Chemical Phase Analysis Of Calcium In Processing Materials

Calcium is an important element,and there are a lot of need in the determination of calcium and calcium compounds,the methods on the total content determination of calcium are mature,while there is little research on the chemical phase analysis of calcium.Recently some new scientific research projects and products quality control fields put forward new requirements to the phase analysis of calcium.Because existing method system can’t solve these problems well,a systematic and reliable method system for chemical phase analysis of calcium needs to be established.In this paper,Leaching experiments were carried out among single minerals such as calcite,fluorite,dihydrate calcium sulfate,free lime and apatite to study their dissolution mechanism.Calcite could be dissolved by 1:9 acetic acid solution and 12.5%ammonium citrate solution,the dissolution rate of wollastonite was as high as 67% in 1:9acetic acid solution and 10% in 12.5% ammonium citrate solution.Sodium silicate could be added to inhibit the dissolution of wollastonite in 12.5% ammonium citrate solution.For samples with low content of wollastonite,selected 1:9 acetic acid solution,while high content of wollastonite,selected 12.5% ammonium citrate solution and added sodium silicate to inhibit the dissolution of wollastonite in 12.5% ammonium citrate solution at the same time.Fluorite could be dissolved completely in 8% Al Cl3 solution and mixed acid composed of hydrochloric acid-boric acid-sulfuric acid,the existence of calcium minerals such as free lime,calcium hydroxide,calcium carbonate,calcium sulfate and so on would cause interference to the determination.Free lime could be dissolved in the sucrose solution,dihydrate calcium sulfate could also be dissolved in the sucrose solution,but it didn’t bring interference to the determination of free lime in modified hydrochloric acid titration method.25% sodium chloride solution was used to leach dihydrate calcium sulfate commonly,with the interference of free lime and calcium hydroxide.The determination of dihydrate calcium sulfate for the mineral containing free lime and calcium hydroxide,could take the sucrose solution leaching-hydrochloric acid titration method to determine the content of free calcium oxide and calcium hydroxide,then use EDTA titration method to determine the total amount ofcalcium oxide in leaching liquid,the content of dihydrate calcium sulfate could be obtained by minus method.In the determination of apatite,we took 3% nitric acid solution as leaching solution,and calculated the content of apatite according to the content of phosphorus in the leaching solution.According to the dissolution rule of calcium compounds and the sample characteristics,specific chemical phase analysis methods were formulated for roasted ore for kiln process phosphoric acid and fluorite concentrate.And according to the formulation of chemical phase analysis method respectively,Standard addition recovery experiment and standard sample measurement show the feasibility of the method;analysis results were consistent with XRD pattern and multi elements results,and could provide guidance for process technology.