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.