The Environmental Friendly Route to Obtain Sodium Silicate Solution from Rice Husk Ash: A Comparative Study with Commercial Silicates Deflocculating Agents

Abstract

Sodium silicate solutions were synthesized treating Rice Husk Ash (RHA) with sodium hydroxide solutions at low molar concentrations (1–4 M). During the study the operative conditions were optimized. Raman spectroscopy was used to check the chemical nature of the silicates solutions obtained by comparison with commercial ones. The deflocculating efficiency of the synthesized solutions was checked by rheological measures on clay suspensions (solid content 60 and 65 wt%). Some findings of the study permit to confirm that the extraction of SiO2 increases by increasing NaOH concentration. The alkaline attack (NaOH solution) at 1.5 and 2 M show the best results for SiO2/Na2O ratio close to 2, this ratio is widely used as deflocculating agents in ceramic sector using commercial silicates. The 0.5wt% content resulted the optimum dosage for all additives. In particular, the viscosity values obtained using the silicates synthetized from RHA are lower than those corresponding to the commercial products. The deflocculating capability behaves similar, or even better, than commercial ones. This valorization of matter from RHA allows the obtainment of high added value products that can play role of “green” substitutes of commercial ones.