Study On Ascorbic Acid Improving The Antifouling Performance Of Ce/Fe/PVDF Membrane

Membrane fouling will block membrane pores,reduce separation efficiency and hinder the development of membrane technology.The purpose of this study is to prepare a heterogeneous Fenton antifouling membrane,and introduce ascorbic acid（AA）to further improve the Fenton reaction efficiency,degrade the pollutants intercepted by the membrane,and improve the antifouling performance of the membrane.Firstly,MIL-100（Fe）and Ce-MOF,two heterogeneous Fenton catalytic materials,were mixed into polyvinylidene fluoride（PVDF）to prepare Ce/Fe/PVDF antifouling membrane.The synergistic effect of the two MOF materials in the catalytic reaction process gave the membrane excellent heterogeneous Fenton catalytic performance;Secondly,ascorbic acid（AA）was introduced into the following two membrane operation modes:（1）first pollution and then cleaning mode:after continuous filtration of wastewater,the polluted membrane is intermittently cleaned with H₂O₂-AA solution;（2）Degradation while running mode:First add H₂O₂-AA into the feed liquid,and then conduct membrane filtration to explore the feasibility of AA promoting membrane antifouling performance.Finally,the mechanism of membrane antifouling mechanism is studied,and the specific conclusions are as follows:（1）Ce/Fe/PVDF composite membrane（FCM）was successfully prepared by immersion phase inversion precipitation technology.Through characterization,it was found that MIL-100（Fe）and Ce-MOF were evenly distributed in the membrane.Compared with single PVDF membrane,the performance of FCM membrane was improved.（2）In the mode of sequential filtration and cleaning,the water flux recovery rate（FRR）and reversible pollution rate（R_r）of FCM polluted by acid red 73（AR73）after cleaning in H₂O₂-AA are significantly higher than those of FCM cleaned by water or in solutions only containing H₂O₂ or AA.This is because the reductivity and chelation of AA can promote the cycle of Fe³⁺/Fe²⁺and Ce⁴⁺/Ce³⁺,accelerate the decomposition of H₂O₂,and efficiently degrade pollutants.In addition,FCM has good antifouling performance to methylene blue（MB）,cationic blue X-GRL,acid orange 74（AO74）and bovine serum albumin（BSA）.15 cycles of operation proved that FCM has good reusability.（3）In the coupled operation mode of simultaneous filtration and degradation,the membrane has better separation performance due to the synergistic effect of heterogeneous Fenton reaction and membrane separation.When treating AR 73 solution containing H₂O₂-AA with FCM,the flux and retention rate were increased by 51%compared with the single FCM filtration,and the retention rate was 100%.The dye in the solution is concentrated on the membrane through the interception of the membrane,which greatly increases the dye concentration.Then,the Fe and Ce on the membrane are used to conduct heterogeneous Fenton reaction with H₂O₂-AA,so as to efficiently degrade the pollutants in the filtration process and alleviate the membrane pollution.BSA,cationic dyes（MB,CBX）and anionic dyes（AO74）were used as model pollutants to prove the applicability of the antifouling performance of the coupling system.10 times of coupled filtration experiments show that FCM has long-term operation stability.（4）Taking the secondary effluent of wastewater biochemical treatment as the model pollutant,the treatment conditions of two modes of wastewater treatment,namely,sequential filtration and cleaning and simultaneous filtration and degradation,were compared.The results show that the system of first fouling and then cleaning can effectively restore the mold performance,save oxidants and prolong the service life of the membrane.The system has good decontamination and antifouling efficiency,high operation efficiency and good stability.（5）The mechanism research experiment shows that ¹O₂ is the key active free radical for the degradation of pollutants in the system.The strong reducibility of AA can effectively reduce Fe³⁺and Ce⁴⁺in the system.At the same time,its chelation greatly reduces the redox potential of Fe³⁺/Fe²⁺and Ce⁴⁺/Ce³⁺cycles,thus enhancing the reaction between H₂O₂ and the two cycles.At the same time,it was found that organic alcohol,as a quenching agent of hydroxyl radical,could significantly promote the degradation of pollutants in the system.In this research system,polyvinyl alcohol（PVA）in printing and dyeing wastewater can effectively promote dye degradation.In this study,the synergistic effect of MIL-100（Fe）and Ce-MOF is used to endow the Ce/Fe/PVDF composite membrane with excellent heterogeneous Fenton catalytic performance,and AA is introduced in the Fenton reaction process to build an efficient heterogeneous Fenton system of AA-H₂O₂-membrane,which can improve the efficiency of pollutants degradation,thus making the membrane have excellent antifouling performance,and is expected to provide a new way to reduce membrane pollution.