Recent advances on biochar-derived materials for photodegradation of pharmaceuticals in wastewater

The bio-recalcitrant nature of pharmaceuticals in wastewater has been a challenge due to the inability of conventional treatment systems to remove them, warranting the use of advanced oxidation techniques with carbon-derived materials. This is owed to the role of photodegradation in breaking organic waste without leading to secondary pollution. This study, therefore, aimed to explore existing knowledge related to biochar-derived photocatalyst materials and their applications in pharmaceuticals. The review addressed the treatment process and the limitations of using pristine catalysts such as high band gap energy, recombination of electron/hole ( e - /h + ) pairs, and low dispersity in solutions. The review showed doping, coupling, decorating, and supporting pristine photocatalyst with biochar resulted in reduced band gap energy, and improved stability, dispersion, and separation of photogenerated e - /h + pairs. These modifications also enhance visible light absorption, and generation of superoxide and hydroxyl radicals that are used for degradation of pharmaceuticals. Therefore, the review established synthesis procedures, types, characterisations, and applications of biochar-derived materials. The synthesised materials demonstrated improved synergistic adsorption-photodegradation efficacies in biochar-derived photocatalysts as compared to pristine counterparts. Finally, the study examined the impact of various operational parameters and the emerging applications of biochar-derived materials. Moreover, the study proposes different prospects for the research frontiers which include pursuit of binary and ternary pollutants in solution and testing the materials against real wastewater.