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

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 (k(obs) = 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 (k(obs) = 0.40 (+/- 0.03) min(-1)), chlorides and bicarbonates showed minimal impact, and anoxic conditions inhibited TP degradation with a significant decrease in k(obs) e.g. 0.817 (+/- 0.41) x 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 (k(obs) = 6.9 (+/- 0.9) x 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).