Separation Of Nickel And Cobalt By Solvent Impregnating Resin In Sulfuric Acid System

Cobalt and nickel are adjacent elements in the periodic table, and their separation has been a problem all the time. Current separation methods mainly include: chemical precipitation, ion exchange, membrane separation and solvent extraction. This article uses solvent impregnating resin method which combines high selectivity of solvent extraction and high separation series of ion exchange to sulfate system to investigate the separation effect of nickel ions and cobalt ionsand the purification of cobalt ions.On the basis of previous research and validation test, chosing P507- Cyanex272 system which has good synergy to the separation of cobalt ions and nickel ions as the extractant of solvent impregnated resins. Experiment of four kinds of macroporous resin, chosing HZ818 as support for producing resins and ethanol as diluent of extractant. The result indicated that: under the condition of cobalt ion concentration was 0.21 g·L-1, temperature was 30℃, equilibrium pH was 4.8, the saturated adsorption amount of cobalt ion of self-made impregnating resin was 34.28 mg·g- 1.Static extraction experiments showed that with the increase of temperature, cobalt extraction rate increased, nickel extraction rate dropped and separation factor of cobalt and nickel increased, extraction temperature was 30℃ in considering selecting; with the increase of reaction equilibrium pH, extraction rate of cobalt and nickel were higher, after greater than 4.8 of the balance pH value, change of cobalt extraction rate was slow, and nickel extraction rate after balance pH greater than 5.5 increased rapidly.It will produce cobalt deposits if the pH is too high andgo against on the experiment, so the selection of extraction equilibrium pH value was 4.8.The research of separating of high nickel and low cobalt solution by double extraction solvent impregnated resins showed that: for good load effect,we need to make pretreatment for separation column with Hac-NaAc buffer solution before loading feed liquid. The best conditions for buffer solution was: 100 m L buffer solution which has the concentration of 0.5 m L·L-1flowed past column by current velocity of 5.0 m L·L-1.Dynamic experimental result indicated that: we can get a good absorption efficacy under the condition of temperature was 30℃, 400 m L feed liquid pH value was 4.8, current velocity of feed liquid was 5.0 mol·L-1. Ni2+ and Co2+ were separated when temperature was 28℃, elution speed was 5.0 mL·min-1, buffer elution pH value ofNi2+was 4.0. Eluting Co2+ volumn was 50 mL by sulfuric acid with pH1.0 when eluting Ni2+ volumn was 200 m L, and we obtained cobalt sulfate solution with 99.27% purityFor high nickel and low cobalt solution and in order to get high purity cobalt solution, increasing separation column high diameter ratio will increase the leaching liquid volume, greatly reduce the leaching efficiency, so eventually chosing packing column high aspect ratio was 3.7.Preparing solution with magnesium ions, nickel ions and cobalt ions simulated actual biological leaching liquid after deeply removing impurity to investigate separation effect. The results showed that the addition of magnesium ions has no effect on separation efficiency for nickel ions and cobalt ions. The research for enrichment ability of Co2 + found the impregnating resin has not bad enrichment effect for low concentration Co2+. The research about absorption ability in different Ni2 +/ Co2 + ratio indicated that in a certain range, bigger Ni2 + / Co2 + ratio,better solution separation effect.