Electrodriven Transport Of Chromium(?) Using Polymer Inclusion Membrane Under Low Voltage

Heavy metal Cr(?)has the characteristics of high toxicity,persistence and bioaccumulation.Even if it is present at low levels in the water,will the body chronic poisoning caused by food chain terminal enrichment,even carcinogenic,teratogenic and mutagenic,which is serious harm to human health and ecological safety.The traditional treatment method of wastewater containing Cr(?)is complicated,and the secondary pollution is serious.The polymer inclusion membrane(PIM)separation technology based on the principle of liquid membrane is an environmentally friendly separation method with simultaneous extraction and extraction.It has a good application prospect in the treatment of chromium containing wastewater.Under the coupling of electric drive,the mass transfer of PIM could greatly enhanced,which can be applied to the harmless treatment and resource recovery of Cr(?)wastewater,and have extremely important research significance.Based on the above,this paper studies the mass transfer of Cr(?)in water phase under low voltage driven by PIM.The main research contents are as follows:(1)Polymer inclusion membrane(PAV-PIM)was prepared cotaining tricapryl(methyl)ammonium chloride(Aliquat 336)as the carrier.The effects of four additives such as 1-octanol(OCT)on the mass transfer performance of PAV-PIM were investigated.The transmission behavior of PAV-PIM to Cr(?)was studied under electric drive.The results show that with the increase of the Aliquat 336 content in the membrane,the removal rate of Cr(?)in the liquid phase increased,but the residual amount of Cr(?)in the membrane also increased.The external voltage drive can significantly improve the mass transfer efficiency of PAV-PIM membrane to Cr(?).The residue of Cr(?)in the PAV-PIM membrane can be reduced by introducing OCT.PAV-PIM has good removal rate and recovery rate for Cr(?)under these conditions that the content ratio of Aliquat 336 to OCT is 0.4:2.0,the liquid phase and the stripping phase is pH 1.3 HCl and 0.3 mol/L NaOH aqueous solution,respectively.The permeability coefficient(P)of Cr(?)is up to 45.73 ?m/s under 10 V.(2)The transport behavior of Cr(?)from the aqueous phase through a polymer inclusion membrane(PO-PIM)containing OCT as carrier and polyvinyl chloride(PVC)as support at a low voltage drive(0~30 V)is investigated.The correlation between the OCT content and the surface or cross-sectional micromorphology of PO-PIM is also analyzed.Under optimized mass transfer conditions,the transmission rules and mechanism of Cr(?)under an electro-driven transport of PIM system are investigated.Results show that the surface and interior of PO-PIM exhibit micro/nanopores with an OCT content exceeding 50 %(w/w).The mass transfer behaviour of OCT to Cr(?)conforms to the proton coupling mechanism.The voltage drive effectively solves the residue problem of Cr(?)in the membrane phase,and the P of PO-PIM to Cr(?)increases with the 0~30 V voltage.The P of PO-PIM to Cr(?)reaches 43.38 ?m/s at 30 V when the OCT content is 82.8 % and the feed and stripping phases are pH 2.0 HCl solution and 0.1 mol/L NaOH solution environments,respectively.After the introduction of hydrophobic kerosene into the membrane phase,the stability of the membrane is significantly enhanced.When the composition ratio of kerosene/OCT/PVC is 0.8:2.2:0.5 and the voltage is 30 V,the initial current density rise is only 0.1 A and the pH increases slightly with the repeated use of PO-PIM to four cycles.(3)The PMMA/PVC two element composite polymer inclusion membrane(PMO-PIM)was prepared by introducing the solid plasticizer(Polymethylmethacrylate,PMMA)into PO-PIM.The transmission behavior of PMO-PIM under electric drive to Cr(?)was investigated.The composition of the membrane was analyzed by surface infrared(ATR-FTIR),and the morphology was observed by scanning electron microscope(SEM).The results show there was strong hydrogen bond and dipole-dipole interaction between PMMA and OCT.When the ratio of PMMA to PVC is 0.1:0.4 as well as the carrier content was fixed to 1.4 g,the transmission system of PMO-PIM was stable and obtains a relatively high transmission rate.With the increasing of the carrier content,the structure of membrane changed significantly.When the addition of the carrier was 73.68 %,the membrane was homogeneous and the surface showed concave and convex structure,and the transmission rate was also the best.Within the 40 V voltage,the transmission rate of Cr(?)increased,but the transmission rate decreased after 40 V.Under the experimental conditions,the concentration ratio of PMO-PIM to Cr(?)can reach 3.33 times,and the mass transfer performance remains unchanged in the range of 12~37 mg/L Cr(?).(4)The PIM based on tributyl phosphate(TBP)as carrier was prepared by using cellulose triacetate(CTA)and PVC as the substrate,respectively.The strong dipole-dipole interaction between TBP and PVC was showed by ATR-FTIR,and it is clarified that the mass transfer advantage of PTT-PIM to Cr(?)based on CTA based polymer.The influence of the composition of the buffer solution of the stripping phase on the mass transfer performance in the mass transfer of PTT-PIM to Cr(?)was investigated.The better action of acetate system on mass transfer in electric drive and the adverse effects of high voltage on the stability of the transmission system were preliminarily verified.