Study On Modification Of Porous α-Al₂O₃ Ceramic Membranes And Their Oil-water Separation Performance

The production of oily wastewater in oil field exploitation,petrochemical and other industrial processes is huge.If it was not properly treated,it would seriously threaten the safety of agricultural soil and water environment and human health.In particular,emulsified oil with steady physical and chemical properties in oily wastewater brought great challenges to the traditional oil-water separation technology.Membrane separation technology,especially ceramic membrane technology,had gradually become a research hotspot in the field of oily wastewater treatment due to its high mechanical strength,good corrosion resistance,high separation efficiency and no secondary pollution.In this paper,α-Al₂O₃ ceramic membrane was used as the original membrane.Two kinds of modified ceramic membranes were prepared by selecting iron（Ш）nitrate nonahydrate and silicon dioxide nanoparticles,and applied to the oil-water emulsion separation experiment.The pure water flux,oil removal rate and flux recovery rate of the modified ceramic membrane were studied.The experimental results showed that the two kinds of modified ceramic membranes had great application potential in the oil-water separation field.The main research results are as follows:（1）Four different concentrations of iron（Ш）nitrate nonahydrate solution modified ceramic membranes were prepared by immersion method.The membranes were characterized by SEM,EDS Mapping and contact angle,and were applied to oil water emulsion separation experiments.According to the characterization of the contact angle and pore size distribution ofα-Al₂O₃ and modified ceramic membranes,increasing the concentration of iron（Ш）nitrate nonahydrate modified solution reduced the surface contact angle ofα-Al₂O₃ceramic membranes,improved their hydrophilicity,and gradually reduced the average pore size.Under the combined influence of hydrophilicity and pore size distribution,the pure water permeation flux of the modified（MF0.5）ceramic membrane was the highest when the concentration of the modified solution was 0.5wt%.Therefore,MF0.5 ceramic membrane was used for oil-water emulsion separation experiments.The results showed that the separation performance of the modified ceramic membrane was significantly improved,but the steady permeation flux was slightly reduced.When the transmembrane pressure difference（TMP）was0.07 MPa,and the feed liquid emulsified oil concentration was 1000 mg·L^-1,the emulsified oil rejection rate of MF0.5 ceramic membrane increased from 86.5%to 99.8%;The steady permeation flux decreased from 65 L·m^-2·h^-1 to 60 L·m^-2·h^-1.（2）In order to solve the problem of low steady permeation flux of MF0.5 ceramic membrane,usingα-Al₂O₃ ceramic membrane as the base membrane,silica nanoparticles modified ceramic membrane was prepared by ultrasonic immersion.α-Al₂O₃ and modified ceramic membranes were characterized by means of SEM,EDS Mapping,and contact angle,and were used for the separation of oil-water emulsions.Under the combined effects of surface hydrophilicity and pore size changes of the membrane,the pure water flux of the modified（MS0.5）ceramic membrane was the highest when the concentration of the silica nanoparticle modified solution was 0.5wt%.Therefore,the MS0.5 ceramic membrane was used as oil water emulsion separation experiment,the results showed that compared toα-Al₂O₃ ceramic membrane,the steady permeation flux of MS0.5 ceramic membrane was improved.When the TMP was 0.07 MPa and the feed liquid emulsified oil concentration was 1000 mg·L^-1,the steady permeation flux of MS0.5 ceramic membrane added from 65L·m^-2·h^-1 to 85 L·m^-2·h^-1.By comparing the performance of two modified ceramic membranes,it was found that the permeability of MS0.5 ceramic membrane was better than that of MF0.5 ceramic membrane;In terms of retention performance,MF0.5 ceramic membrane was better.（3）In order to solve the membrane fouling problem during the separation of two modified ceramic membranes,ceramic membrane cleaning experiments were conducted to study the flux recovery rate and anti-fouling performance of the two modified ceramic membranes.Compared withα-Al₂O₃ ceramic membranes,the flux recovery rate of MF0.5ceramic membrane was improved,and the flux recovery rate reached more than 90%under different concentration and TMP conditions;the flux recovery rate of MS0.5 ceramic membrane was also improved,up to 80%,and the proportion of irreversible pollution was significantly reduced compared withα-Al₂O₃ ceramic membranes.In view of the low flux recovery rate of MS0.5 ceramic membrane after hydraulic cleaning at 0.07 MPa,1000 mg·L^-1,the contaminated MS0.5 ceramic membrane under this condition was chemically cleaned.When SDBS+SDS combination was used for cleaning,the flux recovery rate of the modified ceramic membrane was more than 90%,which was the best cleaning method.Based on the cleaning experimental results of two modified ceramic membranes,the flux recovery rate of MF0.5 ceramic membrane could reach more than 90%after hydraulic cleaning.After chemical cleaning,the flux recovery rate of the MS0.5 ceramic membrane could reach more than 90%,so the two modified ceramic membranes had high potential and application prospects in the treatment of oil-water emulsion,and the application of this technology will have a far-reaching impact on protecting agricultural water and soil environment and human health and safety.