Integrated biosorption and photocatalytic oxidation treatment of di(2-ethylhexyl)phthalate

Di(2-ethylhexyl)phthalate (DEHP), a toxic phthalate ester, is a ubiquitous contaminant due to its extensive use and persistence. No available treatment method can cost-effectively remove it from industrial wastewater. In a previous study, DEHP was effectively removed from aqueous solution by adsorption onto the biomass of selected seaweed, i.e., beached seaweed and Sargassum siliquastrum. Since biosorption cannot detoxify DEHP, the degradation (and detoxification) of desorbed DEHP from seaweed biomass by photocatalytic oxidation (PCO) was attempted. The first part of this study was to optimize the conditions for the degradation of desorbed DEHP in aqueous solution by PCO. Under optimized conditions, a total degradation of 20 mg/L of DEHP was achieved within 45 min. The degradation intermediates/products such as phthalic anhydride and 2-ethyhexanol were identified by GC-MS analysis. Total organic carbon analysis was also used to ensure the complete mineralization of DEHP. The Microtox® test was used to assess the toxicities of the parent and degraded compounds. In the second part of this study, DEHP was first removed and concentrated by adsorption onto seaweed biomass under the conditions optimized in the previous study. It was then desorbed from seaweed biomass and degraded by PCO. Results indicate that the treatment for DEHP by integrating biosorption and PCO is feasible.