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 …Web
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The current strategy reports the recovery of precious group metals (PGMs) from Na2CO3 roast of Saudi Arabian ophiolitic chromite ore at 1160 °C under …Web
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Carbothermic reduction roasting for processing of ferruginous chromite ore using conventional and microwave heating 1. Introduction. The chromite ore occurs as a …Web
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The development of alkali roasting process has undergone three steps: the high lime roasting, the low lime roasting and the lime-free roasting. Thereinto, lime-free technology, which can prevent CaCrO 4 generation and remarkably reduce the discharged residue yield, is the most advanced chromite ore roasting technology (Weber et al., …Web
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Soda-ash roasting of the chromite mineral is commonly used worldwide for the production of watersoluble sodium chromate. The formation of sodium chromate during the soda-ash roasting reaction depends on the oxygen partial pressure and availability of oxygen at the reaction front. The effects of temperature, oxygen partial pressure, charge …Web
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Lime-based roasting is the dominant chromate salts production technology in China, and a million tonnes of chromite ore processing residue (COPR) is produced each year. However, the COPR contains carcinogenic and mutagenic chromium (VI) ion which is an important contamination source of ground and surface water (MIIT, 2012, Yi, 2004, …Web
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Chromium ore processing residue (COPR) is a hazardous waste generated during the production of chromate. Currently, approximately 10% of Cr 2 O 3 cannot be extracted after chromite sodium roasting and remains in COPR, wasting valuable Cr resources. In this study, Mg was selectively removed by using (NH 4) 2 SO 4 roasting in …Web
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Several researchers have used sodium carbonate with chromite ore in the soda-ash roasting reaction. Temperatures used are above 1073 K in air. The decomposition of sodium carbonate has resulted sodium oxide to react with chromium ion (Cr 3+) under an oxidizing atmosphere. This results into the sodium chromate formation [8, 10, 11]. The ...Web
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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 ...Web
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Oxidative alkali roasting of chromite is the state-of-the-art process for manufacturing chromium-containing chemicals, which involves dealing with serious environmental problems arising from handling Cr 6+-containing wastes generated in this process.In this article a new method for the extraction of Cr 2 O 3 from chromite ores is …Web
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To explicate the thermodynamics of the chromite ore lime-free roasting process, the thermodynamics of reactions involved in this process was calculated and …Web
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Chromium metal is obtained commercially by heating chromite ore in the presence of carbon, aluminum, or silicon, and subsequent purification (ATSDR, 2000). Sodium chromate and dichromate are produced by roasting chromite ore with soda ash and are the primary chromium salts from which most other chromium compounds are derived (ATSDR, 2000).Web
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The first and most important conclusion that can be made is that nickel and copper can effectively be leached from a complex, chromite-rich Cu-Ni-PGM ore using a sulfation roast-leach method. The results demonstrated that within the parameters of the experiments, the amount of H 2 SO 4 addition was the most influential factor to control ...Web
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Lime-based roasting is the dominant chromate salts production technology in China, and a million tonnes of chromite ore processing residue (COPR) is produced each year. However, the COPR contains carcinogenic and mutagenic chromium (VI) ion which is an important contamination source of ground and surface water ( MIIT, 2012, Yi, 2004, …Web
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Chromium chemicals are produced through alkaline roasting of chromite ore with alkali salts (such as NaOH, Na 2 CO 3, NaNO 3 or NaFeO 2 ) with or without lime addition at temperatures of 650-1200 ...Web
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In the present investigation, the oxidizing roasting process of chromite with sodium carbonate to prepare potassium dichromate crystals was studied in the microwave field with air, by heating the ...Web
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Chromium has a wide range of applications, including as an alloy addition in various steels and also as a corrosion resistance coating. Carbothermal reduction of chromite ore (FeCr 2 O 4) in a submerged arc furnace is an important industrial process for extracting chromium, but the energy consumption is excessive.It is suggested that one …Web
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Sodium chromate is produced via the soda-ash roasting of chromite ore with sodium carbonate. After the reaction, nearly 15 pct of the chromium oxide remains unreacted and ends up in the waste ...Web
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Details of the high lime roasting process of chromite ore have been reported by numerous researchers (Allied Signal, 1982, Geelhoed et al., 2002, Wazne et al., 2005). Although use of this process has ceased in the USA and the UK (Darrie, 2001) it is still actively used in various parts of the world including China, Russia, Kazakhstan, India ...Web
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Sodium chromate is produced via the soda-ash roasting of chromite ore with sodium carbonate. After the reaction, nearly 15 pct of the chromium oxide remains …Web
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Chromite ore is usually a combination of spinels with associated minerals such as calcite, magnetite, talc, serpentines and uvarovite. Chromites crystals exhibit an octahedral …Web
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Its chromite ore processing residue (COPR) includes carcinogenic and mutagenic calcium chromate ... (1200 °C) of the calcium-free roasting process of chromite ore (Antony et al., 2013b), the liquid-phase oxidation pressure leaching method achieved a high Cr leaching rate at lower reaction temperature (260 °C). It greatly reduced energy ...Web
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This study, focused on the beneficiation of a Nigerian complex chromite ore sourced from Tunga-Kaduka, Anka Local Government of Zamfara State, Nigeria, assaying 45.85% Cr 2 O 4 and 54.15% mineral ...Web
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A new green metallurgical process for chromite ore has been proposed and developed to solve the serious environmental problem in the traditional production process of chromate. In the new process, the oxidation of chromite ore is carried out in sub-molten potassium hydroxide at 300 °C. Compared with the traditional roasting process in a …Web
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The low chromium‐to‐iron ratio of chromite ores is an important issue in some chromite deposits. The value of the chromite ore is indeed dictated in the market by its iron, as well as its ...Web
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The old landfill sites, used for the dis- to use the South African chromite ores for a lime-free roast- posal of chromite ore processing residue (COPR) contain- ing process. The conversion efficiency of South African ing carcinogenic and mutagenic Cr6 ions, have now become chromite ore for the soda-ash roasting process is about 85 pct. a major ...Web
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1. Introduction. The soda ash roasting process produces Chromite Ore Processing Residue (COPR) containing 1130–8500 mg/kg carcinogenic hexavalent chromium (Cr(VI)) due to the industrial incomplete leaching (Du and Chrysochoou, 2018, Chrysochoou et al., 2009)pared with the lime-based roasting process, soda ash as …Web
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Chromium ore processing residue (COPR) is a hazardous waste generated during the production of chromate. Currently, approximately 10% of Cr2O3 cannot be extracted after chromite sodium roasting ...Web
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Soda-ash roasting of the chromite mineral is commonly used worldwide for the production of water-soluble sodium chromate. The formation of sodium chromate …Web
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Chromite ore processing residue (COPR) is a waste byproduct of chromate production that contains high levels of hexavalent chromium (Cr[VI]). ... with lime preventing dissolutio n when the roast ...Web
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Chromite ore and sodium carbonate are roasted at temperatures ranging between 900 °C and 1200 °C in oxidative atmosphere (Antony et al., 2001). Under these …Web
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