Enhanced photoelectrocatalytic decomplexation of Ni-EDTA and simultaneous recovery of metallic nickel via TiO_(2)/Ni-Sb-SnO_(2) bifunctional photoanode and activated carbon fiber cathode

In order to enhance Ni-EDTA decomplexation and Ni recovery via photoelectrocatalytic (PEC)process,TiO_(2)/Ni-Sb-SnO_(2)bifunctional electrode was fabricated as the photoanode and activated carbon fiber (ACF) was introduced as the cathode.At a cell voltage of 3.5 V and initial solution pH of 6.3,the TiO_(2)/Ni-Sb-SnO_(2)bifunctional photoanode exhibited a synergetic effect on the decomplexation of Ni-EDTA with the pseudo-first-order rate constant of 0.01068 min^(-1)with 180 min by using stainless steel (SS) cathode,which was 1.5 and 2.4times higher than that of TiO_(2)photoanode and Ni-Sb-SnO_(2)anode,respectively.Moreover,both the efficiencies of Ni-EDTA decomplexation and Ni recovery were improved to 98%from 86%and 73%from 41%after replacing SS cathode with ACF cathode,respectively.Influencing factors on Ni-EDTA decomplexation and Ni recovery were investigated and the efficiencies were favored at acidic condition,higher cell voltage and lower initial Ni-EDTA concentration.Ni-EDTA was mainly decomposed via·OH radicals which generated via the interaction of O_(3),H_(2)O_(2),and UV irradiation in the contrasted PEC system.Then,the liberated Ni^(2+)ions which liberated from Ni-EDTA decomplexation were eventually reduced to metallic Ni on the ACF cathode surface.Finally,the stability of the constructed PEC system on Ni-EDTA decomplexation and Ni recovery was exhibited.