Weathering Crust Refractory Rare Earth Ore Leaching Process And Help With The Mechanism

The weathered crust elution-deposited rare earth ore in China has been attracted extensiveattention and exploited rapidly due to high-content heavy rare earth and relatively simpleextraction process. As long-term extensive exploitation of rare earth resources, high-grade andeasy-leaching rare earth ore has been preferentially exploited and resulted to rare earth resourcepoor and difficult to leach. In the leaching process of difficult-leaching rare earth with low-gradeand low ion content.The rare earth smearing phenomenon is serious, leaching liquid-solid ratio islarge, leaching rate is low and leaching impurity content is high, and it also requireshigh-concentration leaching agent, high-cost and leaching effect is poor. Aimed at the aboveproblems, coordination aid-leaching technology for leaching process and mechanism was studied,in order to improve leaching effect and rare earth resource utilization rate and reduce leachingcost by using coordination aid-leaching technology strengthen leaching process.Taking difficult-leaching heavy rare earth ore as object, rare earth and aluminum leachingbehavior was studied. The results indicated that there were obvious differences between rare earthand aluminum leaching process. For rare earth leaching process, leaching speed was relativelyfaster, obvious peaks of leaching concentration were found, but for aluminum leaching process,leaching concentration change was small, leaching speed was slow and concentration curve wassmooth. The exchange ability of different ions on rare earth from high to low was NH+4, K+, Na+and Mg+. Ore properties and leaching conditions had a great influence on leaching process.Leaching rate was higher in the conditions of water rate low, rare earth size fine, concentration ofleaching agents high, leaching speed slow, and pH low and ore hight tall. While if theseconditions were over a certain limit, leaching rate would greatly drop. The leaching behaviors ofaluminum was less affected by electrolyte types, leaching agents concentration and flow speedand other factors, but significantly effected by pH value. The lower pH value, the more leachingamount of aluminum ions.In order to strengthen leaching process of difficult-leaching rare earth ores, coordinationaid-leaching technology for was studied by adding different coordination agents to the leachingagents. As was shown from the results, LPC had no aid-leaching effect on rare earth leachingprocess. Acetylacetone, Ammonium citrate tribasic, dihydroxysuccinic acid, LPD and LPF couldall promote leaching. Acetylacetone and LPD had poor aid-leaching effect. Aonium citratetribasic and dihydroxysuccinic acid could increase leaching rate, but they were not suitable to beselected as aid-leaching agents because they could increase leaching amount of aluminum ion.LPE was an optimum aid-leaching agent because it could increase leaching rate and not increaseleaching amount of aluminum ion, and LPE was non-toxic and environmentally friendly. Taking LPF as aid-leaching agent for rare earth low-grade ore, an effective constituent of LPE after isolation and purification, the aid-leaching effects indicated that leaching rate could increase8.38%after adding0.10%LPF to (NH4)2SO4, and (NH4)2SO4concentration reduced25%, liquid-solid ratio reduced5%. These results all showed that LPF had remarkable aid-leaching effect. The aid-leaching mechanism showed that LPF reacted with rare earth ions to form soluble coordination compound, thus reduced activity of the leached rare earth ions, increased concentration difference of ion diffusion and promoted rare earth leaching process. It also reduced electric quantity of of coordination compound, decreased electrostatic attraction of clay minerals to rare earth coordination ions in order to improve diffusion rate.In the presence of coordination agent LPF, coordination filter-leaching kinetics for low-grade rare earth ore was studied. The results indicated that the leaching process was in-diffusion controlled. Kinetic equation by trial-and-error method was as follows:Kinetics studies showed that the apparent activation energy has reduced2.18kJ/mol and LPF coordination aid-leaching technology can effectively promote the leaching kinetics process of weathering crust elution-deposited rare earth ore earth ore.