Preparation And Application Of Organic-inorganic Hybrid Functional Ultrafiltration Membrane Based On Hydrotalcite-like

Synthetic dyes such as acid red（AR）,orange II（AO7）and orange G（OG）are the common pollutants in industrial wastewater,which are difficult to remove by traditional biological treatment technology.Advanced sulfate oxidation process can effectively remove various complex pollutants,but SR-AOPs technology is easy to cause secondary pollution and difficult to recover catalyst.Membrane technology helps SR-AOPs technology to overcome the above shortcomings.The catalytic membrane prepared by doping catalyst and membrane has dual functions of filtration and catalysis,which is helpful to realize self-cleaning of membrane and reuse of catalyst.In order to solve the problems of catalyst deactivation and membrane permeation reduction in catalytic membranes,a novel composite membrane and its catalytic oxidation performance were studied in this paper.The main contents are as follows:（1）A series of Co-based and Mn-based LDHs were prepared by co-precipitation method and Co-Ni LDHs were mainly studied.The products were characterized by FTIR,XRD,SEM,TEM,EDS,etc.The specific surface area and pore volume of Co-Ni LDHs were relatively large.Co-Ni LDHs were used to assist PMS to degrade the simulated printing and dyeing wastewater.When the catalyst dosage was 0.02g/L,the removal rates of AR,AO7 and OG could reach 100%,98.19%and 99.55%,respectively.In the process of AR degradation,the removal efficiency of AR was related to catalyst dosage,PMS dosage,initial p H,inorganic anions and natural organic matter.According to the free radical trapping experiment and XPS analysis of the reaction mechanism,it was found that SO₄^·-,·OH,¹O₂ and O₂^·-radicals were generated in the reaction system,of which ¹O₂ and O₂^·-were dominated and the metal ions were oxidized reduction reaction.The catalytic effect is better after repeated use.（2）In order to improve the ion leaching of Co-Ni LDHs,increase the permeation flux and increase the service life of the membrane,this paper uses the PES membrane as the raw material,the Co-Ni LDHs catalyst was immobilized in the membrane by the coprecipitation technique to form LDHs/PES composite membrane.The membrane structure,pore size,mechanical properties and stability were analyzed by FT-IR,XRD,SEM,dry and wet membrane gravimetry,universal material testing machine and thermogravimetric analysis.Thereafter,the water flux,rejection rate,anti-fouling and anti-ion leaching properties of the LDHs/PES membrane were further analyzed.The results showed that LDHs catalyst can improve the hydrophilicity and anti-fouling properties of the membrane,the leaching amount of ions from LDHs/PES Co 3.88 mg·L^-1,Ni 2.01 mg·L^-1)was much lower than that of LDHs(Co 0.08 mg·L^-1,Ni 0.14 mg·L^-1).In the Co-Ni LDHs/PES catalytic degradation system of AO7,when the catalytic membrane contains 4.76wt%LDHs,the dosage of PMS was 1 mmol·L^-1,the dosage of AO7 was 0.05 mmol·L^-1,96.58%of AO7 can be removed within 20 min and the mineralization rate reaches 54.76%,the mineralization rate of the composite membrane was much higher than that of Co-Ni LDHs（50.29%）.According to the free radical trapping experiment and XPS analysis of the reaction mechanism,it was shown that SO₄^·-,SO₄^·-,¹O₂ and O₂^·-,Co（Ⅲ）/Co（Ⅱ）,Ni（Ⅲ）/Ni（Ⅱ）were simultaneously produced in the reaction system Occurrence of redox reaction,after repeated use four times,the composite membrane still has high stability.（3）In order to improve the anti-fouling performance of PES membranes and reduce the erosion effect of inorganic nanomaterials on organic membranes,biochar composite hydrotalcites（OBC-LDHs）were prepared and doped into PES membranes to form OBC-LDHs/PES composite membranes.The structure of OBC-LDHs catalyst was characterized by FT-IR,XRD,SEM and the membrane structure,morphology,porosity,mechanical properties and stability were analyzed by FT-IR,XRD,SEM,universal material testing machine and thermogravimetric analysis.Studies have shown that OBC-LDHs can increase the hydrophilicity,elongation at break and thermal stability of PES membranes.With the increase of OBC-LDHs content,the membrane water flux increases,the rejection rate decreases and the anti-fouling performance improves.When the catalytic membrane contains 5.88wt%OBC-LDHs,the dosage of PMS was 1 mmol·L^-1,the dosage of OG was 0.05mmol·L^-1,98.47%of OG can be removed within 20min,the mineralization rate reached 53.26%.The ion leaching of OBC-LDHs/PES(Co 0.04 mg·L^-1,Ni 0.06 mg·L^-1)was much lower than that of LDHs(Co 3.88 mg·L^-1,Ni 2.01 mg·L^-1)and OBC-LDHs(1.75 mg·L^-1,1.24mg·L^-1),the composite membrane still has good stability and reusability after repeated use for four times.According to the free radical trapping experiment and XPS analysis,SO₄^·-and ¹O₂ radicals were generated in the reaction system,of which ¹O₂ was the main active species.