| The addition of active chlorine can effectively alleviate the problem that reverse osmosis membrane is easy to be biological polluted,but it will also destroy the membrane structure,causing a sharp change of perm-selectivity.Development of reverse osmosis membrane with good chlorine resistance property can effectively simplify the pretreatment and cleaning process,prolong the service life and reduce the operating cost of the RO system.In addition,restoration of the chlorinated reverse osmosis membrane can restore the separation performance,extend the service life and reduce the environmental pollution caused by the abandoned reverse osmosis membrane.N,N’-Methylenebisacrylamide（MBA）contains two hydrophilic amide bonds,which can preferentially react with active chlorine,thus playing the role of sacrificial protection of aromatic polyamide membrane.Moreover,the two amide bonds also enable MBA to be filled into the polyamide structure destroyed by chlorination,to restore the chlorinated membrane.These two aspects have been studied in this thesis.MBA modified membranes were prepared by using MBA as aqueous phase additive with the assistance of UV irradiation.After the modification of MBA,the membrane surface roughness reduced,the contact angle decreased and the thickness of separation layer increased.Compared with the virgin membrane,the flux of the modified membrane increased by 14.7%and the rejection of the modified membrane remained approximately unchanged.After 2500 ppm×1 h（p H=7.5）chlorination,the flux and rejection of the chlorinated virgin membrane were reduced to 76.4%and 95.7%that of unchlorinated virgin membrane,while the flux and rejection of the chlorinated MBA modified membrane still remained at 90.4%and 98.6%that of unchlorinated MBA modified membrane.After Na2SO3 dechlorination,compared with the virgin membrane,the change of perm-selectivity of the MBA modified membrane was significantly reduced.The above results show that the flux,chlorine resistance and reversible chlorine resistance properties have been improved by MBA modification.In addition,the good stability of the MBA modified membrane was proved by continuous operation and acid/alkaline resistance test.MBA restored membranes were prepared by washing the chlorinated RO membranes with alkaline followed by grafting MBA to the membranes with the assistance of UV irradiation.After the restoration,the membrane surface roughness reduced,the contact angle slightly increased,the thickness of separation layer increased and the membrane surface negative charge content greatly reduced.The flux of the virgin membrane was 49 L/（m2·h）,and the rejection of the virgin membrane was98.90%.The flux and rejection of the chlorinated membrane were reduced to 61.40%and 88.63%that of the virgin membrane,respectively.The flux and rejection of the MBA restored membrane restored to 80.96～89.11%and 99.04～100.51%that of the virgin membrane,respectively.After 2500 ppm×1 h（p H=7.5）chlorination,the flux and rejection of chlorinated MBA restored membrane still remained at 93.9%and 99.1%that of unchlorinated MBA restored membrane,respectively.In the anti-lysozyme adhesion experiment,the flux decline rate of the restored membrane（42.14%）was slightly lower than that of the virgin membrane,meanwhile the flux recovery rate of the restored membrane was 20.48%higher than that of the virgin membrane.The above results show that MBA restored membrane repaired most of the flux,and has excellent chlorine resistance and anti-lysozyme adhesion properties.In addition,the good stability of the MBA restored membrane was proved by continuous operation and acid/alkaline resistance test. |
