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

ABSTRACT

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.