红土镍矿硫酸浸出液中和除铁过程Ni^(2+)和Mg^(2+)损失机理及强化分离研究

Study on the mechanism of Ni^(2+)and Mg^(2+)loss and enhanced separation in sulfuric acid leachate of laterite nickel ore during iron removal using neutralization process

中和沉淀工艺常用于去除红土镍矿酸浸液中的铁、铝、铬等杂质,这一过程中常伴随镍、镁等金属离子的损失。本工作研究了红土镍矿硫酸浸出液中和除铁过程中Ni^(2+)和Mg^(2+)的损失,提出了有价金属离子的损失机制。研究表明,固定模拟浸出液Ni^(2+)和Mg^(2+)浓度条件,随模拟浸出液中Fe^(3+)浓度增大,中和沉淀过程中Ni^(2+)和Mg^(2+)的损失率分别在9.13%~23.23%和9.79%~15.68%左右;固定模拟浸出液Fe^(3+)浓度条件,随着模拟浸出液中Ni^(2+)和Mg^(2+)浓度的提高,二者的损失率逐渐降低。根据溶液化学计算与实验证实,中和沉淀过程中SO_(4)^(2-)与Fe(OH)_(3)胶体形成一元和二元配合物,其中一元配合物中SO_(4)^(2-)的孤对电子与Ni^(2+)或Mg^(2+)成键而发生吸附,从而导致溶液中Ni^(2+)和Mg^(2+)与SO_(4)^(2-)被Fe(OH)_(3)胶体共吸附而损失。在中和沉淀过程中分别加入十六烷基三甲基溴化铵(CTAB)、聚乙二醇(PEG)和十二烷基苯磺酸钠(SDBS)等表面活性剂后均能有效限制SO_(4)^(2-)与Ni^(2+)或Mg^(2+)的结合,强化Fe^(3+)的选择性沉淀。当三种表面活性剂的浓度均为2×10^(-5)mol/L时,Ni^(2+)在中和沉铁过程的保留率可达95%左右,Mg^(2+)可达100%。

Neutralization precipitation process is often used to remove impurities such as iron,aluminum and chromium from the nickel laterite acid leach solution,however,it accompanied with the loss of nickel and magnesium metal ions.The precipitation behaviors of Ni^(2+)and Mg^(2+)ions in nickel laterite acid leach solution during the neutralization precipitation iron removal process was deeply discussed in this work.Furthermore,a novel precipitation mechanism of Ni^(2+)and Mg^(2+)with SO42-during the neutralization precipitation iron removal process was proposed.The results showed that under the condition of fixed Ni^(2+)and Mg^(2+)concentrations in simulated leachate,the loss rate of Ni^(2+)and Mg^(2+)during neutralization and precipitation respectively were 9.13%~23.23% and 9.79%~15.68% with the increase of Fe^(3+)concentration in simulated leachate.Under the condition of fixed Fe^(3+)concentrations,the loss rate of Ni^(2+)and Mg^(2+)decreased with the increase of the concentration of Ni^(2+)and Mg^(2+).According to the results of solution chemical calculation and the characterization of iron hydroxide precipitation by infrared spectroscopy and scanning electron microscopy,both SO_(4)^(2-)ions and Fe(OH)_(3) colloids could co-precipitate in the form of monovalent or binary complex during the neutralization process,in which the lone pair electrons of SO_(4)^(2-)in the monovalent complexes bond with Ni^(2+)and Mg^(2+)and adsorb,resulting Ni^(2+)and Mg^(2+)in the leachate were co-adsorbed with SO_(4)^(2-)by Fe(OH)_(3) colloid and the loss was caused.In addition,it was found that the surfactant such as cetyl trimethylammonium bromide(CTAB),polyethylene glycol(PEG),sodium dodecyl benzenesulfonatecan(SDBS)was added during the neutralization precipitation process can effectively compete for adsorption with neutralizing precipitated products or impede the combination of SO2-4 with Ni^(2+)and Mg^(2+)ions,which could enhance the selective precipitation of Fe^(3+)ions during neutralization process.When the dosage of three surfactants was 2×10^(-5) mol/L,the retention rates of Ni^(2+)in the process of neutralization and precipitation of iron could reach about 95%,and Mg^(2+)could reach 100%.