Catalysis of cupric and cuprous oxides in copper pipes on the diatrizoate transformation with peroxymonosulfate as a disinfectant

Abstract

Cupric and cuprous oxides (CuO and Cu2O) are the main corrosion products of copper pipes; peroxymonosulfate (PMS) is a good drinking water disinfectant; micropollutants are ubiquitous in the factory waters. Corrosion products influence the micropollutant transformation under the action of disinfectants. This study compared the conversion of diatrizoate (DTZ) with PMS as a disinfectant under the catalysis of CuO (Cu(II)PS) and Cu2O (Cu(I)PS). The pseudo-first-order constant (kobs) for the DTZ degradation in the Cu(II)PS was 11.8 times that in the Cu(I)PS, with values of 0.092 and 0.0078 min−1, respectively. SO4− and HO played dominant roles in the Cu(II)PS, while O2− and 1O2 were the primary contributors in the Cu(I)PS. The yield ratio of reactive species were 92.8% and 69.6% in the Cu(II)PS and Cu(I)PS, respectively. The DTZ degradation was promoted by the increase of CuO dose, while inhibited by the increase of Cu2O dose (0.1–1.0 g L−1). In both Cu(II)PS and Cu(I)PS, the DTZ degradation was enhanced by the increasing PMS dose (10–100 mg L−1) and neutral pH (7.0), whereas weakened by water matrix (NOM, HCO3− and Cl−). The total organic iodine was mainly converted to IO3− with a ratio of 45.3 and 7.4% in the Cu(II)PS and Cu(I)PS, respectively. In the Cu(II)PS, the DTZ transformation was mainly through the amide hydrolysis followed by amino oxidation and stepwise deiodination followed by hydroxyl addition. However, hydroxyl addition is not thought to occur in the Cu(I)PS since the related intermediates have not been identified. The study helps to comprehensively understand the conversion of iodine-containing micropollutants in copper pipes when PMS is a disinfectant.