A new application pattern for sludge-derived biochar adsorbent: Ideal persulfate activator for the high-efficiency mineralization of pollutants

Highlights: • The proposed biochar adsorbent with large surface area promotes PS activation. • Desired mineralization efficiency is achieved by the small dosage of PS and biochar. • Toxicity of the biochar/PS catalytic system is relatively low with eco-friendliness. • Most important active species [SBC-PS*] is verified by FT-IR and Raman spectra. • Active sites for PS activation and pollutant degradation are systematically explored. Via enlarging the specific surface area of sludge biochar to enhance the close contact of multiple reactants may be a simple route to improve the catalytic performance with reduced dosage of biochar and oxidant, benefitting for cost-effectiveness and eco-friendliness. Herein, PS activation ability of a reported sludge-derived biochar adsorbent was investigated. 80% TOC of 100 mL 10 mg/L BPA was removed within 40 min by 7 mg biochar and 0.5 mM PS mixed, with a relatively high PS activation efficiency close to 50%. Expectedly, the desired mineralization efficiency of complex actual wastewater was also identified. Eco-friendliness of the application mode was confirmed by the leaching toxicity and acute bio-toxicity tests. Physicochemical properties of the sludge biochar were comprehensively characterized by various techniques. Combined with a series of mechanism analysis, ·OH, SO₄·^-, ·O₂^-, ¹O₂, free electron all participated in pollutants removal process and the non-radical pathway of electron transfer dominated the reaction. The generated metastable complex [SBC-PS*] confirmed by in situ FT-IR and Raman spectra was the most important active species for electron transfer and PS decomposition. Due to the high efficiency and stability, the sludge biochar adsorbent/PS catalytic system provides a promising way for waste reuse and advanced wastewater treatment.