Low-grade Nickel Laterite Ore Research Articles

Reductive behavior of nickel and iron metallization in magnesian siliceous nickel laterite ores under the action of sulfur-bearing natural gas

Abstract This study is a process for the preparation of advanced nickel–iron alloys by selective reduction of nickel-poor laterite ores using a variety of reducing agents. The first part of the experiment was the reduction of nickel laterite ore using natural gas; the reduction yielded mostly nickel metal and a small amount of iron forming fine nickel–iron particles. Fine nickel–iron particles are formed through the reduction of nickel and a small amount of iron oxides. These particles are dispersed and embedded within silicates. Additionally, H2S present in natural gas reacts with iron oxide, resulting in the formation of FeS. This, in turn, forms a low melting point eutectic with Fe, which reduces surface tension and promotes the growth and aggregation of nickel–iron particles. This study aimed to investigate the effects of various parameters such as roasting temperature, roasting time, natural gas concentration, and nickel laterite pellet on the formation and aggregation of ferronickel particles in low-grade nickel laterite ores. The results showed that the optimum reduction parameters were achieved at 900°C, 120 min, 40% natural gas concentration, and 40–60 mesh nickel laterite size, with roasting temperature being the most important factor followed by natural gas concentration, roasting time, and nickel laterite pellet. Using these parameters, the metallization rates of Ni and Fe were found to be as high as 95.3 and 8.5%, respectively.

Hydrophobic deep eutectic solvents for the direct leaching of nickel laterite ores: Selectivity and reusability investigations

The emergence of the battery society has resulted in an unprecedented strain on the supply of battery metals, such as nickel, cobalt, and manganese. Consequently, there is an urgent need to develop processing technology for low-grade nickel laterite ores, which are abundant in resources but challenging to process using conventional hydrometallurgy. In the present study, a hydrophobic deep eutectic solvent (DES) was employed for the first time to leach and recover battery metals from a nickel laterite ore. The DES, which was prepared by decanoic acid and trialkylmethylammonium chloride, was expected to regulate the coordination environment by limiting water and providing ligands for the target metals to be stabilized in the DES. As intended, this direct laterite leaching by the DES facilitated the selective leaching of battery metals with iron, while suppressing the leaching of magnesium and silicon which are primary impurities in the laterite ore. Furthermore, stripping and scrubbing of the metals from the DES enabled the selective recovery of battery metals from iron and even allowed for the repeated use of the DES for at least four cycles of the leaching. The proposed process offers a pathway to recover the critical battery metals from abundant magnesium-rich nickel laterite ores.

Chemo-physical concentration of a Low-grade nickel laterite ore

• A novel method for the beneficiation of limonitic Ni laterites . • Long-term oxalic acid leaching of a low-grade Ni laterite ore from Iran. • A dissolution-precipitation behavior for Ni in contrast to leachability of Fe. • Fast dissolution for Ni and Fe but delayed precipitation for Ni at high temperature. • Collection of nickel oxalate particles in the fine fraction of the leach residue. Extraction of nickel from laterites is a challenging task due to the lack of an efficient nickel concentration method. Current efforts on the beneficiation of nickel laterites–especially low-grade ones– are mainly focused on atmospheric leaching methods using mineral acids, organic acids, or a mixture of them. The aim of the present paper is developing a novel hydrometallurgical approach to concentrate nickel from laterites based on a long-term oxalic acid leaching followed by size separation of the leach residue. A limonitic laterite sample from Sarchahan deposit (Fars province, Iran) containing 0.8% Ni and 27.3% Fe was used for the experiment and dissolution behavior of nickel and iron during the course of long time leaching runs (52 h) was studied under the influence of temperature (60–90 °C) and oxalic acid concentration (0.75–1.25 M). The results show that nickel initially dissolves, but subsequently precipitates with the presence of oxalate ions as NiC 2 O 4 ·2H 2 O. In addition, iron steadily dissolves as ferric oxalate and maintained in solution so long as light-protected. However, it tends to precipitate as FeC 2 O 4 ·2H 2 O at higher temperatures and long retention times. The leach residue was separated into a fine and a coarse fraction via wet classification using a cut point of 44 μm. Phase and chemical analysis confirmed accumulation of nickel in the fine fraction yielding a Ni concentrate as an intermediate product. The concentrate obtained at 60 °C and 1.25 M oxalic acid concentration contained 3.2% Ni (∼10% NiC 2 O 4 ·2H 2 O) and 3.5% Fe with a corresponding concentration ratio of 4.05, enrichment ratio of 3.44 and nickel recovery of 84%. The proposed method appears to provide a promising prospect for exploiting low-grade nickel laterites, as the obtained concentrate could be a suitable feedstock for both pyro- and hydrometallurgical processing to yield a marketable Ni product.

Recycling of chromium sludge to promote aggregation and growth of metal during self-reduction of nickel laterite ore

Addition of stainless steel pickling sludge, which contains hazardous hexavalent chromium, to low-grade nickel laterite ore has the potential to eliminate the hexavalent chromium and promote the aggregation and growth of iron-nickel particles during reduction with anthracite. The effect of chromium sludge on the aggregation and growth of metal particles during a self-reduction process of nickel laterite ore has been studied. The detoxification effect of hexavalent chromium in the sludge was evaluated using the standard TRGS 613 leaching test. Results showed that with increasing chromium sludge addition, the size of metal particles increased. With the addition of 13.94% by mass chromium sludge the average metal particle size in the reduce ore increased from 0.42 µm to 1.38 µm while the recovery of Fe, Ni and Cr increased from 53.73%, 19.39% and 33.36% to 78.33%, 69.22% and 58.26%, respectively. It is proposed that a low melting point eutectic phase of FeS formed in the reduced products, significantly promoted the migration and aggregation of metal particles. Leaching tests indicated that the original chromium sludge released > 600 mg/kg Cr(VI) while the slag from the combined laterite and chromium sludge released less than the EPA limit of 2 mg/kg Cr(VI).

Leaching of limonitic nickel from Sorowako with sulfuric acid at atmospheric pressure

Indonesia has the largest nickel laterite reserves in the world that it plays an important role in fulfilling the demand for stainless steel, nickel-based alloys, and the issue of using electric cars in the future. Currently, low-grade nickel laterite ore has not been maximally processed into value-added products domestically. The extraction process that is widely applied in the industry for low-grade laterite nickel ore through the hydrometallurgical route, which is the leaching method at atmospheric pressure in a sulphuric acid solution. The characterization of nickel ore from Sorowako has been studied that included water content analysis, sieve analysis, XRF analysis, XRD analysis, and leaching in sulphuric acid solution with agitation method at various leaching times. The results showed that the nickel ore sample from Sorowako had a water content of 5.51% with a dominant size fraction of -4 +14 mesh. XRD and XRF analysis results have shown that the chemical compositions of laterite nickel from Sorowako were Limonitic type of goethite (FeOOH) and quartz (SiO2) with the content of Ni, Co, Mg, and Fe of 1.5%, 0.02%, 0.05%, and 23.82%, respectively. The highest percentages of nickel and iron extract that were obtained at the 12 hour leaching time were 90.01% and 97.11%, respectively.

Effects of direct reduction process on the microstructure and reduction characteristics of carbon-bearing nickel laterite ore pellets

A coal-based direct reduction process was used to recover the ferronickel from low-grade nickel laterite ore. The effects of basicity on the compressive strength, metallization rate, microstructure, and reduction characteristics of carbon-bearing nickel laterite ore pellets were investigated. The results show that the metallization rate of iron and the compressive strength of metallized pellets follow a parabolic function with increasing basicity. The optimal reduction temperature of the rotary kiln should be controlled at 1150 °C to 1250 °C with pellet basicity of 0.56 to prevent the ring-forming phenomenon. Under optimum process conditions, the metallized pellets mainly consist of ferronickel ([Fe,Ni]), forsterite ferroan (Mg1.38Fe0.61Ca0.01SiO4), and pigeonite ((Ca0.06Mg0.68Fe0.26)SiO3). The particle size of ferronickel can reach to 30 μm with a high nickel‑chromium concentrations. The compressive strength of metallized pellets is 5220 to 7223 N·Pellet−1, and the metallization rates of iron and nickel are 95.28% to 98.45%, 94.75 to 96.33%, respectively.

Production of Ferronickel Concentrate from Low-Grade Nickel Laterite Ore by Non-Melting Reduction Magnetic Separation Process

The production of ferronickel concentrate from low-grade nickel laterite ore containing 1.31% nickel (Ni) was studied by the non-melting reduction magnetic separation process. The sodium chloride was used as additive and coal as a reductant. The effects of roasting temperature, roasting duration, reductant dosage, additive dosage, and grinding time on the grade and recovery were investigated. The optimal reduction conditions are a roasting temperature of 1250 °C, roasting duration of 80 min, reductant dosage of 10%, additive dosage of 5%, and a grinding time of 12 min. The grades of nickel and iron are improved from 2.13% and 51.12% to 8.15% and 64.28%, and the recovery of nickel is improved from 75.40% to 97.76%. The research results show that the additive in favor of the phase changes from lizardite phase to forsterite phase. The additive promotes agglomeration and separation of nickel and iron.

Optimal conditions for selective reduction process of Nickel Laterite Ore

A low-grade nickel laterite ore from Indonesia was selected to investigate the effect of temperature and time of reduction upon the extraction of nickel through the selective reduction-magnetic separation process to produce the ferronickel. The nickel ore was mixed with5 wt.% of anthracite coal and 10 wt.% of sodium sulfate additive. The mixed ore was pelletized into 10-15 mm of diameter. A series of selective reduction processes were carried out into the pellet ores at various temperatures of 950-1150 °C for 60-120 minutes. The optimal selective reduction parameters of nickel laterite ore were observed clearly. The experimental results indicated that the reduction reactions proceed more completely at a higher temperature and longer reduction time. The optimum of nickel grade and recovery in the ferronickel concentrate was obtained at the reduction temperature of 1150 °C for 120 minutes, which was 8.45% and 72.1%, respectively. The increasing of temperatures and times of reduction process resulted in higher of troilite phase formation which suppressed the iron metallization and also increased the ferronickel particle size.

Separation and Recovery of Iron and Nickel from Low-Grade Laterite Nickel Ore Using Reduction Roasting at Rotary Kiln Followed by Magnetic Separation Technique

The low-grade nickel laterite ore used in this study was successfully upgraded through selective reduction by industrialized rotary kilns followed by magnetic separation. The results indicated that both iron metallization extent and nickel metallization extent showed obvious linear correlation. In addition, rational roasting temperature and prolonged grinding time could enhance the overall fineness level of reduced laterite nickel ore. The moderate roasting temperature at a range of 1100–1150 °C should be suitable enough to a conversion of total nickel to metallic nickel and partly inhibited the conversion of total iron. Ultimately, the obtained ferronickel alloy with a nickel content of 7.32% and an iron content of 84.15% was prepared successfully from the low-grade nickel laterite ore containing a nickel content of 1.92%. Nickel and iron recoveries were 96.72 and 89.08% respectively, which achieved the highly efficient recovery and utilization of iron and nickel from low-grade laterite nickel ore.

Kinetics of Reduction of Low-Grade Nickel Laterite Ore Using Carbon Monoxide

Reduction of a low-grade nickel laterite ore with carbon monoxide to produce Fe-Ni alloy was investigated using a thermo-gravimetric analysis (TGA) method. Non-isothermal reduction tests with a fixed heating rate of 10 °C/min from room temperature to 1200 °C were carried out to determine the different reduction stages and reaction products in each state. Combining measured mass losses with theoretically calculated values together with X-ray diffraction analysis, the products of different reduction stages were identified and a reaction path was established. Isothermal reduction tests with temperatures ranging from 500 °C to 1100 °C were performed to evaluate the temperature dependence of the reduction kinetics. Various kinetic models were fitted to the experimental data to further determine the rate-controlling step in the isothermal tests. Then, two groups of TG experiments were carried out to study the effect of CO flow rate and sample mass on the rate of reaction. The results indicated that the reduction rate increases with the increase of the reduction temperature from 500 °C to 1100 °C. More alloy products are formed and the apparent activation energies increase from 8.6 to 14.7 kJ/mol with the increase of the reduction temperature from 700 °C to 1100 °C. Accordingly, it was proposed that diffusion of CO in the gas bulk and through the pores of the laterite ore sample bed are the rate limiting steps.

Reduction of Nickel and Iron from Low-Grade Nickel Laterite Ore via a Solid-State Deoxidization Method Using Methane

This work focuses on the solid-state deoxidization of low-grade nickel laterite ore under various conditions using methane. The effects of the reduction temperature, reduction time, and methane concentration on the metallization rates of nickel and iron were investigated. The nickel metallization rate increased as the temperature increased to 600°C; it then decreased as the temperature was further increased. The iron metallization rate increased gradually as the temperature increased. The nickel metallization rate sharply increased to over 90% when the CH4 concentration was increased to 20 vol%. The reduction time, which ranged from 30–90 min, had a negligible effect on the reduction of nickel and iron. In the case of the reduced product, the nickel and iron metallization rates were 91.17% and 23.67%, respectively. The optimal conditions were determined to be a reduction temperature of 700°C, a reaction time of 60 min, and a CH4 concentration of 20 vol%. The nickel oxide was almost completely reduced to metallic nickel, and the majority of the iron was reduced to low-valence iron oxide. During the reduction process, a magnesium olivine phase (Mg2SiO4) was produced by the recrystallization of amorphous silicate in the reduction process, and hindered the reduction of nickel and iron.

Biocatalytic and chemical leaching of a low-grade nickel laterite ore

Nickel and cobalt recovery from a low-grade nickel laterite ore, supplied from Çaldağ deposit (Manisa, Turkey) were investigated by bio and chemical leaching processes. The fungus, Aspergillus niger was used for biocatalytic leaching experiments. The effects of parameters (solid ratio and sucrose concentration) on the biocatalytic leaching of the ore were initially tested in flasks to obtain the optimum conditions for the A. niger. Then chemical leaching was applied as a comparison to bioleaching, using organic acids (citric, oxalic, acetic and gluconic acids) as well as a mixture of acids. According the results, the maximum dissolution yield of nickel, cobalt and iron were detected respectively as 95.3%, 74.3% and 50.0% by biocatalytic processes which containing 25% (w/v) sucrose and 1% (w/v) solids. The increase in the solid ratio adversely influenced the biocatalytic activity of A. niger. Finally, further tests in reactors (v = 1 and 10 L) were performed using the optimum conditions from the flask tests. The difference in metals recovery between biocatalytic and chemical leaching was significantly important. Bioleaching produced higher Ni and Co extractions (34.3–75.6%) than chemical process.

Transformation and leaching kinetics of silicon from low-grade nickel laterite ore by pre-roasting and alkaline leaching process

Abstract The mineralogical phase transformation of a low-grade nickel laterite ore during pre-roasting process and the extraction of silicon during alkaline leaching process were investigated. The results indicate that the reaction activity of nickel ores is effectively improved by pre-roasting at 650 °C for 2 h, because of the transformation of lizardite into magnesium olivine and protoenstatite. When finely ground ore samples (44–61 μm) pre-roasted firstly react with sodium hydroxide solution (60 g/L) with a solid/liquid ratio of 1:5 at 140 °C for 120 min, the extraction of silicon can reach 89.89%, and the other valuable elements of magnesium, iron and nickel are accumulated in the solid residues. The leaching kinetics of nickel laterite ore can be described successfully by the diffusion through the product layer control model. The activation energy is calculated to be 11.63 kJ/mol and the kinetics equation can be expressed as 1–3(1–x)2/3+2(1–x)=13.53×10−2exp[–11.63/(RT)]t.

Iron, aluminium and chromium co-removal from atmospheric nickel laterite leach solutions

Atmospheric leaching (AL) of low-grade nickel laterite ores often produces leach liquor containing significant amounts of trivalent iron, aluminium and chromium ions. These impurities are normally removed by increasing the leach liquor pH to precipitate these metals before the recovery of nickel, cobalt and other metal values. This paper documents an investigation of the removal of iron, aluminium and chromium from both synthetic and real nickel laterite AL leach solutions using single- and multi-stage precipitation methods. Single-stage precipitation experiments performed using synthetic leach solutions containing Fe(III) + Ni(II) + Al(III), Fe(III) + Ni(II) + Cr(III), and Fe(III) + Ni(II) + Al(III) + Cr(III) showed that greater losses of nickel to solids occurred in the presence of aluminium and chromium. Increasing the pH value of the solution and the precipitation temperature favoured the removal of iron, aluminium and chromium, but at a cost of greater nickel losses. However, by carefully controlling pH and temperature using a multi-stage precipitation process, the iron, aluminium and chromium can be rejected effectively by precipitation with minimal nickel loss and desirable sludge properties. The optimum conditions for a multi-stage precipitation process were found to be pH 3.0 and 55 °C in the first stage and pH 3.0 and 85 °C in the second stage. Using this approach, as much as 95% iron and chromium together with more than 80% aluminium can be removed; the level of nickel loss to the solid can be reduced to below 1%. The sludge showed a fast settling rate of 5.05 m/h following the addition of a cationic flocculant. Similar satisfactory results were also obtained when performing this multi-stage precipitation procedure with real leach solutions.

Mineralogical characterization and design of a treatment process for Yunnan nickel laterite ore, China

The use of laterite ore as a major nickel source is gradually increasing because of the depletion of sulphide ores. However, in contrast to high-grade nickel sulphide ore, low-grade nickel laterite ore cannot be as easily upgraded by current technologies due to its complicated mineral structure and nickel distribution. This study investigated the mineralogical characteristics, occurrence state and dissemination characteristics of nickel within Yunnan nickel laterite ore in China. Nickel laterite ore had a complex internal structure and mainly consisted of limonite (10wt.%) and serpentine (87wt.%). Sulphides were not a significant part of this laterite ore and were rarely observed. Furthermore, the nickel was mainly hosted in serpentine by substitution for Mg or by adsorption. Serpentine had a mean grade of approximately 0.77wt.% Ni and represented approximately 81.49wt.% of the total laterite resource. A portion of the laterite ore had a pore structure that was formed by destruction of the original protolith during and after its formation, with a specific surface area of 70.042m2/g. The actual temperature for the reduction of metal oxides within the ore was analysed by H2-TPR (temperature-programmed reduction), which indicated that it was higher than the reduction temperature of the pure metal oxides. Finally, based on the above analyses, a non-melting reduction treatment process was proposed for efficient and reasonable utilization of Yunnan laterite ore.

ニッケル酸化鉱の加圧硫酸浸出における鉄の挙動

Owing to the continual depletion of resources, low-grade nickel laterite ores are being treated nowadays to extract Ni. High-pressure acid leaching (HPAL) is a suitable process for treating nickel laterite ores. HPAL has the advantage of having a high extraction rate and low chemical consumption associated with the neutralization of iron; the low chemical consumption is owing to the formation of hematite precipitate in the residue. By studying the behavior of iron under pressure acid leaching, it was observed that sulfur and carbon contained in the ore decreased the redox potential and lead to Fe (II) dissolution. Iron concentration in the leached solution was decreased by oxygen rich leaching.

Microbial leaching of metals from a lateritic nickel ore by pure and mixed cultures of mesophilic acidophiles

The extraction of precious metals, such as nickel (Ni) and cobalt (Co), from a low-grade nickel laterite ore − supplied from the Caldag deposits in Manisa, Turkey − has been investigated by employing pure and mixed cultures of mesophilic acidophiles (Acidithiobacillus ferrooxidans , Leptospirillum ferrooxidans and Acidithiobacillus thiooxidans ). The study examines the effects of parameters such as the pulp density, the amount of externally added elemental sulphur and ferrous iron, and pure and mixed bacterial cultures on the bioleaching of the lateritic ore. The increase in the pulp density adversely influenced the leaching activity of the pure and mixed cultures. Mixed culture (At. ferrooxidans and At. thiooxidans ) displayed a better performance than pure cultures on the extraction of nickel and cobalt from the ore. The maximum dissolution of Ni and Co after 40 days was found to be 97% and 95%, respectively, by a bioleaching process that contained 7% (w/v) elemental sulphur, 2.24 g/L of ferrous iron, 1% (w/v) solids and the mixed culture.

Bacterial bioleaching of low grade nickel limonite and saprolite ores by mixotrophic bacteria

Utilization of indigenous bacteria should be considered to establish a successful biohydrometallurgical process. In this study, mixrotrophic iron-oxidizing bacterial consortia consisting of Comamonas testosteroni, Alicyclobacillus ferrooxydans and Pantoea septic which were isolated from Indonesian mineral ores were examined to determine their abilities to recover nickel from limonite and saprolite ores in the bioleaching experiments using stirred tank reactors. The nickel bioleaching experiments inoculated with the bacterial consortia were carried out using coarse limonite ores and weathered saprolite ores with pulp density of 10% w/v. Abiotic controls were also carried out replacing the inocula by the sterile medium. The bioleaching processes were monitored by measuring Ni and Fe contents and pH of the leaching solution as well as the total bacterial enzymatic activity measured as FDA hydrolytic activity. The effect of leaching on the mineralogy of laterite ores was investigated by the scanning electron microscope equipped with energy-dispersive spectroscopy (SEM-EDS) and X-ray powder diffraction (XRD). After 28 days of incubation, the FDA hydrolytic activity was observed in both bioleaching experiments containing limonite (17.2 μg fluorescein/mL) and saprolite ores (16.9 μg fluorescein/mL). The leached Ni and Fe in the bioleaching experiments containing limonite ores (30% Ni and 5.6% Fe) was greater than that in abiotic controls (1% Ni and 0.1% Fe) with the pH range of 2.5 to 3.5. However, the bacterial consortia were less capable of bioleaching of Ni (2.5%) with the similar leached Fe (6%) from the saprolite ores. In abiotic controls, the medium pH remained relatively constant (pH 6). It was concluded that these bacterial isolated as the consortium were capable of nickel bioleaching (precious metal) more effectively than iron (gangue metal), thus being applicable to the commercial processing of the difficult-to-process low-grade nickel laterite ores in Indonesia.

A novel approach for recovery of nickel and iron from nickel laterite ore

In recent years, there has been an increasing focus on the utilization of low-grade nickel laterite ore. In this study, the technology for efficient utilization of nickel laterite ore was investigated. The results indicate that the experimental sample is a kind of strong acidic ferric oxide ore containing nickel, which tends to appear as a complex with argillaceous mineral. The results indicate that the ultrasonic field has a significant effect on the leaching rates of nickel and iron.Optimum leaching conditions were found as follows: size of mineral particles: 95% less than 0.074 mm; leaching temperature: 80 °C; concentration of sulfuric acid: 190 g/L; liquid-solid ratio: 5:1; leaching time: 2 h; stirring speed: 400 rpm. Under these conditions, the leaching rates of nickel and iron reach 98.35% and 91.28% with the ultrasonic field exertion working 4 min every 5 min. In contrast, the leaching rates of nickel and iron are 78.84% and 80.26% after 2 h without the ultrasonic field. A product with Fe grade of 63.56% could be obtained by precipitation and roasting, the total recovery of nickel and iron reaching 95.62% and 86.50%, respectively. The reasonable recovery technology of nickel laterite ore containing a high content of limonite minerals was determined by this work.

Nickel extraction from low grade laterite by agitation leaching at atmospheric pressure

This research work deals with the extraction of nickel from a low grade nickel laterite ore, taken from a deposit located in southwestern of Iran, through agitation leaching at atmospheric pressure. The assaying and mineralogical studies carried out on the nickel laterite sample, showed the 0.88% Ni, and principally consisted of oxide and silicate crystalline phases i.e. dolomite, quartz, magnetite, and goethite. Among numerous factors affecting such process, four major parameters i.e. temperature, agitator speed (r/min), leaching agents and their concentration were considered in a two-level full factorial experimental design. The agitation leach tests showed that the ore could be leached at atmospheric pressure with sulfuric acid while citric acid was almost unpromising. Analysis of variance (ANOVA) using DX7 software was employed to identify effective parameters. Sulfuric acid concentration and temperature were the most effective parameters on Ni extraction. Furthermore, the factorial models for experiment responses were developed. The results showed 83% Ni extraction after 4h leaching, under optimized conditions i.e. temperature at 95°C, acid concentration at 5N and agitator speed at 1000 r/min. This study revealed that factorial experimental design can be implemented to identify effective parameters on the agitation leaching process of nickel laterite.