Advances towards a Clean Hydrometallurgical Process for Chromite

Abstract

Abstract:Because of the acute toxicity of Cr(VI)-bearing substances, the pollution problem caused by chromite process residue has become a worldwide concern. In the view of relevant studies, the technologies based on the alkali treatment cannot fundamentally resolve the pollution problem, because the oxidation of Cr(III) to Cr(VI) is unavoidable during chromite decomposition. In contrast, the oxidation of Cr(III) to Cr(VI) can be controlled by the sulfuric acid treatment of chromite, and the Cr(VI) pollution can be eliminated from the original source of production. Many research studies focusing on the resolutions of the key obstacles hindering the development of the sulfuric acid treatment process have been carried out, and significant progress has been achieved. In this study, a clean hydrometallurgical process without the generation of hexavalent chromium is demonstrated. First, the chromite was decomposed and leached by sulfuric acid solution in the presence of an oxidant. Then, iron was hydrothermally removed from the acid solution as the precipitate of jarosite. Finally, chromium salts were obtained by adjusting the basicity of the solution, separation and drying. With the aim of realizing industrialization, future research emphasis on the development of the sulfuric acid treatment process is proposed in this study.

Hazardous Waste Disposal in Stromatolitic-Limestone Terrain and Hexavalent Chromium Contamination in Chhattisgarh State, India

“…As pH decreases to <10, most of the Cr(VI)-bearing minerals will become unstable and their dissolution contributes to the increase in Cr(VI) concentration in a leachate solution. 27 …”

Mineral processing: leaching process of chromium and recovery of platinum group elements from Northwestern Saudi Arabian Ophiolitic chromite

“…lithium tetraborate flux [23], sodium peroxide fusion and mixtures of HNO 3 , HF and HClO 4 [21], MnO 2 -LiSO 4 -sulphuric acid mixtures [24]. In this study, four Saudi Arabian chromite ore samples collected from Wadi Al Hawanet (samples I-III) and Jabal Al Wasq (sample IV) areas were digested in the acid mixture of HClO 4 -HNO 3 Antony et al [26] and Zhang et al [27] have been processed chromite ore by roasting with sodium carbonate, limestone and dolomite at 1000-1200 °C [27]. In the current study, the traditional method [26] was used for the recovery of chromate based chromite-Na 2 CO 3 roast ore with sodium carbonate has been carried out with some modifications as follows:…”

“…PGE's were collected in Na 2 CrO 4 liquor while the majority of Ni (0.5% as NiO) was retained in the roast residue. Leaching with water offers a simple, an eco-friendly and cost-effectiveness approach for the production of a basic chromium sulfate product with high quality yield with minimum iron content (< 0.1% m/m) required for the tanning industry compared to the method reported [27]. Basic chromium sulfate product is nearly free from iron content when compared to the published methods.…”

“…The liquors containing Na 2 CrO 4 obtained in the previous experiments were acidified with sulfuric acid to form Na 2 Cr 2 O 7 according to the following equation [27]:…”

Recovery of chromium from residue of sulfuric acid leaching of chromite

“…To avoid the formation of Cr(VI) from the source, a sulfuric acid leaching process was proposed and extensively studied (Zhao et al, 2015(Zhao et al, , 2017Zhang et al, 2016). Literature indicates that in this process, with a suitable oxidant, chromium can be extracted from chromite in trivalent state using a heated sulfuric acid solution (Geveci et al, 2002;Liu et al, 2011).…”