The method of recovering copper from high combination-ratio oxidized copper ores was studied using sodium fluoride-enhanced sulfuric acid leaching. Without a roasting pretreatment step, the leaching process was carried out directly under atmospheric conditions using a gyratory water bath. The leaching mechanism was investigated under the optimal leaching conditions, i.e., T = 30 degrees C, reaching time = 4 h, L/S ratio = 2 mL/g, H2SO4 concentration = 0.05 mol/L and NaF concentration = 0.06 mol/L. The results demonstrated that under optimal leaching conditions, approximately 70.8% of the copper was leached into the solution, whereas the copper leaching efficiency was only around 50.6% without sodium fluoride as a leaching aid. XPS, XRD and DFT calculations elucidate that the enhancement mechanism is primarily driven by a ligand-exchange process, where fluoride ions displace lattice hydroxyl groups on the surface of minerals. The enhancement is primarily driven by a ligand-exchange process, where fluoride ions replace the lattice hydroxyl groups on the goethite surface. The extraction mechanism is primarily driven by the fluoride-assisted dehydroxylation and ligand substitution on the mineral surface. These findings suggest that fluoride-assisted acid leaching provides a promising technical and methodological approach for enhancing the hydrometallurgical recovery of high combination-ratio oxidized copper ores.

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.

For a long time, it has been quite difficult to effectively carry out flotation separation of magnesite and calcite owing to the fact that their physicochemical properties are essentially very similar. However, the primary interfacial mechanisms causing this similar flotation behavior are unknown, impeding predictions of site distribution in the carbonate mineral-collector system. In this study, a multiscale surface complexation modeling (SCM) combining dissolution kinetic, adsorption isotherm, and spectral characterization data was developed. The results demonstrate that magnesite and calcite followed a three-zone dissolution pattern, which was jointly controlled by proton and surface complexation reactions. The release of Mg2+ and Ca2+ ions from the crystal lattice regulated the evolution of surface sites and surface wettability. According to the SCM, the surface densities, protonation constants and species distributions of the magnesite and calcite were very similar. The control of sodium oleate (NaOL) adsorption was via dissolved-ion bridging bidentate-binuclear coordination mechanism operating on -MeOL and -CO3MeOL sites. Calcite demonstrated a marginally higher intrinsic binding affinity than that of magnesite, however, its offset by multisite interactions led to similar adsorption capacities and floatability. XPS and SEM-EDS evidence confirmed the formation of multisite complexes, which were also predicted by the SCM. These findings offer molecular insights into the differing adsorption behavior of NaOL, which enhances our understanding of the reactivity at the flotation interface of carbonate minerals. They could also provide a theoretical basis for controlling and predicting the flotation behavior of carbonate minerals.

The sulphidation flotation process is one of the most effective methods for recovering copper oxide minerals. However, a systematic quantitative understanding of the reaction mechanisms of sulfidation at the molecular level remains lacking, limiting the prediction of malachite surface reactivity and regulation of flotation behavior. This study established a surface complexation model (SCM) framework to elucidate and quantify the microscopic mechanisms underlying sulfidation on the malachite surface. Based on acid-base titration and adsorption data, the results indicate that there were two initial active sites on the malachite surface: -CuOH and -CO3H. The copper active site (-CuOH) exhibited a strong affinity for HS- species, forming a stable monodentate -CuSH complex. In contrast, the adsorption of S2- species was negligible. Crucially, these thermodynamic descriptions were indirectly supported by XPS and SEM-EDS. By integrating multiscale information obtained from zeta potential and adsorption experiments, the model can accurately predict the surface charge transfer characteristics and sites distribution. Furthermore, the model predicted binding density exhibited a highly consistent positive correlation with flotation performance not only in pure mineral systems but also in bench-scale flotation of actual copper oxide ores. This study provides an innovative perspective on the surface reactivity and sulfidation mechanisms of malachite, offering broad prospects for future the optimization of copper oxide ore sulfidation flotation processes and intelligent mineral separation.

Red mud (RM), an industrial by-product of the alumina refining industry, poses severe environmental risks of water, air and soil contamination if improperly disposed due to its inherent high alkalinity. Herein, a highly efficient dealkalization strategy for RM is proposed to mitigate the accumulation of industrial waste and realize the "Red to Green" valorization of RM. This study synergistically utilizes two industrial wastes, RM and TiO₂ waste sulfuric acid (TWSA), to achieve acid leaching dealkalization of RM. Under the optimal conditions of a liquid-to-solid ratio of 4mL/g, a TWSA concentration of 0.4mol/L, a leaching temperature of 50 °C and a leaching time of 30min, the dealkalization rate of Bayer process RM reached 87.69%. The dealkalization process of RM using TWSA can be broadly divided into two distinct stages. In the first stage, the free alkali in RM undergoes a neutralization reaction with H⁺ released from TWSA, leading to the removal of a portion of the free alkali. In the second stage, TWSA reacts with calcite, tricalcium aluminate, catoite, sodalite and cancrinite in RM, resulting in the liberation and removal of bound alkali. This integrated process not only delivers a favorable dealkalization efficiency but also simultaneously valorizes two problematic industrial wastes, demonstrating significant commercial potential. A preliminary techno-economic analysis reveals that the production of RM-based bricks using 1t of dealkalized RM yields a net profit of 25.98 USD, providing strong evidence for the industrial scalability of this approach and enabling the sustainable "Red to Green" conversion of RM.

The effective recovery of highly alkaline copper oxide ores remains a significant challenge, as the close mineralogical association between calcareous gangue and target minerals. To achieve flotation separation, the selective depressants are necessary, but traditional depressants have various limitations. In this study, a novel depressant containing multipolar groups, disodium glycerophosphate (DGP), was investigated for its selective depression of dolomite. Micro-flotation results for mixed minerals showed that 80 mg/L of DGP yielded a high malachite recovery of 91.61% while sharply suppressing dolomite recovery to 18.83%. These findings were validated by bench-scale tests on natural highly alkaline copper oxide ores (sulfidization-xanthate system), establishing DGP as a highly efficient selective depressant for carbonate gangue. The adsorption mechanisms of DGP were comprehensively elucidated through a combination of zeta potential measurements, contact angle analysis, FTIR, XPS, SEM-EDS, and DFT calculations. The results demonstrated that DGP selectively and strongly adsorbs onto the dolomite surface, significantly enhancing its hydrophilicity and thereby competitively inhibiting the subsequent adsorption of sodium oleate (NaOL). The depression mechanism is primarily driven by the interaction between phosphate groups in DGP and the Ca/Mg active sites on the dolomite surface. These findings suggest that DGP provides a promising technical and methodological approach for enhancing the flotation efficiency of refractory copper oxide ores.

Calcium silicate-based materials hydrate to form calcium silicate hydrate (C-S-H), a reactive phase capable of immobilizing heavy metals. However, the mechanisms governing element-specific long-term stability remain unclear. In this study, dicalcium silicate (C2S) and tricalcium silicate (C3S) were used to compare the removal behavior, aging stability, and microscopic immobilization mechanisms of Pb(Ⅱ) and Cd(Ⅱ) in aqueous systems. Both minerals efficiently removed Pb(Ⅱ) and Cd(Ⅱ), while C3S showed stronger early Pb(Ⅱ) removal, possibly related to faster hydration-product formation under the tested conditions. Cd(Ⅱ) removal remained above 99% in both systems. Apparent isotherm and kinetic analyses indicated that metal removal was governed by a coupled apparent process involving interfacial adsorption, surface complexation, hydration-product formation, and precipitation, rather than by physical adsorption alone. Long-term aging and acidic leaching tests revealed contrasting stability: Cd-bearing products exhibited strong leaching resistance, whereas Pb-bearing products showed a potential risk of re-release after aging. XRD, XPS, TEM, and TEM-EDS analyses indicated that Pb and Cd were closely associated with C-S-H-related hydration products, suggesting possible Ca-associated binding or partial structural incorporation. The stronger acid-leaching resistance of Cd-bearing products implies more stable association with C-S-H-related phases than that of Pb-bearing products. These findings clarify the element-specific immobilization mechanisms of C2S/C3S and provide guidance for calcium silicate-based treatment of heavy-metal-contaminated water.

The adsorption of metal ions on the mineral-liquid interface can significantly affect the minerals surface properties and flotation behavior. Despite the establishment of various surface complexation models, the lack of comprehensive understanding regarding silicate mineral surface reactivity and their metal ions adsorption affinity constants has hindered accurate prediction of metal ions adsorption by silicate minerals. Herein, the diffuse layer model (DLM) was developed to describe the Mg adsorption on K-feldspar and muscovite interfaces. The model effectively revealed the surface charge characteristics and adsorption distribution of Mg species on both minerals. Mg2+ ions were bound to permanently negatively charged sites on the muscovite basal surface by ions exchange. With increasing concentration of Mg, the muscovite edge surface sites became the primary sites for the adsorption of MgOH+. The model successfully predicted the surface charge and Mg sites distribution properties of two minerals. Combined with XPS, SEM-EDS, and DFT analyses, the results further revealed the mechanism of Mg adsorption on the mineral surfaces and its dominant components, and provided feedback for model fitting. The model approach based on species parameters developed in this study demonstrates significant practical utility and application potential, particularly in the field of mineral flotation separation. This study provides new insights into the adsorption mechanism of metal ions on mineral interfaces by linking macroscopic adsorption behavior with molecular-scale surface speciation.

The combination of metal ions and organic collectors has been widely utilized in mineral separation processes, however, there is a poor quantitative understanding of their adsorption mechanisms and effects. Although various surface complexation models have been established, the absence of metal ions and organic reagents affinity constant of oxidized ore impedes the prediction of metal ion-organic reagent adsorption behavior of minerals in the flotation process. The objective of this work is to develop the surface complexation model (SCM) for the ternary system hematite/quartz-Ca-sodium oleate. The results indicate that the binding of Ca on the surface sites of hematite and quartz was mainly dominated by monodentate adsorption (- FeOCaOH and - SiOCaOH), corresponding to adsorption constants (logK) of 6.03 and 6.80, indicating that Ca ions are more readily adsorbed on the quartz surface. Furthermore, the binding constant of - SiOCaOL site was 16.28, that of - SiOHCa(OL)2 site was 21.70, that of - FeOCaOL site was 14.96, and that of - FeOHCa(OL)2 site was 20.64, demonstrating a strong synergistic interaction between Ca ions and NaOL from a quantitative perspective. Based on these adsorption affinity constants, the surface reactivity of quartz and hematite were successfully predicted from both different NaOL concentrations and slurry pH values. This finding provides insight into the mobility and coordination of Ca(II) and NaOL in solution and provides a method to quantify the adsorption behavior of metalbased collectors in multi-mineral systems.

Metallic arsenic is a critical raw material in the semiconductor industry.Arsenic-alkali slag from antimony smelting contains a high concentration of arsenic and has a complex composition.The key to preparing metallic arsenic lies in the efficient separation of arsenic from various impurities.In this study,based on the geochemical mineralization principles of arsenic,we propose an innovative theory of high-precision mineralization and precipitation of arsenate complex salts.We developed a key technology involving one-step reduction roasting of arsenate complex salt precursors for metallic arsenic production.This approach overcomes the challenges of efficiently separating arsenic and alkali in high alkali/salt solutions and similar issues with impurity separation,enabling a shortened process for converting arsenic-containing solid waste into high-purity metallic arsenic.Our findings show that oxidative leaching using hydrogen peroxide enables effective and selective removal of arsenic from arsenic-alkali residue.The liquid-solid ratio,temperature,and hydrogen peroxide dosage significantly influence the leaching rate.Under optimal reaction conditions,the leachate contains high concentration of alkali,arsenic,and sulfur.Carbonation of the leachate allows for alkali recovery,yielding a product with an alkali content of up to 98.79%and a uniform particle size distribution.Arsenate salt mineralization and precipitation achieve selective separation of arsenate from bicarbonate and alkali.With increased dosage of ammonium salts and magnesium sources,the arsenic removal rate improves.The arsenic content in slag increases with magnesium salt dosage and then decreases.Reaction time positively influences arsenic removal,while higher temperatures reduce both the arsenic removal rate and the arsenic grade in slag,the latter reaching 29.75%.Through reduction roasting of high-arsenic slag using carbon powder,metallic arsenic with 99.81%purity was obtained.The monomeric arsenic contained only 0.03%antimony and 0.16%sulfur impurities.Analysis of the reduction roasting and condensation processes,considering the temperature and Gibbs free energy,indicates that to maintain the quality of the metallic arsenic monomers,sulfate reduction should occur at 620 ℃.Increasing the carbon powder dosage or elevating the roasting temperature promotes reduction volatilization and lowers sulfur impurity content in the final product.This study provides both a theoretical basis for the resource-efficient disposal of arsenic-containing solid waste and technical support for the efficient preparation of metallic arsenic.

Dolomite often is found as a gangue mineral and shares similar chemical properties with the malachite, posing a significant challenge to the effective separation of copper oxide ore. There are many studies on the depressants of dolomite, however, those applicable to the flotation system of copper oxide ore have not been reported. In this study, the sodium methyl-phosphonate sulfonate (SMPS) was first introduced as a selected depressant of dolomite for effective separation from malachite. The micro-flotation results indicated that SMPS had selective depressant of dolomite flotation, while it was pretty poor for malachite. The batch flotation experiments further demonstrated that SMPS was an effective dolomite depressant. Zeta potential measurement and FTIR analysis suggested that the addition of SMPS powerfully stopped the NaOL adsorption onto dolomite surface, with little influence on malachite, leading to remarkable differences in their floatability. XPS analysis demonstrated that the SMPS adsorption onto dolomite can be contributed to the interaction of the electron-rich -SOO- group of SMPS with the Ca and Mg exposed in dolomite-water interface. DFT calculations indicated that the sulfonic acid groups in SMPS reacted strongly with the dolomite Mg sites, which was significantly stronger than that of sodium oleate (NaOL), further demonstrating the greater chemical bonding ability of SMPS onto dolomite. These findings provide promising insights into the potential of SMPS as critical depressant for optimizing the flotation of copper oxide ores.

The large amount of heavy metals from waste electroplating sludge has great recovery and treatment value, which is of great significance for environmental protection, resource recycling and sustainable development. In actual process, metals were relatively easy to be extracted from sludge, but the separation process was more complex. In this study, three universal methods for extracting low-grade and complex heavy metals from electroplating sludge (actual solid waste sample from Zhejiang Province, China) in terms of Selective ammonia treatment process (SAP), efficient acid treatment process (EAP) and roasting-acid treatment process (RAP) were investigated. In comparison, EAP was more advanced in extracting heavy metals from actual samples than SAP and RAP. It was noticed, by optimizing the separation and purification process, when the acid concentration was 5 % and the liquid-solid ratio was 10:1 with the assistance of effective extractants of Lix984N and P507, the purity and recovery rates for both copper and zinc products could reach to over 90 %, meanwhile, more than 80 % recovery rates of nickel products could be obtained. And compared with some existing related studies, the research process has the advantages of simpler operation mode and better separation effect, which offers the valuable insights into efficient separation and recovery of heavy metal resources from electroplating sludge. The methodology employed in this work can be easily applied to other solid/hazardous waste extraction processes.

Sulfide minerals are the critical sources for extracting valuable nonferrous metals such as lead, copper, and zinc, which are indispensable across various industrial sectors. Flotation is the pivotal technology for separation and enrichment of these sulfide minerals. The core mechanism of flotation lies in the selective adsorption of flotation reagents on the minerals surface. However, there are few quantitative studies regarding the protonation reaction of active sites on the surface of sulfide minerals. In this research, the Surface Complexation Model (SCM) is innovatively applied to quantitatively analyze the protonation characteristics of active sites on sphalerite, galena, pyrite, and chalcopyrite surfaces, providing the basis for clarifying the adsorption behavior of flotation agents and developing efficient reagents. By analyzing the crystal lattice structures and cleavage plane characteristics of the minerals, the types of active sites were determined. Subsequently, the hydrogen ion interactions with mineral surfaces was investigated by potentiometric titration, and the equilibrium equations of protonation reaction was established. The corresponding protonation constants and site densities were calculated by iterative fitting using Newton-Raphson method. In the process of data validation, the theoretical and fitted site densities of the mineral primary cleavage planes were compared. Additionally, by substituting the protonation constants into the equilibrium equations, a high correlation between the fitted surface potential under different pH conditions and the measured zeta potential values was revealed. This result confirms the accuracy of the fitted protonation constants and site densities and further validates the reliability of the Surface Complexation Model. For the first time, this research systematically applies the surface complexation model (SCM) to accurately analyze the protonation characteristics of the surface active sites of typical sulfide ores, which provides an important prerequisite for deepening the understanding of the interaction between the typical sulfide ore surfaces and reagents and the surface charge distribution. It is helpful to improve the flotation process and design flotation reagents, thereby enhancing the efficiency and accuracy of the beneficiation process.

Competitive adsorption behavior of reagents is of great significance for efficient flotation separation of minerals. Motivated by the surface complex adsorption, surface complexation model (SCM) is an effective approach for quantitative characterization of reagents adsorption behavior. In this study, sodium humate (SH) adsorption and mixed SH and dodecylamine (DDA) competitive adsorption mechanisms onto hematite and quartz were quan-titatively described and predicted using SCM. The model simulation suggested that there are two binding forms (monodentate and bidentate) between the groups on SH and the hematite sites and one (monodentate) with the quartz sites. The adsorption equilibrium constants (logK) of SH were calculated, which are 10.15, 23.34 (for hematite) and 10.41 (for quartz), respectively. In addition, the fitting results indicate that SH is adsorbed on the hematite surface mainly through the bidentate equivalent to Fe2-R(COO)2 site. Furthermore, the successful prediction of adsorption and surface potential at pH system were performed to verify the reliability of the model. Quantitative analysis of mixed SH and DDA interactions with mineral surfaces will elucidate and predict the reagents competitive adsorption behavior, which can also provide reliable data and parameters for surface complexation databases for surface complexation. Meanwhile, this finding provides valuable insights for the flotation of minerals, which enables their selective separation efficiency to be modulated and optimized.

The effective improvement of dewatering performance of fine tailings slurry is a common challenge in tailings disposal and mining environmental protection worldwide. Flocculation is a commonly used method for solid-liquid separation of tailings, and the properties and structure of tailings flocs play a key role in sedimentation and filtration performance. This study proposed to improve the dewatering efficiency of tailings by regulating the floc properties and structure through polycarboxylate ether/ester (PCE). It simultaneously enhanced dewatering speed and reduced filter cake moisture. Dewatering experiments results showed that the assistance of PCE increased the initial filtration rate (IFR) of tailings by approximately 60 % and reduced filter cake moisture by 4.16 %. Moreover, the increase of shear strength in the slurry had a detrimental effect on dewatering performance. The dynamic evolution process of flocs was studied using focused beam reflectance measurement (FBRM) technology. The results showed that the addition of PCE caused a significant increase in floc size and counts, while the structural strength and regrowth ability of flocs also improved. Floc density calculations and scanning electron microscope (SEM) observations revealed that PCE caused densification of flocs, with particles aggregating more compactly. Contact angle analysis indicated that the adsorption of PCE on particles surface weakened their hydrophilicity. This study could conduce to understand the mechanism of dewatering performance enhancement in solid-liquid separation.

The interaction of surfactants at minerals-water interfaces in flotation system plays an important role in minerals separation. Although the increasing number of reports have been published on the sodium oleate (NaOL) adsorption at the mineral-water interface, there has been little development in describing and predicting its adsorption behaviors from a quantitative molecular insight. In this study, based the adsorption experiments, the adsorption characteristics of NaOL on the hematite/quartz-water interfaces were quantitatively depicted using the surface complexation model (SCM). There was a monodentate binding form between the function group on NaOL and the hematite and quartz surface sites during SCM fitting. The binding constants (logK) of NaOL are 10.72 (-Fe-OL) and 8.03 (-Si-OL), respectively. Notably, there are more positive -FeOH2+ site on the hematite surface, and it has strong adsorption capacity with anionic surfactant NaOL. Moreover, the minerals surface potentials, NaOL adsorption capacity and flotation recovery in mixed ore systems were successfully predicted by the model. This study provides a credible evaluation of the adsorption characteristics of NaOL under a broad scope of pH and concentration conditions. Meanwhile, quantitative analysis of surfactants adsorption at minerals-water interfaces is beneficial for the intelligence of mineral processing technology and efficient separation of minerals.

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Use of mixed collectors in froth flotation confirmed effective separation of minerals with better selectivity and synergistic effects. But the underlying interaction mechanism still keep vague and have not been interpreted clearly so far. This work proposed a quantitative perspective to account for experimental flotation behavior from active site calculation, which has not been involved in flotation areas yet. Specifically, the mineral site distri-butions of diaspore and kaolinite were quantitatively characterized through calculated collector (sodium oleate (NaOL) and benzohydroxamic acid (BHA)) adsorption intrinsic constants. The algorithm principle was radically different from common homogeneous solution system without electric double layer. Using collector adsorption constants, all the initial and adsorbed product sites were counted in any circumstances to compare with corre-sponding flotation tests. The results showed that the 5 % higher recovery of diaspore at NaOL/BHA = 9:1 was attributed with 2 % more adsorption sites occupied than a single NaOL when both doses were controlled at 5 x 10-4 mol/L. On the contrary for kaolinite, the overall coverage of collectors was much smaller, indicating its poor recovery. Despite 10 % NaOL replacement by BHA in mixed collectors, neither the adsorbed site content nor the flotation efficiency for kaolinite was facilitated finally. Therefore, the significant discrepancies in adsorptions and flotations between diaspore and kaolinite contribute to their separation with the better selectivity of mixed NaOL/BHA than individual NaOL. The method established in this study may draw further attention for complex collector adsorption to facilitate flotation development.

The recovery of low grade and fine particle copper ore usually requires sufficient dissociation, which reduces the particle size to the submicron level, presenting new challenges in subsequent copper tailings disposal. Flocculants can improve tailings sedimentation efficiency, but they also change the rheological properties of the slurry, resulting in low efficiency and high energy consumption during long-distances pumping. To address this issue, this study introduced polycarboxylate ether (PCE) superplasticizers as auxiliary additives for tailings treatment to improve fine particles sedimentation efficiency while enhancing slurry flowability. The results showed that compared to non-ionic polyacrylamide (NPAM) treated slurries, the synergistic effects of PCE and NPAM increased the initial sedimentation rate (ISR) by up to 3.4 times while decreasing the yield stress by up to 8 times and the thixotropic loop area by 10.5 times. DLVO theory calculations showed that PCE mainly affects particle interactions through a significant decrease in electrostatic repulsion. By in-situ monitoring with a focused beam reflectance measurement (FBRM) device, it was demonstrated that the synergistic effect of PCE improved the flocculation ability, strength, and regrowth ability of flocs. Furthermore, strong correlations were found between floc properties and fluid rheological properties. Overall, this study indicated that PCE additive was a promising reagent for fine particles slurry rapid settling and flowability enhancement, providing a new approach for copper tailings disposal.