Electromembrane Extraction Of Low Concentration Chromium(Ⅵ) By Polymer Inclusion Membrane Based On TOPO And TOA

Most of the traditional Cr（Ⅵ）-containing wastewater treatment processes have the disadvantages of serious secondary pollution,low efficiency,large resource consumption,and difficulty to reuse the treated water.PIM electricmembrane extraction technology with polymer inclusion membrane（PIM）as the membrane phase,extraction and back extraction are carried out simultaneously,with good selectivity,high removal efficiency,green and pollution-free,is a kind of energy-saving and environmentally friendly harmless technology.In this paper,low-concentration Cr（Ⅵ）was used as the treatment object,and polyvinyl chloride（PVC）was used as the basic polymer.A new polymer inclusion based on tri-n-octylamine（TOA）and trioctylphosphine oxide（TOPO）was prepared.The electrical membrane extraction behavior of Cr（Ⅵ）by PO-PIM and plasticized PT-PIM was studied.The chemical composition and micro-morphology of PO-PIM and PT-PIM were analyzed by ART-FTIR,XRD and SEM characterization techniques.The low concentration Cr（Ⅵ）at p H1.3 is the feed liquid phase,and the stability,selectivity and enrichment ability of the two PIM electric membrane extraction systems for Cr（Ⅵ）mass transfer were discussed.The main research contents are as follows:（1）There are chain-like fiber bundle liquid membrane channels on the surface of PO-PIM.There is a dipole-dipole interaction and hydrogen bonding between TOPO and PVC.With the neutral or alkaline aqueous solution as the analytical phase,the permeability coefficient P of the Cr（Ⅵ）extracted by the PO-PIM electricmembrane increases with the increase of the TOPO content of the carrier in the membrane,but after the TOPO content exceeds 0.25g,the Cr（Ⅵ）The permeability coefficient P decreases.At a voltage of 100V,the optimal composition of PO-PIM has a permeability coefficient P of 54.31um/s for the extraction of Cr（Ⅵ）electromembrane.For Cr（Ⅵ）and Cd（Ⅱ）,Co（Ⅱ）,Ni（Ⅱ）,The selective separation factors of Zn（Ⅱ）are 15.75,142.09,256.68,and 13.15,respectively.Taking 0.2mol/L Na OH solution as the analytical phase,the enrichment factor of Cr（Ⅵ）in the PO-PIM electro-membrane extraction system within 60h was 5.08.（2）Using dioctyl phthalate（DOP）,o-nitrophenyl octyl ether（NPOE）and tributyl phosphate（TBP）as plasticizers,three series of plasticizations were introduced into PT-PIM（PTD-PIM,PTN-PIM,PTT-PIM）,discussed the mass transfer behavior of Cr（Ⅵ）extraction by plasticized PT-PIM electric membrane.The results showed that the plasticizer can improve the compatibility between the basic polymer PVC and the carrier TOA.The low-concentration Na OH solution can be used as the analytical phase for the extraction of Cr（Ⅵ）by plasticized PT-PIM.The mass transfer of Cr（Ⅵ）by plasticized PT-PIM is an ion exchange system,and the mass transfer behavior conforms to the first-order kinetic equation.The voltage reduces the chemical complex between Cr（Ⅵ）and carrier TOA and the degree of control of mass transfer.（3）The effect of plasticizer on the extraction of Cr（Ⅵ）by PT-PIM electricmembrane was investigated,and the stability,selectivity and enrichment ability of Cr（Ⅵ）extraction by plasticized PT-PIM electric membrane were investigated.The results showed that the viscosity,water solubility,dielectric constant and other physical and chemical properties of the plasticizer will affect the extraction of Cr（Ⅵ）from the plasticized PT-PIM electrical membrane.The highly hydrophobic DOP helps to improve the PT-PIM electrical membrane extraction stability.The high dielectric constant NPOE is beneficial to promote the dissociation of Cr（Ⅵ）from the carrier.The membrane composition is the plasticized PT-PIM of P₂₅T₁₃D₁₅,P₂₅T₁₅N₂₀,P₂₅T₁₅T₂₀.When the voltage is 50V,30V,30V,respectively,the permeability coefficient P of the extraction of Cr（VI）electric membrane is 47.17um/s,52.41um/s,43.75um/s.The permeability coefficient P of Cr（Ⅵ）extracted by PTD-PIM electromembrane is basically unchanged in four cycles,and the Cr（Ⅵ）in the coexistence system of Cd（Ⅱ）,Co（Ⅱ）,Ni（Ⅱ）,Zn（Ⅱ）has excellent selectivity.At 50V operating voltage,the enrichment factor for Cr（Ⅵ）is close to 10 within 80h.