Oxidative degradation of tetracycline using persulfate activated by N and Cu codoped biochar

[Display omitted] •N and Cu codoped biochar was prepared and showed great performance for tetracycline degradation.•The urchin-like copper could provide abundant active sites for catalytic reaction.•The dominant free radical in the N&Cu-C/PS system was HO.•The electron transfer mechanism of the nonradical pathway has been confirmed. A nitrogen and copper codoped biochar (N-Cu/biochar) material was prepared and used to activate persulfate (PS) for tetracycline (TC) degradation. The material was characterized by SEM, FT-IR, XRD and XPS. The results showed that the N-Cu/biochar had a flaky carbon structure with urchin-like copper growing on the carbon surface, a large specific surface area of 352.43 m2/g that provided sufficient active sites for catalytic reaction, and abundant functional groups. Quenching experiments and electron paramagnetic resonance (EPR) experiments verified the reaction pathway mechanisms. The main free radical in the system was HO; another possible mechanism is the nonradical pathway of electron transfer between TC and PS on the surface of the catalyst, and this electron transfer could lead to TC degradation. All the TC was removed within 120 min at a catalyst dosage of 200 mg/L, PS dosage of 0.5 mM, and pH of 7.0. Chloride and bicarbonate ions had little effect on the degradation of TC. HPLC-MS was used to investigate the main degradation intermediates and the possible transformation pathways were proposed. The toxicity of TC and its intermediates were evaluated by bioluminescence inhibition method. The high catalytic efficiency and low consumables of the N-Cu/biochar/PS system could provide a new strategy for the remediation of wastewater.