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Preparation And Performance Research Of Composite Reverse Osmosis Membrane By Electrostatic Deposition Of Polyelectrolyte

Posted on:2019-09-07Degree:MasterType:Thesis
Country:ChinaCandidate:M L LiuFull Text:PDF
GTID:2381330596466832Subject:Chemical Engineering
Abstract/Summary:PDF Full Text Request
Improving the separation and permeation performance and anti-fouling performance of reverse osmosis?RO?membranes has always been an important research direction for reverse osmosis membranes.In this paper,the commercial aromatic polyamide thin-film composite reverse osmosis membrane was used as the substrate membrane.And its surface was modified by chlorination treatment and electrostatic deposition to prepare the composite reverse osmosis membrane with excellent performance.The commercial membrane surface was chlorinated with sodium hypochlorite solution,followed by alkaline cleaning of the chlorinated membrane.Then the chitosan as a polycation electrolyte was deposited on the surface of the alkaline cleaning membrane by electrostatic attraction.The effects of solution pH,chlorination time,sodium hypochlorite concentration,chitosan concentration and deposition time on water flux and salt rejection of modified membranes were systematically investigated.And to observe and analyze the surface morphology,roughness,hydrophilicity,chemical structure,elemental composition and charge characteristic,a series of characterizations of original and modified membranes were performed,including field emission scanning electron microscope?FESEM?,atomic force microscope?AFM?,contact angle measuring instrument,Fourier transform infrared spectrometer?FT-IR?,X-ray photoelectron spectroscopy?XPS?and solid surface Zeta potential tester.Three pollutants such as sodium alginate?SA?,lysozyme and cetyltrimethylammonium chloride?CTAC?were selected to study the anti-fouling property of the modified membrane.In addition,the stability of chitosan deposition modified membrane was also investigated.The results showed that,when the chlorination solution pH=9,the chlorination time was 30 min and the sodium hypochlorite concentration was 1000 mg·L-1,the optimum chlorination conditions were achieved.The water flux of the chlorination membrane was 60.75 L·m-2·h-1,and the salt rejection was 99.45%.Compared to the original RO membrane,the water flux of the chlorination membrane increased by19.89%,and a slightly increase of the salt rejection was also observed.After alkaline cleaning,the water flux increased to 67.69 L·m-2·h-1,and the salt rejection decreased to99.31%which was higher than the salt rejection of original RO membrane.When the chitosan concentration was 0.1 wt%and the deposition time was 30 min,the optimum deposition conditions were achieved.The water flux of the deposition modified membrane was 66.52 L·m-2·h-1,and the salt rejection was 99.69%.Compared to the original RO membrane,the water flux of the deposition modified membrane increased by 31.28%.And the salt rejection also had a certain degree of improvement.Meanwhile,further modification of chitosan deposition on the alkaline cleaning membrane surface showed that the surface hydrophilicity of the deposition modified membrane was greatly enhanced,whose contact angle decreased to 30.75°.After fouling experiments and stability test,it could be found that the chitosan deposition modified membrane presented excellent anti-fouling property and stabilty.
Keywords/Search Tags:Reverse osmosis membrane, Water flux, Salt rejection, Surface modification, Chlorination, Electrostatic deposition, Hydrophilicity, Anti-fouling
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