Facet-Dependent Charge Density of Serpentine: Nanoscopic Implications for Aggregation and Entrainment of Fine Particles.

Deciphering the facet-dependent surface properties of clay minerals holds vital significance in both fundamental research and practical engineering applications. To date, the anisotropic local charge density of serpentine surfaces still remains elusive, and thus, the interaction energies and associated aggregate structures between different crystal planes of serpentine cannot be quantitatively determined. In this work, different crystal planes of serpentine (i.e., SiO basal, MgOH basal, and edge) were selectively exposed, and their surface potentials and charge densities were determined using atomic force microscopy (AFM) force measurements coupled with Derjaguin-Landau-Verwey-Overbeek (DLVO) theory fitting. The SiO and edge planes consistently exhibited a permanently negative surface charge, whereas the point of zero charge (PZC) on the MgOH plane was estimated to be pH 9.0-11.0. Based on the interaction energy calculation between different serpentine planes, the aggregation structures of serpentine were predicted. Combined with scanning electron microscopy observation of freeze-dried samples, SiO-MgOH and MgOH-edge associations were found to dominate the aggregate structures at pH ≤ 9.0, thereby resulting in a stacking or "card-houses" structures. In contrast, all of the plane associations exhibited the repulsive interaction energy at pH 11.0, which led to a completely dispersed system, ultimately causing the most severe fine particle entrainment during froth flotation. Our work provides quantitative clarification of facet-dependent surface properties and aggregate structures of serpentine under different pH conditions, which will help improve the fundamental understanding of colloidal behaviors of clay minerals.

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.

Charge transfer mechanism through S-scheme heterojunction in in-situ synthesized TiO2/Fe-doped hydroxyapatite for improved photodegradation of xanthate.

The heterojunction structure of the photocatalyst composite, which necessitates a robust interface and sufficient contact areas, holds the key to obtaining high charge carrier migration efficiency. Here, a novel composite, TiO2 nanoparticles/Fe-doped hydroxyapatite (TONPs/FH_CS), is fabricated using a two-step synthetic technique, in which FH_CS is synthesized from artificial converter slag enriched with Fe and Ca. The unique nanorod@plate structure of FH_CS enables the uniform immobilization of TONPs onto FH_CS. Thereby, an n-n type heterojunction exhibits a highly intimate Ti-O-Fe heterointerface. Kelvin probe testing demonstrates the formation of an interfacial electric field oriented from FH_CS to TONPs, which serves as the driving force for interfacial electron transfer through the Ti-O-Fe channels. The photoacoustic signals provide information on electron trap levels and densities, indicating the formation of the electron transfer channels. •O2- and •OH species are responsible for being the active species in this system. A photoexcited carrier transfer pathway exhibiting an S-scheme mechanism with high separation efficiency significantly enhances the utilization of charge carriers in each phase. Thus, improved xanthate degradation has been achieved using a heterojunction containing a photocatalyst derived from industrial solid waste. This work demonstrates the significant potential of steel-making byproduct utilization in industrial wastewater treatment.

Attenuation of Palmitic Acid-Induced Intestinal Epithelial Barrier Dysfunction by 6-Shogaol in Caco-2 Cells: The Role of MiR-216a-5p/TLR4/NF-κB Axis.

Palmitic acid (PA) can lead to intestinal epithelial barrier dysfunction. In this study, the protective effects and working mechanisms of 6-shogaol against PA-induced intestinal barrier dysfunction were investigated in human intestinal epithelial Caco-2 cells. Transepithelial electrical resistance (TEER), paracellular flux, qRT-PCR, immunofluorescence, and Western blot experiments showed that the 24-h treatment with 400 µM PA damaged intestinal barrier integrity, as evidenced by a reduction of 48% in the TEER value, a 4.1-fold increase in the flux of fluorescein isothiocyanate-dextran 4000 (FD-4), and decreases in the mRNA and protein expression of tight junction (TJ)-associated proteins (claudin-1, occludin, and ZO-1), compared with the control. The PA treatment significantly (p < 0.05) increased the levels of pro-inflammatory cytokines (interleukin (IL)-6, IL-1ß, and tumor necrosis factor-alpha (TNF-α)) in Caco-2 cells due to the upregulation of toll-like receptor 4 (TLR4), myeloid differentiation factor 88 (MyD88), phosphorylated nuclear factor kappa-B (NF-κB) proteins, and downregulation of miR-216a-5p (which directly targeted TLR4). Co-treatment with PA and 6-shogaol (2.5 µM) significantly (p < 0.05) attenuated PA-induced changes through regulation of TJs via the miR-216a-5p/TLR4/NF-κB signaling pathway. This study provides insights into the functions and working mechanisms of 6-shogaol as a promising food-derived agent against PA-induced intestinal epithelial barrier dysfunction.

Preparation of Magnetic Metal-Organic Frameworks@Molecularly Imprinted Nanoparticles for Specific Extraction and Enrichment of Bisphenol A in Food.

Metal-organic frameworks (MOFs) with systematically tailored structures have been suggested as promising precursors to the preparation of diverse functional materials. Herein, a facile and versatile layer-by-layer strategy without any special surface modifications has been proposed for the preparation of magnetic metal-organic frameworks (MMOFs) supported molecularly imprinted polymer nanoparticles (MMOFs@MIP), which are based on a magnetically susceptible core conjugated with an imidazole-derived self-assembled layer and a silane-based imprinted shell. The obtained MMOFs@MIPs, which integrated the advantages of Fe3O4, MOFs, and MIPs, were characterized and exhibited good magnetic properties, a rapid mass transfer rate, and an excellent adsorption selectivity as well as capacity for the targeted molecular - bisphenol A (BPA). Moreover, the MMOFs@MIPs were employed as adsorbents in magnetic solid phase extraction (MSPE) to selectively bind and rapidly separate BPA from real samples with satisfactory recoveries ranging from 88.3% to 92.3%. More importantly, the desirable reusability of MMOFs@MIP was also evaluated, and the recoveries still maintained above 88.0% even after five re-use cycles. Furthermore, combined with high-performance liquid chromatography (HPLC) analysis, a novel MSPE-HPLC method was developed, enabling the highly selective and sensitive detection of BPA in a wide linear range of 0.5-5000 µg L-1 with a low limit of detection (LOD) of 0.1 µg L-1. This work contributes a promising method for constructing various functional nanoparticles @MOFs@MIP hybrid materials for applications in many different fields.

A preliminary study of aeolian sand-cement-modified gasification slag-paste backfill: Fluidity, microstructure, and leaching risks.

To realize low-cost green backfill mining, this paper proposes a novel model of aeolian sand-cement-modified gasification slag-paste backfill (ACGPB). This model realizes the safe disposal and resource utilization of hazardous solid wastes. A comprehensive experiment (including slump test, uniaxial compressive strength tests, microscopic test, and leaching toxicity tests) was conducted to explore how the mechanism of ACGPB depends on activator type and dosage. The results showed that fresh ACGPB slurry can be expressed by the Herschel-Bulkley model (R2 ≥ 0.965 in all recipes). With Na2SO4 as activator type, the yield stress, apparent viscosity, thixotropy, and slump of ACGPB slurry increased with increasing activator dosage. With CaO as activator type, the yield stress, apparent viscosity, thixotropy, and slump of ACGPB slurry fluctuated with increasing activator dosage. The mechanical properties of all recipes (not including Control group and C-C1) met the mechanical requirement (3 d ≥ 0.5 MPa and 28 d ≥ 1.0 MPa). In addition, the concentrations of all heavy metals remained within the range specified by the national standard. Specifically, the activator exerted a positive effect on the stabilization/solidification of heavy metal ions (Cu, Cd, Ba, Ni, Cr, Se, and As). Finally, FTIR, TG-DTG, SEM, and hydration heat were used to analyze the microstructure of ACGPB. The research results provide a creative way for the resource utilization of solid waste.

Apple phenolic extracts ameliorate lead-induced cognitive impairment and depression- and anxiety-like behavior in mice by abating oxidative stress, inflammation and apoptosis via the miR-22-3p/SIRT1 axis.

Lead can lead to neurotoxicity and cognitive impairment. In this study, for the first time, the protective effects and working mechanisms of apple phenolic extracts (APEs) against lead acetate (Pb(Ac)2)-induced cognitive impairment and depression- and anxiety-like behavior were examined in vivo. Forty male mice were administered daily (via gastric gavage; 8 weeks) with 0.9% normal saline (control), Pb(Ac)2 (20 ppm), APE (200 ppm) or Pb(Ac)2 (20 ppm) + APE (200 ppm). The APE contained five major phenolic compounds: chlorogenic acid, proanthocyanidin B2, epicatechin, phloridzin and phloretin. Behavioral tests, histopathological examinations and biochemical analyses revealed that Pb(Ac)2-treated mice exhibited cognitive and behavioral deficits (i.e. a reduced percentage of spontaneous alternation, prolonged duration of immobility and decreased open field test scores compared with the control. Pb(Ac)2 exposure significantly increased cellular oxidative damage and the levels of pro-inflammatory cytokines (interleukin (IL)-1ß, IL-6 and tumor necrosis factor-α (TNF-α), ionized calcium binding adaptor molecule 1 (Iba1) and pro-apoptotic proteins (caspase 3, caspase 9 and Bax), while downregulating the expression of Bcl-2 in the brain. APE administration alleviated these Pb(Ac)2-induced changes through regulating oxidative stress, neuroinflammation and apoptosis via the miR-22-3p/Sirtuin 1 (SIRT1) signaling pathway. Taken together, the APE has the potential to treat lead-induced neurotoxicity and neurodegenerative disorders via antioxidant, anti-inflammatory and anti-apoptotic actions.

AuNPs/NiFe-LDHs-assisted laser desorption/ionization mass spectrometry for efficient analysis of metronidazole and its metabolites in water samples.

Gold nanoparticles (AuNPs) have been widely used as laser desorption/ionization mass spectrometry (LDI-MS) nanomaterials for the analysis of low-molecular-weight samples. Nickel/iron-layered double hydroxides (NiFe-LDHs) nanosheets can support the anchoring of AuNPs and enhance the ability of desorption/ionization. Their hybrid nanocomposites are expected to produce synergistic effects to improve the performance of LDI-MS. In this work, a novel AuNPs/NiFe-LDHs nanomaterial was synthesized by self-assembly method and characterized based on TEM, SEM, XPS, UV-vis and FTIR-ATR. AuNPs/NiFe-LDHs assisted LDI-TOF MS exhibited higher peak intensity and lower background noise compared with conventional organic matrices. Furthermore, excellent salt and protein tolerance, good repeatability and quantification were observed when MNZ and its metabolites were detected in the range of 1-50 ng·µL-1 (R2 > 0.98), with LODs and LOQs of 0.5 ng·µL-1 and 1 ng·µL-1, respectively. This nanocomposite could also be used for the analysis of some other small molecules, such as antibiotics, sugars, amino acids and pesticides, demonstrating the potential to detect a variety of environmental chemicals. Taken together, the developed method combined the advantages of two nanomaterials and can provide rapid and accurate analysis of MNZ and its metabolites in water samples, as well as some other small molecules.

A review on rice yellowing: Physicochemical properties, affecting factors, and mechanism.

Yellowing is a critical issue that reduces quality and commodity value of rice. This article presents an overview on rice yellowing and the mechanism of rice yellowing was addressed as the emphasis. The change of physicochemical and nutritive properties in yellowed rice depends on the exposure temperature and time, as well as rice cultivar. The temperature and moisture on rice yellowing were dominant. There is no consensus on the relationship between microorganisms and rice yellowing. The occurrence of yellowing is mainly associated with heat stress induced by heaping heat or respiration of grain, and the yellowing is the collective result of primary and secondary metabolism. The upregulation of flavonoids is the direct cause of rice yellowing, which can be used as metabolic markers of rice yellowing. The Maillard reaction also contributes to yellowing during storage. Aeration and cooling are recommended to lessen the occurring of rice yellowing during commercial storage.

Revealing the Multi-Electron Reaction Mechanism of Na3 V2 O2 (PO4 )2 F Towards Improved Lithium Storage.

Na3 V2 O2 (PO4 )2 F (NVOPF) as an attractive electrode material has received much attention based on the one-electron reaction of V4+ /V5+ . However, the electrochemical reactions involving lower vanadium valences were not investigated till now. Herein, a composite of graphene decorated nanosheet-assembled NVOPF microflowers (NVOPF/G) was synthesized and the multi-electron reaction of NVOPF/G was conducted by controlling the operation voltage windows. The reaction mechanism, structural changes, and vanadium valences during the insertion/extraction of Li ions (from 2 to 6) were elucidated clearly by in-situ X-ray diffraction and ex-situ X-ray photoelectron spectroscopy. Theoretical computations also revealed the Li-ion locations in the structure of NaV2 O2 (PO4 )2 F. Due to the additional redox couple of V3+ /V4+ , NVOPF/G displayed a much higher initial capacity of 183.3 mAh g-1 in the wider voltage window of 1.0-4.8 V than that of 2.5-4.8 V (129.3 mAh g-1 ). Moreover, excellent Li-storage performance of NVOPF/G at a lower voltage (≤2.5 V) with the active reaction of V2+ /V3+ /V4+ was obtained for the first time, demonstrating the high potential of NVOPF/G as an anode material for Li ion storage.

A semi-covalent molecularly imprinted fluorescent sensor for highly specific recognition and optosensing of bisphenol A.

A novel mesoporous fluorescent molecularly imprinted sensor for selective detection of bisphenol A (BPA) in food materials was fabricated via a semi-covalent imprinting method. The imprinting precursor that served as an alternative template molecule for BPA was prepared via thermally reversible isocyanate bonding, which effectively improved the imprinting efficiency for the molecularly imprinted sensor. Carbon dots (CDs) were embedded in mesoporous silica as signal recognition elements that exhibited quenching upon BPA binding. Subsequently, through the sol-gel process, the molecularly imprinted layer was coated on the CDs silica layer and provided specific recognition sites for BPA. The composite of CDs embedded in the mesoporous molecularly imprinted polymer (CDs@MIP) was characterized with scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller measurements and thermogravimetric analysis. The mechanism of carbon dots quenching and the high selectivity of CDs@MIP towards BPA were explored. The linear response range of the sensor was from 0.025 mg L-1 to 2 mg L-1 with a limit of detection of 0.016 mg L-1. The method was successfully applied for the determination of food samples and recoveries ranged from 92.5% to 101.1%. The BPA contents in actual samples were determined using high performance liquid chromatography and the proposed sensor, showing no significant difference between the two methods.

Study of Microscopic Structure of Ceramic Materials Prepared from Nonmetallic Mineral Group Associated with Skarn-Type Gold Deposits.

The microscopic structure of ceramic bodies has an essential influence on their performance. In this study, a ceramic material was prepared by modifying a nonmetallic mineral group (J) associated with a skarn-type gold mine in Hubei. The nano and microsized structures of the fired ceramic bodies under different contents of nonmetallic mineral group (J) and varying temperature conditions were systematically observed and tested by scanning electron microscopy (SEM), Malvern laser particle size analysis, differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The J content affects the sintering and melt degree of the ceramic body, the contact mode of the particles inside the ceramic body and the pore structure. When the content of J is less than 70%, the performance parameters of the sintered body can meet the requirements of Group AII in the International Standard of Ceramic Tiles. It is concluded that the microscopic structure of the ceramic body is affected by the complex phase transition process including the dehydration, oxidation, melting and recrystallization of nonmetallic minerals during the firing process and is closely related to the properties of the ceramic body. It is feasible to improving the properties of ceramic bodies by adJusting the gradation parameters of J and increasing the proportion of fine grains under the same dosage. Considering the features of the ceramic body and J' utilization ratio, the optimum content of nonmetallic minerals associated with the skarn-type gold deposit in Hubei Province is 68-43%, and the optimum sintering temperature is approximately 1150 °C.

Ultrasensitive determination of sulfathiazole using a molecularly imprinted electrochemical sensor with CuS microflowers as an electron transfer probe and Au@COF for signal amplification.

In this work, a molecularly imprinted sensor employing copper sulfide (CuS) as a novel signal probe was successfully developed for ultrasensitive and selective determination of sulfathiazole (STZ). The reduction signals of Cu2+ produced in the process of electron transfer of CuS containing large amounts of Cu2+ are easy to be captured, which provide high electrochemical signals. Moreover, gold nanoparticles@covalent organic framework with excellent conductivity was introduced on the electrode surface for signal amplification and facilitating electron transfer processes of CuS. Under optimized testing conditions, the proposed sensor offered a linear DPV response to STZ over a very wide concentration range (1.0 × 10-4 to 1.0 × 10-11 mol L-1), with a limit of detection of 4.3 × 10-12 mol L-1. Fodder and mutton samples spiked with STZ were analyzed using this sensor, and the satisfactory recoveries ranging from 83.0% to 107.2% were obtained. In addition, the proposed sensor was used to determine the concentration of STZ in chicken liver and pork liver, with quantification results being near identical to those determined by high-performance liquid chromatography.

In Situ Adsorption of Mixed Anionic/Cationic Collectors in a Spodumene-Feldspar Flotation System: Implications for Collector Design.

Herein, we investigated the effects of mixed collectors with varying alkyl chain lengths and ligand types on the hydrophobicity of the spodumene-feldspar flotation system. Various collector-mineral interactions were compared using in situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy with two-dimensional correlation spectroscopy (2D-COS), in situ microcalorimetry, and X-ray photoelectron spectroscopy (XPS). The highest flotation separation performance can be achieved at a molar ratio of 6:1 and pH 8-9. The in situ microcalorimetry results revealed that the difference in the adsorption reaction heat of the mixed collector is larger than that of the single anionic collector. Moreover, the inconformity between the magnitude of adsorption reaction heat and the results observed for flotation recovery indicates that the heat of the reaction presumably involves the adsorption configurations of the collectors and the amounts adsorbed. In in situ ATR-FTIR with 2D-COS, it can be observed that octanohydroxamic acid/dodecylamine (OHA/DDA) is adsorbed much more intensely onto feldspar than onto spodumene due to the availability of more space on feldspar for the subsequent sorption of DDA after the prior bidentate chemisorption of OHA under alkaline conditions, whereas the sodium oleate (NaOL)/DDA adsorption sequence at pH 4-5 was the reverse of that at pH 8-9. Lastly, XPS was employed to provide further supplemental evidence for the bonding between these two minerals and single anionic/mixed collectors at the optimal pH of 8-9. In this study, the powerful in situ detection technologies can establish a new platform for exploring the underlying mechanism of new reagents at the solid-liquid interface. Moreover, the in-depth understanding related to the adsorption behavior of the mixed collector is beneficial for facilitating the selection and design of efficient and environmentally friendly flotation collectors with improved selectivity.

Noble Metal Nanostructured Materials for Chemical and Biosensing Systems.

Nanomaterials with unique physical and chemical properties have attracted extensive attention of scientific research and will play an increasingly important role in the future development of science and technology. With the gradual deepening of research, noble metal nanomaterials have been applied in the fields of new energy materials, photoelectric information storage, and nano-enhanced catalysis due to their unique optical, electrical and catalytic properties. Nanostructured materials formed by noble metal elements (Au, Ag, etc.) exhibit remarkable photoelectric properties, good stability and low biotoxicity, which received extensive attention in chemical and biological sensing field and achieved significant research progress. In this paper, the research on the synthesis, modification and sensing application of the existing noble metal nanomaterials is reviewed in detail, which provides a theoretical guidance for further research on the functional properties of such nanostructured materials and their applications of other nanofields.

Influence of ultrasound pre-treatment on ilmenite surface chemical properties and collectors' adsorption behaviour.

In this study, we used flotation tests, Fourier transform infrared spectroscopy (FTIR), zeta potential, X-ray photoelectron spectroscopy (XPS), and microcalorimetry measurements to investigate the flotation and possible adsorption mechanisms of the ilmenite surface before and after ultrasonic pre-treatment. Flotation results show that under optimum conditions, the promotion effect of sonication on ilmenite is remarkable. The maximum recovery is 89.54% for ultrasonicated ilmenite at a pH of 4-5. For pH of 8-9, recovery increased again to 66.34%. Microcalorimetry indicates that the adsorption-driven heat release (-Qads) is higher for ultrasonicated ilmenite than for raw one. After pre-treatment, the iso-electric point (IEP) changed from pH 6.2 to pH 4.2. FTIR spectra and zeta potential measurements indicated that metal ions as active sites on the ilmenite surface are probably changed by the ultrasonic treatment. XPS analysis shows that ultrasonic treatment can promotes the oxidation of Fe2+ to Fe3+ and improves the solubilization of Ca2+ and Mg2+ in the pH range of 4-5. Under weakly alkaline condition, ultrasound also can make Ca2+ and Mg2+ re-absorb onto the ilmenite surface as main active sites.

Anisotropic surface chemistry properties and adsorption behavior of silicate mineral crystals.

Anisotropic surface properties of minerals play an important role in a variety of fields. With a focus on the two most intensively investigated silicate minerals (i.e., phyllosilicate minerals and pegmatite aluminosilicate minerals), this review highlights the research on their anisotropic surface properties based on their crystal structures. Four surface features comprise the anisotropic surface chemistry of minerals: broken bonds, energy, wettability, and charge. Analysis of surface broken bond and energy anisotropy helps to explain the cleavage and growth properties of mineral crystals, and understanding surface wettability and charge anisotropy is critical to the analysis of minerals' solution behavior, such as their flotation performance and rheological properties. In a specific reaction, the anisotropic surface properties of minerals are reflected in the adsorption strengths of reagents on different mineral surfaces. Combined with the knowledge of mineral crushing and grinding, a thorough understanding of the anisotropic surface chemistry properties and the anisotropic adsorption behavior of minerals will lead to the development of effective relational models comprising their crystal structure, surface chemistry properties, and targeted reagent adsorption. Overall, such a comprehensive approach is expected to firmly establish the connection between selective cleavage of mineral crystals for desired surfaces and designing novel reagents selectively adsorbed on the mineral surfaces. As tools to characterize the anisotropic surface chemistry properties of minerals, DLVO theory, atomic force microscopy (AFM), and molecular dynamics (MD) simulations are also reviewed.

The flotation and adsorption of mixed collectors on oxide and silicate minerals.

The analysis of flotation and adsorption of mixed collectors on oxide and silicate minerals is of great importance for both industrial applications and theoretical research. Over the past years, significant progress has been achieved in understanding the adsorption of single collectors in micelles as well as at interfaces. By contrast, the self-assembly of mixed collectors at liquid/air and solid/liquid interfaces remains a developing area as a result of the complexity of the mixed systems involved and the limited availability of suitable analytical techniques. In this work, we systematically review the processes involved in the adsorption of mixed collectors onto micelles and at interface by examining four specific points, namely, theoretical background, factors that affect adsorption, analytical techniques, and self-assembly of mixed surfactants at the mineral/liquid interface. In the first part, the theoretical background of collector mixtures is introduced, together with several core solution theories, which are classified according to their application in the analysis of physicochemical properties of mixed collector systems. In the second part, we discuss the factors that can influence adsorption, including factors related to the structure of collectors and environmental conditions. We summarize their influence on the adsorption of mixed systems, with the objective to provide guidance on the progress achieved in this field to date. Advances in measurement techniques can greatly promote our understanding of adsorption processes. In the third part, therefore, modern techniques such as optical reflectometry, neutron scattering, neutron reflectometry, thermogravimetric analysis, fluorescence spectroscopy, ultrafiltration, atomic force microscopy, analytical ultracentrifugation, X-ray photoelectron spectroscopy, Vibrational Sum Frequency Generation Spectroscopy and molecular dynamics simulations are introduced in virtue of their application. Finally, focusing on oxide and silicate minerals, we review and summarize the flotation and adsorption of three most widely used mixed surfactant systems (anionic-cationic, anionic-nonionic, and cationic-nonionic) at the liquid/mineral interface in order to fully understand the self-assembly progress. In the end, the paper gives a brief future outlook of the possible development in the mixed surfactants.

New insights into the oleate flotation response of feldspar particles of different sizes: Anisotropic adsorption model.

The anisotropic adsorption of sodium oleate (NaOL) on feldspar surfaces was investigated to elucidate the different flotation properties of feldspar particles of four different size ranges. Microflotation experiments showed that the feldspar flotation recovery of particles with sizes spanning different ranges decreased in the order 0-19>19-38>45-75>38-45µm. Zeta potential and FTIR measurements showed that NaOL was chemically adsorbed on the Al sites of the feldspar surface. The anisotropic surface energies and broken bond densities estimated by density functional theory calculations showed that, although feldspar mostly exposed (010) and (001) surfaces, only the (001) surfaces contained the Al sites needed for NaOL adsorption. The interaction energies calculated by molecular dynamics simulations confirmed the more favorable NaOL adsorption on (001) than (010) surfaces, which may represent the main cause for the anisotropic NaOL adsorption on feldspar particles of different sizes. SEM measurements showed that the main exposed surfaces on coarse and fine feldspar particles were the side (010) and basal (001) ones, respectively. A higher fraction of Al-rich (001) surfaces is exposed on fine feldspar particles, resulting in better floatability compared with coarse particles. XPS and adsorption measurements confirmed that the Al content on the feldspar surface varied with the particle size, explaining the different NaOL flotation of feldspar particles of different sizes. Therefore, the present results suggest that coarsely ground ore should be used for the separation of feldspar gangue minerals. Further improvements in the flotation separation of feldspar from associated valuable minerals can be achieved through selective comminution or grinding processes favoring the exposure of (010) surfaces.

Effects of plant species richness on 13C assimilate partitioning in artificial grasslands of different established ages.

Artificial grasslands play a role in carbon storage on the Qinghai-Tibetan Plateau. The artificial grasslands exhibit decreased proportions of graminate and increased species richness with age. However, the effect of the graminate proportions and species richness on ecosystem C stocks in artificial grasslands have not been elucidated. We conducted an in situ13C pulse-labeling experiment in August 2012 using artificial grasslands that had been established for two years (2Y), five years (5Y), and twelve years (12Y). Each region was plowed fallow from severely degraded alpine meadow in the Qinghai-Tibetan Plateau. The 12Y grassland had moderate proportions of graminate and the highest species richness. This region showed more recovered 13C in soil and a longer mean residence time, which suggests species richness controls the ecosystem C stock. The loss rate of leaf-assimilated C of the graminate-dominant plant species Elymus nutans in artificial grasslands of different ages was lowest in the 12Y grassland, which also had the highest species richness. Thus the lower loss rate of leaf-assimilated C can be partially responsible for the larger ecosystem carbon stocks in the 12Y grassland. This finding is a novel mechanism for the effects of species richness on the increase in ecosystem functioning.