Phenolic compounds represent a class of recalcitrant organic pollutants that pose a persistent challenge in water remediation. In this work, a dual-functional composite, designated as PCT@Py-MOF(Fe), was fabricated by integrating a pyridine-functionalized MIL-101(Fe) framework with a polyurethane/chitosan-tannic acid interpenetrating polymer network (PU/CS-TA IPN). This material exhibited combined adsorption and photocatalytic functionalities. The Langmuir model fitted maximum adsorption capacities reached 326.72, 271.25, and 287.62 mg/g for bisphenol A (BPA), phenol, and hydroquinone (HQ), respectively, with the adsorption kinetics conforming well to the pseudo-second-order (PSO) model. Notably, the removal efficiency remained above 85% even after seven consecutive regeneration cycles. Under visible-light irradiation, the photocatalytic degradation of all three phenolics followed pseudo-first-order (PFO) kinetics, with the removal efficiency reaching over 95% for all three pollutants. Fixed-bed column breakthrough curves were accurately described by the Thomas model (R2 > 0.99), while the deviation between response surface methodology (RSM)-predicted and experimentally measured values was less than 0.5%. Mechanistic insights, derived from X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR), and density functional theory (DFT) calculations, revealed that adsorption was governed by Fe-site coordination, π-π stacking, hydrogen bonding, and electrostatic interactions. The photocatalytic activity, on the other hand, was attributed to the pyridine-induced narrowing of the bandgap from 2.96 eV to 2.87 eV, which facilitated the generation of superoxide radicals (·O2−) and hydroxyl radicals (·OH). Collectively, this study offers an efficient and stable dual-functional material alongside an integrated “adsorption-enrichment and photocatalytic degradation” strategy for the remediation of phenolic-contaminated water bodies.

Achieving selective flotation separation of spodumene from feldspar is challenging due to their comparable surface chemistry. In this study, a novel magnesium-based multi-ligand collector, Mg-OHA-NaOL, composed of Mg2+, octyl hydroxamic acid (OHA), and sodium oleate (NaOL), was developed to address the shortcomings of traditional collectors in terms of high dosage and poor selectivity. Micro-flotation results reveal that Mg-OHANaOL achieves a maximum recovery difference of 42.35% between spodumene and feldspar, significantly outperforming the binary Mg-NaOL and Mg-OHA systems. Mechanistic investigations revealed that Mg-OHA-NaOL exhibits stronger and more selective adsorption on the spodumene surface, as confirmed by contact angle measurements and in situ microcalorimetry. The enhanced wettability contrast between spodumene and feldspar is attributed to the co-adsorption of hydrophobic functional groups from both OHA and NaOL. Zeta potential, FTIR, and X-ray photoelectron spectroscopy (XPS) analyses further verified that the collector predominantly interacts with Al and Si active sites on the spodumene surface through the formation of electrically neutral [Mg2+center dot OHA-center dot OL-] coordination complexes. This structural configuration facilitates higher surface adsorption density and chemisorption strength, thereby amplifying hydrophobicity and flotation response. These findings provide mechanistic insight into the enhanced separation and offer guidance for designing efficient collectors for spodumene and other oxide minerals.

Frequent oil spills and complex oil-water contamination pose a serious threat to ecosystems, making the development of an efficient high-viscosity crude oil remediation material urgently needed. This study employed a HIPE template strategy to fabricate multifunctional foams integrating photothermal conversion, electrothermal response, superhydrophobicity, and photocatalytic activity in a single step. The prepared P(S5-E1-N3)/TiO2@PDA-PPy8 foam exhibited remarkable compressibility, outstanding superhydrophobicity (WCA = 157.1°, WSA = 1.5°), ultra-high continuous oil-water separation efficiency (≥99.7%), and oil-water emulsion separation efficiency (≥99.5%). Crucially, this material demonstrated exceptional photothermal and electrothermal conversion capabilities, with its surface temperature rapidly rising to 106.7°C under illumination and 119.4°C under voltage. Furthermore, the crude oil adsorption process under dual-effect synergistic heating proved approximately 76 times faster than conventional adsorption methods. Notably, this foam exhibited remarkable degradation efficiency (98.1%) for organic dyes, demonstrating outstanding photocatalytic activity.

The strategic significance of fluorite as a critical source for the fluorine industry has received attention, and flotation separation is the most common technique for enriching fluorite. The efficient flotation separation remains challenging due to the ubiquitous coexistence of calcite and barite with similar surface physicochemical properties. The lack of intrinsically selective collectors severely limits fluorite recovery and separation efficiency. Herein, we report a novel ether-functionalized hydroxamic acid collector, benzyloxyacetyl hydroxamic acid (BOHA), rationally designed by introducing an ether linkage (C-O-C) into benzohydroxamic acid (BHA) to enhance selective interfacial interactions with fluorite. Flotation separation results revealed that BOHA maintained >90% fluorite recovery and exhibited a large flotation recovery gap (Delta R) of similar to 70% relative to calcite and barite at optimal conditions, demonstrating improved floatability and selectivity compared with the traditional collectors. Combined with the spectroscopic analysis and theoretical simulation, it was revealed that the high selectivity and adsorption strength of BOHA toward fluorite stems from a synergistic adsorption mechanism, in which the ether oxygen and hydroxamic acid group cooperatively coordinate with surface Ca2+ to form CaO bonds and a stable bidentate five-membered chelation structure. In addition, the strong cation-pi interactions between the benzene ring of BOHA and the fluorite surface further enhanced the adsorption strength of BOHA based on the DFT calculations. This work establishes a molecular-level design strategy for high-performance fluorite collectors by integrating specific chemical bonding and non-covalent interactions, which offers fundamental insights and practical guidance for the selective separation of fluorite and other calcium-bearing mineral systems.

Beryllium (Be) in industrial solid wastes is highly mobile and highly toxic, making its long-term stabilization challenging and remobilization under changing environmental conditions likely. Inspired by natural mineralization processes, this study proposes an artificial mineralization strategy for Be immobilization based on aluminate-induced structural reconstruction. The stabilization performances of sodium aluminate, dicalcium silicate, and sodium silicate toward Be2+ were systematically compared, with sodium aluminate exhibiting the highest removal efficiency and stabilization capacity. Multiscale characterizations (XRD, TEM, XPS, and EELS) reveal that sodium aluminate undergoes hydrolysis to form an amorphous aluminum oxyhydroxide precursor dominated by an Al-O-(OH) framework, followed by progressive structural evolution and local ordering during long-term curing. No directly detectable well-crystallized Be-bearing phases were observed under the current characterization conditions. Instead, Be species are more likely present in highly dispersed or framework-associated states within the evolving aluminum oxyhydroxide matrix. In practical Be-containing lithium slag systems, over 99% Be immobilization is achieved, with negligible Be release observed over 120 days of curing. Our work demonstrates the potential feasibility of mineralization-assisted stabilization for highly toxic metals through coupled structural evolution and framework-associated immobilization processes, providing a theoretical basis and technical support for the geochemical stabilization of Be in complex solid waste systems.

Bastnaesite and gangue minerals share highly similar surface properties, making their efficient separation a long-standing challenge in mineral processing. Conventional collectors often suffer from drawbacks such as poor selectivity, limited collecting performance, and inadequate resistance to low temperatures, which restrict their flotation effectiveness. In this study, the surface active sites of bastnaesite and calcite were investigated, and based on these findings, a novel multifunctional cationic collector, BDDAB, was designed and introduced into the low-temperature flotation separation system of bastnaesite and calcite. BDDAB demonstrates superior collecting capability for bastnaesite compared to NaOL and DDA, enabling its efficient separation from calcite. Even under low-temperature conditions, BDDAB maintained outstanding collecting performance, demonstrating remarkable cold resistance. Upon adsorption on bastnaesite, BDDAB induced dense point-like adsorption features on the mineral surface, increased surface roughness, and significantly enhanced hydrophobicity, while the changes on calcite were relatively minor. When bastnaesite surfaces carried negative charges, BDDAB adsorption led to a pronounced positive shift, with greater shifts observed as the negative charge increased, indicating that electrostatic attraction was the dominant interaction. Furthermore, FTIR and XPS analyses revealed that hydrogen bonding, in addition to electrostatic forces, contributed to the adsorption mechanism. This study provides a novel collector and theoretical guidance for addressing the challenge of efficient low-temperature flotation of bastnaesite.

Gaining in-depth insights into the adsorption mechanism of collectors serves as the core scientific basis for achieving efficient spodumene (the most important lithium-bearing mineral) flotation. Due to the spodumene exhibits complex anisotropic surface properties, the quantitative understanding of the facet-dependent interaction between collectors and spodumene surfaces remains challenging. Herein, taking the typical collectors sodium oleate (NaOL) and dodecylamine (DDA) used in spodumene flotation separation, the chemical force microscopy technique was used to quantitatively measure the intermolecular interactions between collectors and different spodumene surfaces (110, 100, and 010) at the nanoscale. Adhesion measurements revealed that the adhesion forces of DDA with the (110), (100), and (010) surfaces were 21.7, 43.3, and 23.3 mN/m, respectively, with adhesion energies following the order (100) > (010) ≈ (110). Anisotropic adhesion was attributed to variations in the density of negatively charged O atoms on the surfaces. Conversely, the strong electrostatic repulsion between -COO- group and spodumene surfaces induced much weaker adhesion (1.7-8.8 mN/m) of NaOL toward all the surfaces. The adhesion energies between oleate ions and spodumene surfaces followed the order (110) ≈ (010) > (100), which correlated with differences in the number of exposed Al sites on the surfaces. Furthermore, the stronger adhesion between -NH3+ group and spodumene surfaces enabled DDA to adsorb more stably and effectively onto them, thereby enhancing the surface hydrophobicity and facilitating spodumene flotation. This study provides quantitative insights into the facet-dependent adsorption of collectors on mineral surfaces at the nanoscale, offering significant potential for establishing a quantitative link between mineral flotation behavior and the interaction forces between collector molecules and mineral surfaces.

The adsorption mechanism of octylhydroxamic acid (OHA) in the presence of metal ions during spodumene flotation remains poorly understood, representing a critical knowledge gap. This study systematically investigated the interaction mechanisms of OHA with Fe3+ and Ca2+ in spodumene flotation through micro-flotation experiments, Zeta, FTIR, XPS, and DFT. Micro-flotation experiments indicated that in the OHA system, both metal ions improved the floatability of spodumene. Better floatability was achieved with pre-mixed Ca-OHA complexes than with sequential addition of Ca2+ and OHA, whereas the opposite trend was observed for Fe3+ and OHA. Theoretical analyses confirmed that pre-mixing Fe3+ and OHA leads to precipitation, while the Ca-OHA complex forms a highly dispersed colloid. Zeta analysis indicated that the activation performance and interaction with OHA were stronger for Fe3+ than for Ca2+. Spectral analysis demonstrated that a stronger chemisorption mechanism for Fe3+ and OHA on the active Al sites compared to Fe-OHA, in contrast to the case of Ca2+ and OHA. The interaction region indicator (IRI) method was further employed to investigate the intermolecular interactions between OHA and the potential complexes. These results indicated that the interactions between OHA and Ca2+ are primarily governed by closed-shell interactions, whereas those with Fe3+ are dominated by partial covalent bonds along with other weak interactions. This work provides useful insights for improving spodumene floatability and for the further exploration, selection, and design of more efficient metal-based collectors.

Chlorine (Cl) in steel smelting wastes seriously restricts resource reutilization and poses significant environmental risks. During pyrometallurgical recovery of valuable metals, Cl promotes the formation of hydrogen chloride (HCl), leading to equipment corrosion, while chlorinated wastewater generated after smelting can cause severe water pollution. This study presents the first systematic review of Cl sources, transformation behavior, Cl-bearing smelting wastes, and Cl removal methods in steel smelting wastes. Based on industrial data, differences in Cl content of smelting raw materials across countries are analyzed, providing a basis for optimizing feed composition and process control. During ironmaking and steelmaking, chlorides are released at high temperatures as HCl and volatile metal chlorides, which are subsequently captured by dust collection systems to form Cl-containing smelting wastes; among these, sintering dust generally exhibits the highest Cl content. For Cl removal, organic chlorides in solid wastes are mainly treated by thermal methods, whereas inorganic chlorides are commonly removed by leaching. In wastewater treatment, precipitation remains the most widely used approach because of its simplicity and effectiveness, although it produces considerable chemical sludge. Developing green, selective, and cost-effective Cl removal technologies remains a key research priority.

Intact deep sandstone cores are scarce, heterogeneous with poorly repeatable, limiting systematic laboratory studies of deep-rock mechanical behavior. This study selected dense sandstone recovered from 1050 m in the Pingdingshan mining area as the prototype system for the development of a targeted-sandstone-constrained screening strategy for simulated deep sandstone. The strategy integrates mineral-composition matching, orthogonal mixture design, mechanical testing, PCA-based comprehensive similarity evaluation, GMM classification, stress–strain curve comparison and fracture-morphology verification. Candidate materials were prepared using a cement–silica-fume matrix with quartz sand, K-feldspar, Na-feldspar, nanoclay and superplasticizer. Results show that the water–binder ratio dominated uniaxial compressive strength, tensile strength and elastic modulus, whereas superplasticizer and nanoclay had secondary effects. The PCA-based index assigned weights of 52.9%, 29.2% and 17.9% to uniaxial compressive strength, elastic modulus and brittleness index, respectively. Among the 25 mixtures sampled, S5 showed the highest mechanical similarity, with a simulation index of 71.65% and a stress–strain curve similarity of 0.958. GMM clustering identified S5 and S10 as the closest high-strength, high-stiffness and high-brittleness group, while S10 better reproduced natural crack geometry. These results indicate that the optimal simulated sandstone depends on the target response and provide a task-oriented route for reproducible simulated deep sandstone.

Facet-dependent wettability is a fundamental yet poorly understood principle governing the stability, aggregation, and performance of 2D Janus materials in diverse separation processes such as oil recovery and pollutants adsorption. However, the direct and quantitative characterization of nanoscale wettability on individual nanosheets remains challenging. Natural serpentine was selected as a representative Janus nanosheet system comprising distinct MgOH, SiO and typical edge facets. A combination of atomic force microscopy (AFM) and extended Derjaguin-Landau-Verwey-Overbeek (EX-DLVO) theory was used to quantitatively characterize the facet-specific hydrophobicity of serpentine nanosheets. Hydrophobic interactions between individual facets and self-assembled monolayers functionalized AFM tips were quantified, followed by EX-DLVO fitting to extract hydrophobic decay lengths. To uncover the molecular origins of facet-dependent wettability, density functional theory (DFT) was performed to evaluate water adsorption configurations and energies. We report the first direct quantification of anisotropic wettability in Janus nanosheets. The MgOH and edge facets were fully hydrophilic, displaying no measurable hydrophobic interaction, consistent with stronger water adsorption energies (-27.62 and - 108.50 kJ mol- 1). In contrast, the SiO facet exhibited clear hydrophobicity, characterized by hydrophobic decay lengths of 1.00 +/- 0.05 nm (pH 5.5) and 1.20 +/- 0.05 nm (pH 8.5), which was supported by weaker water adsorption (-18.93 kJ mol- 1). The insights obtained in this work establish serpentine nanosheets as potential easily exfoliated Janus materials for separation processes involving enhanced oil recovery, emulsion separation, adsorption, and provide guidance for the design of mineral processing reagents.

The distribution of surfactants at interfaces and the resulting regulation of interfacial properties are fundamental to chemical engineering, particularly in the field of mineral flotation. Existing research have primarily focused surfactant adsorption at solid-liquid interfaces, while there is a lack of sufficient understanding of their role gas-liquid interfaces. To address the issue that octyl hydroxamic acid (OHA) possesses excellent flotation selectivity but has limitations in its gas-liquid interfacial properties, sodium oleate (NaOL) was introduced enhance the interfacial properties of OHA, thereby improving its stability and application performance. Foam stability and bubble population size distribution were evaluated and combined with density functional theory (DFT) calculations and molecular dynamics (MD) simulations to investigate macroscopic behavior molecular-scale interfacial characteristics. The addition of NaOL significantly reduces the gas-liquid interfacial tension of the OHA solution, increases the foam volume and foam life, thereby improving the foam stability the OHA system. Meanwhile, the addition of NaOL decreases bubble size and inhibits bubble coalescence, which promotes sustained bubble stability during continuous interfacial reaction processes. Simulations further reveal that NaOL enhances OHA hydration at the interface by increasing OHA-water binding energy and reducing diffusion coefficient of interfacial water, which potentially reduces liquid-film drainage and stabilize the foam film structure. This study provides a theoretical basis for optimizing of surfactants in flotation, as well as insights into regulating of surfactants performance in other fields involving gas-liquid interfacial processes.

Flotation is a technology that utilizes the differences in hydrophobicity of mineral surfaces to selectively adsorb mineral particles onto bubble surfaces. While traditional research predominantly focuses on mineral-reagent adsorption mechanisms, the role of the foam phase in the flotation process remains insufficiently investigated, particularly in mixed collector systems. In this study, the flotation performance of spodumene with different particle sizes in the NaOL/DDA mixed system was investigated from the perspective of foam properties. Flotation experiments on spodumene with different particle sizes demonstrated higher recovery for intermediate particle size; however, the adsorption heat and adsorption capacity of the agents on the surface of its mineral particles are not the highest. This suggests that the flotation performance of minerals with different particle sizes cannot be fully explained by reagent adsorption mechanisms alone. The results of two-phase foam properties analysis revealed that increasing the DDA proportion in the NaOL/DDA mixed system progressively decreased foaming capacity and foam stability. The results of three-phase foam properties analysis demonstrated that intermediate particle size resulted in significantly enhanced foam stability, consistent with observed flotation performance trends. Through zeta potential measurements, optical microscopy observations, and viscosity measurements, the mechanism of foam stability was studied. It was found that the distribution of surface charges on the bubbles regulated the stability of the foams. Electrostatic interactions not only control the flow rate of the liquid layer, but also indirectly regulate the adhesion of particles and bubbles, thereby affecting the flotation effect of minerals. This investigation provides a novel perspective on interpreting flotation phenomena in mixed collector systems.

Hetero-aggregation between serpentine and sulfide minerals represents a persistent challenge in the efficient recovery of valuable metals from complex ores, while most existing depressants suffer from limited selectivity, insufficient suppression efficiency, or environmental and toxicity concerns, restricting their application in sustainable mineral processing. Herein, we report for the first time the use of a phosphorylated nanocellulose biopolymer as a highly selective and environmentally benign depressant to overcome serpentine-induced interference in sulfide flotation, and elucidate the selective depression and interfacial mechanism. Phosphorylated cellulose nanofibers (P-CNF) and phosphorylated cellulose nanocrystals (P-CNC) were synthesized by introducing phosphate functional groups, resulting in a marked enhancement in pyrite flotation performance, with recoveries exceeding 88.0% and reaching 89.6% for P-CNF. The exceptional separation efficiency arises from the highly selective adsorption of phosphorylated cellulose on the serpentine MgOH plane, with a surface coverage of 96.32% on serpentine compared to only 0.28% on the pyrite surface. This pronounced selectivity induced a reversal of the serpentine surface charge, thereby transforming pyrite-serpentine interactions from electrostatic attraction to strong repulsion. Force-resolved atomic force microscopy measurements provided direct nanoscale evidence for this transition, revealing a dramatic reduction in adhesion forces from ∼9.81 mN m-1 to ∼1.25 mN m-1 (P-CNC) and ∼0.10 mN m-1 (P-CNF). Moreover, phosphorylated nanocellulose promoted the flocculation of fine serpentine particles via polymer-bridging effects, leading to the enlarged aggregates and effective suppression of mechanical entrainment. This work establishes phosphorylated nanocellulose as a novel green depressant platform and provides molecular insights into interfacial interactions governing complex mineral separation, thereby enabling the rational design of sustainable reagents and advancing resource-efficient environmentally interfacial responsible mineral processing.

High-efficiency recycling of secondary metal resources has been recognized as a critical pathway to achieving resource sustainability and advancing the circular economy. Current existing pyrometallurgical and hydrometallurgical recovery technologies remain unsatisfactory due to economic inefficiencies and environmental risks. Deep eutectic solvents (DESs), with their advantageous properties including strong adsorption, coordination, reduction, and proton dissociation capabilities, have attracted research attention in metal recovery. However, DESs-based recovery technologies remain in the experimental research stage. We critically assess the application progress of DESs in the recovery of various types of secondary resources, analyzing the coupled advantages of DESs as novel solvents-strong adsorption, acidity, complexation, and reduction capabilities. We emphasize the mechanism, advantages, and limitations of DESs in the leaching, separation, and extraction of metal components. Finally, we discussed its potential for green and efficient recycling, analyzed the challenges in promoting this technology, proposed process optimization strategies, and outlined future research directions and prospects. Through this review, we aim to provide theoretical support and important references for the efficient resource recovery of secondary metal resources using DESs, thereby accelerating its transition from laboratory research to industrial application.

Serpentine is easily activated by metal ions and floats upward into the concentrate in the flotation separation of copper-nickel sulfide ores, resulting in increased MgO content, which seriously affects the downstream smelting process. However, the specific adsorption mechanisms of metal ions on serpentine surfaces remain unclear, resulting in a challenge in the modulation of serpentine flotation behavior. In this work, the effect of inevitable divalent metal ions (e.g., Mg(II), Ca(II), and Cu(II)) on serpentine floatability was systematically investigated. Flotation results showed that serpentine without treatment with divalent metal ions has weak floatability, whereas the introduction of divalent metal ions increased serpentine flotation recovery by similar to 10 % after Ca or Mg treatment and similar to 15 % after Cu species treatment. Spectroscopic and surface topography imaging analysis revealed imaging revealed that Mg(II) exhibited weak adsorption, primarily in the outer sphere, on the Mg-OH plane; whereas Ca(II) tends to adsorb onto the edge planes. Notably, Cu(II) demonstrated the strongest adsorption ability, binding with O- residue on the Mg-OH plane and edge planes via Cu-O bonds. Density functional theory calculations also revealed an increasing order of collector adsorption affinity: Cu(II) > Ca(II) > Mg(II). Therefore, serpentine after Cu treatment can provide more sites for the adsorption of collectors, enhancing its floatability of serpentine. This study provides molecular interaction mechanisms of inevitable ion adsorptions on serpentine surfaces, which can offer theoretical guidance for chemical additives design and surface reaction control in minerals separation processes.

The surface characteristics of bastnaesite and barite are highly similar, leading to comparable reagent interactions during flotation processes. Conventional collectors often demonstrate limited selectivity and suboptimal collection efficiency, which negatively impact flotation outcomes. Effective mineral separation requires highly selective and efficient collectors. This study presents the synthesis and initial application of lauryl hydroxamic acid (LHA) as a new collector for the flotation of bastnaesite. LHA exhibited remarkable selectivity and collecting efficiency in the flotation separation of bastnaesite from barite. The synergistic application of LHA and carboxymethyl cellulose (CMC) as depressants enabled effective separation. This resulted in a recovery difference of up to 66.5 % between the two minerals. Spectroscopic analysis revealed that LHA interacts with Ce sites on bastnaesite surfaces through N and O atoms in its hydroxamate groups. Pre-adsorption of CMC was found to prevent LHA adsorption on barite without affecting its adsorption on bastnaesite. LHA adsorbs through the synergistic effect of electrostatic interaction and chemisorption. Comparative analysis indicated that LHA's hydroxamate group possesses lower non-bonded tension than traditional octyl hydroxamic acid (OHA), enhancing its chelate-forming capability. Density Functional Theory calculations identified hydroxamate groups as LHA's primary active sites, with O and N atoms playing critical roles. This research systematically investigates the potential of LHA for bastnaesite-barite separation and elucidates its adsorption mechanism. The findings not only advance theoretical understanding of selective flotation control but also provide molecular design guidelines for novel collector development.