Laterite Ore Research Articles

Process development for the direct solvent extraction of nickel and cobalt from nitrate solution: aluminum, cobalt, and nickel separation using Cyanex 272

A direct solvent extraction (DSX) process for purifying nickel and cobalt from the nitric acid leach solution of nickel laterite ores was conceived and experimentally probed. The proposed process consists of two solvent extraction (SX) steps but with only one extractant — bis(2,4,4-trimethylpentyl)phosphinic acid (Cyanex® 272) — used in both steps. The first extraction step involved the removal of aluminum and zinc, whereas the second extraction step involved the separation of cobalt along with manganese from nickel. The experimental results showed essentially quantitative removal of aluminum (>97%) and zinc (>99%) in a single extraction stage using 20vol% Cyanex 272 at pH 2.1. Some cobalt (32%) and manganese (55%) were co-extracted but were easily scrubbed out completely from the loaded organic phase using dilute sulfuric acid at pH ≤ 1.38. Cobalt and manganese in the first extraction raffinate were extracted completely in four extraction stages at staggered pH values of 4.0, 4.4, 4.5, and 4.0 in the first, second, third, and fourth stages, respectively, using also 20vol% Cyanex 272. A small amount of nickel (up to 6.6%) was co-extracted but was easily scrubbed out completely with dilute sulfuric acid at pH 2.0. A flow diagram showing the input and output conditions and the metals separated under the deduced optimum conditions is presented.

High pressure sulphuric acid leaching of lateritic nickel ore

High pressure sulphuric acid leaching of lateritic nickel ore

THE INFLUENCE OF HEAT TREATMENT ON MICROSTRUCTURE AND MECHANICAL STRENGTH OF LATERITIC NICKEL STEEL

Indonesia has abundant resources of lateritic nickel ore and coal. However, this resource has not been considered as a main raw material in the Indonesian steel industry . Therefore, this study are aimed to investigate several aspects of lateritic nickel intrinsic propertiesand its potency through heat treatment process. Nickel laterite steels are usually used for bridge and building construction steel. Their properties can be improved in various ways, such as by conducting temper heat treatment. This research reported the influences of heat treatment on microstructure and mechanical strength in nickel laterite steel. Samples were austenitized at 900oC and subsquently tempered at 100 oC, 200 oC, 300 oC, 400 oC, 500 oC, and 600oC. Metallographic observation was conducted by using an optical microscope meanwhile mechanical strength were conducted by tensile test and surface hardness. The results showed evolution of mictrostructure in nickel laterite steel after heat treatment. The microstructure formed consisted of martensite temper. The presence of inclusion can affect brittle behavior of the lateritic nickel. The optimum tempering temperature was 200 oC. The result of Scanning Electron Microscope (SEM) fractography showed the dimple and intergranular fracture has caused a more ductile and mechanical behavior which is compatible with construction steels standard .

A life cycle assessment of a new laterite processing technology

This paper presents a life cycle assessment (LCA) study of three nickel laterite processing technologies. The main goal was to quantify selected environmental impact categories and to compare and analyse each impact category for three different nickel feedstock for stainless steel production. The nickel laterite processing routes were (1) high pressure acid leaching (HPAL), (2) ferronickel, and (3) the newly developed Direct Nickel (DNi Process) that involves atmospheric leaching of nickel laterite using nitric acid. A cradle to gate approach was adopted. A functional unit of one tonne stainless steel was chosen. The scope covered was from laterite ore mining to final metal production. All inventory data was expressed in units per tonne nickel-based feedstock. The flow sheets for each technology were developed and the system boundaries were clearly defined. It was found that Ferronickel has the highest global warming potential and non-renewable energy scores whereas HPAL has the highest water depletion score. Overall, the DNi Process is found to be a more sustainable processing route as it produces less airborne emissions compared to the other two routes. Nitric acid is also less toxic compared to sulphuric acid used in HPAL. The DNi Process is also able to process different types of laterite ores (from limonitic to saprolitic ores) which is an important feature for future nickel production.

Ferronickel particle formation during the carbothermic reduction of a limonitic laterite ore

Attempts to economically extract nickel from the nickeliferous laterite ores face a number of challenges, including a limited ability to beneficiate the ore prior to processing. One method to address this issue would be to reduce the ore at moderate temperatures to form a ferronickel alloy, which could then be selectively recovered to form a nickel concentrate. The current work explores the effects of varying coal, elemental sulphur and pyrite additions and temperatures in the range of 1000–1200°C on the formation of ferronickel alloy particles in a limonitic ore. It was observed that a small sulphur addition (⩽4%) yielded a significant increase in the average size of the ferronickel particles formed during reduction. A decrease in the average nickel grade of the ferronickel particles, resulting from the increased metallization of iron, was also observed in the presence of sulphur. The ferronickel particle morphology and distribution of sulphur in the reduced ore are consistent with a liquid-phase growth mechanism driven by the FeFeS eutectic at 988°C.

Considerations for Scale-Up of Ferronickel Electric Smelting Furnaces

In ferronickel smelting, the selective carbothermic reduction of calcined nickel laterite ores in large electric furnaces yields a crude ferronickel product. The optimal process for nickel laterite smelting requires a fine balance between the metallurgical requirements of the process (feed composition, nickel recovery, energy consumption, product quality) and the capabilities of the feeding, tapping and off-gas systems, and especially of the furnace crucible and electrical system. The scale-up of nickel laterite smelting operations over the last 50 years has seen a tenfold increase in furnace power input. Furnace operations within the industry are examined to identify common trends and some new metrics are proposed which incorporate the combination of electrode power densities and the impact of alloy nickel grade on gas generation rates, and hence local electrode gas fluxes, which may impact on future scale-up of ferronickel furnaces.

Scandium speciation in a world-class lateritic deposit

Scandium (Sc) has unique properties, highly valued for many applications. Future supply is expected to rely on unusually high-grade (up to 1000 ppm) lateritic Sc ores discovered in Eastern Australia. To understand the origin of such exceptional concentrations, we investigated Sc speciation in one of these deposits. The major factors are unusually high concentrations in the parent rock together with lateritic weathering over long time scales in a stable tectonic context. At microscopic and atomic scales, by combining X-ray absorption near edge structure spectroscopy, X-ray diffraction and microscopic and chemical analyses, we show that Sc-rich volumes are associated with iron oxides. In particular, Sc adsorbed on goethite accounts for ca 80 % of the Sc budget in our samples. The remaining is incorporated in the crystal structure of hematite, substituting for Fe3+. Scandium grades reflect the high capacity of goethite to adsorb this element. In contrast, the influence of hematite is limited by the low levels of Sc that its structure can incorporate. These crystal-chemical controls play a major role in lateritic Sc deposits developed over ultramafic–mafic rocks.

Kinetics study of carbon raiser on the reduction of nickel laterite from Pomalaa, Southeast Sulawesi

As one of the top ten on nickel laterite ore resources in the world, Indonesia must have been initiating the nickel processing in total amount of about 1.5 million tonnes. In regard to the low nickel laterite processing, one of the possible product is nickel pig iron (NPI) needed for the stainless steel industries. In this study carbon raiser that is waste from oil industries was used to replace metalurgical coke. The kinetic of nickel laterite reduction using carbon raiser was studied and compared with anthrasite coal. In this work, the author conducted the reduction of nickel laterite ores by both carbon raiser and anthrasite coal as reductant, in air and CO2 atmosphere, within the temperature ranged from 800°C and 1000°C. Two models were applied, sphere particle geometry model and Ginstling-Brounhstein diffusion model, to study the kinetic parameters. The results indicated that type of reductants and reduction atmosphere greatly influence the kinetic parameters. The obtained values of activation energy were varied between 17.44-18.12 kcal/mol.

Reductive bioprocessing of cobalt-bearing limonitic laterites

Demand for cobalt is increasing worldwide, primarily as a result of its use in rechargeable batteries, super-alloys, and the chemicals industry. Extraction and recovery of cobalt from primary ores and waste materials using (novel) bioprocessing approaches has been suggested to have significant potential as a means to secure the supply of this critical metal in future years. While bioleaching of cobalt-bearing sulfide ores has been carried out in one full-scale operation (at Kasese, Uganda), bioprocessing of cobalt-bearing oxidised ores, such as limonitic laterites, has hitherto received little attention. In the present work, reductive bioleaching of three limonitic laterite ores was carried out in anaerobic bioreactors, maintained at pH 1.8 and 35°C, and compared with oxidative acid leaching in control aerobic bioreactors. Elemental sulfur was added as electron donor for the acidophilic bacteria used in both aerobic and anaerobic bioreactors. Reductive bioleaching enhanced the extraction of cobalt from all three ores, by a factor of up to 6-fold, compared to acid leaching under aerobic conditions. Extraction of cobalt from the ores closely paralleled that of manganese, suggesting that the most of the cobalt was liberated via the reductive dissolution of manganese (IV) minerals present in the limonites, catalysed directly and/or indirectly by the bacteria present (predominantly Acidithiobacillusferrooxidans and Sulfobacillusthermosulfidooxidans).

Phase Evolution and Ni-Fe Granular Growth of Saprolitic Laterite Ore–CaO Mixtures during Reductive Roasting

The correlations between phase evolution, fusion behavior, and Ni-Fe granules growth of laterite ore–CaO mixtures during reductive roasting have been investigated. The minimum melting point of 1220°C of the CaO-MgO-Al2O3-SiO2 system with 17–36 wt.% CaO is demonstrated via phase diagram analysis, and this point is decreased in the presence of FeO. This reveals that the fusion behavior in close association with the Fe-Ni granular growth can be regulated by altering the contents of CaO and FeO. Promoting the generation of diopside (CaMgSi2O6) may reduce the operating temperature from 1300–1350°C to 1150–1200°C, which ensures sufficient melting phase content. Moreover, reducing the CO partial fraction lowers the fusion temperature but hinders the growth of Ni-Fe grains. The average size of Ni-Fe granules in the reduced mixture with 17 wt.% CaO reaches nearly 20 μm at 1200°C for 1 h in a 100 vol.% CO atmosphere.

Oral bioaccessibility of inorganic contaminants in waste dusts generated by laterite Ni ore smelting.

The laterite Ni ore smelting operations in Niquelândia and Barro Alto (Goiás State, Brazil) have produced large amounts of fine-grained smelting wastes, which have been stockpiled on dumps and in settling ponds. We investigated granulated slag dusts (n=5) and fly ash samples (n=4) with a special focus on their leaching behaviour in deionised water and on the in vitro bioaccessibility in a simulated gastric fluid, to assess the potential exposure risk for humans. Bulk chemical analyses indicated that both wastes contained significant amounts of contaminants: up to 2.6wt% Ni, 7580mg/kg Cr, and 508mg/kg Co. In only one fly ash sample, after 24h of leaching in deionised water, the concentrations of leached Ni exceeded the limit for hazardous waste according to EU legislation, whereas the other dusts were classified as inert wastes. Bioaccessible fractions (BAF) of the major contaminants (Ni, Co, and Cr) were quite low for the slag dusts and accounted for less than 2% of total concentrations. In contrast, BAF values were significantly higher for fly ash materials, which reached 13% for Ni and 19% for Co. Daily intakes via oral exposure, calculated for an adult (70kg, dust ingestion rate of 50mg/day), exceeded neither the tolerable daily intake (TDI) nor the background exposure limits for all of the studied contaminants. Only if a higher ingestion rate is assumed (e.g. 100mg dust per day for workers in the smelter), the TDI limit for Ni recently defined by European Food Safety Authority (196µg/day) was exceeded (324µg/day) for one fly ash sample. Our data indicate that there is only a limited risk to human health related to the ingestion of dust materials generated by laterite Ni ore smelting operations if appropriate safety measures are adopted at the waste disposal sites and within the smelter facility.

Limonitic Laterite Ore as a Catalyst for the Dry Reforming of Methane

We investigated four catalysts for the dry reforming of methane: three Ni-containing natural iron ores (LN, SN, and NN ores) and one Ni-supported ore (Ni-supported NN ore) to solve the problems about unused high-temperature waste heat and CO2 emission in the steel industry. The CO2 conversion ratio was highest for the LN ore (1.18 wt % Ni), followed by Ni-supported NN (1.0 wt % Ni), SN (0.30 wt % Ni), and NN (0 wt % Ni) ores. The CO2 conversion ratio of the LN ore was much higher than that of the Ni-supported NN ore, despite the fact that they contained almost the same amount of Ni. This is because the LN ore had a higher surface area and a higher nickel dispersion. Transmission electron microscopy with energy-dispersive X-ray spectroscopy revealed that Ni existed quite finely in the LN ore but existed as a larger particle (20 nm) in the Ni-supported NN ore. Smaller Ni particles have a higher surface area, resulting in the higher catalytic performance of the LN ore. More CO2 and CH4 reacted and higher amo...

Overcoming the bacteriostatic effects of heavy metals on Acidithiobacillus thiooxidans for direct bioleaching of saprolitic Ni laterite ores

In this study, the adaptation of Acidithiobacillus thiooxidans to heavy metals leached from saprolitic Ni laterite ores from Riverina, Australia, was performed by gradual acclimatisation. The microorganism was cultivated in heavy metals (Ni, Co, Fe, Mg, Cr and Mn) with total concentrations of 2400 to 24,000ppm equivalent to total dissolution of 1 to 10% (w/v) pulp densities of the saprolitic Ni laterite ore. Adaptation evolution mapped from its tolerance index was found to be dependent on metal concentration, acid generation, and period of adaptation. Bio-stimulation of cell growth and acid production was promoted by heavy metal stress on the bacteria. Pre-established heavy metal tolerance of the bacterial strain improved the leaching rate in its early phase; 20% and 7% increase in Ni and Co metal recoveries were observed in using adapted bacteria. However heavy metal tolerance was also achieved by the bacterium during the leaching process, albeit delayed by a lag phase. These results confirm the robust nature and suitability of A. thiooxidans in direct bioleaching of Ni ores.

Reagent Degradation in the Synergistic Solvent Extraction System LIX®63/Versatic™10/Nonyl-4PC

ABSTRACTDirect solvent extraction of nickel and cobalt from nitrate-based leach liquors has become of interest due to the successful piloting of nitric acid processes for treating nickel laterite ores. The current study investigated the stability of both hydroxyoxime and nonyl-4PC (nonyl-4-pyridine carboxylate) in LIX 63/Versatic 10/nonyl-4PC under conditions relevant to the recovery of nickel and cobalt from a nitrate-based leach liquor with stripping into sulfuric acid. Nonyl-4PC increased both the rate of hydroxyoxime degradation under the pH 1.5 extract conditions required for a potential nickel–cobalt separation process and the rate of cobalt poisoning of LIX 63. Under strip conditions and the pH 4 extract conditions required for co-extraction of nickel and cobalt, nonyl-4PC did not otherwise affect the rate of hydroxyoxime loss. Additionally, the presence of nitrate anions did not increase the loss of either hydroxyoxime or nonyl-4PC. The combination LIX 63/Versatic 10/nonyl-4PC therefore appears prospective for the co-extraction of nickel and cobalt at pH 4 from nitrate-based leach liquors.

Efficient Utilization of Nickel Laterite to Produce Master Alloy

To lower the smelting temperature associated with the carbothermic reduction processing of laterite, the optimization of slag and alloy systems was investigated to enable the reduction of laterite ore in the molten state at 1723 K. The master Fe-Ni-Mo alloy was successfully produced at a lower temperature (1723 K). The liquidus of the slag decreased with the addition of oxide flux (Fe2O3 and CaO) and that of the ferronickel alloy decreased with the addition of Mo/MoO3. More effective metal–slag separation was achieved at 1723 K, which reduces the smelting temperature by 100 K compared with the current electric furnace process. A small addition of Mo/MoO3 not only decreased the melting point of ferronickel alloys but also served as a collector to aggregate the ferronickel sponges allowing them to grow larger. The FeO concentration in the slag and the nickel grade of the alloy decreased with increasing graphite reductant addition.

Mechanistic and Kinetic Analysis of Na2SO4-Modified Laterite Decomposition by Thermogravimetry Coupled with Mass Spectrometry.

Nickel laterites cannot be effectively used in physical methods because of their poor crystallinity and fine grain size. Na2SO4 is the most efficient additive for grade enrichment and Ni recovery. However, how Na2SO4 affects the selective reduction of laterite ores has not been clearly investigated. This study investigated the decomposition of laterite with and without the addition of Na2SO4 in an argon atmosphere using thermogravimetry coupled with mass spectrometry (TG-MS). Approximately 25 mg of samples with 20 wt% Na2SO4 was pyrolyzed under a 100 ml/min Ar flow at a heating rate of 10°C/min from room temperature to 1300°C. The kinetic study was based on derivative thermogravimetric (DTG) curves. The evolution of the pyrolysis gas composition was detected by mass spectrometry, and the decomposition products were analyzed by X-ray diffraction (XRD). The decomposition behavior of laterite with the addition of Na2SO4 was similar to that of pure laterite below 800°C during the first three stages. However, in the fourth stage, the dolomite decomposed at 897°C, which is approximately 200°C lower than the decomposition of pure laterite. In the last stage, the laterite decomposed and emitted SO2 in the presence of Na2SO4 with an activation energy of 91.37 kJ/mol. The decomposition of laterite with and without the addition of Na2SO4 can be described by one first-order reaction. Moreover, the use of Na2SO4 as the modification agent can reduce the activation energy of laterite decomposition; thus, the reaction rate can be accelerated, and the reaction temperature can be markedly reduced.

Separation of nickel and iron from lateritic ore using a digestion – roasting – leaching – precipitation process

Separation of nickel and iron from lateritic ore using a digestion – roasting – leaching – precipitation process

Separation of aluminium and preparation of powdered DRI from lateritic iron ore based on direct reduction process

Lateritic iron ore has not been used effectively due to excess content of multiple metals. In this work, separation of aluminium from a high-aluminium lateritic iron ore was achieved by the process of ‘direct reduction with sodium sulfate-magnetic separation’, with a powdered direct reduced iron (DRI) produced. It is found that the presence of 12% sodium sulphate during reductive roasting significantly improves separation of iron and aluminium in magnetic separation: the total iron grade (TFe) of powdered DRI increases from 80.6 to 92.0% and the Al2O3 content decreases from 9.8 to 1.3% correspondingly. The presence of sodium sulphate results in formation of sodium aluminosilicates instead of FeAlO2. Moreover, sodium sulphate significantly promotes growth of metallic iron grains which is beneficial to sufficient liberation and separation of metallic iron grains from gangue minerals in grinding and magnetic separation.

Reductive roasting of nickel laterite ore with sodium sulphate for Fe-Ni production. Part II: Phase transformation and grain growth

ABSTRACTIn Part II, the correlation between Fe–Ni grain growth and characteristic fusion temperatures of the Na2SO4–laterite mixtures, and phase transformations of the reduced pellets were investigated. For the mechanism of sodium sulphate, Na+ is able to liberate the hosted nickel and iron within lizardite, while SO42– is the sulphur source for the formation of Fe–FeS eutectic compound which can decrease the characteristic fusion temperatures to promote the growth of ferronickel grains. The mean particle size of ferronickel increased from 7.4 μm to 48.6 μm with the addition of 20 wt% Na2SO4.

Effect of Sodium Sulfate Addition on the Production of Ferronickel from Lateritic Ore

Lateritic nickel ore from Manisa — Caldag region was roasted to form ferronickel at 1200 ◦C for 1 h with additions of metallurgical coke and sodium sulfate varying by weight 5–15% and 0–20%, respectively. Formed metallic part of roasted sample was separated from non-metallic part by magnet and examined by means of X-ray diffraction analysis and scanning electron microscopy. In spite of kamacite α-(Fe,Ni) formation, iron-rich silicate structure that causes iron losses was observed for samples roasted with only coke. Kamacite formation increased with increment of the coke percentage but iron-rich silicate structure remained almost same. With addition of sodium sulfate, elimination of iron-rich silicate phase was achieved and easily magnetizable metallic particles were obtained.