Research On The Application And Mechanism Of Polymer Inclusion Membranes Electrodialysis In Acid Concentrated And Vanadium Transport Separation

The industrial production process will generate a lot of wastewater containing waste acid and heavy metal,resulting in environmental pollution and waste of resources.Polymer Inclusion Membranes(PIMS),developed on the basis of Support Liquid membrane(SLMS),has become a hot spot in the study of transport and separation of metal ions and small molecular matter because of its good selectivity and stability.In this paper,waste acid and vanadium-containing wastewater was regard as target,and combined high selectivity and stability of PIMs with the electrodialysis's(ED)synergistic effect of electric field on ion transport and separation,in order to realize the efficient and selective transport of acid concentration and vanadium.In this paper,the influence of PIM membrane composition and structure on PIMED performance was investigated,and the influence of different process parameters on acid concentration performance and vanadium transport and separation was studied.At the same time,the mass transfer mechanism of vanadium in PIMs was deeply analyzed.The main research contents and conclusions are as follows:Three kinds of basic polymers were selected as the substrate and three kinds of ionic liquids were used as the carrier to prepare a variety of PIMs.XRD,FTIR and other characterization methods were used to preliminarily screen different PIMs.The results showed that the PIM based on cellulose triacetate(CTA)and polyvinylidene difluoropropene(PVDF-HFP)had better film forming state and more uniform surface.Among them,the two PIMs on PVDF-HFP substrate were partially crystallized films,while the two PIMs on CTA substrate were amorphous films.Polyethylene glycol dimethacrylate(PEG-DMA)was used as a crosslinking agent to improve the crystallinity of PIM films.By combining the prepared PIM with ED,the effects of different base polymers and different ionic liquids on the performance of concentrated acid were investigated.Then,the acid concentrated performance of cross-linked PIM using Cyphos IL 101 and Aliquat 336 as carriers was studied.The results showed that the acid concentration efficiency of CTA as the base polymer was significantly better than that of PVC and PVDF-HFP.Among them,the concentration efficiency of PIM acid prepared by using CTA as the base polymer and Aliquat 336 as the ionic liquid can reach 2.2 times,which achieves the hydrogen barrier effect compared with the commercial hydrogen barrier membrane,and the membrane resistance is lower.CTA based PIM and PEG-DMA through covalent bond for chemical cross-linking,the film has higher crystallinity,the film is more"compact",which helps to further improve the ion transport efficiency and reduce proton leakage.PIM-ED was used for vanadium separation and recovery,and the effects of different substrates and carriers,electric field intensity,initial concentration of feed liquid,p H and other factors on vanadium transport were investigated.The results showed that the combination of PVDF-HFP and AQUAT 336 has obvious advantages in the transmission of V(V).In a moderate viscosity range,the larger the proportion of Aliquat 336 was,the more conducive to the transmission of V(V).With the aid of ED,the transmission capacity of V(V)by PIM was significantly improved.At the current density of 20 m A/cm²,the permeability coefficient of V(V)was increased from 0.2?m/s to 2.2?m/s in the absence of electric field.It showed that VO₂⁺and SO₄^2-in acidic sulfate environment slowly form VO₂SO₄^-complex,which is transported in PIM through two mechanisms of"carrier diffusion"and"fixed site jump",and the extraction process of V(V)is completed by anion exchange mechanism under the reverse extraction of appropriate amount of HSO₄^-.Under the optimum experimental conditions,the extraction yield and extraction yield reached 92%and 91%,respectively.In the stability test of the system,it showed good stability,and the transmission efficiency of V(V)kept basically stable in 5 cycles.In exploring the selective separation of V(V)by PIM-ED,it was found that vanadium could be separated from nickel,cobalt,manganese and other metals by the system.