Boosting persulfate activation via paper mill sludge-based biochar for efficient degradation of bisphenol A: Inherent multiple active sites

Paper mill sludge generated from the pulp and papermaking industries has inherent iron and carbon contents. Herein, the biochar derived from paper mill sludge (PSBC) was synthesized via simple pyrolysis processes and applied as an efficient persulfate (PDS) activator for the removal of Bisphenol A (BPA) in water. The unique properties of PSBC endowed it with multiple active sites including Fe(II) species, oxygen vacancy, CO, and graphite sp2-C with defects, owing to which, the PSBC/PDS process presented satisfactory performance with BPA removal efficiency up to 98 % within 60 min. Both of the radical and non-radical pathways were revealed to be involved in the BPA degradation. Based on the results of theoretical calculation, the existences of some special structures in PSBC effectively facilitated the electron transfer process of PDS activation. The process also exhibited a high anti-interference capability to coexisting substances and the universality toward various organic contaminants degradation. And the used PSBC can be recovered by simple thermal treatment. This work provided a promising heterogeneous PDS activator with plentiful active sites and satisfactory efficiency, which can be beneficial to the cost reduction of wastewater treatment and promotes the application of paper mill sludge in the area of environmental remediation.