In recent years, water pollution has become one of the most predominant environmental problems. Organic refractory pollutants such as dyes and antibiotics are difficult to degrade in nature and thus cause water pollution. To solve this water pollution problem, the efficient removal of pollutants in wastewater is extremely important. Cobalt is the best metal element for activating peroxymonosulfate (PMS). In this study, we aimed to prepare transition metal-doped CoOOH catalysts to improve the activity of PMS.
The M-doped CoOOH catalyst was prepared as follows (M = Cu, Ni, Fe, Zn, and Mn). To 50 mL of 84 g/L of NaOH, 0.45 M Co(NO3)2·6H2O and 0.05 M metal nitrates were added in a volume of 25 mL. The mixture was stirred for 30 min. Then, 60 mL of 30% H2O2 was added, and the mixture was stirred at 60 ℃ for 24 h with a hot stirrer. The product was washed with distilled water and vacuum-dried. Dye decolorization was performed in the presence of peroxymonosulfate using the prepared CoOOH catalyst.
XRD measurements confirmed that CoOOH was prepared, as the characteristic peaks of CoOOH were observed. Some peak positions were shifted to the lower angle side in CoOOH doped with Cu, Ni, Fe, and Zn compared to CoOOH. In the decolorization experiments, RhB was decolorized by 15.2% after 10 min of reaction, when PMS solution was added alone, and by 26.3% in the CoOOH/PMS system. The decolorization rate of the M-doped CoOOH/PMS system was faster than that of the CoOOH/PMS system. Especially in the Ni-doped CoOOH/PMS system, RhB was decolorized by 77.8%. Therefore, X% Ni-doped CoOOH with different Ni doping was prepared and decolorization experiments were performed (X = 5, 10, 20, and 30). As a result, 87.2% of RhB was decolorized in the 20% Ni-doped CoOOH/PMS system.
