Preparation And Separation Palladium Properties Of Palladium Ion Imprinted Blend Membrane

Palladium(Ⅱ),as a rare platinum group precious metal element,is widely used in various fields due to its excellent physical and chemical properties.In addition,Pd(Ⅱ)in palladium-containing wastewater must be separated and recycled for environmental protection and sustainable development purposes due to its rare crustal reserves than aurum and biological toxicity.Pd(Ⅱ)in aqueous solution can be separated and recovered by conventional separation methods,but these methods generally lack the ability to selectively separate,while the emerging ion-imprinting technology can solve this problem well.To this end,a novel palladium(Ⅱ)ion-imprinted membrane(Pd(Ⅱ)-ⅡM)based on the amphiphilic block copolymer was prepared in this paper,which combined the ion-imprinting technique with the membrane separation technique.In this paper,a novel polysulfone-based amphiphilic triblock copolymer poly(4-vinylpyridine)-b-polysulfone-b-poly(4-vinylpyridine)(P4VP-PSF-P4VP)was synthesized by reversible addition fragmentation chain transfer(RAFT)polymerization.And the synthesis conditions(initiator:macromolecular chain transfer agent:monomer=1:5:500/1000/2000)in the RAFT reaction is changed to synthesis three block copolymers(BCP1,BCP2 and BCP3).Finally,the synthesized polymers were characterized by hydrogen nuclear magnetic resonance spectra(~1H NMR),Fourier infrared spectroscopy(FTIR),thermogravimetric analysis(TGA)and gel permeation chromatography(GPC).Then P4VP-PSF-P4VP was used as membrane-based material,and polysulfone(PSF)as an additive to prepare P4VP-PSF-P4VP/PSF blend membrane by self-assembly non-solvent induced phase separation(SNIPS).At the same time,composition conditions of different casting solution,which includes three types of BCPs prepared under different blending ratios of P4VP-PSF-P4VP/PSF,were set to explore their effects on the structural properties of the membrane.And membranes were characterized by scanning electron microscopy(SEM),atomic force microscopy(AFM),static/dynamic water contact angle,pure water flux and adsorption capacity of each membranes.It was found that the blend membrane(M6)prepared by BCP3 at blending ratio of 70/30 has excellent properties and spongy membrane structure.Furthermore,static adsorption experiments showed that p H had a great influence on the adsorption of membrane,and it reached a maximum adsorption of 103.1 mg/g at p H=2.M6 was used to separate the simulated Pd(Ⅱ)-containing wastewater,and various factors such as influence of flow rate,cations and anions on the separation performance of Pd(Ⅱ)were investigated.It was found that the flow rate at the range of 1-12 m L/min and cations had no significant effect on separation performance,while anions had certain influence on separation performance,and the effect degrees were different with different anions.In addition,M6 was found to have good recyclability by repeated regeneration experiments.Furthermore,actual electroplating wastewater separation was experimented by M6 and its actual industrial application simulation was carried out,which found that M6 is of high practical value and industrial application possibility.On the basis of P4VP-PSF-P4VP/PSF blend membrane,P4VP-PSF-P4VP and Pd(Ⅱ)were used to prepare metal-polymer complexes(MPCs),which were blended with PSF at the ratio of MPCs/PSF=70/30 to prepare membrane by self-assembly non-solvent induce phase separation(SNIPS)method.And,Pd(Ⅱ)ion-imprinted membrane(Pd(Ⅱ)-ⅡM(M8))was obtained by eluting Pd(Ⅱ)in the membrane with acidic thiourea.After SEM characterization,it was found that the ion imprinting process had little effect on membrane structure.After a series of adsorption experiments,Pd(Ⅱ)-ⅡM(M8)is proved to have a higher adsorption capacity than NIM(M8).Moreover,its adsorption process is more in line with Langmuir isotherm adsorption model and pseudo-second-order model.The theoretical equilibrium adsorption capacity is 149.2 mg/g,which belongs to homogeneous monolayer adsorption process and chemical adsorption process.In addition,Pd(Ⅱ)-ⅡM(M8)maintains high selectivity to Pd(Ⅱ)under interference of Cu(Ⅱ)and Ni(Ⅱ).Pd(Ⅱ)-ⅡM(M8)has efficiently separated single Pd(Ⅱ)solution,which exhibits excellent Pd(Ⅱ)retention capacity.And it also has good recyclability with the loss of only 8.02%after eight regeneration cycles.In addition,polystyrene-poly(4-vinylpyridine)(PS-P4VP)was synthesized by RAFT polymerization.Then PS-P4VP as an additive,and PSF as membrane-based material were used to prepare PS-P4VP/PSF blend membrane via SNIPS method.And different PS-P4VP addition ratios were set to explore its effect on the structural properties of blended membrane.On this basis,PS-P4VP and Pd(Ⅱ)were prepared into MPCs and blended with PSF at the ratio of MPCs/PSF=20/80 to form Pd(Ⅱ)ion-imprinted membrane(Pd(Ⅱ)-ⅡM(M-20-2)).The synthesized polymer was characterized by ~1H NMR and FTIR,and the membrane was characterized by SEM,X-ray energy dispersive spectrum(EDS),static/dynamic water contact angle and pure water flux.It was found that addition of PS-P4VP greatly improved hydrophilicity and pure water flux of the membrane.The imprinting process had little influence on the structure of ion-imprinted membrane and did not cause collapse or defect of membrane structure.Then,a series of adsorption experiments were carried out using Pd(Ⅱ)-ⅡM(M-20-2)and NIM(M-20-1),and it was found that adsorption effect was best under the condition of p H=2,which was consistent with previous results.Both Pd(Ⅱ)-ⅡM(M-20-2)and NIM(M-20-1)are more in line with the Langmuir isotherm adsorption model and pseudo-second-order model,which are of homogeneous monolayer adsorption processes and chemical adsorption process.When 10 mg/L single Pd(Ⅱ)solution was separated,Pd(Ⅱ)-ⅡM(M-20-2)did not penetrate until it was filtered for 35 min.Finally,recyclability study was carried out.It was found that the adsorption capacity of Pd(Ⅱ)-ⅡM(M-20-2)only decreased by 7.28%after 5 cycles compared with the result of first time.