Research On Enhanced Cleaning Technology Of Ceramic Membrane Based On Multi Agent Cooperation

With the development of society,the problem of water shortage in China is becoming more and more serious.High-efficiency and low-consumption membrane separation technology has become a research hotspot in the field of wastewater recycling and reuse in my country.Compared with organic membranes such as PVDF,ceramic membranes have the advantages of corrosion resistance and stable structure.They are widely used in water treatment,environmental protection and other fields.However,the inevitable membrane pollution restricts the development of membrane technology.In order to ensure the water production of flat ceramic membranes To increase the efficiency and prolong the service life of the membrane,the membrane needs to be chemically cleaned.This research aims at the significant effect of acid washing on flat ceramic membrane flux recovery found in the previous research of the research group,which is different from the organic membrane acid washing effect.It focuses on the research of high-efficiency acid washing technology of flat ceramic membrane,and cooperates with alkali,oxidant and chelating agent.Mixtures,surfactants and other types of chemical cleaning agents,develop ceramic membrane enhanced cleaning technology based on multi-agent coordination,and perform microscopic characterization of the selected optimal cleaning agent combination through SEM characterization,contact angle characterization and other means to clarify its cleaning Mechanism to realize the efficient and stable operation of ceramic membranes.The research on the water treatment characteristics of the flat ceramic membrane shows that under the test conditions,the clear water flux of the flat ceramic membrane is positively correlated with the membrane pressure.Under the operating pressure of 15KPa,the clear water flux of the flat ceramic membrane is 200L/（m².h）,The critical flux of flat ceramic membrane to treat municipal secondary effluent is 98L/（m².h）.The cleaning technology used in this test is mainly physical cleaning combined with chemical cleaning.After physical cleaning,the average membrane flux recovery rate of flat ceramic membrane and PVDF membrane were 65.4%and 58.7%,respectively.During the experiment,the cleaning efficiency of chemical cleaning was investigated,and the ceramic film enhanced cleaning technology based on multi agent coordination was developed.The results show that the flux increment of H₂SO₄and H₂C₂O₄is 14.69%and15.75%respectively,compared with physical cleaning,and the cleaning effect is as follows:H₂SO₄>HCl>HNO₃,H₂C₂O₄（oxalic acid）>C₆H₈O₇（citric acid）>CH₃COOH（acetic acid）.For PVDF membrane,the flux increment of HCl and C₆H₈O₇was 13.83%and 25.56%compared with that of physical cleaning,and the cleaning effect was as follows:HCl>H₂SO₄>HNO₃,C₆H₈O₇>H₂C₂O₄>CH₃COOH.The change of membrane flux between the flat ceramic membrane cleaned by H₂SO₄and the PVDF membrane cleaned by HCl when the municipal secondary effluent is treated shows that when the flux of both membranes drops to the same level,the running time of the flat ceramic membrane is longer than that of the PVDF membrane.In the mixed cleaning,the combined cleaning effect of strong acid mixed with HNO₃is better than that of HNO₃alone,and the combined cleaning effect of weak acid mixed with CH₃COOH is better than that of CH₃COOH alone.The results of step-by-step cleaning test show that the step-by-step cleaning effect of H₂SO₄and HCl,H₂C₂O₄and C₆H₈O₇is lower than that of mixed cleaning for flat ceramic membrane.For PVDF membrane,the step-by-step cleaning effect of H₂SO₄+HNO₃is similar to that of HNO₃before H₂SO₄,while the step-by-step cleaning effect of H₂C₂O₄and C₆H₈O₇is slightly lower than that of mixed cleaning.The single-step,mixed and step-by-step cleaning effects of three cleaning agents（NaClO,NaOH and EDTA-Na₂）on flat ceramic membrane were studied.The results showed that the flux of flat ceramic membrane recovered to 118.75%of the initial flux after NaClO cleaning.The results show that the membrane flux of the cleaning method of H₂SO₄before NaClO,H₂C₂O₄before NaClO exceeds the initial flux of the ceramic membrane.The results of EDTA-Na₂and NaClO showed that the membrane flux of EDTA-Na₂before NaClO,NaClO before EDTA-Na₂and NaClO+EDTA-Na₂was 119.34%,88.59%and 60.84%of the initial membrane flux respectively.The experimental results of cationic surfactant DTAC and NaClO showed that the membrane flux of three different cleaning methods,NaClO before DTAC,DTAC+NaClO,DTAC before NaClO,recovered to 112.41%,60.36%and 55.55%of the initial membrane flux respectively.The results show that the results show that the long-term operation of ceramic film can reach 67.16%,63.41%and 65.38%respectively.SEM and contact angle characteristics also reveal that the long-term operation effect of the three cleaning methods is good,Then,three cleaning methods,namely H₂SO₄before DTAC,H₂C₂O₄before NaClO,NaClO before DTAC,are recommended as the optimal cleaning strategies for municipal secondary effluent treatment with flat ceramic membrane.