Photodegradation of the endocrine-disrupting chemicals 4n-nonylphenol and triclosan by simulated solar UV irradiation in aqueous solutions with Fe(III) and in the absence/presence of humic acids

Abstract

► Photodegradation of 4 n -NP and TCS were investigated using experimental design. ► Different pH, concentration of Fe(III) and humic acids were evaluated. ► The presence of Fe(III) and basic pH increases the oxidation rate for triclosan. ► Synergistic effect was observed for presence of Fe(III) and HAs for 4 n -nonylphenol. ► First publication reporting of endocrine-disrupting chemicals photodegradation in waters from Colombia. 4 n -Nonylphenol (4 n -NP) and triclosan (TCS) are endocrine disrupters that are used widely in personal care products. They are mainly transported in domestic sewage, which can eventually reach natural waters (rivers, lakes or reservoirs). In this work, the photodegradation of 4 n -NP and TCS using a solar simulator (300–800 nm) at two different pH levels, two different concentrations of ferric ion, Fe(III), and in the absence/presence of humic acids (HAs) were investigated. A Xe lamp (250 W m −2 ) was employed as the light source. The conditions were chosen to simulate a natural aquatic environment. The experiments were performed using a factorial design for three factors with eight combinations of the factors studied. Experiments performed in ultrapure water showed that the degradation of 4 n -NP was faster than that of TCS. The data showed that first-order reaction kinetics describe the degradation of both compounds well; the half-lives of TCS and 4 n -NP were 5.4 h and 2.3 h, respectively. For TCS, the results indicated that the oxidation rate increases in the presence of Fe(III) and at basic pH levels; however, the rate it decreased in the presence HAs. In the case of 4 n -NP, synergistic effect was observed for presence of Fe(III) and HAs. The best conditions were a basic medium (pH 9) and an Fe(III) concentration of 2 mg L −1 without HAs for TCS and a pH of 9, an Fe(III) concentration of 2 mg L −1 and a HAs concentration of 1 mg L −1 for 4 n -NP. The results of photodegradation of both compounds in water from two reservoirs showed that the photodegradation was highly dependent on the conditions of the aquatic environment.