Interfacial Polymerization Regulation And Performance Research Of High-performance Nanofiltration Membrane With Poly(ether Sulfone)support

Water is the source of life.As population all over the world continues going up,drinking water has become the key limit to the development of human.To increase the supply of water,water treatment technologies based on membrane separation has attracted widely attention in water desalination and waste water reusage.Nanofiltration,known as a rapidly developing membrane separation technique,can effectively remove salts,bacteria,viruses,biocides and other organic pollutes in groundwater and wastewater.Apart from drinking water treatment,nanofiltration membranes can be also used to supply high quality water for agricultural irrigation and industrial process.Besides,because of its inherent advantages,nanofiltration membranes possess the potential to take place of reverse osmosis membranes in new generation membrane bio-reactors.However,in the daily application of nanofiltration membranes,influenced by pollutes,membrane performance decreases.Therefore,chemical cleaning is always carried out,but the existence of hypochlorite would destroy the separation layer,leading to the sharp decrease of membrane performance.As a result,improving membrane chlorine resistance property can extend membrane lifetime and reduce membrane operation costs.In our work,ester groups were introduced to the separation layer to improve membrane chlorine resistance property,two series of membranes were prepared,and membrane performance was tested and studied.In the first part,sulfonated hyperbranched poly(aryl ether ketone)with hydroxyl groups on the side chain(SHPAEK-OH)was synthesized and took part in interfacial polymerization.After the introduction of sulfonic groups,membrane surface structure changed,membrane hydrophilicity was enhanced and membrane surface zeta potential decreased.As a result,water permeability increased and rejection to salts still held a high level.Membrane stability test showed that membrane performance changed little after long-term performance test.However,though the sulfonic groups possess strong electron withdrawing property and ester groups formed during interfacial polymerization,considering that the addition of SHPAEK-OH was little,ester structure in the formed separation layer was rare,improvement of membrane chlorine resistance property was not that much.In the second part,to further improve membrane chlorine resistance property,from the chemical structure of separation layer,phloroglucinol replaced piperazine and served as aqueous monomer to take part in interfacial polymerization.The skeleton structure of formed separation layer was polyester.Compared to polyamide,ester bonds could keep stable facing the attack of hypochlorite.At the same time,taking poly(aryl ether sulfone)with hydroxyl groups as support membrane,chemical bonds would form between separation layer and support layer during interfacial polymerization,membrane stability could be improved.Results showed compared to the traditional PA nanofiltration membrane,polyester nanofiltration membrane possessed loose separation layer,better hydrophilicity and more negative surface potential,which could increase membrane flux and keep a high rejection to salts.Besides,polyester nanofiltration membrane showed long-term stability performance after being performance under 0.6 MPa for 72 h.After immersed into sodium hypochlorite solution for 24 h,membrane could still hold a rejection of 90% to magnesium sulfate solution,and the normalized rejection was higher than 95%.Compared to the first part,the prepared membrane possessed a higher water flux and even better chlorine resistance property.