Degradation Of Humic Acid Using Superoxide Activated By Co₃O₄-CuO-AC Under Microwave Radiation

Humic acids?HAs?are the major components of natural organic matter?NOM?,which widely present in water.HAs affect the color and taste of water,they also chelating heavy metal and organic matter to become more complicated pollutions.Moreover,HAs could react with chlorine to produce trihalomethanes and haloacetic acids,which are strictly controlled in drinking water.So the removal of HAs from water is given serious attention.In this study,the degradation of commercial HAs was conducted in the MW/Co₃O₄-CuO-AC/H₂O₂?Na₂S₂O₈?system with different influence factors.The synergistic mechanism between MW,Co₃O₄-CuO-AC and H₂O₂?Na₂S₂O₈?,and the oxidation mechanism of free radicals were explored.The main content of research including:?1?In MW/Co₃O₄-CuO-AC/H₂O₂ system,the removal rate of UV254 and TOC of HAs were 88.2% and 71.2%,respectively,after 60 min treatment under the following condition: 80? of MW temperature,9.8 mmol/L of H₂O₂,0.5 g/L of catalyst dosage,7.0 of initial pH.In addition,in MW/Co₃O₄-CuO-AC/Na₂S₂O₈ system,the removal rate of UV254 and TOC of HAs were 90.3% and 79.7%,respectively,after 60 min treatment under the following condition: 80? of MW temperature,4.9 mmol/L of Na₂S₂O₈,0.5 g/L of catalyst dosage,7.0 of initial pH.?2?The degradation of HAs was fitted well with first-order kinetic equation with different factors in the MW/Co₃O₄-CuO-AC/superoxide system.In addition,the temperature could promote the generation of free radical to improve the HAs degradation efficiency.The reaction activation energy in MW/Co₃O₄-CuO-AC/H₂O₂ and MW/Co₃O₄-CuO-AC/Na₂S₂O₈ system were 82.5 kJ·mol-1 and 129.9 kJ·mol-1,respectively.?3?Though the test of EPR,·OH were found in the MW/Co₃O₄-CuO-AC/H₂O₂ system.·OH and O2-? were verified by quenching experiment with quencher of tertiary butanol and trichloromethane,and ·OH was the primary.In the MW/Co₃O₄-CuO-AC/Na₂S₂O₈ system,the result of EPR shows that ·OH and SO ?4-were generated.In addition,·OH and SO ?4-were verified the major types free radical after quenching by methyl alcohol and tertiary butanol.?4?The results of SEM shown that the hole become larger and equally distributed after active by HNO3,and the metallic oxides were successfully loaded onto the surface or in the holes of AC.BET data shown that the surface area and pore volume were increased after the metallic oxides loaded.The characteristic peak of CuO and Co3O4 were observed in the XRD pattern,which indicates that the successfully load of CuO and Co3O4 onto AC.After the analysis of XPS spectra,the species of Cu and Co on the AC were Cu?II?,Co?III?and Co?II?,respectively.