Activation Of Persulfate With Magnesium Doped Metal Matrix Mate Rials For Phenol Degradation

In this study,Mg doped metal-based catalysts were prepared for the activation of persulfate（PS）for the degradation of phenol.The catalytic ability of Mg-CuO-Fe₂O₃/PS and Mg-Ni（OH）₂/PS systems were explored with phenol as the target pollutant.The structure and composition of the catalysts were characterized by XRD,SEM,ESR,and XPS.In addition,the effects of the dosages of catalysts and oxidants,the solution pH and the different inorganic anions were studied to obtain the optimum reaction conditions and test the stability of the catalytic system.（1）The degradation of phenol by Mg-CuO-Fe₂O₃/PSMg doped CuO-Fe₂O₃ composites were hydrothermally synthesized and characterized by powder X-ray diffraction（XRD）,scanning electron microscopy（SEM）and Raman spectroscopy.Mg doping improved the catalytic performance of CuO-Fe₂O₃ for phenol degradation as the removal efficiency of phenol（33 mg/L） reached up to 84.36%within 45 min using 3.2% Mg doped CuO-Fe₂O₃ coupled with persulfate（PS）system.The results revealed that Mg doping generated more defects（oxygen vacancies）,which result in the generation of more active species during the degradation process.The influences of catalysts and PS dosages were investigated to obtain the optimum conditions.The effects of pH and dissolved oxygen were also evaluated.Increase of solution pH was found to be beneficial for the removal of phenol because of reduced copper leaching at higher pH.However,decrease in dissolved oxygen concentration retarded the degradation of phenol because of the reduced production of O₂·^-.Based on the quenching experiments and ESR experiments,¹O₂,O₂·^-,·OH and·SO₄^-were confirmed as the active species in the phenol degradation process and a phenol degradation pathway was proposed.Other contaminants such as nitrobenzene（NB）,P-nitrophenol（PNP）and P-Chlorophenol（4-CP）could also be removed to some extent using the present catalyst system.（2）The degradation of phenol by Mg-Ni（OH）₂/PSMg doped Ni（OH）₂ was synthesized and investigated as an efficient catalyst to activate persulfate（PS）for phenol degradation.The property of the Ni（OH）₂ catalyst was enhanced by Mg doping as the removal efficiency of phenol was increased from 74.82%in Ni（OH）₂/PS system to 89.53% in Mg-doped Ni（OH）₂/PS system within 20 min.The experiments results revealed that doping Mg into Ni（OH）₂brings about more defects（oxygen vacancies）,which facilitated the formation of more active species in the catalytic process.The removal efficiencies of phenol increased with the increase of the initial pH from 3 to 11.The influences of Cl^-,NO₃^2-and HCO₃^-on the stability of the catalytic system were also studied and the results showed that removal rates of all systems in the presence of those different inorganic anions could reached about 90%within 20 min.Based on the electron spin resonance（ESR）experiments,¹O₂,O₂·^-,·OH and·SO₄^-were identified as the active species in Mg-doped Ni（OH）₂/PS system for phenol degradation and the degradation mechanism was proposed.In addition,the as-prepared catalyst remained its catalytic property even after 3 recycles.