Preparation And Water Treatment Efficiency Of Isoporous Catalytic Ceramic Membrane

To cope with the challenges posed by pathogenic microorganisms and organic micro-pollutants in the process of wastewater reuse,a variety of physical-chemical coupled multi-stage advanced treatment processes have been widely used in advanced wastewater treatment.However,the coupling processes are cumbersome and time-consuming,occupying a large area with high investment costs,which gradually fail to meet the needs of the rapid urbanization development.In this study,an isoporous ceramic catalytic membrane with uniform pore size and high porosity was prepared,which could effectively remove bacteria,viruses and organic micro-pollutants from wastewater.The role of the isoporous structure on bacteria and viruses removal was verified.The effectiveness and mechanism of the isoporous catalysis for organic micropollutants degradation were systematically studied.The simulation technology was used to explore the mechanism of the nano-space confinement effect in isoporous structures.The effectiveness of isoporous ceramic catalytic membrane for real water treatment was also evaluatedFirst,the feasibility of the solvent evaporation-induced self-assembly（EISA）method to prepare isoporous alumina ceramic membranes（IAM）was verified.The IAMs were prepared by using PS-b-PEO block copolymer as the template and aluminum acetylacetonate as the aluminum source.The membrane preparation method and parameters were optimized,and the microstructure of the IAMs was characterized.Control over the pore structure of IAM was achieved by tailoring the PS segment of PS-b-PEO,leading to the pore size rise from 8.3 to 19.7 nm.The selective separation performance of IAMs was evaluated using gold nanoparticles（5-37 nm）and proteins（lysozyme,ovalbumin,bovine albumin serum and human immunoglobulin）.Subsequently,the preparation of isoporous La₂Co Mn O_6-δperovskite phase catalyst（ILCMO）was explored by using the EISA method.The preparation parameters were optimized by testing the pore structure,crystal structure and catalytic performance of the catalyst.Based on the improvement of IAM and ILCMO preparation technologies,isoporous Al O_x/La₂Co Mn O_6-δcatalytic ceramic ultrafiltration membrane（IAPUF）was prepared.The heterogeneous structure of IAPUF was systematically studied and characterized.The pure water permeability of IAPUF was 318.1±16.9 L·m^-2·h^-1·bar^-1,which was higher than that of a commercial ceramic membrane（CM100）of 237.5±4.7L·m^-2·h^-1·bar^-1.The filtration experiments on bacteria and MS2 phage viruses showed that IAPUF could completely remove bacteria and viruses from the water by pore size sieving.Secondly,the organic micro-pollutants degradation in IAPUF/PMS membrane catalysis system was systematically investigated.The mechanism of organic micro-pollutants degradation in ILCMO/PMS was studied by X-ray photoelectron spectroscopy（XPS）and electron spin resonance（ESR）.The ILCMO/PMS catalytic oxidation system mainly generated four active species:sulfate radical(SO₄^·-),hydroxyl radical（^·OH）,singlet oxygen（¹O₂）and superoxide radical(O₂^·-).Among them,SO₄^·-and^·OH were the most important active species for the degradation of organic micro-pollutants.The Co on the surface of ILCMO was the most dominant active site for catalyzing the decomposition of PMS to generate free radicals.The performance of the IAPUF/PMS membrane catalytic system was studied.Four common organic micro-pollutants,atrazine（ATZ）,carbamazepine（CBZ）,phenol（Phenol）and sulfamethazine（SMZ）,were used as the target pollutants.The effects of operating pressure and PMS concentration on the degradation efficiency of the targets were investigated,and the kinetics of the related oxidation reaction was analyzed.The results showed that the IAPUF/PMS system could rapidly degrade organic micropollutants in a very short time(～4×10^-3 s)under optimal operating conditions.The residual amounts of ATZ,CBZ,Phenol and SMZ in the filtration water were 2%,10%,1%and 2%of the feed water,respectively.It could be concluded that IAPUF/PMS membrane catalytic system could quickly and effectively remove organic micro-pollutants in water samples.To further explore the dynamic mechanism of the organic micro-pollutants degradation by the IAPUF/PMS membrane catalytic system and the influence of the membrane isoporous structure on the catalytic reaction.COMSOL Multiphysics software was used to establish the mathematical model of the pore channels in IAPUF.The catalytic reaction was also simulated by the software.The parameters of the fluid field and chemical reaction field were calibrated by comparing them with the experimental data,respectively.The concentration distributions of PMS,SO₄^·-,^·OH and Phenol in the isoporous channel were calculated based on the related mechanisms investigated in the previous chapter.The results showed that the diffusion distance of SO₄^·-and^·OH was greatly shortened due to the nano-scale pore channels of IAPUF.This reduced the consumption of free radicals in the diffusion process and formed a higher concentration of free radical domains in the pore space.Simultaneously,organic micropollutants rapidly entered the free radical domains of the nanopores under pressure-driven.With the combined effect of pressure-driven high mass transfer and the nano-space confinement effect,the organic micro-pollutants were rapidly degraded in the pore channels of IAPUF.Finally,the secondary effluent was used as the actual background water.The Escherichia coli,MS2 phage virus and SMZ were used as targets for IAPUF/PMS system evaluation,respectively.The efficiency of the IAPUF/PMS membrane catalytic system in the advanced treatment of wastewater reuse was evaluated versus single commercial membrane filtration（CM100-F）,single homogeneous membrane filtration（IAPUF-F）,single oxidation（PMS-S）,ILCMO catalytic oxidation（ILCMO/PMS）,and the combined of ILCMO catalytic oxidation and inert homogeneous membrane filtration（ILCMO/PMS/IAUF）treatment,respectively.The results showed that IAPUF/PMS system could completely remove bacteria,viruses and organic micro-pollutants in water samples.Moreover,IAPUF/PMS was effective in removing DOC,UV₂₅₄ and fluorescent organics.This result indicated that IAPUF/PMS membrane catalytic water purification technology exhibited a promising potential in wastewater advanced treatment.