Saprolitic Laterite Research Articles

Collaborative extraction of valuable components from saprolitic laterite ore through two-stage nitric acid leaching

Saprolitic laterite ore (SLO) is an important Ni resource that also contains high Mg and a small amount of Sc, but traditional extraction techniques cannot achieve the comprehensive utilization of valuable components, especially Mg and Sc. In this work, a new process was proposed to treat SLO through the application of an HNO3 medium. First, E-pH analysis showed that serpentine and part of iron oxide are easily destroyed, and Ni and Co embedded in silicate and Fe-bearing minerals can be also leached. Subsequently, Ni, Mg, Co, and Sc can be efficiently extracted under the HNO3 concentration of 240 g/L, 90 ℃, L/S of 5:1, 2 h, and 200 r/min. Relevant characterization confirmed that serpentine and goethite were almost completely dissolved after leaching. However, magnetite and its alteration intermediates have relatively stable properties and cannot be destroyed. To reduce acid consumption, the leach liquor was supplemented with HNO3 for two-stage leaching. Efficient extraction of valuable metals can be achieved again with the supplemented HNO3 concentration of 192 g/L. A two-stage leaching process can save 120 kg HNO3/t-ore. Finally, a technical route including two-stage HNO3 leaching, adding MgO to adjust pH, and pyrolysis of Mg(NO3)2 to regenerate HNO3 and MgO was suggested.

Selective removal of Fe(Ⅲ) from HNO3 leach liquor of saprolitic laterite ore: Precipitation efficiency, hydrolysis mechanism, and removal strategy

HNO3 leach liquor of saprolitic laterite ore contains Fe3+, Al3+, Sc3+, Ni2+, Co2+, Mg2+, etc. Efficient removal of Fe3+ while reducing the loss of valuable metals is the key to solution purification. In this paper, a detailed study was carried out on the removal of Fe3+ by hydrolysis precipitation. First, thermodynamic calculations were conducted to analyze the precipitation pH changes and possible hydrolysis products at different temperatures. Subsequently, the experimental results show that more than 99 % Fe can be removed via low-temperature hydrolysis at 25–80 ℃ and pH = 3.0–3.5, but over 40 % Al and 30 % Sc also precipitate together, causing valuable metals losses. Differently, under high-temperature conditions (180 ℃, pH = 1.0, 0.5 h), 99.49 % of Fe can be selectively removed as Fe2O3 product, while other valuable metals hardly precipitate. It was found that the low-temperature Fe removal residue exhibits irregular agglomeration and uneven particle size, and contains 9.48 % NO3– and 25.86 % Fe. The high-temperature Fe removal residue presents a nanoscale spherical shape with uniform particle size and only contains 0.087 % NO3–, and the Fe content is up to 69.07 %. Finally, the Fe3+ hydrolysis mechanism was analyzed and an efficient Fe removal process from the HNO3 system including pH adjustment of leach liquor, selective Fe removal at high temperature, flash evaporation to recover free HNO3, and solid–liquid separation to obtain Fe2O3 products was proposed.

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.

Enhancing Rotary Kiln-Electric Furnace Process of Saprolitic Laterite from the Viewpoint of Slag Optimization to Minimize Energy Consumption

Enhancing Rotary Kiln-Electric Furnace Process of Saprolitic Laterite from the Viewpoint of Slag Optimization to Minimize Energy Consumption

Near-Zero-Waste Approach for the Treatment of Saprolitic Nickel Laterite via a Combined Hydrometallurgical Process

Atmospheric acid leaching can be used for processing the nickel laterite ore. The lixivium composition necessitates Fe3+ separation as the first step in recovering valuable metals. However, traditional partial neutralization has the problem of significant loss of Ni2+ and Co2+ ions due to the high Fe3+ concentration. Besides, the discharged acidic residue leads to environmental pollution. This study proposes a combined hydrometallurgical method for efficiently recovering valuable components from saprolitic laterite. After atmospheric sulfuric acid leaching, the Fe3+ in the lixivium was first separated using phosphoric acid and sodium hydroxide as reagents; 92% of the Fe3+ precipitated as iron phosphate at a pH of 1.8. The charge and discharge capacities of the LFP sample prepared from this iron phosphate at the rate of 1 C were 157 and 154 mA h/g, respectively. During the recovery of Fe3+ ions, approximately 100% of other metals were retained in the aqueous solution. After adjustment of the pH to 6.0, this solution was used to remove impurities, including Al, Mn, Cr, and Fe. Then, more than 98% of Ni and Co were recovered as Ni,Co(OH)2 precipitates at a pH of 8.0–9.0. When the pH was raised to 11.0, over 98% of Mg precipitated as Mg(OH)2. The leach residue with a high silica content was used to prepare calcium silicate hydrate (C–S–H) via a hydrothermal process. The recovery of FePO4, Mg(OH)2, and C–S–H, in addition to Ni,Co(OH)2, made this a value-added process and with a near-zero residue discharge.

Novel heterostructured metal doped MgFe2O4@g-C3N4 nanocomposites with superior photo-Fenton preformance for antibiotics removal: One-step synthesis and synergistic mechanism

A novel metal doped MgFe2O4@g-C3N4 (m-MF@CN) nanocomposite was synthesized by one-pot method using saprolite laterite nickel ore and urea as raw materials. The heterostructure was verified as an effective heterogeneous Fenton-like catalyst for degrading antibiotics including tetracycline, oxytetracycline and chlortetracycline hydrochloride, and the related catalytic mechanism was elaborated in detail. Under the optimum conditions, the m-MF@CN/H2O2/vis system exhibited superior photo-Fenton property (degradation efficiency of 93.15% within 30 min, TOC removal efficiency was as high as 60.54% within 120 min) and cycle stability for tetracycline removal. The combination of MgFe2O4 and g-C3N4 enhanced the absorption of visible light, and the energy level matched heterojunction promoted the separation of photogenerated electron-holes to accelerate the redox cycle of ≡Fe3+/≡Fe2+. Free radical quenching and electron spin resonance (ESR) analysis confirmed that O2− was the main active species, h+ and OH also played a synergistic role in the degrading reactions. Notably, a possible degradation pathway of tetracycline was proposed according to the intermediates produced in the reaction process. The one-step synthesized m-MF@CN nanocomposite catalysts possessed high catalytic performance, good stability and recoverability, which not only realized the high-value utilization of ore raw materials, but also provided a potential practical way for efficient treatment of antibiotic wastewater.

Investigation on Saprolitic Laterite Ore Reduction Process using Palm Kernel Shell Charcoal: Kinetics and Phase Transformation

The performance and kinetic of saprolitic laterite reduction using palm kernel shell charcoal and anthracite were studied. The anthracite coal represents the conventional high-grade carbon content matter, and palm kernel shell charcoal represents

Transferring behavior and reaction kinetics of saprolitic laterite during metalized reduction in the presence of calcium fluoride

Laterite ore is the most important primary base source of nickel, however low-nickel saprolitic laterite is difficult to economically utilize. This study aims to investigate the proposed nonmolten-state metalized reduction (NSMR) technology for saprolitic laterite. First, the thermodynamics of NSMR in the presence of calcium fluoride was analyzed using laterite from Southwest China as raw material. Then, the process for concentrating nickel and iron under different factors was systematically studied. Subsequently, the behavior of nickel and iron during the NSMR process was analyzed. Lastly, the kinetics of the metalized reduction process was examined, and the reaction apparent activation energy was determined. Results showed that nickel and iron recoveries can reach as high as 92.9% and 84.6%, respectively, and these two metals are produced in the form of nickel–iron concentrate, which can be used as raw material for steel making. Calcium fluoride can inhibit nickel from entering the nickel-bearing magnesium silicate phase, avoiding the inertness of nickel and considerably increasing its metallization. The reaction process of NSMR conforms to the Avrami–Eroféev reaction model (n = 0.5) and the apparent activation energy (Ea) is 309.16 kJ mol−1. This research demonstrates the theoretical perfection of the proposed NSMR technology, which may realize the commercial utilization of worldwide low-nickel ore in a long-term stagnant state.

An efficient and low-cost magnetic heterogenous Fenton-like catalyst for degrading antibiotics in wastewater: Mechanism, pathway and stability

Metal-doped MgFe2O4 spinel ferrite synthesized from saprolite laterite nickel ore was verified as an efficient heterogeneous Fenton-like catalyst for degrading antibiotics including tetracycline (TC) and metronidazole (MNZ) in a “catalyst/oxalic acid (H2C2O4)/visible light (vis)” system. The degradation efficiencies reached over 95% and total organic carbon (TOC) removal efficiencies were nearly 50% of the two antibiotics within 210 min, under the optimal conditions, especially 90% catalytic activity of the fresh catalyst was maintained after five cycles, suggesting the ferrite possessed excellent degrading performance, cycling stability and applicability. Moreover, the degradation mechanism and pathway of TC were elucidated in detail. Results revealed that the [≡Fe(C2O4)3]3- complex ions formed by octahedral Fe3+ in spinel ferrite with oxalate ions on the surface of MgFe2O4, played the key role in production of ·OH radicals which decomposed antibiotic TC into small molecules even mineralized in three pathways. Cost-effective preparation, high catalytic performance and long cycle life may accelerate the practical application of the heterogeneous Fenton-like catalyst.

Evolution of ferronickel particles during the reduction of low-grade saprolitic laterite nickel ore by coal in the temperature range of 900–1250°C with the addition of CaO-CaF2-H3BO3

Evolution of ferronickel particles during the reduction of low-grade saprolitic laterite nickel ore by coal in the temperature range of 900–1250°C with the addition of CaO-CaF2-H3BO3

Superabsorbent recycling for process water recovery

The high process water content of many mineral tailings warrants development and application of new and cost-effective dewatering methods, involving high-capacity and regenerable water-absorbing polymers. The stimuli responsive nature of Superabsorbent (SAB) polymers enables them to release absorbed water upon changing process conditions (e.g., temperature and pH), allowing superabsorbent polymers recycling towards improving dewatering process economics. To understand the effect of process conditions and ore type coupled with cost effectiveness of superabsorbent dewatering system, this study investigates recovery of the absorbed water by pH induced superabsorbent regeneration. The superabsorbent, sodium polyacrylate, absorbed water from hydrophilic saprolitic laterite and hydrophobic chalcopyrite slurries prior to the investigations. Specifically, the effect of pH of absorbed water, SAB dosage and acid type (CH3COOH, HCl) and dosage on the SAB's water recovery behaviour was studied. The SAB dosage of 2 g/100 g slurry and HCl dosage of 2 g/100 g absorbed water were conducive for maximum water recovery (~95%) from both slurries while their pH and mineralogy had no noticeable effect on the SAB dewatering process. The overall performance, based of maximum recovered water, of CH3COOH in the SAB dewatering system was lower than HCl, however, relatively higher water recovery (~70 wt.%) was observed for Ch3COOH under slightly acidic solution conditions (~ pH 4) compared with HCl (~45 wt.% water recovery). The findings aid to the development of improved, cost-effective management of both, hydrophobic and hydrophilic waste tailings.

High-efficiency leaching of valuable metals from saprolite laterite ore using pickling waste liquor for synthesis of spinel-type ferrites MFe2O4 with excellent magnetic properties

High-efficiency leaching of valuable metals from nickeliferous laterite ore for preparation of functional materials is one of the most important high-value utilization pathways. In this paper, facile preparation of multi-metal spinel-type ferrites (MFe2O4) from saprolite laterite ore after pickling waste liquor leaching process was proposed. The effects of pickling waste liquor leaching parameters including acid concentration, leaching temperature and time, liquid–solid ratio and iron ion concentration on leaching efficiency for Fe, Ni, Mg, Mn and Co from saprolite laterite ore and the molar ratio (RFe/M) of iron ions to divalent metal ions such as Ni2+, Mn2+, Mg2+, etc. in the leach liquors were systematically investigated. After complete leaching, spinel-type ferrites were synthesized from leach liquors and the influence of RFe/M and pH value as well Zn ion doping on phase compositions, morphological structure and magnetic performance of as-synthesized samples were also characterized and analyzed. Under the optimized leaching conditions, the leaching efficiency of Ni, Co, Mn, Fe and Mg could reach 93.2%, 90.8%, 94.3%, 95.5% and 85.3%, respectively. With the concentration of iron ions in pickling waste liquors increasing from 60 to 160 g·L−1, the RFe/M value increases from 1.88 to 4.32. The pH values for synthesis of spinel-type ferrites with high purity from leach liquors with RFe/M of 1.85 and 2.04 are 8.0 and 11.0, respectively, and the saturation magnetization Ms values of as-synthesized ferrites increase gradually with the increasing of pH value. Zn ions in pickling waste liquors could be doped and fixed in spinel-type ferrites to improve Ms values of as-synthesized ferrites, and the Ms value could reach the highest as 58.6 emu·g−1 when Zn ions doping amount is 0.4. Value-added utilization of pickling waste liquor and saprolite laterite ore could be realized by the proposed process. This paper might provide theoretical and technical support for low-cost synthesis of spinel-type ferrites from polymetallic resources.

E-pH diagrams for the metal-water system at 150 °C: Thermodynamic analysis and application for extraction and separation of target metals from saprolitic laterite

Hydrometallurgical processes of laterite ores mainly occur in the aqueous solution of acid, alkali or salt. The ionization of water and change of pH are of great importance during the extraction and separation of target components. Based on the empirical equations of potential (E), pH and ionic activity terms of various species, the thermodynamics of metal-water system is summarized in the form of potential—pH (E-pH) diagrams. In the Ni + Co + Mg-H2O potential-pH diagram, the predominant area of Ni2+, Co2+ and Mg2+ is contained in the region soluble Co2+ as the pH lower than 3.8 and potential higher than −0.2 V. After superimposing the Fe-H2O potential diagram, the stable area of Ni2+, Co2+, Mg2+ and Fe2O3 is critical. The thermodynamic calculation results indicate that the extracting of Ni, Co and Mg is easy and the separation of Fe can be achieved by controlling final pH of nitric acid pressure leaching. The experiments of nitric acid pressure leaching display that more than 95% Ni and Mg and nearly 90% Co can be extracted and more than 98% Fe is separated into leach residue at initial nitric acid concentration of 120 g/L and a final pH of 0.8; leaching temperature of 150 °C; leaching time of 60 min and liquid to solid ratio of 4–8 ml/g. A new flowsheet is proposed to treat saprolitic laterite, and target components are recovered efficiently. The experimental results are in agreement with the results of the thermodynamic calculation. The process is environmentally friendly and has high economic efficiency, which can provide possibilities for commercial application of saprolitic laterite by hydrometallurgical processes.

Facile and large-scale fabrication of (Mg,Ni)(Fe,Al)2O4 heterogeneous photo-Fenton-like catalyst from saprolite laterite ore for effective removal of organic contaminants

A facile and cost effective acid leaching-coprecipitation method was developed to prepare spinel-type (Mg,Ni)(Fe,Al)2O4 from saprolite laterite ore in large scale. The as-prepared (Mg,Ni)(Fe,Al)2O4 exhibited excellent photo-Fenton-like catalytic activity in decomposing different kinds of organic dyes and antibiotic tetracycline in the present of oxalic acid (H2C2O4). The influential factors of RhB degradation efficiency were investigated, including the (Mg,Ni)(Fe,Al)2O4 dosage, H2C2O4 concentration and the intensity of simulated sunlight. Meanwhile, the reaction mechanism of (Mg,Ni)(Fe,Al)2O4/H2C2O4/simulated sunlight system was also proposed. As the formation of highly photochemical [≡Fe(C2O4)3]3− complex ions on the surface of the (Mg,Ni)(Fe,Al)2O4, the obtained (Mg,Ni)(Fe,Al)2O4 showed degradation efficiency (η) over 90.0 % for common organic dyes and antibiotic tetracycline within 180 min under the optimum conditions. The η and TOC removal for RhB were still over 98.0 % and 46.0 % after five reuse cycles, respectively. The excellent catalytic performance and recyclability make the (Mg,Ni)(Fe,Al)2O4 fabricated from natural saprolite laterite ore more competitive in dealing with wastewaters contaminated by organic pollutants.

Nonmolten state metalized reduction of saprolitic laterite ores: Effective extraction and process optimization of nickel and iron

Laterite ore is an important raw nickel ore resource, and methods for extracting valuable metals from low-nickel saprolitic laterite has not been fully developed. This paper proposes a technology, called nonmolten state metalized reduction (NSMR), for extracting nickel and iron from saprolitic laterite in a tube furnace. On the basis of the mineralogical study of ores and feasibility analysis of NSMR, the direct metalization behavior of nickel and iron under different influencing factors was systematically studied. Results showed that the recoveries of nickel and iron were only 14.2% and 32.5%, respectively. For the optimization of the reaction process, the effects of additives, predehydration, and regulating mineral composition on the recovery of nickel and iron were investigated, and the results showed that the recoveries of nickel and iron after optimization increased to 94.1% and 87.4%, respectively. The behaviors of nickel and iron before and after optimization were compared and analyzed. Nickel and iron were metalized in situ before optimization but did not migrate or polymerize remarkably. After optimization, most of the nickel–iron solid solution was polymerized and showed a ribbon shape, which is beneficial for magnetic separation. This result confirmed that the optimized process can effectively improve the metalization of nickel and iron. The lower rate of iron recovery as compared with that of nickel recovery was attributed to the different existing states of the two elements in the ore. The newly generated fayalite was the primary reason for the low iron recovery. Meanwhile, a small amount of sporadically embedded ferronickel in the tailings was responsible for the loss of iron and nickel. The proposed innovative technology can realize nonmolten metalized saprolitic laterite ores and effective beneficiation of nickel and iron.

Improved beneficiation of nickel and iron from a low-grade saprolite laterite by addition of limonitic laterite ore and CaCO3

As is well known, the process of direct reduction and magnetic separation is effective route to deal with low-grade saprolite laterite, but generally limited by the reduction of nickel (iron)-bearing minerals and growth of Fe-Ni alloy particles in the reduction process, causing the low recovery of nickel and iron. To improve beneficiation of nickel and iron from low-grade saprolite laterite with 1.29wt.%Ni and 16.31wt.%Fe, co-reduction with limonitic laterite ore and basicity optimization were adopted as strengthening measures in this paper with better economic efficiency than before. The enhancing mechanism was investigated via the thermodynamics analysis and mineralogical study. The phase transformation and growth behaviors of metallic alloy particles during reduction process were revealed as well. The results indicated that co-reduction with limonitic laterite ore is capable of promoting phase transformation from Ni2SiO4 in saprolite laterite to NiFe2O4. CaCO3 can not only destroy the structure of magnesium silicate to release nickel(iron)-bearing phase, but also enhance the reduction of Fe2SiO4 to form efficiently iron-based eutectoid with nickel and liquid phases to accelerate the growth of Fe-Ni fine particles larger than 40μm. A superior crude alloy was obtained with 5.11wt.%Ni and 82.15wt.%Fe with corresponding recovery rates of 91.89% and 85.15% respectively.

Leaching Ni and Co from Saprolitic Laterite Ore by Employing Atmospheric Acid Leaching Solution with High Concentration of FeCl3 at Mild Conditions

Limonitic and saprolitic laterite ores are used to produce Ni by employing different kinds of processes. Acid leaching is an energy-saving process for pure Ni metal production. The high concentration of Fe in atmospheric acid leaching solution caused difficulties in metal-ions separation. In this work, saprolitic laterite ore was leached by atmospheric acid leaching solution of limonitic laterite ore at moderate temperatures. Conditions affecting the leaching of valuable metals and the conversion ratio of Fe were investigated. The results showed that optimal output was obtained after 1.5 h of leaching at 150°C with 1.0 liquid/solid ratio (volume/weight). X-ray diffraction analysis and mineral liberation analysis indicate that some nickel was adsorbed by leached residues, resulting in the loss of nickel. The physiochemical properties of leached residues could be changed due to the presence of Al and Cr. The decrease in zeta potential and the increase in specific surface area resulted in the increase of Ni adsorption.

Effects and mechanism of Bayer red mud on co-reduction with a saprolitic laterite ore to prepare ferronickel

Effects and mechanism of Bayer red mud on co-reduction with a saprolitic laterite ore to prepare ferronickel

Counter-Current Leaching of Low-Grade Laterites with Hydrochloric Acid and Proposed Purification Options of Pregnant Solution

A hydrochloric acid hydrometallurgical process was evaluated for Ni and Co extraction from a low-grade saprolitic laterite. The main characteristics of the process were (i) the application of a counter-current mode of operation as the main leaching step (CCL), and (ii) the treatment of pregnant leach solution (PLS) with a series of simple precipitation steps. It was found that, during CCL, co-dissolution of Fe was maintained at very low levels, i.e., about 0.6%, which improved the effectiveness of the subsequent PLS purification step. The treatment of PLS involved an initial precipitation step for the removal of trivalent metals, Fe, Al, and Cr, using Mg(OH)2. The process steps that followed aimed at separating Ni and Co from Mn and the alkaline earths Mg and Ca, by a combination of repetitive oxidative precipitation and dissolution steps. Magnesium and calcium remained in the aqueous phase, Mn was removed as a solid residue of Mn(III)–Mn(IV) oxides, while Ni and Co were recovered as a separate aqueous stream. It was found that the overall Ni and Co recoveries were 40% and 38%, respectively. About 45% of Ni and 37% of Co remained in the leach residue, while 15% Ni and 20% Co were lost in the Mn oxides.

Facile synthesis of metal-doped magnesium ferrite from saprolite laterite as an effective heterogeneous Fenton-like catalyst

Metal-doped magnesium ferrite (MgFe2O4) with cubic spinel structure, large specific surface area and medium saturation magnetic strength was synthesized from saprolite laterite leaching solution through hydrothermal-calcination method and used as a heterogeneous Fenton-like catalyst. The influence of reaction temperature on the catalytic process was centrally discussed based on the hydroxyl radical theory. The as-prepared MgFe2O4 exhibited favorable catalytic activity for degradation of Rhodamine B (RhB), achieving 97.8% degradation efficiency of 10 mg·L−1 RhB within 300 min (90.0% degradation, 180 min) at the conditions of 45 °C, pH 6.44, 0.625 g·L−1 catalyst dosage and 1.00 vol% H2O2 concentration. And the TOC removal efficiency could reach 77.8%. After five consecutive degradation cycles, the reduction of degradation and TOC removal efficiencies were <3.0% and 8.0%, respectively, suggesting the metal-doped MgFe2O4 had high catalytic activity, good stability and excellent reusability. More importantly, the formed catalyst may broaden the application of saprolite laterite and provide a promising way for other natural minerals which contain transition metal elements in the treatment of organic dye wastewater.