Laterite Ore Research Articles

Ternary extractant system consisting of PC-88A, TOPO, and Versatic 10 for recovery of scandium(III) from nickel laterite processing liquors

Solvent extraction of scandium(III) from an aqueous solution, which simulates a concentrated scandium solution generated from nickel/cobalt mixed-sulfide production process, was performed using a ternary mixed extractant system. Addition of tri-n-octylphosphine oxide and a long-chain alkyl carboxylic acid (Versatic 10) to an organophosphonic ester (PC-88A) drastically improved the separation factor of scandium over zirconium in comparison with that of a single extractant system. The optimum mixing ratio in the ternary extractant system was 10 mol% PC-88A, 60 mol% tri-n-octylphosphine oxide, and 30 mol% Versatic 10. The degree of scandium extraction was 90%, and the separation factors between scandium and other metals (i.e., Al, Fe, Ni, Cr, and Zr) were > 140 at pH 2 with the optimized ternary extractant system. The operating conditions for a countercurrent multistage extraction of scandium were investigated by McCabe–Thiele analysis. Ninety-nine percent recovery from 1800 mg dm−3 scandium was achieved by two- to three-stage countercurrent extraction at the flow ratio (A/O) = 1.01. The stripping efficiency of scandium reached >98% with 7 mol dm−3 H3PO4. Based on the results, a conceptual flowsheet for scandium recovery from waste solutions of laterite ore leachate is proposed.

A comprehensive kinetic investigation on sulfur deportment during nickel laterite calcination using model-free, model-fitting, and master plot approaches

The rotary kiln-electric furnace process is the most common method for ferronickel production from laterite ore. Since sulfur deteriorates the mechanical properties of ferronickel, it is essential to examine the routes through which sulfur is transferred to the nickel-containing product during the extraction process. Oxidation of fuel (e.g., coal) in the calcination kiln emits SO2, which results in sulfur transfer from the gas to the calcine. In this investigation, coal combustion atmosphere was mimicked by purging N2-CO-CO2-SO2 gas mixture in the tube furnace. A comprehensive kinetic analysis on the sulfurization of nickel laterite ore was conducted to obtain a fundamental understanding of the rate of the sulfurization reactions. The kinetic investigation was performed by three approaches: model-free, model-fitting, and master plot at various processing times, temperatures, and partial pressures of SO2. The XRD and ICP analyses were used to determine the phase composition and sulfur content of the calcine, respectively. Considering the activation energy values obtained by model-free approach, the process is divided into two steps, before and after 60 min of calcination. Contracting sphere and Avrami Erofeev are identified as the most suitable kinetic models for steps 1 and 2, respectively. Considering the small values of activation energy, 1.4–5.3 kJ/mol, the sulfurization reactions are identified as diffusion-controlled mechanism.

Nickel Recovery Optimization and Kinetic Study of Morowali Laterite Ore

Nickel plays a critical role in the mining industry. However, the presence of nickel in the primary source of sulfide minerals is decreasing. Focus has since turned to laterite ore, which contains up to 80% Ni metal. The purpose of this study was to optimize nickel leaching using sulfuric acid and conduct a kinetic analysis to discover the mechanism that best controls the leaching process. To optimize the operating conditions, the response surface method (RSM) with a Box–Behnken design was used. The shrinking core and Zhuravlev, Leshokin, and Templeman (ZLT) models were used to assess the kinetics of the nickel leaching process. Mineral characterization was also performed to gain a better understanding of the sample characteristics. At 2 M sulfuric acid concentration, 10% solid–liquid ratio, and 90 °C temperature, the highest observed Ni recovery was 87% and the apparent activation energy was 32.75 kJ/mol.

Determination of scandium in ash and slag wastes and products of their processing by instrumental neutron activation analysis

Abstract Ash and slag waste accumulated throughout the world in appreciable amounts are, in essence, man-made deposits and are of interest as a potential source of critical elements, in particular Sc, as well as raw materials for obtaining construction materials. Coals from Siberia and the Far East are used as fuel at thermal power plants (TPPs) in the Primorsky Territory of Russia. These coals are characterized by a high Sc content. The content of Sc in the ash and slag wastes from landfills of six TPPs in Primorsky Krai was determined by neutron activation analysis with a Cf-252 radionuclide source. The Sc content ranged from 5.1 to 52.7 ppm. Average concentrations of Sc in ash and slag waste are 23.3 ppm. Verification of the INAA method was carried out by comparing with the ICP-MS data in reference materials (laterite and carbonatite scandium-containing ores). The possibility of using the Sc-46 isotope, produced by thermal neutron activation, as a radioactive tracer to assess the effectiveness of operations for Sc extraction and concentration is shown. Sc has been preconcentrated from the initial ash of the Primorsky thermal power plant by the precipitation method in the form of hydroxide, followed by separation from accompanying elements by dissolving the hydroxide in sodium hydroxide or hydrochloric acid. The possibility of concentrating Sc more than 4 times from the initial ash has been shown.

Phase transformation in the metallic reduction process of low-grade laterite nickel ores for ferronickel alloy production

The utilization of low-grade laterite ores has become necessary due to the intensive mining of high-grade nickel sulphide ores for a long time. In this study, metallic reduction roasting followed by magnetic separation to produce ferronickel alloy and abandon gangue minerals provides an effectively treatment for laterite ores. The experimental results indicate that ferronickel alloy containing more than 7.5% Ni with its recovery of 95% and more than 70% Fe with its recovery of 90% was produced successfully from the low-grade laterite ore. In the metallic reduction roasting process, the thermodynamic analysis displayed that the higher temperature promotes the conversion percentage of the oxidic nickel and iron to metallic nickel and iron. The ferronickel particle morphology with a liquid-solid growth and aggregation mechanism in the reduced laterite ore were investigated by SEM/EDS. XRD analysis revealed that the nickel laterite ore was transformed from hortonolite (MgOx · FeO2-x · SiO2) to forsterite (MgOx · CaOy · SiO2) during the metallic reduction process.

Разработка укрупнённого адсорбера для переработки продуктивных растворов

Productive solutions obtained after leaching of ores have a complex composition, including a variety of non-ferrous and heavy metal cations. The method of extracting nickel from productive solutions after leaching of sulfide and lateritic ores is the most important process in hydrometallurgical processing. Sorption by ion-exchange resins is an alternative to existing technologies for nickel recovery from productive solutions. The ability to selectively extract nickel and regenerate makes polymeric ion-exchange resins one of the most popular sorbents in the modern world. The polymer resin sorption process avoids wastage of reagents, costly filtration, and poor nickel selectivity compared to other metal ions associated with solvent extraction processes. In order to conduct experimental studies of sorption using Amberlite IRC 748 polymer resin, it is necessary to calculate and design an adsorber. The objectives of the study include the determination of the geometric parameters of the adsorber, the parameters of the sorption/desorption process and the development of a process flow diagram. As a result of the research, an enlarged adsorber has been designed to extract nickel from the productive solution after bacterial-chemical oxidation of cobalt-copper-nickel sulfide ore, and a process flow diagram for the process of obtaining nickel salts from the productive solution has been developed. The volume of the adsorber, its height, diameter, diameter of the inlet fitting, the height of the sorbent layer, the required resin flow rate, and the duration of the process before regeneration are determined. To ensure the continuity of the process, taking into account the duration of bacterial-chemical oxidation, periodic regeneration of the sorbent, the number of adsorbers in a common installation is taken to be two. When the adsorption stage occurs in one of the apparatuses, the stage of regeneration and drying of the polymer resin proceeds in the other. The estimated sorption capacity of Amberlite IRC 748 resin was taken as 21.6 g of nickel per 0.1 kg of adsorbent. Resin desorption has been supposed to be carried out with a 10 % sulfuric acid solution, at a flow rate of 5 l/h.

SEDIMENTARY MANGANESE DEPOSITS IN CARAJÁS, BRAZIL

The Carajás Mineral Province in Brazil is actually one of the most important in the world because it contains world-class mineral deposits (Fe, Cu, Au, Ni and Mn), partly enriched by lateritic weathering (Fe, Mn, Ni). It carries at least four manganese ore deposits: Azul, Buritirama, Sereno-Conquista and Buriti, of these Azul and Buritirama are productive mines. The Azul deposit is the earliest known and was initially considered as typically lateritic. Further studies show that much of the reserves are classically associated with carbonaceous gray to black mineralized shales and enriched in manganese oxyhydroxides, where cryptomelane is the major ore mineral, enveloped by thick packets of red siltstones and sandstones of lower age Proterozoic (around 2.1 Ga). The mineralogical composition of rocks and ore, isotopic data, abundance of carbonaceous organic matter and the presence of stromatolite structures show deposition in a shallow platform, where the source of manganese and associated metals were mainly of ocean hydrothermal origin, while the sediments of the rocks would have a main continental source from Archean rocks. Rhodochrosite is restricted and diagenetic, likely pyrite. Tectonic deformations reached the whole package and provided environment and structures for remobilization and reprecipitation of Mn-oxyhydroxides of high content and crystallinity. These two types of ores were the source of lateritic ore and colluvionary, already practically depleted

IRON REMOVAL PROCESS FROM NICKEL PREGNANT LEACH SOLUTION USING SODIUM HYDROXIDE

Indonesia is a country that has abundant mineral resources, including nickel resources in laterite ore. Nickel demand has risen significantly because of the need for nickel precursors for battery production. Nickel laterite can be processed via the hydrometallurgical route to obtain nickel precursor by leaching the laterite ore with an acid solution to produce a nickel-rich solution or Pregnant Leach Solutions (PLS). This nickel-rich solution is then processed by precipitation with a base solution to make its hydroxides known as Mixed Hydroxides Precipitate (MHP). MHP is the main product that contains nickel and cobalt for making the material for a lithium battery. PLS usually contain iron impurity, which also dissolves when the ore is leached. Therefore, the iron needs to be separated to make high-purity MHP. To solve this problem, synthetic PLS contained nickel, cobalt, and iron, and their concentration was simulated to match the general PLS composition. From the experiment, it was observed that iron could be precipitated at two stages at solution pH of 3 and 3.5 using 2.5 M NaOH solution. After that, nickel and cobalt can be precipitated at higher pH. To study the effect of pH and temperature on the yield of nickel and cobalt precipitation, precipitation at pH of 7, 8, and 9; and temperature of 70, 80, and 90 °C was conducted. The results show that the highest yield was obtained at a pH of 9 and temperature of 90 °C, with precipitation yield of nickel and cobalt at 99.03% and 98.78%, respectively.

COMPORTAMENTO TÉRMICO DE 25°C A 1100°C DO MINÉRIO DE NÍQUEL DA MINA ONÇA-PUMA EM CARAJÁS

Ferronickel alloys are produced by pyrometallurgical processes from nickel-bearing hydrous magnesium silicates occurring in the saprolite in laterite deposit of the Serra de Onça-Puma/Pará-Brazil. The ore is treated by RKEF process. It consists of drying, calcination and reduction, however, the processing of lateritic nickel ore is quite difficult since the Ni-bearing minerals are finely disseminated in the ore bodies. In this work was studied the influence of thermal treatment between 25°C and 1100°C in nickel lateritic ore, evaluated through thermal analysis (Tg/DTA) and x-ray diffraction (XRD). The XRD analyses of raw samples without thermal treatment showed that they are mixture of serpentine, smectite and chlorite. After starting thermal treatment, the curves of Tg/DTA revealed to have two endothermic peaks at 60°C to180°C and 594°C to 613°C due to release the adsorbed and crystalline water, respectively, followed by an exothermic peak at 820ºC which can be attributed to the change in crystal structure and consequent formation of a new mineral phases. Weight differences can be observed when the adsorbed water removed, without phase changes in the range of 60°C to 180°C, indicated stability of nickel ore. Phase changes and weight loss were observed at 594°C to 613°C with clear crystalline breaking of the serpentines and smectite forming amorphous substances. Above this temperature new phases are crystallized until 820°C, when is formed forsterite (trevorite), enstatite and hematite, remaining unchanged quartz. On the analyzed conditions might infer that the pyrometallurgical to iron nickel production through this type of laterite ore effectively corresponds to RKEF process.

Kinetika Leaching Ni dan Fe dari Bijih Laterit Tipe Limonite Morowali

Nickel (Ni) deposits are depleting, while demand for the metal is increasing. To address this problem, valuable metals such as Ni and Fe can be extracted from secondary sources such as limonite-type laterite ores. The goal of this study was to investigate the influence of leaching temperature on Ni and Fe recovery, as well as the best kinetic model to represent the leaching process of these metals. Temperature has a considerable impact on the leaching process of Ni and Fe. Increasing the temperature from 30 to 90 oC can increase the recovery of Ni by 50% and Fe by 70 %. Ni and Fe recoveries were highest at 93.21 % and 95 %, respectively. Kinetic analysis of the two metals' leaching processes was also performed. It was discovered that the diffusion process controls Ni leaching, which can be represented using the Zhuravlev kinetic model, whereas chemical reactions on the surface of the unreacted core controls Fe leaching. The activation energies for leaching Ni and Fe are 36.53 and 40.32 kJ/mol, respectively. 1930 exp ((-36.53 kJ/mol)/(R.T))t=[(1-X)-1/3)-1]2 is the kinetic equation for Ni leaching. The kinetic equation for Fe leaching is 3903 exp ((- 40.32 kJ/mol)/(R.T)t=1-(1-X)1/3.

A novel method: Nickel and cobalt extraction from citric acid leaching solution of nickel laterite ores using oxalate precipitation

In this study, an alternative method for recovering nickel and other valuable metals from nickel laterite ores is proposed and evaluated. The proposed method comprises a leaching step using citric acid to dissolve the nickel and cobalt from Indonesian nickel laterite ores, and subsequently, an oxalate precipitation step to precipitate the nickel (and cobalt) from citric acid leach filtrate. The results of the leaching experiments showed that nickel (and cobalt) can be dissolved in the leaching step using 1 M citric acid solution at 80 °C, a pulp density of 100 g/L, and leaching duration of 5 h. The results of the oxalate precipitation experiments showed that complete precipitation of nickel can be achieved at 80 °C, 500 rpm stirring speed, and precipitation duration of 3 h. This proposed method can produce Mixed Oxalate Precipitate (MOP) with a purity of 78 %.

Cytotoxicity of fibrous antigorite from New Caledonia

Exposure to asbestos and asbestos-like minerals has been related to the development of severe lung diseases, including cancer and malignant mesothelioma (MM). A high incidence of non-occupational MM was observed in New Caledonia (France) in people living in proximity of serpentinite outcrops, containing chrysotile and fibrous antigorite. Antigorite is a magnesium silicate, which shares with chrysotile asbestos the chemical formula. To achieve information on antigorite toxicity, we investigated the physico-minero-chemical features relevant for toxicity and cellular effects elicited on murine macrophages (MH-S) and alveolar epithelial cells (A549) of three fibrous antigorites (f-Atg) collected in a Caledonian nickel lateritic ore and subjected to supergene alteration. Field Atg were milled to obtain samples suitable for toxicological studies with a similar particle size distribution. UICC chrysotile (Ctl) and a non-fibrous antigorite (nf-Atg) were used as reference minerals.A high variability in toxicity was observed depending on shape, chemical alteration, and surface reactivity. The antigorites shared with Ctl a similar surface area (16.3, 12.1, 20.3, 13.4, and 15.6 m2/g for f-Atg1, 2, 3, nf-Atg, and Ctl). f-Atg showed different level of pedogenetic weathering (Ni depletion f-Atg1 ≪ f-Atg2 and 3) and contained about 50% of elongated mineral particles, some of which exhibited high aspect ratios (AR > 10 μm, 20%, 26%, 31% for f-Atg1, 2, and 3, respectively). The minerals differed in bio-accessible iron at pH 4.5 (f-Atg1 ≪ f-Atg3, < f-Atg2, nf-Atg < Ctl), and surface reactivity (ROS release in solution, f-Atg1 ≪ f-Atg2, 3, nf-Atg, and Ctl). f-Atg2 and f-Atg3 induced oxidative stress and pro-inflammatory responses, while the less altered, poorly reactive sample (f-Atg1) induced negligible effects, as well nf-Atg. The slow dissolution kinetics observed in simulated body fluids may signal a high biopersistence. Overall, our work revealed a significative cellular toxicity of f-Atg that correlates with fibrous habit and surface reactivity.

Development of laterite ore processing and its applications

Nickel ore is found in two types sulfide and laterite. The sulfide is a nickel ore that has high nickel content and low reserves of natural resources than of the zinc laterite. In contrast, the laterite is a rock mineral that contains the iron-nickel oxide compounds. There are two methods of processing nickel laterite, namely hydrometallurgy and pyrometallurgy. The former is a method that uses leaching by a chemical solution or solid such as acid, as a reducing agent. The alkaline leaching (ammonia) is the most optimal method to obtain a nickel grade with the highest recovery but it needs more modification. Pyrometallurgical method uses high heat up to 1800°C, so it requires a lot of energy and needs improvement to decrease the carbon usage. The rotary kiln-electric furnace method is the optimal method for developing the nickel laterite. These methods generate products that can be applied to various fields. For example, the pyrometallurgy method produces nickel pig iron and ferronickel as raw materials for stainless steel and steel alloys. The hydrometallurgy method produces nickel sulfate and nickel oxide with a purity of 99% by weight as raw materials for magnets, sensors, and batteries. Hence, the hydrometallurgy method still needs improvements for the environmentally friendly reagent. Therefore, bioleaching will be a nickel laterite leaching process in the future by using bacteria as the reducing agent.

Kinetic study in selective reduction of limonitic and saprolitic nickel ore

ABSTRACT Saprolite and limonite have different behaviour in the carbothermic reduction process due to the differences in their atomic structures. This work investigates the kinetic study of these two different kinds of lateritic nickel ores. Nickel ore, coal, sodium sulfate, and calcium oxide were mixed, then pelletised into 10–15 mm diameters. The pellets were reduced with a non-isothermal condition using a muffle furnace at 950–1150 °C for 5–120 min. The reduced pellets were crushed into less than 74 µm prior to the wet magnetic separation process to obtain concentrates (ferronickel) and tailings (impurities). The result showed that the reduction rate for both lateritic nickel ores increased with the increase of reduction temperature and holding time. The Ginstling-Brouhnstein model was appropriate to describe the diffusion mechanism of the reduction process of limonite and saprolite. The activation energy in the reduction of limonite was lower than in saprolite. It indicated that the iron and nickel in magnesium silicate in saprolite have lower reducibility than the oxide structure in limonite. Modifying basicity in nickel laterite with CaO addition could also reduce the activation energy.

Ammonia leaching process for selective extraction of nickel and cobalt from polymetallic mixed hydroxide precipitate

Nitric acid pressure leaching process (NAPL) uses nitric acid as the leaching medium to produce cobalt and nickel raw materials. Based on the benefits of nitric acid pressure leaching process for laterite ore, this paper proposes a process of "nitric acid pressure leaching-neutralization precipitation-reductive ammonia leaching separation". Firstly, thermodynamic analysis confirmed the possibilities of nickel and cobalt leaching from ammonia solution. Then the impacts of leaching agent composition, temperature, time, and liquid-solid ratio on nickel and cobalt extraction ratios were investigated. Finally, the leaching behaviors of nickel and cobalt during ammonia leaching were investigated using the shrinking core model. In addition, the phase and morphology of the leach residue were studied using X-ray diffraction (XRD) and scanning electron microscope/energy dispersive spectrometer (SEM/EDS). The reductive ammonia leaching method for treating MHP results in high nickel and cobalt extraction ratios, good separation results, and recyclable material, all of which have significant industrial application value.

The study for reduction roasting of laterite residue in the presence of CaF2

Lately, an increasing number of companies invested in the hydrometallurgical process of laterite ores. In the meantime, the research on disposal of laterite residue has come under spotlight the sake of environmental protection, economic efficiency, and resource utilization. Consequently, reduction roasting process in the presence of CaF2 is proposed to treat laterite residue efficiently and recover valuable components. The thermodynamic calculation was conducted to study the mechanism of phase transformation and roasting in the presence of CaF2. It is found that CaF2 would react with iron olivine and chromite to release iron and chromium. In addition, the addition of CaF2 avails the reduction, migration, aggregation, and growth of metallic Fe and Cr. The optimal conditions for addition of CaF2 and temperature is 10% and 1200 °C, respectively. The recovery of chromium reached 95.61% at 10% CaF2 addition from 65.86% without CaF2 addition and the metallization reduction of iron increased from 77.2% to 91.87%. The function of CaF2 was further investigated by the microstructure evolution of roasting products.

On the Cobalt Content Upgrade in Nickeliferous Laterites Using Iron (III) Sulfate: A Study Based on Thermodynamics Simulations

Nickel (Ni) and cobalt (Co) are relevant technological metals for the future of the lithium-ion battery (LIB) industry. Based on the current and projected demand for these, an increased interest in developing processing routes to exploit lateritic occurrences has been observed, as these are reported as critical raw materials for future mineral–metallurgical industry. However, the content of Ni and Co in such ores is minimal and requires impracticable mineral-processing operations for concentration before metal extraction. It was identified that information regarding the sulfation roasting of this material is scarce on what concerns the iron sulfates interaction as a function of the temperature. Based on that context, the present work has its purposes associated with the proposition of an alternative chemical pretreatment to upgrade the content of metals of technological interest in lateritic ores through a simple roast–leach process. Thus, the chemical interactions between the mineral sample and iron (III) sulfate (Fe2(SO4)3) through thermodynamic simulations and experimental procedures were explored. The latter included specific water leaching practices for the selective concentration of metals. The equilibrium calculations indicate that Fe2(SO4)3 and FeSO4 tend to decompose at lower temperatures, and considering the higher stability of other metal sulfates, it could be an interesting reagent in this type of process. Regarding the experimental results, the characterization of materials indicates a recovery of Co as high as 73.4 wt.% after sulfation roasting at 500 °C followed by water leaching, with the full content of Iron (Fe) being reported in the insoluble phase. Based on these findings, the present development could be an interesting alternative to consider within operations for the chemical upgrade of cobalt in such types of mineralogical occurrences.

An alternative route to extract nickel and cobalt from non-commercial laterite ore

Laterite ores, which represent around two-thirds of nickel reserves, became an important source of nickel and cobalt metals. The objective of the present study was to investigate the efficiency of a hybrid route to extract nickel and cobalt present in a laterite ore sample which was not commercially attractive to be processed through the current routes. The process efficiency was investigated through the application of different test conditions, such as roast temperature, ore sample comminution, and moisture. Chemical analysis by atomic absorption was used to quantify the metals. The solid phase’s identification and characterization were accomplished by X-ray diffraction and Scanning Electron Microscopy. The Rietveld Method was used for the mineral’s phase quantification. In terms of nickel and cobalt extractions, the most favorable condition was: particle size smaller than 38 µm, 50% sulfuric acid (wt.%), and 10% moisture (wt.%), which permitted nickel, cobalt, magnesium, and iron recoveries of 84.5%, 92.0%, and 93.0%, 27.0% respectively. These results indicate the successful application of the route. In addition, it was found that chlorite, chromite, hematite, and goethite were identified as the main nickel and cobalt carriers present in the process residue.

CO2 mineral sequestration and nickel recovery from laterite ore by using waste copperas

CO2 mineral sequestration is one of the most promising strategies for combating global warming, which is composed of direct and indirect pathways. However, the high cost and heat consumption for recycling reagents used in the indirect carbonation process is the biggest obstacle for its widespread applications. In this study, a novel process by using a solid waste, copperas, as reagent to extract magnesium and nickel from laterite ore was proposed for simultaneous CO2 mineralization and recovery of nickel. In this process, the copperas was decomposed into SO2, which sulfated the laterite ore by in situ gas–solid reaction. The addition of Na2SO4 facilitated the formation of low melting point substances, converting the gas–solid reactions into a multiphase gas–liquid-solid reaction, thus the extraction was enhanced. Meanwhile, the heat of sulfation of laterite ore can compensate the heat of copperas decomposition, reducing the overall energy consumption. The maximum extraction efficiency of 94 % for Mg and 87 % for Ni was achieved at Na2SO4 dosage larger than 10 wt%. The carbonation of MgSO4-riched leachate experiments revealed the optimal CO2 storage capacity was approximately 291 kg·t−1 laterite ore. Compared with the conventional acid-based Mg extracted process for CO2 mineralization, the cheap copperas avoided the recycle of reagent and obtained weak acidic leachate, reducing the amount of alkali used in the subsequent carbonation process.

Effective separation and recovery of iron and chromium from laterite residue in the presence of calcium chloride

In nitric acid pressure leaching (NAPL) for the treatment of limonitic laterite ores, the comprehensive utilization of leach residue is significant for resource recovery and environmental protection. In this work, the recovery and separation of iron and chromium from NAPL residue by metallization reduction roasting−magnetic separation with calcium chloride as additive was studied. The following optimum parameters were obtained: 1100 °C roasting temperature, 25 % reductant dosage, 40 min roasting time, 7 % calcium chloride dosage, 200 mT magnetic field intensity, and 40 s rod mill time (D50 = 7.20 µm). Under these optimum conditions, 81 wt% iron content in the concentrate and 7.4 wt% chromium in the tailings were obtained. The corresponding recovery rates of iron and chromium were 95 % and 64 %, respectively. The microstructure and composition of leach residue and process products were investigated by SEM, EDS, and XRD to study the phase transition and polymerization of substances during roasting. The results showed that iron was mainly enriched in the magnetic concentrate, and chromite and silicate minerals dominated the tailings. Analysis of the action of calcium chloride in the reduction roasting revealed that calcium chloride was beneficial for the liberation of Fe from fayalite and the migration and polymerization of iron.