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The biogeochemistry of post-mining areas is important because of their impact on the environment and the possibility of remediating such areas. Such a hostile environment is also a source of acidophilic microorganisms that can dissolve minerals that might be applied in the extractive metallurgy of low-grade oxide ores. Therefore, the study used autochthonic microorganisms isolated from water and sediment samples taken from places affected by acid mine drainage. The acidophiles were isolated under aerobic and anaerobic conditions. Genomic analysis revealed low prokaryotic diversity. The genera with a relative abundance greater than 1% were Acidithiobacillus (39.8-84.2%), Ferrimicrobium (26.4-34.4%), Acidiphilium (8.31-28.8%), and Leptospirillum (9.6-32.1%). Aerobic bacteria were adapted to reduce iron(III) under a nitrogen atmosphere and the presence of elemental sulfur as an electron donor. It was shown that increasing the amount of sulfur (1-5 g) had little effect on the process kinetics. In anaerobic bottom sediments, Sulfobacillus (45.7%) and Acidisphaera (32.7%) predominated. Microorganisms showed the fastest reduction activity when glycerol was used as an electron donor. Four weeks of anaerobic-controlled bioreduction of laterites yielded nickel and magnesium at 33.3% and 77.3%, respectively, which could have potential applications in the processing of laterites. [ABSTRACT FROM AUTHOR]

Growing energy demands in various sectors have resulted in overusing fossil fuel sources and rise in greenhouse gases in the atmosphere. This necessitates the need for reducing greenhouse gases and shifting to cleaner, renewable energy sources like H 2. Chemical looping is one such renewable method to produce clean H 2. The efficiency of this process depends on the oxygen carrier. Generally, oxygen carriers (OC) are transition metal oxides (Fe 2 O 3 or NiO) or some complex metal oxides like spinel or perovskites, but usage of these OCs are restricted due to their availability and redox performance. One solution for selecting OCs can be using industrial waste like slag or low-grade ores because of their composition, which consists of metal oxides. One such low-grade ore is Ni-laterite ore or chromite overburden, a mining waste found in the chromite mines of Sukinda (India). In this work, we have focused on utilizing this laterite ore as an OC for the chemical looping reforming of methane to produce syngas. The reactivity analysis of laterite ore with CH 4 was performed in DSC-TG and the reaction products were analyzed in gas chromatography along with microscopy and spectroscopic techniques. Results showed the formation of H 2 and CO gases along with reduced metallic phases. The total H 2 yield at 750 °C is determined to 53.67 (±1.09) ml/g of OC which is comparable or even higher than existing CeO 2 based OCs. Further, thermodynamic calculations are presented to calculate the theoretical yield for our process and compared with the experimental H 2 yield. This study effectively demonstrates the performance of laterite ore as an OC for generating clean and renewable energy through chemical looping technique. [Display omitted] • Utilization of laterite ore as an oxygen carrier and reactivity study in TGA of laterite ore in presence of methane. • Theoretical study of reaction with CH 4 and predicting the reaction products of laterite ore reaction with methane. • Comparison of hydrogen yield obtained in experiments (53.67 ± 1.09 ml/g of OC) and theoretical calculation (61.96 ml/g of OC). [ABSTRACT FROM AUTHOR]

In the present study, a complete separation of copper over nickel has been studied from an ammoniacal leach liquor of nickel laterite ore generated via the Caron process. For this purpose, a phenolic oxime (LIX 84-IC) used as the extractant molecule was mixed with tributyl phosphate (TBP) to inhibit the co-extraction of nickel with copper loading into the organic phase. The antagonistic effect of TBP was confirmed by the distribution coefficients to be Dmix << DLIX 84-IC + DTBP and negative values of ∆D. The highest separation (βCu/Ni) of >1329 was yielded using the molar ratio of organic mixture at LIX 84-IC:TBP = 0.4:0.6 at an organic-to-aqueous phase ratio of 1. The thermodynamic properties of copper extraction exhibited an endothermic nature with ΔH° value of 5.4 kJ∙mol−1, indicating the formation of inner-sphere coordination between metal ions and the organic mixture. Further, the stripping of copper from the loaded organic phase was quantitatively achieved by contacting with 1.0 mol∙L−1 H2SO4 solution at the unit phase ratio. [ABSTRACT FROM AUTHOR]

Microwave reduction behaviors of nickel and iron components in laterite ore were investigated in this study with a focus on the effect of reduction temperature based on both thermodynamic and experimental analyses. It was found that the mixture of laterite ore and coke powder had strong microwave response due to the existences of goethite and spinel. The nickel and iron components in the ore showed different temperature dependences during the reduction process from 300 ºC to 1100 ºC. For nickel, its metallization degree (η Ni) varied with temperature (T) in two different stages. It increased rapidly from 69.7% to 96.5% in the range 300–500 ºC (stage I) due to easier reduction of NiO than Fe 2 O 3 , which could be represented by the linear fitting equation, η Ni Ⅰ = 0.136 T + 25.98 , and then grew minorly to 99.3% following the linear fitting equation, η Ni Ⅱ = 0.0049 T + 94.327 , at higher temperatures (stage II, 500–1100 ºC). For iron, its metallization degree (η Fe) increased steadily with increasing temperature in a single stage, as confirmed by the linear fitting equation, η Fe = 0.1190 T − 23.57 (300 ° C ≤ T ≤ 1100 ° C) , owing to the stepwise reduction of Fe 2 O 3 , (Mg,Fe) 2 SiO 4 , and (Mg,Fe)(Cr,Al) 2 O 4. By considering the different reduction behaviors of nickel and iron components, the optimal reduction conditions were reduction temperature of 800 ºC, reduction time of 30 min, and C/O molar ratio of 1.2. Under these conditions, the values of η Ni and η Fe reached 98.9% and 81.6%, respectively, which were comparable with those obtained by conventional reduction at 1100 ºC for 60 min, i.e., 99.0% for nickel and 70.8% for iron. • The differential reduction behaviors of nickel and iron components in laterite ore were explored. • The nickel metallization degree varied with temperature in two different stages. • The iron metallization degree increased steadily with temperature in a single stage. • The microwave carbothermic reduction mechanism of nickel and iron components was clarified. [ABSTRACT FROM AUTHOR]

The sulfation-roasting-leaching process has successfully been used to extract nickel and cobalt from laterites due to its flexibility for application to ores with different chemical and mineralogical characteristics. One of the main characteristics of this process is to leave elements such as iron, aluminum, and chromium in the residues as insoluble oxides. In this work, a sample of nickel laterite ore from the northern region of Brazil was processed by the sulfation-roasting-leaching route. The samples after each step of the process were characterized by X-Ray diffraction (XRD), scanning electron microscopy (SEM), and chemical analysis by atomic absorption spectrometry. The phases quantification was carried out by the Rietveld method. Under favorable conditions, nickel and cobalt recoveries were higher than 80 (wt.%) while the iron recovery was only 5.5 (wt.%). Despite the higher nickel and cobalt extraction, it was verified after calculation of the metals distribution throughout the main mineral phases present in the solid leaching residue that hematite was responsible for 29.5 (wt.%) and 60.8 (wt.%) of nickel and cobalt losses in the solid leaching residue, respectively. The sulfation-roasting-leaching process efficiency is influenced by many variables, then, depending on the ore characteristics, furnace choice, and processing conditions. The possibility of reprocessing the hematite in the solid leaching residue to increase the recovery of valuable metals can be a key factor for the route viability.

Laterite ore is one of the important sources of nickel (Ni). However, it is difficult to liberate Ni from ore structure during reduction roasting. This paper provided an effective way for a robust recovery of Ni from laterite ore by H2 reduction using sodium thiosulfate (Na2S2O3) as a promoter. . It was found that a Ni content of 9.97% and a Ni recovery of 99.24% were achieved with 20 wt% Na2S2O3 at 1,100°C. The promoting mechanism of Na2S2O3 in laterite ore reduction by H2 was also investigated. The thermogravimetric results suggested the formation of Na2Mg2SiO7, Na2SO3, Na2SO4, and S during the pyrolysis of laterite with Na2S2O3, among which the alkali metal salts could destroy the structures of nickel-bearing silicate minerals and hence release Ni, while S could participate in the formation of the low-melting-point eutectic phase of FeS-Fe. The formation of low-melting-point phases were further verified by the morphology analysis, which could improve the aggregation of Ni-Fe particles due to the capillary forces of FeS-Fe as well as the enhanced element migration by the liquid phase of sodium silicates during reduction.

A two-stage leaching process, namely, high-pressure acid leaching-atmospheric acid leaching, was used to treat laterite ores under mild conditions. The leaching ratio of Ni was low because of adsorption and incomplete leaching. In this work, surfactants were used as additives to boost the leaching ratio of Ni. The effect of surfactant type (cationic, anionic, and nonionic surfactants) on the leaching ratio of Ni was investigated. Leaching results showed that stearyl trimethyl ammonium chloride (STAC) apparently increased the leaching ratios of valuable metals. The variation in the physicochemical properties of the lixiviant and the residue improved the leaching ratio of Ni in the presence of STAC. Kinetics analysis indicated that the leaching process was controlled by chemical reaction. [ABSTRACT FROM AUTHOR]

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Natural laterite can be regarded as a strong adsorbent due to its special structure and composition. In this study, the laterite was modified by manganese oxide (MnO2) to create a new good adsorbent for treating phosphate and fluoride in water environment. Under the optimized conditions of the adsorbent dose (pH 6, temperature 20°C, and the contact time 180 min), laterite, doped manganese, with diameter of grains from 0.1 to 0.5 mm has maximum adsorption capacity of 31.25 mg/g and 10.99 mg/g for phosphate and fluoride, respectively. The characteristics of the manganese doping laterite were confirmed using various techniques like SEM, BET, XRD, EDX. The adsorption process of the material was investigated by both kinetic models (pseudo-first and second orders) and isotherm models (Freundlich and Langmuir). This new material was tested for treatment of wastewater taken from the superphosphate fertilizer factory, with the results obtained showing high potential for application in reality.

• Coprocessing • of SSPS with laterite ore via the RKEF route is a promising way. • The pre-reduction temperature should be higher than 850 °C for sufficient desulfurization. • Laterite ore enhanced the desulfurization of SSPS by forming CaMgSi 2 O 6 and SO 2. • Components of CaO and CaF 2 from the SSPS served as fluxes for slag-forming. Stainless-steel pickling sludge (SSPS) is a hazardous solid waste, which mainly contains CaSO 4 , CaF 2 and a high level of metals such as Fe, Cr and Ni. The high-content of sulfur in the SSPS hinders its adequate treatment and deteriorates the quality of hot ferronickel when the SSPS was used as a feed to the rotary kiln-electrical furnace process (RKEF). Thus, the desulfurization behaviors of the SSPS, including thermodynamics, phase transformation and off-gas emission characteristics during pre-reduction were primarily investigated in this work. Pre-reduction temperature and carbon content were essential for the desulfurization, and the reduction temperature should be higher than 850 °C for sufficient sulfur removal. The presence of laterite ore enhanced the desulfurization of SSPS, and on the other hand, the presence of SSPS facilitated the subsequent reduction smelting. Under optimal conditions, almost all of the sulfur within SSPS could be removed by pre-reduction, and 94.72% Fe, 81.90% Ni and 46.14% Cr were recovered by reduction smelting. [ABSTRACT FROM AUTHOR]

Co-reduction of a saprolitic laterite and waste Bayer red mud was investigated to prepare ferronickel powder. The synchronous reduction and comprehensive recovery of nickel and iron in the low-grade laterite ores and iron in the red mud were realized. At the red mud dosage of 50 wt%, ferronickel powder with nickel and iron grades of 5.58 wt% and 89.91 wt% was obtained. The corresponding nickel and total iron recoveries were 93.11 wt% and 90.23 wt%, respectively. The red mud enhanced the nickel recovery of the saprolitic laterite ore evidently, attributing to the formation of low-melting anorthite, omphacite, and diopside during co-reduction. This led that NiO in the saprolitic ore was released. Meanwhile, obvious melting phenomenon of the roasting system was appeared, enhancing the growth of the ferronickel particles. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Atmospheric acid leaching has attracted great attention from scientists due to the mild leaching conditions. However, the leaching efficiency of nickel is lower than that using high pressure acid leaching. Herein, we report the use of a surfactant (e.g., stearyltrimethyl ammonium chloride, STAC) to improve the leaching efficiency of Ni. The effects of surfactant type, ore-surfactant ratio, leaching temperature, and leaching duration on the leaching ratio of Ni were investigated. The use of STAC resulted in the high efficiency for Ni leaching at 100 °C with an ore-surfactant ratio of 15 and leaching duration of 8 h. The leaching efficiencies of Ni and Co were significantly higher than that of atmospheric acid leaching. The surface tension and viscosity of the leaching solution, and the zeta potential of the leached residue were analyzed to investigate the mechanism of the leaching process. The changes of interfacial properties improved ionic diffusion and decreased metal adsorption, which further lead to the increasing of leaching efficiency. Image 10532775 • Strengthen the leaching of Ni by surfactant. • The leaching selectivity of Ni was improved compared with traditional process. • The reason for the improvement of Ni leaching was investigated. [ABSTRACT FROM AUTHOR]

Nickeliferous laterite ores from two typical central Greece deposits (Larymna and Evia), currently used in the LARCO GMMSA smelting plant to produce ferronickel, were characterized using a combination of diffraction, microscopic, and analytical techniques. X-ray diffraction patterns of various fractions, with emphasis to the clayey material (<2 μm), after glycolation and heating at 550 °C, indicated that both materials contain crystalline Fe3+ oxide (hematite) and chlorite-group phyllosilicates, whereas the Evia sample contains additional illite. Transmission electron microscopy investigations revealed that the LARCO laterite ores consist of complex nanoscale aggregates of the above-mentioned phases. Different Ni-bearing Mg-Fe-phyllosilicates (mainly chlorite-group minerals), occur in mixture with hematite. Nickel is present in all examined phases, and therefore the separation of pure Ni-phases, by physical or chemical methods, is practically unfeasible. Trace element bulk analyses showed that there no significant differences, with regarding to Ni content concentrations (ca. 0.6–0.7 wt.%), between the initial ore and the clay fraction, for both the Larymna and Evia laterites (ca. 30% and 26% wt.% enrichment respectively). However, the Larymna ore contains double quantities of Co and it is enriched in rare earths compared to Evia (ΣREE = 774 ppm and 76 ppm respectively), while Sc concentrations are comparable in both mining areas (64 ppm and 42 ppm respectively). Discrimination diagrams (e.g. Th/Sc vs. Zr/Sc and Ce/Ce* vs. Eu/Eu*) showed that LARCO laterite Ni-ores do not exclusively originate in ultrabasic -ophiolitic- rocks as previously considered. [ABSTRACT FROM AUTHOR]

Abstract The large-scale utilization problem of red mud remains a challenge. During the reduction of laterite ores to prepare ferronickel product, sodium or calcium salt usually needs to be added, but it would increase the raw material cost. Thus, the feasibility of co-reduction followed by magnetic separation of strong alkaline waste red mud and a limonitic laterite ore to prepare ferronickel was investigated. A ferronickel product containing 1.71 wt% nickel and 86.00 wt% iron was obtained, under the optimized co-reduction conditions of the red mud dosage of 20 wt%, the anthracite dosage of 16 wt%, the co-reduction duration of 70 min. The corresponding nickel and the total iron recoveries were 96.37 wt% and 97.72 wt%, respectively. Results showed that the co-reduction and comprehensive recovery of the iron ore in the red mud were achieved. [ABSTRACT FROM AUTHOR]

Abstract In the current paper, we proposed a novel, "one-step" method to simultaneously prepare MgO-Al 2 O 3 -SiO 2 glass-ceramics and Ni-Fe alloy from laterite ore with the addition of TiO 2. The "one-step" method makes full use of the thermal energy of the molten slag so that the energy consumption for the production of the glass-ceramics is much lower than that in a more conventional method. Moreover, the slag utilization rate can reach 100%. In this method, 0–4 g of TiO 2 as a nucleating agent was added into laterite ore to control the phase composition and microstructure of glass-ceramics. The effects of the addition of different amounts of TiO 2 on the crystallization behaviour, major crystalline phase, microstructure and various properties of glass-ceramics were investigated by XRD, SEM, EDS and a Vickers hardness tester. The results show that with an increase in the amount of TiO 2 added (0–3 g), the μ-cordierite gradually precipitated and became the main crystalline phase of the glass-ceramics. Meanwhile, the crystallinity, grain size and acid/alkali resistance were all enhanced with increased TiO 2 addition. The micro-hardness increased from 6.699 GPa to 9.156 GPa. However, as the amount of TiO 2 added increased up to 4 g, a large amount of sapphirine ((Mg 4 Al 4)(Al 4 Si 2)O 20) precipitated in the glass-ceramics. The major crystalline phase of the glass-ceramics begins to change from μ-cordierite to sapphirine, accompanied by a decrease of its density, acid/alkali resistance and micro-hardness. This study is helpful for extending the "one-step" method of simultaneously preparing glass-ceramics and metals to other low-grade ores and not just laterite ore. [ABSTRACT FROM AUTHOR]

One of the major contributors to global warming is the CO 2 emissions from the steel industry. In the primary steel making process, coal/coke is used for reduction purposes that lead to CO 2 emissions. Replacing coke with other reducing agents like syngas (H 2 and CO) could be a possible approach to reduce CO 2 emissions. One effective route for the generation of syngas in a sustainable way is the chemical looping method. In this work, we have investigated the utilization of laterite ore (a mining waste) as an Oxygen carrier for the chemical looping reforming of methane. Multiple redox cycles in the presence of methane and air as reducing and oxidizing agents were performed in DSC-TG to determine the performance of the oxygen carrier. The reacted samples formed in the reaction were analyzed using XRD and SEM. The product gases generated during the reaction were also analyzed using gas chromatography. The results of the reactivity analysis showed that H 2 and CO gases were continuously formed during the reforming reaction of methane. The phase analysis of reacted samples in XRD and SEM clearly showed the formation of stable chromite and reduced iron oxide phases. The oxygen carrier showed good stability, and a total hydrogen yield of 203.9 ml/g of OC after 20 cycles of redox reaction were observed. In addition, the theoretical yield of the reacted sample after the first cycle was calculated and compared with the experimental H 2 yield at different cycles. A thermodynamic-based simulation study is also reported in this work. The syngas generated from the reforming reaction is used to pre-reduce the Iron bearing ore materials in a blast furnace. The results showed a significant decrease in the CO 2 emissions and coke rate could be achieved in primary steelmaking by integrating a chemical looping process with a blast furnace. This study effectively shows the utilization of laterite ore as an oxygen carrier for generating syngas through a chemical looping reforming process to mitigate CO 2 emissions. [Display omitted] • Utilization of laterite ore as an oxygen carrier for multi cycle chemical looping reforming of methane. • Reactivity analysis of laterite ore for 20 cycles in TGA along with phase analysis. • Quantification of hydrogen yield obtained in 20 cycles (203.9 ml/g of oxygen carrier) using gas chromatography. [ABSTRACT FROM AUTHOR]

Following the growing demand for Ni and Co and the dwindling supplies of sulfide nickel ore, attention has turned toward the more efficient exploitation and utilization of laterite ore. Using ammonium chloride acid solution to leach is an effective method. Our research concerned investigations on the leaching mechanism and leaching kinetics of laterite. XRD was used to demonstrate the leaching mechanism through analysis of the pattern of the leaching residue and raw ore, showing that acid concentration affects the leaching process more significantly than other factors, and that valuable metals are mainly released from goethite and serpentine. The leaching order of these materials are as follows: Goethite > serpentine > magnetite and hematite. The leaching kinetics were analyzed and this leaching process followed a shrinking core model controlled by a combination of interfacial transfer and diffusion across the solid film. Leaching data fitted to the kinetic equation perfectly, and the apparent activation energies for the leaching of nickel, cobalt, and iron were calculated to be 4.01 kJ/mol, 3.43 kJ/mol, and 1.87 kJ/mol, respectively. The Arrhenius constants for Ni, Co, and Fe were 204.38, 16.65, and 7.12 × 10−3, respectively, with reaction orders of Ni (a 1.32, b 0.85, c 1.53), Co (a 1.74, b 1.12, c 1.22), and Fe (a 2.52, b −0.11, c 0.94).

An alternative process of pre-roasting, phosphoric acid leaching followed by solvent extraction of a limonitic laterite ore was described in this work, with emphasis on the solvent extraction of Ni and Co from the phosphoric acid leaching solution by P204 and P507. First, the pH value of the leaching solution was adjusted using ammonia to reduce the content of Al3+ and Fe3+ by precipitation, then the content of Al3+, Fe3+ and Mn2+ were further decreased by extraction using P204. At last, Ni2+ and Co2+ were separated by three-stage extraction using P507. After extraction, the extraction ratio of Co2+ was 96.61%, while that of Ni2+ was 12.32%, and the selective extraction of Ni2+ and Co2+ could be realized.

This study focused on the extraction of nickel from a low-grade lateritic ore. The characterization of representative samples was done by X-ray diffraction (XRD), X-ray fluorescence (XRF), and microscopic mineralogical studies. Nickel was uniformly distributed in iron (hydr)oxide minerals. The pre-concentration of nickel was attempted by magnetic separation, but was unsuccessful. The effect of the type of lixiviant, acid concentration, S/L ratio, time, and temperature were investigated in the atmospheric leaching process. Based on the experimental data, optimum conditions for the maximum recovery of nickel were determined under the following conditions: 5 M H2SO4, 25% (w/v), 90 °C, and two hours. Pre-calcination, for increasing nickel extraction by converting goethite to hematite, was carried out on raw ores at different times (30-180 minutes) and temperatures (180-540 °C). Recovery was found increasing from 69 to 95% under the same conditions. Kinetic studies were conducted by fitting the data with Shrinking Core (SC) models. The study determined, from the estimate of activation energy, that the rate of reaction controlled by chemical reaction. [ABSTRACT FROM AUTHOR]

Nickel is sourced from sulphide and laterite ores. While 70% of the nickel resources are contained in laterites, these ores are often complex and expensive to treat using conventional methods. Therefore, upgrading the nickel content in laterite ores ahead of any recovery processes is economically desirable. Flotation has not been successful to recover nickel from laterite ores because of the fine-grain and low grade nickel. Nickel laterite deposits are generally divided into limonite (oxide), nontronite (clay) and saprolite (silicate) zones. A systematic study was conducted on the ore samples sourced from these three categories to see the effect of different mineralogies on the flotation behaviour of laterite ores. Pre-concentration of laterite ores by flotation was found to be possible, but it is highly determined by the ore mineralogy. In this study, no or minor upgrade in the nickel content was found for the limonite and nontronite samples. However, it was possible to obtain 40% upgrade in the nickel content (at 70% recovery) for the saprolite ore sample using flotation. [ABSTRACT FROM AUTHOR]

Large scale utilization is still an urgent problem for waste red mud with a high content of alkaline metal component in the future. Laterite ores especially the saprolitic laterite ore are one refractory nickel resource, the nickel and iron of which can be effectively recovered by direct reduction and magnetic separation. Alkaline metal salts were usually added to enhance reduction of laterite ores. The feasibility of co-reduction roasting of a saprolitic laterite ore and red mud was investigated. Results show that the red mud addition promoted the reduction of the saprolitic laterite ore and the iron ores in the red mud were co-reduced and recovered. By adding 35wt% red mud, the nickel grade and recovery were 4.90wt% and 95.25wt%, and the corresponding iron grade and total recovery were 71.00wt% and 93.77wt%, respectively. The X-ray diffraction (XRD), scanning electron microscopy, and energy dispersive spectroscopy (SEM-EDS) analysis results revealed that red mud addition was helpful to increase the liquid phase and ferronickel grain growth. The chemical compositions “CaO and Na2O” in the red mud replaced FeO to react with SiO2 and MgSiO3 to form augite. [ABSTRACT FROM AUTHOR]

Natural laterite can be regarded as a strong adsorbent due to its special structure and composition. In this study, the laterite was modified by manganese oxide (MnO2) to create a new good adsorbent for treating phosphate and fluoride in water environment. Under the optimized conditions of the adsorbent dose (pH 6, temperature 20°C, and the contact time 180 min), laterite, doped manganese, with diameter of grains from 0.1 to 0.5 mm has maximum adsorption capacity of 31.25 mg/g and 10.99 mg/g for phosphate and fluoride, respectively. The characteristics of the manganese doping laterite were confirmed using various techniques like SEM, BET, XRD, EDX. The adsorption process of the material was investigated by both kinetic models (pseudo-first and second orders) and isotherm models (Freundlich and Langmuir). This new material was tested for treatment of wastewater taken from the superphosphate fertilizer factory, with the results obtained showing high potential for application in reality. [ABSTRACT FROM AUTHOR]

This study investigates the reactions of Na2SO4 and its effects on iron and nickel reduction in the roasting of a high-iron and low-nickel laterite ore through gas composition, X-ray diffraction, and scanning electron microscope analyses. Results showed that a reduction reaction of Na2SO4 to SO2 was performed with roasting up to 600°C. However, no clear influence on iron and nickel reductions appeared, because only a small amount of Na2SO4 reacted to produce SO2. Na2SO4 reacted completely at 1000°C, mainly producing troilite and nepheline, which remarkably improves selective reduction of nickel. Furthermore, the production of low-melting-point minerals, including troilite and nepheline, accelerated nickel reduction and delayed iron reduction, which is attributed to the concurrent production of magnesium magnetite, whose structure is more stable than the structure of magnetite. Reduction reactions of Na2SO4 resulted in weakening of the reduction atmosphere, and the main product of Na2SO4 changed and delayed the reduction of iron. Eventually, iron metallization was effectively controlled during laterite ore reduction roasting, leading to iron mainly being found in wustite and high iron-containing olivine. [ABSTRACT FROM AUTHOR]

The reductive leaching behaviour of manganese (Mn) and cobalt (Co) in a laterite and a pure manganese ore was investigated by varying and optimising various leaching parameters for the recovery of Mn and Co. The effect of different reducing agents (FeSO 4 , Na 2 SO 3), sulfuric acid concentration, reductant/ore mass ratio, leaching time, and reaction temperature on the dissolution of Mn and Co from the laterite and manganese ores were studied. Furthermore, the kinetics of Mn and Co leaching from laterite ore was studied. The Mn and Co recovery from both ores increased with increasing H 2 SO 4 concentration, reductant/ore mass ratio, leaching time, and reaction temperature. Based on the manganese and cobalt extraction efficiency, FeSO 4 was the best reductant among the two evaluated reductants. The optimum leaching of Mn and Co from the laterite ore occurred at a H 2 SO 4 concentration of 0.51 M, a reductant/ore mass ratio of 2.7, a leaching time of 5 h, and a reaction temperature of 363.15 K. For the manganese ore the optimum leaching of these elements at the same temperature occurred at a higher H 2 SO 4 concentration of 1.02 M, a reductant/ore mass ratio of 2.4, and a shorter leaching time of 2 h. The results from the optimization studies showed that the leaching trends of Mn and Co phases in the manganese ore are similar to those of the Mn and Co phases in the laterite ore. Moreover, Co was co-leached together with Mn suggesting a degree of correlation of cobalt to manganese mineral phases in both, the laterite, and the manganese ores. The kinetics of the reductive leaching of Mn and Co for the laterite ore could well be described by the Avrami model reflected by high correlation coefficient values of R2 > 0.95. The leaching of Mn and Co occurred rapidly at the initial leaching stage but gradually slowed down with prolonged leaching time. This was indicated by the modal parameter (n) values that were <1, at varying reaction temperatures. The experiments showed further that Mn and Co leaching in laterite ore is a diffusion-controlled reaction, which was indicated by the apparent activation energy of 11.7 kJ mol−1 and 11.1 kJ mol−1, respectively. • Manganese phases in laterite ore occur as lithiophorite-asbolane. • Mn and Co recovery are very high in the early stages of laterite and manganese ore leaching. • Cobalt seems to be nearly bound to manganese phases in laterite and manganese ores. • Reductive leaching of Ni from laterite ore is suitable under higher acid concentrations. • Reductive leaching of Mn and Co from laterite and manganese ore is a diffusion-controlled reaction. [ABSTRACT FROM AUTHOR]

A hydrometallurgical process was developed to recover Co(II) and Ni(II) from the chloride leach liquor of laterite ore. Most of Co(II) and Ni(II) together with a small amount of Al(III) were selectively extracted over other elements by Cyanex 301 from the feed solution at pH 1 which contained Co(II), Ni(II), Al(III), Ca(II), Mg(II) and Mn(II). From the loaded Cyanex 301, Co(II) and Al(III) were selectively stripped by 3 M HCl solution, and then Ni(II) was completely stripped by 10 M HCl solution. The McCabe-Thiele plots for the extraction and stripping isotherms were constructed. Batch simulation experiments for the counter-current extraction and stripping indicated that the recovery percentage of Co(II) and Ni(II) was 92.6 and 95.7%, respectively. Moreover, the purity of Ni(II) in the stripping solution was reached 99.5%. A process flowsheet for the recovery of Co(II) and Ni(II) from the laterite leach liquor was proposed. [ABSTRACT FROM AUTHOR]

Currently there is a decline in the world's nickel sulfide deposits, which are the main source of this metal. Due to the fact, that more than 70% of nickel reserves are in the form of oxide ores, more attention is nowadays paid on laterites. Leaching processes using different organic acids are widely described in the literature, but there is a lack of works linking influence of leaching process with the surface area and particle size distribution. Therefore, the main aim of this study was to examine how citric acid produced by microorganisms and citric acid added as chemical affected the specific surface and particle size distribution of mineral particles. The laterite ore was obtained from Szklary deposit, Poland. This study also compared the effect of chemical citric acid and filtrate after cultivation of Aspergillus niger on nickel extraction. It was observed that higher nickel recovery correspond to higher surface area of particles. The highest yield of nickel extraction was observed for a citric acid concentration of 1 mol/dm³ (67%). The specific surface area after leaching was 159 m²/g. An analysis of particle size distribution showed increase in the median particle size of particles after leaching with citric acid. It may suggest that dissolution of Polish laterites follows a shrinking core-shrinking particle model. [ABSTRACT FROM AUTHOR]

In 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. [ABSTRACT FROM PUBLISHER]

The selective reduction of nickel and adequate growth of ferronickel grains are imperative for efficient preparation of ferronickel from nickeliferous laterite ore via the process of direct reduction followed by magnetic separation. In Part I, reduction/sulfidation behaviors of a saprolitic laterite ore in the presence of sodium sulfate were investigated, with an emphasis on thermodynamic analysis, selective reduction/sulfidation ratios and kinetics. To separate the interactions between Ni and Fe, chemical titration analysis was adopted to determine the contents of various Ni and Fe species in the roasted pellets, and a modified equation to assay metallic iron content was proposed. [ABSTRACT FROM AUTHOR]

The purpose of this work is to establish the elements that condition and identify the intercalations of low ore grade, which are the cause of internal dilution, for further separation during mining operations. By observing and interpreting the geological and geochemical data pertaining the pits and the mining fronts, it was possible to differentiate the various elements that include the parameters and factors associated to the internal dilution according to their geological or mining nature. The geochemical parameters and factors of the geological component are the ones that best characterize the intercalations based on the drill samples. In contrast, the field control within the mining component is the one that allows identifying (and separating) better the intercalations immediately after the ore is fed to the industrial process in accordance to the selective potential of the mining technology and existing digging equipment. [ABSTRACT FROM AUTHOR]

Metal doped magnesium ferrites were directly synthesized from saprolite and limonite laterite ores by using an alkali fusion-solid state reaction method. Samples were characterized by X-ray diffraction (XRD), Fourier Transform Infrared spectrometer (FTIR), and Physical Property Measurement System (PPMS) to determine the structural and magnetic properties. The effects of the treated saprolite to limonite laterite ore mass ratio ( M TSL/TLL , 4:6, 5:5 and 6:4 g g –1 ), calcination temperature (700, 900, 1000 and 1100 °C) and SiO 2 content (2%, 3% and 5%) on the phase change and magnetic properties of as-prepared samples were investigated in detail. The results showed that single-phase cubic spinel ferrite could be obtained when the M TSL/TLL and calcination temperature were controlled at 6:4 and 1000 °C, respectively. With the calcination temperature increasing from 700 to 1100 °C, the saturation magnetization (Ms) value increased from 18.4 to 43.2 emu g –1 while the coercivity (Hc) value decreased from 165 to 60 Oe, which was mainly attributed to the improvement of crystallinity and purity of synthesized ferrites. In addition, increasing the SiO 2 content from 2% to 5%, the Ms value decreased from 45.4 to 31.5 emu g –1 because of the occurrence of spin canting. And the decrease of Hc value from 120 to 75 Oe might be ascribed to the reduction of anisotropy energy. [ABSTRACT FROM AUTHOR]

Laterite ore is one of the important sources of nickel (Ni). However, it is difficult to liberate Ni from ore structure during reduction roasting. This paper provided an effective way for a robust recovery of Ni from laterite ore by H 2 reduction using sodium thiosulfate (Na 2 S 2 O 3 ) as a promoter. . It was found that a Ni content of 9.97% and a Ni recovery of 99.24% were achieved with 20 wt% Na 2 S 2 O 3 at 1,100°C. The promoting mechanism of Na 2 S 2 O 3 in laterite ore reduction by H 2 was also investigated. The thermogravimetric results suggested the formation of Na 2 Mg 2 SiO 7 , Na 2 SO 3 , Na 2 SO 4 , and S during the pyrolysis of laterite with Na 2 S 2 O 3 , among which the alkali metal salts could destroy the structures of nickel-bearing silicate minerals and hence release Ni, while S could participate in the formation of the low-melting-point eutectic phase of FeS-Fe. The formation of low-melting-point phases were further verified by the morphology analysis, which could improve the aggregation of Ni-Fe particles due to the capillary forces of FeS-Fe as well as the enhanced element migration by the liquid phase of sodium silicates during reduction., Competing Interests: Author JL was employed by the company Taiyuan Green Coke Energy Co. Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Liu, Yang, Yang, Yu, Wang, Yan, Li and Liu.)

Following the growing demand for Ni and Co and the dwindling supplies of sulfide nickel ore, attention has turned toward the more efficient exploitation and utilization of laterite ore. Using ammonium chloride acid solution to leach is an effective method. Our research concerned investigations on the leaching mechanism and leaching kinetics of laterite. XRD was used to demonstrate the leaching mechanism through analysis of the pattern of the leaching residue and raw ore, showing that acid concentration affects the leaching process more significantly than other factors, and that valuable metals are mainly released from goethite and serpentine. The leaching order of these materials are as follows: Goethite > serpentine > magnetite and hematite. The leaching kinetics were analyzed and this leaching process followed a shrinking core model controlled by a combination of interfacial transfer and diffusion across the solid film. Leaching data fitted to the kinetic equation perfectly, and the apparent activation energies for the leaching of nickel, cobalt, and iron were calculated to be 4.01 kJ/mol, 3.43 kJ/mol, and 1.87 kJ/mol, respectively. The Arrhenius constants for Ni, Co, and Fe were 204.38, 16.65, and 7.12 × 10−3, respectively, with reaction orders of Ni (a 1.32, b 0.85, c 1.53), Co (a 1.74, b 1.12, c 1.22), and Fe (a 2.52, b −0.11, c 0.94). [ABSTRACT FROM AUTHOR]