A novel low temperature synthesis of sodium silicate (water glass) from silica-rich wastes using hydrothermal method

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 110oC 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 800oC 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 150oC, 170oC and 200oC 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 SiO2/Na2O ratio showed they are commercial sodium disilicates which indicates the products are all sodium silicate solutions.