Study on the performance and mechanism of verapamil degradation by zero-valent iron activated persulfate oxidation

Pharmaceuticals and personal care products (PPCPs) are a kind of refractory organic pollutants with large amount and wide range of pollution in environmental water, which can contaminate drinking water sources. The removal efficiencies of PPCPs are low during conventional drinking water treatment processes. Hence, it has attracted extensive attention on how to effectively remove PPCPs in water. The degradation of a common drug, verapamil was studied by using advanced oxidation technology based on sulfate radical which produced from zero-valent iron activated persulfate. The degradation kinetic model was established. The effects of zero-valent iron dosage, persulfate concentration, verapamil concentration, pH and temperature on degradation efficiency were investigated, and the main mechanism of degradation reaction was analyzed. The results showed that the degradation of verapamil followed the pseudo-first-order kinetic model well. The combination of 3 mm zero-valent iron and 3 mm persulfate could effectively remove 10 μM verapamil in 60 min. Lower pH and higher temperature were conducive to the degradation of verapamil. During the reaction, most of verapamil was transformed into intermediate products while only a small part was completely mineralized. • Verapamil could be efficiently degraded by sulfate radical-based oxidation. • Both ZVI dose and PS concentration had an inflection point in ZVI-PS system. • Low pH was conducive to the degradation of verapamil by ZVI-PS oxidation. • High temperature enhanced reaction rate but decreased stoichiometric efficiency of PS. • Most of verapamil transformed to intermediate products rather than mineralized.