Nanofiltration of natural and synthetic chemicals with hydrogen peroxide/UV pretreatment process.

摘要

This research addresses the application of nanofiltration and the H ₂O₂/UV advanced oxidation process (AOP), for the removal of natural organic matter (NOM) and synthetic organic chemicals (SOCs) in water supplies. In an attempt to improve nanofiltration performance, the H ₂O₂/UV pretreatment of source water, an efficient and cost-effective means for both fouling mitigation and SOC removal, as well as cleaning of fouled membrane, was investigated. It further examined the surface characteristics of membranes with regard to the nature and mechanisms associated with NOM fouling and cleaning using different chemical agents. Several surface characterization techniques were employed including attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and scanning electron microscopy (SEM). Furthermore, the study involved the development and application of a kinetic model for predicting the H₂O₂/UV decomposition rate of a model SOC, exemplified by the pesticide alachlor, and NOM in a source water. The proposed model facilitated the optimization of process variables for a given water quality matrix to achieve rapid decontamination in a cost-effective manner. Optimal operating conditions for the H₂O₂/UV oxidation were obtained through a systematic approach of combining modeling techniques with experimental data acquisitions, and applied for the pretreatment of source water prior to nanofiltration. The investigation revealed that the performance, as well as cost effectiveness, of nanofiltration for the removal of NOM and SOCs could be greatly improved by source water pretreatment and membrane cleaning. The H₂O₂/UV pretreatment prior to nanofiltration showed potential for the following: (i) mitigation of flux decline due to organic fouling and biofouling, (ii) removal of alachlor and hydrogen sulfide, and (iii) improvement in membrane cleanability. Nonetheless, careful control of the preoxidation must be exercised in order to reach reasonable compromise between fouling mitigation and NOM rejection.