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The red mud was activated by an acid leaching and reprecipitation approach to be used as NH.sub.3-SCR catalyst. The effect of acid concentration on the leaching rates of Fe, Ti, Al, Ca and Na was investigated, specifically, the interaction between Fe and Ti components in the obtained red mud-based catalysts was concerned. With the acid concentration increasing (below 3.1 mol/L), more Fe and Ti are leached out, meanwhile, Ti can be incorporated into Fe.sub.2O.sub.3 phase and the crystallite size of Fe.sub.2O.sub.3 becomes smaller, and the obtained catalyst exhibits better low-temperature activity and SO.sub.2 resistance. The HRM3.1 catalyst obtained at the acid concentration of 3.1 mol/L possesses strongest reducibility, largest amount of surface chemisorbed oxygen and medium surface acidity. The in-situ DRIFTS results show that more NO can be adsorbed and oxidized over the HRM3.1 catalyst to generate more nitrate species, even though in the presence of SO.sub.2, alleviating the suppression of SO.sub.2 on the NH.sub.3-SCR reaction, and thus the SO.sub.2 tolerance is enhanced.

Uranium, a cornerstone for nuclear energy, facilitates a clean and efficient energy conversion. In the era of global clean energy initiatives, uranium resources have emerged as a vital component for achieving sustainability and clean power. To fulfill the escalating demand for clean energy, continual advancements in uranium mining technologies are imperative. Currently, established uranium mining methods encompass open-pit mining, underground mining, and in situ leaching (ISL). Notably, in situ leaching stands out due to its environmental friendliness, efficient extraction, and cost-effectiveness. Moreover, it unlocks the potential of extracting uranium from previously challenging low-grade sandstone-hosted deposits, presenting novel opportunities for uranium mining. This comprehensive review systematically classifies and analyzes various in situ leaching techniques, exploring their core principles, suitability, technological advancements, and practical implementations. Building on this foundation, it identifies the challenges faced by in situ leaching and proposes future improvement strategies. This study offers valuable insights into the sustainable advancement of in situ leaching technologies in uranium mining, propelling scientific research and practical applications in the field.

Recently, the resource utilization of agricultural biomass wastes for the preparation of a wide range of high-value-added chemicals and functional materials, especially heterogeneous catalysts, has received extensive attention from researchers. In this work, mesoporous WO[sub.3]/ZrO[sub.2]-SiO[sub.2] catalysts are prepared by a two-step incipient-wetness impregnation method using agricultural biomass waste rice husk (RH) as both the silicon source and mesoporous template. The effects of different WO[sub.3] and ZrO[sub.2] loadings on the oxidative desulfurization (ODS) performance of samples are investigated, and the suitable WO[sub.3] and ZrO[sub.2] loadings are 11 and 30%, respectively. The relevant characterization results indicate that, compared to 11%WO[sub.3]/SiO[sub.2], the introduction of ZrO[sub.2] leads to the formation of stronger W-O-Zr bonds, which makes the tungsten species stabilized in the state of W[sup.6+]. The strong preferential interaction between Zr and W facilitates the formation of stable and highly dispersed WOx clusters on the mesoporous ZrO[sub.2]-SiO[sub.2] carrier. Furthermore, it also prevents the formation of WO[sub.3] crystallites, significantly reducing their content and thus inhibiting the loss of the WO[sub.3] component during cycling experiments. Therefore, the 11%WO[sub.3]/30%ZrO[sub.2]-SiO[sub.2] sample shows excellent catalytic activity and recycling performance (DBT conversion reaches 99.2% after 8 cycles, with a turnover frequency of 12.7 h[sup.–1]; 4,6-DMDBT conversion reaches 99.0% after 7 cycles, with a turnover frequency of 6.3 h[sup.–1]). The kinetics of the ODS reactions are further investigated. The mechanism of the ODS reaction is explored through experiments involving leaching, quenching, and the capture of the active intermediate. Finally, a possible reaction mechanism for the ODS process for the 11%WO[sub.3]/30%ZrO[sub.2]-SiO[sub.2] sample is proposed.

Ore leaching constitutes a core step for achieving efficient utilization of mineral resources, primarily encompassing acid leaching and alkaline leaching methods. Currently, acid leaching technology has reached a high level of maturity and is widely applied in industry due to its advantages of fast reaction kinetics and broad applicability to various mineral types. However, the theoretical framework underpinning alkaline leaching systems remains relatively weak. Given the distinct advantages of alkaline leaching in processing ores containing alkaline gangue minerals, this review systematically examines chemical and microbial leaching techniques for metal ores under alkaline conditions. It focuses on elucidating the mechanisms and key influencing factors associated with different alkaline matrices, oxidants, external pressures, and microbial strains. Future development prospects are also discussed. The aim is to provide a theoretical foundation and practical guidance for advancing metal ore leaching technologies towards greener and more efficient directions.

The permeability of ore is a key factor affecting the leaching effect of uranium ore, and the addition of surfactants can significantly improve the permeability of ore, thereby strengthening uranium ore leaching. This article simulates two infiltration leaching processes, atmospheric heap leaching and pressurized in-situ leaching, and explores the effect of surfactant cetyltrimethylammonium bromide on uranium leaching rate and ore permeability coefficient in both processes. The results showed that in the atmospheric heap leaching test, adding surfactants increased the ore leaching rate by 30.31% during the same 13 day test cycle, and the leaching process was mainly controlled by surface chemical reactions. In the pressurized in-situ leaching test, based on the results of a leaching cycle of 13 days, the average permeability coefficient increased by 72.89% and 64.07% after adding surfactants to the drained and water containing uranium deposits, respectively. In addition, the peak uranium concentration in the leaching solution appeared 2 days earlier, indicating that the addition of surfactants has a significant promoting effect on in-situ leaching of uranium, improving the leaching efficiency of uranium, and can improve the leaching rate of uranium within the same leaching cycle.

N-tetradecanoyl-L-homoserine lactone (C[sub.14]-HSL) is a long-chain signaling molecule belonging to acyl-homoserine lactones (AHLs), which is widely present in the quorum sensing (QS) system of Gram-negative bacteria. In this study, the effects of C[sub.14]-HSL on chalcopyrite bioleaching mediated by Acidithiobacillus ferrooxidans (A. ferrooxidans) were investigated. After cultivating A. ferrooxidans with different energy substrates and exploring the potential mechanisms of signal molecule production, chalcopyrite was selected as the energy substrate for further study. Molecular docking analysis revealed that the high binding affinity between AHL and the receptor protein AfeR in A. ferrooxidans was beneficial for the activation of transcription by the AfeR-AHL complex, promoting their biological impact. The variations in the physicochemical parameters of pH, redox potential, and copper ions revealed that after adding C[sub.14]-HSL, the leaching rate of chalcopyrite increased (1.15 times during the initial 12 days). Further analysis of the mechanism of extracellular polymers formation indicated that the presence of C[sub.14]-HSL could promote the formation of biofilms and the adhesion of bacteria, facilitating mineral leaching rate of A. ferrooxidans. This research provides a theoretical basis for regulating the biological leaching process of chalcopyrite and metal recovery using signaling molecules, which could also be used to control environmental damage caused by acid mine/rock drainage.

The urgent need for efficient CO[sub.2] capture technologies has driven research into amine-functionalized adsorbents, though existing methods face trade-offs between adsorption capacity and cycling stability. This study addresses these limitations by developing a novel hybrid modification strategy combining chemical grafting and physical impregnation on polymorphic kaolinite minerals. Through systematic acid leaching and hybrid grafting–impregnation amine functionalization, the adsorbents with hierarchically porous structures and optimized performances are synthesized. The tubular adsorbent (ATK-APTES-PEI) demonstrated exceptional performance, achieving a CO[sub.2] uptake of 1.68 mmol/g at 75 °C under a 60% CO[sub.2]/40% N[sub.2] mixed gas flow, with only 5.3% capacity loss after 10 adsorption–desorption cycles, significantly outperforming both rod-like (ARK-APTES-PEI, 1.55 mmol/g) and flake-like (AFK-APTES-PEI, 1.23 mmol/g) variants. The unique pore structure of ATK-APTES-PEI enables simultaneous high amine loading and maintained gas diffusion pathways, while the hybrid modification strategy synergistically enhances both adsorption capacity and stability by increasing active surface sites. These findings establish critical structure–property relationships for mineral-based adsorbents and demonstrate a scalable approach for industrial CO[sub.2] capture applications. The work provides a blueprint for designing cost-effective, stable adsorbents using abundant clay minerals, bridging materials science with environmental engineering for sustainable carbon management solutions.

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

Nowadays, deep eutectic solvents (DESs) are seen as environmentally friendly alternatives with the potential to replace traditional solvents used in hydrometallurgical processes. Although DESs have been successfully applied in the recovery of metals from secondary sources, there is still innovative potential regarding DESs as green leaching agents applied in the recovery of metals from primary sources like polysulfide ores. This study aimed to evaluate the characteristics of DESs as solvents for some of the main metals present in typical polymetallic concentrates, like Cu, Fe, Pb, and Zn. Thus, three DESs based on choline chloride (ChCl) were prepared: 1:2 ChCl-urea (also known as reline), 1:2 ChCl-ethylene glycol (also known as ethaline), and 1:2 ChCl-glycerol (also known as glyceline). Then, dissolution tests at 30 °C were carried out with these DESs and different metal- (Cu, Fe, Pb, and Zn) bearing compounds (sulfates, oxides, and sulfides). According to the dissolution tests, it was found that the solubility of the studied metals (expressed as g of metal per Kg of DES) was dictated by the bearing species, reaching the dissolution of the metals from sulfates with values as high as two orders of magnitude higher than the metal solubility values for metal oxides and sulfides.

The amount of secondary aluminium dross in China exceeds one million tons annually, posing environmental and disposal challenges. This study explores acid leaching as an alternative to conventional alkali methods for recovering Al from secondary aluminium dross to produce Al[sub.2]O[sub.3]. Research has focused on optimizing leaching conditions. Under optimized H[sub.2]SO[sub.4] leaching conditions, an Al[sup.3+] leaching ratio of 86.5% is achieved. By maintaining a pH below 9 during hydrolytic precipitation and multiple washes, the leaching efficiency of Al from Al(OH)[sub.3] reached 95.97%. The original dross, which is primarily composed of Al, Al[sub.2]O[sub.3], and AlN, undergoes a transformation where AlN becomes Al(OH)[sub.3] during washing. Thermal decomposition then yields Al[sub.2]O[sub.3]. The overall recovery of Al reaches 83.11%.