Effects of pH and Anions on the Generation of Reactive Oxygen Species (ROS) in nZVI-rGo-Activated Persulfate System

In this study, nanosized zero-valent iron-reduced graphene oxide (nZVI-rGO)-activated persulfate (PS) was used to investigate the generation of reactive oxygen species (ROS) for the degradation of trichloroethylene (TCE) in the aqueous solution. More than 98 % of TCE was degraded within 2 min under experimental conditions. The generation of ·OH increased when the pH was shifted toward the basic region while ·SO4− radicals’ intensity increased in the acidic pH. Different scenarios have been observed in ·O2− generation in the neutral and strong basic pH and decreased in acidic or slightly basic pH. In addition, the intensity of ·OH was increased with the addition of HCO3− (10 mM) and NO3− (100 mM) but decreased in the presence of Cl− (10 and 100 mM), HCO3− (100 mM), and NO3− (10 mM). The degradation of anisole, probe for both ·OH and ·SO4−, was slightly enhanced by 10 mM NO3− anions but decreased in 100 mM salt solution. ·O2− intensity was increased while HCO3− (10 and 100 mM) and NO3− (100 mM) anions were used. nZVI-rGO-activated PS process could remove TCE in aqueous effectively, and the ROS generation and intensity were influenced by solution pH values and anions.