Extraction And Separation Of Impurity Zinc In The Process Of Using Phosphating Slag To Prepare Battery-grade Iron Phosphate

Phosphating slag is an inevitable product in the phosphating process.It is mainly composed of phosphate and various metal ions.If it is not treated,the phosphating slag is randomly buried or discarded.Phosphate leaching into the soil causes acidification of the soil and metal ions will accumulate in plants or water to seriously pollute the environment,also waste a lot of valuable elements.Therefore,it is of great significance to recycle the valuable elements in the phosphating slag resources.This article is based on the analysis of the physical properties of the phosphated slag raw materials to provide a basis for the research on the recovery and utilization of phosphate group,on this basis,the resource utilization of PO₄^3-in the phosphated slag is carried out:Firstly,the phosphated slag is leached with Na OH solution to separate the PO₄^3-from other impurity metal ions to obtain a leaching solution containing a high concentration of PO₄^3-,but the solution contained low concentration of impurity zinc ions,and then,Solvent extraction is used to extract and separate the zinc ions in the leachate to obtain the purified leachate.Finally,ferric chloride solution is added to provide the iron source and PO₄^3-in the leaching solution to form precipitated iron phosphate,so as to achieve the purpose of recycling PO₄^3-in the phosphating slag to prepare battery-grade iron phosphate.The main technical processes in the preparation of battery-grade iron phosphate using phosphating slag include:alkali leaching process,extraction process,metathesis reaction process.The NaOH solution leaching experiment on phosphating slag showed that the alkali slag ratio is an important factor for PO₄^3-alkali leaching.The optimal alkali slag ratio is 0.65,and the leaching rate of PO₄^3-is 93.97%under this condition.The experiment of extracting zinc ions in simulated solution with single extractant system showed that the solid form extractant dithizone is not easy to emulsify.the solubility of dithizone in CHCl₃can reach 17.55 g/L at 25?.The main factors affecting the extraction are:solution p H,temperature,stirring speed,extractant concentration and comparison.The optimal zinc removal conditions for dithizone is p H=7.25,stirring speed 550 r/min,temperature 25?,O:A=1:1,organic phase composition 1.2 g/L dithizone-chloroform,the single-stage extraction rate of zinc ion can reach 92.57%,the dithizone and zinc ion are chelated at a molar ratio of 2:1;the double extraction agent system extracts zinc ion in the simulated solution.The experiment results that the optimal separation condition is p H=7.25,stirring speed550 r/min,temperature 25?,O:A=1:3,the organic phase composition is 1.2 g/L dithizone+volume ratio 10%P204-chloroform,the single-stage zinc ion extraction rate can reach 93.67%,the extractants dithizone and P204 are combined with zinc ion in a molar ratio of 1:3:2;the extraction experiment in the actual leaching solution is:using disulfide The hydrazone and P204 extractant constitute a double extractant system to extract the leachate.The zinc extraction effect of the mixed extractant is significantly better than the corresponding single extractant.When O:A=1:5,the single-stage extraction rate of zinc ion can reach 55.39%,and the zinc ion concentration in the raffinate is 8.4 mg/L.The metathesis reaction process is investigated and the experiment showed that the reaction p H,the content of the added iron source,and the amount of surfactant are important factors affecting the metathesis reaction.The optimal experimental conditions for the preparation of iron phosphate is reaction p H=2.0,add iron-phosphorus molar ratio R=1:1.2,the amount of CTAB is 3%of the mass of the iron source.Under this condition,a battery-grade iron phosphate product can be prepared,in which the impurity zinc content is 24.2?g/g and the iron-phosphorus ratio is 0.98.Through this three-step,the total recovery utilization rate of PO₄^3-can reach 78.31%.