The Study Of Adsorption And Separation Of Re(Ⅶ), Mo(Ⅵ) And As(Ⅴ) With A New Type Of Ion Exchange Resin

Ion exchange resins are widely used in the process of adsorption and separation,and it consists of three-dimensional networks, functional groups attached to thepolymeric matrix and the ion carrying opposite charge on functional group.Depending on the matrix types, ion exchange resins (e.g. acrylic,styrene-divinylbenzene, phenol-formaldehyde and epoxy-amine) possess differentproperties and show various of selectivity towards the same ions. Polystyrenecrosslinked with divinylbenzene (PS-DVB) as a resin matrix offers remarkablechemical and physical stability, which is more stable than phenol-formaldehydematrices. Chloromethylation of polystyrene-divinylbenzene resin (Merrifield resin)with chlorine methyl group is very easy to react with nucleophiles. The amination ofthe chloromethylated copolymers with trimethylamine or dimethylethanolamineprepared strong base anion exchangers of Types I and II, respectively. Moreover, theamination with primary amine, secondary amine and tertiary-amine gained weak baseanion exchange resin.Ionic liquid functionalized strongly basic anion exchange resins (RCl) weresuccessfully synthesized by anchoring N-methyimidazole on Chloromethylatedcopolymers of styrene-divinylbenzene (Merrifield resins). The SO42-ionic form anionexchange resin (R2SO4) was attained by contacting RCl with1mol/L Na2SO4solution.The functionalized resin can not only overcome some drawbacks of ionic liquids,such as large amount used, high viscosity and losses of ionic liquids, but also improvethe physical and chemical stability of ion exchange resins. The decompositiontemperature of RCl and R2SO4is220°C according to thermogravimetric analysis.The maximum weight loss velocity temperature of RCl and R2SO4occurs at258oCand241oC, respectively, but the temperature of ordinary hydroxyl anion exchangeresin is only220°C. And thus, the prepared anion exchangers possess higher thermalstability. Moreover, the new type of ion exchange resin also exhibited very goodchemical stability in the base and acid aqueous solution, except that when14%NaOCl and5mol/L NaOH were used as degradation agents. The resins are morestable than common quaternary ammonium and pyridinium based anion exchangeresins.N-methylimidazolium functionalized strongly basic anion exchange resins R2SO4 was studied to adsorb and separate Re(VII) and Mo(VI) from binary mixture ofRe(VII)-Mo(VI) solution and copper arsenic filter cake. At pH6.25, Re(VII) andMo(VI) can be effectively separated with the resin, and it exhibited high selectivityand adsorption efficiency for Re(VII). The maximum loading capacity of the anionexchanger is462.0mg/g, and the adsorption is an exothermic reaction. When theinitial Mo(VI) concentration value is40g/L in the Re(VII)-Mo(VI) solution, theseparation factor (βRe/Mo) value is up to25.6. Moreover, the R2SO4can efficientlyadsorb Re(VII) from real copper arsenic filter cake sample, and adsorption ratio canachieve89.1%. R2SO4was easily regenerated with dilute nitric acid (1mol/L)/sulfuricacid (1mol/L) which was good washing solution for eluting Re(VII).Moreover, we also studied the strongly basic anion exchange resins RCl toremove As(V) from aqueous solution in this paper. At pH9.8, the adsorption percentis90.0%, and the adsorption equilibriums were attained at60min. The Langmuirisotherm fitted the data quit well, and the maximum adsorption capacities of As(V) onRCl was67.2mg/g. The adsorption percentage for As(V) increased slightly withincreasing temperature. The process of ion exchange was endothermic reaction. Theloaded resin was easily regenerated with0.1mol/L HCl, and desorption efficiency canachieve99.46%. RCl had almost no loss of adsorption amount during four cycles. RClwas stable in multiple adsorption-desorption operations, and could be regenerated andreused repeatedly.