Research On The Leaching Law Of Rare Earths And Impurities In Phosphorite Ore By Acid Leaching

Phosphate rock contains abundant rare earth resources, in the conventional wet phosphoric acid production process, the leaching rate of rare earths is low.Due to the complexity of impurities in phosphate rock composition, the leaching rule of rare earths whether has a certain relevance with impurities during acid leaching process,whether the reaction of the impurity elements in the pickling process will affect the rare earths leaching, is a major problem to research on this thesis.Therefore,the paper studies the leaching rules for rare earth elements and impurities in different acid system, and combined with the basic chemical reaction thermodynamics theory of rare earth and impurities, in-depth analysis the relevance between rare earth and impurities,so as to provide a theoretical basis for the comprehensive recovery of rare earth.By thermodynamic calculation and analysis, the results show that the reaction between fluorapatite and H3PO4 to generate Ca(H2PO4)2 is more easier than the reaction between fluorapatite and H2SO4 to generate CaSO4?2H2O,therefore,when the mixed acid of Sulfuric acid and Phosphoric acid to leach phosphate rock,the first step is to generate Ca(H2PO4)2,and then Ca(H2PO4)2 react with H2SO4 to generate CaSO4?nH2O.When Sulfuric acid or mixed acid leaching phosphate ore,RE3+ easy to react with H2PO4- and PO43- generate soluble REH2PO42 + and insoluble REPO4, so rare earths in phosphoric acid solution mainly exists in the form of REH2PO42+.During the Leaching process,F may react with rare earths to generate insoluble REF3,CaO will crystallization precipitation in the form of CaSO4?nH2O, so F, CaO may lead to the decrease of distribution ratio of rare earths in phosphoric acid solution.The research on leaching rules of Rare earth and impurities in different acidsystem show that Cao is the main impurity to influence the distribution of ?REO in phosphoric acid solution, and presents a positive correlation between the two. when CaO enter into phosphoric acid solution distribution ratio is low, ?REO extraction rate is low. when CaO enter into phosphoric acid solution distribution ratio is high,?REO extraction rate is high.During Leaching process, ?REO leaching rate do not decrease with the increase of F,due to F exists in the phosphoric acid solution in the form of HF, and with SiO2 reacts to fluoride silicate, do not generate insoluble REF3,so F is not the reason that cause ?REO have a low leaching rate. The leaching rules of rare earth and impurities in different ore during the leaching process are similar,which shows that the principle of the rare earth and impurities enter into the phosphate solution is the same. Parathion mixed acid stepwise is advantageous rare earth to enrich in phosphoric acid solution; The leaching rate of ?REO of Zhijin,Fanshan Phosphate Mine is 62.73%, 51.97% respectively when phosphoric acid concentration is 8.6mol/L, leaching time is 3h, sulfate excess coefficient is 1.00,temperature is 80?, liquid solid ratio is 6:1.The results of the physical and chemical properties of the solution showed that:the acidity and viscosity of the leaching liquor were the main factors affecting the leaching of rare earth.Within the scope of the sulfur phosphorus molar ratio of 1:2,with the increase of mole ratio, solution acidity increase, rare earth leaching rate increases; When the mole ratio of more than 1:2, solution viscosity rise sharply,which has a obvious retarding effect for rare earths leaching. In order to obtain ideal ?REO leaching rate should choose appropriate sulphur phosphorous mole ratio.