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I.

INTRODUCTION

In this paper, I will explain some alternative raw materials in production of SLS glass. Firstly, I will briefly mention the SLS glass composition and typical materials that are used in production of them as an introduction. Then, I will explain the necessity of using alternative materials in production of SLS glasses. After mentioned these, I will explain the alternative raw materials and their impacts by referring some research in literature. Alternative raw materials that I explain in this paper are biomass ash, eggshells, seashells, rice husk and grass ash. Finally, I will conclude the paper with conclusion part. 1. SLS Glasses Soda lime glasses also called SLS glass use for window, food, beverage, bottles, and jars today. At the same time, soda-lime glass constitutes approximately 85% -90% of the total glass produced. [1][2] Soda lime glass is cheap compared to other glasses. It is stable in chemical structure and has good hardness. SLS glass generally consists of SiO2 (approximately 70%), soda (approximately 15%), lime (approximately 9%) and various compounds [3]. It is a transparent material produced by melting and cooling these compounds such as sand (SiO2), soda ash (Na2CO3), limestone (CaCO3) and dolomite (CaMg (CO3) 2) and alumina (Al2O3). Melting temperature is very high. It is about 15001600 degrees. [8] At that point, I will briefly mention the generally features of each components of glass to identify its typical formation. Each compound within glass system is very important. Silica (SiO2) is a glass former. However, silica melts approximately 1700-1800. This is a very high temperature. These types of pure silica glasses badly affect most glass applications economically. Therefore, alternative raw materials are investigated to reduce this feature of Silica. ‘’Soda (Na2O) is a flux. Adding soda to the system will greatly reduce the melting temperature of the silica melt. In addition, the addition of soda increases the water solubility of the glass obtained. Lime (CaO) is a stabilizer. The addition of small amounts of lime stabilizes the glass melt with respect to water by solving the water solubility problem associated with the soda component. 1

Many metal oxides can be added to silica solutions to add different properties to the glass obtained.’’[9] 2. The Necessity of Using Alternative Materials I will mention two necessity of using alternative materials like preventing environmental pollutions and providing sustainable way of production. Today, carbon dioxide emission due to environmental pollution is at a very important point. Such alternative raw materials are needed to protect the earth and the atmosphere, to reduce environmental pollution and for a sustainable life. Also, alternative raw materials are needed in order to enable lower furnace operating temperatures, i.e. to reduce energy consumption, thus reducing CO2 and Thermal NOx emissions. Moreover, the glass industry extracts sand from seashore and riverbeds. This causes a deterioration in the ecology of marine creatures and other organisms. Alternative raw materials are needed to overcome this situation. For example, rice husk ash can be used instead of silica to prevent sand erosion. Using alternative raw materials are important point in sustainable glass production. For example, the content of GlassTrend Seminar 2020 is about “Innovative raw materials and processing technologies for sustainable glass production”. In this seminar, innovative raw materials and recycling technologies were mentioned. [4][6][13] II.

ALTERNATIVE RAW MATERIALS AND THEIR IMPACTS

It has been considering previously that using agricultural and industrial wastes to produce glass. In other words, using ashes of the organic materials as an alternative in the production of glass is not a new issue. For example, in Medieval Germany, they used the wood ashes like fluxes in glass and named it as Forest Glass. But usage of such raw materials in glass industry has not been common until recent years. However, today, with the awareness and consideration of sustainable glass production aspects, using alternative raw materials has gained importance. Because researchers think that these wastes have significant potential of contributions to reduce energy consumption and enable more sustainable glass production. However, these alternative waste materials should be evaluated in terms of their chemical compositions and mineral content to determine whether they are suitable for producing glass or not.

Therefore, in this paper, some discussions regarding investigating potential

alternative raw materials for glass production will be examined. [4] The alternative raw materials that are examined in this paper are biomass ash, eggshells, seashells, rice husk and grass ash. Moreover, the impacts of these potential alternative raw materials on production of glass will be discussed in discussion part. 1. Biomass ash

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Using biomass to power generation gains importance with the increasing of environmental concerns. Therefore, these biomass power plants produce a significant number of ashes in each year. Researchers have analysed these ashes whether they could be an alternative raw material for glass production or not. At the end of the analyses, they found that biomass ashes contain useful and suitable alkali metals like K, Na, Mg and, Ca for SLS glass production. While comparing other raw materials, biomass ashes compositions are complex, and it is difficult to recycle for glass ram materials [6]. Biomass ash materials has characteristic effects on final glass quality. For example, glass color will be affected. 2. Seashell Another alternative raw material can be seashells to produce SLS glass. The increasing of amount of seashell wastes produced by seashell industries direct people to use these wastes in new applications like glass making. Because these wastes consist rich calcium, so they are considering as an alternative source of calcium carbonate. Seashells can be used by replacing limestone in SLS glass production. Although studies show that using seashells in production of SLS glasses is not high-value application, it provides effectiveness, resource efficiency and reuse of wastes. Seashells contain more than 98 wt% calcium oxide, so they are the alternative source of CaO. [6] 3. Eggshells Eggshells wastes are rich in terms of calcium carbonates, magnesium, and protein. Therefore, eggshells could be considered as an alternative material of limestone in production of SLS glass. Like seashells, eggshells also could be alternative source of CaO because of containing 98 wt% calcium oxide [6]. Eggshells have impact on color of glasses. Although pure SLS glass is colorless and transparent, eggshells cause to dark green color in samples. As seen in Figure 1, the color of produced glass is darker with increasing weigh of eggshells [11].

Figure 1- Glasses that are produced by using wt%1, wt%3 and wt%5 eggshells (ES) (Source: [11])

4. Rice husk Potential usage of rice husk in glass making is reported by Kaewkhao and Limsuwan [5]. Rice husk ashes have potential for a pure and lower energy consumption due to contain approximately 95 wt% is SiO2. Therefore, it could be an alternative source of SiO2 in glass production. On the other hand, the result of XRF studies claim that rice husk ashes include some materials that are not currently exist in SLS glass compositions like phosphate and 3

chloride. Sometimes volatile features of chloride may cause to rise corrosion of furnace refractories. Also, uncontrolled phosphate in production of SLS glass can cause to phosphate levels are above approximately 1.5 wt%. Also, iron and manganese amount of rice husk ashes cause to coloration of produced samples. The left samples in Figure 2 shows the glass with pure rice husk ash. Studies show that adding 0.5 mol% of Sb2O3 reduce amount of magnesium and colorless glass is obtained [12].

Figure 2- Glasses that are produced by Rice husk ashes. (Source: [12])

5. Grass ash According to a study, using recycled grass ashes (obtained from Pennisetum purpureumElephant Grass) can be a useful and alternative choice in glass production. Grass ashes contain significant amount of SiO2, K2O and CaO, so these ashes which consist of silica of >30 wt% are used instead of SiO2 material in glass composition. Also, B2O3 and Na2O added to grass ashes to be successful in glass production. The glass which is produced by using grass ashes show colourless features. [7] III.

CONCLUSIONS

To conclude, in this paper alternative raw materials that can be used for glass production are mentioned. Especially, the industrial and organic wastes considered as alternative raw materials into glass manufacture. According to studies, seashells, eggshells, biomass ashes, rice husk ashes and grass ashes are represented as alternative materials in glass production. As seen in Table 1, Seashells and Eggshells are used instead of CaO in glass composition because of containing high amount of CaO. Moreover, Biamass ashes, Rice husk ashes and Grass ashes are used instead of SiO2 in glass composition because of containing high amount of SiO2. Table 1: Composition (weight %) of alternative raw waste materials (synthesized and analysed by author based on [6] and [10])

Wt% SiO2 Al2O

Alternative raw materials used instead of CaO Seashells Eggshells 0.34 0.15

Alternative raw materials used instead of SiO2 Rice Husk Ash Grass Ash

Biomass ash 0.00 39.13 0.00 18.17 4

95.05 0.00

79.24 3.59

3 Na2O CaO K2O

0.54 98.30 0.00

0.31 98.43 0.12

1.46 14.55 8.87

0.19 097 1.15

0.00 12.17 12.07

All alternative raw materials impact some features of final glass product in terms of melting temperature, color etc. But adding some materials enable to obtain typical SLS glass. To sum up, there are potential opportunities to reduce energy consumption, prevent environmental pollution and develop waste treatment by using these waste ashes in glass production. Therefore, using alternative raw materials is important to provide sustainable way of production. IV. REFERENCES [1] Rayotek News, (n.d.), Borosilicate Glass vs. Soda Lime Glass? Retrieved 10.01.2021 from https://rayotek.com/wpnews/borosilicate-glass-vs-soda-lime-glass/ [2] Robertson, Gordon L. (2005). Food Packaging: Principles and Practice (Second ed.). CRC Press. ISBN 978-0-8493-3775-8. [3] Congcal, (n.d.), Calcium Carbonate - Glass Manufacturing.Retrieved 09.01.2021 from https://www.congcal.com/markets/glass/. [4] Murray Edward College. (2019). Biomass Ash: A Past and Future Raw Material for Glass-Making? Retrieved January 10, 2021, from Society of Glass Technology Annual Conference website: https://cambridge2019.sgt.org/ab-sc-danielbackhouse [5] Kaewkhao J, Limsuwan P. Utilization of rice husk fly ash in the color glass production. Proc Eng. 2012;32:670–5. [6] Deng, W., Spathi, C., Coulbeck, T., Erhan, K., Backhouse, D., Marshall, M.,Bingham, P. A. (2020). Exploratory research in alternative raw material sources and reformulation for industrial soda-limesilica glass batches. International Journal of Applied Glass Science, 11(2), 340–356. https://doi.org/10.1111/ijag.14775 [7] Srisittipokakun, N., Kirdsiri, K., Ruangtaweep, Y., & Kaewkhao, J. (2013). Utilization of Pennisetum purpureum ash for use in glass material. Advanced Materials Research, 770(September), 84–87. https://doi.org/10.4028/www.scientific.net/AMR.770.84 [8] Burchard. F. Ernest. “The Requirements of Sand and Limestone for Glass Making”. pp. 452- 475 [9] Lockwood, G. K. (n.d.). Glass Compositions. Retrieved January https://www.glennklockwood.com/materials-science/glass-compositions.html

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[10] Soriano, L., Jr, H. S., Santamarina, P., Akasaki, J. L., & Solteira, I. (n.d.). Microscopic and Chemical Characterization of Elephant Grass and Corn Leaves and Their Ashes. [11] Aktas, B., Albaskara, M., Yalcin, S., & Dogru, K. (2017). Optical properties of soda-lime-silica glasses doped with eggshell powder. Acta Physica Polonica A, 132(3), 442–444. https://doi.org/10.12693/APhysPolA.132.442 [12] Gonçalves, J., da Silva, G., Lima, L., Morgado, D., Nalin, M., Armas, L. E. G., … Menezes, J. W. (2020). Production of Transparent Soda-Lime Glass from Rice Husk Containing Iron and Manganese Impurities. Ceramics, 3(4), 494–506. https://doi.org/10.3390/ceramics3040040 [13] GlassTrend Seminar 2020 : “ Innovative raw materials and processing technologies for sustainable glass production .” 1–5.

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