Limonitic Laterite Research Articles

Briquette Shape Roles in Carbothermal Reduction Process of Limonitic Laterite Nickel

Lateritic ore carbothermalreduction is currently the focus of many researchers. This process uses a relatively lower temperature of operation than the smelting. Therefore, the carbothermal reduction process has a relatively lower primary energy demand and CO2 gas emissions. This research examines the appropriate briquette form to obtain the optimum recovery, concentration of nickel, and selective reduction of nickel, as well as analyzes the compounds/phases formed. The briquette in this study was formed into three different geometries, i.e., the pillow, spherical, and cylindrical forms. First, this research was carried out by mixing the raw materials and forming it into specified briquette forms. Second, the formed briquettes were put into a crucible. Third, the coal-limestone bed mixture was used to cover the briquettes. Then, the carbothermic reduction process was started by heating to 700 oC for 2 hours and continued to 1400 oC for 6 hours. Finally, the magnetic separation process was performed to separate the reduced briquettes. As a result, the cylindrical shape briquette obtained better results at 6.74% Ni, with a nickel recovery of 96.20% and a selectivity factor value of 10.39. The compounds formed after carbothermic reduction process products include FeNi, Fe3Si, and SiO2. In a spherical-shaped briquette, Fe3O4 and Mg2SiO4were found in the reduced product, indicating impurities in the reduced briquettes.

Fe(III) bioreduction kinetics in anaerobic batch and continuous stirred tank reactors with acidophilic bacteria relevant for bioleaching of limonitic laterites.

In the framework of the H2020 project CROCODILE, the recovery of Co from oxidized ores by reductive bioleaching has been studied. The objective was to reduce Fe(III) to Fe(II) to enhance the dissolution of Co from New-Caledonian limonitic laterites, mainly composed of goethite and Mn oxides. This study focused on the Fe(III) bioreduction which is a relevant reaction of this process. In the first step, biomass growth was sustained by aerobic bio-oxidation of elemental sulfur. In the second step, the biomass anaerobically reduced Fe(III) to Fe(II). The last step, which is not in the scope of this study, was the reduction of limonites and the dissolution of metals. This study aimed at assessing the Fe(III) bioreduction rate at 35°C with a microbial consortium composed predominantly of Sulfobacillus (Sb.) species as the iron reducers and Acidithiobacillus (At.) caldus. It evaluated the influence of the biomass concentration on the Fe(III) bioreduction rate and yield, both in batch and continuous mode. The influence of the composition of the growth medium on the bioreduction rate was assessed in continuous mode. A mean Fe(III) bioreduction rate of 1.7 mg·L-1·h-1 was measured in batch mode, i.e., 13 times faster than the abiotic control (0.13 mg·L-1·h-1). An increase in biomass concentrations in the liquid phase from 4 × 108 cells·mL-1 to 3 × 109 cells·mL-1 resulted in an increase of the mean Fe(III) bioreduction rate from 1.7 to 10 mg·L-1·h-1. A test in continuous stirred tank reactors at 35°C resulted in further optimization of the Fe(III) bioreduction rate which reached 20 mg·L-1·h-1. A large excess of nutrients enables to obtain higher kinetics. The determination of this kinetics is essential for the design of a reductive bioleaching process.

Pre-treatment through reductive calcination for CO2 mineralization and selective battery metal extraction from laterites

The world needs an increasing supply of nickel and cobalt production as battery materials for sustainable development. However, the complexity of laterite deposits and the need to control CO2 emissions challenge the enhanced global supply from laterites. This work investigates the effects of calcination as a pre-treatment for selective battery metal extraction from both limonite laterite and saprolite laterite together with concurrent achievement of CO2 mineralization. Calcination under a reducing atmosphere of CO-N2 or CO-CO2 gas mixtures can significantly enhance the extraction of critical metals from both limonite and saprolite laterites. With calcination, the hydrated silicate minerals and ferric oxides converted to reactive olivine and ferrous oxide. The calcines thus can participate in the CO2 mineralization process to stabilize CO2 as mineral carbonates and release nickel and cobalt arising from the CO2 mineral carbonation into solution as complex ions with a ligand (such as sodium nitrilotriacetate, NTA). The optimum calcination conditions are 20 ∼ 30 % CO in CO-CO2 gas mixture at 700 °C. Beyond the optimum range results in the inadequate conversion of ferric to ferrous at too low CO concentration or over calcination of ferric to metallic iron at too high CO concentration. At the optimum conditions, the nickel & cobalt extraction and CO2 mineralization can reach 90 %, 93 %, and 39 % from laterite. Each tonne saprolite with the pre-treatment of calcination can recover 20.5 kg nickel, 0.59 kg cobalt, and simultaneously sequester 142 kg CO2 as stable mineral carbonates. The pre-treatment through slightly reductive calcination enables the robust suitability of the developed process for all layers of laterites for both critical battery metal recovery and carbon mineralization.

Transformation mechanism and selective leaching of nickel and cobalt from limonitic laterite ore using sulfation-roasting-leaching process

The sulfation-roasting-leaching process holds promise as an environmentally friendly method of production but has low recovery efficiency and poor selectivity for Ni and Co in ores containing impurity metals, including Fe, Al, and Cr. In this study, the transformation mechanism and leaching behavior of metals in a limonitic laterite ore during the sulfation-roasting-leaching process were investigated. Results suggest that the transformation of ferrous ion can reduce leaching efficiency for impurity metals in air atmosphere. The leaching efficiencies for Ni, Co, and Al were 91.1%, 91.5%, and 3.3%, respectively, during roasting at 725 °C for 1.5 h. The leaching solution equilibrium pH value was 3, the concentration of the added H2O2 was 0.5 wt%, and Fe and Cr were not detected in the leaching solution. Simulation and characterization results indicated that the conversion of Fe(II) into Fe(III) reduced the amount of FeSO4 in the roasting product and inhibited iron dissolution, demonstrating that the sulfation-roasting-leaching process is a feasible and environmentally friendly method that selectively leaches Ni and Co in ores containing trivalent metals.

A clean strengthening and carbon reducing process for limonitic laterite sintering: Pre-drying granulated green feed by sintering exhaust gas

To ensure the air permeability of granulated sintering green feed, much water needs to be added during the granulation process as the low density and loose of limonitic laterite which bears lots of crystal water as well. As the heat conduction and combustion-supporting function of moisture, excessive high fuel consumption and poor sinter strength would be inevitably generated. In this study, to synchronously ensure air permeability and moisture content to strengthen the sintering process, a novel method of pre-drying the granulated sintering green feed by the sintering exhaust gas was put forward. The results showed that comparing with the traditional sintering process, the tumble index of sinter was increased by more than 28%, and the dosage of solid fuel was reduced by more than 10%. Pre-drying granulated sintering green feed was beneficial to the matching of combustion front and heat transfer front, promoting the formation of bonding phase in sinter.

Bioleaching of a lateritic ore (Piauí, Brazil) in percolators

Heap leaching of laterites for extraction of nickel and cobalt is an attractive alternative to capital and energy intensive high pressure acid leaching, the dominant hydrometallurgical processing technology for limonitic laterites. Conventional approach for heap leaching of laterites is leaching with sulfuric acid. Consumption of sulfuric acid during heap leaching is substantial and industrial-scale operations require construction of a sulfuric acid production plant on site. In this study, heap bioleaching of laterites was simulated in laboratory scale column percolators and bioleaching of nickel and cobalt from lateritic material was successfully demonstrated for the first time. The process is based on biooxidation of the bacterially modified “wet sulfur” inside column percolators by sulfur-oxidizing acidophilic bacteria Acidithiobacillus thiooxidans. The “wet sulfur“ was generated in a bioreactor with the bacterial culture, harvested, and mixed with lateritic ore before forming agglomerates to be filled in the percolator columns. Liquid was circulated with a flow rate of 8 mL/min. Maximum metal extraction was 66% nickel, 95% cobalt, 10% iron, 55% magnesium and 89% manganese from the Piauí lateritic ore after one month bioleaching. For comparison, chemical leaching with 1 M sulfuric acid with or without addition of 10 g/L of ferrous sulfate heptahydrate as reductant resulted in extraction of approximately 80% nickel, 86% cobalt, 33% iron, 50% magnesium and 81% manganese. With bioleaching a higher cobalt but lower nickel and iron extraction was achieved, i.e. a better selectivity of nickel over iron extraction, as well as a relatively higher pH of the pregnant leach solution requiring less limestone and, consequently, lower CO2 emission and generation of iron cake waste in case of laterite bioleaching. Overall, the results are promising and show potential of laterite heap bioleaching to be further developed to application on industrial scale.

Mineralization Behavior and Strengthening Mechanism of Limonitic Laterite Ore Sintering Process Enhanced by Calcined Lime Coating

Mineralization Behavior and Strengthening Mechanism of Limonitic Laterite Ore Sintering Process Enhanced by Calcined Lime Coating

Assessing Stainless Steel Swarf Effect on Limonitic Laterite Sintering Process

Assessing Stainless Steel Swarf Effect on Limonitic Laterite Sintering Process

Investigation of the thermal behavior of Ca(NO3)2·4H2O and its application for the regeneration of HNO3 and CaO

Nitric acid pressure leaching has great potential in treating limonitic laterite. A new method is designed to improve the downstream process. The resulting calcium nitrate solution is concentrated/crystallized/pyrolyzed to achieve the regeneration of nitric acid and calcium oxide. Calcium nitrate pyrolysis is the core process to realize the new method, but the dynamic analysis of this process is relatively lacking and the pyrolysis mechanism is controversial. In this paper, TG-DSC, TG-MS and XRD were applied to systematically study the thermodynamics and phase evolution of calcium nitrate tetrahydrate. It is found that pyrolysis of calcium nitrate tetrahydrate can be divided into four stages: removing free water and part of crystal water, removing residual crystal water, stable existence of anhydrous calcium nitrate, and its decomposition after melting. Calcium nitrite and nitrogen are absent in the process of calcium nitrate pyrolysis. Three iso-conversion methods, including Flynn-Wall-Ozawa method, Kissinger-Akahira-Sunose method and Starink method, were applied to determine activation energies of calcium nitrate pyrolysis as 224.4 kJ/mol, 221.8 kJ/mol and 222.2 kJ/mol. The kinetic mechanism model of calcium nitrate pyrolysis determined by Melak method is closer to An model, which is the random nucleation and growth reaction. Calcium nitrate pyrolysis process further expands the industrial application of nitric acid pressure leaching.

Enhanced extraction of nickel from limonitic laterite via improved nitric acid pressure leaching process

At a time when the world is practicing energy conservation and emission reduction in order to achieve carbon neutrality, it is particularly important to enhance the extraction of valuable metals from low-grade resources. In the current process of extracting valuable metals from limonitic laterite, the characteristic that the laterite is a highly porous mineral is often overlooked. Inspired by our previous studies on the porous kinetics of limonitic laterite during nitric acid pressure leaching, this paper investigated the enhanced recovery of nickel from limonitic laterite. Response surface methodology was first used to optimize the nitric acid pressure leaching limonitic laterite process parameters to obtain the optimum conditions (Temperature: 194 °C, Time: 75 min, Liquid/Solid: 3.4 mL/g, and the initial nitric acid concentration: 178 g/L). Based on this process condition, two enhancement options were performed, namely bleed air treatment and adding surfactant. The results showed that both bleed air treatment and the addition of surfactant promoted the leaching of limonitic laterite. The best enhancement was achieved by DTAB (dodecyl trimethyl ammonium bromide), with a 5.22% increase in nickel extraction under optimal process conditions (from 90.63% to 95.85%). Furthermore, the analysis of the reinforcement mechanism shows that the bleed air treatment mainly removes the obstruction of the leaching reaction by the air in the pore, thus accelerating the reaction. The reinforcing effect of surfactants is mainly based on improved diffusion efficiency and increased permeability.

Nickel acquisition affected by root density of mono- and mixed-cropping peanut and choy sum

Nickel (Ni) and associated minerals (Cr and Mn) are naturally occurring substances in ultramafic laterites soil. It may be found in our vegetables and grains when agriculture is grown in ultramafic laterites. This study aimed to assess the contamination of Ni in edible crops affected by soil volume in mono- and mixed cropping on limonitic laterite soil. The investigation was conducted on Peanut (Arachis hypogaea L.) and Choy Sum (Brassica rapa var. parachinensis) in three different pots sizes-representing soil volume to support root growth, which was filled with 0.5 kg (small), 1.0 kg (medium), and 1.5 kg (big) of limonitic laterite soil, respectively. The limonitic soil has a 7.884 mg kg-1 Ni concentration. The experiment shows that Ni concentration in peanut and Choy Sum shoots of mono-cropping in small, medium, and big pots achieve 20, 90, 120 mg kg-1 and 51, 67, and 95 mg kg-1, respectively. Meanwhile, in mixed cropping, Ni concentration in small, medium, and big pots of peanut and Choy Sum shoots are lower only by 33, 50, and 51 mg kg-1 and 15, 52, and 63 mg kg-1, respectively. Contamination of Ni in Peanut and Choy Sum shoots increases with the increasing soil volume, and mixed cropping is a potential strategy to reduce the acquisition of Ni.

Atmospheric acid leaching of powdery Ni-Co-Fe alloy derived from reductive roasting of limonitic laterite ore and recovery of battery grade iron phosphate

The efficient and inexpensive extraction of Ni and Co from limonitic laterite ore is becoming imperative due to the rapidly growing demand for nickel and cobalt driven by electric vehicles (EVs). In this work, powdery Ni-Co-Fe alloy was prepared from limonitic laterite via reductive roasting followed by magnetic separation, with nickel and cobalt recoveries of 91.9% and 93.3%, respectively. Most of the gangue material was rejected, and the obtained powdery alloy was readily dissolvable in sulfuric acid solution at atmospheric pressure. Under the conditions of 2.5 M H2SO4, 80 °C, 60 min, L/S ratio of 8 mL/g, the extractions of Ni, Co and Fe were 98.5%, 99.9% and 95.6%, respectively, and chemical reaction was the rate-controlling step. The proposed process is promising for the utilization of limonitic laterite ore with high leaching efficiency and less leach residue discharge.

Surfactant-enhanced extraction of valuable metals from limonitic laterite: Porous kinetics and mechanism analysis

The efficient extraction of valuable metals from low-grade mineral resources is an important initiative to implement the concept of carbon neutrality and achieve energy conservation and emission reduction. Atmospheric leaching of laterite ores is widely noted for its low cost. However, low extraction and difficulties in slurry filtration have severely restricted its development. Inspired by our previous studies on the porous kinetics, two options for improving the nitric acid atmospheric leaching (NAAL) of limonitic laterite are proposed. 84.85 % of Ni extraction is achieved under the optimal process conditions (Temperature: 98 °C, Time: 3.5 h, Liquid/Solid: 4.7 mL/g, and the initial nitric acid concentration: 487 g/L). After enhanced treatment, the Ni extraction is increased by 3.16 % (bleed air), 4.55 % (SDS: sodium dodecyl sulphate), and 5.67 % (DTAB: dodecyl trimethyl ammonium bromide), respectively. In addition, DTAB not only promotes the leaching of laterite ores but also improves the filtration performance of the slurry. The filtration rate was more than three times higher than in the absence of DTAB. The presence of silicic acid is responsible for the difficult filtration of the slurry and the low extraction of valuable metals. Analysis of the intensification mechanism shows that the bleed air treatment mainly eliminates the obstruction of leaching by air in the pores, thus increasing the effective reaction area. The reinforcing effect of surfactants is mainly due to the improvement of diffusion efficiency, the reduction of adsorption, and the increase in permeability. This paper provided a feasible option for the enhanced leaching of limonitic laterite, and the reinforcement mechanism was explained clearly. It not only responds to the call for energy conservation and emission reduction by achieving efficient extraction of valuable metals from low grade laterite resources, but also avoids the treatment of laterite ores by means of high temperature and pressure.

Adsorption of Pb(II) and Cd(II) hydrates via inexpensive limonitic laterite: Adsorption characteristics and mechanisms

Industrial heavy metal pollution has been a long-standing concern, and adsorption is an economical and effective measure for treating wastewater containing heavy metal ions. With its low price, large specific surface area, and high surface activity, limonitic laterite is an ideal low-cost adsorbent for the removal of heavy metal ions. In this paper, the adsorption behavior of heavy metal ions on limonitic laterite was studied, and then the mechanism of Pb2+ and Cd2+ hydrate adsorption was described in detail by combining density functional theory (DFT) calculations. The results showed that the removal ratios of Pb2+ and Cd2+ by laterite were 99.1 % and 86.17 %, respectively, which were much higher than the removal efficiencies of Pb2+ and Cd2+ by synthetic goethite. Furthermore, according to isothermal adsorption and kinetic analysis, Pb2+ and Cd2+ were chemically adsorbed on laterite as a single molecular layer. Further mechanistic analysis from DFT indicated that Pb2+ hydrate exhibits bidentate adsorption on the goethite (010) surface, while the Cd2+ hydrate displays monodentate adsorption. Partial density of states (PDOS) and differential charge density analyses indicate that the Pb6d orbital hybridizes with the O1s orbital and the Pb6s orbital with the O2p orbital, forming the Pb-O bond. The Cd5s orbital hybridizes with the O2p orbital, forming the Cd-O bond. Both Pb2+ and Cd2+ undergo stable chemical absorption on the goethite (010) surface.

Collaborative resource utilization of hazardous chromium ore processing residue (COPR) and C-bearing dust during limonitic laterite sintering process

Much chromite ore processing residue (COPR), which is defined as hazardous solid waste due to virulent Cr (Ⅵ), is produced from chromium salt industry. C-bearing dust from steel industry is a kind of typically solid waste with poor surface activity. The iron ore sintering process has the potential on large-scale harmless utilization of COPR and C-bearing dust. This study proposes a new approach of co-utilizing COPR and C-bearing dust during limonitic laterite sintering process. The negative influence of COPR and C-bearing dust on permeability was offset by the fuel attribute of extra C from C-bearing dust. The results indicate that, while 6% COPR and 8% C-bearing dust were added, the tumble index and yield of the sinters were basically equal to those of the blank samples. The toxic Cr (Ⅵ) was reduced to Cr (Ⅲ) which was concentrated in high alumina spinel phases during the sintering process. The obtained sinters were identified as nontoxic, and no secondary waste was generated throughout the clean utilization process.

Recovery of scandium and aluminum from limonitic laterite intermediate product

The discovery of Sc-rich Ni-Co laterite highlights the potential of the extraction of Sc from Ni-Co laterite. In the nitric acid pressure leaching (NAPL) process of treating limonitic laterite, Sc precipitates with Al and concentrates in Sc-bearing Al residue. Thus, this intermediate product becomes an important resource for Sc. This paper presents a combined process to recover Sc and Al from Sc-bearing Al residue, which consists of alkaline leaching, acid leaching and solvent extraction. First, by controlling alkalinity, 94.3% Al was separated from the Sc-bearing Al residue, while 96.8% Sc was enriched in leach residue. Then, the obtained Sc-rich residue was totally leached with sulfuric acid. Moreover, Sc in leach solution was synergistically extracted by 10% Di-(2-ethylhexyl) phosphoric acid (P204) and 5% Tributyl phosphate (TBP). Finally, the co-extracted impurities in the Sc-loaded organic phase were scrubbed by HCl solution, followed by the Sc was stripped with NaOH solution. Sc-bearing Al residue is an advantageous Sc resource, and the proposed process could achieve comprehensive utilization of Sc-bearing Al residue in a facile way.

A novel and greener sequential column leaching approach for the treatment of two different Greek laterites

Τhe present study investigates, from an environmental protection viewpoint, the efficiency of sequential column leaching of two different Greek laterites, i.e. a limonitic ore from central and a saprolitic ore from northern Greece. First, the most refractory limonitic laterite is leached in the first column for 15 days and the obtained pregnant leach solution (PLS) is further used for the leaching of the easier to treat saprolitic ore in the second column, thus achieving a significantly reduced acid consumption. The main parameters affecting the process efficiency, i.e. acid molarity (1.5 or 3 mol/L H2SO4) and addition of sodium sulfite (Na2SO3) in the leaching solution were studied. The extraction of Ni, Co, Fe, Al, Mg, Mn and Ca was determined by Atomic Absorption Spectroscopy (AAS), while the characterization of the ores and final residues was carried out by X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA/DTA), and Scanning Electron Microscopy/Energy Dispersive X-Ray Spectroscopy (SEM-EDS) analysis. The results confirm the efficiency of the proposed green approach, which with the use of leaching solution containing 1.5 mol/L H2SO4 and 20 g/L Na2SO3 resulted in 73.8 % Ni, 71.6 % Co and 8.4 % Fe extraction after a short period of time (33 days), while the acid consumption, which is a serious environmental concern, was very low and did not exceed 300 kg/t ore. Overall, the proposed process not only improves the efficiency of leaching of different types of laterites for the recovery of both Ni and Co but also reduces the environmental impacts due to the significantly lower acid consumption.

Crystallization and pyrolysis of nitric acid pressure leach liquor of limonitic laterite and separation of valuable metals

Based on the advantages of nitric acid pressure process (NAPL) for laterite nickel ores, this study innovatively proposes nitric acid pressure leach liquor crystallization pyrolysis-mixed metal oxides separation process. Firstly, the feasibility and the possible reactions of mixed nitrate pyrolysis were confirmed by thermodynamic analysis. Subsequently, the optimal pyrolysis temperature was experimentally investigated. Then, the pyrolysis process of combined nitrate was thermodynamically analyzed, and the phase composition of mixed metal oxides was determined by X-ray diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), and Scanning electron microscopy/energy dispersive X-ray spectrometry (SEM/EDS). The Pourbaix diagram shows that using NaOH as leaching agent can selectively separate aluminum from mixed metal oxides, and the variables influencing aluminum's leaching rate are investigated. The experimental results are as follows: the optimal pyrolysis temperature of mixed nitrate crystals is 600 °C; the pyrolysis products are mainly oxides with the formation of NiAl2O4 and MgAl2O4 spinel phases; the aluminum leaching rate is 81.9% under the optimal alkali leaching conditions. The presence of spinel phase is not favorable for aluminum leaching. After leaching, an enriched residue of 15.8% Ni, 1.9% Co and 0.19% Sc was obtained.

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.

Separation and recovery of scandium from high pressure sulfuric acid leach liquor of limonitic laterite

Extraction of Sc from Sc-rich limonitic laterite without interfering with the main nickel-cobalt production circuit will significantly enhance the economic value of laterite. A process for separation and recovery of Sc from high pressure acid leach (HPAL) liquor of limonitic laterite was proposed in this paper. Based on the chemical composition of the leach liquor, precipitation thermodynamic analysis and experiments were conducted. The results indicated that after a first step to precipitate Fe3+ at pH = 2.5 and 90 °C, Sc could be enriched through a second step precipitate at pH = 4.8 and 60 °C to 267 g/t in Sc-containing precipitate. Then, Sc was re-leached from the Sc-containing precipitate via 1 mol/L sulfuric acid at L:S ratio of 5 mL/g, 80 °C, and 40 min. Meanwhile, gypsum in the Sc-containing precipitate transformed into calcium sulfate hemihydrate during leaching. After that, Sc was synergistically extracted from the leach solution via 5% P204 and 2.5% TBP. Moreover, impurities extracted into the organic phase during the extraction of Sc were scrubbed by HCl. Finally, Sc was stripped by NaOH. By using this process, Sc could be efficiently recovered from limonitic laterite in a facile way.