氢氧化钠焙烧钙热还原氟化稀土还原渣及其热力学分析

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

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298~1300 K温度范围内,氢氧化钠与渣中DyF_(3)、CaCO_(3)和CaF_(2)反应,生成Dy2O_(3)、NaF、CaO、Na_(2)CO_(3)和CO_(2);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。

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 1300 K,NaOH reacts with DyF_(3),CaCO_(3) and CaF_(2) in the residue,producing Dy2O_(3),NaF,CaO,Na_(2)CO_(3) and CO_(2);sodium hydroxide can convert fluorinated rare earth to oxidized rare earth,which contribute substantially to the increase of the extraction rate of rare earth.