Mild and economy homogeneous UV-LED/persulfate process for degradation of fluoxetine model drug

Abstract

A homogeneous persulfate (PS) activation under low energy consumption ultraviolet light-emitting diodes (UV-LEDs) was established in order to degrade the resistive fluoxetine-hydrochloride drug in aqueous media. For this aim, a falling film photo-reactor, equipped with four arrays of six UV-LEDs (395 nm, 1 W each), was utilized. Trace concentrations of ferrous sulfate and heating the media could significantly improve the degradation efficiency. Under the established optimal conditions of 100 mg/L of persulfate, 1 mg/L of ferrous sulfate, natural pH of 6.4 and temperature of 40 °C, a 71.1% degradation efficiency was achieved for 40 mg/L fluoxetine initial concentration after 50 min. The kinetic study revealed a pseudo-first order overall degradation rate. Based on scavenger quenching results, it was revealed that the hydroxyl radical and sulfate anion radical had, respectively, 52.3 and 31.4% contribution in degradation. To extend results to real conditions, the influence of inorganic cations/anions and also humic acid was investigated. From LC-MS analysis results, the transformation products were identified and three degradation pathways were proposed. Interestingly, a cost evaluation indicated electrical energy consumption of 16.7 kWh/m3 and operating cost of only $1.71 per each cubic meter. Consistently, the profound UV-LED/PS/Fe2+/heat process exhibited desired capabilities in scenarios for treating resistive drug wastewaters.