Preparation Of Magnetic Molecularly Imprinted Polymer And Its Application In Membrane Fouling Mitigation

Membrane bioreactor(MBR)has many advantages such as good effluent quality,small equipment footprint,high treatment efficiency,and etc.It is widely used in wastewater treatment and reuse.However,the problems of flux decline and operating cost increase caused by membrane fouling have severely limited the larger-scale application of MBR.The addition of adsorbents such as activated carbon can improve the characteristics of the mixed liquid in the MBR and effectively mitigate membrane fouling.However,most of the existing adsorbents is not selective,which will greatly reduce the adsorption efficiency and increase the operation and maintenance costs.The development of nanotechnology and surface molecular imprinting technology has made a substantial breakthrough in the preparation and application of molecularly imprinted polymers(MIPs)for biological macromolecules.It is promising to improve the poor selectivity of existing adsorbents.This topic is to prepare the magnetic molecularly imprinted polymers,and selectively adsorb the membrane foulants.It is aimed to explorethe feasibility and mitigating fouling mechanism of magnetic MIPs,which will provide enough information of mitigating membrane fouling in MBR by magnetic activated sludge process.by.The main contents are as follows:(1)A single-template magnetic protein molecular imprinting polymer of Fe₃O₄@Si O₂@C=C@MIPs was prepared using surface molecular imprinting technology with double bond modified magnetic nanoparticles as a carrier,acrylamide and N-isopropylacrylamide as functional monomers,and bovine serum albumin(BSA)as a template molecule..The results indicated that the saturated adsorption capacity of Fe₃O₄@Si O₂@C=C@MIPs is 34.5 mg/g,and the imprinting factor is between 2.09 and 2.12.The adsorption fits better to the Langmuir isotherm and follows the pseudo-second-order model.The adsorbent of Fe₃O₄@Si O₂@C=C@MIPs showed the better selectivity for BSA.In addition,It remained high adsorption capacity around 30 mg/g after 5 adsorption-desorption cycles,suggesting good reusability.(2)A single-template magnetic protein molecular imprinting polymer of Fe₃O₄@Si O₂@NH₂@MIPs was prepared and evaluated with amino functionalized magnetic nanoparticles as carriers.It is found that the saturated adsorption capacity of Fe₃O₄@Si O₂@NH₂@MIPs is 45.6 mg/g and the imprinting factor is around 2.2.However,the specific adsorption capacity of bovine hemoglobin(BHb)is small,and the specific adsorption capacity of lysozyme is high,which may be due to the small molecular size of lysozyme and the small steric hindrance into the imprinting site.At the same time,the surface of lysozyme is positively charged,while the surface of magnetically imprinted microspheres is negatively charged,and therefore electrostatic attraction provides benefit.(3)A double-template magnetic protein molecular imprinting polymer of Double-MIPs was prepared with BSA and BHb as double templates.Compared with the double template protein solution,the adsorbent of Double-MIPs indicates a higher adsorption capacity in the single template protein solution than that of mixed solution,possibly due to the competitive adsorption in the mixed solution.It can be seen from the adsorption kinetics and adsorption isotherms that the saturated adsorption capacities of BHb and BSA are 104.4 mg/g and 37.8mg/g,respectively,and it can be speculated that Double-MIPs has a higher affinity for BHb.(4)For membrane filtration resistance tests,the main membrane foulant of dissolved organic matter(SMP)form a MBR was applied to investigate the specific adsorption performance of the 3 molecularly imprinted polymers.The adsorption capacity of all the three imprinted adsorbents for SMP protein was significantly higher than that of polysaccharides,indicating good adsorption selectivity.At the same time,the reduction of membrane filtration resistance by imprinted adsorbents is significantly higher than that of non-imprinted adsorbents.Also,the highest membrane filtration resistance reduction ratio can reach 37.27%.These show that magnetic molecularly imprinted adsorbents can effectively mitigate membrane fouling through specific adsorption.In addition,the excellent magnetic response characteristics make sure of rapid separation from the mixed solution.