Porous adsorbents derived from coal fly ash as cost-effective and environmentally-friendly sources of aluminosilicate for sequestration of aqueous and gaseous pollutants: A review

Coal fly ash (CFA) is an industrial by-product generated during coal combustion process in power plants. Due to its chemical and mineralogical composition, CFA is considered as an abundant and cheap source of aluminosilicate to produce valuable advanced materials, such as zeolites, catalysts, photocatalyts, and geopolymers, with high adsorption capacity towards pollutants. In this review, the preparation methods and characterization of CFA-based adsorbents, as well as their application in removing aqueous pollutants, such as petroleum compounds, dyes, heavy metals, radioactive contaminants, COD and SS, and gaseous pollutants, such as carbon dioxide, sulfur dioxide, sulfuric acid, hydrogen sulfide, mercury, nitric oxide, benzene, toluene, and o- and p-xylene were summarized. The studies prove CFA-based adsorbents to be efficient and cost-effective alternatives to remove aqueous and gaseous pollutants. Recent investigations on the application of various surface modification techniques to improve the adsorption capacity of CFA-based adsorbents were also covered. The results indicate higher adsorption capacity of CFA-based adsorbents compared to raw CFA after surface modification. (C) 2018 Elsevier Ltd. All rights reserved.