Utilization of rice husk fly ash in the color glass production

Procedia Engineering 32 (2012) 670 – 675

1877-7058 © 2012 Published by Elsevier Ltd.doi:10.1016/j.proeng.2012.01.1325

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Procedia Engineering 00 (2012) 000–000

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I-SEEC2011

Utilization of rice husk fly ash in the color glass production

J. Kaewkhaoa,b* and P. Limsuwanb,c

aCenter of Excellence in Glass Technology and Materials Science (CEGM), Nakhon Pathom Rajabhat University, Nakhon Pathom, 73000, Thailand

bThailand Center of Excellence in Physics, CHE, 328 Si Ayutthaya Rd., Bangkok 10400, Thailand cDepartment of Physics, Faculty of Science, King Mongkut’s University of Technology Thonburi, Bangkok, 10140 Thailand

Elsevier use only: Received 30 September 2011; Revised 10 November 2011; Accepted 25 November 2011.

Abstract

In this research work, the glasses were prepared by rice husk ash from Yasothon Province, Thailand. The result shows that, after sintered at 1,000°C (RHA sample), rice husk ash can be used in colorless and color glass production. The color glass can be prepared from RHA and showed light blue (CuO doped), brown (MnO2 doped), deep blue (CoO doped), pink (Er2O3 doped) and green (Cr2O3 doped) color. The color of glasses was confirmed by UV-Visible spectrophotometer. This research is useful in the development of glass from ash and increased utilization of industrial waste.

© 2010 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of I-SEEC2011

Keywords: Color glass; Rice husk ash, Density; Refractive index

* Corresponding author. Tel.: +6634-261-065; fax: +6634-261-065. E-mail address: [email protected].

671J. Kaewkhao and P. Limsuwan / Procedia Engineering 32 (2012) 670 – 6752 J. Kaewkhao and P. Limsuwan / Procedia Engineering 00 (2012) 000–000

1. Introduction

Rice has been one of the most important agricultural products of Thailand since ancient time. It was cultivated not only for domestic consumption but also for export. Consequently, several million tons of rice husks, which can be considered as agricultural waste, are obtained every year. It was found that when rice husk is burnt, the resulting black ash contains silica. However, this silica from rice husk carries too many impurities and exhibits some inferior properties. As a result, research has been carried out to convert this rice husk into high purity amorphous silica. Several methods for preparing silica from rice husk have been proposed [1, 2].

In the glass science, color is the most obvious property of a glass object. It can also be one of the most interesting and beautiful properties. Although color rarely defines the usefulness of a glass object it almost always defines its desirability. Once the methods of colored glass production were discovered, an explosion of experimentation began. The goal was to find substances that would produce specific colors in the glass. Some of the earliest objects made from glass were small cups, bottles and ornaments [3]. Colorations of different colors in glass were achieved by transition metal ions.

The objective of this research is to replace the silica prepared from rice husk to fabricate the color glass. Several important physical properties, i.e. density, refractive index and uv-visible absorption spectra were investigated. Apart from increasing the value of rice husk, it is also desirable to promote the use of color glass by reducing its raw material cost.

2. Materials and Methods

The raw rice husk ash (RRH) from the Yasothon Province, Thailand was placed in alumina crucibles and then sintered at 1,000 °C for 5 hours (RHA) in a muffle furnace. The chemical composition of RRH and RHA was analyzed by Energy Dispersive X-ray Fluorescence (EDXRF), with standardless mode supplied by Panalytical, Minipal4 spectrometer (PW 4030/45B) with Rh X-ray tube operation, for select the best ash in this experiment. The glass samples were prepared from formula;

55SiO2:13B2O3:1Al2O3:6.3CaO:4.5BaO:0.2Sb2O3: 20Na2O (use RRH and RHA as SiO2).

The color glass samples were prepared from formula;

(55-x)SiO2:13B2O3:1Al2O3:6.3CaO:4.5BaO:0.2Sb2O3: 20Na2O

where x is a molar percentage of dopant. In this work, the dopants are CoO = 0.5 mol%, CuO = 0.5 mol%, Cr2O3 = 0.03 mol%, MnO2 =1.0 mol% and Er2O3 = 3.0 mol %) (use RHA as SiO2).

Each batch weighs about 30 g was melted in alumina crucibles by placing them in an electrical furnace for an hour, at 1,100 °C. These melts were quenched at room temperature in air by pouring between stainless steel plates. The quenched glasses were annealed at 500 °C for 3 hours for reduce thermal stress, and cooled down to the room temperature. All glass samples were cut and polished in proper shape for further studies.

The densities of the prepared glasses were measured at room temperature, using the Archimedes displacement method where distilled water was the immersing liquid, the density is calculated according to the formula;

672 J. Kaewkhao and P. Limsuwan / Procedia Engineering 32 (2012) 670 – 675 J. Kaewkhao and P. Limsuwan / Procedia Engineering 00 (2012) 000–000 3

0000.1×−

=BA

A

www

ρ g /cm3 (1)

where wA and wB is the weight of the sample in air and distilled water, respectively. The density of water is 1.0000 g/cm3.

The Abbe refractrometer (ATAGO, 3T) and mono-bromonaphthalene as an adhesive coating were used in refractive index measurement with three times in each glass. The absorption spectra were performed using a UV-visible spectrophotometer (Varian, Cary 50), together with a dual light source capable of emitting ultraviolet spectra were recorded in the wavelength range 300-1,000 nm, using air as the reference.

3. Results and discussions

3.1 Chemical composition of rice husk ash

The chemical compositions of raw rice hush ash (RRH) and rice husk ash sintered at 1,000°C (RHA) as shown in Table 1. It was seen that the major composition of all ash (RRH and RHA) are SiO2. RHA was 1,000°C sintering temperature show 92.10% of silica. The result shows that the RHA sample is good enough for glass making.

Table 1. Chemical composition of ash samples

Weight % Ash

SiO2 MnO Fe2O3 P2O5 SO3 K2O CaO TiO2 CuO ZnO BaO Cl MgO Al2O3

Raw rice husk ash (RRH)

86.80 0.48 0.10 5.04 0.40 4.98 1.47 0.02 0.05 0.03 0.00 0.00 0.60 0.00

Sinteredat 1000 °C(RHA)

92.10 0.37 0.10 2.45 0.30 1.91 1.23 0.03 0.04 0.02 0.00 0.28 0.00 1.50

3.2 Glass from RRH and RHA

From Table 2, it was found that the density of glass from RRH and RHA are comparable. The glass from RRH and RHA were shown light green color and colorless, respectively (Fig. 1). This result indicates that the glass from RHA can be used in color glass production.


Table 2. Density, refractive index and color of glasses

Sample Density (g/cm3) Refractive index Color

RRH 2.7593±0.0014 1.5494±0.0000 Light green RHA 2.7557±0.0023 1.5498±0.0003 Color less CoO 2.7613±0.0010 1.5513±0.0001 Deep blue CuO 2.7672±0.0011 1.5497±0.0001 Light blue MnO2 2.7717±0.0011 1.5513±0.0001 Brown Er2O3 2.9915±0.0012 1.5662±0.0000 PinkCr2O3 2.7648±0.0022 1.5569±0.0001 Green

3.3 Glass color

The glass doped with Er2O3 has the highest density and refractive index than other glasses because it has the highest molecular weight and effect to the increasing in density. According to the classical dielectric theory, the refractive index depend on density and on polarisabilities of the atom in a given materials. Therefore, the refractive result corresponds with density value [4].

Fig. 1. The glasses samples from rice husk ash

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(a) RRH glass and RHA glass (b) RHA glass doped with CuO

674 J. Kaewkhao and P. Limsuwan / Procedia Engineering 32 (2012) 670 – 675 J. Kaewkhao and P. Limsuwan / Procedia Engineering 00 (2012) 000–000 5

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(e) RHA glass doped with Er2O3 (f) RHA glass doped with Cr2O3

Fig. 2. Optical spectra of RHA glasses with various dopants

Fig. 2 (a) is show the absorption spectra of RRH glass compared with RHA glass. The shoulder peaks around 380 and 450 nm are due to Fe3+ and board peak around 1,100 nm due to Fe2+ ions. It effects to light green color of RRH glass. For RHA glass, the Fe3+ and Fe2+ are not found, and the glass is colorless.

The RHA glasses doped with copper oxide produces a light blue color (Fig. 2. (b)). The absorption band near 800 nm (2B1g→2B2g) is due to Cu2+ ion in octahedral coordination with a strong tetragonal distortion [5].

From the absorption spectra of MnO2 doped glasses have predominant broad band around 500 nm (Fig. 2. (c)). This absorption band is assigned to a single allowed 5Eg →5T2g transition which it arises from the Mn3+ ions (3d4 configuration) in octahedral symmetry [6]. This result corresponds with brown color in glass.

The main absorption bands of Co2+ in tetrahedral symmetry from the ground state 4A2(F), to the 4T2(F),4T1(F) and 4T1(P) states (Fig. 2. (d)). The very intense absorption band centered about 600 nm was assigned to he spin- and electric-dipole-allowed 4A2(F)→4T1(P) transition [7], and shown deep blue color in glass.

For Er2O3 doped glass show pink color. It can be seen that the transition energy levels vary with the Er2O3 concentration and depend on covalency and the asymmetry of Er-O local structure among these host matrices. The in homogeneously broadened bands are attributed to the transitions from the 4I15/2ground state to the various excited states of the Er3+ ion. The spectra consists of various absorption peaks


corresponding to the transitions between the ground state 4I15/2 and higher energy states 4I13/2 (1,493 and 1,539 nm), 4I11/2, (976 nm) 4I9/2 (801 nm), 4F9/2 (654 nm), 4S3/2 (552 nm), 2H11/2 (524 nm), 4F7/2 (489 nm), 4F5/2 (451 nm), 4F3/2 (405 nm) and 2G9/2 (379nm) respectively (Fig. 2. (e)). This result corresponds with published literatures of Er3+ in difference glass matrices [8-10].

The green glass from Cr2O3 doped glass are observed in the absorption spectrum with peaks around 440 nm, identified due to the conventional transitions of Cr3+ ions viz., 4A2→4T1(F) (Fig. 2. (f)). Another band was found around 635 nm, due to 4A2→4T2 transition. Additionally, two significant kinks at 655 (4A2→2T1) and 690 nm (4A2→2T1) have been appeared on 635 nm band in the spectra [11].

4. Conclusions

In this research work, the glasses were prepared by rice husk ash from Yasothon Province, Thailand. The result shows that, after sinter at 1000°C (RHA sample), rice husk ash can use in colorless and color glass production. The color glass can prepared from RHA and show light blue (CuO doped), brown (MnO2 doped), deep blue (CoO doped), pink (Er2O3 doped) and green (Cr2O3 doped) color. This research is useful in the development of glass from rice husk ash, and increase utilization of industrial waste.

Acknowledgements

J. Kaewkhao would like to thank the National Research Council of Thailand (NRCT) for funding this research. P. Limsuwan would like to thanks King Mongkut’s University of Technology Thonburi for partially funding under National Research University project.

References

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[2] Chandrasekhar S, Pramada PN and Praveen L. Effect of Organic Acid Treatment on the Properties of Rice Husk Silica. J. Materials Science 2005; 40: 6535.

[3] http://geology.com/articles/color-in-glass.html [4] Marler B. On the Relationship between Refractive Index and Density for SiO2-polymorphs. Physics and Chemistry of

Minerals 1988; 16: 286. [5] Lakshminarayana G and Buddhudu S. Spectral analysis of Cu2+ : B2O3-ZnO-PbO glasses. Spectrochimica Acta Part A:

Molecular and Biomolecular Spectroscopy 2005; 62: 364. [6] Chakradhar RPS, Sivaramaiah G, Rao JL and Gopal NO. EPR and optical investigations of manganese ions in alkali lead

tetraborate glasses. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 2005; 62: 761. [7] Duan XL et al. Optical Absorption of Co2+-Doped Silica Gel-Derived Glasses. Optical Materials 2003; 23: 327. [8] Kumar GA, De la Rosa E and Desirena H. Radiative and non radiative spectroscopic properties of Er3+ ion in tellurite glass.

Optics Communications 2006; 260: 601. [9] Ye CC, Hewak DW, Hempstead M, Samson BN and Payne DN. Spectral properties of Er3+-doped gallium lanthanum

sulphide glass. J. Non-Crystalline Solids 1996; 208: 56. [10] Kassab LRP, de Oliveira Preto A, Lozano W, de Sa FX and Maciel GS. Optical properties and infrared-to-visible

upconversion in Er3+- doped GeO2-Bi2O3 and GeO2-PbO-Bi2O3 glasses. J. Non-Crystalline Solids 2005; 351: 3468. [11] Venkateswara Rao G and Veeraiah N. Study on certain physical properties of R2O-CaF2-B2O3:Cr2O3 glasses. J. Alloys and

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Utilization of rice husk fly ash in the color glass production