Adsorption Properties And Mechanisms Of In (Ⅲ) And Fe (Ⅲ) Using Impregnated Resins Containing Neutral Phosphorous Extractant

Indium is a rare metal element which is widely applied in the field of high technology. Inrecycling indium from the mineral or secondary resources, it is necessary to solve theinterference of other metal elements, especially iron element in acid leaching solution. Hence,How to separate In(III) and Fe(III) efficiently and environmental friendly has been theresearch difficulties. Solvent impregnated resins (SIRs) are prepared with extractantsimpregnated in a specific macroorous resin carrier. Being a green and high efficient separationtechnology, SIR technology is alternative system combining the advantages of both solventextractant and ion exchange resin method. It is expected to provide a novel approach toachieve the effective separation of In(III) and Fe(III) with the suitable solvent impregnatingresin prepared by choosing a extractant and carrier. Meanwhile, the adsorption mechanismstudy of SIRs provide a theoretical basis for the further adsorption and separationinvestigation of In(III) and Fe(III).Cyanex923/HZ830and TBP/HZ830SIRs was prepared with two kinds of neutralphosphorous extractant (trialkyphosphine oxide (Cyanex923) and tributyl phosphate (TBP))and styrene-dithylbenzene macroorous carrier (HZ830). The two kinds of SIRs containingneutral phosphorous extractant were characterized by scanning electron microscopy,thermogravimetric analysis and infrared spectroscopy. Then the adsorption behavior andmechanism of In(III) and Fe(III) was studied with these SIRs in hydrochloric acid medium bystatic adsorption method and dynamic adsorption method:(1) In the static adsorption experiment, it was shown that the optimal hydrochloric acidconcentrations for In(III) and Fe(III) adsorption with Cyanex923/HZ830SIR were2mol·L-1and6mol·L-1, respectively. TBP/HZ830SIR showed hardly adsorption for In(III), but itsadsorption for Fe(III) increased with the increasing hydrochloric acid concentration. Theadsorption isotherms of In(III) and Fe(III) with two SIRs gave satisfactory ft of Langmuiradsorption model and belong to the monolayer adsorption. Thermodynamic data indicatedthat the adsorption processes were endothermic and entropy increase ones. Kinetic datarevealed that the adsorption for In(III) and Fe(III) with these two SIRs agreed with the pseudosecond-order rate equation, and the intraparticle diffusion was rate limiting.(2) The influence of HCl concentration on In(III) and Fe(III) species distribution diagrams were listed by the adsorption mechanisms investigation. The mechanisms involved thesolvation extractants combined with neutral species and ion pairs (involving associationsbetween protons and anionic indium or iron chloro-species) of the metal ions. From the slopeanalysis study, the effects of the amounts of extractants, HCl activity on the extracted specieswere determined. The stoichiometry of the extracted complexes investigated by SIRs werefound to be MCl3·nL and HMCl4·nL (n=2,3; M representative In(III) or Fe(III)). Theadsorption reaction equations of In(III) and Fe(III) by two kinds of SIRs in different HClconcentrations were also given according to the extracted complexes. The possibleinteractions between the extractant immobilized on the SIRs and the different species of metalions were described.(3) The adsorption properties of In(III) and Fe(III) were investigated by dynamicadsorption experiments. The research suggested the lower flow rate had a better absorptionefficiency on In(III) and Fe(III) with two kinds of SIRs. High column increased the contacttime with metal ions and increased the adsorption capacity. The loading column could beefficiently desorbed using2mol·L-1solutions of sulfuric acid and the possibility of reusingthe SIRs were demonstrated over five cycles. In binary separation system, the SIRs have agood separation trend with In(III) and Fe(III). Cyanex923/HZ830SIR was used to adsorbIn(III) from acid leaching solution of copper-smelting dust and the hydrochloric acid leachingwith copper-smelting dust achieved a better effect on Indium recovery. The exist of largeamounts of Cu(II), Fe(III), Cd(II) and Zn(II) had a serious influence on the separation andrecycling of In(III). Remove of Cu (II), Fe (III), Cd(II) and Zn(II) by fractional precipitationmethod could achieve the purpose of preliminary separation of indium.