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Structure And Property Of Surface Modified Low Pressure Reverse Osmosis (Lp-RO) Membrane By Using An Ionic Liquid

Posted on:2018-09-08Degree:MasterType:Thesis
Country:ChinaCandidate:J L ZhangFull Text:PDF
GTID:2381330593450201Subject:Chemical engineering
Abstract/Summary:PDF Full Text Request
Owing to their high perm-selectivity,thin-film composite?TFC?reverse osmosis membranes have played a predominant role in sea water desalination,occupying more than ninety percent of the reverse osmosis?RO?membrane market.However,the drawbacks of high energy consumption,high operation pressure and high fouling tendency bring negative effect on membrane performance stability and long-term stability,leading to increased running cost of RO system in practical operation.In this study,an environmental friendly ionic liquid was used to modify the commercial RO membrane,aiming at enhancing perm-selectivity,and consequently,reducing the energy consumption of the modified RO membrane.The 1,3-dimethylimidazolium dimethyl phosphate[MMIM][DMP]was synthesized by condensation reaction between N-methylimidazole and trimethyl phosphate at a constant temperature of 150?for 10 h,followed by rinsing with ether and vacuum evaporation.The synthesized product was characterized by 1H NMR spectrum,and the result proved the successful synthesis of[MMIM][DMP].The obtained[MMIM][DMP]was used to modify the commercial RO membrane?DOW BW30LE?,the effect of activation temperature,immersion time and[MMIM][DMP]concentration on the membrane morphology and performance was investigated.These characterizations revealed that the active layer of the modified RO membrane became thinner,smoother,and more hydrophilic compared to that of the pristine RO membrane.The optimal modification condition was 100 wt.%[MMIM][DMP]with immersion time of 4 min and activation temperature of 110?.Under this condition,the modified RO membrane can achieve62%higher water flux with 2.6%decrease in salt rejection compared to the pristine membrane,as well as enhanced anti-fouling property.The modified RO membrane also exhibited enhanced hydrophilicity and good long-term stability,showing stable permeation flux about 34 L·m-2·h-1 and rejection of 93%in 48 h continuous filtration test.Furthermore,the pristine membrane and modified membrane was arranged in the same two-double staged RO system running in the same water input/output amount.The modified membrane can achieve a water flux of 33.7 L·m-2·h-1 at the operating pressure 0.6 MPa,whereas a high operating pressure of 1.0 MPa was needed for the pristine RO membrane to achieve the same value of water flux.Therefore,modified RO membrane system could save50-60%energy consumption the compared to that of the pristine RO membrane system.
Keywords/Search Tags:Polyamide, Thin-film composite reverse osmosis membrane, Ionic liquid, Modification, Energy conservation
PDF Full Text Request
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