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This review provides an update to the last mini-review with the same title pertaining to recent developments in bioleaching and biooxidation published in 2013 (Brierley and Brierley). In the intervening almost 10 years, microbial processes for sulfide minerals have seen increased acceptance and ongoing but also declining commercial application in copper, gold, nickel and cobalt production. These processes have been applied to heap and tank leaching, nowadays termed biomining, but increasing concerns about the social acceptance of mining has also seen the re-emergence of in situ leaching and quest for broader applicability beyond uranium and copper. Besides metal sulfide oxidation, mineral dissolution via reductive microbial activities has seen experimental application to laterite minerals. And as resources decline or costs for their exploitation rise, mine waste rock and tailings have become more attractive to consider as easily accessible resources. As an advantage, they have already been removed from the ground and in some cases contain ore grades exceeding that of those currently being mined. These factors promote concepts of circular economy and efficient use and valorization of waste materials. Key points • Bioleaching of copper sulfide ore deposits is producing less copper today • Biooxidation of refractory gold ores is producing more gold than in the past • Available data suggest bioleaching and biooxidation processes reduce carbon emissions

Recovery of new-energy critical metals including scandium, nickel and cobalt as well as copper and zinc from a neutralization residue produced in laterite hydrometallurgical process has been studied. Effect of leaching parameters such as acid consumption, solution pH and temperature has been investigated. It was found that scandium, nickel, cobalt and copper could be recovered at high efficiencies from the residues by selective leaching using sulphuric acid solutions under ambient conditions, while the co-leaching of impurities including iron, aluminium and silicon was low under the optimal conditions. The nickel, cobalt, copper and zinc in the leaching solution could be further concentrated into mixed sulphides and separated from impurities by sulphide precipitation.

With the growth of the stainless-steel industry, the focus has moved toward making specialized steels, where Ni has proved itself as a significant ingredient. With time, Ni demand has inclined toward the energy storage sector. Observing the drastic application in several areas, Ni demand has grown multi-fold in recent years. Ni requirement was conventionally being fulfilled by the high-grade sulfidic ores, which have been facing scarcity issues for quite a long time. These issues may get suitably addressed with the introduction of lateritic ores. Lateritic ore contributes to 70% of total nickel resources. However, due to its low grades, and comparatively higher impurity constituents, it requires specific preprocessing steps prior to utilization. The present article reviews the insight into the available hydrometallurgical approaches for treating laterite ores and the separation of nickel and cobalt from hydrometallurgy routes. Caron process, a combination of pyrometallurgy and hydrometallurgy, is also well described in the review. Mineralogy aspects and the spatial distribution of laterites ore play an essential role in selecting the best-suited hydrometallurgical route, which is also discussed. The work has introduced a novel attempt where the ore genesis, corresponding hydrometallurgical processing, and the relatable post-leaching treatment are collated for better understanding.

This study presents a facile, cost-effective hydrothermal transformation of natural lateritic iron ore into hematite nanorods, offering significant economic and technical benefits for the remediation of toxic arsenic ions. Lateritic iron ore was subjected to alkaline modification for different durations (12 h (HM12), 24 h (HM24), 36 h (HM36), and 48 h (HM48)), leading to morphological evolution into nanorod structures (2D) with variations in surface area, crystallinity, and adsorption efficacy for arsenate (As(V)) ions. Comprehensive characterization confirmed significant structural and physicochemical modifications. X-ray diffraction (XRD) analysis revealed a shift in peak positions and intensity reduction, indicative of lattice strain and increased surface defects. Fourier-transform infrared spectroscopy (FT-IR) confirmed modifications in the Fe–O coordination, and Brunauer–Emmett–Teller (BET) surface area analysis demonstrated a notable increase in surface area, with HM36 exhibiting the highest value (154.7 m 2 /g). Adsorption experiments indicated that HM36 achieved the highest As(V) removal capacity (151.4 mg/g), followed by HM48 (138.2 mg/g), HM24 (125.4 mg/g), and HM12 (113.8 mg/g). Advanced equilibrium modeling revealed steric and energetic parameters governing the adsorption mechanism, with HM36 exhibiting the highest density of active sites (Nm = 67.9 mg/g). Each active site accommodated up to three As(V) ions, emphasizing the significance of multi-ionic interactions and vertical stacking at the adsorption interface. The adsorption energy, evaluated using both classic models (< 4 kJ/mol) and advanced statistical physics models (< 9 kJ/mol), confirmed a predominantly physical and exothermic adsorption mechanism. Thermodynamic evaluations further supported the spontaneous and favorable nature of As(V) adsorption across all modified hematite derivatives. The ease of synthesis, low-cost natural precursor, improved adsorption efficiency, and recyclability highlight the potential application of these hematite nanorods in real-world wastewater remediation. The findings suggest that HM36 is a highly efficient and scalable adsorbent for arsenic removal, offering sustainable solutions for industrial and agricultural wastewater treatment.

Nickel production from saprolite—a major laterite source—is critical for the electric vehicle battery supply chain but is currently constrained by the high carbon footprint of the conventional Rotary Kiln-Electric Furnace (RKEF) process. Hydrogen-based reduction offers a sustainable alternative; however, optimizing the reaction kinetics and phase separation efficiency remains a challenge for industrial application. In this study, we investigated the hydrogen reduction behavior of saprolite ore using a dynamic reduction system to maximize Nickel Pig Iron (NPI) recovery. The effects of reduction time, temperature, gas flow rate, and particle size were systematically evaluated. The results revealed that particle size is the governing factor overcoming the diffusion resistance within the Mg-rich silicate matrix. Optimal reduction efficiency (~ 20 wt% mass loss) was achieved rapidly within 15 min at 900 °C with a particle size of -45 μm. Furthermore, a high-grade NPI (Fe ~ 73 wt%, Ni ~ 25 wt%) was successfully produced with a clear separation from the silicate slag phase. These findings demonstrate that controlling physical parameters based on mineralogical constraints is key to enhancing the reduction efficiency of hydrogen reduction, providing a viable pathway for low-carbon nickel smelting processes.

This study investigated the mechanical performance, toughness behavior, failure characteristics, and microstructure of geopolymer-stabilized laterites modified with modified natural rubber latex (MNRL) for application in pavement base and subbase layers. Class C fly ash was used as the primary binder, with MNRL added at a weight% of 0–10% of the dry soil. Unconfined compressive strength ( q u ), indirect tensile strength ( q t ), and flexural strength ( q f ) were evaluated, alongside brittleness index (BI), improvement toughness ratio (ITR), and scanning electron microscopy (SEM). The results showed that while the addition of MNRL reduced peak q u by 20–60%, most mixtures still satisfied subbase ( q u > 0.70 MPa) and base ( q u > 1.75 MPa) strength criteria. MNRL significantly decreased BI (from 1.00 to as low as 0.03) and increased ITR (up to 6.28), indicating a transition from brittle to ductile failure. SEM analysis confirmed the formation of elastic polymer films that bridge fly ash and soil particles, thereby enhancing matrix cohesion and reducing porosity. The optimal mixture containing 25–30% fly ash and 5–7% MNRL achieved q u values of 1.83–2.64 MPa with improved ductility. The findings confirmed that MNRL effectively enhanced toughness and fracture resistance, making it a promising sustainable additive for laterite stabilization in tropical pavement infrastructure.

The kinetics of hydrochloric acid leaching of oxidized magnesite–iron nickel ores from the Gornostaevskoye deposit (Eastern Kazakhstan) were investigated. The ore has high contents of Mg (14.25 wt.%), Fe (10.8 wt.%) and Si (24.32 wt.%), with a Ni content of 0.87 wt.%. The optimal process parameters were determined as follows: S:L = 1:4, temperature = 85–90 °C, leaching duration = 120 min, HCl concentration = 18%, and stirring rate = 400 rpm. The extraction rates of Ni, Mg and Fe were 91.03%, 97.88% and 93.04%, respectively. The pregnant leach solution contained 1.98 g L -1 Ni, 35.31 g L -1  Mg and 25.12 g L -1 Fe. Kinetic modeling indicated that the leaching of Ni, Fe, and Mg followed a mixed-control mechanism, with activation energies of 76.07 kJ mol -1 for Ni, 125.45 kJ mol -1 for Fe, and 119.33 kJ mol -1 for Mg, confirming that the chemical reaction was controlled. Thermodynamic analysis revealed that pimelite, nickel silicate hydrate, and antigorite are the most reactive phases under hydrochloric acid leaching, on the basis of their highly negative ΔG values. The established mineral dissolution sequence, namely, pimelite > Ni − silicate hydrate > nepouite > antigorite > lizardite > talc > wüstite > hematite, reflects the combined influence of structural accessibility and thermodynamic favorability.

The Khmer people constructed numerous monuments from the 9th to 15th centuries (Angkor period) using iron tools. Ancient ironmaking sites have been identified as slag mounds near Khmer monuments. However, details of the ironmaking technology used during the Angkor period remain unknown. Herein, we show the temporal changes in ironmaking technology in northern Cambodia, which was a major iron-producing region of the Angkorian Empire. The chemical and Nd-Sr-Pb isotopic compositions of slag and ore samples indicate that Angkorian iron producers used diverse ores and employed at least two distinct ore formulations. From the late 10th to early 13th centuries, laterite and umber were used as iron ores with the addition of Mn oxide and sulphide ores, resulting in high iron yield. This technique may have evolved in response to increased iron demand during the peak of the Angkorian Empire. However, after the late 13th century, ironmaking became less efficient, relying solely on laterite and magnetite ores without additives, which coincided with the decline of the Angkorian Empire. The efficient ironmaking method was lost with only a part of the technique possibly being transferred to another area. These results provide new insight into how technological changes in iron production were linked to the socio-economic dynamics and eventual decline of the Angkorian Empire.

Pyrite and calcium sulfite were used to remove iron and manganese from an acidic aqueous solution. The concentration of Fe was decreased to be smaller than 0.05 g/L in 60 min when pyrite and air were added into the acidic aqueous solution, but the concentration of Mn in the solution remained unchanged. After the process of iron removal, calcium sulfite and air were used to remove manganese ions from the solution, and the efficiency of manganese ion removal was larger than 75% in 240 min (with less than 0.05 g/L Fe and 0.5 g/L Mn in the solution). Meanwhile, experiments were conducted to simultaneously remove iron and manganese from artificially simulated acidic leaching solution of laterite nickel ore. When the proposed method was used to purify the leaching solution of laterite nickel ore, Fe 3+ and Mn 2+ ions were effectively removed from the acidic solution, and the recovery efficiency of nickel and cobalt was greater than 98%.

The rare earth elements (REE) have attracted much attention in recent years, being viewed as critical metals because of China’s domination of their supply chain. This is despite the fact that REE enrichments are known to exist in a wide range of settings, and have been the subject of much recent exploration. Although the REE are often referred to as a single group, in practice each individual element has a specific set of end-uses, and so demand varies between them. Future demand growth to 2026 is likely to be mainly linked to the use of NdFeB magnets, particularly in hybrid and electric vehicles and wind turbines, and in erbium-doped glass fiber for communications. Supply of lanthanum and cerium is forecast to exceed demand. There are several different types of natural (primary) REE resources, including those formed by high-temperature geological processes (carbonatites, alkaline rocks, vein and skarn deposits) and those formed by low-temperature processes (placers, laterites, bauxites and ion-adsorption clays). In this paper, we consider the balance of the individual REE in each deposit type and how that matches demand, and look at some of the issues associated with developing these deposits. This assessment and overview indicate that while each type of REE deposit has different advantages and disadvantages, light rare earth-enriched ion adsorption types appear to have the best match to future REE needs. Production of REE as by-products from, for example, bauxite or phosphate, is potentially the most rapid way to produce additional REE. There are still significant technical and economic challenges to be overcome to create substantial REE supply chains outside China.