Study On Efficient Extraction Of The Rare Earth From Bastnaesite Concentrate By Calcification Transition Process

Rare earth is a unique resource in China with its advantage of abundant reserves, considerable variety and high grade. With the application of rare earth and its alloys in the fields of military, information, energy, biotechnology etc, efficient rare earth extraction methods are being paid more and more attention in academia and industry.The bastnaesite is a main kind of rare earth mineral with important industrial value. Currently, the traditional process of "roasting transformation-stripping" is mainly used in the production of bastnaesite, which leads to high energy consumption and operating costs. Considering the characteristics of bastnaesite and the disadvantages of traditional process, a new hydrometallurgical technology of "calcification transformation-acid leaching" was proposed in this paper, which aims to extract the valuable rare earth elements as well as retain fluoride in bastnaesite effectively and cleanly.In this paper, the basic issues of calcification transition process and acid leaching process of bastnaesite have been studied, and important conclusions were obtained:(1) The optimal pressure calcification transition conditions are as follows:calcification temperature of 220℃, calcification time of 3h, liquid-solid ratio of 15:1, ore-base ratio of 20:7.53:4.Bastnaesite was transferred to rare-earth hydroxide completely with the present experimental condition, the highest leaching rate of different rare earth elements was obtained: Ce 67.96%, La 76.04%, Nd 75.18%, E RE 72.46%.(2) The optimal mechanochemistry calcification transition conditions are as follows: calcification temperature of 220℃, calcification time of 3h, liquid-solid ratio of 5:1, ore-base ratio of 5.015:1.911:1.015, ratio of ball and material of 8:64.5, the leaching rate of rare earth were as follows:Ce 80.30%, La 90.47%, Nd 89.39%,ERE 85.32%.Compared with the pressure calcification transition, the total leaching rate of rare earth was greatly increased by 13%; and the water consumption was greatly reduced by 67%.(3) The optimal acid-leaching conditions are as follows:acid-leaching temperature of 25 ℃, acid-leaching time of 10min, liquid-solid ratio of 15:1, hydrochloric acid concentration of 2.5mol/L, stirring speed of 300rpm. In this condition, the leaching rate of different rare earth elements was:Ce 80.30%, La 90.47%, Nd 89.39%,∑RE 85.32%.(4) In the pressure calcification--acid-leaching process, fluoride was recovered in the acid-leaching residue in the form of CaF2, Separation of fluoride from the rare earth was achieved with less than 0.5% loss rate of fluoride in the whole process.