Selective oxidation of water pollutants by surface-complexed peroxymonosulfate during filtration with highly dispersed Co(II)-doped ceramic membrane

It is generally accepted that sulfate radical predominates pollutant removal when peroxomonosulfate (PMS) is activated by cobalt ion or cobalt-containing catalysts. Although sulfate radical is very reactive toward many contaminants, its nonselective reaction with various water constituents always limits its practical application. In this work, selective pollutant removal was achieved with oxidative filtration on a ceramic membrane doped with highly dispersed cobalt (Co-CM). It was observed that the oxidative filtration was insensitive to chloride, bicarbonate, and humic substances for pollutant removal, which is distinct from the oxidation relying on sulfate/hydroxyl radicals. Moreover, associated with very low Co2+ leaching (less than1 µg L−1), the oxidative filtration used more oxidation capacity of PMS than the homogeneous PMS/Co2+. Unlike heterogeneous PMS activation with Co-CM in jar tests where sulfate radical dominates pollutant removal, the predominant oxidant of the oxidative filtration was confirmed to be surface-complexed PMS. This study revealed that the hydraulic condition is an important factor to be taken into account when analyzing the mechanism of PMS activation, and this novel reaction pathway would endow the oxidative filtration with high selectivity for pollutant removal as compared with traditional slurry reactions.