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chromite ore processing residue (COPR) is an inevitable solid emission in chromite salt production. It is an industrial waste produced during the extraction of Cr(VI) from a …
This chapter contains sections titled: Introduction Crystal Structure of Chromite Minerals Thermal Decomposition of Chromites Alkali Roasting of Chromites …
A new leaching process for preparing chromium oxide from chromite was studied for this paper, using Cr(VI) extracted from the remediation treatment of chromite ore processing residue (COPR) as an ...
The sulfuric acid leaching kinetics of South African chromite was investigated. The negative influence of a solid product layer constituted of a silicon-rich phase and chromium-rich sulfate was eliminated by crushing the chromite and by selecting proper leaching conditions. The dimensionless change in specific surface area and the …
The sulfuric acid leaching process is regarded as a promising, cleaner method to prepare trivalent chromium products from chromite; however, the decomposition mechanism of the ore is poorly understood. In this work, binary spinels of Mg-Al, Mg-Fe, and Mg-Cr in the powdered and lump states were synthesized and used as raw …
Batch tests were conducted to assess the potential use of ferrous sulfate and calcium polysulfide for the remediation of chromite ore processing residue (COPR). The remediation process entails addition of ferrous sulfate or calcium polysulfide to chemically reduce hexavalent chromium [Cr(VI)] to trivalent chromium [Cr(III)] in slurry form and pH …
This paper introduces various treatment processes for chromite, highlighting the clean advantages of the acid leaching method. Based on the current difficulties in separating chromium and iron in chromite acid leachate, the research status of separating chromium and iron in recent years is reviewed from the perspective of four extraction …
Direct leaching of oxidic PGM ore using different acids yielded relatively low PGM extractions. Leaching in hydrochloric acid achieved extractions of 36.6% Pt and 8.8% Pd, nitric acid achieved extractions of 34.5% Pt and 7.1% Pd. The best leaching results were obtained using aqua regia, with extractions of 48% Pt and 24.5% Pd. In view of the ...
A process flow diagram indicating the likely process steps to be utilized for pelletized pre-reduction before acid leaching to improve the Cr/Fe ratio of chromite. In this general process flow diagram ( Fig. 1 ), Process steps 1–5 are based on the currently applied pelletized chromite pre-reduction process.
Leaching of Light Rare Earth Elements from Sichuan Bastnaesite: A Facile Process to Leach Trivalent Rare Earth Elements Selectively from Tetravalent Cerium. …
The Fe content in the FeCr produced depends on the chromite spinel Cr/Fe ratio. Therefore, the selective removal of Fe from the chromite spinel using different …
This chapter contains sections titled: Introduction Crystal Structure of Chromite Minerals Thermal Decomposition of Chromites Alkali Roasting of Chromites Leaching of Chromite Minerals Ch...
African chromite ore is processed for the extraction of chro- stoichiometric amount of sodium carbonate required for the mium as sodium chromate. The oxide constituents of South formation of sodium chromate. The mixture was roasted African chromite ore were determined by chemical analysis; isothermally in an alumina crucible in a temperature-con-
The sulfuric acid leaching behavior of the chromite in Zhao et al. 's study can be illustrated as shown in Figure 3, where four types …
To establish a cleaner production technology of chromium salt, the pressurized leaching process of chromite ore in 60 wt.% NaOH solution, subsequent separation of a chromium salt from the leached ...
A new leaching process for preparing chromium oxide from chromite was studied in this paper, using Cr(VI) extracted from the remediation treatment of chromite ore processing residue (COPR) as an oxidant. Thus, the "detoxification" of deposited COPR could be achieved and no new Cr(VI)-bearing substances would be generated in …
The sulfuric acid leaching process is regarded as a promising, cleaner method to prepare trivalent chromium products from chromite; however, the decomposition mechanism of the ore is poorly … Expand
Roasted ilmenite samples were treated in a two-stage leaching process, where the first step involved water leaching and this was followed by organic acid (mixture of 0.25 M oxalic and 0.01 M ascorbic acid) leaching for 2 h, so as to obtain TiO 2-rich residue. During the acid leaching, the leachates were sampled at different times for …
Sulfuric acid-based leaching is a promising cleaner method to produce chromium salts, but its feasibility for treating low Fe(II)-chromite still remains to be proven. A Box–Behnken design (BBD)-based set of experiments for sulfuric acid leaching of low Fe(II)-chromite was utilized in this work for generating an experimental dataset for …
1. Introduction. The production of chromate from the roasted chromite produces millions tons of Chromite Ore Processing Residue (COPR) annually [1], [14].Due to the industrial incomplete roasting and leaching, about 6 wt% of Cr remain within COPR particles including 1130 − 8500 mg/kg of hazardous Cr(VI) [7].Unlike less toxic and less …
The current strategy reports the recovery of precious group metals (PGMs) from Na2CO3 roast of Saudi Arabian ophiolitic chromite ore at 1160 °C under atmospheric O2. The influence of roasting temperature (960–1200 °C) and leaching agents (H2O, HCl, H2SO4) and their concentrations …
Batch leaching studies on chromite ore processing residue (COPR) were performed using acids to investigate leaching of hexavalent chromium, Cr(VI), with respect to particle size, reaction time, and type of acid (HNO 3 and H 2 SO 4).Aqueous Cr(VI) is maximized at approximately 0.04 mol Cr(VI) per kg of dry COPR at pH 7.6–8.1.
The extraction of chromate from chromite via the sulfuric acid leaching process has strong potential for practical use because it is a simple and environmentally friendly process. This paper aims to study the sulfuric acid leaching process using chromite as a raw material via either microwave irradiation or in the presence of an …
The sulfuric acid leaching process is regarded as a promising, cleaner method to prepare trivalent chromium products from chromite; however, the decomposition mechanism of the ore is poorly … Expand
In order to improve the chromate salts cleaner production technology, a pressure leaching process for chromite ore in 50 wt% KOH solution was studied for the first time and the results were presented in this manuscript.It was found out that the chromium extraction rate increased significantly with the increase of temperature and …
Chromium ore processing residue (COPR) is classified as hazardous solid waste because of the leachable Cr(VI). Cementitious materials are often used to solidify and stabilize heavy metals. However, most of them focus on the leaching concentration of particles after solidification and stabilization and lack research on leaching …
The leaching kinetics study indicated that the leaching process of chromium was controlled by the surface chemical reaction between the chromite ore …
The novel extraction route may be able to displace the current oxidative process for chromite ore processing by retrofitting. Remediation of the vanadium slag processing residue and recovery of the valuable elements ... The sulfuric acid leaching process is widely considered to be a cleaner technology to prepare chromium salt from …
Safe management and disposal of chromite ore processing residue (COPR) is an unsolved global problem. In spite of several global research efforts, the problem of safe management of COPR and redemption of dump sites has remained unsolved. There is a high risk for all living beings in and around the COPR dump sites due to prevailing …
The sulfuric acid leaching process is regarded as a promising, cleaner method to prepare trivalent chromium products from chromite; however, the decomposition mechanism of the ore is poorly understood. In this work, binary spinels of Mg–Al, Mg–Fe, and Mg–Cr in the powdered and lump states were synthesized and used as raw …
Key words: leaching; kinetics; hydrofluoric acid; hexavalent chromium; chromite ore processing residue 1 Introduction Chromite ore processing residue (COPR) is a solid …
Two most common hydrometallurgical processes are high pressure acid leaching (HPAL) and reduction roast-ammoniacal leach (Caron process). ... (nearly 8–10 times that of the ore) that is generated during chromite mining and dumped nearby has found a very little use so far. The mineralogical studies indicated that there was no …
The sulfuric acid leaching process is regarded as a promising, cleaner method to prepare trivalent chromium products from chromite; however, the decomposition mechanism of the ore is poorly ...
(b) being treated by HF acid process of the acid-soluble Cr(VI) in COPR further depends on kinetic data. 3.2 Effect of stirring rate The stirring rate (N) has little influence on the leaching efficiency of acid-soluble Cr(VI) in COPR (Fig.3). When the leaching time (t) is 60 min, Cr(VI) leaching efficiency with a stirring rate of 800 r/min is
during the leaching process and what impact dichromic acid has on it. It was found that the breakdown efficiency was strongly influenced by the Fe(II) concentration of the chromite and that dichromic acid acted as an oxidant and a catalyst in the leaching process. According to another study by Shi et al. (2017), the sulfuric acid leaching
Highlights Leaching temperature, leaching duration, sulfuric acid to ore weight ratio and particle size of the limonitic nickel laterite ore were studied. Optimum parameters determined as 255 o C, 0.30 sulfuric acid to ore weight ratio, a particle size of −850μ, 1 h of leaching duration with 30% w/w. 87.3% of Ni and 88.8% of Co in …
The L/S is a very crucial factor in the acid-leaching process of an ore or residue. 33 To figure out the influence of L/S, a series of experiments with varying L/S …
The leaching behavior of both the silicate and the spinel phases was investigated in the current study. Before the test, a chromite lump was polished by polisher and several types of abrasive paper to get two smooth flat surfaces. 100 mL 80 wt.% sulfuric acid and 1 g oxidant were mixed in a glass beaker on an automatic temperature …
The Fe content in the FeCr produced depends on the chromite spinel Cr/Fe ratio. Therefore, the selective removal of Fe from the chromite spinel using different combinations of chromite pre-oxidation, pre-reduction, and sulphuric acid leaching was investigated. The Cr/Fe ratio of the case study ores could be increased from 1.57 up to …