Investigation on Utilization of Sodium Silicate Synthesized from Agricultural Waste as a Dispersant in Clay-Based Slip for Ceramic Production

Abstract

Thailand is the world’s largest rice exporter, tend to continuous increasing the agricultural waste. Burning, to eliminate an agricultural waste, pollutes the air with CO and CO₂ emissions which is considered by many in the science community to be a cause of global warming. However, the calcined agricultural waste with the optimum temperature, results in a rich source of active-SiO₂. Active-SiO₂ was reacted with sodium hydroxide (NaOH) to form sodium silicate (Na₂SiO₃), called as waterglass or soluble glass. Therefore, sodium silicate is often used as a deflocculant in clay-based ceramic slip production to reduce viscosity instead of adding large amounts of water. In this work, rice straw and rice husk are an agricultural waste and used as a starting material. Before used, the reaction temperature of agricultural waste is checked by using DTA-TGA technique. The waste was first calcined at 600 °C for 2 h in air to remove organic matter and produce high purity of active-SiO₂. This was then added to NaOH as the starting material for Na₂SiO₃ synthesis. Then used synthesized Na₂SiO₃ as a dispersant in clay-based ceramic slip. The phase, viscosity, porosity, and particle arrangement were tested and compared with commercial grade of Na₂SiO₃. Sodium silicate from agricultural waste exhibited high-performance deflocculant behavior, with reduced viscosity and water demand of clay minerals. Card pack particle arrangement resulted in increased density and low porosity, and directly endowed the ceramic products with high strength. For reducing waste and environmental impact, the result suggested that sodium silicate produced from agricultural waste, can be utilized as a promising and alternative natural deflocculant to clay-based ceramic slip in the ceramic manufacturing process to decrease production costs.

Keywords:

• Deflocculant agent
• Husk ash
• slip casting
• ceramic processing
• waste management

Acknowledgments

This work did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. I also thank Suranaree University of Technology (SUT) for facilitating the development of part of the research in our work.