Study On PH Regulation And Complex Precipitation Combined Impurity Removal Process And Mechanism Of Magnesium Salt Leaching Solution Of Ionic Rare Earth Ore

The occurrence forms and properties of impurity ions in ionic rare earth ores are similar to those of rare earth ions.During the leaching process,a large number of impurity ions enter the rare earth leaching solution and affect the precipitation and crystallization of rare earth.It not only generates amorphous flocculent precipitation,resulting in difficulties in solid-liquid separation,but also causes serious loss of rare earth in the impurity removal process and reduced recovery rate.At present,the commonly used ammonium bicarbonate impurity removal process has the problems of low impurity removal rate,high rare earth loss rate,long impurity removal and precipitation cycle and high production cost.In this paper,the rare earth leaching solution obtained from magnesium sulfate leaching of ionic rare earth ore is taken as the research object.The impurity removal test of Al³⁺and Fe³⁺in the leaching solution is carried out by using p H regulation impurity removal process,complex precipitation impurity removal process and combined impurity removal process.The impurity removal mechanism is characterized by FT-IR,solution chemical calculation and MS simulation calculation,The impurity removal effects of different impurity removal processes were systematically studied.The removal effect of Al³⁺and Fe³⁺in the rare earth leaching solution obtained from the magnesium salt leaching of ionic rare earth ore was studied by using the p H regulation impurity removal process.The results show that while the ideal impurity removal effect is obtained,there is a large loss of rare earth ions,which is not conducive to the recovery and utilization of rare earth elements.When ammonium bicarbonate and ammonia adjust the p H value of the leaching solution to be less than 5.0,the OH^-produced by reagent hydrolysis reacts with impurity ions to form insoluble hydroxide precipitation,which can remove most of the impurity ions without losing rare earth ions.However,when the p H value of rare earth leaching solution is adjusted to be greater than 5.2,a large number of rare earth ions begin to be transformed into insoluble rare earth precipitation,resulting in serious loss of rare earth.Therefore,the optimal p H value of impurity removal by p H regulation of ionic rare earth ore leaching solution should be less than 5.2 as far as possible.The removal of Al³⁺and Fe³⁺in the rare earth leaching solution obtained by magnesium salt leaching of ionic rare earth ore was studied by complex precipitation process.The results show that while complexing to remove impurity ions,the metal ion complexing agent will also have complex precipitation reaction with rare earth ions,which affects the effective recovery of rare earth ions.Rose red ammonium tricarboxylate,Alizarin Red S and alizarin violet can reduce the p H value of the leaching solution while complexing and precipitating with impurity ions,avoiding the loss of some rare earth ions caused by the increase of p H value of the leaching solution.The reagent has strong selectivity for impurity ions and weak complexation ability with rare earth ions.Although it can not achieve ideal impurity removal effect,it can be used in combination with p H regulator.The effect of pH regulation complex precipitation combined impurity removal process on the removal of Al³⁺and Fe³⁺in the leaching solution of ionic rare earth ore was studied.The results show that the combined process can basically remove impurity ions while ensuring a low rare earth loss rate.The reagent combination of ammonium bicarbonate+Rose Red ammonium tricarboxylate could obtain 5±0.84%rare earth loss rate,95±0.79%Al³⁺removal rate and 94±0.96%Fe³⁺removal rate.The test indexes are good.The process has the advantages of simple operation,strong adaptability,low impurity removal cost,less loss of earth ions,which was good for the effective recovery of rare earth elements.