| Vanadium is an important rare element,which commonly exists as anassociated element in vanadium titano-magnetite and vanadium-bearing carbonaceous shale.To extract vanadium from these low grade resources,the first step usually is to leach vanadium from the vanadium-bearing resources,and then,the separationand enrichment of vanadium from the leaching solutions is needed to meet the requirements of subsequent process of product preparation.The separation and enrichment of vanadium from solution is one of the key processes,which determinesthe success of vanadium extraction technology and the purity of final vanadium product.At present,the main methods,solvent extraction and ion exchange,for purification and enrichment of metals from aqueous solution have inherent shortcomings.The invention of solvent impregnated resins(SIRs)has set up a bridge between solvent extraction and ion exchange,combining the advantages of both technologies.The specific advantages include simple preparation process,less reagent consumption,environmental-friendliness,high adsorption and separation efficiency,hence it have been widely applied in the separation and purification of metals.In this study,the SIRs were used in treatment of vanadium-bearing solutions.The preparation conditions of the SIRs,the adsorption and separation properties of vanadium,and the adsorption mechanism of vanadium on the SIRs were investigated,respectively.The main research content and conclusions are as follows:(1)It was found that the extractant P204 was best for vanadium extraction,and petroleum ether was also the best dilution for P204 during the preparation of SIRs according to solvent extraction test and inpregnation experiments,respectively.Hence,the combination,i.e.P204+petroleum ether,was can be used as extraction agent.According tothe three evaluation indicators,the impregnation rate of the extractant,the total adsorbed quantity of vanadium on the SIRs and the adsorbed quantity of vanadium onunit extraction agent,the XAD-16 HP resin was proved anideal support resin for the SIR.It was found that the result of dry impregnating method was better through the comparison of common impregnating method.The SIRs has good adsorption performance on adsorption of vanadium when it was preprared by the following optimum conditions:extractant concentration is 50%,the ratio ofextraction solvent tosupport resinis 10:1 mL/g,impregnating time is 12 h,and impregnating temperature is 25?.In virtue of SEM,FTIR,TG,specific surface area and pore size analysis and swelling degree test,itcan be assured that theexistence and effectiveness of extractant in the P204 impregnated resin.Comparedthe adsorption characteristics of vanadium by the SIRs and solvent extraction,it wasshown that vanadium extraction efficiency of impregnated resin has been improved obviously.(2)By the static adsorption experiment results,it can be foundthat the bestadsorption pH value of V(?)and V(?)was 2.The adsorption quantity of V(?)and V(?)increased with the increase of equilibriumconcentration,until adsorption equilibrium quantity were achieved at 16.04 mg/g and 18.21 mg/g,respectively.Rising temperaturewas conducive to the adsorption process.The adsorption quantity of V(?)and V(?)on theP204 impregnated resin was increased with the extension of contact time andthe initial adsorption rate was fast,the adsorption equilibrium time was 18 h and 12 h,respectively.The dynamic adsorptionperformance of V(?)and V(?)on theP204 impregnated resin was studied.It was found that the breakthrough volume was increasedwith the reducing of flow rate and the increase of the column.At this condition,the breakthrough timealsocan beextended,and it is conducive to the adsorption process.For the ternary mixture solution with V(?),Fe(?)and Al(?),the stepping adsorption-elution process was designed by the affinity difference of metal ionson the P204 impregnated resin,then the satisfyingvanadium recovery and enrichment ratio wasachieved.(3)The adsorption process of V(?)and V(?)onthe P204 impregnatedresinwas met the Langmuir isothermal adsorption equation.Thermodynamic parameter calculation resultsshowed that enthalpy change?H>0,entropy change?S>0,the Gibbs free energy under different temperature?G<0,indicating that the adsorption process was an endothermic,entropy increment and spontaneous process.The study on adsorption kinetics of V(?)and V(?)onthe P204 impregnated resin showed thatthe pseudo-second orderkinetic equation can describe the adsorption processwell,and through the rate control steps fitting results,it canbe knownthat adsorption process was controlled by particle diffusion.The molar ratioof P204 to the vanadium adsorbed on the P204 impregnated resinwasmeasured as 4:1by saturation method and slope method,thus the adsorption equation can be obtained.The adsorption mechanism of vanadium onthe P204 impregnated resin was the combination of the cation exchange and coordination reaction,whichalso wasverified bythe Fourier transform infrared spectroscopy. |
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