Electro-UV/H2O2 system with RGO-modified air diffusion cathode for simulative antibiotic-manufacture effluent treatment

Development of UV/H2O2 in practical application has been obviously constrained by inflexible H2O2 doping and less security and high cost from H2O2 transport and store. In-situ generating H2O2 via electrochemical oxygen reduction reaction (ORR), named electro-UV/H2O2 system, may provide an alternative way to enhance its efficiency and decrease its cost, especially for dealing with high-salinity organic wastewater. Electro-UV/H2O2 system was constructed with graphite-based air diffusion cathode (GADC) to enhance efficiency and economy of the traditional UV/H2O2 system. For creating extra benefit by the UV radiation, reduced graphene oxide (RGO) was attempted to modify the GADC via inner mixture (RGO@GADC-1) and further superficial deposition (RGO@GADC-2). One-step electrochemical reduction with anhydrous graphene oxide (GO) dispersion was developed for superficial modification of RGO with high-efficiency and good uniformity. The physical-chemical and electrochemical characterization showed little change of porous structure by RGO-doping and increased hydrophily and electrocatalytic activity by surface deposition of RGO. Average H2O2 production of 187.5 similar to 243.7 mg L(-1)h(-1)cm(-2) were obtained, which were explained according to the potential energy barrier and desorption energy from DFT calculation. RGO@GADC-2 enhanced the TOC removal efficiency and mineralization current efficiency (MCE) of penicillin sodium (PGS) by 79.13% and 49.3% to 91.13% and 56.8%, respectively. The photocatalysis of RGO was confirmed to provide additional oxidative free radicals via reactions including donating UV-excited electrons for (i) one-electron ORR and (ii) H2O2 decomposition and (iii) UV-excited holes for water-splitting were evaluated.