Highly efficient removing refractory organics continuously using a Fenton-like Filter: The role of in-situ galvanic effect enhanced peroxymonosulfate activation

Peroxymonosulfate (PMS) activation by heterogeneous catalysts is a promising method for removing organic contaminants in wastewater. However, recovery and stability of the catalyst limit its practical applications. Here we demonstrate that Co incorporated chitosan and immobilized on carbon-fiber (CF) sheets (Co-N/CF) by annealing can catalytically activate PMS for efficiently degrading refractory organic pollutants, and show excellent stability and recovery within a Fenton-like filtration device. Batch tests reveal the excellent activity of the Co-N/CF and the optimized synthesis condition. Radical-quenching experiments and EPR measurements confirm that the generated singlet oxygen (1O2) is the main reactive species. Excellent continuously treating performance is obtained under various conditions, including different initial organic concentration, various organic pollutants, PMS dosage, pH, co-existing anions, and natural organic matter. For example, under the conditions of 20 mg L−1 RhB, 25 ppm PMS and a flux rate of 15 mL min−1, the reactor can maintain 100% RhB removal rate for more than 32 h while the Co leaching is much lower than the standard value. Interestingly, in the presence of electrolytes, the removal rate can keep 100% under a much higher flux rate over 450 mL min−1, which is about 16 times higher than the wastewater without electrolyte. Based on the differential concentration in the filter and the conductivity of carbon based Co-N/CF and electrolyte, an in-situ galvanic effect between the upper and lower Co-N/CF plates can be formed, which can boost the generation of reactive species, thereby significantly improving the degradation performance. Present study provided a rational strategy for PMS activation in equipment level, and also presented a new insight into the mechanism of PMS heterogeneous activation.