Evaluation of UVC-Activated Persulfate for the Degradation of Tramadol in Water

Abstract

Wastewater from the pharmaceutical industry is a main source of surface and groundwater contamination by organic contaminants, particularly active pharmaceutical ingredients (APIs). Conventional treatment strategies do not completely eliminate these contaminants, leading to the release of toxic effluents into the environment. The stability of these compounds and their resistance to conventional treatment methods indicates the need for degradation strategies designed for point-source treatment before arrival to municipal wastewater treatment plants. Advanced oxidation processes (AOPs), which utilize oxidants such as H2O2 or persulfate (PS) to treat organic contaminants, have shown great results in the elimination of pharmaceuticals from wastewater. Multiple studies have demonstrated their ability to generate reactive radical species that can break down stable molecules. This research investigated the degradation of Tramadol (TRA), a fully synthetic opioid, in a UVC/PS system. Preliminary experiments were performed using other PS activation systems. The results showed that UVA and thermal activation were inefficient in breaking down TRA compared to UVC. Different concentrations of PS were tested, and the UVC/PS system with [PS]0 = 0.4 mM was able to achieve complete degradation of [TRA]0 = 10 mg L-1 in 6 min and was chosen for this study. The UVC/PS system was evaluated under different conditions including pH, the presence of common water matrices such as chlorides, bicarbonates, nitrates and humic acid, and the level of dissolved oxygen in water. The results from these experiments offer valuable insight for the development of pilot-scale treatment plants using UV-activated PS. Our team developed one such pilot-scale treatment plant, utilizing elements from commercially available UV water disinfection kits for continuous-flow treatment of pharmaceutical industry effluent. After optimization, the system was able to achieve full degradation of 360 L day-1 of [TRA]0 = 10 mg L-1.