Degradation of theophylline in a UV254/PS system: Matrix effect and application to a factory effluent

Abstract

Oxidative degradation of emerging waterborne contaminants, particularly pharmaceuticals, is currently an extensively studied field of research. In this study, a UV-254 nm activated persulfate (PS) system (UV254/PS) was used to eliminate Theophylline (TP) from simulated and real industrial effluents. Results showed that TP is strongly resistant to degradation through direct photolysis under UV-254 nm irradiation. UV254/PS system showed efficient degradation, in which [PS]0 = 0.25 mM achieved total degradation of [TP]0 = 10 mg L−1 in a period of 20 min and followed a pseudo-first order reaction kinetics (kobs = 0.173 (±0.004) min−1). Effect of several matrix parameters were tested to study the robustness of TP degradation in real-life cases such as pH, chlorides, bicarbonates, and dissolved oxygen, in which neutral pH gave the highest degradation rate (kobs = 0.40 (±0.03) min−1), chlorides and bicarbonates showed minimal impact, and anoxic conditions inhibited TP degradation with a significant decrease in kobs e.g. 0.817 (±0.41) × 10−1 min−1. Additionally, TP was spiked into natural spring, sea and wastewater, where the three tested matrices showed a decrease in the degradation rate, with the latter being the most significant (kobs = 6.9 (±0.9) × 10−3 min−1). Radical scavenging experiments showed that sulfate radicals were the main contributors in TP degradation. Furthermore, wastewater effluent obtained from a local pharmaceutical manufacturing facility and containing [TP]0 = 160 mg L−1 was also tested and showed successful full degradation over 3 h in 25 mM PS-spiked medium with an average reaction stoichiometric efficiency of about 3.7% and at an estimated cost of 17.2 $ m−3. © 2019 Elsevier B.V.