氟碳铈-独居石混合矿中钍的分离

Separation of Thorium From Mixed Bastnaesite-Monazite Concentrate

以氟碳铈矿-独居石混合稀土矿为研究对象，采用分步选择性碳热氯化-化学气相传输反应（SC-CVT），实现钍与其它稀土元素的分离。当氯化反应温度为500℃，以活性炭为还原剂、SiCl4为脱氟剂，在Cl2气氛下稀土矿反应2h时，钍的氯化产物（ThCl4）挥发量小于1％;继而以AlCl3作配位体，800℃、Cl2气氛下传输反应0.5h，ThCl4与配位体反应形成气态配合物ThAlCl7；温度降低时，ThAlCl7分解并沉积在600℃左右的温区内，AlCl3沉积在温度低于200℃的温区内，FeCl3主要沉积在200～350℃的温区内，从而实现放射性元素Th的分离和回收。

A stepwise carbochlorination-chemical vapor transport （SC-CVT） technique is proposed for separation of thorium from mixed bastnaesite-monazite concentrate. Mixed bastnaesite-monazite concentrate is first isothermally carbochlorinated for 2 h in a Cl2 atmosphere with activated carbon as a reductant and SiCl4 as a fluorine scavenger at a temperature as low as 500℃, only about 1 percent of the total thorium contained in the bastnaesite-monazite concentrate is evaporated. CVT processing is then undertaken at 800℃ for 0.5 h in a Cl2 SiCl4-AlCl3 atmosphere. During this stage thorium is converted to a volatile complex ThAlCl7, and is driven to transport to a temperature-gradient collection system, where thorium is deposited around 600℃, while FeCl3 and AlCl3 are deposited in the range of 200～350℃ and at even lower temperature（〈200℃）, respectively. By using this technique the pollution caused by thorium radioactivity could be significantly alleviated.