the heated sample through a controlled cold reservoir; use of cyclone


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6water management system that expand the concentrated sample flow in a turbulentvortex tube which causes water vapor to condense onto the chamber surface wall;selective desorption of the concentrate by slow and temperature-controlled heating ofthe freezeout trap and flow-regulated transfer of the organic gases (Helmig andVierling, 1995). Although these techniques are successfully used for specificcompounds under well-defined experiments, their use in general is limited because ofthe possible loss of VOC's on the drying agent and the possible introduction ofcontaminants (Helmig and Vierling, 1995).

2. The second approach is to selectively trap VOC's at the sample collectingstage through the use of solid adsorbents. The organic trace gases are trappedselectively in the solid adsorbents without trapping components such as CO2 and water.In practice, various adsorbents have been shown to trap atmospheric moisture to adegree that still cause analytical problems (Ciccioli et. al., 1992)Our intended approach is to use the zeolite sodalite as a drying agent. Its high affinityfor water and low affinity for organics at room temperature should make it possible todry samples without disturbing the organic components. No low temperatures areinvolved which might cause condensation of less-volatile organics. Most sodalitesurface area is inaccessible to the organics, so adsorption of organics is unlikely.Synthetic sodium sodalite contains no organic material that might contaminate thesample. However, following disappointing results with early tests of sodalite for waterremoval, it became important to test the effect of synthesis conditions on sodalitemorphology and performance.


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7CHAPTER I I

LITERATURE REVIEW

2.1 ZeolitesZeolites are rrucroporous crystalline solids with well-defined structures.

Generally they contain silicon, aluminum and oxygen in their framework and cationswith water and/or other molecules within their pores. Many occur naturally as minerals.Others are synthetic, and are made commercially for specific uses (Breck, 1974). Adefining feature of zeolites is that their frameworks are made up of 4-connectednetworks of atoms. Zeolites can be thought of as tetrahedra, with a silicon or aluminumatom in the middle and oxygen atoms at the comers. These tetrahedra can then linktogether by their comers to form many different structures. The framework structuremay contain linked cages, cavities or channels, which are of the right size to allow smallmolecules to enter (Breck, 1974).

Synthetic zeolites have been used successfully in many commercial applications.Changes in silica-to-alumina ratios, unit cell sizes, pore sizes, surface area, cations, andincorporated metals produce different adsorbent and catalytic properties that are usefulin many new application areas (www.zeolyst.com). Zeolites are widely used as catalystsin the refining of crude oil into finished petroleum products. Because of their highselectivity, zeolite catalysts are considered one of the most efficient and cost-effectivemethods for a number of refinery conversions, especially in upgrading refinery streamsinto high-octane gasoline blending stock. In the production of petrochemicals, zeolitesare increasingly replacing environmentally unfriendly catalysts. Zeolite catalysts


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8typically yield fewer impurities, have higher capacity, give greater unit efficiency, andafford higher selectivity. Moreover, unlike the acid catalysts that have been used in thepast, such as solid phosphoric acid and hydrofluoric acid, zeolites are non-hazardous,and non-corrosive. Furthermore, metal-exchanged zeolite catalysts have been employedon vehicles that use the efficient, oxygen-rich, lean-bum diesel engines, which produceless CO2, a greenhouse gas as a less costly and more effective option for NOx removalthan the three-way catalytic converter (www.zeolyst.com). Moreover, zeolites are usedin many industrial processes such as catalytic cracking, hydrocracking, organicchemicals, and inorganic chemicals (Bhatia, 1946).

Some work was done exploring different ways of reducing the particle size ofzeolite A by Smimiotis et al (2001). Several parameters such as temperature, alkalinity,and water content, in addition the effect of using microwaves, centrifuging, andultrasonication were studied. Although the high pressure and temperature created by theultrasonication was expected to affect the nucleation process and lead to smallercrystals, it has been found that ultrasonication did not lead to any change in the crystalsize. Si02/Al2 0 3 ratio did affect the particle size distribution of zeolite A. DecreasingSi02/Al2 0 3 ratio lead to a narrower particle size distribution. Moreover, for samples thatwere subjected to microwave radiation for105 seconds, rapid crystallization along witha narrow particle size distribution were observed (Brar et at, 2001).

2.2 SodaliteSodalite IS one of the naturally occumng zeolites; moreover, it can be

synthesized in the laboratory. The unit cell of the natural sodalite IS


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9Na8[(AI02)6(Si02)6]Cl2. However, during laboratory synthesis of sodalite if NaOH isintercalated the composition varies according to Na6AI6Si6024oxNaOH(8-2x)H20because one NaOH replaces two water molecules (Breck, 1974). The sodalite structuralunit is called the ~ - c a g e which is constructed of repeated truncated octahedron units. A~ - c a g e is made of 8 'hexagons' and 6 'squares ' (Figure 2-1 and Figure 2-2). Breckreported that sodalite will adsorb 18% water by weight and that the void volume ofsodalite is 0.35 cc/cc. Moreover, the kinetic diameter of sodalite pores (


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Figure 2-1 Sodalite (J-cage structure. Vertices present Silicon or Aluminumatoms. Lines represent bridging Oxygen atoms

Figure 2-2 Sodalite p-cages stacked.

10


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11CHAPTER II I

Experimental Methods

3.1 Sodalite SynthesisSodalite was prepared following procedures that were developed by Young

(Young, 1998), and modifications of these procedures as detailed below. The gelcomposition for the original synthesis was as follows:

These molar ratios were obtained by mixing the following reagents:Distilled or ACS reagent waterSodium aluminate (NaAI02xH2 0 , x---2)Sodium silicate (Na2Si03 5H20 )Sodium hydroxide (NaOH)The molar ratio corresponding to the gel composition was:

To prepare 100 g of solution the reagents mass ratio was:


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123.1.1 Sodalite Base Synthesis1. In a polypropylene bottle, dissolve 2.013 grams of sodium aluminate and 10.352

grams of sodium hydroxide in 37.391 grams of distilled water. (All massesmeasured in polypropylene bottle on scale accurate to 0.0001 g).

2. In a second polypropylene bottle, dissolve 2.5036 grams of sodium silicate and10.4149 grams of sodium hydroxide in 37.4422 grams of distilled water.

3. Cool both bottles to 0 "C in ice water bath.4. Pour second solution into the first solution and mix the two solutions together.5. Place the mixed solution in a forced convection oven maintained at 100C for

150 minutes.6. Remove the solution from the oven and place the solution in an ice water bath

until the solution temperature reaches 0 DC.7. Filter the resulting crystals and wash with distilled water until the wash water

reach a pH = 7.08. Dry the resulting crystals overnight in the convection oven set at 100C.

3.2 Analysis Method:A two-level factorial design was used to test the effects of synthesis variations

on the sodalite crystal diameter. Five variables were tested, each at two values,resulting in 32 syntheses (no replicates) (Table 3-1). Through the use of effectestimates, the variables having the greatest influence will be determined, and the bestcombination of the variables tested will be selected.


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13The variables to be tested are:Water quality (Qc): distilled.with a conductivity of approximately 4 J.lSiemen cm' vs.ACS reagent grade with conductivity of2 J.lSiemen em-I.Synthesis temperature rr, 80C vs. 110 CPre-synthesis aging temperature (Ta) : -2C vs. 100CNaOH: -20 wt % vs. +20 wt % (relative to current synthesis)Synthesis time (t.): 100 min vs. 240 min

The data obtained from the two-level factorial design experiments was analyzedbased on contrasts and the estimation of factor effects. Contrasts represent measures ofthe difference in the crystals diameter at high factor level and low factor level (W.P.Gardiner, 1997). For synthesis temperature, for example, the high level was 110C andthe low level was 80C (Table 3-2). The factor effect estimation was calculated fromthe average effect on the crystals diameter when the level of the factor or combinationof levels was changed (W.P. Gardiner, 1997).

Contrast for the water quality, for example, was calculated by adding theaverage crystal diameter from experiments in which distilled water (high level) wasused and subtracting average crystals diameter from experiments in which ACS reagentgrade (low level) was used:

Contrast (Qw) = [(Ex.17+ Ex.18+ .. .+ Ex. 32) - (Ex. 1+ Ex. 2+ .. .+Ex. 16)] (3-4)


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14The two variable interactions, such as water quality (Qw) and synthesis temperature(Ts) contrasts, were calculated as the difference between the average crystal diameterfor the variables tested at the same level and the average crystal diameter fromexperiments in which the variables were tested at opposite levels (W.P. Gardiner, 1997).For example,

Contrast Qw x Ts = QwL TsL + QwH TsH - QwL TsH - QwH TsL (3-5)

Where, Land H refer to 'low level' and 'high level' respectively.For three or more variable interaction, such as the contrast for the interaction of waterquality (Qw), synthesis temperature (Ts) , and synthesis time (ts) , the contrasts wascalculated from the difference in the interaction of two variables at the two levels of thethird (W.P. Gardiner, 1997.)

Contrast Qw x Ts x ts = QwTShigh(ts) - QwTSlow(ts) (3-6)

Effect estimates are generally expressed as: (effect contrast) /(2 k-l), where k is thenumber of variables.

This variable "space" includes the current synthesis, but crystalline product wasnot obtained at some combinations of these values. For reaction batches that did notproduce crystallite, diameter was considered to be zero. For syntheses that resulted inamorphous material or materials other than sodalite the crystallite diameter wasconsidered to be zero. Using this assumption, experiments that did not produce sodalite


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15is treated in the same way as experiments that produced material other than sodaliteor sodalite with impurities. This approach was necessary in order to be able to do thestatistical calculation.

Table 3-1 Sodalite Test MatrixTest # Qw Ts T a NaOH t,1 Distilled 80C -2 C 24.836 100 min2 Distilled 80C -2 C 24.836 240 min3 Distilled 80C -2 C 16.562 100 min4 Distilled 80C -2 C 16.562 240 min5 Distilled 80 C 100 C 24.836 100 min6 Distilled 80 C 100C 24.836 240 min7 Distilled 80C 100 C 16.562 100 min8 Distilled 80C 100C 16.562 240 min9 Distilled 110 C -2C 24.836 100 min10 Distilled 110C -2C 24.836 240 min11 Distilled 110C -2C 16.562 100 min12 Distilled 110 C -2C 16.562 240 min13 Distilled 110 C 100 C 24.836 100 min14 Distilled 110 C 100 C 24.836 240 min15 Distilled 110C 100 C 16.562 100 min16 Distilled 110C 100 C 16.562 240 min17 ACS reagent 80C -2 C 24.836 100 min18 ACS reagent 80C -2 C 24.836 240 min19 ACS reagent 80C -2 C 16.562 100 min20 ACS reagent 80C -2 C 16.562 240 min21 ACS reagent 80C 100C 24.836 100 min22 ACS reagent 80C 100C 24.836 240 min23 ACS reagent 80C 100C 16.562 100 min24 ACS reagent 80C 100C 16.562 240 min25 ACS reagent 110C -2C 24.836 100 min26 ACS reagent 110C -2C 24.836 240 min27 ACS reagent 110 C -2C 16.562 100 min28 ACS reagent 110 C -2C 16.562 240 min29 ACS reagent 110C 100 C 24.836 100 min30 ACS reagent 110 C 100 C 24.836 240 min31 ACS reagent 110C 100 C 16.562 100 min32 ACS reagent 110C 100 C 16.562 240 min


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16Table 3-2. Variables high and low levelsVariable High LowSynthesis Temperature, Ts 110 C 80 CPre-synthesis aging temperature (Ta ) 100 C -2CWater quality (Qw) Distilled ACS reagent gradeNaOH 24.836 grams 16.562 gramsSynthesis time (ts) 100 min 240 min.

3.3 X-Ray DiffractionCrystals were evaluated first by powder X-ray diffraction (XRD) and compared

to powder XRD pattern of sodalite found in literature Figure 3-1 (Felsche, 1986) toensure that the material produced by the synthesis was sodalite.

,

r I , 1 ,

100.0

80.0

.et,) 60.0.)

.sQ.)'E 40.0G)

20.0

0.0 0.0 10.0 20.026 angle

30.0 40.0 50.0

Figure 3-1 Simulated XRD powder pattern of sodalite.

In X-ray diffraction, electromagnetic radiation ofwavelength close to 1 A (10-10m), which is about the same size as an atom, is used to probe crystalline structure at the


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17atomic level. X-ray diffraction is used for the characterization of crystalline materialsand the determination of their structure. The interaction of the scattered X-rays createsconstructive and destructive interferences depending on the wavelengths and distancebetween the scatterers of the radiation. (Jenkins & Snyder 1996)Every crystalline solid has its unique characteristic X-ray powder pattern. That pattern

may be used as a "fingerprint" for identification. We can determine the size and theshape of the unit cell for any crystalline compound using the diffraction of x-rays.(http://imr.chern.binghamton.edu/labs/xray/xray.html)The Bragg equation is used to describe the constructive interference (Figure 3-2).Bragg equation:

n x wavelength = 2dsin(theta) (3-8)Where,n: is an integerwavelength: is the X-ray wavelengthd: is distance between the planes in the crystaltheta: is the X-ray beam angle

e

x x

e

Figure. 3-2 Reflection of x-rays from two planes of atoms in a solid.


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18The powders produced by all the successful experiments were analyzed usingthe Rigaku Geigerflex diffractometer provided by the Department of Physics at OhioUniversity, Out of the 27 experiments that produced crystals, 14 gave satisfactory XRDresults that were similar to the sodalite crystal XRD found in the literature (Figure 3-1).

3.4 Scanning Electron MicroscopyFor the samples that gave satisfactory XRD results, scannmg electron

microscopy (SEM) was performed to determine the morphology of the crystallites andto estimate the shape and size of the sodalite crystallites formed.

Conventional light microscopes create a magnified image by using a series ofglass lenses to bend light waves. On the other hand, the Scanning Electron Microscope,Figure 3-3, uses electrons rather than light waves to create the magnified images. TheSEM gives very detailed 3-dimensional images at much higher magnifications than ispossible with a light microscope. The SEM images are in rendered black and white.Because SEM illuminates the sample with electrons, the samples also have to be madeto conduct electricity; therefore, SEM samples have to be coated with a thin layer ofgold by a sputter coater machine. The sample is placed inside the vacuum column in themicroscope. After the air is pumped out of the column, an electron gun emits a beam ofhigh-energy electrons. This beam travels downward through a series ofmagnetic lensesdesigned to focus the electrons to a very fine spot. Scanning coils near the bottom movethe focused beam back and forth row by row across the specimen. When the electronbeam hits a spot on the sample, secondary electrons are knocked loose from its surface.These electrons are counted via a detector which than sends the signals to an amplifier.


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19The image is constructed from the number of electrons released from each spot on thesample. (http://www.mos.org/sln/SEM/works.html)

Figure 3-3 Scanning electron microscope diagram.

Scanning electron microscopy pictures were taken using ZEISS DSM962scanning electron microscope in the Scientific Imaging Facil ity at Ohio University.

Sodali te samples were prepared for SEM analysis by dispersing a small amount of thesample on a special sample holder, followed by gold sputter ing at 15 J.lA for 90 s. Allsamples were analyzed using an accelerating voltage ranging from 20 to 30 KVo


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203.5 Water Removal ExperimentThe ability of sodalite to remove water vapor from air samples was tested using

an apparatus designed by Randall Brown (Brown, 2000) (Figure 3-4). This systemdelivered saturated humid air or dry air to the Omega RH-411 humidity sensor eitherdirectly or after passing it through a 1/4 -inch nominal diameter stainless steel tubing 31/8 inch long cartridge containing a sample of sodalite that was held in place with veryfine stainless steel screens mounted in reducing unions on both ends. For humiditylevels above 90% R.H. and below 10% R. H. the accuracy of the sensor is within 5%,otherwise the error is only 2%.

FilterHumidity Sensor

I I

SupplyValve

Humidifier

Dry AirSupplyFigure 3-4 Water removal apparatus

SodaliteCartridge


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21A total of six blank runs bypassing the sodalite cartridge were made with flowrates of 20, 60, and 100 mL/min. For each flow rate, dry air was passed through thesystem and at time zero the supply valve was turned to deliver humid air to the system(Figure 3-5). The humidity sensor readings were recorded in one-minute intervals.

FilterHurnidity 5 e n ~ o r

I I

SUPDLYValve

Humidifier

Dry Air Suppl.Y

SodaliteC a r l r i d ~ e

Figure 3-5 Water removal apparatus: humid air supply, bypassing sodalite

Two experiments were conducted usmg cartridges filled with 505.6 mg ofsodalite crystals from batch number 10 (sodalite with small crystal size) and with 578.2mg of sodalite from batch number 13 (sodalite with large crystal size). In eachexperiment dry air was passed through the sodali te cartridge by adjusting the sensor


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22valve and at time zero the supply valve was turned to deliver humid air to the system(Figure 3-6). The experiment was repeated using airflow rate of 20, 60, and 100mL/min for each sodalite batch. Sodalite was regenerated after each run for re-use.Experiment, in which sodalite from batch number 13 was tested, was repeated again andthe results from the two experiments were in excellent agreement.

FilterHurnidit)J Sen*or

I I

Suppl.....ValveHumidifier

Dry Air Suppl,Y

SodaliteCartridge

Figure 3-6 Water removal apparatus: humid air supply, through sodalite

3.6 Regeneration of SodaliteFor sodalite to be practically used as a desiccant it needs to be capable of being

regenerated quickly and easily. After each experiment in which sodalite was tested forwater adsorption the cartridge containing the "wet" sodalite was heated to 110C usingan electrical resistance heater wrapped around the cartridge. A thermocouple was used


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23to monitor the temperature. When the temperature reached 110C, within less than aminute, the supply valve was switched from humid air to dry air (Figure 3-7). Thehumidity sensor reading was then recorded every minute until the sensor reading wasback to the dry air humidity level which was around 8 % relative humidity.

FilterHumidity Sen*orI I

SupplyValveHumidifier

DryAir Suppl}l

SodaliteCartridge

Figure 3-7 Water removal apparatus: dry air supply, through sodalite

3.7 Sodalite Non-Interference with NMHCIn order for sodalite to be adequate for use as a desiccant In atmospheric

researchit must not adsorb any of the trace organic gases present in air.Sodalite was tested for the ability to remove water from the air sample without

disturbing the organic content; this was done by analyzing a known standard sampleusing the gas chromatograph (GC) (Figure 3-8) with sodalite and then without sodaliteand comparing the output of the GC in both cases. The standard gas mixture used was


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24an SOS standard (Eric Apel, NCAR) containing 26-hydrocarbon compounds with molefractions ranging from 0.64 to 2.29 ppb (Table 3-3). The analytical system is suitableonly for compounds having seven or fewer carbons, so all 26 NMHC are not quantified.

Table 3-3 SOS Standard Gas Composition~ o m p o u n d IConcentration Retention Time(Minutes)ppbv)ETHANE 2.26 2.21ETHYLENE 2.18 2.19PROPANE 2.29 2.28PROPYLENE 2.11 2.11ACETYLENE 0.64 0.64ISOBUTANE 1.84 1.84rN-BUTANE 2.28 2.28TRANS-2-BUTENE 1.96 1.97I-BUTENE 2.19 2.20CIS-2-BUTENE 1.79 1.80ISOPENTANE 2.18 2.18rN-PENTANE 2.11 2.111,3-BUTADIENE 1.73 1.74TRANS-2-PENTENE 2.00 2.00CIS-2-PENTENE 2.03 2.05ISOPRENE 1.89 1.90BENZENE 2.15 2.12TOLUENE 2.15 2.31

GasChromatograph

I OUTPUT I

Figure 3-8 Organic non-interference test system


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25

Through all the experiments, a pressure difference system was used to controlthe volume of standard loaded. The standard passed through a cryogenic trap due to thepressure difference between the standard mixture and an evacuated three- liters canister.The volume of sample loaded was proportional to the pressure difference in theevacuated canister before and after sample loading. The pressure was measured using apressure transducer (MKS Baratron). Five runs were performed without sodalite plusnine runs with sodalite from batch numbers 10, 13, and 14, each tested three times.

For all the runs, the standard was drawn through a pre-concentration systemconsisting of two stainless steel tube loops. The first loop is the cryo-trap and thesecond smaller loop is the cryo-focuser. Both loops were cooled to -180C using liquidargon. The function of the concentration system is to concentrate the organic sample toa small enough volume to be injected into the capillary column. The standard sample isre-vaporized and injected to the column when the cryo-focuser trap is heated withboiling water at 100C.

Inside the GC column the different hydrocarbons are separated by thedifferences in the interaction between the hydrocarbons and the stationary phase of thecapillary column. The column used in this research was a 50m x 0.32mm x SumAl20 3IKCI porous layer open tubular (PLOT) capillary column installed in a HewlettPackard 589011 gas chromatography oven equipped with flame ionization detection(GCIFID). This type of column is designed to separate light hydrocarbons (sevencarbons or fewer).


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26The helium earner gas and the temperature profile were programmed toachieve the optimum separation and resolution. The head pressure was adjusted duringthe run to maintain a constant flow rate of 6.0 mL/min. The following was thetemperature program that was used:

35C, hold 1 minuteRamp 20 C/min to 100CRamp 12C/min to 150CRamp 20C/min to 200, hold 15 minutes

The sample loading, preconcentration, and analysis steps followed one immediatelyafter the other. An SOS standard chromatogram output is presented in figure 3-9.

20

; i :

! '}. I ll.

Figure 3-9 SOS Standard chromatogram output


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27CHAPTER IV

RESULTS AND DISCUSSION

In this research the effects of different synthesis conditions on sodalitecrystallite morphology was investigated using x-ray diffraction and scanning electronmicroscopy. Sodalite with large crystallite diameter and sodalite with the smallcrystallite diameter were tested for their ability to remove water vapor from air samples.Moreover, the regeneration conditions for sodalite were examined. Finally, thepossibility of interaction between sodalite and organic compounds was investigated.

4.1 Synthesis ResultsThe goal of this part was to determine the synthesis conditions that produced

sodalite. Out of the total 32 experiments performed, batches numbered 1, 3, 19, 23, and29 did not produce any type of precipitation at the end of the experiment time.Moreover, 13 experiments out of the remaining 27 experiments did not give an x-raydiffraction pattern typical of sodalite (Table 4-1).

4.1.1 X-Ray Diffraction ResultsThe x-ray diffraction pattern of powders obtained from experiments 4, 7, 8, 11,

12, 15, 16, 17, 24, 27, 28, 31, and 32 (Figure 4-1 to Figure 4-4 for example) did notresemble the x-ray diffraction pattern for sodalite found in the literature (Figure 3-1).On the other hand; experiments 2,5,6,9, 10, 13, 14, 18,20,22,25,26,30 (Figure 4-5to Figure 4-8 for example) gave x-ray diffraction pattern were typical of sodalite.


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Table 4-1 XRD Results for the 32 experiments 28Test # Qw Ts Ta NaOH ts x-ray result

1 Distilled 80 C -2C 24.836 100 min ~ crystals2 lDistilled 80 C -2C 24.836 240 min Success3 lDistilled 80 C -2C 16.562 100 min ~ crystals4 Distilled 80 C -2C 16.562 240 min Failure5 Distilled 80 C 100 C 24.836 100 min Success6 Distilled 80 C 100 C 24.836 240 min Success7 lDistilled 80C 100 C 16.562 100 min Failure8 Distilled 80 C 100 C 16.562 240 min [Failure9 Distilled 110C -2C 24.836 100 min Success10 Distilled 110C -2C 24.836 240 min Success11 Distilled 110C -2C 16.562 100 min Failure12 Distilled 110C -2C 16.562 240 min Failure13 Distilled 110 C 100 C 24.836 100 min Success14 Distilled 110C 100 C 24.836 240 min Success15 Distilled 110C 100 C 16.562 100 min Failure16 Distilled 110C 100 C 16.562 240 min tFailure17 ACS reagent 80 C -2C 24.836 100 min Failure18 ACS reagent 80 C -2C 24.836 240 min Success19 ACS reagent 80C -2 C 16.562 100 min No crystals20 ACS reagent 80C -2 C 16.562 240 min Success21 ACS reagent 80C 100 C 24.836 100 min Success22 ACS reagent 80 C 100 C 24.836 240 min Success23 ACS reagent 80C 100 C 16.562 100 min lNo crystals24 ACS reagent 80 C 100 C 16.562 240 min Wailure25 ACS reagent 110C -2C 24.836 100 min Success26 ACS reagent 110C -2C 24.836 240 min Success27 ACS reagent 110C -2C 16.562 100 min Failure28 lACS reagent 110 C -2C 16.562 240 min Failure29 ACS reagent 110C 100 C 24.836 100 min ~ crystals30 ACS reagent 110C 100 C 24.836 240 min Success31 ACS reagent 110C 100 C 16.562 100 min Failure32 ACS reagent 110C 100 C 16.562 240 min Failure


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r~ ! - - _ . __ .~

ZQ1849.RAW... ~ _ _ ...._.L._ # ._ SODEX7 -_._._ _._._ _JIIijjI!iI

29

10 . 15 . 20 . 25 . 30. 35 . 40. .45. 50

Figure 4-1 XRD pattern for experiment number 7 indicating significantamorphous material anda crystalline phase other than sodalite

Z01850.RAW~ ~ ~ = = ~ S ~ - ~ ~ = = l!III

10. i5 20. 25. 30. 35. 40. 45. 50"

Figure 4-2 XRD pattern for experiment number 8 indicating a crystalline phaseotherthan sodalite


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30zo :853. RA'fi

50.5.5.0.

... 50"0-EX11--------,------ I......__ __ . _....... ...... _.._ _ __ h._ .... .........-.._ _._._... .._..._.._. _ _

!iiI

25.0.5.0.

Figure 4-3 XRD pattern for experiment number 11 indicating a crystalline phase otherthan sodalite

10. 15. 20. 25. 30. 35. 40. 45. 50.

Figure 4-4 XRD pattern for experiment number 15 indicating a crystalline phase otherthan sodalite


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31ZO .1841. R,,\W.... -..~ ~ . , , - .._ ..--- _ _ ~ . - ...--._-_._ _-. _ _ - . - - - - - - ~ _ .. _ ~ _.- _- - - "" .SODEX5

10. 15. 20. 25. 30. 35. 40. 45. 50.

Figure 4-5 XRD pattern for experiment number 5, typicalof sodalite with little or noamorphous material

------------------,!..-----..--..-.-..- -------JII

iZD1852.RAW.._ __-_ _ _ _-_ _--_ _ - - - - - _ . _ - ~ _ ..~ . .._._ SODEA10("I") - j - _ "---

~ i

II

!iiil ~ ' , ... , - ~ .....-

~ T ' F r T . , . T ' T ' . , . . , . r T " T , . " ! ~ r , . , ~ T r r T I - " ~ T ' r ' T T ' T ' " T { ~ T r 'TT' , ' , ' I , ' ; ~ ' ~ ~ ~ ' ; ~10. 15. 20. 25. 30. 35. 40 . 45. 50.

Figure4-6 XRD pattern for experiment number 10, typicalof sodalite 'with little or noamorphous material


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32

!1iI

~ : : ~ r r T ~ - ~ ' ~ ' ~ : ' ~ ' ~ ; ' ~ ' ; - : T T T i i ' I i i i f r p r P l ~ ~ l T P " r ' ~ l ~ ; ; ; ' : ~ ~ 110. 15. 20. 25. 30. 35. 40. 45. 50.

Figure 4-7 XRD pattern for experiment number 18, typical of sodalite with little or noamorphous material

1-----o r- - " ' ~ " - - - T -r..o:""2":

j

Ir ~ : ~ : r r r i i i I i ' ' I i i i ' i PT 'TT / " .T ' , ' I ' I' I I" "1 ' T ' T ' r ' T ' T T T T T ' T T ~ ~ ' : ; ' : ~ ~

10. 15. 20. 25. 30. 35. ~ O 45. 50.

Figure 4-8 XRD pattern for experiment number 25, typical of sodalite with little or noamorphous material


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33

4.1.2 Scanning Electron Microscopy ResultsScanning electron microscope pictures were taken of sodalite produced by the

fourteen experiments that gave successful XRD results (Figure 4-9 and Figure 4-10 forexample). The high-resolution scanning electron microscope revealed solid sphericalcrystallites (Figure 4-11 and Figure 4-12). No needle-like crystals were observedo Theaverage spherical crystallite diameter varied from 1.9 to 6.9 urn (Table 4-2).

Table 4-2 Sodalite spherical crystallite diameterExperiment # Crystals Diameter (urn)"

2 2.8 0.75 1.9 0.26 2.7 0.29 2.8 0.410 2.8 0.413 6.9 1.414 4.9 1.918 3.2 0.820 2.5 0.421 3.3 0.422 2.7 0.325 3.2 0.426 3.8 1.230 6.5 0.1

(* Mean 18 often crystallites from each experiment)


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Figure 4-9 SEM picture of sodalite from batch 22, 2.7 0.3 gm crystallites

Figure 4-10 SEM pictllre of sodalite from batch 6, 2.7 0.2 J.lrn crystallites

34


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35

Figure 4-11 SEM picture of sodalite from batch 30, 6.5 0.1 }.lm crystallites.Note that crystallites consist of intergrown crystals rather than agglomerates ofindividual crystals

Figure 4-12 SEM picture of sodalite from batch 13,6.9 1.4 Jlffi crystallites


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364.2 Variables Effect EstimationA two-level factorial design was used to test the effects of synthesis variations

on the sodalite crystallite diameter. The factorial design calculation was carried-outusing the Minitab software. The variables and the sodalite crystallite diameter for eachexperiment were input to Minitab (Table 4-3). The effect estimates for the importantvariables were calculated to be:

Table 4-3 Variable effect estimatesVariable Effect EstimatesQw -0.0231Ts 0.7294Ta 0.4856NaOH 2.8019ts 0.8681Ts*NaOH 1.0419

The effect estimate for water quality is a small negative number. This means thatwater quality is not a major variable that affects the size of the crystals. Larger crystalswere produced when the "low level" ACS water was used, and smaller crystals wereproduced when the "high level" distilled water was used.

The effect estimate for synthesis temperature is a relatively large positivenumber, so large crystals were produced using "high level" 110C, and small or nocrystals were produced using "low level" 80C.


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37The effect estimate for aging temperature is a small positive number, so largecrystals were produced using the "high level" 100C, and small or no crystals wereproduced using the "low level" -2 C.

The effect estimate for NaOH is a relatively very large positive number, so largecrystals were produced using "high level" +20 %wt NaOH. Small or no crystals wereproduced using "low level" -20 %wt NaOH.

The effect estimate for synthesis time is a large positive number, so longersynthesis time gave large crystals and small or no crystals were produced when shortsynthesis time was applied.

The effect estimate for the two way interaction between NaOH and synthesistemperature is a large positive numbers. It is clear that large crystals were producedwhen the NaOH level was same as the synthesis temperature this is achieved by settingboth NaOH and synthesis temperature levels to "high level". Other two way and threeway interaction effect estimates had relatively small value or could not be calculateddue to insufficient successful experiment. It should be noted that due to the largenumber of unsuccessful syntheses (18), all ofwhich were assigned crystallite diametersof zero, the actual value of the effect estimates are somewhat uncertain. However, theirsigns and relative magnitudes may be relied upon.


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Table 4-4Factorial designanalyses inputmatrix38

Qw (JlS/cm) TsoC TaoC NaOH(wt%) ts (min) Crystal Dia. (urn)4 80 -2 24.836 100 0.04 80 -2 24.836 240 2.84 80 -2 16.562 100 0.04 80 -2 16.562 240 0.04 80 100 24.836 100 1.94 80 100 24.836 240 2.74 80 100 16.562 100 0.04 80 100 16.562 240 0.04 110 -2 24.836 100 2.84 110 -2 24.836 240 2.84 110 -2 16.562 100 0.04 110 -2 16.562 240 0.04 110 100 24.836 100 6.94 110 100 24.836 240 4.94 110 100 16.562 100 0.04 110 100 16.562 240 0.02 80 -2 24.836 100 0.02 80 -2 24.836 240 3.22 80 -2 16.562 100 0.02 80 -2 16.562 240 2.52 80 100 24.836 100 3.32 80 100 24.836 240 2.72 80 100 16.562 100 0.02 80 100 16.562 240 0.02 110 -2 24.836 100 3.22 110 -2 24.836 240 3.82 110 -2 16.562 100 0.02 110 -2 16.562 240 0.02 110 100 24.836 100 0.02 110 100 24.836 240 6.52 110 100 16.562 100 0.02 110 100 16.562 240 0.0


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394.3 Water Removal ResultIn these experiments sodalite crystallite with small diameter from batch number

10 and crystallites with large diameter from batch number 13 were tested for theirability to adsorb water vapor from humid air using the apparatus described in section3.4.

Each sodalite batch was tested with humid air at flow rates of 20, 60, and 100mL/min. Blank runs with the same flow rates were carried out at the same time tocompare them to the sodalite runs. All experiments were carried out at lab temperaturewhich varied from 23C to 24 C and at atmospheric pressure. Figure 4-13 shows 45minute blank runs made at flow rates of 20, 60, and 100 mL/min. Figure 4-14 shows thesame experiment using 505.6 mg of sodalite from batch number 10 and Figure 4-15shows the same experiment using 578.2 mg sodalite from batch number 13. Water wasclearly adsorbed by sodalite, moreover; sodalite with the smallest diameter from batchnumber 10 exhibited stronger adsorption for water vapor than the larger diametersodalite.

1 0 0 ~ - - - - - -

30 ~ - - - - - _ .._ - ..

20 -H------------ ..

10 15Time (min)

20 25 30

Figure 4-13 % RH vs. Time for a blank water removal test (no sodalite)


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4060

50

40 r - - - - - - - - - - - - - -F - - - - - - - - - ,== - - -= - - - - - - - - - - - - - - - --

20 t-----< -------+------

10

5050505Time (rrin)

2050o ~ - - _ _ _ r _ - - - _ r _ _ - - _ _ _ r _ - - - ~ - - _ . , . . . _ - - - . . - - - - - - _ _ , _ _ - - _ _ _ _ _ , - - - . . . . , _ - - _ _ _ _ 4o

Figure 4-14 %RH vs. Time for sodalite batch 10 water removal test

70-r-------------------------------------.

40 + - - j J - - - - - , . . . I r - - ~ - - - - - - - - - - - - - - - - - - - ..--::2J:. ';

30 + - + - - ~ - + - -

20

10

----r-+-100mVmin II 60mVmin I1--...- 20mVmin j

5050505Time (rrin)

2050a + - - - - - - r - - - - , . - - - - - - . - - - - - r - - - - - - - - . - - - - - - - - r - - - . . . . . . - - - - - - - , . . - - - . . . . , . - - - - ~o

Figure 4-15 % RH vs. Time for sodalite batch 13 water removal test


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41

Figure 4-16 to Figure 4-21 show the concentration of water per volume of airverses total airflow for blank and sodalite runs at the same flow rates. The amount ofwater adsorbed was calculated by integrating the area between the blank run curve andthe sodalite run curve. Sodalite produced by both batches adsorbed higher percentage ofwater at lower flow rate. Sodalite with an average crystallite diameter of 2.8 urnproduced by batch number 10 adsorbed about 73% of the water vapor in 900 mL 86%humid air. Sodalite with an average crystallite diameter of 6.9 urn adsorbed 41.5% ofthe water vapor in 900 mL 86% humid air (Table 4-4 and Table 4-5).

0.02 -- ...-.---...----------------------.-.-------.----- -- ,0.018

0.016'-

0.014oE-; 0.012j

0.01 -..e0.008eccug 0_006oo0.004

0.002

-------=.I ItIIt ~ . . _ J F I F . : = : ; . : : . : . : ; ; ; ; : ; ; = - ~ - - - - - - - - -

i - -+ --Water cone. Blank (mgJml)! Water cone. Sodalite (mg/ml)---L __ ._____ _

5000500000500000500Total Airflow (ml)

200050000000o I-----,..-----r-----r-----r-----r-----r-------..,-----r-------!o

Figure 4-16 Water removal test for sodalitelO at 100 ml/min (2.8 0.4 gm)


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42

0.018

0.016

. - - - : : . . . - . . . : : . . . . . . - = - - - . : . . . - . : . . . . . ~ - - ' - - : - - . . : . . _ ~ - - ' - - - - - - - - - - _ . _ - - - _ . __._.-

.; 0.014oE 0.012j'0CI 0.01..co 0.008CGQg 0.006o

.--.--,__.....-:8....-------------------.------------___ . { Waterconc.Blank(mglml) L _ __Water cone. Sodalite (mglml) i

0.004

0.002

3000500000500Total Air f low (rri)

100000O ~ - - - - - - . . , - - - - - - - . . . . , . . - - - - - - - - - - . , , - - - - - - - - - r - - - - - - - _ - - - - - - - lo

Figure 4-17 Water removal test for sodalitelO at 60 ml/min

0.02 ------------ ._--_._---------------------_._-----_._---_.-----------0.018

0.016 +---- ..- - . - - ~ ~ .

j100000000000 500 600Total "' r flow (01)

300

...-------_._--- - - - - - - - - - _ . _ - - - - - - - - - ,_._,- , --------------------==-=---_.._ - - - - , = - ~ - - - - - ~ ~

20000O-l-.-.- - - - - - - - . . . - - - - - - . . , . . . - - - - . . . . . . . . - - - - . . . . . . . . - - - - - . - - - - - _ - - - _ - - ~o

0.002 ~ - - - .-,,-.------ - -

0.004

0.014 ~ - - ~ - - - - - - - - -E 0_012 -joCI 0.01..co

0.008eGQC


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43

:-+ - Water conc. Blank (mg/ml) :, L- _! - Water conc. Sodalite (mg/ml) I

0.02 -0.018-..co 0.016

I+-0E 0.014i::Q) 0.012uI+-0 0.01Jge 0.0080;;eu... 0.006eQ)(Je 0.0040(J0.002

00 500 1000 1500 2000 2500 3000 3500 4000 4500 5000

Total air f low (ml)Figure 4-19 Water removal test for sodalite13 at 100 ml/min (6.9 1.4 Jlm)

0.02 ~ - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - .0.018 . { - - - - - - - - - : : ; A ; ; ~ .. . .. . .. .~ . . . . . . . .~ . _ 4 I ~ . _ 4 I ~ __ - - - - - _ _ e ~ .-..----..-..0.016 -i----,.,JC--'


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440.02 ....,..----------------------------'--------,

0.016 + - - - - - - - ~ ~ : - - - -

0.018

0.002

0.004 .fJ------+---.-------

0.014...oE 0.012III

0.01..eo! 0.008C..c,)s 0.006o

1000000000000000000000O-t---..,..----....,..---.....,-----r---------.,...----r------,..--_------!o

Total Air flow (ml)

Figure 4-21 Water removal test for sodalite13 at 20 ml/min

Table 4-5 Percentage ofwater adsorbed by sodalite from batch numberlOIFIOW rate (mUmin)lfrotal feed water (mg) IIRemovedwater (mg) IIPercentageWater removed I100 79 2 39 1 49260 48 1 28 1 58 220 15 1 12 1 73 3

Table 4-6 Percentage ofwater adsorbed by sodalite from batch number 13IFlow rate (mUmin)lfrotal feed water (mg) IIRemovedwater (mg) IIPercentage Water removed I100 79 2 21 1 26 1.60 47 1 18 1 37220 15 1 61 42 2


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454.4 Sodalite Regeneration ResultAt the end of each experiment in which sodalite was tested for water adsorption,

the cartridge containing "wet" sodalite was heated to 110C with an electricalresistance heater wrapped around the cartridge. A thermocouple was used to monitorthe temperature. When the temperature reached 110C, usually within less than oneminute, the supply valve switched from humid air to dry air. The humidity sensorreading was recorded every minute until the relative humidity reaches the value of dryair which was around 8 percent (Figure 4-22). Sodalite can easily be regenerated duringthe 30-45 minutes typically required to complete GC analysis of an air sample.

908070

c 60 + ~ - - - - - - . _ - - - - - - - - - + - - - - - + - - - ~ - - - - ~ - - - - ~ - - - - - - _ . ~ ~ - - . _ - - _ . - ~ - - + - - - ----- - - ~ - - - - - - . - - - . - - - . - - - ~ - . - - - - I=s. 50J:Q)> 40a;a::

30

10

oo 2 4 6 8

Time (min)10 12 14 16

Figure 4-22 Sodalite Regeneration at 110C under dry air flow


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464.5 Non-Interference with NMHC ResultsIn this part of the research the ability of sodalite to be used as desiccant for GC

analyses without interference with the organic compounds found in air samples wastested. A known 80S standard was analyzed by gas chromatography either after thesample passed through a sodalite cartridge or without passing through sodalite asdescribed in section 3.6.

To test the reproducibility and reliability of the pre-concentration and gaschromatography systems five standard sample run were performed without the use ofsodalite. Every compound is compared to average value of the runs in Figure 4-23.Except for toluene,most of the results were within 5% of the average value. Thesystem is clearly quite reproducible overall.

Sodalite did not interfere with any of the organic compounds present in the SOSstandard. Although sodalite with large, medium, and small crystallites did not show anysystematic adsorption of organic compounds, smaller crystallites gave the lowerdeviation from the blank run average value (Figure 4-24, Figure 4-25, and Figure 4-26)0

Previous work in our laboratory (unpublished) has established that the majorsource of uncertainty in the analytical system is in the measurement of the samplevolume loaded. Loading a slightly larger volume in a particular run results in highermeasured concentrations for all compounds. Also, response factors for acetylene areknown from our prior work to show more day-to-day variability than for othercompounds. Finally, our analytical system regularly shows poor reproducibili ty fortoluene and heavier compounds.


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47

40.00% - t - - - - - - - - - - - - - - - - - - - - - - - - - -

30.00%

20.00% +-----------------------

& 10.00% - t ~ _ . - - - - - - - - - - - - - - - - - - - - .----j 0.00% ~ ~ T ~ ~ ~ ~ ~ ~ ~ ~~ 1 0 . 0 0 % t------------ ---.--------.---

~ 2 0 . o o % J-----------.--_. - -- -- - - - -

~ 3 0 . 0 0 % +-------------------- . ---.--

-ao.oos

~ 5 0 . o o % !--.__

.Run#1!

: : ~ ~ : [ = - ~ ~ ~ ~ - = = -.Run#4 i--- ..-.--.----.. -.. .. _. . ____tcRun#51_----- _. I

1. _J

Figure 4-23 Percent Deviation by Compound for Blanks Run Without Sodalite

Three runs were performed using 514.7 mg, 578.2 mg, and 534.7 mg of sodalitefrom batches number 10, 13, and 14 respectively. In each run about 200 torrs of 80Sstandard was passed through the sodalite. The first run for each batch was done withconditioned sodalite while the second and third runs were done without reconditioningthe sodalite. The average of the three runs for each sodalite batch was compared to theaverage value of the blank runs Figure 4-24 to Figure 4-26. Although all the samplesgave excellent result, it seems that sodalite with smaller crystals gave the lowestdeviation from the blank runs average (Table 4-6).If sodalite does interfere with with organics, the analysis should show greater deviationfor same compounds, because some will be preferentially adsorbed. An example of suchpreferential adsorption from Randall Brown (Brown, 2000) is shown in Figure 4-27.


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50.00% ,.__ ._._._.. .._._.__ __ __ _ __ __._ - _ _ __._-_.._.- - - - - ..- - - -- -. - -.,

40.00% . ~ - - - .._--- - ... .-._-- .._-..---.. "'--'''--'-'''''-'

30.00% }----..-.--.----.----------.- -.- .."---- ._.

20.00% 4-----------.----.- -------- - -.

CD 10.00%atcIII0.00% + - - . . ~ ~ ~ . . . . ~ _ . r . ~ ~ - . . , ..."1{..."..,..rn......1'"I._JL.-m4....~ - - f l , . - - - . .........- . J ~ . . . . - r - I ~ ~ ~ ~ . . . . . . . . - , . . I i " ' - - ~ - ~

CDe:. -10.00%

48

-20.00%

-30.00%

-40.00%

ImRun#1 } - - - - .Run#2 ImRun# 3 ~ - - - ~.Run#4

-50.00% -"-- .__---'

Figure 4-24 Percent Deviation by Compound for Run with Sodalite batch #10(2.8O.4J.!m)

50.00%

40.00%

30.00%

20.00%

CD 10.00%atcIII..c(J 0.00%CCDecD -10.00%.-20.00%

-30.00%

-40.00%

-50.00%

-r -- - - - - - - - - - - - . - - - - --.-.- --- ----------- - - - - -,

I_Run# 1 ,----- -- --- - - - - ~ ----- .. -- - -IDRun#2 Il ~ ~ ------- - - - - - - - - - - - - -- - -

._ ..._ . . . ._ . .. __ ~ _ ____J

Figure 4-25 Percent Deviation by Compound for Run with Sodalite batch #13(6.9 1.4 J.!m)


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49

40.00%

30.00%

20.00% - - - - - -

10.00% .J0.00% - t - - . . . . , . . . . . - - ~ ~ ....~ i , . . - _ .. ..,i--.....,..--r---;-. . . ' ..-.r'r'-....,--10.00%

-20 .00% --- -- -

-30.00%

-40.00%

- ---I_Run # ~ - - _------J IIRun # 2I_Run# 3

-50.00% J..-

Figure 4-26 Percent Deviation by Compound for Run with Sodalite batch #14(4.9 1.9 J,lm)

100.000/080.001

60.000/040.00%

CDC)e 20.001eu..c:U 0.00%..eCD(J -20.00%-CDQ. -40.00% -

-60.00%-80.000/0

-100.000/0

m1stRun.2nd Run

Run

Figure 4-27 Percent change by compound from Randall Brown experiment (Brown,2000)


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Table 4-6 Results from blank and sodalite runs50

Compound Blank (ppbv)* Batch # 10** Batch # 13** Batch # 14**ETHANE 2.26 0.11 2.19 0.06 2.38 0.20 2.20 0.05ETHYLENE 2.180.11 2.180.04 2.34 0.15 2.20 0.00PROPANE 2.29 0.09 2.27 0.05 2.39 0.12 2.25 0.04PROPYLENE 2.11 0.10 2.11 0.04 2.26 0.12 2.08 0.03ACETYLENE 0.64 0.04 0.65 0.02 0.62 0.03 0.65 0.02I-BUTANE 1.84 0.08 1.84 0.04 1.950.10 1.81 0.04N-BUTANE 2.28 0.09 2.28 0.04 2.43 0.15 2.24 0.05T-2-BUTENE 1.96 0.09 1.96 0.04 2.100.11 1.93 0.03I-BUTENE 2.19 0.11 2.19 0.05 2.34 0.12 2.16 0.04C-2-BUTENE 1.79 0.08 1.79 0.04 1.910.10 1.76 0.03ISOPENTANE 2.18 0.08 2.18 0.04 2.30 0.12 2.15 0.06N-PENTANE 2.11 0.09 2.10 0.04 2.24 0.12 2.08 0.051,3-BUTADIENE 1.73 0.07 1.74 0.03 1.85 0.09 1.70 0.03T-2-PENTENE 2.00 0.09 2.00 0.04 2.130.I1 1.96 0.04C-2-PENTENE 2.03 0.08 2.04 0.04 2.170.11 2.00 0.04ISOPRENE 1.89 0.08 1.89 0.04 2.020.IO 1.86 0.04BENZENE 2.15 0.09 2.12 0.04 2.270.13 2.08 0.05TOLUENE 2.17 0.23 2.34 0.18 2.52 0.26 2.31 0.12*Mean 18 of 5 runs**Mean 18 of3 runs


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51CHAPTER V

CONCLUSIONS AND RECOMMENDATIONS

The synthesis variables that most strongly affected the crystallite size wereidentified. Synthesis temperature, sodium hydroxide amount, synthesis time, and thetwo way interaction between synthesis temperature and sodium hydroxide amount werefound to be the major variables affecting sodalite formation and morphology. Of these,sodium hydroxide amount and synthesis temperature were most important. Waterquality was found to have no effect on sodalite crystallite morphology. The assumptionof a zero value for crystallite size for experiments which did not produce sodalite orproduced sodalite with impurities might affect the value of the "low level" effects of thevariables. It is recommended for a future researcher to examine the variables whichwere found to affect the morphology of sodalite crystal in a space in which allexperiments will produce sodalite to properly quantify the influence of each variable.

Sodalite with smaller crystallites adsorbed more water vapor in the same timethan those with larger crystallites. Sodalite with an average crystallite diameter of 2.8urn produced by batch number 10 adsorbed about 73% of the water vapor in 900 mL86% humid air. Sodalite with an average crystallite diameter of 6.9 urn adsorbed 41.50/0of the water vapor in 900 mL 86% humid air. This is probably because the same massof sodalite with smaller crystallite has more accessible surface area for water adsorptionthan sodalite with larger crystallite size.

Sodalite was regenerated for re-use in a short time. Using a dry airflow rate of20 mL/min, "wet" sodalite was regenerated in fifteen minutes at 110 "C. Using a higher


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52flow rate of dry air of 100 mL/min, "wet" sodalite was regenerated in six minutes at110C.

Sodalite did not interfere with any of the organic compounds present in the 80Sstandard. Although sodalite with large, medium, and small crystallites did not show anysystematic adsorption of organic compounds, it is worth noting that smaller crystallitesgave the lower deviation from the blank run average value.

The interference of sodalite with NMHC reported by Randall Brown (Brown,2000) was probably due to the presence of impurities in his synthesis. In his synthesisRandall Brown used generic polypropylene bottles that might be contaminated withorganic material which led to the formation of a second crystal phases, whereas newname brand labware was used in this work. The presence of the second phase inBrown's materials might have been identified if a higher resolution x-ray diffractometerhad been available. Unfortunately, none of those bottles remain to allow this to betested. In the current work, new Nalgene bottles were used for synthesis.

Sodal ite is a very attractive opt ion for use as desiccant. The use of sodalite infield studies is highly recommended.


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53REFERENCES

Barrer, R. M., "Hydrothermal Chemistry of Zeolites," Chemistry & Industry, 19,757-758, (1983).

Bellat, J. P.; Molse, J. C.; and Methivier, A., "Adsorption ofwater vapor on X and Yzeolite exchanged with barium,"Microporous and Mesoporous Materials, 43,91-101, (2001).

Bhatia, Subhash, ZEOLITE CATALYSIS PRINCIPLES and APPLICATIONS, CRePress Inc., Boca Raton, 1946.

Brasseur, l.J., "Tropospheric Ozone", in Atmospheric Chemistry and Global Change,edited by G.P. Brasseur, J.J. Orlando, and G.S. Tyndall, Oxford UniversityPress, New York, 1999.

Breck, D. W., Zeolite Molecular Sieves: Structure, Chemistry, and Use, John Wiley &Sons, Inc.: New York, 1974.

Brown, Randall, SODALITE SYNTHESIS AND USE AS A DESICCANT FOR GASCHROMATOGRAPHY ANALYSIS OF AMBIENT AIR. Dept. ofChemicalEngineering, Ohio University, Athens, Ohio, Master Thesis, 2000.

Changlu Shao, Xiaotian Li, Shilun Qiu, Feng-Sholl Xiao, "The role ofpyrocatechol as acomplex agent for silicon in the synthesis of large single crystals of silicasodalite zeolite," Microporous and Mesoporous Materials, 33, 215-222, (1999).

Ciccioli, P.; Cerinato, A.; Brancaleoni, E.; Frattoni, M.; Liberti, A ~ GasChromatography, J High Resolut. Chromatogr, 15,75-84, (1992).

Gardiner, William P., Statistical Analysis Methods For Chemists A Software-basedApproach, THE ROYAL SOCIETY OF CHEMISTRY: Cambridge, 1997.

Felsche, F., Luger, S., and Baerlocher, Ch., Zeolites, 6, 367-372, (1986).

Helmig, Detlev, and L. Vierling. "Water Adsorption Capacity of the Solid AdsorbentsTenax TA, Tenax GR, Carbotrap, Carbotrap C, Carbosieve SIll, and Carboxen569 and water Management Techniques for the Atmospheric Sampling ofVolatile Organic Trace Gases," Analytical Chemistry, 67, 4380-4386, (1995).


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54Hyver K. J., Sandra P., High Resolution Gas Chromatography. Hewlett-Packard Co.:USA, 1989.

Jenking, Ron and Snyder, Robert L., Introduction to X-ray Powder Diffractometry, JohnWiley & Sons, Inc.: New York, 1996.

Joseph J. Bufalini, Robert R. Amts, Atmospheric Biogenic Hydrocarbons Volume 2,AnnArbor Science Publishers, Inc.: Michigan, 1981.Mark C. Barnes, Jonas Addai-Mensah, Andrean R. Gerson, "The mechanism of thesodalite-to-cancrinite phase transformation in synthetic spent Bayer liquor,"

Microporous and mesoporous Materials, 31,287-302, (1999).Museum of Science, "How the SEM Works", http://www.mos.org/slnlSEM/works.html,

January 15,2001.Smimiotis, Panagiotis G., Brar, Tejinder, France, Paul, "Control ofCrystal Size andDistribution ofZeolite A," Ind. Eng. Chern. Res., 40, 1133-1139, (2001).Tomohiro Hayashi, Hidemoto Shiga, Masayoshi Sadakata, and Tatsuya Okubo,"Hydrothermal groeth ofmillimeter-sized aluminosilicate sodalite singlecrystals in noble metal capsules," J. ofMaterials Research, 13,891-895, (1998).Whittingham M.S., "X-RAY ANALYSIS OF A SOLID,"http://imr.chem.binghamton.edullabs/xray/xray.html, November 8, 2000.Zeolyst International, "Thousands ofApplication",

http://www.zeolyst.com/html/app.html. January 16, 2001.Young, David, Dept. ofChemistry, Ohio University, Athens, Ohio, personalcommunication, June 1998.


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Appendix ~ X-Ray Diffraction Patterns of crystalline materials synthesized

ZQ1836.RAW.. -_.-.._--'" -_.......... . __._--_._--_. ' _-_ -----_.__ _ _.- - - - - ,en r = ~ = = - - . . . - - - . - - ! , S_OD,EX2 _._ - __ - _.,-_ ..- - - .._ ..~ ,( \ . J ~Ln1

1I. ,- ' I~ T ' T ..rr. r,trTITTTTl"TT'T"1'T'r'TTl'TT1"f'TT"f'TrTT'p"Tl'TTTTrrT'q-r'TT-r-r' rrr"tT-rPTTT'rrrrTTT1

55

10. 15. 20 . 25. 3 0 35. 40. 45. 50.

_._._ __ _.__ ...._. ..__ Z 0 1 8 4 6 ~ __ __.._._ _ " v~ F - - - - -.----..------ SODEX4 ------.... - - - - . - - - - . - - - - - - - ~rul!

10. 15 20. 25. 30. 35. 40 45. 50.


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Z01847.RAWSOOEX5 -----.- _ _----l._.__ ..._--_ .._._._----- - - -_ .

56

!ijII II iL , ~ ~ ~ ~ - .


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57r - - ~ u u - . . - . . ---- . -

I01849.RAW! -.. ,.... ~ ~ - _ _ - - s o D . : : E-:7 - ..- --- .- ..-.-.- -----.. - . - _ _ ~ - - - I,_.__.__._-_._-------_. - ----,---_.__ .__ .:-_..__ _.__ .._._-_._------- --.--..__._---. .

I

iII.: ; '\ ."

10. 15. 20. 25. 30. 35. 40. .45. 50 .

II


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r - - - - " - _ _ _ ~ _ ~ , - - - - -

c o l - - ~ -o!~ !

i!1

ZO 1851. R A ~ ~---------.-------- . - - - . - - - ~ - .. , - - ~ - - - - lSOOEX9:

IIIIIIiIIjl1

58

10. 15. 20. 25. 30. 35. 40. 45. 50.

J-_.~ I!

zn 1852. R . A ~ ~SOOEX10

IiIII,.."'...... ~ " ' .. " , I II I' " : : . , . .: ' ~ ~ ' : ~ ~ ~ . : : ~ ~ ~ . ~ , ' I f I ' I ~ ; ~ T ~ T l ~ ~ ' I f I ' : \ : ~ T ~ ~ ' : ' , 1 f I ..~ ~ ~ ; ~

10. 15. 20. 25. 30. 35. ~ 1 . 45. 50.


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59ZO 1853. R A \ ~

~ . _ . _ . ~ . __._ _.__._._._._. H ' _ ~ _ ' _ ~ ~ _ - _ ..- _ __ ..__ __ . ~ - - - - - - ,SODEXii iL ! 1 1 - - - - - ~ - _ - - " _ _ - - _ _ _ .._,-____-__----!_ ._ -_ ._ _-- - ~ ..- -- _ _.. __ . _ . ~ _ . _

(0 I 11Ui 'I ;

I IIj I

j1I\IItIII11IIIII. j.. -.-4"j

.-...; 1iI

~ - - - r r r r - r r r - r r r r T r T T r l " r T r T T T J T T T T T l ' T r T - r T ' T ' l T " f T rT: p r r r r r T r T T T T " f T T ' ~10. 15. 20. 25. 30. 35. 40. ~ . 50.

Z01854.RAWr _._ . , , ,...._ "._ __._.__ _u_ _.__ .._.__ -"--"- '-"--- '--".--..-.----- --.. - --.-- -.--- -.---..-- -.-------=1.SOOEXi2t--- -.-.---- -.-. _-_._.'" w y A Y . ~ . _ _ . . _ y . . ... .- - - _ ~ . - ..~ . ,.......... _ ~ __._-_._- - - -_.ru 'm' I(\ j

1ijIfr".,,:!j ' ' ' / ~ ' .~ r F T ~ T T ' J r . r ~ r r r T ' T ' ]', ! . , I I ' F r T r T . - r : ~ : T : ' F F F I ~ " ; ' : ~ ; ~ " I ' 1 ~

10. 15. 20. 25. 30. 35. 40. 45. 50.


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, - - - - - - - - - - - ~ _ .._---------------._- - .._-_..... _ - . _ . ~en ---------- ..


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61

~ III

Z01857.RAWSODEX15

~ ~ . _ o__ __ - ._ _o or-- _

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ZO 1858. R A \ ~r- ~ = = ~ = - = _ _ _ ~ .._===.. = = = - - ~ O - O E X 1 6 " - - " - - - - - - - - - " - - - " - - - ~ ~ ~ ~ = - ~ = " : l~ I

Ii!II

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Z01859.RAW~ - : _ - _ ~ ~ ~ - =__ ~ __ ~ _ O _ E _ ~ ~ - _ - - - = _ ~ - - - - - ~ - - - - ~ - -I II II II

62

10. 15. 20. 25. 30 . 35. 40. 45 . 50.

10.

I- - - - - .-.,--...-.- .-------- .- . ~ . - ' _ _ _ 4I


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ZQ1863.RAWSODEX20

63

10. 15. 20. 25. 30. 35. 40. ,,15. 50.

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cuILn\

10 . 15. 20. 25. 30. 35. 40. 45. 50.


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64ZO 1865. R A ~ ~

..................,ij"._._----_ .. _ -

Z01866.RAWr-----.--.-- "-' _ ... o. _",_",___ _ ~ < ~ . , ~ ~ m ....< _... _ __ ,1 SODEX24 J-.;;;:rr------ --..- --..--.- - _ . ' m _ r - - _ ~ _ ___-----________ _-_ _ , -.- --- .-- .---- .

( '\J i IiCUj tJ

( ::

.:

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,.__ ._.........._....I0 1 ~ ' - - - - - -(,0:~

ZO 1868. R A ~ ~SODEX25.._-_ ......,..------_._----

65

10. 15. 20. 25. 30. 35. 40. ,.15 . 50 .

.... _ - - - - - - _ . _ - - - ~ .

l01869.RAW.__._ . _ _ '_UN '' '_ . .' N U . ' _ ' h ~ M N . __ ~ N._''.__ ~ _ __ ~ _ __ _._.- __..__ _ _ ......._ _ _ _ ,SODEX26 !

_ ._ ._ ._ , .0_'_00. __ _ .. _ .


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zo 1870 .Rf\W66

10. 15. 20. 25. 30. 35. 4 0 45. 50.

1-~ C\JtrI!I

za 1871. R A Y ~SOOEX28 I- -

II


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67ZOi873.RAWSODEX30

l - ~ ~ - - _ y , - , _ , h ' h h _ h .._ ,h .

iIIII

il-, .I v\---""_''''/''/'", ... / . . / ' ~ / \ ' /V" . .;> /,1t r P T r y r T T r ' T r T T T " " ' r T . . : P T r T r T ' T r - F T ' T r T ' T ' - y ' T Y . . . . , . . , T ' T ' T " ' T r p T ' T ' T I ' T r ~ ~

01 .LOiIl1t

10. 15. 20. 25. 30. 3.5. 40 . 45. 50.

II' ! i i ' I ' I I ! I I ' 1 ' T'T'f"'T' l 'T"f" 'TTl 'T 'TrT 'TTfTT TTr,rrrT I I ' I' I 'T'T'T"r....,.....,

, - - - ~IIII1ji

. .. j'i f

lOi874.RAWSOOEX311...4),......------

~ IIIiiIII1!i

10. 15. 20. 25. 30. 35. 40. 45. 50.


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1----------------CD1i----0 1(\J!

1IjIj\

Z 0 1 8 7 5 . R A ~ ~___----------SO-OE-}-:3-2 - ..---- . - . - --..- . - - ~ . ._. -l;IilIjiiiI

68


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Appendix B: Scanning Electron Microscopy Images

Sodalite batch # 2

Sodalite batch # 5

69


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Sodalite batch # 6

Sodalite batch # 9

70


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Sodalite batch # 10

Sodalite batch # 13

71


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Sodalitebatch# 14

Sodalitebatch# 18

72


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Sodalite # 20

Sodalite batch # 21

73


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Sodalite batch # 22

Sodalite batch # 25

74

,


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Sodalite batch # 26

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