Production, characterization, activation and environmental applications of engineered biochar: a review

Increased industrial and domestic activities have induced pollution, global warming and resources depletion, calling for advanced remediation techniques. For instance, biochar synthesized from waste materials is an ecofriendly and low-cost material for the remediation of contaminants, yet raw biochar is poorly efficient. Therefore, biochar properties can be improved by ultrasonication, metal impregnation, surfactant modification, microwave, electrochemical and plasma treatment techniques. Biochar properties include adsorption capacity, active surface area, uniform distribution of pores, chemical attributes and mechanical stability. Engineered biochar thus exhibits high contaminant removal efficiency of 90–99%, tolerance to wide range of pH of 3–9 and high specific surface area of more than 400 cm3/g. For example, modified cornstalk biochar displays mercury adsorption capacity of 269.4 mg/g. The usage of magnetic biochar allows a β-estradiol adsorption capacity of 98.8 mg/g. Engineered biochar can act as an ecofriendly soil amendment and a highly efficient tool to recover contaminants from water systems.