钕铁硼磁材二次废料制备高纯硫酸亚铁

钕铁硼磁材废料经回收稀土后产生大量的二次废料，针对该废料含铁量高的特点，对废料中的铁元素提取进行了相关研究，铁元素以硫酸亚铁产品形式回收。酸浸提铁阶段考察了酸浓度、浸提温度、反应时间、液固比(酸体积/废渣质量)、浸取次数等因素对铁离子浸出效果的影响，通过单因素实验得到较优的酸浸工艺参数：硫酸浓度6 mol/L、浸提温度80℃、反应时间120 min、液固比4∶1(mL/g)和浸取次数2次，在此条件下铁的浸出率约为97.8%。还原阶段考察了温度、反应时间及废铁屑过量系数等因素对Fe³⁺转化为Fe²⁺效果的影响，得到较优的还原工艺参数：还原温度为80℃、反应时间为120 min和废铁屑过量系数为1.2，在此优化条件下，Fe³⁺转化为Fe²⁺的转化率约为97.69%。最终采用浓缩、冷却结晶、重结晶的方法制得硫酸亚铁产品，产品纯度99.92%。

Preparation of high-purity ferrous sulfate from NdFeB magnetic material secondary waste slag

A large amount of secondary waste residue is produced after rare earth recovery from NdFeB magnetic waste material. In view of the high iron content in waste residue component, the iron extraction from the waste residue was studied, and the iron was recycled in the form of ferrous sulfate products. In the stage of iron extraction by acid leaching, the effects of acid concentration, extraction temperature, leaching time, liquid-solid ratio (acid volume/waste residue mass), and leaching frequency on iron ion leaching were investigated in detail. The optimal acid leaching process parameters obtained by univariate experiments are acid concentration of 6 mol/L, leaching and extracting temperature of 80 ℃, leaching time of 120 min, liquid-solid ratio (mL/g) of 4∶1 and leaching frequency of 2, under which the leaching rate of iron ions is approximately 97.8%. In the reduction stage, the effects of temperature, reaction time and scrap iron excess coefficient on the conversion of Fe3+ to Fe2+ were investigated. The obtained optimal reduction process parameters are reduction temperature of 90 ℃, reaction time of 120 min, and scrap iron excess coefficient of 1.2, under which the conversion rate of Fe3+ to Fe2+ is 97.69%. Finally, the ferrous sulfate product is obtained by concentration, cooling crystallization and recrystallization, with the purity of 99.92%.