Acidic Treatment Of Scheelite By Organic Sodium Phytate At Atmospheric Pressure

Decomposition of scheelite using sulfur-phosphorus mixed acid is one of the mainstream technologies in tungsten metallurgy,but it required high concentration of phosphoric acid.Phytic acid is composed of six phosphates and inositol.Based on the strong complexation ability of six phosphoric groups on phytic acid root to tungsten-oxygen complex,a new process for the decomposition of scheelite by phosphorus phytate in sulfuric acid solution at atmospheric pressure was proposed.The reaction mechanism of the phytic system decomposition scheelite,sodium phytate atmospheric pressure decomposition process conditions,the extraction of tungsten from acid leaching solution,dephosphorization of magnesium salt and circulation of leaching mother liquor problems were investigated,the main contents of research were as follows:（1）The reaction mechanism of scheelite decomposition by inorganic phosphoric acid and organic phosphorus phytate in sulfuric acid solution was described.The reaction of the decomposition of scheelite by H₂SO₄-H₃PO₄may be the conversion of WO₄^2-to polyacid polymerization ion or soluble tungstic acid（WO₃（OH）^-）,and then immediately converted into H₃[PW₁₂O₄₀]monomer by high concentration of phosphoric acid.Under the same concentration of total phosphorus,the leaching rate of tungsten decomposed by phytate system was much higher than phosphoric acid system,The six phosphate groups on phytic acid root closely complexed tungsten-oxygen atoms to form the phytic tungsten cluster,the complexation performance of phytate was better than single phosphoric acid group.（2）The applicability of phytate system to different scheelite was investigated,and the process of sodium phytate decomposition of scheelite concentrate was studied.The new method has strong adaptability to different raw materials.H₂SO₄and sodium phytate were the driving force of the reaction.Under the condition of adding only 10g/L sodium phytate,the leaching rate of scheelite reached 99.39%.（3）The extraction behavior of tungsten from acid leaching solution with different extractants was investigated,and the co-extraction performance of impurities such as phosphorus,iron,calcium and molybdenum was compared.The optimal extraction system was selected.TBP and amine extractants were excellent extractants with potential,but the extraction rate of phosphorus with 15%N1923+10%sec-octanol was higher.The extraction rates of calcium and iron in 30%N235 were both higher than that in 60%TBP,and the separation coefficientβ_W/Moof tungsten and molybdenum was obviously lower than 5.The reverse extraction of weak base ammonia water is good,and neither ammonium paratungstate crystal nor reddish brown iron hydroxide precipitation was produced.Therefore,considering the extraction and stripping performance comprehensively,it was recommended to use 60%TBP as the extraction agent,loaded organic phase was stripped by ammonia.（4）The phosphorus removal of magnesium salt and cyclic open circuit experiment of leaching mother liquor was investigated.Magnesium sulfate was added to generate phyate-Mg precipitation.The residual concentration of P in the solution was lower than the national standard.In the raffinate returned to the leaching process for 5 cycles of mother liquor leaching,the satisfactory leaching rate of tungsten achieved,the concentration of phosphorus in the solution basically kept balance about 2 g/L,the concentration of phosphorus in the stripping solution was about 0.5 g/L.This paper has a total of 48 pictures,25 tables,163 references...