Effect of Sulfuric Acid Corrosion on Flotation Performance of Calcite by Changing Surface Roughness.

Surface roughness is a crucial factor that affects the flotation performance of minerals. In this study, the effect of sulfuric acid corrosion on the surface roughness of calcite flotation was investigated through microflotation tests, scanning electron microscopy (SEM-EDS), atomic force microscopy (AFM), Fourier transform infrared (FT-IR) spectroscopy, and contact angle analysis. Microflotation test results show that sulfuric acid treatment has a serious negative effect on the floatability of calcite. When the sulfuric acid dosage was 4 mL (3 mol/L), the flotation recovery of calcite was reduced to less than 19%. SEM-EDS and AFM results verified that the sulfuric acid treatment significantly changed the surface morphology of calcite, reduced the average surface roughness and surface area, and reduced the amount of active Ca2+ sites on the calcite surface. As characterized by FT-IR and contact angle analyses, the sulfuric acid treatment enhanced the hydrophilicity of the calcite surface and reduced the amount of sodium oleate adsorbed on the calcite surface. Consequently, sulfuric acid corrosion can reduce the average surface roughness of calcite and have a serious negative effect on the flotation performance of calcite.

Formulation of ferric/phosphorus composite coating on coal gangue as a novel fertilizer for enhancing slow-release of silicon and implication of As, Cr and Pb.

Owing to the abundant silicon content in coal gangue, its conversion into fertilizer can help address large-scale storage. Nonetheless, the rapid release of silicon in coal gangue poses challenges for plants to fully utilize it. A slow-release fertilizer prepared by ferric/phosphorus composite coating on coal gangue (C@SP) was developed in the study. The findings revealed that the C@SP can facilitate slow release of Si and enhance the stabilization of As, Pb, and Cr in soil. C@SP can react with As and Cr to form stable Fe-As-PO4 and Fe-Cr-PO4 compounds. The -OH in C@SP can combine with Pb, transforming it into insoluble Pb, which was then integrated into the crystal structure with ferric/phosphorus composite or Fe(III)-oxyhydroxysulfate to create a more stable form. The silicon release was promoted by the conversion of the passivation film to iron oxides. Thus, the fertilizer holds promise for application in environmental activities.

Efficient benzo(a)pyrene degradation by coal gangue-based catalytic material for peroxymonosulfate activation.

A low cost and green peroxymonosulfate (PMS) activation catalyst (CG-Ca-N) was successfully prepared with coal gangue (CG), calcium chloride, and melamine as activator. Under the optimal conditions, the CG-Ca-N can remove 100 % for benzo(a)pyrene (Bap) in an aqueous solution after 20 min and 72.06 % in soil slurry medium within 60 min, which also display excellent reuse ability toward Bap after three times. The removal of Bap is significantly decreased when the initial pH value was greater than 9 and obviously inhibited in the presence of HCO3- or SO42-. The characterization results indicated that the addition of calcium chloride could stabilize and increase the content of pyridinic N during thermal annealing, resulting in the production of •OH, SO4•- and 1O2. Based on electron paramagnetic resonance (EPR) and active radical scavenging experiments, 1O2 could be identified to be the dominant role in Bap degradation. Overall, this work opened a new perspective for the low cost and green PMS catalysts and offered great promise in the practical remediation of organic pollution of groundwater and soil.

Integrated CO2 capture and conversion via H2-driven CO2 biomethanation: Cyclic performance and microbial community response.

This study investigated the use of H2-driven CO2 biomethanation for integrated CO2 capture and conversion (iCCC). Anaerobic chambers containing Na2CO3-amended microbial growth medium provided with H2 were inoculated with anaerobic granular sludge. Microorganisms were enriched that could regenerate carbonate by using the bicarbonate formed from CO2 absorption to generate methane. Multiple absorption-regeneration cycles were performed and effective restoration of CO2 absorption capacity and stable carbonate recycling via CO2 biomethanation were observed for CO2 absorbents adjusted to three different pH values (9.0, 9.5, and 10.0). The pH = 10.0 group had the highest CO2 absorption capacity; 65.3 mmol/L in the 5th cycle. A slight alkaline inhibition of acetoclastic methanogenesis occurred near the end of regeneration, but had limited impact on the cyclic performance of the iCCC process. Microbial communities were dominated by H2-utilizing and alkali-tolerant species that could participate in CO2 biomethanation and survive under alternating neutral and alkaline conditions.

A review of flotation reagents for bastnäsite-(Ce) rare earth ore.

Given the indispensability and immense value of rare earth elements for scientific and technological advancements in the 21st century, extracting high-quality rare earth resources from nature has become a global priority. Bastnäsite-(Ce) is one of the known rare earth minerals with high rare earth content and wide distribution, which occupies a pivotal position in human life and high-end production activities, making its efficient development and utilization crucial. In recent years, research on separating bastnäsite-(Ce) from gangue minerals has focused on the flotation process, with flotation reagents playing a critical role in achieving effective separation. This paper provides a detailed summary of current research on the behavior of bastnäsite-(Ce) flotation agents on minerals, their interaction with mineral surfaces during flotation separation, and outlines future prospects for further research.

Self-Healing Liquid Metal Magnetic Hydrogels for Smart Feedback Sensors and High-Performance Electromagnetic Shielding.

Hydrogels exhibit potential applications in smart wearable devices because of their exceptional sensitivity to various external stimuli. However, their applications are limited by challenges in terms of issues in biocompatibility, custom shape, and self-healing. Herein, a conductive, stretchable, adaptable, self-healing, and biocompatible liquid metal GaInSn/Ni-based composite hydrogel is developed by incorporating a magnetic liquid metal into the hydrogel framework through crosslinking polyvinyl alcohol (PVA) with sodium tetraborate. The excellent stretchability and fast self-healing capability of the PVA/liquid metal hydrogel are derived from its abundant hydrogen binding sites and liquid metal fusion. Significantly, owing to the magnetic constituent, the PVA/liquid metal hydrogel can be guided remotely using an external magnetic field to a specific position to repair the broken wires with no need for manual operation. The composite hydrogel also exhibits sensitive deformation responses and can be used as a strain sensor to monitor various body motions. Additionally, the multifunctional hydrogel displays absorption-dominated electromagnetic interference (EMI) shielding properties. The total shielding performance of the composite hydrogel increases to ~ 62.5 dB from ~ 31.8 dB of the pure PVA hydrogel at the thickness of 3.0 mm. The proposed bioinspired multifunctional magnetic hydrogel demonstrates substantial application potential in the field of intelligent wearable devices.

Synergistic Mechanism of Combined Inhibitors on the Selective Flotation of Arsenopyrite and Pyrite.

The selective action mechanism of sodium butyl xanthate (BX), ammonium salt (NH4 +), and sodium m-nitrobenzoate (m-NBO) on pyrite and arsenopyrite was examined by experiments and quantum chemistry. The experiments show that under alkaline conditions, ammonium salt (NH4 +) and m-NBO can have a strong inhibitory effect on arsenopyrite. At pH 11, the recovery rate of arsenopyrite reduces to 16%. The presence of ammonium salt (NH4 +) and m-NBO reduces the adsorption energy of BX on arsenopyrite to ΔE = -23.23 kJ/mol, which is far less than the adsorption energy on the surface of pyrite, ΔE = -110.13 kJ/mol. The results are helpful to understand the synergistic mechanism of the agent on the surface of arsenopyrite and pyrite, thus providing a reference for the selective separation of arsenopyrite.

Opportunities and challenges in microwave absorption of nickel-carbon composites.

In recent years, the problem of electromagnetic wave (EMW) pollution has attracted more and more attention with the development of science and technology. In order to solve this complex problem, the research and development of EMW-absorbing materials is crucial. The new absorbing materials should have the characteristics of light weight, high efficiency, wide bandwidth, environmental protection, oxidation resistance, and other characteristics. Traditional single-phase Ni materials exhibit remarkable ferromagnetic behavior and double-loss mechanisms (dielectric loss and magnetic loss), and are considered as efficient EMW absorbers. However, under the action of EMWs, especially in the GHz frequency band, Ni materials tend to produce an eddy current effect, which limits their application prospects. For Ni-based materials, there is much interest in modifying the composite materials by designing a hierarchical structure for their preparation. Traditional, single-phase, carbon-based materials have been widely used in related fields because of their light weight and good conductivity. However, a single-loss mechanism will affect the impedance matching of carbon materials, thus affecting their application in the field of absorbing waves. For carbon materials, people use them as a filler or matrix material to fabricate composites with metals, metal oxides, or polymer materials to obtain carbon-containing absorbing materials. This paper reviews the evaluation and design principles of the absorbing properties of EMW-absorbing materials. Then, the progress of modified single-phase Ni-based materials (designed materials with 0D, 1D, 2D, and 3D structures), the development of carbon materials (carbon black, carbon nanotubes, carbon fiber, graphite oxide, reduced graphene oxide, and biomedical carbon), and the research progress of Ni-C composite materials (the composite material formed by nickel and carbon) are reviewed. The ultimate goal is to obtain absorbers with light weight, strong absorbing ability, and a wide frequency band. In particular, Ni-MXene, Ni-biomedical carbon, and Ni-multiphase carbon composites are the target direction for designing new and high efficiency EMW absorbers. Finally, the basic challenges and opportunities in this field are discussed.

Flexible PEBAX/graphene electromagnetic shielding composite films with a negative pressure effect of resistance for pressure sensors applications.

In the current work, we fabricated flexible poly(ether-block-amide) (PEBAX)/graphene composite films by a combination of facile melt blending and compression molding technique. The graphene content significantly affects the mechanical properties, electrical conductivity and electromagnetic interference (EMI) shielding performance. An electrically conductive percolation threshold of 1.75 vol% graphene was obtained in the PEBAX/graphene composites. With the introduction of 4.45 vol%, and 8.91 vol% graphene content, the average EMI SE of composite films could reach 16.6 and 30.7 dB, respectively. More interestingly, the PEBAX/graphene composite exhibited a nearly-linear negative pressure coefficient (NPC) effect of resistance with increasing outer pressure stimulation, which was attributed to the formation of more conductive pathways caused by the decreased distance between adjacent graphene. In addition, these composites demonstrated good sensing stability, recoverability and reproducibility after stabilization by cyclic pressure loading. The current study provides guidelines for the large-scale preparation of elastomer NPC sensors and smart EMI shielding devices.

Effect of Different Acid-Modified Coking Coals on Quinoline Adsorption.

The adsorption of quinoline from wastewater by coking coal (AC-1), HCl-modified coking coal (AC-2), HNO3-modified coking coal (AC-3), HF-modified coking coal (AC-4), and H2SO4-modified coking coals (AC-5) was investigated in this paper. The effects of acid-modified concentration, modification time, and adsorption time versus quinoline removal rate were studied by batch experiments. The quinoline concentration was measured by UV spectrophotometry, the average pore size and specific surface area of coking coal before and after modification were characterized through static nitrogen adsorption, the mineral composition of coking coal was tested by X-ray diffraction, the surface functional groups were tested by Fourier transform infrared spectroscopy, and the surface topography was tested using a scanning electron microscope. The experimental results showed that the adsorption capacity of coking coals was the best when both the modification time was 120 min and the acid-modified concentration was 0.1 mol·L-1 and the quinoline removal rate reaches the highest when the adsorption time was 120 min. The specific surface area of AC-2 increased from 2.898 to 3.637 m2·g-1, and the removal rate of quinoline increased from 77.64 to 90.61%. Acids reacted with inorganic mineral impurities within coking coal such as hydrogen vanadium phosphate hydrate, which caused an increase in the specific surface area. A new peak appeared in the Fourier transform infrared spectroscopy pattern at the wavenumber 2300 cm-1. The surface of coking coal modified by acids was rougher than that of AC-1. The adsorption capacity of coking coal was improved after modification, and modified coking coals have the highest potential as low-cost adsorbents for quinoline removal.

Adsorption of Methylene Blue on Bituminous Coal: Adsorption Mechanism and Molecular Simulation.

Coal with its complex porous medium and abundant oxygen functional groups could be used as an adsorbent to adsorb organic compounds. Adsorption experiments and molecular dynamics simulations were carried out to study the behavior of methylene blue (MB) on the surface of Wiser bituminous coal. The influence of adsorption through factors, such as pulverized coal dosage, adsorption reaction time, initial concentration, and temperature effect, was investigated. The removal efficiency of MB reached 96.5% under optimum reactive conditions. The adsorption equilibrium was accorded with a Langmuir isotherm adsorption equation. The adsorption of MB onto coal was a spontaneous process because the adsorption free energy ΔG 0 was negative. It was consistent with the conclusion of a negative interaction energy between bituminous coal and MB obtained by molecular dynamics simulation. Moreover, the density distribution along z-axis of each component molecule showed that MB molecules were adsorbed on the coal surface because of the polar interactions between the methyl groups of MB and the hydrophilic sites at the coal surface. Also, the diffusion degree of water molecule in liquid phase showed that as MB molecules formed hydrogen bonds with the water molecules, the activity of water molecules was restricted.

Study on the Interaction between Galena and Sphalerite During Grinding Based on the Migration of Surface Components.

In Pb-Zn ore flotation, unintentional activation of sphalerite often leads to difficult separation of Pb and Zn minerals, during which grinding plays a key role in unintentional activation. Therefore, the aim of this study was to evaluate the surface component changes of two different mineral particles and to propose the interaction between galena and sphalerite during mixed grinding using time-of-flight secondary ion mass spectrometry (ToF-SIMS). The results show that after mixed grinding of the galena and sphalerite, the Pb content on the sphalerite surface increased with the decrease of Zn and Fe contents on the sphalerite surface. The lead ions from galena were obviously absorbed onto the sphalerite surface, while the zinc and iron ions from sphalerite were not obviously migrated to the galena surface. Principal component analysis (PCA) of a dataset composed of 206 positive ion peaks of galena and sphalerite indicates that the surface components of galena and sphalerite migrated from either side to different degrees. This study successfully identified an important factor for unintentional activation of lead and zinc minerals during flotation: homogenization of surface components of different minerals during grinding.

A novel sponge-like 2D Ni/derivative heterostructure to strengthen microwave absorption performance.

One of the major hurdles of Ni-based microwave absorbing materials is the preparation of two-dimensional (2D) Ni flakes that can improve magnetic anisotropy to tune complex permeability. In this study, we successfully synthesized porous 2D sponge-like Ni/derivative heterostructures composed of Ni, NiO and Ni(OH)2 through a controllable hydrogen reduction method. Thanks to the larger grain size of the Ni/derivative heterostructure prepared at 600 °C (Ni-600) under hydrogen flow, good magnetic properties and high magnetic loss could be obtained, which is beneficial for the enhancement of microwave absorption properties. For the Ni-600 samples, the minimal reflection loss (RL) is -37.3 dB at 7.1 GHz and the effective bandwidth (RL < -10 dB, 90% microwave dissipation) could be tuned in the range of 4.5-18.0 GHz with the thickness of 1.5-4.5 mm. High attenuation ability, including dielectric loss and magnetic loss, and good impedance matching are the requirements for excellent microwave absorption properties. In addition, the porous 2D heterostructure flake structure also significantly contributes to microwave absorption. Multiple reflections and scattering caused by the porous flakes, interfacial polarizations in the heterostructures, tunable impedance matching in the porous structure, strong natural resonance induced by the 2D flakes and plentiful micro-capacitors in the separate flakes account for the enhanced microwave absorption performance. This study demonstrates a fresh exploration of designing novel electromagnetic wave absorbing materials.

Enhancing the microwave absorption properties of amorphous CoO nanosheet-coated Co (hexagonal and cubic phases) through interfacial polarizations.

Core-shell flower-like composites were successfully prepared by a simple polyol method. These composites were formed by coating dual-phased (face-centered cubic [fcc] and hexagonal close-packed [hcp]) Co with amorphous CoO nanosheets. The microwave absorption properties of the flower-like Co@CoO paraffin composites with various Co@CoO amounts were then investigated. Results showed that the paraffin-based composite containing 70wt% flower-like Co@CoO displayed excellent microwave absorption properties (RE=24.74dB·GHz/mm). The minimum reflection loss of -30.4dB was obtained at 16.1GHz with a small thickness of 1.5mm, and 1.5mm bandwidth reached 4.6GHz (13.4-18GHz) below -10dB (90% microwave absorption). The excellent microwave absorption properties of flower-like Co@CoO are attributed to the synergetic effect between magnetic loss and dielectric loss, and the magnetic loss makes a main contribution to absorption. The core-shell flower-like structures with dual Co phases also contributed to microwave absorption. The amorphous CoO nanosheets were able to generate multiple reflections and exhibit scattering. In addition, the novel absorption mechanism that enhanced interfacial polarization was proposed. This enhancement resulted from the presence of interfaces between the hcp and fcc phases and between the core-shell Co@CoO composites.

Enhanced sulfidation xanthate flotation of malachite using ammonium ions as activator.

In this study, ammonium ion was used to enhance the sulfidation flotation of malachite. The effect of ammonium ion on the sulfidation flotation of malachite was investigated using microflotation test, inductively coupled plasma (ICP) analysis, zeta potential measurements, and scanning electron microscope analysis (SEM). The results of microflotation test show that the addition of sodium sulfide and ammonium sulfate resulted in better sulfidation than the addition of sodium sulfide alone. The results of ICP analysis indicate that the dissolution of enhanced sulfurized malachite surface is significantly decreased. Zeta potential measurements indicate that a smaller isoelectric point value and a large number of copper-sulfide films formed on the malachite surface by enhancing sulfidation resulted in a large amount of sodium butyl xanthate absorbed onto the enhanced sulfurized malachite surface. EDS semi-quantitative analysis and XPS analysis show that malachite was easily sulfurized by sodium sulfide with ammonium ion. These results show that the addition of ammonium ion plays a significant role in the sulfidation of malachite and results in improved flotation performance.

Yolk-Shell Ni@SnO2 Composites with a Designable Interspace To Improve the Electromagnetic Wave Absorption Properties.

In this study, yolk-shell Ni@SnO2 composites with a designable interspace were successfully prepared by the simple acid etching hydrothermal method. The Ni@void@SnO2 composites were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. The results indicate that interspaces exist between the Ni cores and SnO2 shells. Moreover, the void can be adjusted by controlling the hydrothermal reaction time. The unique yolk-shell Ni@void@SnO2 composites show outstanding electromagnetic wave absorption properties. A minimum reflection loss (RLmin) of -50.2 dB was obtained at 17.4 GHz with absorber thickness of 1.5 mm. In addition, considering the absorber thickness, minimal reflection loss, and effective bandwidth, a novel method to judge the effective microwave absorption properties is proposed. On the basis of this method, the best microwave absorption properties were obtained with a 1.7 mm thick absorber layer (RLmin= -29.7 dB, bandwidth of 4.8 GHz). The outstanding electromagnetic wave absorption properties stem from the unique yolk-shell structure. These yolk-shell structures can tune the dielectric properties of the Ni@air@SnO2 composite to achieve good impedance matching. Moreover, the designable interspace can induce interfacial polarization, multiple reflections, and microwave plasma.

[Spectroscopic characterization of dissolubility and surface properties of chalcopyrite in aqueous solution].

The dissolubility and surface properties of chalcopyrite were studied in different mechanical stirring time and different pH value solution under argon and oxygen atmosphere by ICP-MS, AFM and XPS analysis. Besides, the XRD tern and crystal structure of chalcopyrite and its dissolution model in aqueous solution were established. The laboratory results indicate that the relationship between copper and iron concentrations in solution and time in pure water can be derived as the equation c = ks(a)t+b. The lower pH value makes it easier for chalcopyrite to dissolve, and that the surface oxidation is slow has minor effect on the dissolubility. In pure water, the dissolution of chalcopyrite has little influence on the effective specific surface area, and the dissolution is controlled by surface chemical reaction under acidic conditions. After long time dissolution, the surface of the chalcopyrite assumes copper-rich state relative to iron and the surface roughness and lattice imperfections increase.

[The general analytical methods for gases dissolved in liquids: sonoluminescence].

How to analyze the gases dissolved in water or organic liquids is a challenging problem in analytical chemistry. Till the present time, only the dissolved oxygen in water can be analyzed by chemical and instrumental methods, while other gases, e. g. CO2, N2, CH4, Ar, He, Ke, still can not be analyzed by chemical or instrumental methods. The present paper gives a review on using sonoluminescence for gas analysis in water or organic liquids.