Pretreatment of polyvinyl alcohol by electrocoagulation coupling with catalytic oxidation:Performance,mechanism and pathway

In this study,various conditions for the removal of polyvinyl alcohol(PVA)by electrocoagulation(EC)coupled catalytic oxidation are systematically studied.The direct oxidation of the anode,the reduction of the cathode,the oxidation of·OH and·Cl,and the synergistic effect of flocculation on the degradation of polyvinyl alcohol are investigated.It is observed that the optimum experimental conditions obtained are as follows:Cell voltage 9 V,natural pH 7,NaCl concentration 0.02 mol/L,and interelectrode distance3.0 cm.The evolution of iron ions is also discussed in the EC process.By contrast,EC had made an outstanding contribution to the removal of PVA,which removes 71.29%of PVA.Free radicals,especially·OH and·Cl,are equivalent to the contribution of the electrodes in the degradation of PVA.And the contribution of PVA degradation by anode oxidation and cathode reduction are 12.76%and 8.02%,respectively.Characterization of solution and floc,such as Fourier transform infrared spectrometry(FTIR),scanning electron microscopy(SEM),energy dispersive X-ray spectroscopy(EDS),thermogravimetric analysis(TGA),GC-MS and molecular weight,showed that PVA is effectively removed by the EC process,and a possible degradation pathway is proposed.