Study On The Influence Of DOM-polluted Nanofiltration Membranes In Raw Water On The Removal Behavior Of PPCPs

In recent years,as more and more trace organic pollutants like PPCPs in surface water and drinking water have been frequently detected,and PPCPs are continuously discharged into the environment due to human life,so PPCPs The phenomenon of "false persistence" appears in the environment.Because PPCPs exist in humans or organisms for a long time and cause harm to humans or animals,it is necessary to remove PPCPs in water.However,some technical methods such as conventional water treatment technology cannot effectively remove PPCPs in water bodies.For this reason,it is very important to study and develop high-efficiency PPCPs removal methods in water.In this study,NF-C and NF-75 were selected.By comparing the rejection rate of different nanofiltration membranes for PPCPs and the rejection rate of the same nanofiltration membrane for different PPCPs,according to the molecular size of PPCPs and the difference between PPCPs The morphology of the water,the amount of adsorption per membrane area and the characteristics of the membrane surface are used to analyze the removal mechanism of PPCPs by nanofiltration membranes.At the same time,the nanofiltration membrane will be polluted when the raw water is processed,the DOM in the raw water of Ganjiang River was selected to pollute the nanofiltration membrane,and the removal rate of PPCPs by the polluted nanofiltration membrane and the membrane surface characteristics after membrane pollution were analyzed.The effect of DOM on the removal of PPCPs by nanofiltration membranes.The main conclusions are as follows:1.The types and concentrations of PPCPs in the raw water of Ganjiang River in different locations and different seasons were detected by liquid chromatographymass spectrometer.The experiment found that there are indeed many kinds of PPCPs in the Ganjiang water body,and there are temporal and spatial differences in the types and concentrations of PPCPs.Among them,the detection rate of CAF,TC,CF reached 100% and the concentration was high.2.Comprehensive analysis of the removal rate of NF-C and NF-75 on 10 common PPCPs in water bodies,and found that the removal rate of most PPCPs by the two nanofiltration membranes is over 80%.The nanofiltration membrane process is to remove water An effective method for trace organic pollutants.By comparing the removal rate of neutral PPCPs with the molecular size of PPCPs and the pore size of the nanofiltration membrane,it is confirmed that the nanofiltration membrane has a sieving effect in the process of removing PPCPs;by changing the p H value of the water body,it is confirmed that the nanofiltration membrane can remove PPCPs.There is electrostatic effect in the process;by calculating the amount of adsorption on the surface of the nanofiltration membrane,it is confirmed that there is an adsorption effect in the process of removing PPCPs by the nanofiltration membrane.According to the properties of PPCPs themselves and the properties of the surface of the nanofiltration membrane,it is found that in the removal process,the influence of the three mechanisms of action is not the same.3.The nanofiltration membrane was characterized after DOM pollution.It was found that after DOM pollution,the negative charge on the membrane surface increased,and the hydrophobicity of the membrane surface also increased,which means that the adsorption effect of the nanofiltration membrane was strengthened and the electrostatic effect was strengthened.DOM contamination will form a dense filter cake layer on the surface of the nanofiltration membrane,reducing the size of the membrane pores.At the same time,DOM may also polymerize with PPCPs to form macromolecular organics,which enhances the screening effect.Due to the enhancement of sieving effect,which prevents PPCPs from passing through the nanofiltration membrane,a local high-concentration solution of PPCPs will be formed on the surface of the nanofiltration membrane,forming a concentration polarization phenomenon and accelerating PPCPs to pass through the nanofiltration membrane.Therefore,the removal rate of PPCPs by the nanofiltration membrane after DOM pollution is determined by a variety of mechanisms.According to the different properties of PPCPs and the surface properties of the nanofiltration membrane,the removal mechanism of different PPCPs by the nanofiltration membrane after DOM pollution is also different.not exactly.