Occurrence of Phthalates in common effluent treatment plants and removal by using Nano Titania-Graphene based photo-catalyst for tertiary treated effluent

Abstract

The occurrence and effectiveness of common effluent treatment plants (CETPs) for the removal of phthalates, as well as the fate of DEHP, are demonstrated in this study using a nano TiO2-Graphene-based photo-catalyst and photolytic system. Full-scale CETPs were selected at SIDCUL, Haridwar, and Unnao, Uttar Pradesh, along with installing a lab-scale photocatalytic reactor. Solid phase extraction (SPE) and gas chromatography-mass spectrometry (GCMS) was used to extract and quantify four phthalates, namely DEP, DBP, BBP, and DEHP, and byproducts.The average concentration of DEP, DBP, BBP, and DEHP in the mixed industrial effluent of CETP Haridwar exceeded by around ten folds than the literature value. Still, it was removed significantly by 77.9%, 32.8%, 97.5%, and 41.8%, respectively.The average influent concentration was eventually lower than the treated effluent at CETP Unnao, and phthalates were not removed during the process. During process optimization, the distinct ability of each method to remove DEHP during photolysis and photo-catalysis was discovered. The UV-TiO2-GO had removal effectiveness of 98% in 30 min at pH-6. However, at a dose of 500 mg, UV and UV-TiO2-GO had removal efficacy of 73% and 86%, respectively, for 180 min. After de-esterification, the UV system only cleaved the aliphatic chain, leaving the aromatic ring intact and producing a variety of byproducts. The superoxide ions (O2°−) and hydroxyl radicals produced in the photocatalytic process attacked not only the aliphatic chain but also the benzene ring.