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• The flotation separation of fluorite from calcite and celestite was realized. • The optimum conditions for flotation separation were found. • The selective depression mechanism of the mixed depressant Al 2 (SO 4) 3 -AWG was discussed. To cope with the increase of sulfate gangue minerals in fluorite ores, flotation separation of fluorite from calcite and celestite using Al 2 (SO 4) 3 and acidified water glass (AWG) as mixture depressants was studied in this paper. The flotation separation performance and underlying mechanism were studied by flotation experiments, zeta potential measurements, microcalorimetric analysis, adsorption measurements, and X-ray photoelectron spectroscopy (XPS). The flotation results show that under optimum conditions, the inhibition effect of AWG on celestite is more remarkable with the assistance of Al 2 (SO 4) 3 , but has no obvious effect on the flotation of fluorite. Zeta potential measurements show that both positively charged Al species and negatively charged Si species are adsorbed on the surface of the minerals. Microcalorimetric analysis confirms that the interaction between Al 2 (SO 4) 3 and celestite is more intense than that of calcite and fluorite, while AWG is more likely to be adsorbed on the calcite surface. Adsorption measurements reVeal that there is competitive adsorption between the depressant and collector and that the adsorption of the depressant AWG prevents the collector NaOL from adsorbing on the surface of the minerals. The XPS results show that Al species and Si species are chemically adsorbed on the surface of the minerals and change the chemical surroundings of the elements on the mineral surface. Moreover, compared with fluorite, Al species can more clearly enhance the adsorption of Si species on the celestite surface. [ABSTRACT FROM AUTHOR]

The dissolved components of calcium-bearing gangue minerals will adsorb onto the celestite surface, which increases the difficulty of the flotation separation of celestite from fluorite and calcite. Single mineral and artificial mineral flotation experiments show that EDTA exhibits an excellent selective inhibition effect towards celestite and calcium-bearing minerals. Surface dissolution experiments reveal that EDTA can strongly inhibit the dissolution of calcium ions on the fluorite surface, thus reducing the influence of dissolved calcium ions on celestite flotation. Zeta potential experiments and adsorption experiments demonstrate that the amount of depressant EDTA adsorbed on the fluorite surface is greater than that on the celestite surface, which is contrary to the adsorption amount of collector sodium dodecyl sulfate (SDS) on the fluorite and celestite surfaces. Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses further reveal that, through chelating with calcium ions, EDTA can change the chemical surroundings of elements on the fluorite surface, while the chelation is not evident on the celestite surface. Based on the experimental and analytical results above, a possible model for the flotation separation process is created. Unlabelled Image • EDTA can selective inhibit the flotation of celestite and calcium bearing minerals. • EDTA can strongly inhibit the dissolution of calcium ions on the fluorite surface. • The adsorption of EDTA on the fluorite surface is greater than that of celestite. • EDTA can be adsorbed by chelating with calcium ions on the fluorite surface. [ABSTRACT FROM AUTHOR]

• The flotation separation of fluorite from celestite was achieved. • The optimum conditions for flotation separation were found. • The selective inhibition mechanism of SPS was discussed. Sulfate minerals have gradually become the main gangue minerals of fluorite deposits, and the flotation separation of fluorite and sulfate minerals is difficult with commonly used depressants. In this paper, the high selectivity of a novel depressant sodium polynaphthalene formaldehyde sulfonate (SPS) for the flotation separation of fluorite and celestite both in single mineral and artificial mixed ore experiments was studied, and the underlying separation mechanism was investigated by zeta potential measurement, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) analysis, and Atomic force microscopy (AFM) imaging analysis. Flotation results showed that, in the presence of sodium oleate (NaOL) and SPS, the flotation recovery difference between fluorite and celestite reached 76.26% and the grade of fluorite concentrates increased by 32.11% at pH 6.0. The analysis results showed that the adsorption of SPS on the fluorite surface was limited at pH 6.0, and the adsorption was most likely be through electrostatic interaction. For celestite, the adsorption of SPS on the surface significantly changed the chemical surrounding of celestite surface inhibiting the chemical adsorption of NaOL, and the chemical adsorption of SPS was more significant at pH 6.0. [ABSTRACT FROM AUTHOR]

By strong oxygen plasma treatment with 100 W on monolayer MoS2, we observe the disappearance of the Raman modes of MoS2. The phenomena of no MoO3 formation shown by Raman spectra and the appearance of the Mo6+ peak and decreased O concentration shown by X-ray photoelectron spectroscopy are attributed to that the state of MoS2 translates from crystal to amorphous after strong oxygen plasma treatment. The amorphization of monolayer MoS2 is further confirmed by the quenching of photoluminescence (PL) and the disappearance of two absorption peaks related to A, B exciton which demonstrates the disordered bandgap. Finally, we found that the amorphous MoS2 can improve the absorption fraction at the visible light (500 ~ 750 nm) which is potential for future visible light photocatalysis. [ABSTRACT FROM AUTHOR]

• BN@SiO 2 was successfully prepared by exfoliating h-BN and grafting SiO 2 onto its surface. • The presence of SiO 2 nanoparticles on the surface of BN@SiO 2 enhances its dispersion stability. • The composite coating, formulated with BN@SiO2 as a filler, demonstrates outstanding barrier properties, thermostability, and waterproofing performance, so it offers significant advantages in protecting mortar from carbonization and chloride attack. In order to improve the durability of cement-based materials, a composite epoxy coating with a newly synthetic BN@SiO 2 filler was developed using nanosilica (SiO 2) and hexagonal boron-nitride (h-BN). In this study, the BN@SiO 2 was synthesized through grafting SiO 2 nanoparticles onto surface of h-BN, while the BN@SiO 2 were verified by using Fourier transform infrared (FTIR) spectrum, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM) and transmission electron microscopy (TEM). Results showed that, the BN@SiO 2 as a filler can outperform the SiO 2 and h-BN for improving the thermostability and waterproofing performance of the coating. Three composite coatings prepared by SiO 2 , h-BN and developed BN@SiO 2 can effectively prevent mortar from carbonation and chloride attack, but the coating with BN@SiO 2 filler has more effectively performance than that with SiO 2 and h-BN fillers. After the mortar sample covered with BN@SiO 2 coating undergoes 180 days of chloride attack and 28 days of carbonization, its chloride penetration and carbonization depths were reduced by 50% and 64% compared to pure coating, respectively. In general, optimizing the properties of the filler can significantly enhance the barrier properties of coatings, which is beneficial for improving the durability of cement-based materials. [ABSTRACT FROM AUTHOR]

Zn-Co-S ball-in-ball hollow sphere (BHS) was successfully prepared by solvothermal sulfurization method. An efficient strategy to synthesize Zn-Co-S BHS consisted of multilevel structures by controlling the ionic exchange reaction was applied to obtain great performance electrode material. Carbon nanotubes (CNTs) as a conductive agent were uniformly introduced with Zn-Co-S BHS to form Zn-Co-S BHS/CNTs and expedited the considerable electrocatalytic behavior toward glucose electro-oxidation in alkaline medium. In this study, characterization with scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) was used for investigating the morphological and physical/chemical properties and further evaluating the feasibility of Zn-Co-S BHS/CNTs in non-enzymatic glucose sensing. Electrochemical methods (cyclic voltammetry (CV) and chronoamperometry (CA)) were performed to investigate the glucose sensing performance of Zn-Co-S BHS/CNTs. The synergistic effect of Faradaic redox couple species of Zn-Co-S BHS and unique conductive network of CNTs exhibited excellent electrochemical catalytic ability towards the glucose electro-oxidation, which revealed linear range from 5 to 100 μM with high sensitivity of 2734.4 μA mM−1 cm−2, excellent detection limit of 2.98 μM, and great selectivity in the presence of dopamine, uric acid, ascorbic acid, and fructose. Thus, Zn-Co-S BHS/CNTs would be expected to be a promising material for non-enzymatic glucose sensing. [ABSTRACT FROM AUTHOR]

Mutual interference is a severe issue that occurs during the electrochemical detection of heavy metal ions. This limitation presents a notable drawback for its high sensitivity to specific targets. Here, we present a high electrochemical sensitivity of ~237.1 μA cm-2 μM-1 toward copper(II) [Cu(II)] based on oxygen-deficient titanium dioxide (TiO2-x) nanosheets. We fully demonstrated an atomic-level relationship between electrochemical behaviors and the key factors, including the high-energy (001) facet percentage, oxygen vacancy concentration, surface -OH content, and charge carrier density, is fully demonstrated. These four factors were quantified using Raman, electron spin resonance, X-ray photoelectron spectroscopy spectra, and Mott-Schottky plots. In the mutual interference investigation, we selected cadmium(II) [Cd(II)] as the target ion because of the significant difference in its stripping potential (~700 mV). The results show that the Cd(II) can enhance the sensitivity of TiO2-x nanosheets toward Cu(II), exhibiting an electron-induced mutual interference effect, as demonstrated by Xray absorption fine structure spectra. [ABSTRACT FROM AUTHOR]

In the present study, sulfated derivatives of Artemisia sphaerocephala polysaccharide (SASP) with high degree of substitution (DS) were synthesized by using 4-dimethylaminopyridine (DMAP)/dimethylcyclohexylcarbodiimide (DCC) as catalyst in homogeneous conditions. It was found that DMAP/DCC showed marked improvement in DS of sulfated samples. Compared to sulfated derivatives without catalyst, the DS of SASP increased from 0.91 to 1.28 with an increment in dosage of DMAP from 0 to 10 mg. The influence of DMAP/DCC on the DS of sulfated derivatives was depended on the content of DMAP. The effect of DMAP might be due to its strong coordination to the hydroxy group. The results of FT-IR and X-ray photoelectron spectroscopy (XPS) indicated that SO 3 − group (S 6+ , binding energy of 172.3 eV) was widely present in sulfated polysaccharide molecules. 13 C NMR results indicated that C-6 substitution was predominant for sulfated polysaccharide when compared with other positions. In the sulfation reaction, a sharp decrease in M W was observed. DMAP/DCC was an effective catalyst system in sulfated modification of polysaccharide. [ABSTRACT FROM AUTHOR]

• Flotation separation of bastnaesite from fluorite and calcite is achieved. • Citric acid (H 3 Cit) is used as a selective depressant for fluorite and calcite. • H 3 Cit adsorbs spontaneously on the Ca–containing minerals surfaces. • Depression mechanism of H 3 Cit on the fluorite and calcite surfaces is investigated. Bastnaesite is a chief natural source of light rare earth elements (LREEs). The effective depression of Ca-containing minerals such as fluorite and calcite in bastnaesite flotation system is normally difficult, and it is imperative to exploit more environmentally-friendly depressants which can inhibit these gangue minerals simultaneously. Hence, we employ citric acid (H 3 Cit), a green, cheap and commonly available organic acid, to selectively depress the flotation of fluorite and calcite, and use octanohydroxamic acid (OHA) and sodium oleate (NaOL) with a molar ratio of 2:1 as mixed collectors. Micro-flotation results show that H 3 Cit decreases the recoveries of fluorite, calcite, and bastnaesite by 84.73%, 62.96%, and 9.23%, respectively at pH 8–9. The depression mechanism of H 3 Cit was investigated through zeta potential measurements, microcalorimetry measurements, solution chemistry and reaction thermodynamic analyses, and X-ray photoelectron spectroscopy (XPS) analyses. These further analyses at the minerals/water interfaces indicate that H 3 Cit preferentially adsorbs on the gangue mineral surfaces due to the positively charged fluorite and calcite surfaces which interact more easily with citrate ions (Cit3-), and the spontaneous interaction between Cit3- and Ca2+ on the surfaces. Accordingly, H 3 Cit is supposed to be a potential depressant for Ca-containing minerals in the flotation separation of bastnaesite. [ABSTRACT FROM AUTHOR]