Continuous flow degradation of Orange II by a dandelion-like NiCo2O4/NF activated peroxymonosulfate in a fixed-bed system

A novel dandelion-like catalyst, nickel foam supported NiCo2O4 (NiCo2O4/NF), was successfully synthesized and applied to the activation of peroxymonosulfate (PMS) in a fixed bed system for the degradation of Orange II (OII). The physicochemical properties of synthesis catalysts were identified by various characterization methods (SEM, EDS, XRD and XPS), revealing that the dandelion-like NiCo2O4 nanosheets were evenly distributed on the surface of NF. NiCo2O4/NF-250 showed excellent catalytic performance at a hydrothermal reaction time of 8 h, urea/ metal ratio of 10:1, and Co/Ni concentration of 10 mM/5 mM. When PMS concentration was 5 mM, reaction temperature was 50 celcius, pH was 7.5, space velocity was 0.236 min-1, the conversion ratios of OII, PMS and COD were 99.8 %, 71.3 %, and 71.4 % at 240 min, respectively. In particular, NiCo2O4/NF still could reach 99.9 % OII conversion and 64.4 % COD conversion in the third cycle. DFT calculations implied that NiCo2O4/NF had excellent PMS activation performance.