LAUSR

Solidification/stabilization (S/S) of hazardous waste using cement for immobilization of contaminants has been recognized as Best Demonstrated Available Technology (BDAT) by the United States Environmental Protection Agency, which has been practiced in India too. However, the growing concerns over the environmental impacts and carbon footprints of cement production have inspired the waste managers and policymakers to develop and support more sustainable binders for S/S. The present study aims at exploring the potential of waste-derived geopolymers to be used in the treatment of hazardous wastes generated from industrial operations using S/S technology with a special focus on Indian waste management scenario. The present study presents a literature review on the use of certain kinds of industrial waste as the so-called “green binders” by combining sodium silicate and alkalis such as sodium hydroxide or potassium hydroxide by the process of geopolymerization. Such green binders are typically fly ash, ground granulated blast furnace slag (GGBS), rice husk ash, kaolin and metakaolin, which has better environmental acceptance and considered as more sustainable when compared with convention binders. The binder materials can potentially be used as an alternative to cement, which will reduce greenhouse gas emissions in cement production and reduce the energy requirement in the cement industry (minimization of carbon footprints). Additionally, the ashes produced from the coal-fired thermal power plant and other industries should be put to gainful use, and thereby, costs for treatment and disposal of waste can be minimized. Various studies have been reported in the literature that fly ash-based geopolymers can be effectively employed to immobilize heavy metals in industrial sludges and incinerator ashes containing Pb, Ni, Zn Mn, and Cr, because geopolymers create chemical bonds, thereby causes physical encapsulation. It is hoped that this green binder would minimize not only the environmental burden of fly ash generated from the thermal power plants in India but also produce the so-called refuse-derived green construction products. Reportedly, out of the total of 9.44 million tonnes of hazardous waste generated per year in India, nearly 38% is landfillable waste. The landfillable waste needs to be treated before its final disposal into the secured landfills to immobilize the hazardous contaminants and remove the moisture. For this purpose, according to the estimates made in this study, nearly 897,000 tonnes of cement is needed for S/S of hazardous waste which can be saved by replacing it with sustainable binders called geopolymers.