The Effect of Decolorizing Agent on the Optical Properties of High Iron Contents Soda-Lime Silicate Glass

Abstract:

The aim of this study is to decolorize the high iron content (more than 0.1 %wt Fe₂O₃) glass. The contained 0.13 wt% iron oxide (Fe₂O₃) soda-lime silicate is prepared by high iron content sand with 0.17 wt% of Fe₂O₃. Iron oxide in soda-lime glass presents in two forms, Fe²⁺ (green) « Fe³⁺ (yellow). In principle, high iron content sand is not suitable to produce tableware. Therefore, the glass manufactures require high purity of sand because they want to control the amount of iron oxide as low as possible, which usually tableware glass contains only small amount of iron oxide (0.01 - 0.04 wt% Fe₂O₃) to avoid iron effect (green color). The soda-lime silicate glasses is decolorized by three different agents, Neodymium oxide (Nd₂O₃), Manganese oxide (MnO₂), and Tin oxide (SnO₂) 0.125 0.25 0.50 1.00 and 2.00 %wt respectively. The glasses are melted twice in the platinum crucible and investigated of the optical properties by UV-Vis spectrophotometer. The results of the color in CIE L*a*b* system are found that glass containing MnO₂ and SnO₂ slightly changes to white shade, but still presents in green. However, the result of contained 1.00 and 2.00 %wt SnO₂ glasses is nearly cleared, the result of contained Nd₂O₃ glasses are satisfied, and the contained 0.25 %wt Nd₂O₃ glass is showed very clear. Anywise the color of glasses containing 1.00 and 2.00 %wt Nd₂O₃ turned to blue. The reaction of glasses containing Mn and Sn occur according to the mechanism of chemical decolorization. The reactions was described by the following equation, Fe²⁺ + Mn³⁺ g Fe³⁺ + Mn²⁺ and Fe²⁺ + Sn⁵⁺ f Fe³⁺ + Sn⁴⁺, but the reactions are limited and strongly depending on the redox equilibrium. For Nd₂O_3, the reaction presents according to physical decolorization, because the color of Nd₂O₃ is stable in melted glass and it can dismissed the color of Fe₂O₃ directly. Therefore, this method can apply for the tableware glass production with high iron content sand.

• Periodical: Key Engineering Materials (Volume 766)
• Pages: 28-33
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.766.28
• Online since: April 2018
• Authors: Ekarat Meechoowas*, Benjamon Petchareanmongkol, Parida Jampeerung, Kanit Tapasa
• Keywords: Decolorizing Agents, High Iron Content Sand, Soda-Lime Silicate Glass

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