Solar photo-Fenton oxidation of cytostatic drugs via Fe(III)-EDDS at circumneutral pH in an aqueous environment

Abstract

Cytostatic drugs have been widely and increasingly used and are poorly biodegraded in wastewater treatment plants, so they are commonly found in wastewater effluents. This study applied a solar photo-Fenton process to remove cyclophosphamide and 5-fluorouracil. The complex Fe(III)-ethylenediamine-N,N’-disuccinic (EDDS) degraded cyclophosphamide and 5-fluorouracil more efficiently than three other Fe(III)-ligand complexes under ultraviolet (UV) and solar light irradiation. Fe(III)-EDDS also showed higher photoreactivity under solar light than under UV light. Cyclophosphamide and 5-fluorouracil showed increasing degradation with increasing Fe(III)-EDDS concentration and H2O2 dosage. The addition of EDDS can widen the operational pH range of the solar photo-Fenton process to pH 3.0−8.5. A suitable Fe(III):EDDS ratio and initial dissolved oxygen level were demonstrated to affect the degradation performance. Cyclophosphamide and 5-fluorouracil were rapidly degraded within 1.5 min (k = 5.131 and 5.407 min−1, respectively) in the solar photo-Fenton process with the concentration of 0.1 mM Fe(III)-EDDS and 1 mM H2O2, and detoxification throughout the process was also ensured. In addition, this study is the first to combine the UV/H2O2 process with the solar photo-Fenton process to achieve the goal of total mineralization. For engineering purposes, this solar photo-Fenton process with a relatively low Fe(III) concentration and H2O2 dosage provides a promising potential alternative method for wastewater treatment under natural pH conditions with solar light.