Research On The Removal Of Trace Paes By Nanofiltration Membranes From Water Sources

Phthalate acid esters (PAEs) is a typical class of endocrine disrupting compounds, it may affect human health, which have received extensive attention. Therefore, the technology of effectively removing such micropollutants have became the study hotspot. Nanofiltration membrane is one of the advanced technologies, with the advantages of good separation, low operating pressure and high removal efficiency for PAEs, indicating the broad application prospect of which in water treatment.In this thesis, PAEs such as dimethyl phthalate (DMP), diethyl phthalate (DEP), di-n-butyl phthalate (DnBP) and diisobutyl phthalate (DiBP) were selected as the target compounds. Applications of nanofiltration membranes, NF270-2540and DK2540, to remove PAEs from water sources, were researched herein. The main results of the research were as follows:1. Adsorption and rejection characteristics of nanofiltrationAdsorption behavior of DMP, DEP, DnBP and DiBP on DK2540and NF270-2540were studied. It was found that the adsorption capacity of PAEs on nanofiltration membranes increased with the increasing initial concentration of PAEs. The octanol-water partition coefficient (logKow) and solubility of PAEs had effect on the adsorption capacity. The adsorption isotherm of PAEs on nanofiltration membranes fited Freundlich adsorption equation well. Freundlich adsorption isotherm parameter1/n of DMP, DEP, DnBP and DiBP for NF270-2540were0.61,0.61,0.61and0.59, respectively; of that for DK2540, they were0.62,0.62,0.61and0.60, respectively. In addition, the parameter K of DMP, DEP, DnBP and DiBP for NF270-2540were0.05,0.09,0.13and0.17, respectively; of that for DK2540, they were0.04,0.08,0.12and0.15, respectively. The adsorption capacity of DMP, DEP, DnBP and DiBP on NF270-2540(KNF270-2540) were all greater than that of DK2540(KDK2540).Rejection characteristics of NF270-2540and DK2540in removing trace PAEs from water had been investigated. It could be concluded that the rejection characteristics of the membranes involved the adsorption retention and the pore retention of the membranes before adsorption reached equilibrium. After adsorption reached equilibrium, the rejection mechanisms of the membranes could be described pore model. And the rejection of DMP, DEP, DnBP and DiBP by NF270-2540were44.4%,68.2%,92.7%and93.1%, respectively; the rejection of DMP, DEP, DnBP and DiBP by DK2540were55.1%,78.0%,96.0%and96.8%, respectively. It showed that the rejection of PAEs by DK2540is better than that of NF270-2540, and the trace DnBP or DiBP in water could be removed effectively by NF270-2540and DK2540.2. The effect of experimental condition on the rejection of PAEsThe effect of the experimental condition such as feed concentration, pH, ionic strength and operating pressure on the rejection of PAEs were studied with the experiment of DEP removal by DK2540. The results were as followed:(1) The operating pressure was a very important factor influencing permeate flux of DK2540. Increasing operating pressure, the flux and the rejection of DEP increased;(2) The feed concentration of DEP was proportional to the rejection by DK2540, and inversely proportional to the flux;(3) The rejection of DEP reduced as pH of feed increased, with the contrary trend of DK2540flux increased;(4) The higher the ionic strength of the feed, the lower the flux of DK2540, the higher the rejection of DEP.