Thermal Decomposition Kinetics of Rare Earth Minerals in Tailings with Addition of MgO

Yan Zhou,Xiangxin Xue,Gongjin Cheng,Shizhe Song,He Yang,Jianxing Liu

doi:10.3390/met11050701

Abstract

Due to the advantage in deactivating fluorine and enhancing the decomposition of rare earth (RE) minerals, MgO was applied to the magnetizing roasting of Bayan Obo tailings in this work. The effects of MgO dosages, roasting temperature, and holding time on the decomposition rate of RE minerals were experimentally studied. With a MgO dosage of 10 wt.%, the decomposition rate of RE minerals reached 98.09% at 750 °C. The phase composition of roasted samples was characterized by XRD and SEM-EDS. The incomplete decomposition rate was investigated with the observation of leaching residual by SEM-EDS. The decomposition kinetics of the RE minerals with the addition of MgO was analyzed with the Ginstling-Brundshtein model, where the reaction rate was controlled by chemical reaction.

Highlights

MgO was analyzed with the Ginstling-Brundshtein model, where the reaction rate was controlled by chemical reaction
The effect of MgO on the thermal decomposition of rare earth (RE) minerals in tailings was experimentally investigated in this study
With the MgO dosage of 10 wt.%, the decomposition rate of RE minerals increased to 98.09% at 750 ◦ C

Summary

Introduction

Rare earth (RE) elements, namely lanthanum (Ln), scandium (Sc), and yttrium (Y), are irreplaceable strategic resources for innumerable applications owing to their chemical, catalytic, electrical, magnetic, and optical properties [1,2,3,4]. The technologies of roasting with sulfuric acid and treatment in sodium hydroxide are mainly applied to decompose the RE minerals in concentrate, but are uneconomical for processing the tailings [2,9]. These methods lead to environmental pollution, such as emissions of HF and SO2 , plenty of waste-water [2]. In our previous study [6], the method combining magnetizing roasting and (NH4 ) SO4 activation roasting was developed to recover Fe and RE elements from the Bayan Obo tailings. This study is expected to provide a clean method for the recovery of RE minerals in tailings

Materials

Procedures and Characterization

O2 solution ple powders

Effect of dosages on the decomposition rate of Effect ofof

XRD pattern ofof samples under different conditions: sample ofof tailings

Effect

Kinetics Analysis of Mixed RE Mineral Decomposition

12. Arrhenius

Findings

Conclusions