Production, properties, and catalytic applications of sludge derived biochar for environmental remediation

•Sludge components and dewatering methods impact the properties of biochar.•Thermochemical methods influence the characteristics of sludge biochar.•The mechanisms and removal performance of pollutants by biochar are introduced.•High-temperature carbonized sludge biochar exhibits excellent performance.•This review offers a sustainablewayof sludge reutilizationfor water purification. Environment-friendly and cost-effective disposal and reutilization of sludge wastes are essential in wastewater treatment processes (WWTPs). Converting activated sludge into biochar via thermochemical treatment is a promising technology for waste management in WWTPs. This review summarizes the compositions of sludge, the dewatering methods, and the thermochemical methods whichinfluence the structures, chemistry, and catalytic performances of the derived biochar. Moreover, the physiochemical characteristics and chemical stability of sludge biochar are discussed. Catalytic applications of biochar are highlighted, including the reaction mechanisms and feasibility for catalytic removal of organic contaminants. High-temperature carbonized sludge biochar exhibits excellent performance for persulfate activation in advanced oxidation processes due to the graphitic carbon structure, newly-created active sites, and fine-tuned metal species. Therefore, the sludge biochar can be produced via cost-effective and eco-friendly approaches to immobilize harmful components from sludge and remediate organic pollution in wastewater, offering a sustainable route toward sludge reutilization into value-added products for water purification. [Display omitted]