Preparation Of AFM Microparticle Probe And Application In PVDF Ultrafiltration Membrane Fouling Of Organic Matters

AFM (Atomic Force Microscope, AFM) have been widely used in materialsscience, life science and other fields, especially the application in the micro-forceparsing of membrane fouling, due to its advantage of high resolution, easy to operateand have no requirements with samples and test environment, etc. But mostresearchers all use carboxyl (-COOH), hydroxyl (-OH) functional groups or BSA toconducted AFM cantilever probe which will be used to measure the adhesion force,these functional groups used to simulate different types of pollutants, not only couldfully reflect their actual characteristics,but also have strict preservation and preparationof the test environment, also the functional groups were easily to react with otherpollutants in the test environment, and the production cost is high. Therefore, to furtherexplore the interaction between actual pollutant and polyvinylidene fluoride (PVDF)membrane, this study prepared the PVDF membrane material probe with physicalsintering method and melt adhesion method respectively, combined withlaboratory-made probe preparation device. And we also prepared different pollutantsprobe using the solution soak method on the basis of the PVDF membrane materialprobe. Humic acid (HA), sodium alginate (SA), bovine serum albumin (BSA) werechosen as different types of simulative pollutant and the secondary effluent dissolvedorganic matter (EfOM) of the forth sewage treatment plant as the actual pollutant and itwas determined segmentation of hydrophilic and hydrophobic substances, andmolecular weight distribution measurement. Both were conducted of membranefouling tests and adhesion forces measurement. The conclusions were as follows:(1)The size of PVDF microparticle probes prepared by physical adhesion method and sintered was5-20μm, the particle bonding strength of the probe size was able tomeet the actual operation requirements,.(2)Different simulated pollutants on PVDF ultrafiltration membrane flux decayorder: BSA> SA> EfOM> HA, adhesion test showed that the more severe flux decline,the greater the force between the film and the pollutants.The adhesion order was:BSA-PVDF> SA-PVDF> EfOM-PVDF> HA-PVDF;(3)The content of hydrophobic component was the highest, about51.1~54.5%,the hydrophilic component and weakly hydrophobic component content were quiteclose, for26.3~27.8%,19.2to21.1%, respectively. Membrane flux decline order:hydrophilic components> strong hydrophobic component> weakly hydrophobiccomponent;(4)The proportion of small molecules in the secondary effluent substances was thehighest, the distribution of different molecular weight for the three components weresimilar to that of secondary effluent organic matters, small molecules accounts a higherproportion, mainly in the range of <10ku, and molecules <3ku of hydrophilic organicmatters was nearly60%, significantly higher than the strong, weak hydrophobicorganic compounds and secondary effluent organics;(5)For the same component pollutants, the membrane-foulant forces are greaterthan the corresponding foulant-foulant force, which showed that the membrane-foulantforce was the key factor to control the PVDF membrane fouling. And the results of thefouling of different factions to the PVDF UF membrane showed that stronghydrophobic faction was the key factor in controlling PVDF membranes stableoperation of membrane fouling.