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As the by-product of wastewater treatment, a large amount of sludge is generated annually. Turning this waste into a resource is a feasible and sustainable strategy to reduce potential environmental risks and recover energy. As a way to realize the international goal of carbon dioxide emission peak and carbon neutrality, producing biochar from sludge has gained worldwide attention. This review evaluates recent progress in synthesis techniques for biochar of sludge origin. Different preparation techniques and their key affecting factors are compared and described. The obtained sludge-derived biochar could be employed for eliminating aqueous pollution or purifying wastewater, mainly through adsorption and catalytic reactions. The removal of various pollutants by sludge-derived biochar and its related mechanisms are discussed and summarized in detail. This review will be conducive for a comprehensive understanding of recent progress in sludge-derived biochar study and for guiding the purposeful production of biochar, as well as for developing wastewater purification technology based on sludge-derived biochar. [ABSTRACT FROM AUTHOR]

Metal nitrogen carbon (MNC)-based Fenton reactions leveraged with robust peroxymonosulfate (PMS) interaction effectively guarantee the elimination of refractory contaminants, yet the precise design of local microenvironment of MNC to couple with the multiple PMS activation pose major challenges. Herein, a porous Co single-atom catalyst (SAC) with nitrogen defects (N v ) (MCo/NC-6) is fabricated to initiate PMS oxidation reaction. The weaker but richer coordination between Co and N in the precursor facilitates the formation of N v and porous structure during pyrolysis, achieving simultaneously electronic structure and spatial distribution tuning. Compared with the Co SAC (ZCo/NC-6), the optimized MCo/NC-6 significantly increase the bisphenol A (BPA) reactivity (k = 0.63 min -1 ), PMS utilization (78%), and singlet oxygen ( 1 O 2 ) yield (100%) by 15.3, 2.4, and 2.6 times, respectively. Experimental analyses and theoretical calculations reveal that the Co─N─C coordination regulated by both micro space and neighboring N v is endowed high-mobility electrons, thus synergistically facilitating rapid generation and efficient utilization of 1 O 2 . This work promises new opportunities for the design of local microenvironments-regulated SACs, and charts new trajectories in complex Fenton-like systems., (© 2024 Wiley‐VCH GmbH.)