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IJRRAS 10 (3) ● March 2012 www.arpapress.com/Volumes/Vol10Issue3/IJRRAS_10_3_04.pdf
397
ADSORPTION CONSIDERATION OF Ni2+,
Fe2+,
Cu2+,
Cr3+
AND Co2+
BY
PHOSPHATE ORE AND IT’S CONCENTRATE FROM SOLUTION IN
ISOTERM MODELS
M. Kargar Razi
* & S. Yahyaabadi
Islamic Azad University (North Branch of Tehran)-Iran
*Email: [email protected]
ABSTRACT
In this investigation, the adsorption behavior of natural phosphate rock and it’s concentrate with respect to Fe3+
،Ni2+
، Co2+
، Cu2+
Cr و 3+
has been studied, in order to consider its application to purity of electroplating waste water
pollution. The batch method has been employed, using metal concentrations in solution ranging from 2-40 ppm with
mixing process. The effect of pH, concentration of heavy metals and times (10-20min) is considered.
The results of their removal performance in 40 ppm concentration, pH =8 and 10 minutes are obtained as
Cr3+
> Cu2+
> Fe3+
> Co2+
> Ni2+
for phosphate rock and the sequence can be given as Cr3+
> Fe3+
> Cu2+
> Co2+
> Ni2+
for phosphate concentrate.
It was found that the adsorption phenomena depend on charge density and hydrated ion diameter .The same results
show that maximum adsorption in pH=4.5, 7 for concentrate. According that results are accepted electrostatic
interaction in adsorption equilibrium.
The Langmuir adsorption isotherm constant corresponding to adsorption capacity, were found to be as Cr3+
> Fe3+
>
Cu2+
> Ni2+
>Co2+
for phosphate soil and Cr3+
> Fe3+
> Cu2+
> Co2+
> Ni2+
for phosphate concentrate. Sorption of
metallic cations are considered in pH 4.5, 7and 8.
More ever the qm (mmol/g) is depended to the initial concentration, adsorption percent and kd (as distribution
constant).
These results show that phosphate rock and its concentrate are hold great potential to remove cations heavy metal
species from electroplating waste water.
Keywords: Electroplating waste water, Phosphate ore, Phosphate Concentrate, Heavy metal cations.
1. INTRODUCTION
The removal of toxic and heavy-metal contaminants from aqueous waste streams and industrial effluents such as
electroplating waste water is one of the most important environmental issues being faced the world over. The
commonly used procedures for removing metal ions from waste water include chemical precipitation, ion-exchange,
reverse osmosis and solvent extraction [1]. However, these methods have certain disadvantages such as incomplete
metal removal, high reagent and energy requirements, generation of toxic sludge or other waste products that require
disposal. The hazardous wastes generated from mining and smelting operations also need to be decontaminated
before entering the ecosystem.
Heavy metals such as chromium , nickel , lead, copper, cadmium ,Iron , cobalt , have a number of applications in
industries such as electroplating, steel and alloys, leather tanning, paints and paper, to name a few [2].
In the last decade, a great effort has been invested to develop new sorbents such as calcite [3-6], goethite [7],
birnesite [8] and wool [9], activated sludge [10], iron oxide coated sand [11], and zeolite (clinoptilolite) [12-15].
Silica [16, 17], fishbone apatite [18] and polymers [19–21]. Phosphate minerals have been shown to possess the
potential to adsorb heavy metal ions from aqueous solutions [22].
All of the inorganic phosphate sources apatite’s are most readily available. Apatites are often identified by the
general formula M10 (XO4)6Y2 where Me2+
is a divalent cation, (XO4)3−
is a trivalent anion and Y− is a monovalent
anion
[23-25]. Apatite of different origins (mineral, synthetic, and derived from animal and fish bones) have been used as
sorbents of heavy metals such as Pb, Zn, Cu, Cd, Fe, Cr, Ni, Pd, Co [26-32].
It has probably mechanisms for metal retention by phosphate minerals included: (1) ion exchange processes at the
surface of PR [33]; (2) surface complexation [34]; (3) precipitation of some amorphous to poorly crystalline, mixed
metal phosphates [35]; and (4) substitution of Ca in PR by other metals during recrystallization (co precipitation)
[36]. However, it is difficult to quantify the relative contribution from each mechanism that is responsible for metal
removal and it appears that all of the mechanisms may work together.
In this study, copper, chromium, nickel, iron and cobalt removal from aqueous solutions were investigated by using
a phosphate rock (PR) and phosphate concentrate (PC) sample. Langmuir isotherm model was used for the
IJRRAS 10 (3) ● March 2012 Razi & Yahyaabadi ● Adsorption Behavior of Natural Phosphate Rock
398
evaluation of findings, In addition, the effect of various parameters affecting sorption behavior such as time, pH and
concentration of heavy metals as pollutants are considered and data on sorption isotherms are presented. In addition,
infrared spectra (FT-IR), X-ray fluorescence (XRF), specific surface area measured (BET) and X-ray diffraction
(XRD) techniques are verified for characterization of phosphate and its concentrate as sorbents.
2. MATERIAL AND METHODES
2.1. Materials
Rock phosphate (PR) and phosphate concentrate (PC) used as adsorbent in this investigation was obtained from the
phosphate deposits in Esfordi mine of Bafgh (Iran).The sample was crushed, screened and classified using ASTM
standard sieves. 0.5–0.125 mm particle size was used for the removal of Fe3+
, ،Ni2+
، Co2+
، Cu2+
and Cr3+
ions from
aqueous solutions as real model of electroplating waste water. Phosphates concentrate in the size range of 0. 25.
Chemical and Physical analyses of the rock phosphate and phosphate concentrate were carried out by standard
gravimetric, volumetric and XRF methods which results are summarized in Table 1 and Table 2.
Sorbents were analyzed by X-ray diffraction (XRD) for the determination and identification of structural changes of
the PR and PC samples, and the results are summarized in Figs. (20, 21).
The specific surface area was determined from low-temperature nitrogen adsorption isotherms, using a Micrometrics
ASAP 2000 instrument, and the point of zero charge (PHPZC) were measured by batch equilibration technique, with
0.1mol/dm3 KNO3 as an inert electrolyte.
For the infrared spectroscopy, the phosphate samples were ground to a very fine powder form in an agate mortar for
a minimum of 10min.
After drying at 105 °C for 2 hrs , the results are summarized in Figs. (22-25). The Sorbents with Cu2+
before and
after adsorption were tested by IR spectral analysis. An IR transmittance spectrum of the ground samples were
obtained in the 370–4000 cm−1
range with a Perkin Elmer spectrum on FT IR spectrometer.
Table 1. Physical analysis of Sorbents
Physical characteristics
Phosphate concentrate
Rock phosphate
CEC meq/1000gr
porosity
Bulk density (g/cm3)
BET surface area (m2/g)
0.695
40%
3.10
0.2341
1.21
32%
64.3
1.0436
Table 2.Chemical analysis of Sorbents
Constituents (% wt/wt) of
Phosphate concentrate
(% wt/wt) of
Rock phosphate
SiO2
Al2O3
Ca O
Mg O
P2O5
Fe2O3
TiO2
F-
C l-
L.O.I
2/26
0.18
56.44
0.74
31.98
3.49
0.10
1.30
0.23
1.04
13.80
0.78
23.92
1.90
17.34
36.89
0.86
0.21
0.15
2.66
2.2. Preparation of Metal Solution
Stock solution (250 mg/l) of different metal ions (Fe3+
, ،Ni2+
، Co2+
، Cu2+
and Cr3+
) were prepared from analytical
grade Iron Chloride , copper Chloride, chromium chloride, nickel chloride and cobalt chloride using double distilled
water and Serially diluted to prepare solutions of varying initial concentration for experimental works[37].
IJRRAS 10 (3) ● March 2012 Razi & Yahyaabadi ● Adsorption Behavior of Natural Phosphate Rock
399
2.3. Experimental
Batch experiments included: the kinetic studies, pH effect and sorption isotherms studies. Sorption experiments for
the kinetics study were conducted as follows: sorbents sample (1g) were containing with 50 ml of solution of
different concentration (2, 5, 10, 20, 30 and 40 mg/L) and pH (4.5, 7, 8) of individual metal ions. The suspension
was mixed at predetermined periods of time (5, 10, 20 min) at room temperature.
Then, the suspensions were filtered and the concentration of ions in the filtrate were analyzed using an Atomic
absorption spectrophotometer (Varian AA 240).Each Absorbance was recorded in triplicate, and mean of values
were used for the concentration calculations.
2.4. Effect of pH
The effect of pH on the metal uptake of the different metal ions on phosphate rock (PR) and phosphate concentrate
(PC) is a very important parameter. An initial metal ions solutions concentration of 40 mg/1 was used in conjunction
with the PR and PC samples. Contact time was 5, 10 min and, Initial pH of solution was adjusted to 4, 7 and 8.
2.5. Effect of residence time
In these experiments, the suspensions containing sorbents and 40mg/l ions of metal solutions were shaken in
different time (5, 10, 20 min), filtrated and analyzed to determine the metal cations concentration.
2. 6. Effect of concentration
Initial ions of metal concentrations of 2, 5, 10, 20, 30 and 40 mg /1 were performed at pH=7 and t=10min with PR
sample and PC.
2.7. Adsorption isotherms
Isotherms are considered by Langmuir and Freundlich equation models. Adsorption isotherms are essential for the
description of how Fe3+
, ،Ni2+
،Co2+
، Cu2+
and Cr3+
concentration interacts with the PR sample and PC are useful to
optimize the use of PR and PC samples as adsorbents. Langmuir model was used for the evaluation of experimental
results. The Langmuir isotherm is based on assuming a monolayer sorption onto a surface with a fixed number of
well defined sites; the equation is given below [38-40]:
qe = qmKCe/ (1 + KCe) (1)
where Ce is the equilibrium liquid-phase concentration (mg/l), qe the equilibrium amount adsorbed (mg/g), qm the
maximum amount of sorbate per unit sorbent (adsorption capacity) to form a complete monolayer, and K is the
Langmuir constant related to the affinity between sorbent and sorbate.
The equilibrium adsorption uptake, qe, can be calculated from the mass balance at the adsorption process.
qe = (Co -Ce). V/w (2)
Where Co is the initial sorbate concentration (mg/l), Ce the equilibrium sorbate concentration (mg/1), V the volume
of the solution (1), and w is the amount of the adsorbent (g).
The Freundlich model attempts to account for surface heterogeneity and is presented as follows:
qe= KfCe '/"
(3)
Where Kf and n are Freundlich constants that are related to the adsorption capacity and intensity,
Respectively. Figs.(16-20)Shows Langmuir isotherms of Fe3+
, ،Ni2+
، Co2+
، Cu2+
and Cr3+
sorption on the PR, PC
samples (θ= 27°C, pH 7, t=10min).
3. RESULTS AND DISCUSSION
3.1. Effect of pH
As known, the pH value of a solution strongly affects in heavy metal adsorption onto sorbents. Therefore; the
adsorption of ions on the PR and PC samples was initially studied depending on the solution pH.
This may be related to both the electrostatic repulsive forces between phosphate particles and metal ions, and the
hindering of metal ions sorption on the surface of phosphate particles (sorbent surfaces) due to the sorption of H+
ions on the particle surfaces. The increase in Fe3+
, ،Ni2+
، Co2+
، Cu2+
and Cr3+
removal beyond pH =4 is due to the
decrease in electrostatic repulsive forces because of low concentration of H +. In addition, as the pH goes up, the
removal recovery may increase due to the enhanced ionization of adsorption sites. As is known, at higher pH values,
metal ions precipitate as metal hydroxides.
The maximum sorption capacity for Fe3+
, ،Ni2+
، Co2+
، Cu2+
and Cr3+
were found to be at pH value between 7and 8
for PR and PC. The pH values were chosen to avoid metal precipitation at higher pH values. Figs. (1-5) Shows that
IJRRAS 10 (3) ● March 2012 Razi & Yahyaabadi ● Adsorption Behavior of Natural Phosphate Rock
400
PR is the best sorbent of all metallic ions and the best at different pH values compared to PC as well.Itis observed
that removal of Fe3+
, ،Ni2+
، Co2+
، Cu2+
and Cr3+
reaches maximum adsorption at pH 8.
Figure1. Sorption of Fe3 on (PR) and on (PC), at different pH; 1 g solid/50 ml, M: 40 mg/l, t = 5, 10 min, T: 25°C.
Figure2. Sorption of Ni2+on (PR) and on (PC), at different pH; 1 g solid/50 ml, M: 40 mg/l, t = 5, 10 min, T: 25°C.
Figure 3. Sorption of Co2+ on (PR) and on (PC), at different pH; 1 g solid/50 ml, M: 40 mg/l, t = 5, 10 min, T: 25°C.
Figure4. Sorption of Cu2+ on (PR) and on (PC), at different pH; 1 g solid/50 ml, M: 40 mg/l, t = 5, 10 min, T: 25°C.
IJRRAS 10 (3) ● March 2012 Razi & Yahyaabadi ● Adsorption Behavior of Natural Phosphate Rock
401
Figure 5. Sorption of Cr3+ on (PR) and on (PC), at different pH; 1 g solid/50 ml, M: 40 mg/l, t = 5, 10 min, T: 25°C.
3.2. Effect of contact time and concentration
The effect of contact time for ions removal is given in Figs (6-10). As can been seen, the percentage of ions removal
increases with the contact time up to 5 min. The amount of ions adsorbed per unit mass of adsorbents increased with
the increasing of the initial ions concentrations. Figs. (11-15) that Shows that PR is the best sorbent of all metallic
ions and the best at pH =7 values compared to PC as well.
Figure 6. Effect of contact time on the removal of Fe3+ on (PR) and on (PC), at different time; 1 g solid/50 ml, M: 40 mg/l T:
25°C.
Figure7. Effect of contact time on the removal of Ni2+on (PR) and on (PC), at different time; 1 g solid/50 ml,
M: 40 mg/l T: 25°C.
Figure8. Effect of contact time on the removal of Co2+on (PR) and on (PC), at different time; 1 g solid/50 ml, M: 40 mg/l T: 25°C.
IJRRAS 10 (3) ● March 2012 Razi & Yahyaabadi ● Adsorption Behavior of Natural Phosphate Rock
402
Figure 9. Effect of contact time on the removal of Cu2+ on (PR) and on (PC), at different time; 1 g solid/50 ml,
M: 40 mg/l T: 25°C.
Figure 10. Effect of contact time on the removal of Cr3+on (PR) and on (PC), at different time; 1 g solid/50 ml,
M: 40 mg/l T: 25°C.
Figure 11. Effect of PR sample and PC on removal of Fe3+ for different concentration Values (1g solid/50 ml, t=10 min, pH=7,
T: 25°C).
Figure 12. Effect of PR sample and PC on removal of Ni2+ for different concentration Values (1g solid/50 ml, t = 10 min, pH=7,
T: 25°C).
IJRRAS 10 (3) ● March 2012 Razi & Yahyaabadi ● Adsorption Behavior of Natural Phosphate Rock
403
Figure 13. Effect of PR sample and PC on removal of Co2+ for different concentration Values (1g solid/50 ml, t = 10 min,
pH=7, T: 25°C).
Figure 14. Effect of PR sample and PC on removal of Cu2+ for different concentration Values (1g solid/50 ml, t = 10 min, pH=7, T: 25°C).
Figure 15. Effect of PR sample and PC on removal of Cr3+ for different concentration Values (1g solid/50 ml,
t = 10 min, pH=7, T: 25°C).
3.3. Adsorption isotherms
Adsorption isotherms are shown in Figs. (16-20) show that the adsorption follows the Langmuir model for Fe3+
,
،Ni2+
، Co2+
، Cu2+
and Cr3+
.The Langmuir model parameters and the statistical fits of the sorption data to this
equation are given in
Table 3.
IJRRAS 10 (3) ● March 2012 Razi & Yahyaabadi ● Adsorption Behavior of Natural Phosphate Rock
404
Figure16. Langmuir isotherms of Fe3+ (1g solid/50 ml,t = 10 min, pH=7, T: 25°C).
Figure 17. Langmuir isotherms of Ni2+ (1g solid/50 ml,t = 10 min, pH=7, T: 25°C).
Fig.18. Langmuir isotherms of Co2+ (1g solid/50 ml, t = 10 min, pH=7, T: 25°C).
Fig.19. Langmuir isotherms of Cu2+ (1g solid/50 ml, t = 10 min, pH=7, T: 25°C).
IJRRAS 10 (3) ● March 2012 Razi & Yahyaabadi ● Adsorption Behavior of Natural Phosphate Rock
405
Fig.20. Langmuir isotherms of Cr3+ (1g solid/50 ml, t = 10 min, pH=7, T: 25°C).
3.4. XRD analysis
For the determination of structural changes of the PR and PC samples, XRD analysis was done with original
samples (Figs. 20, 21). It was shown that both original samples contain apatite [Calo (PO4)6(OH, F, C1)2],
flourapatite[Ca5(PO4)3F], hydroxyapatite [Ca10(PO4)6(OH)2], quartz, Hematite and Calcite, But phosphate rock (PR)
have also a talc.
Phosphates concentrate (PC) where it was processed, so the amount of substances such as talc and gypsum it
dropped. Sorbents were analyzed by X-ray diffraction (XRD), using a Broker D4 diffraction system, with CuKa1.2
Nifiltrated radiation.
The patterns were registered in the 2θ range 4–70°, and the results are summarized in Figs. (20, 21).
Table 3 . Characteristic parameters and determination coefficient of the experimental data
according to the Langmuir equation model.
Metal
ions
phosphate concentrate (PC) phosphate rock (PR)
K
l/g
qm
(mg/g)
q'm
(mmol/g)
R2 K
l/g
qm
(mg/g)
q'm
(mmol/g)
R2
2+Co 0.120 1.084 0.018 0.999 0.206 2.146 0.036 0.785
3+Cr 0.398 0.315 0.006 0.778 0.659 1.992 0.038 0.962
2+Ni 0.692 0.351 0.0059 0.894 2.867 0.634 0.010 0.743
3+Fe 0.354 2.659 0.047 0.955 0.0021 23.419 0.419 0.999
2+Cu 6.91 0.959 0.015 0.9715 3.652 1.814 0.028 0.999
Figure21. XRD patterns of phosphate concentrate
IJRRAS 10 (3) ● March 2012 Razi & Yahyaabadi ● Adsorption Behavior of Natural Phosphate Rock
406
Fig.22. XRD patterns of phosphate rock
3. 5. Infrared spectra analysis In order to determine structural change on the PR and Pc samples after its treatment with 20 mg/1 of copper (II), FT-IR analysis
was performed. Figs. (22-25). Show the spectra of raw and treated PR and Pc samples. In both spectra (PR and Pc samples), the
sharp bands near 450, 900, and 2000-2100 cm-1 define the Si-P stretches. The peak at 879 cm -1 is associated with the PO43-
group. The bands between 1000-1100 cm -1 are Si-O, and those at 1461, 1643 and 2900 are C=O, 2450 is P-H. The sharp peak
around 3536 is the O-H stretch. All peaks defined above are related with the mineralogical composition of the sorbents (PO4,
SiO2 and CO3). Peak displacement and peak intensity is decreasing and increasing should define the change in the structure with
copper (II) and imply the related functional groups to be responsible for the adsorption. From these findings, it can be concluded
that copper ions are sobbed on the PR and PC samples surfaces.
Figure 22. FTIR spectra of phosphate concentrate before adsorption of [ Cu2+] =40mg/l
Figure 23. FTIR Spectra of Phosphates concentrate after adsorption of [ Cu2+] =40mg/l
Figure.24. FTIR spectra of phosphate rock before adsorption of [ Cu2+] =40mg/l
IJRRAS 10 (3) ● March 2012 Razi & Yahyaabadi ● Adsorption Behavior of Natural Phosphate Rock
407
Figure 25. FTIR spectra of Phosphate rock after adsorption of [ Cu2+] =40mg/l
4. CONCLUSIONS
All of the experiments performed on mineral soil and its concentrate as natural and industrial processed sample
indicate its natural entity in mixed reactions adsorption as normal species with experiment capability on planned
concentrations.
Performance of adsorption tests in laboratory and batch scale to achieve similar amounts at pilot and industrial
scales have common and implemented conditions.
Results of adsorption studied about effects of sample concentration, pH, time of contact and primary concentration
of mineral phosphate soil and it’s concentrate, as well as reviewed isotherm curves based on Langmuir equations
that in general agreed with experimental data results.
Increasing trend of ratio on radious according to adsorption in PH=4.5 for soil and PH= 7 for it’s concentrate have
similarity. We also observe similar changes in PH= 4.5 for soil and PH=8 for it’s concentrate. Maximum quantity of
adsorption and comparison studies against burden physical ratio to radious are explaining effects of cavity size and
electrostatic burden on soil and its concentrate.
Although changes in increased adsorption in PH=8. 7 and PH=4.5 are low, but considering the two physical factors
of burden and cation radious, they can be linked to environment chemical conditions. Value R2, qm, K using
computing software can be achieved, the absorption capacity and energy adsorption depends. Langmuir model
indicates effectively data adsorption in curve with values of R2 (correlation coefficient), so that R
2 for phosphate soil
is:
0. 99>R2>0. 74 and for its concentrate is 0. 99>R
2>0.72.According to qm and q'm given parameters, adsorption for
studied metals with soil adsorbent is Fe > Co > Cu > Ni > Cr and with soil concentrate is Fe > Co > Cu > Ni > Cr.
The basic nature of phosphate soil and it’s concentrate indicate similarity in metals adsorption order.
The generalization of this explanation in regards to metal adsorb in solution is divergent adsorption phenomenon
and instability kinetics that caused change in this process.
Langmuir curves data for different metals in phosphate soil and it’s concentrate as adsorbent are adsorption
phenomenon especially in balance manner based on heterogeneous adsorbent, but in general, small difference with
drawing curves in some concentrations in ideal form make us approach to predict ideal conditions.
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