A Novel Low Temperature Synthesis of Sodium Silicate (Water Glass) from Silica-Rich Wastes using Hydrothermal Method

Abstract

This present work aims at synthesizing sodium silicate solutions from selected industrial wastes (waste glass and rice husks) using hydrothermal method. The as-received waste glasses of different mix colors were initially washed, crushed and wet milled for several hours then sieved through 75µm mesh. The sieved recycled glasses were then oven dried at 110 o C for 72 h to obtain a powdered glass (SLSG). Rice husks were also washed to remove dirt adherence and dried. The dried rice husks were thermally treated in a muffle furnace at 800 o C for 1 h then left to cool to obtain whitish rice husk ash (RHA). Both SLSG and RHA were then reacted with NaOH solution at varying concentration of 3M, 4M and 5M respectively in a 250 ml Erlenmeyer flask. The mixtures were heated with continuous stirring using a magnetic stirrer at temperatures of 150 o C, 170 o C and 200 o C respectively for a reaction period of 4 h. Analyses were carried out on the synthesized sodium silicate solutions. The results obtained from the analyses showed sodium silicate synthesized from RHA possessed high viscosity while the SiO 2 /Na 2 O ratio showed they are commercial sodium disilicates which indicates the products are all sodium silicate solutions.

Justification of an acceptable modern energy-efficient method of obtaining sodium silicate for production in Kazakhstan

“…This method is very attractive for practical implementation due to the low cost [14]. Due to the presence of a high content of unreacted silicon oxide, liquid glass, which is obtained by further dissolution of sodium silicate, contains a large amount of insoluble residue unacceptable by any standards, which, in principle, could be eliminated by conventional filtration, but, apparently, this method has not found practical application for reasons of production safety [15].…”