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采用硝酸浸出铁矿废渣磷灰石中的铈、镧、钕稀土元素,应用响应面方法对硝酸浓度、液固比和浸出时间对稀土元素浸出率的影响进行了研究。结果表明,硝酸浓度和液固比对稀土浸出率的影响较大,而浸出时间的影响较小。在浸出条件为硝酸浓度18%、液固比0.06和浸出时间38 min的情况下,可得到最大的铈、镧、钕稀土元素浸出率,其分别为66.1%、56.8%、517.%。采用收缩核模型对铈的浸出动力学进行研究。结果发现,浸出过程由两个阶段组成,在第一阶段,铈的浸出率随时间增长快速增加;随时间的延长,浸出率增长逐渐变慢。在第一阶段,反应受灰分层内扩散控制,反应的表观活化能为6.54 k J/mol;在第二阶段,溶液中的质量传递为反应控制步骤。
The effects of concentration of nitric acid, liquid-solid ratio and leaching time on the leaching rate of rare earth elements were studied using nitric acid leaching of cerium, lanthanum and neodymium rare earth elements in apatite from iron ore wastes. The results show that the concentration of nitric acid and liquid to solid ratio of the rare earth leaching rate greater impact, and the impact of leaching time smaller. The leaching rates of rare earth elements such as cerium, lanthanum and neodymium were 66.1%, 56.8% and 517%, respectively, with leaching conditions of 18% nitric acid concentration, liquid-solid ratio of 0.06 and leaching time of 38 min. The leaching kinetics of cerium was studied by the contracting kernel model. The results showed that the leaching process consisted of two stages. In the first stage, the leaching rate of cerium increased rapidly with time. With the extension of time, the leaching rate gradually slowed down. In the first stage, the reaction is controlled by diffusion in the ash layer, and the apparent activation energy of the reaction is 6.54 kJ / mol. In the second stage, the mass transfer in the solution is the reaction control step.