Study On Preparation Of FePc Modified PVDF Catalytic Membrane And Its Separation Property In Dye Aqueous Solution

Nowadays,the world is facing the environmental problems of insufficient water resources and serious water pollution.Dyeing effluents from textile industry are considered to be one of the most difficult industrial wastewater to purify,because its largevolumesof heavily pollutivewastewaters with highcolourity,containing complicated components.Under the severe situation,membrane separation technique,as a method of separation,purification,cleansing and concentration with high-efficiency,energy saving,simple operation and reliable running,has attracted increasing attention.PVDF is one of the most promising membrane materials for the fabrication of ultrafiltration?UF?and microfiltration?MF?membrane for industrial application owing to its high mechanical strength,good thermal stability and chemical resistance as well as film-forming properties compared to other commercialized polymeric materials.However,the intrinsic hydrophobic property of PVDF materials results in low water permeability and severe membrane fouling when treating an aqueous solution containing organic,colloidal matters,and biological substances,which are susceptible to adsorption and deposition onto the membrane surface,blocking the surface pores.As aforementioned drawbacks of PVDF membranes,it is generally accepted that an increase in hydrophilicity through the incorporation of nanoparticles to impart the antifouling property of the membrane.Unfortunately,the improvement in membrane hydrophilicity and resistance to membrane fouling is limited due to the agglomeration of nanoparticles.In this work,Iron phthalocyanine?FePc?with a bioinspired catalytic function as modifier,was innovatively incorporated using three different technique routes?blending,grafting and coordinating?into the PVDF matrix to fabricate PVDF composite membrane.Utilizing FePc is soluble in DMAc to form a homogeneous mixture with PVDF,a novel modified strategy is proposed to prepared modified PVDF membrane with improved water permeability and excellent antifouling properties and catalytic self-cleaning function.ATR-FTIR spectroscopy,XPS,SEM,contact angle measurement and streaming potential analysis were employed to characterize the chemical composition,morphological structure,wetting and surface charge of PVDF composite membranes.Cross-flow filtration tests using BSA as a protein model was allowed for the evaluation of the permeation flux,foulants rejection and antifouling properties of the resulting membranes.The separation performance and catalytic self-cleaning ability of the optimized membrane were discussed in the filtration of oil/water emulsion and dyes aqueous solution.It was found that the composite membranes modified by FePc exhibited the improved properties of hydrophilicity,porosity,pore size and negative charge of PVDF membrane and endowed the catalytic self-cleaning function of PVDF membrane which can degrade thoroughly the adsorbed organic pollutants on the surface or trapped within the membrane pore,which has a development potential of practical application and research significance.The main research results are as follows:?1?By measuring the viscosity of the casting solutions with different concentration PVDF and investigating pure water flux,BSA rejection ratio and antifouling properties of corresponding to PVDF membranes.It can be found that the easy film-forming,enhanced pure water flux and BSA rejection ratio of PVDF membrane when the concentration is 15%in casting solution.The research results present the viscosity change is not obvious under the incorporation 1⁴%FePc into the casting solution of15%concentration at 20°C,implying the addition of the modifier no more than 4%.?2?We innovatively incorporated an environmentally friendly FePc into the PVDF matrix to fabricate a FePc/PVDF composite membrane through blending modified technique.It was found that the introduction of Fe Pc in PVDF membrane matrix resulted in improved porosity,mean pore size,surface hydrophilicity and negative charge of as-prepared composite membranes,and thereby enhanced membrane permeability and antifouling property.The experimental results show that the pure water flux of the composite membrane has been increased from 63.37 L m^-2h^-1?the pristine PVDF membrane?to 158.94 L m^-2h^-1.The flux recovery ratio?FRR?of the composite membrane has been also enhanced,the largest increase is 98.90%compared to that?38.67%?of the pristine PVDF membrane.Although the BSA retention rates of the FePc/PVDF composite membranes decrease with increasing the FePc content,the lowest retention rate still exceeds 92.1%.In addition,The FRR of 100%for the membrane fouled by oil contaminants was acquired after the membranes were impregnated in H₂O₂ solution in the oil/water emulsion separation.This suggests that a FePc/PVDF composite membrane with remarkable water permeability,excellent antifouling property and catalytic self-cleaning capability has been achieved successfully.The composite membrane was applied in the separation of the aqueous solution of disperse dyes.A filtration mechanism of adsorption-accumulation-dynamic membrane was proposed for the membrane separation of water-soluble dyes.What's more,the composite membrane exhibited high-efficiency separation performance and significant catalytic self-cleaning ability in treating the aqueous solution of disperse dyes.?3?By nucleophilic addition reaction and amination reaction,Ethylenediamine?EA?and Trimesoyl chloride?TMC?were successively grafted onto PVDF backbone,and then the obtained products were fabricated PVDF-g-EA and PVDF-g-EA-TMC composite membranes via non-solvent induced phase separation technique,respectively.The permeation flux and fouling resistance of the resulting membranes were evaluated using cross-flow filtration test to optimize the reaction concentration and reaction time of EA and TMC.It was found that 5%EA reacted 30 min and 1.0%TMC reacted 10min to prepare the composite membrane with the best separation performance.PVDF-g-EA-TMC-FePc composite membrane was prepared successfully via grafting ethylenediamine on alkaline-treated PVDF backbone followed though the amidation reaction with 4-NH₂-Fe Pc in the preparation process of casting solution.The composite membrane exhibits remarkable permeate flux(218.05 L m^-2h^-1)and excellent antifouling performance,and its FRR reaches 90.25%.Owing to grafting FePc on PVDF chain,the composite membrane was endowed with catalytic self-cleaning ability.It was found that the composite membrane presents outstanding removal efficiency and catalytic self-cleaning ability in treating wastewater containing Congo red,and the FRR of 93.2%for heavily-fouled membrane was obtained successfully.?4?A novel modifier was facilely designed and architecturally built through grafting4-aminopyridine?4-APy?followed by axial coordinating iron phthalocyanine?FePc?on PVDF.An original PVDF-g-Py-FePc/PVDF composite membrane has been successfully developed using the phase inversion technique via supplementing the resulting modifier PVDF-g-Py-FePc into PVDF matrix.The pure water flux of the composite membrane was nearly 2.72 times as great as that of PVDF membrane,reaching 172.54 L m^-2h^-1.97.40%flux recovery ratio of the fouled membrane after hydraulic cleaning for 30 min was achieved,whereas the pristine membrane only reached 38.67%recovery.In addition,the composite membrane exhibited high-efficiency separation performance and significant catalytic self-cleaning ability in treating oily wastewater.Specifically,the permeate flux of 132.50 L m^-2h^-1and the oil rejection ratio of 94.40%for the composite membrane were obtained in oil/water separation.The FRR of 98.58%for the membrane fouled by oil contaminants was acquired based on advanced catalytic degradation mechanism through decomposing H₂O₂ to generate·OH radicals in the presence of the Fenton-like modifier PVDF-g-Py-FePc.The outstanding removal efficiency of disperse dyes and the excellent antifouling performance of the composite membrane were achieved in the filtration process of the aqueous solution of disperse dyes,suggesting its extensive application value in the treatment of printing-dyeing wastewater.