A comprehensive review of biochar in removal of organic pollutants from wastewater: Characterization, toxicity, activation/functionalization and influencing treatment factors

Abstract

The current climate and environmental challenges demand novel and cost-effective sustainable materials with a high efficacy and eco-friendly properties. Biochar (BC) has gathered a great interest in the last years across different research fields, thanks to its special physicochemical characteristics such as high specific surface area, high porosity, ion exchange capacity and because of scientific evidence in removing various contaminants from soil, water, and air. This review aims to give the state of the art on the removal of toxic organic pollutants from wastewater using biochar, activated biochar, functionalized biochar and metal oxide or clay base biochar composites, commenting on the substrates' physiochemical properties, the role of the most used characterization techniques toxicity, activation/functionalization and influencing treatment factors in organic pollutant removal from wastewater. The effect of different operating parameters of the water treatment process is summarized and thoroughly discussed. The toxicity of biochar components such as heavy metals, dioxins and polycyclic aromatic hydrocarbons (PAHs) is addressed. The various application processes of biochar in water treatment at both laboratory and pilot scale is also reviewed. The activation techniques, functionalization pathways and biochar based-nanocomposite synthesis methods for enhancing the pollutant elimination efficiency are also extensively discussed. Finally, the paper suggests research directions in the field of biochar application in wastewater treatment.