MgxCu-biochar activated peroxydisulfate triggers reductive species for the reduction and enhanced electron-transfer degradation of electron-deficient aromatic pollutants

In wastewater treatment by persulfate-based advanced oxidation processes (PS-AOPs), electron-deficient aromatic pollutants (EDAPs) are refractory to nonradical pathway. To explore an efficient degradation pathway for EDAPs, MgxCu-biochar (BC) (x = 0.5, 1, 1.5) activated peroxydisulfate (PDS) was developed, which could trigger reductive species (•H) to reduce EDAPs first, and subsequently facilitate electron-transfer degradation of reduced intermediates. The roles of Mg-doping in MgxCu-BC to promote PDS activation and 2,4-dibromophenol (DBP) degradation were investigated. The mechanisms were then explored via electron paramagnetic resonance (EPR), chemical probes and Density Functional Theory (DFT) calculations. The results showed that Mg-doping improved metal-support interactions (MSIs) of MgxCu-BC, inducing •H formation via electron transfer from Cu atoms during PDS activation, which was thermodynamically favorable. The degradation rate of DBP (kobs, 0.0494 min–1) and Br– release (5.35 mg L–1) in Mg1Cu-BC systems were more 31 and 33 times than that in Cu-BC/PDS system, respectively. The degradation mechanism of •H-enhanced electron transfer processes was that •H attacked one Br group of DBP, and then debrominated intermediates were mineralized by electron transfer processes in the Mg1Cu-BC/PDS system. Overall, this study reports a novel pathway in PS-AOPs for selective degradation of EDAPs in wastewaters. [Display omitted] •Mg-doping changed the morphologies of MgxCu-BC to form Cu4MgO5 structure.•Mg-doping enhanced PDS adsorption and activation by MgxCu-BC.••H was generated from H+ reduction by Cu atoms of MgxCu-BC in PDS activation.••H-enhanced electron transfer processes could efficiently degrade EDAPs.