Efficient degradation of Rhodamine B in water by CoFeO/HO and CoFeO/PMS systems: A comparative study.

In this work, a comparative study of efficient degradation of Rhodamine B (RhB) in CoFeO/HO and CoFeO/PMS systems was performed. Batch experiments indicated that the RhB degradation rate of CoFeO/HO system reached 95.5% at 90 min under the condition of 0.5 g L of CoFeO dosage, 10 mM of HO concentration and 3.0 of initial pH. At certain conditions of initial pH = 7.0, 0.3 g L of CoFeO dosage, 7 mM of PMS concentration, CoFeO/PMS system could completely degrade RhB within 90 min. EPR and quenching experiments indicated that •OH was the main active species of CoFeO/HO system, and •OH, SO•, •O and O participated in RhB degradation of CoFeO/PMS system. The circulate of Co(II)/Co(III) and Fe(II)/Fe(III) on the CoFeO surface promoted the formation of free radical species in the two system. In CoFeO/PMS system, the formed •O and SO• realized the generation of non-free radical species (O). The LC-MS results indicated that N-de-ethylation, chromophore cleavage, opening rings and mineralization were the main steps for the RhB degradation of the two systems. After five cycles of degradation experiment, the CoFeO/HO and CoFeO/PMS systems still maintained the high degradation rate (85.2% and 92.4%) and low mass loss (2.7% and 3.09%). In addition, CoFeO/PMS system had better potential value for the actual water and multi-pollutant degradation than CoFeO/HO system. Finally, the toxicity analysis and cost assessment of the two oxidation systems were preliminarily evaluated.