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Lateritic ores constitute the main source of raw material for extraction of Ni and Co by the Caron process. Consumption of oil in the reduction furnace is one of the key indicators if the metallurgical process is economical. To date it has not been possible to replace the additive fuel oil that is used at commercial scales, therefore, the aim of this study was to partially replace the oil with bituminous coal on a pilot scale by using a mixture of 2 % coal and 1.25 % oil as the reducer additive. Phases of the reduced/leached ores were analyzed by powder X-ray diffraction, while the metallic state of the ore was determined by leaching the reacted samples with a bromine-ethanol solution followed by the atomic absorption spectrometry analysis. Extractions of Ni and Co were confirmed by leaching the reduced ore with ammoniacal-ammonium carbonate solutions. It was observed that the mixture used as a reducer additive can replace the fuel oil since it allows the adequate transformation of the main mineralogical phases of the laterite ore during the reduction process and the average extraction yields of Ni and Co for ~3 and ~8 %, respectively. Although the effect of bituminous coal particle size in the process was not analyzed, the reducing mixture ensured that the Caron process was more efficient.

The average lithium content in the Earth's crust is estimated at about 0.007%. Despite this, lithium is considered abundant and widely distributed, with significant extraction from various sources. Notably, the brines in the Salar de Atacama are highlighted for their high lithium concentration ~1800 mg/L. Lithium is currently recovered from these brines through a solar evaporation process. The brine is transferred through a series of ponds, increasing the lithium concentration from 0.2% to 6% over 18 months, while decanting other minerals like potassium, magnesium, and boron. This method is the most efficient and cost-effective globally due to the Salar de Atacama's high lithium concentration of approximately 1800 ppm and the region's intense solar radiation, which facilitates evaporation at no economic cost. This manuscript describes in detail the lithium and potassium extraction processes used in the Salar de Atacama. [ABSTRACT FROM AUTHOR]

Ferromanganese crusts are mineral resources distributed in the planet's oceans. These deep-sea minerals stand out for their abundance and diversity of metals, with Mn and Co being the most abundant elements. These minerals are a good alternative to diversify the extraction of elements, which today are found at low grades on the Earth's surface. For the co-processing of ferromanganese crusts to recover Co and Mn, there are few studies. These generally worked with the use of a reducing agent, and in many cases previous roasting processes. In the present investigation, two ferromanganese crusts that were collected from two seamounts in the central eastern Atlantic Ocean were characterized. Subsequently, these crusts were leached in an acid-reducing medium, adding steel waste (slag) with 99.73% Fe3O4 and 0.27% metallic iron from the steel industry as a reducing agent. Acid-reducing processes have previously been shown to yield high and rapid recoveries of Co and Mn from seabed minerals. However, there is no previous study using smelting slag as a reducing agent for the treatment of ferromanganese crusts. The best results of this research were obtained when working at 60 C, achieving joint extractions of Co and Mn of ~80% and ~40%, respectively, in 10 min. In addition, the process residues were analyzed, and the formation of contaminating elements or the precipitation of Co and Mn species was not observed. [ABSTRACT FROM AUTHOR]

Green hydrogen is poised to play a crucial role in the energy-transition process in developed countries over the coming years, particularly in those countries aiming to achieve net-zero emissions. Consequently, the for green hydrogen is expected to rise significantly. This article explores the fundamental methods of producing hydrogen, focusing on the oxidation reaction within a thermochemical solar cycle for the dissociation of steam. Solar thermochemical cycles have been extensively researched, yet they remain in the development stage as research groups strive to identify optimal materials and conditions to enhance process efficiency, especially at high temperatures. The article analyses theoretical foundations drawn from exhaustive scientific studies related to the oxidation of iron in steam, the relationship with the activation energy of the corrosive process, thermodynamic aspects, and the kinetic model of a heterogeneous reaction. Additionally, it presents various mechanisms of high-temperature oxidation, pH effects, reactors, and materials (including fluidized beds). This scientific review suggests that hydrogen production via a thermochemical cycle is more efficient than production via electrochemical processes (such as electrolysis), provided the limitations of the cycle's reduction stage can be overcome. [ABSTRACT FROM AUTHOR]

Corrosion is an inevitable and persistent issue that affects various metallic infrastructures, leading to significant economic losses and safety concerns, particularly in areas near or in contact with saline solutions such as seawater. Green corrosion inhibitors are compounds derived from natural sources that are biodegradable in various environments, offering a promising alternative to their conventional counterparts. Despite their potential, green corrosion inhibitors still face several limitations and challenges when exposed to NaCl environments. This comprehensive review delves into these limitations and associated challenges, shedding light on the progress made in addressing these issues and potential future developments as tools in corrosion management. Explicitly the following aspects are covered: (1) attributes of corrosion inhibitors, (2) general corrosion mechanism, (3) mechanism of corrosion inhibition in NaCl, (4) typical electrochemical and surface characterization techniques, (5) theoretical simulations by Density Functional Theory, and (6) corrosion testing standards and general guidelines for corrosion inhibitor selection. This review is expected to advance the knowledge of green corrosion inhibitors and promote further research and applications. [ABSTRACT FROM AUTHOR]

Modeling of flotation processes is complex due to the large number of variables involved and the lack of knowledge on the impact of operational parameters on the response(s), and given this problem, machine learning algorithms emerge as an alternative interesting when modeling dynamic processes. In this work, different artificial neural network (ANN) architectures for modeling the mineral concentrate in a rougher-cleaner-scavenger (RCS) circuit based on the main process variables are generated (variables as the recovery of the rougher, cleaner and scavenger cells, along with disaggregated variables). Analysis of the global sensitivity was performed to study the importance of the individual and joint performances of the stages of the flotation circuit, reflected by sensitivity indicators that allow to infer the impact that the stages and operational parameters produce on the dependent variables (mineral concentrate in rougher, cleaner and scavenger cells, in addition to the global concentration in the RCS circuit). It should be noted that the ANN is a useful tool for modeling dynamic systems such as flotation, while sensitivity analysis shows that the operation of the three threads turns out to be crucial for the subsequent evaluation of the circuit, while the Unbundled variables that most interact with the overall recovery are gas flow rate, bubble and particle diameters, bubble velocity, particle density, and surface tension.

Currently, there is a large amount of mineral resources not being exploited in large copper minings, a clear example are black copper minerals. These resources are generally not incorpo-rated into the extraction circuits or are not treated, either in stocks, leach pads, or debris. These exotic minerals have considerable amounts of Cu and Mn, which are commercially very attractive. They are refractory to conventional leaching processes, therefore, the use of reducing agents is necessary for treatment of these minerals in order to dissolve the present MnO2, which in turn allows Cu extraction. In this research, iron scrap Fe0 was used as a reducing agent for the dissolution of Mn from a black copper mineral in an acidic medium and compared to previous studies of the use of Fe2+ under the same conditions. In addition, the effects of a pretreatment process (agglomeration and curing) by adding NaCl are investigated in order to favor the reduction of MnO2. Finally, it was discovered that there is a higher kinetics of dissolution of Mn when working with Fe0 in short periods of time, although similar extraction efficiencies are obtained after prolonged times. The pretreatment process by adding NaCl resulted in increased Mn extraction in short periods of time (30 min). At applying high concentrations of the reducing agent, the effect of particle size on the dissolution rate of MnO2 was shown to be insignificant.

High-molecular-weight anionic polyacrylamide was used to analyze the effect of kaolin on the structure of particle aggregates formed in freshwater and seawater. Batch flocculation experiments were performed to determine the size of the flocculated aggregates over time by using focused beam reflectance measurements. Sedimentation tests were performed to analyze the settling rate of the solid–liquid interface and the turbidity of the supernatant. Subsequently, a model that relates the hindered settling rate to the aggregate size was used to determine the mass fractal dimension ( D f ). Flocculation kinetics revealed that greater amounts of kaolin generated larger aggregates because of its lamellar morphology. The maximum size was between 10 and 20 s of flocculation under all conditions. However, the presence of kaolin reduced the settling rate. The fractal dimension decreased with the increase in the kaolin content, resulting in the formation of irregular and porous aggregates. By contrast, factors such as the flocculation time, water quality, and quartz size had limited influences on the fractal dimension. Seawater produced a clearer supernatant because of its higher ionic strength and precoagulation of particles. Notably, the harmful effect of clays in seawater was reduced. [ABSTRACT FROM AUTHOR]

Analytical models are of vital importance to study the dynamics of complex systems, including the heap leaching process. In this work, a methodology to study the dynamics of copper recovery in the heap leaching by means of fit of analytical models that capture the leaching dynamics product of variations of leaching agents as a function of the feeding is proposed, establishing a first mode of operation keeping the leaching agent fixed (H2SO4) and a second operation mode, where Cl− is added to accelerate the reaction kinetics of sulfide minerals (secondary sulfides). Mineral recovery was modeled for the different modes of operation, dependent on the independent variables/control parameters time, heap height, leach flow rate, and feed granulometry. The results indicate that the recovery of ore from sulfide minerals is proportional to the addition of Cl−, reaching recovery levels of approximately 60%, very close to 65% recovery in conventional oxide leaching, using only H2SO4 as leaching agent. Additionally, high copper recoveries from sulfide ores are achieved at medium Cl− concentrations, but the increase in recovery at high Cl− concentrations is marginal. [ABSTRACT FROM AUTHOR]