Peroxymonosulfate activation by vacuum ultraviolet and trace copper ions: A new way to boost Cu(II)/Cu(I) redox cycle

Herein, vacuum ultraviolet (VUV) was introduced to enhance the activation rate of peroxymonosulfate (PMS) by copper ions for the first time. Compared with ultraviolet (UV), the redox cycle rate of Cu(II)/Cu(I) was prominently enhanced by VUV due to the combined driving effect of UV, hydrated electron and active hydrogen atoms. The accelerated Cu(II)/Cu(I) cycle in VUV/PMS/Cu(II) system led to 2.89 times higher degradation efficiency of 2,4-dichlorophenol (2,4-DCP) than that by UV/PMS/Cu(II) system. More importantly, the initial Cu(II) concentration (5 μM) in VUV/PMS/Cu(II) system was only 1/5 of the guideline value in WHO standards for drinking water, and the initial PMS concentration was also 1 order of magnitude lower than that in most PMS based systems for water treatment. Furthermore, the reaction mechanism and possible degradation pathways of 2,4-DCP were also proposed. This study verified the possibility for the utilization of trace Cu(II) in water to decompose refractory micro-pollutants by PMS activation.