Performance of the Persulfate/UV-C Process for the Treatment of Dimethyl Phthalate from Aquatic Environments

Abstract

Phthalate esters (PAEs) are used as plasticizers to impart flexibility and resilience to plastic products. In recent years, PAEs are a controversial issue because many phthalates are suspected to be mutagens, hepatotoxic agents and endocrine disruptors, and can lead to adverse effects on organisms even in a low concentration. Recently, sulfate (SO4·-) radical based advanced oxidation processes have attracted great scientific interest due to their high efficiency in the degradation and mineralization of recalcitrant and/or toxic organic pollutants. In the present study aqueous dimethyl phthalate (DMP; 100 mg L-1), being selected as a model PAE, was treated by the persulfate (PS)/UV-C process at pH 3 and varying PS concentrations (0-60 mM). DMP and TOC abatements increased with increasing PS concentrations from 5 to 40 mM. Further increase in the initial PS concentration, however, reduced both the rate and extent of DMP and TOC removals. The highest pseudo-first-order abatement rate coefficient and electrical energy per order (EE/O) values obtained for DMP treatment with PS/UV-C oxidation were found as 0.4493 min-1 and 1.79 kWh m-3 order-1, respectively, for PS = 30 mM, pH = 3, DMP = 100 mg L-1. The second-order reaction rate coefficient for DMP with SO4·- was determined as 1.47×109 M-1s-1 by the application of competition kinetics using phenol as the probe compound. Within the scope of the present study, aqueous DMP was also subjected to peroxymonosulfate (PMS)/UV-C and hydrogen peroxide (HP)/UV-C treatments. The performance of PS/UV-C treatment was found to be higher than that of PMS/UV-C and HP/UV-C treatments both in terms of DMP and TOC abatement rates at an initial oxidant concentration of 5 mM.