Red mud is an inevitable and under-utilized byproduct of the aluminium industry. The current study evaluates the effect of mechanical and thermal activation on the acid leaching of red mud. The acid leaching of the pretreated product is followed by acid-base treatment to precipitate the dissolved aluminium values from solution and enrich the residue with Fe and Ti values. Mild acid leaching yielded ~76% aluminium dissolution with 81% silicon removal. The direct acid leaching resulted in dissociation of sodium aluminosilicate; meanwhile, gibbsite phase remains in the residue. The mechanical milling for 1 h enhanced the aluminium dissolution to 89.5% with silicon and iron dissolution of 98.5 and 9.6%, respectively. The silica and iron oxide values were separated before HCl leaching by thermal pretreatment step using microwave heating with NaOH and carbon additives respectively. The sodium silicate and sodium aluminate phases formed during alkali thermal treatment resulted in ~33% silicon and ~ 27% aluminium removal by water washing. Meanwhile, HCl leaching of the water wash residue resulted in 82% aluminium dissolution with 70% recovery and residue containing ~52% Fe₂O_3, and 28% TiO₂ is obtained. The carbothermal reduction yielded iron-rich magnetic concentrate having 48% iron grade with 20% metallic iron, and ~ 83% iron recovery. Leaching of the non-magnetic fraction containing hercynite and fayalite as the major aluminium and silicon bearing phases resulted in 81% aluminium dissolution with overall aluminium recovery of only 37%. Mullite formation is also observed in the precipitate with a high Al/Si molar ratio. The carbothermal route was found as an energy-efficient route, whereas the mechanical milling route yielded maximum Al extraction of ~90% with Fe and Ti content of 41.1% and 16.8% in the residue.

赤泥是铝行业不可避免且未得到充分利用的副产品。当前的研究评估了机械活化和热活化对赤泥酸浸的影响。预处理产品的酸浸之后，进行酸碱处理，以从溶液中沉淀出溶解的铝原子，并用Fe和Ti原子富集残余物。轻度酸浸会产生约76％的铝溶出度和81％的硅去除率。直接的酸浸导致铝硅酸钠的离解；同时，残渣中保留了三水铝石相。机械研磨1小时将铝的溶解度提高到89.5％，硅和铁的溶解度分别达到98.5和9.6％。在通过热预处理步骤分别使用NaOH和碳添加剂分别进行微波加热的HCl浸出之前，分离二氧化硅和氧化铁值。在碱热处理过程中形成的硅酸钠和铝酸钠相导致水洗除去约33％的硅和约27％的铝。同时，水洗残渣的HCl浸出导致铝溶出82％，回收率70％，残渣中含〜52％Fe₂ O _3，得到28％的TiO ₂。碳热还原产生的富铁磁性精矿具有48％的铁品位和20％的金属铁，以及〜83％的铁回收率。含锂铁矿和方铁矿作为主要含铝和含硅相的非磁性馏分的浸出导致铝溶出量为81％，而铝的总回收率仅为37％。在具有高Al / Si摩尔比的沉淀物中也观察到莫来石形成。碳热途径被认为是一种节能途径，而机械碾磨途径产生的最大铝提取量约为90％，而铁和钛的含量分别为41.1％和16.8％。