The Study Of Activation Of Pb In Extraction Of Ionic Rare Earth Ore

China has the richest ionic rare earth ore resources around the world.There are three main exaction process:pool leaching,heap leaching,and in-situ leaching,which is used widespread.The in-situ leaching process is that injecting the leaching agent through the injection fluid wells to weathering ore bodies under the condition of natural bury.The rare earth cations are exchanged by leaching cations,formating the rare earth mother liquor.In a long-term time,a large amount of high concentration(NH4)2SO4 is used in the ionic rare earth ore leaching process.The NH4+ will also activate the heavy metals of the ore after it exchages with rare earth cations,which will make the soil and groundwater polluted by activated heavy metals.The ionic rare earth ore leaching process can make the heavy metals activated,which is studied little around the world.This paper studied the process that ionic rare earth ore leaching process can make the heavy metals activated,which selected the Pb as representative.The main research results were as followsThe ionic rare earth ore adsorbed ammonium in the way of physical adsorption and polymolecular layer chemical adsorption,maximum adsorption capacity was 6.62 mg/g(in terms of nitrogen,the same below).The result was fitted well with pseudo-second reaction kinetics and Freundlich adsorption isotherm,the intraparticle diffusion model described that the adsorption of ammonium was mainly controlled by exterior adsorption and bulk diffusion.Ammonium-N concentration of mother liquor was low at the beginning,and increased when the ore adsorbed well,untill the concentration was the same with leaching agent.The concentration of La3+ and Ce4+ increased till the maximum,then decreased till the concentration was zero.The Pb was activated after rare earth element was extracted well,its concentration trend was same with La3+ and Ce4+,but the activation process lagged behind the extractionExchangeable fraction and bound to carbonate fraction La and Ce almost be extracted completely,which the unmined quantity of middle was higher than the top and the low position.Then,the Pb was activated,the cations' proportion which exchanged La3+,Ce4+and Pb2+ of CEC was very low.The exchangeable fraction Pb would be activated first,about 70%of the exchangeable fraction Pb was activated.The activated exchangeable fraction Pb became a part of the mother liquor,the 30%of the exchangeable fraction Pb was still the form,but they could not be extracted with the method that extracted exchangeable fraction Pb,which increased the quantity of the fractions of bound to carbonate,bound to Fe-Mn oxides and bound to organic matter.When the extraction of ionic rare earth ore was finished,the exchangeable fraction Pb was not activated completely,the other forms of Pb were also sensitive to pH.Therefore,the surplus Pb of ore was a potential pollutant,which was able to be activated again and polluted the environment when the ore body environment changed(acid rain).