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Removal of tetracycline antibiotics (TCs) by biochar adsorption is emerging as a costeffective and environmentally friendly strategy. This study developed a novel pomelo peel derived biochar, which was prepared at 400 °C (BC-400) and 600 °C (BC-600) under nitrogen conditions. To enhance the adsorption capacity, BC-400 was further activated by KOH at 600 °C with a KOH: BC-400 ratio of 4:1. The activated biochar (BC-KOH) displayed a much larger surface area (2457.37 m 2 /g) and total pore volume (1.14 cm 3 /g) than BC-400 and BC-600. High adsorption capacity of BC-KOH was achieved for removing tetracycline (476.19 mg/g), oxytetracycline (407.5 mg/g) and chlortetracycline (555.56 mg/g) simultaneously at 313.15 K, which was comparable with other biochars derived from agricultural wastes reported previously. The adsorption data could be fitted by the pseudosecond-order kinetic model and Langmuir isotherm model successfully. The initial solution pH indicated the potential influence of TCs adsorption capacity on BC-KOH. These results suggest that pore filling, electrostatic interaction and π-π interactions between the adsorbent and adsorbate may constitute the main adsorption mechanism. BC-KOH can be used as a potential adsorbent for removing TCs from swine wastewater effectively, cheaply and in an environmentally friendly way.

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Resistant pollutants like oil, grease, pharmaceuticals, pesticides, and plastics in wastewater are difficult to be degraded by traditional activated sludge methods. These pollutants are prevalent, posing a great threat to aquatic environments and organisms since they are toxic, resistant to natural biodegradation, and create other serious problems. As a high-efficiency biocatalyst, enzymes are proposed for the treatment of these resistant pollutants. This review focused on the roles and applications of enzymes in wastewater treatment. It discusses the influence of enzyme types and their sources, enzymatic processes in resistant pollutants remediation, identification and ecotoxicity assay of enzymatic transformation products, and typically employed enzymatic wastewater treatment systems.Perspectives on the major challenges and feasible future research directions of enzyme-based wastewater treatment are also proposed.

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