Efficient Degradation of Congo Red in Water by UV-Vis Driven CoMoO(4)/PDS Photo-Fenton System

In order to improve the catalytic activity of cobalt molybdate (CoMoO(4)), a PDS-activated and UV-vis assisted system was constructed. CoMoO(4) was prepared by coprecipitation and calcination, and characterized by XRD, FTIR, Raman, SEM, TEM, XPS, TGA Zeta potential, BET, and UV-Vis DRS. The results showed that the morphology of the CoMoO(4) nanolumps consisted of stacked nanosheets. XRD indicated the monoclinic structures with C2/m (C(3)(2h), #12) space group, which belong to α-CoMoO(4), and both Co(2+) and Mo(6+) ions occupy distorted octahedral sites. The pH of the isoelectric point (pHIEP) of CMO-8 at pH = 4.88 and the band gap of CoMoO(4) was 1.92 eV. The catalytic activity of CoMoO(4) was evaluated by photo-Fenton degradation of Congo red (CR). The catalytic performance was affected by calcination temperature, catalyst dosage, PDS dosage, and pH. Under the best conditions (0.8 g/L CMO-8, PDS 1 mL), the degradation efficiency of CR was 96.972%. The excellent catalytic activity of CoMoO(4) was attributed to the synergistic effect of photo catalysis and CoMoO(4)-activated PDS degradation. The capture experiments and the ESR showed that superoxide radical (·O(2)(−)), singlet oxygen ((1)O(2)), hole (h(+)), sulfate (SO(4)(−)·), and hydroxyl (·OH(−)) were the main free radicals leading to the degradation of CR. The results can provide valuable information and support for the design and application of high-efficiency transition metal oxide catalysts.