Waste materials for wastewater treatment and waste adsorbents for biofuel and cement supplement applications: A critical review

A pragmatic shift is ongoing in waste material management and wastewater treatment technology due to the large amount of waste production worldwide and the necessity for cheap adsorbents to reduce wastewater treatment costs. Improvements in the circular economy and energy recovery from waste materials is another fast-growing concept for promoting sustainability and a greener environment. This review study endeavours to integrate the concept of wastewater treatment by waste materials (agricultural residue, industrial and municipal waste, organic and inorganic sources) and utilization of the used waste adsorbents for value-added products through further treatment. Although very few experimental studies were performed on this concept, this study summarizes the potential valuable products such as regenerated adsorbents, biofuel, soil amendment supplements and cementitious material by utilizing waste adsorbent. Production mechanisms of valuable products is discussed comprehensively. This review also documents the major emerging contaminants, the diverse waste materials as potential adsorbent candidates and conversion processes from waste into adsorbents. The outcome of this review promotes the utilization of waste into multiple useful products generation which may improve waste management and boost the circular economy. The integrated applications of this review describe the commercial window available to accumulate waste materials for large scale applications. Further, sources of energy and nutrients extracted from waste materials after treating polluted water in industries, municipal units and animal husbandries can be a significant contributor to commercial viability in the future. (C) 2020 Elsevier Ltd. All rights reserved.