Degradation of humic acid using hydrogen peroxide activated by CuO-Co3O4@AC under microwave irradiation

To investigate the degradation of humic acid (HA) in a CuO-Co3O4@AC/H2O2 system under microwave irradiation, a catalyst (CuO-Co3O4@AC) was prepared and characterized. The effects of several reaction parameters, such as the microwave temperature, initial pH, H2O2 concentration, catalyst dosage and inorganic anions (HCO3 and Cl-) were investigated, and the synergetic effect of hydrogen peroxide among MW, AC and metal oxides was explored. The results indicated that cobalt and copper were supported on activated carbon and existed as Co3O4 and CuO. The removal efficiency of HA and TOC reached 88% and 71%, respectively, with 100 mg/L HA, 80 degrees C, 9.8 mM H2O2 and 0.5 g/L catalyst under 60 min of microwave irradiation. The existence of HCO3- and Cl- had an inhibitory effect on the degradation of HA, and the effect of HCO3- was more evident. Quenching experiments and EPR tests confirmed that (OH)-O-center dot and O-2(-center dot) were the main free radical species, and XPS analysis showed that the species present on AC were Co (II), Co (III) and Cu(II), which can activate H2O2 to produce (OH)-O-center dot and O-2(-center dot).