Study On The Separation Of Nickel(Ⅱ) And Magnesium(Ⅱ) By P227 And The Extraction Technology

The impurity of magnesium in nickel sulfate must be removed in the industrial production process.Solvent extraction method has the characteristics of high productivity,high recovery rate,low energy consumption and low pollution,which makes solvent extraction widely used.The structure of extractant determines the efficiency of solvent extraction.Di（2-ethylhexyl）phosphonic acid（P227）shows a similar ability on extracting nickel and magnesium to Cyanex 272,showing great potential in the separation of nickel and magnesium.Therefore,to improve the separation factor of nickel and magnesium and optimize the extraction separation process conditions of P227,a series of experiments have been carried on the preliminary exploration of nickel and magnesium,and provided technical support for the development of new nickel sulfate purification technology in the future.This paper is mainly divided into the following three research parts:（1）In this chapter,ammonia was added to the water to increase the affinity of water to nickel ions and reduce the distribution ratio of P227 to nickel ions.Finally,it was found that using P227-n-hexane as the organic phase,ammonia concentration in water phase was 1 mol/L,the extraction rate of Mg（Ⅱ）was more than 97%,and almost no nickel ions were extracted,the separation time was less than 3 min,in the meantime,theβ_Mg/Ni was about 1000.But hexane is volatile,the characteristic of low boiling point is not conducive to the practical production.In addition,the extractant P227 is an acidic extractant.In the case of high p H,a small part of the acidic extractant will dissolve and lead to the loss of part of the extractant.Therefore,the ammoniacal system of P227-n-hexane does not meet the requirements of industrial production.（2）In this chapter,the extraction and separation ability of P227 for nickel and magnesium be improved by adding a salting-out agent to the aqueous phase of the sulfuric acid system.By studying the effects of Na₂SO₄ and（NH₄）₂SO₄ on the extraction of Ni（Ⅱ）and Mg（Ⅱ）with P227,the results shows that the addition of Na₂SO₄ and（NH₄）₂SO₄ can improve the separation coefficient of nickel and magnesium,which（NH₄）₂SO₄ has the greatest effect.When the concentration of（NH₄）₂SO₄ in the aqueous phase was 1 mol/L,theβ_Ni/Mg was 10 times as much as that in the aqueous phase without adding salting out agent.In order to optimize the extraction and separation process of Ni（Ⅱ）and Mg（Ⅱ）with P227-n-dodecane in sulfuric acid system,the effects of the extraction phase（O/A）,temperature,extractant concentration,and nickel-magnesium content ratio on the extraction and separation of Ni（Ⅱ）and Mg（Ⅱ）with P227 was studied.When bis（2-ethylhexyl）phosphonic acid（P227）is used as the extractant and dodecane is used as the diluent,the same saponification agent is added,and the comparison（O/A）is getting smaller and smaller,and the equilibrium p H was getting higher and higher.The extraction rate of Mg（Ⅱ）and Ni（Ⅱ）both increased;With the increase of the extraction temperature,the extraction rate of magnesium ions gradually increases,and the separation coefficientβ_Mg/Ni between magnesium and nickel increases,The separation coefficientβ_Mg/Ni at 50°C is 5 times that at 5°C;The system is endothermic reaction,and the△H is 30424 k J.The binary linear regression equation between the p H of the feed,the concentration of the extractant and E shows that when the p H value is constant,the extraction rate of nickel ions increases with the increase of the concentration of the extractant.The effect of the equilibrium p H of the water phase is greater than that of extractant concentration.When the relative content of Mg（Ⅱ）in the feed solution increases,the extraction rate of P227for both Ni（Ⅱ）and Mg（Ⅱ）decreases slowly,but the change ofβ_Mg/Ni is very small.When the C_Ni:CMg decrease from 5:1 to 1:10,the extraction system can separate the metals.（3）For the optimization of the back-extraction process of loaded ion P227,the influence of sulfuric acid concentration,back-extraction time and back-extraction relative to P227 back-extraction was studied.It is found that 0.2 mol/L of H₂SO₄ can completely back-extract magnesium ions;the back-extraction time has almost no effect on the back-extraction rate of Mg（Ⅱ）,and Mg（Ⅱ）,and the Mg（Ⅱ）can be almost completely back-extracted in 1 minute,while in the stripping process of Ni（Ⅱ）,the stripping rate increases with time.When the stripping time is 10 minutes,the equilibrium is reached,and the first stripping rate of Ni（Ⅱ）is 80%.Under the premise of not affecting the back extraction rate,the time of back extraction should be minimized,so the appropriate time for back extraction is 10 min;when the back extraction ratio is 1:1,it can meet the complete back extraction of Mg（Ⅱ）and Ni（Ⅱ）.The stripping rate is low and the phase separation time is short.