The Fouling Behaviour Of EVOH Ultrafiltration Membrane By The Typical Dissolved Organic Matter

In order to explore the behavior of dissolved organic compounds on ethylene-vinyl alcohol polymer(EVOH)ultrafiltration membrane,bovine serum albumin(BSA),sodium alginate(SA)and humic acid(HA)were used to represent the ubiquitous protein,polysaccharides and humus organic matter in the wastewater.Through the macroscopic membrane fouling experiment combined with micro-force,the micro-adsorption process of pollutants on the membrane surface and the characteristics of the pollution layer,to analysis the flouing mechanism of typical organic compounds to EVOH Ultrafiltration membrane,and then obtain the superior membrane fouling of EVOH ultrafiltration membrane.Based on this,the mechanism of the effect of Mg2+on the membrane fouling caused by the dominant pollutants was investigated.The main conclusions are as follows:(1)First,EVOH ultrafiltration membrane was used to carry out the macroscopic membrane fouling experiment of the three pollutants,and the results showed: after the120 min contaminant filtration,the flux reduction rates of BSA,SA and HA were44.2%,56.0% and 65.7%,while the flux recovery rates were 79.4%,66.5% and 47.6%.Combined with the removal efficiency,it was found that HA pollutants were more likely to be entrapped,and the membrane flux was greatly attenuated and irreversible fouling,and SA followed.By contrast,BSA protein organic pollutants were not easily trapped by the EVOH ultrafiltration membrane,so the corresponding membrane fouling rate and irreversible pollution were the least.So for the EVOH ultrafiltration membrane,humic organic matter is dominant membrane contaminants,and its anti-pollution properties of protein-like organic matter is better.(2)The mechanism of contamination of EVOH ultrafiltration membrane by BSA,SA and HA was investigated by atomic force microscopy combined with dissipative quartz crystal microbalance.It was found that the difference of microscopic interaction between EVOH ultrafiltration membrane with the pollutants was the main reason for the difference of membrane fouling.The forces of HA-EVOH was the strongest in the three kinds of pollutants,reached to 1.09 m N/m,which increased the accumulation rate of HA on the membrane surface,and formed dense HA pollution layer on the membrane surface,and the corresponding membrane fouling was aggravated.While the interaction between EVOH-SA is centered,and the adsorption and accumulation of SA on the membrane surface is lower than that of HA.The forces of BSA-EVOH was the least,0.68 m N/m,which mainly because the BSA contains a large number of amino functional groups,and it has a weak binding with EVOH,so BSA is not easy to adsorb on the EVOH membrane surface,the formation of a more loose BSA adsorption layer,the corresponding membrane of the weakest.(3)At last,for the EVOH advantage membrane contaminants HA,we investigated the effects of Mg2+ on the EVOH membrane fouling behavior of it through the macro combination of micro analysis.It was found that the effects of Mg2+ on HA fouling were in two stages: at the lower Mg2+range,the fouling rate and fouling amplitude increased with the increase of Mg2+,it was because as the increas of the Mg2+,the net charges of EVOH and HA surface were reduced because of the charge screening and complex bridge and this weaken the electrostatic repulsion of EVOH-HA and HA-HA,thus a higher deposition rate of HA was accumulated and a denser HA layer was formed on the membrane surface,so the membrane fouling aggravated.However,when Mg2+dosage above a critical value,the fouling rate and fouling amplitude decreased with the increase of Mg2+,it was because in the high Mg2+ conditions,the hydration repultion forces were provoked effectivity,which caused a decrease in the deposition rate and extent of HA onto the membrane surface,and more nonrigid HA layer was formed,corresponding membrane fouling was mitigated.