The state-of-the-art development of biochar based photocatalyst for removal of various organic pollutants in wastewater

The use of biochar (BC) as a substrate and dopant in developing composite biochar-based photocatalysts (BBP) has proven to be highly promising in advancing wastewater treatment technology. This review focuses on the development of BBP using agricultural and poultry waste-derived BC to mitigate organic pollutants in water, with emphasis on the synthesis technique employed for the preparation of various BBP. Various techniques for preparing BC and BBP, along with its features and physico-chemical properties, are discussed in detail. The review then delves into the role of BC in influencing the inherent properties of the BBP, particularly in reducing band gap, acting as an electron sink or reservoir, increasing surface active regions, and improving charge separation. Furthermore, the review outlines the synergistic improvement brought about by BC in BBP, specifically in terms of the photodegradation of different classes of pollutants, i.e. pharmaceutical waste, dye from the textile industry, and phenolic compounds. Lastly, the crucial challenges associated with the practical employment of BBP in real-time applications, such as scaling up, long-term stability, and retrofitting into existing wastewater remediation technologies are elaborated. This review will provide significant insights for readers evaluating the sources of BC used as substrates and the methods employed to develop efficient BBP for the remediation of various organic pollutants.