Study On Chlorine Resistance And Evaluation Method Of Aromatic Polyamide Composite Reverse Osmosis Membrane

Aromatic polyamide composite reverse osmosis(RO)membrane has been widely applied in field of water treatment due to its high water permeability and salt rejection.However,the poorly chlorine resistance performance of aromatic polyamide composite RO membrane has been given long-term attention.At present,the mechanism of chlorine resistance of aromatic polyamide composite RO membrane is inconclusive,and there is still a lack of evaluation method for chlorine resistance of aromatic composite RO membranes.So it has important significance to research on chlorine resistance and its evaluation method of aromatic polyamide composite RO membrane.In this paper,the chlorine resistance performance of aromatic polyamide composite RO membrane was studied by dynamic test and static test,respectively.The membrane performance before and after chlorination was tested by composite RO membrane.Scanning electron microscopy(SEM),Fourier transform infrared spectroscopy(ATR-FTIR),X-ray photoelectron spectroscopy(XPS)and Water contact angle(WCA)were used to characterize the membrane surface morphology,chemical structure,and wettability.Then combined with static test results,aromatic polyamide composite RO membrane chlorine resistance evaluation method was studied.The results showed that when using dynamic test method for chlorination,the flux decreased gradually and the rejection was almost invariant with the increase of chlorine time.When using static testing method,the concentration of active chlorine was less than 1000 ppm,the membrane performance decreased gradually with the increase of active chlorine concentration;and the concentration of active chlorine was more than 1000 ppm,the membrane performance decreased rapidly.The membrane performance degradation was caused by chlorinate degradable of polyamide layer,compacted or flattened peak valley structure,wetting reduction of the membrane surface and plugged membrane pore through the pollutants.Based on the static test results,we obtained the flux decay equation of aromatic polyamide reverse osmosis composite membrane:y=a×xb(1<x<1000),which provided a basis for the evaluation of aromatic polyamide composite RO membrane.According to the membrane flux degradation equation,the membrane flux attenuation amount of a specific concentration of active chlorine and chlorination at a certain time could be calculated.Then through the actual water demand to decide whether to replace RO membrane.The research provided the basic data for aromatic polyamide composite RO membrane chlorine resistance performance,and had a certain guiding significance on establishment of chlorine resistance evaluation method.