Persulfate enhanced photoelectrocatalytic degradation of cyanide using a CuFe2O4 modified graphite felt cathode

Abstract In order to remove cyanide (CN − ) from wastewater, a photoelectrocatalytic (PEC) system was constructed using TiO 2 nanorods (NRs) anode and CuFe 2 O 4 modified graphite felt (CuFe 2 O 4 /GF) cathode. With the addition of persulfate (PS), the performance of PEC for the removal of CN − with an initial concentration of 0.9 mM was increased from 31.10% to 98.21% in 120 min and the pseudo-first-order rate constant was calculated to be 0.0314 min −1 . The removal rate of CN − was accelerated with the decrease of initial CN − concentration and the increase of PS dose. The optimal bias potential for the removal of CN − and the recovery of Cu was 1.00 V. Results of radical quenching experiments and electron spin resonance analysis suggested that OH and SO 4 − were generated by a Fenton-like process in the PEC/PS system. As proved by the XPS analysis, Cu(II) in CuFe 2 O 4 cathode was dissolved by CN − into solution and then partially transformed to Cu(I). When CN − was removed, dissolved Cu ions were deposited onto the surface of CuFe 2 O 4 cathode forming Cu 2 O. In addition, the dissolved Cu ions can also be deposited on TiO 2 photoanode forming CuO. Cu(I) ions reacted with PS through a Fenton-like reaction, generating SO 4 − , which enhanced the oxidation ability of the PEC/PS system. The results provided a promising way to treat the industrial cyanide effluents efficiently.