Anti-swelling Leaching Technology Of Weathered Crust Elution-Deposited Rare Earth Ore With DMDACC

Weathered crust elution-deposited rare earth ore is the main source of middle and heavy rare earth in the world,and its exploitation has great industrial value.Rare earths are adsorbed on clay minerals by hydrated or hydroxyl hydrated ions,and can only be recovered by ion exchange.In industry,ammonium sulfate is mainly used as the leaching agent to recover rare earth in in-situ leaching technology.Clay minerals have the characteristics of swelling with adsorption of water and shrinking with loss of water.The swelling of clay minerals would lead to the infiltration pores of the leaching agent to become smaller during in-situ leaching process.Meanwhile,the fine clay minerals will also migrate with the leaching agent,blocking the pores,resulting in decreasing leachate seepage speed and aggravating effusion of ore,prolonging the exploitation cycle,reducing the recovery rate of rare earth.In serious cases,it will lead to the occurrence of geological disasters such as landslides,affecting the economic benefits of mining enterprises.Therefore,it is necessary to select a swell inhibitor that can promote seepage and suppress clay mineral expansion.This paper mainly analyzes the mineralogical properties of weathered crust elution-deposited rare earth ore,using CPZ-2dual channel linear swellmeter to evaluate the inhibition property of diallyl dimethyl ammonium chloride(DMDACC)on montmorillonite and rare earth ore.At the same time,the inhibition mechanism was investigated by FI-IR,XRD,SEM,laser particle size analyzer and Zeta potential.Combining DMDDAC with rare earth leaching agent ammonium sulfate,the effect of the compound system on the inhibition performance and rare earth leaching were discussed.The optimal leaching process parameters,the kinetics of rare earth leaching and dynamic model were also stuied to provide theoretical basis and technical support for the efficient development and utilization of weathered crust elution-deposited rare earth ore.The main research contents and results are as follows:(1)The mineralogical properties of the weathered crust elution-deposited rare earth ore were studied,and it was found that the content of full phase rare earth and aluminum in the ore were 0.10% and 12.86%,the content of ionic phase rare earth was 0.096%,and the content of exchengeable aluminum was 0.09%.The order of rare earth content in different occurrence states in this ore was: ionic phase> mineral phase> colloid phase >> water soluble phase.The order of aluminum content in different occurrence states was: mineral state> amorphous aluminosilicate state> iron oxide bound state> adsorbed hydroxyl aluminum> interlayer aluminum> exchange state> water soluble state.The thermogravimetric analysis of the mineral verified the ore with many kinds of water.(2)The Anti-swelling performance of a single DMDACC and compound system on montmorillonite and rare earth minerals was evaluated,and the Anti-swelling mechanism was investigated.It was found that DMDDAC perform a great inhibition effect on montmorillonite and rare earth minerals,and the increasing concentration of DMDACC enhance the inhibition performance.The inhibition mechanism of DMDACC for clay minerals may be that DMDACC adsorbs on the surface of clay minerals and effectively neutralize the negative charge on the surface of clay particles,reducing the entry of water molecules into the crystal layer,increasing the particle size of particles,and weakening hydration of clay.At the same time,the mixed solution of DMDACC and ammonium sulfate can make the absolute value of the surface potential of the rare earth mineral particles approach zero.It may increase the anti-swelling performance which means the stability of the ore body is enhanced,and landslides can be effectively prevented from occurring.(3)Using column leaching method to simulate in-situ leaching process,the effects of concentration of DMDACC,liquid-solid ratio,leaching temperature,initial pH of leaching agent and flow rate on the leaching process of rare earth and aluminum were studied using,and found the optimized process parameters of leaching rare earth are 2 wt%(NH4)SO4 compounded with 0.6 wt% DMDACC,0.8:1 liquid-solid ratio(mL/g),0.5 mL/min of flow rate,pH4 ~ 5 and room temperature.Under the conditions,the leaching efficiency of rare earth can reach more than 95%,and the leaching efficiency of aluminum is more than 90%.The leaching process of rare earth ores is controlled by internal diffusion.The apparent activation energy of rare earth and aluminum are 5.14 kJ/mol and 8.51 kJ/mol,and the reaction order of rare earth and aluminum are 0.079 and 0.073.