The Environmental Friendly Route to Obtain Sodium Silicate Solution from Rice Husk Ash: A Comparative Study with Commerc
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ORIGINAL PAPER
The Environmental Friendly Route to Obtain Sodium Silicate Solution from Rice Husk Ash: A Comparative Study with Commercial Silicates Deflocculating Agents Fernanda Andreola1 · Luisa Barbieri1 · Isabella Lancellotti1 Received: 2 May 2019 / Accepted: 16 October 2019 © Springer Nature B.V. 2019
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. Graphic Abstract
RHA Soluon NaOH 1M, 1.5M, 2M, 3M,4M
Tritraon by HCl 1M
Separaon of soluble silicates by Filtraon
Raman
Deflocculang capability tests by Rotaonal Reometry
XRD SEM/EDS
Keywords Silicates · Deflocculants · Rice ask ash (RHA) · Rheological properties · Recycling Extended author information available on the last page of the article
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Statement of Novelty The RHA was used as amorphous silica source, this fact permits a better extraction with respect to crystalline silica; Current industrial processes work at high temperatures (1400–1500 °C) and pressures, here an environmental friendly route, where the operative conditions are: temperature < 100 °C and atmospheric pressure; The valorization of RHA in the deflocculation field is a very high added value utilization; The performance of deflocculants obtained from RHA behaves similar, or even better, than commercial ones for the ceramic processing.
Introduction Rice husk (RH) is a food by-product commonly employed in rice producing Countries as biomass for green energy production. The solid residue of the combustion process is a particular kind of ash, the rice husk ash (RHA). About 18–20 wt% of the RH is converted to RHA after incineration. Thanks to its high content in amorphous silica (83–90%), RHA doesn’t need to be disposed of in landfill and can be instead exploited as low-cost precursor for the production of high-value silica based materials. Indeed, amorphous silica from con
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