摘要
Preparing rare earth carbonates from rare earth chlorides is a common step in the smelting process for all rare earth ores;however,it produces large amounts of ammoniacal nitrogen wastewater and a chloriderich precipitate.This study proposes a novel,green and simple process for preparing low-chlorine lanthanum carbonate via a multi-membrane electroconversion approach.The effects of the CO_(2) flow rate,current density,lanthanum chloride concentration,and electroconversion time on the electroconversion process were systematically explored.Under the optimal process conditions(CO_(2) flow rate=0.5 L/min,current density=25 mA/cm^(2),LaCl_(3) concentration=0.3 mol/L,electroconversion time=60 min),a current efficiency of 75.77% was obtained,along with a unit energy consumption of5.44 kWh/kg.X-ray diffraction,Fourier transform infrared spectroscopy,thermogravimetric analysis,and laser particle size analysis results indicate that a pure La_(2)(CO_(3))_(3)·8H_(2)O product is obtained with a median particle size of 6.53 μm and chlorine content of 0.0021%.In addition,scanning electron microscopy and transmission electron microscopy observations indicate that the crystallisation and growth of La_(2)(CO_(3))_(3)·8H_(2)O conform to the oriented attachment and Ostwald ripening mechanisms.Thus,the proposed multi-membrane electroconversion method provides guidance toward the clean transformation of rare earth chlorides to low-chlorine lanthanum carbonates.
基金
supported by the Postdoctoral Research Project of Henan Province (HN2022004)
Zhongyuan Critical Metals Laboratory(GJJSGFYQ202319,GJJSGFYQ202328)
Open Fund project of Key Laboratory of Ecological Metallurgy of Multi-Metal Intergrown Ores of Ministry of Education(NEMM2022003)
Guangxi Science and Technology Major Project (Guike AA22068078)
National Key R&D Program of China (2021YFC2902604)。
