氢氧化钠焙烧钙热还原氟化稀土还原渣及其热力学分析

针对钙热还原氟化稀土还原渣,开展了直接酸浸实验、氢氧化钠焙烧-酸浸实验。结果表明,直接酸浸时稀土提取率约72%,而氢氧化钠焙烧-酸浸稀土提取率达92.3%。热力学分析和实验结果共同表明: 在298~1 300 K温度范围内,氢氧化钠与渣中DyF₃、CaCO₃和CaF₂反应,生成Dy₂O₃、NaF、CaO、Na₂CO₃和CO₂; 氢氧化钠能将氟化稀土转化为氧化稀土,这是稀土提取率提高的主要原因。

Thermodynamics Analysis for NaOH Roasting of Reduction Residue from Calcium Thermal Reduction of Fluorinated Rare Earth

Aiming at the reduction residue generated after the calcium thermal reduction of fluorinated rare earth, experiments were performed with direct acid leaching process and a combined process of NaOH roasting and acid leaching. It is shown that the extraction rate of rare earth is around 72% by direct acid leaching process, but can reach 92.3% by the combined process. Both thermodynamics analysis and the experimental results indicate that at the temperature ranging from 298 K to 1 300 K, NaOH reacts with DyF₃, CaCO₃ and CaF₂ in the residue, producing Dy₂O₃, NaF, CaO, Na₂CO₃ and CO₂; sodium hydroxide can convert fluorinated rare earth to oxidized rare earth, which contribute substantially to the increase of the extraction rate of rare earth.