Integrated biosorption-photocatalytic oxidation treatment of di (2-ethylhexyl) phthalate
2006
Chan, H.W. | Chan, C.M. | Ang, P.O. | Wong, P.K., The Chinese Univ. of Hong Kong, Shatin, N.T., Hong Kong SAR (China)
Di (2-ethylhexyl) phthalate (DEHP), a toxic phthalate ester, is a plasticizer in the production of polyvinyl chloride products. It is a ubiquitous contaminant due to its extensive use and persistence. However, no available treatment method can cost-effectively remove DEHP 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 Sargasum siliquastrum. Since biosorption cannot detoxify DEHP, the degradation (and detoxification) of DEHP desorbed from seaweed biomass by photocatalytic oxidation (PCO) is attempted. The first part of this study is to optimize the conditions for the degradation of DEHP in aqueous solution by the PCO process. The effect of physico-chemical conditions, including reaction time, pH, TiO2 concentration, UV intensity, H2O2 concentration and DEHP concentration, on the PCO degradation of desolved DEHP were determined. Under optimized conditions, total degradation of 20 mg/L of DEHP was achieved within 45 min. The degradation intermediates/products such as phthalic anhydride and 2-ethylhexanol were identified by GC-MS analysis. Total organic carbon analysis was also conducted to ensure the complete mineralization of DEHP. Toxicity assays, including the Microtox and amphipod survival tests were used to assess the toxicities of the parental 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. DEHP was then desorbed from seaweed biomass by the selected organic solvent, and the desorbed DEHP was then degraded by the PCO process. Chemical analyses and toxicity tests were employed to identify the degradation intermediate and product(s) as well as their toxicity, respectively. Results indicate that the treatment for DEHP by integrating biosorption and PCO is feasible.
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