Study On Re(?)Separation By Imidazole-based Ionic Liquid Functionalized Adsorption Materials

Ionic liquids have great designability and are widely used in the field of adsorption separation.In particular,imidazolyl ionic liquids show great adsorption potential for scattered metals due to their abundant nitrogen elements.Here,we use imidazole ionic liquid to copolymerize with divinylbenzene or compound with MOFs to solidify the ionic liquid and improve its adsorption efficiency.At the same time,the adsorption and separation ability of the adsorbent material to the dispersed metal Re?VII?in aqueous solution was explored.The specific results are as follows:1.A simple radical polymerization of divinylbenzene and vinylimidazolium-based ionic liquid was used to prepare a resin-based imidazolium-based ionic liquid copolymer?DVB-n-C₈VEIMX?for selective adsorption of Re?VII?.The addition of divinylbenzene reduced the loss of the ionic liquid,and solidified liquid ionic to make it easier to separate.The adsorbent showed good stability,the maximum saturated adsorption capacity for Re?VII?was 313.28 mg·g^-1.The adsorption process conformed to the langmuir adsorption isotherm model,which was a spontaneous exothermic reaction.Even in the presence of a large number of coexisting ions(SO₄^2-,NO₃^-,NO₂^-,Cl^-,CO₃^2-,PO₄^3-),it still displayed high adsorption capacity for Re?VII?.More importantly,the adsorbent can effectively separate molybdenum and rhenium in a wide acidic range of pH 1-3 M.And at 3M,the adsorption percentage of Re?VII?remained above 60%.In addition,the effects of alkyl chain length,steric hindrance and anion species on the recovery of Re?VII?were reported.The mechanism of electrostatic attraction and ion exchange was verified by XPS,IC and FT-IR.Meanwhile,it still showed super strong regeneration performance and structural stability after 10 cycles with an 88.21%adsorption efficiency and an 95.11%elution efficiency,which reflected the practical application value of the material.2.Metal-organic frameworks?MOFs?are a new type of porous solid material with large surface area,high porosity,adjustable pore size,which are considered to be a good adsorbent material.We selected MIL-101 as the matrix material and used immersion grinding to made in-situ polymerization of bivinylimidazole ionic liquid inside and outside the porous structure of MOFs to prepare a stable heterogeneous composite material?y-P?C_nVIM₂Cl₂?@MIL-101?.MIL-101,as a porous framework,accelerated the mass transfer speed of target ions and improved the time to reach adsorption equilibrium.The bivinylimidazole ionic liquids increased the adsorption functional groups.Compared with solvothermal method,the heterogeneous synthesis method of dipping and milling reduced the number of adsorption sites occupied by chemical bonding.Besides,the polymerization of the ionic liquid on the MOFs framework was ensured,so that the adsorbent had higher adsorption capacity for Re?VII?,and the maximum adsorption capacity was 642.41 mg·g^-1.According to the experimental results,the adsorption effect of the composite material was far superior to that of MIL-101 or P?C₄VIM₂Cl₂?.We explored the effect of different alkyl chain lengths on the adsorption performance of Re?VII?.The fitting results of the Langmuir adsorption isotherm model indicated that the saturated adsorption capacity of Re?VII?for composites with alkyl chain lengths of two,four,and six were 298.02 mg·g^-1,642.41 mg·g^-1,402.12 mg·g^-1,respectively.The adsorbent with alkyl chain length of six exhibited the best selectivity,and the adsorbent with alkyl chain length of four had a faster adsorption rate.After soaking the three adsorbents in aqueous solutions of different acidity for 48 hours,the residual masses all remained above 85%,and the XRD spectrum manifest that the intact crystal structure,which showed excellent stability.The adsorption mechanism were mainly the anion exchange between Cl^-on the ionic liquid functional groups and ReO₄^-,and the electrostatic attraction of quaternized nitrogen on the imidazole ring and ReO₄^-.