Research On Fouling And Control Of Ultrafiltration Membranes Based On Microscopic Interfacial Forces

UF membrane has become the core of the third generation drinking water treatment technology.However,membrane fouling had been a major obstacle for broader promotion and implementation of UF.As a new and more intuitive method of assessing the potential of membrane fouling,the technique that uses interaction forces of membrane-foulant and foulant-foulant to evaluate membrane fouling has recognized by many scholars.However,this research was not in-depth,especially the feasibility of using interfacial force to evaluate irreversible membrane fouling and optimize the pretreatment process,and the scope of application of this evaluation method,which requires further understanding.This study uses typical model membrane fouling of humic acid(HA),sodium alginate(SA)and bovine serum albumin(BSA),and natural waters were employed as inlet water.The membrane fouling index(TFI)and the irreversible fouling index(HIFI)were used to evaluate the membrane fouling.The microscopic interface force of pollutant and the ultrafiltration membrane were used to a structure-activity relationship with the total membrane pollution,or irreversible membrane pollution was analyzed.On this basis,the effect of the nature of organic pollutants on the structure of membrane fouling potential was explored.The feasibility of evaluating and optimizing the fouling control performance of the integrated "adsorption-UF" process using the microscopic interface force was discussed.Whether it was the single typical membrane pollutant or the complex system of natural water,from the analysis of correlations between foulant-membrane interfacial forces and membrane fouling,it was found that good correlation existed between foulant-membrane interfacial forces and TFI or HIFI,and significant correlation was observed between foulant-membrane interfacial forces concentration and HIFI.These results indicated that the foulant-membrane interfacial forces were more suitable for evaluating the irreversible membrane fouling.Model fitting indicates that microscopic interface force was suitable for evaluating membrane fouling behaviour,governed by cake filtration.Further analysis suggested that the change of molecular weight has little effect on the foulant-membrane interfacial forces.But functional groups with p Ka was larger than p H of the solution would bring large foulant-membrane interfacial forces,which would cause serious irreversible pollution;Interaction force of the hydrophilic component interaction was more vital than the forces of hydrophobic and transphilic component,thereby exacerbated membrane fouling.This could provide theoretical support for controlling the organic membranes fouling.In the integrated adsorption-UF process,no significant correlation was found between the membrane fouling mitigation performance and the particle size of the adsorbent.In comparison,the membrane fouling mitigation performance showed certain positive correlations with the removal performance of adsorbent Strong correlations between the membrane fouling mitigation performance and the interface force difference(between "pollutant-adsorbent" and "pollutant-ultrafiltration membrane"),correlation coefficient up to 0.9289.These results indicate that the interface force difference could be used to screen adsorbent particles.And this method helps to improve the membrane fouling control capability during the integrated "adsorption-UF" process.The research on MIEX shows that the adhesion force of pollutants-resin decreased with the increase in the saturation level of resin.When the saturation level of resin increased to about 70%,the resin would lose its positive effect on membrane fouling mitigation performance.Under good regeneration,resin regeneration had little impact on the "pollutant-adsorbent" interface force.The results suggested that for the integrated adsorption-UF process,the adsorption performance of the adsorption was not the only criterion to select.It was essential prerequisites that "Adsorption performance" and "stronger interfacial force between pollutants and adsorbents" for ensuring good effluent quality and ideal membrane pollution control effects in the integrated "adsorption-UF" process.