Goethite (α-FeOOH) and calcium sulfate (CaSO₄·2H₂O) are the main solid constituents of the iron oxide residues in zinc hydrometallurgy by the goethite process. Impounding these residues in tailings ponds is costly to maintain and causes a great threat to the local environment. In this study, magnetic separation was applied to separating goethite from calcium sulfate with maghemite (γ-Fe₂O₃) fine particles as the carrier, which were prepared by roasting −1 μm pure magnetite mineral particles. The SEM images and XRD patterns indicated the precipitation of goethite on maghemite fine particles in the goethite process, which made the goethite aggregates magnetic, while the calcium sulfate formed nonmagnetic bulk precipitates. The magnetic goethite–maghemite aggregates were then separated effectively from calcium sulfate precipitates using a magnetic drum separator. The recovery of Fe and Ca to their corresponding products was 93.2% and 91.9%, respectively. The removal of S and As from goethite precipitates was studied by roasting with coal powder. Under the optimum conditions of the coke powder to the residue mass ratio of 4% and 1100 °C, 99.3% S and 99.5% As were removed while the goethite precipitates reached the standard of ironmaking raw materials. After drying, the calcium sulfate precipitates are used to produce cement and building materials.

中文翻译：

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磁铁矿细颗粒存在下锌湿法冶金中针铁矿和硫酸钙的磁选与循环利用。

针铁矿工艺中，针铁矿（α-FeO​​OH）和硫酸钙（CaSO ₄ ·2H ₂ O）是锌湿法冶金中铁氧化物残留的主要固体成分。将这些残留物蓄积在尾矿池中，维护成本高昂，对当地环境构成了巨大威胁。在这项研究中，磁分离施加到分离的针铁矿从硫酸钙与磁赤铁矿（γ-的Fe ₂ ö ₃）细颗粒作为载体，通过焙烧-1μm的纯磁铁矿矿物颗粒而制得。SEM图像和XRD图表明针铁矿过程中针铁矿在磁赤铁矿细颗粒上的沉淀，使针铁矿聚集体具有磁性，而硫酸钙形成非磁性的块状沉淀。然后使用磁鼓分离器将针铁矿-磁赤铁矿聚集体与硫酸钙沉淀物有效分离。铁和钙的回收率分别为93.2％和91.9％。通过用煤粉焙烧研究了从针铁矿沉淀物中去除S和As的方法。在最佳条件下，焦粉对渣油的质量比为4％和1100°C，S为99.3％，99。当针铁矿沉淀达到炼铁原料标准时，去除了5％的As。干燥后，硫酸钙沉淀物用于生产水泥和建筑材料。