Search

In the title compound, bis(2-methoxyethyl xanthato-κS)(N,N,N′,N′-tetramethylethylenediamine-κ2N,N′)zinc(II) acetone hemisolvate, [Zn(C4H7O2S2)2(C6H16N2)]·0.5C3H6O, the ZnII ion is coordinated by two N atoms of the N,N,N′,N′-tetramethylethylenediamine ligand and two S atoms from two 2-methoxyethyl xanthate ligands. The amine ligand is disordered over two orientations and was modelled with refined occupancies of 0.538 (6) and 0.462 (6). The molecular structure features two C—H...O and two C—H...S intramolecular interactions. In the crystal, molecules are linked by weak C—H...O and C—H...S hydrogen bonds, forming a three-dimensional supramolecular architecture. The molecular structure was optimized using density functional theory (DFT) at the B3LYP/6–311 G(d,p) level. The smallest HOMO–LUMO energy gap (3.19 eV) indicates the suitability of this crystal for optoelectronic applications. The molecular electrostatic potential (MEP) further identifies the positive, negative and neutral electrostatic potential regions of the molecules. Half a molecule of disordered acetone was removed with the solvent-mask procedure in OLEX2 [Dolomanov et al. (2009). J. Appl. Cryst. 42, 339–341] and this contribition is included in the formula.

In this study, flotation tests were conducted with purified pyrite and ore samples. The collectors employed were anionic and cationic type such as potassium ethlyl-amyl xanthate, Tomamine M73 and Resanol Bal. According to the flotation tests, it was found that pyrite floated at low pH and depressed at high pH values with xanthates. On the other hand, in the case of cationic collectors which are Tomamine M73 (alkyl ether amine, an amphoteric surfactant) and Resanol Bal (N-3-tridecyloxy propyl 1-3 diamine, branched acetate) pyrite floated at high pH values. It was shown that amine type collectors could be efficient to selectively float pyrite from chalcopyrite at alkali pH ranges in the case of ore samples. [ABSTRACT FROM AUTHOR]

Atomic force microscopy (AFM) has been applied to study the adsorption morphology of various collectors, i.e., potassium ethyl xanthate (KEX) and potassium amyl xanthate (PAX) and Cytec Aerofloat 238 (sodium dibutyl dithiophosphate), on chalcocite in situ in aqueous solutions. The AFM images show that all these collectors adsorb strongly on chalcocite. Xanthate adsorbs mainly in the form of insoluble cuprous xanthate (CuX), which binds strongly with the mineral surface without being removed by flushing with ethanol alcohol. This xanthate/chalcocite adsorption mechanism is very similar to the one obtained with the xanthate/bornite system; while it is different from the one of the xanthate/chalcopyrite systems, for which oily dixanthogen is the main adsorption product on chalcopyrite surface. On the other hand, dibutyl dithiophosphate adsorbs on chalcocite in the form of hydrophobic patches, which can be removed by rinsing with ethanol alcohol. AFM images show that the adsorption of collectors increases with increasing adsorption time and collectors’ concentration. In addition, increasing the solution pH to 10 does not prevent the adsorption of xanthate and Aerofloat 238 on chalcocite and the result is in line with the fact that chalcocite floats well in a wide pH range up to 12 with xanthate and dialkyl dithiophosphate being used as collectors. The blending collectors study shows that xanthate and dialkyl dithiophosphate can co-adsorb with both insoluble cuprous xanthate and oily Cu(DTP)2 (Cu dibutyl dithiophosphate) on a chalcocite surface. The present study helps to clarify the flotation mechanism of chalcocite in industry practice using xanthate and dialkyl dithiophosphate as collectors.

Removal of toxic metal ions using adsorbents is a well‐known strategy for water treatment. While chitosan and cellulose can adsorb weakly some types of metals, incorporating thiols as metal chelating agents can improve their sorption behaviors significantly. Presented in this review are the various chemical modification strategies applicable for thiolation of chitosan and cellulose in the forms of mercaptans, xanthates and dithiocarbamates. Moreover, much attention has been paid to the specific strategies for controlling the thiolation degree and characterization approaches for establishing the structure‐property relationship. Also, the kinetics and isotherm models that elucidate the adsorption processes and mechanisms induced by the thiomers have been explained. These thiomers have found great potentials in the applications associated with metal removal, metal recovery and metal detection. [ABSTRACT FROM AUTHOR]

Copper-cobalt oxide ores contain several minerals that are economically treatable by concentration techniques. The most used technique is froth flotation in which selective reagents are used to recover more valuables. It is, therefore, important to examine the optimal doses of those reagents while investigating the behaviors of minerals at the same time. This study explored the influence of lead nitrate Pb(NO3)2 on the froth flotation of oxide ore to increase valuable metals recoveries. Four factors were investigated including Pb(NO3)2 dosage, its conditioning, its addition dose in the 2nd fraction, and sulfidiser dosage. Other parameters were kept constant. The optimum was found at 25 g/t of Pb(NO3)2, conditioning together with sodium silicate (Na2SiO3) for 5 min, the addition of 5 g/t of Pb(NO3)2 in the 2nd fraction, and 3,000 g/t of sulfidiser. Recoveries in concentrates were 79.51 % Copper (Cu) and 60.27 % Cobalt (Co), with grades of 9.49 and 0.67 %, respectively. The conclusion was that the use of Pb(NO3)2 can considerably improve copper and cobalt recoveries. [ABSTRACT FROM AUTHOR]

• TiO 2 nanoparticles are effective for the preparation of xanthate sensors. • Optimization of modified carbon paste electrodes improves xanthate detection. • Background current subtraction is effective in improving xanthate detection. • Xanthate quantification is possible over a wide linear range in flotation samples. • Xanthate quantification is possible without collector interference. A voltammetric method for xanthate quantification was developed by fabricating a new electrode based on TiO 2 nanoparticles (TiO 2 NPs). The nanomaterial in the anatase phase was synthesized by a simple sol-gel method followed by a thermal treatment (9 h at 500 °C). The nanoparticles have a spheroidal morphology with an average size of 20.61 ± 6.01 nm. The band gap energy (3.7 eV) was determined by means of UV–visible spectroscopy from the absorption band at 335 nm. The TiO 2 based sensor was employed as working electrode (electroactive area: 0.02248 cm2) in a cyclic voltammetry study, and a greater peak current was observed for the electrooxidation of isopropyl xanthate at pH 10 as compared to the unmodified electrode. The electrode optimization showed that the percentage of TiO 2 and the amount of mineral oil in the electrode have a significant influence on the electrochemical response, with 18.4 % of TiO 2 NPs, 0.74 mL of mineral oil, and 18 h of electrode rest before the first use as optimal conditions. In the polarization studies, the charge transfer reaction occurred through a lower overpotential with respect to the open circuit potential. The exchange current density was three times higher for the modified electrode. Electrochemical impedance spectroscopy indicated the detection of xanthate with lower charge transfer resistance than when the unmodified electrode was used. The electrochemical sensor allows the quantification of xanthate from 5 μmol/L to 10 mmol/L by cyclic voltammetry and the square wave technique. For the cyclic voltammetry calibration, the limits of detection and quantification were 40.6 μmol/L and 135 μmol/L, respectively. The limit of detection by square wave voltammetry was 2.4 μmol/L, and the limit of quantification was 7.9 μmol/L. The repeatability of the method showed a relative dispersion of 3.1 % at 0.51 mmol/L. The electroanalytical response of the sensor was reproducible up to 30 days. The recoveries of xanthate in real flotation samples were 91.9 % and 94.6 % for concentrations of 0.55 and 1.1 mmol/L, respectively. No statistically significant differences were found between the quantification using the sensor and the UV spectrophotometric method. Dicresyl dithiophosphate showed statistically significant interference with the xanthate oxidation signal. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • The water-bridged self-assembly effectively reduced the release of volatiles. • The varied hydroxide content on mineral surfaces affects self-assembly. • Water bridge's existence confirmed by matching calculated and experimental spectra. • Water bridge makes TBOEX more firmly adsorbed on the chalcopyrite surface and arranged more closely. • TBOEX interacts with the d orbitals of copper on chalcopyrite (1 1 2) through π* orbitals and leads to the recovery of the Cu-S tetrahedron. Xanthate, a high-consumption functional surfactant, poses health and environmental risks due to the presence of volatile sulfides and pungent odors. In this study, we designed a novel ether group enhanced xanthate collector, O-(2-(tert -butoxy)ethyl) xanthate (TBOEX), which exhibits low odor and excellent flotation performance. The high matching between the calculated and the experimental infrared spectrum confirms the existence of water-bridged self-assembly behaviour. Odor evaluation results show that TBOEX reduced the content of volatile sulfur organic compounds and volatile hydrocarbons by 54.2% and 88.6%, respectively, compared to isobutyl xanthate (IBX), effectively reducing odor production. Flotation experiments and Zeta potential measurements demonstrate that TBOEX adsorbs densely on the surface of chalcopyrite, while the rich hydroxide on the surface of pyrite hinders the self-assembly of the collector, resulting in good selectivity for chalcopyrite. DFT calculations further reveal that TBOEX can form a stable and tightly arranged adsorption layer bridged by water molecules on the surface of chalcopyrite through two paths, and interact with d orbitals of copper atoms in the form of Cu-S tetrahedra through π* orbitals, finally improving the flotation recovery of chalcopyrite. The discovery of the water-bridge self-assembly mechanism and interfacial adsorption behavior of TBOEX is expected to drive the targeted design of collectors. [ABSTRACT FROM AUTHOR]

Estimation of xanthate decomposition percentage has a crucial role in the treatment of xanthate contaminated wastewaters and in the improvement of the flotation process performance. In this research, the modeling of xanthate decomposition percentage has been performed by least squares regression method and Adaptive Neuro-Fuzzy Inference System (ANFIS). A multi-variable regression equation and ANFIS models with various types and numbers of membership functions (MFs) are constructed, trained, and tested for the estimation of xanthate decomposition percentage. The statistical indices such as Root mean squared error (RMSE), Mean absolute percentage error (MAPE), and coefficient of determination (R2) are used to evaluate the performance of various models. The lowest values of RMSE and MAPE and the closest value of R2 to unity were determined for ANFIS model with triangular membership function and number of input MFs 9 9 9 (0.766906, 3.553509 and 0.998793). This indicates that ANFIS is a powerful method in the estimation of xanthate decomposition percentage. The performance of new-adopted ANFIS data modeling was significantly better than the conventional least squares regression method.

The degenerative transfer of xanthates to olefins is enabled by the iridium-based photocatalyst [Ir{dF(CF3)ppy}2(dtbbpy)](PF6) under blue LED light irradiation. Detailed mechanistic investigations through kinetics and photophysical studies revealed that the process operates under a radical chain mechanism, which is initiated through triplet-sensitization of xanthates by the long-lived triplet state of the iridium-based photocatalyst.

Cadmium dithiocarbamate and cadmium ethyl xanthate complexes were synthesized and characterized by microanalysis, Fourier transform infrared (FT-IR) spectroscopy and thermogravimetric analyses. The complexes were employed as molecular precursors for the fabrication of CdS nanoparticles in hexadecylamine (HDA) and oleylamine (OLA) at a temperature of 250 °C. Spherical and oval shaped particles with sizes ranging from 9.93 ± 1.89 to 16.74 ± 2.78 nm were obtained in OLA while spherical, oval and rod shaped particles with sizes ranging from 9.40 ± 1.65 to 29.90 ± 5.32 nm were obtained in HDA. Optical properties of the nanoparticles showed blue shifts as compared to the bulk CdS, with the OLA capped nanoparticles slightly more blue shifted than the corresponding HDA capped nanoparticles. Results of crystallinity patterns revealed hexagonal phase of CdS. [ABSTRACT FROM AUTHOR]

A protocol was described to access diverse isothiazoles with functionalization potential via transition metal‐free three‐component annulation of alkynones, potassium ethylxanthate (EtOCS2K) and ammonium iodide (NH4I). A sequential regioselective hydroamination/thiocarbonylation/intramolecular cyclization cascade achieved the efficient formation of consecutive C−N, C−S and N−S bonds in a one‐pot process. [ABSTRACT FROM AUTHOR]

Currently there is a wide variety of collectors used in mineral processing, the xanthates being the most used in sulfides flotation. Unfortunately, it is known that xanthates are not stable compounds and their decomposition generates carbon disulfide (CS2), a substance that is considered toxic. These aspects have motivated the search for collectors that exhibit superior performance without the health, safety and environmental (HSE) concerns associated with xanthates. In this study, the chemical stability of three xanthates of different alkyl groups (sodium ethyl xanthate (SEX), sodium isopropyl xanthate (SIPX) and potassium amyl xanthate (PAX)) was evaluated by UV/Vis spectroscopy, as a function of pH and time. Similarly, the chemical stability of three chelating collectors was evaluated: sodium di-isobutyl dithiophosphinate (SDIBDTPI), benzohydroxamic acid (BHA) and octanohydroxamic acid (OHA). Likewise, the surface tension of their aqueous solutions was measured making use of the Du Noüy method, to determine the critical micelle concentration (CMC). The results showed that the xanthate UV/Vis absorption spectra reflect the presence of a chemical reaction as the pH decreases from 4 to 2.5, which results in the formation of carbon disulfide (CS2). In addition, the generation of CS2 is favored as time elapses and the pH of the solutions decreases from 10 to 6, regardless of the hydrocarbon chain length. Conversely, dithiophosphinate and hydroxamic acids present greater chemical stability, although they form micelles at a certain concentration (CMC), a phenomenon that is not observed with xanthates. By not hydrolyzing, oxidizing, or decomposing into other chemical species, SDIBDTPI, BHA, and OHA may be considered environmentally friendly reagents. In the above context, it is important to promote the adoption of these collectors in mineral processing.

Thermodynamic and kinetic control of a chemical process is the key to access desired products and states. Changes are made when a desired product is not accessible; one may manipulate the reaction with additional reagents, catalysts and/or protecting groups. Here we report the use of carbon dioxide to accelerate cyanohydrin synthesis under neutral conditions with an insoluble cyanide source (KCN) without generating toxic HCN. Under inert atmosphere, the reaction is essentially not operative due to the unfavored equilibrium. The utility of CO2‐mediated selective cyanohydrin synthesis was further showcased by broadening Kiliani–Fischer synthesis under neutral conditions. This protocol offers an easy access to a variety of polyols, cyanohydrins, linear alkylnitriles, by simply starting from alkyl‐ and arylaldehydes, KCN and an atmospheric pressure of CO2. [ABSTRACT FROM AUTHOR]

To create more effective dialkyldithiophosphate collector for use in combination with potassium butyl xanthate in silver ore flotation (for Ducat deposit ores), the effect of a number of dialkyldithiophosphate collectors was studied depending on their surface-active properties and water-repelling ability. It was shown that their collecting ability, at rather similar water-repelling ability increases with strengthening their surface-active properties and reaches maximum at surface tension of 42–45.3 mN/m, and then begins to decrease. The water repellent ability decrease, even at their high surface-active properties, for example, for hydrolyzed samples, significantly reduces silver recovery. Taking into account the studied effect of surface activity and water repellent ability of the reagents, a more efficient dialkyldithiophosphate collector has been developed, which increases silver recovery compared to the standard reagent by 1.8–3.4% depending on ore dressability. Optimal ratio of the proposed dialkyldithiophosphate collector and xanthate dosing also contributes to increasing silver recovery with no reducing the process selectivity.

Lead is a toxic metal and its removal from industrial effluents is important. This can be done in several ways including ion dissolved air flotation (DAF). The advantages of the latter are multiple, among them speed, efficiency, low cost and space requirement. Tests were carried out with an aqueous synthetic wastewater of lead nitrate simulating the effluent of a producer of batteries. Xanthate was used as collector, a widely applied approach in ore processing. The variables studied were the size of the hydrocarbon chain of xanthate, xanthate concentration, pH, contact time, and foaming concentration. Quantification of residual lead was obtained by atomic adsorption. The proposed method revealed that dissolved air flotation is an efficient technique for the removal of lead ions, like the technique at the present is successful used in ore separation. It was observed that the pH and the amount of foaming did not have an effect. However, a solution of 20 mg L-1 of Pb could be reduced to 0.65 mg L-1, corresponding to a removal of 96.8% of the initial concentration.

Herein, it is reported that the stability of a halogenated perovskite (PVK) solar cell consisting of an fluorine‐doped tin oxide (FTO) substrate/TiO2/CH3NH3PbI3/N2,N2,N2′,N2′,N7,N7,N7′,N7′‐octakis(4‐methoxyphenyl)‐9,9′‐spirobi[9H‐fluorene]‐2,2′,7,7′‐tetramine/Ag/Au structure is improved by adding Sb‐xanthate to the PVK layer without large loss of efficiency. The Sb‐element‐rich layer is observed on top of the PVK layer. From the X‐ray photoelectron spectroscopy (XPS) study, it is concluded that an inorganic SbxOy passivation layer on the PVK layer is prepared by baking the solution of the Sb‐xanthate and the PVK precursor. The inorganic layer prevents moisture and oxygen from penetrating into the PVK layer. This article provides a new method to obtain a passivation layer on a PVK layer by baking a mixture solution in one step for improving solar cell stability. [ABSTRACT FROM AUTHOR]

Methyl xanthates of the type M(SSC‐OMe) (M = Li–Cs) are readily formed when carbon disulfide is reacted with the corresponding alkali metal hydroxides in methanol exposed to air, or with the alkali metal methoxides in dry methanol or THF under exclusion of air. The reactions are easily monitored by 13C NMR spectroscopy. The Na, K, Rb, and Cs salt could be isolated in high yields, while the Li salt decomposed upon attempted isolation. All compounds are readily complexed by crown ethers and form isolable 1:1 adducts, including the elusive Li salt. All products were studied by NMR (1H, 13C, and alkali metal nuclei) and IR spectroscopy, and most of them where structurally characterized by single‐crystal X‐ray diffraction. Li(SSC‐OMe)(12c4) (12c4 = [12]crown‐4) and Cs(SSC‐OMe)(18c6) (18c6 = [18]crown‐6) represent the first structurally characterized lithium and caesium xanthate complexes, respectively. [ABSTRACT FROM AUTHOR]

Cu2ZnSnS4 (CZTS) is a non-toxic and cheap photovoltaic absorber material, however, many challenges still remain for the successful fabrication of these devices. In this study, CZTS was deposited with CdS, a commonly used buffer layer, using different spray coating procedures (i.e., two-step, single-step and graded deposition techniques), to demonstrate a facile and rapid fabrication technique of creating CZTS:CdS photovoltaic devices. Scanning electron microscopy (SEM) was used to determine the morphology of the deposited films, showing that the two-step, single-step and the graded deposition with 2 s of overlap time produced clear and defined layers. However, when the overlap time exceeded 4 s the layer became less defined, thicker and less dense, resulting in failed photovoltaic devices. This was attributed to the additional source of air during the deposition period, resulting in air being trapped by the deposited precursor, which therefore forms more foam-like functional layers. X-ray diffraction (XRD) analysis reflected this change in morphology, with graded samples above 4 s displaying no obvious CZTS peaks, suggesting an ineffective decomposition route. Depositions using a two-step, single-step and the graded deposition technique with 2 s of overlap time were shown to form functional photovoltaic devices, with a 2 s graded overlap performing three times better than the ungraded samples, resulting in an improved power conversion efficiency of 0.41%. It is important to highlight that the device prepared with a 2 s graded interface significantly increased the current peak performance of CZTS photovoltaic devices deposited using xanthate precursors. [ABSTRACT FROM AUTHOR]

In the title compound, (2,2′-bi­pyridine-κ²N,N′)bis­(2-meth­oxy­ethyl xanthato-κS)zinc(II), [Zn(C4H7O2S2)2(C10H8N2)], the ZnII ion is coordinated to two N atoms of the 2,2′-bi­pyridine ligand and two S atoms from two 2-meth­oxy­ethyl xanthate ligands. The ZnII ion lies on a crystallographic twofold rotation axis and has distorted tetra­hedral coordination geometry. In the crystal, mol­ecules are linked by weak C—H· · ·O hydrogen bonds, forming supramolecular chains propagating along the a-axis direction. Weak intra­molecular C—H· · ·S hydrogen bonds are also observed. The inter­molecular contacts in the crystal were further analysed using Hirshfield surface analysis, which indicates that the most significant contacts are H· · ·H (36.3%), followed by S· · ·H/H· · ·S (24.7%), C· · ·H/H· · ·C (15.1%), O· · ·H/H· · ·O (14.4%), N· · ·H/H· · ·N (4.1%) and C· · ·C (2.9%). [ABSTRACT FROM AUTHOR]

Pinacolato boronates (Bpin) with an empty p‐orbital on boron stabilize an adjacent carbon radical, in contrast to diethanolamino boronates [B(DEA)] where the boron is sp3‐hybridized. By alternately placing a pinacol or diethanolamine moiety on the boron atom, thus stabilizing or not stabilizing the corresponding adjacent radical, it is possible to control the behavior of α‐boronyl xanthates and construct a large variety of terminal or internal boronates in a modular fashion. The remarkable tolerance of polar groups and the ability to introduce quaternary centers are particularly noteworthy features of this process. [ABSTRACT FROM AUTHOR]

In the title compound, bis­(2-meth­oxy­ethyl xanthato-κS)(N,N,N′,N′-tetra­methyl­-ethylenedi­amine-κ²N,N′)zinc(II) acetone hemisolvate, [Zn(C4H7O2S2)2(C6H16N2)]·0.5C3H6O, the ZnII ion is coordinated by two N atoms of the N,N,N′,N′-tetra­methyl­ethylenedi­amine ligand and two S atoms from two 2-meth­oxy­ethyl xanthate ligands. The amine ligand is disordered over two orientations and was modelled with refined occupancies of 0.538 (6) and 0.462 (6). The mol­ecular structure features two C—H∙∙∙O and two C—H∙∙∙S intra­molecular inter­actions. In the crystal, mol­ecules are linked by weak C—H∙∙∙O and C—H∙∙∙S hydrogen bonds, forming a three-dimensional supra­molecular architecture. The mol­ecular structure was optimized using density functional theory (DFT) at the B3LYP/6–311 G(d,p) level. The smallest HOMO–LUMO energy gap (3.19 eV) indicates the suitability of this crystal for optoelectronic applications. The mol­ecular electrostatic potential (MEP) further identifies the positive, negative and neutral electrostatic potential regions of the mol­ecules. Half a mol­ecule of disordered acetone was removed with the solvent-mask procedure in OLEX2. [ABSTRACT FROM AUTHOR]

[Display omitted] • Efficient flotation separation of malachite from calcite was obtained using high-dosage PX. • PX weakly interacted with the calcite surface via poor physical adsorption. • Copper xanthate was formed by the chemisorption of PX onto the malachite surface. • The selective flotation of malachite was attributed to the generated hydrophobic substance. • The long carbon chain of xanthate collector can be used in the oxidized mineral flotation. Calcite is a commonly associated gangue mineral in oxidized copper ore, while the flotation separation of oxidized copper ore from calcite is a bottleneck technology in the utilization of carbonate-type oxidized copper ore. The present study applied the pentyl xanthate (PX) as a collector to efficiently separate malachite and calcite without any other reagents. The flotation results indicate that the PX dosage is a key factor determining the flotation separation results of malachite and calcite. When its dosage reaches 1000 mg/L, the flotation recovery rate of malachite can reach 88.7 %, while calcite is less than 5 %. The flotation test of real ore contained these two minerals further confirmed that the malachite could be separated from calcite using PX as the collector. The mechanism and characterization analysis show that the selective substitution reaction between xanthate ions and OH ions on the malachite surface could generate hydrophobic substances of copper xanthate, which largely improves the hydrophobicity of the malachite surface. This study is expected to provide theoretical and practical assistance for the efficient flotation beneficiation of low-grade marble-type copper oxide ore. [ABSTRACT FROM AUTHOR]

As the most widely used flotation agent in mineral processing, xanthate in flotation wastewater causes significant damage to the environment and is a major obstacle to the construction of green mines. It is of great urgency to develop a low-cost, easy-to-separate and high-efficient adsorbent to remove xanthate from flotation wastewater. In this study, novel copper-based core-shell adsorbents with a large particle size are prepared by the hydrothermal crystallization-surface replacement method for xanthate removal. The as-prepared adsorbents were characterized by XRD, SEM-EDS, TEM, N 2 adsorption-desorption, FTIR, XPS analyses. Because of the larger specific surface area and higher Cu element content on surface, CuO-based adsorbent (CuA-2) possesses a higher adsorption capacity and faster adsorption rate of potassium ethyl xanthate (KEX) when compared with Cu 4 (NO 3) 2 (OH) 6 -based adsorbents (CuA-1). The removal percentage of 99% KEX can be obtained by adjusting dosage and the adsorption capacity is reduced by increasing solution pH due to the electrostatic repulsion. The maximum adsorption capacity of CuA-1 and CuA-2 are 645 and 1128 mg·g−1, respectively. The adsorption kinetic can be described by the pseudo-second-order model while the Langmuir adsorption isotherm is in good agreement with experimental results. EX- anion adsorbs and precipitates on the adsorbent in the form of flakes. A strong chemisorption of EX- anion occurs on the adsorbent surface, generating the Cu-xanthate complex. Moreover, the possible adsorption mechanism of KEX is proposed. The novel copper-based core-shell adsorbents show a promising application prospect in the treatment of flotation wastewater. [Display omitted] • Copper-based core-shell adsorbent is prepared by a surface replacement method. • The copper-based adsorbent displays excellent removal capacity for KEX. • The oxidation-reduction reaction between xanthate and Cu2+ occurs during adsorption. • Cupric and cuprous xanthates are main forms of Cu-xanthate complex on surface. [ABSTRACT FROM AUTHOR]

• N-type pyrite (e.g., pure, Co-, Au+ Co-, and Ni-bearing pyrite) is more noble and thus does not promote oxidation. • P-type pyrite (As-bearing pyrite) is the least noble and thus the most easily oxidized. • Low concentration of weakly polar metal impurities (e.g., Ni) promote xanthate oxidation to dixanthogen on pyrite surface. • Xanthate oxidation is not permitted on pyrite surface having either a strong polar metal (e.g., Co) or p-type inducing metalloids (e.g., As). • Xanthate collector shows the strongest interaction with p-type pyrite. Pyrite is an important mineralogical component of most sulphide ore deposit classes, where it commonly forms part of the gangue mineralogy, but may also represent an important ore mineral (i.e., auriferous pyrite). Effective and efficient separation of pyrite is thus a crucial step during most ore processing operations, and this is in part influenced by the pyrite mineral chemistry. Here, electrochemical measurements were used to study the reactivity of a series of well-characterised synthetic trace-element substituted pyrite samples under alkaline conditions relevant to industrial flotation. The presence of metals and metalloid impurities (As, Au, Co, and Ni) in pyrite were tested using rest potential measurements to infer oxidation and associated hydrophobicity. In the absence of any collector phases, pure- and Ni-substituted pyrite have the highest rest potential, followed by Co-substituted pyrite and couple-substituted (Co + Au) pyrite, whilst As-substituted pyrite has the lowest measured rest potential. Importantly, the degree of oxidation at the mineral surface correlates linearly with the concentration of each of the substituents, with the largest effect observed when As is the substituent. These results correspond to the semiconducting properties and noble character of each pyrite sample, with n-type pyrite (Au-, Co- and Ni-substituted) associated with noble character and high rest potential, whereas p-type As-substituted pyrite associated with least noble character and lowest rest potential. With the addition of a potassium amyl xanthate collector, the mineral chemistry further had an impact on the probability of dixanthogen formation. Increased substituent concentration in the pyrite lattice decreased the probability of dixanthogen formation, except in a sample where high Au (and moderate Co) was incorporated. These results highlight the importance of developing improved understanding of the impacts of substitution mechanisms on the surface reactivity and flotability of pyrite. Such an understanding will form the foundation for further improved (and engineered) approaches towards reagent design and mixture. This will serve to optimise separation of both gangue and valuable pyrite by using fundamental knowledge to target specific collector bands and flotation domains. [ABSTRACT FROM AUTHOR]

An atomic force microscope (AFM) was applied to study of the adsorption of xanthate on bornite surfaces in situ in aqueous solutions. AFM images showed that xanthate, i.e., potassium ethyl xanthate (KEX) and potassium amyl xanthate (PAX), adsorbed strongly on bornite, and the adsorbate bound strongly with the mineral surface without being removed by flushing with ethanol alcohol. The AFM images also showed that the adsorption increased with the increased collector concentration and contact time. Xanthate adsorbed on bornite in a similar manner when the solution pH changed to pH 10. The AFM force measurement results showed that the probe–substrate adhesion increased due to the adsorption of xanthate on bornite. The sharp “jump-in” and “jump-off” points on force curve suggest that the adsorbate is not “soft” in nature, ruling out the existence of dixanthogen, an oily substance. Finally, the ATR-FTIR (attenuated total reflection-Fourier-transform infrared) result confirms that the adsorbate on bornite in xanthate solutions is mainly in the form of insoluble cuprous xanthate (CuX) instead of dixanthogen. This xanthate/bornite adsorption mechanism is very similar to what is obtained with the xanthate/chalcocite system, while it is different from the xanthate/chalcopyrite system, for which oily dixanthogen is the main adsorption product on the chalcopyrite surface. The present study helps clarify the flotation mechanism of bornite in industry practice using xanthate as a collector.

Seven reported xanthate ligands and their new Fe(II) complexes of formulaNa[Fe(R-OCSS)3], where R is ethyl-, propyl-, butyl-, pentyl-, Hexyl-, heptyl- and octyl-xanthate have been synthesized. They have been characterized using elemental analysis, molar conductance, FT-IR, UV-Vis and 1H NMR spectroscopic techniques and melting-, decomposition-points for ligands and complexes respectively. All the ligands and their Fe(II) complexes have been evaluated for their antimicrobial activity against four gram-positive bacteria, four gram-negative bacteria and three fungi by agar disc diffusion technique. The MIC values of the compounds exhibited significant antifungal activity but showed lower antibacterial activity. The iron(II) complexes are found to possess higher antimicrobial activity than their counterpart ligands thus improving its antimicrobial efficacy. Hydrocarbon chain length of the ligands coordinated to Fe(II) centers seemed to be important for their antifungal as well as antibacterial activities.

By developing technologies, spent lithium-ion batteries (LIBs) are considered a great source of nickel-cobalt ions to fabricate metal sulfide nanoparticles. However, the presence of unnecessary ions such as manganese and lithium may hamper the formation of pure metal sulfide nanostructures where the utilization of proper ligand(s) can be very critical. For this reason, the present study initially introduces a promising and cost-effective acidic leaching followed by precipitation and thermal treatment (~250 °C, 1 h) processes to fabricate pure NiS nanopowders from the LIBs, while considering potassium amyl xanthate as the precipitating agent. The produced nanoparticle’s size and structure were characterized by commonly used and advanced analytical techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and photon correlation spectroscopy (PCS), and inductively coupled plasma optical emission spectrometry (ICP-OES). The elemental distributions and functional groups were analyzed through energy dispersive X-ray spectroscopy (EDS) and Fourier-transform infrared spectroscopy (FTIR) methods. The characteristic analyses of the spherical-like NiS particles showed a mean particle size of 61 ± 2 nm (by TEM) and 64 nm (through the PCS method) with high purities approved via XRD and EDS analyses. Moreover, comparing the obtained XRD data with the standard ones showed a perfect match with the hexagonal structure of the NiS phase. We finally concluded that such a presented approach is very practical and efficient for converting the LIBs to an extremely valuable product. Future studies are suggested for the fundamental conceptualization of the processes.

• A novel photoreactive chain transfer agent for RAFT/MADIX polymerization. • Well-defined macrophotoinitiators of PSt and PAN via RAFT/MADIX polymerization. • Diblock copolymers by photoinitiated free radical promoted cationic polymerization. An alternative approach for the synthesis of well-defined macrophotoinitiators of polystyrene and polyacrylonitrile with an end-chain photofunctional group via reversible addition-fragmentation chain transfer/macromolecular design via the interchange of xanthate (RAFT/MADIX) polymerization has been described. For this purpose, a novel photoreactive chain transfer agent (CTA-PI), namely S -benzyl O -(2-oxo-1,2-diphenylethyl) carbonodithioate, was prepared with an efficient one-pot, two-step synthesis by first reacting benzoin photoinitiator (PI) with CS 2 in the presence of NaH and then reacting this intermediate with benzyl bromide in THF. The structure of CTA-PI was determined by FT-IR, 1H NMR, and 13C NMR spectroscopy and confirmed by elemental analysis. Here, we used this xanthate based CTA in conjunction with 4,4′-azobis(4-cyanovaleric acid) (ACVA), as the initiating species, to investigate RAFT/MADIX polymerization of styrene (St), acrylonitrile (AN), methyl methacrylate (MMA), the so-called more activated monomers (MAMs), and vinyl acetate (VAc), one of the less activated monomers (LAMs). While RAFT/MADIX polymerization of styrene and acrylonitrile progressed in a controlled manner producing well-defined macrophotoinitiators with benzoin end-chain functional group, polymerization of methyl methacrylate proceeded uncontrollably. Polymerization of vinyl acetate under the same reaction conditions, on the other hand, did not occur at all. Spectroscopic and GPC measurements indicated that syntheses of polystyrene and polyacrylonitrile macrophotoinitiators bearing a photoreactive benzoin end group, PSt-PI and PAN-PI, respectively, with well-defined structures were achieved. These unique macrophotoinitiators were then used as prepolymers in photoinitiated free radical promoted cationic polymerization of cyclohexene oxide (CHO) and butyl vinyl ether (BVE) monomers to obtain PSt-PCHO, PSt-PBVE, PAN-PCHO, and PAN-PBVE di-block copolymers. [ABSTRACT FROM AUTHOR]

• The synthesis of a novel xanthate derivative (HEIBX) and its application in the separation of chalcopyrite from pyrite. • The molecular behaviour of HEIBX and SIBX were compared by DFT calculation. • Properties of HEIBX were compared with properties of another surfactant SIBX. • HEIBX exhibited superior collector ability and selectivity for chalcopyrite against pyrite than SIBX. • HEIBX chemisorbed on the surface of chalcopyrite by formation of Cu O and Cu S bonds. Separating chalcopyrite, an important copper-containing ore, from pyrite is an important mineral-processing objective. Herein, we report the synthesis of S -hydroxyethyl- O -isobutyl xanthate (HEIBX), a novel surfactant bearing both hydroxyl and thione groups, through the attachment of a hydroxyethyl group to sodium isobutyl xanthate (SIBX), and its first application as a flotation collector for the selective flotation-separation of chalcopyrite from pyrite. The flotation mechanism involving HEIBX and chalcopyrite or pyrite was investigated by DFT calculations, UV–vis spectroscopy, contact-angle and surface-tension measurements, flotation and zeta-potential experiments, as well as FTIR spectroscopy and XPS. Incorporation of the hydroxyethyl group was observed to increase the molecular properties of SIBX by increasing the number of active sites, arrangement density, selectivity and hydrophobicity, thereby improving its flotation performance. Chalcopyrite was separated from pyrite using 4 × 10−5 mol·L−1 HEIBX at pH ∼8.0. Furthermore, we found that the hydroxyl and thione functional groups adsorb onto the chalcopyrite surface though the formation of C O Cu and C S Cu bonds. [ABSTRACT FROM AUTHOR]

Xanthate is the most commonly used sulphide collector in the mining industry, however, its toxicological, ecological, and health and safety risks make alternative options increasingly attractive. In this study, two alternative collectors, one a mixture of dithiophosphate and mercaptobenzothiazole (DTP-MBT) and the other a mixture of dithiocarbamate and mercaptobenzothiazole (DTC-MBT), were tested for non-selective sulphide flotation. The adsorption of these collectors on pure pyrite surfaces was quantitatively and qualitatively characterized after conditioning at natural pH values (4–4.5) and alkaline pH values (10.5 using soda ash and lime). The adsorption of each collector was characterized through UV–vis spectrophotometry and direct surface observations using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The maximum amount of the three collectors adsorbed on pyrite surfaces was at least twice as great when conditioning was performed at natural pH values than at pH 10.5. Additionally, xanthate showed a greater affinity for pyrite surfaces than the DTP-MBT or DTC-MBT collectors. Surface characterizations showed that conditioning with collector resulted in the solubilization and modification of the oxidized species on pyrite surfaces. The nature of these superficial species and the collection mechanisms varied according to collector type, conditioning pH, and type of pH modifier used. At natural pH values, the vibrations detected in the spectra from the alternative collectors were mainly the C N H or N C S groups belonging to the 2-mercaptobenzothiazole compounds adsorbed on the pyrite surface, which could correspond to an iron mercaptobenzothiazole complex. At alkaline pH values, the main species characterizing the adsorption of these collectors on pyrite were difficult to identify because of their lower affinity for the pyrite surface. The only adsorption signature appearing on the pyrite surfaces at high concentrations was a C N H group of the MBT component; this also indicated the presence of a Fe-MBT complex on the pyrite surface. This study attempted to apply the above findings to the desulphurization of an ore from Goldex mine (Val-d'Or, Quebec). These tests were carried out with the three collectors at pH 6 (using sulphuric acid) and at pH 9.5 (using NaOH or CaO) in order to compare sulphur recoveries and sulphide cleaning in the final tailings. The desulphurization efficiencies of DTP-MBT at pH 9.5 were about 74.0% and 73.1% using NaOH and CaO, respectively. This was similar to the efficiency of xanthate (˜75%), but the alternative collectors showed slower flotation kinetics. In contrast, the performance of DTC-MBT was lower than for xanthate i.e., 69.9% with NaOH and 66.6% with CaO. For the three collectors, sulphide flotation at pH 6 was less efficient than at pH 9.5 (efficiency did not exceed 67% regardless of collector). According to the calculated acid-generation and neutralization potentials, none of the final desulphurized tailings should be considered as acid-generating. [ABSTRACT FROM AUTHOR]

I2‐catalyzed C(sp2)–H bond sulfenylation have been achieved from the reaction of thiols or disulfides with dihydropyrans under metal‐free conditions. This catalytic system was also used for thiol‐free achievement of sulfenylated dihydropyrans from aryl halides in the presence of CuI and potassium isopropyl xanthate as an effective source of sulfur. [ABSTRACT FROM AUTHOR]

In this paper, we describe a new simple and efficient synthetic protocol for the preparation of amphiphilic block copolymers on the basis of MPEG and PLA (MPEG- b -PLA). The proposed method consists of the preliminary modification of the terminal OH-group of MPEG using only carbon disulfide and KOH as reagents. It will be demonstrated that the resulting xanthate-functionalized MPEG (MPEGX) serves as a macro-initiator, thus allowing the ring-opening polymerization of D, l -lactide to be performed and the desirable block copolymers to be obtained in solvent-free and catalyst-free conditions. It will also be shown that this method is characterized by the lack of by-product (PLA) formation, which is almost unavoidable when traditional catalytic methods are applied. These circumstances, coupled with the low polydispersity (1.04) of the obtained product, demonstrate the precise control over a process realized under relatively soft conditions. Self-assembly of the purified copolymers into micelles and disassembly of the micelles caused by the degradation of the xanthate link is demonstrated using DLS measurements and GPC analysis, and peculiarities in the electronic structure of the xanthate derivatives responsible for the observed degradation effects are evaluated using DFT-based quantum chemical calculations. Xanthate functionalized MPEGs as new macro-initiators for the catalyst-, solvent-, and PLA-free controlled synthesis of core-shell forming amphiphilic block copolymers. Unlabelled Image [ABSTRACT FROM AUTHOR]

• Functional bis(γ-thiolactone) synthesis from xanthate radical chemistry. • Two routes involving addition to an alkene, thermolysis and thiolactonization steps. • Incorporation of phosphonate, hydroxy, bromide or boronate functionalities. A new methodology for the synthesis of bis(γ-thiolactones) including two different routes was developed. Both strategies are based on xanthate-mediated synthesis involving free radical addition to an unsaturated compound followed by thermolysis and thiolactonization steps. The first approach is based on the addition of a xanthate to different dienes whereas the second one uses the addition of a bis(xanthate) to various functional alkenes. These two different pathways led to a series of bis(γ-thiolactones) bearing phosphonated, hydroxy, bromide or boronate groups. This shows great promise for broader access to functional bis(γ-thiolactones) which can be envisioned as high potential building blocks for step-growth polymerization. [ABSTRACT FROM AUTHOR]

The reaction of NiCl2·6H2O or Zn(CH3CO2)·2H2O with potassium O-propylxanthate (KS2COC3H7) and N, N, N′,N′-tetramethylethylenediamine (tmeda) affords monomeric complexes of the formula [M(S2COC3H7)2(tmeda)] (M = Ni(II) 1; Zn(II) 2). Both complexes are characterized by single crystal X-ray diffraction, elemental analysis, IR spectroscopy. Complexes 1 and 2 crystalize in monoclinic P21/c and I2/a space groups, respectively. Each metal center is ligated by four S atoms from xanthate ligands and two N atoms from tmeda in a distorted octahedral geometry. [ABSTRACT FROM AUTHOR]

Microwave-assisted tertiary carbon radical reaction was developed. The reaction of tertiary xanthates with electron deficient alkenes was prompted by microwave irradiation, and various coupling products possessing quaternary carbon centers were obtained in good yields. The reaction was conducted under simple and common radical condition except for microwave irradiation, and the reaction completed within 5min. [ABSTRACT FROM AUTHOR]

Heavy metal lead poses a great threat to organisms and the environment; the removal of lead has drawn more and more attention in recent years. In this paper, the sulfur-containing functional group was grafted onto the walnut shell with xanthate to synthesize a low-cost biosorbent (SWM) for the removal of lead in water. The synthesized adsorbent was characterized by Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and Brunner−Emmet−Teller (BET). The effects of pH, adsorbent dosage, contact time, initial Pb (II) concentration, and temperature on adsorption were investigated, and the adsorption properties of walnut shells before and after modification were compared. Moreover, adsorption kinetics, adsorption isotherms, and adsorption thermodynamics were studied. The sulfur-containing functional group was confirmed to be successfully grafted onto the walnut shell. The results showed that the adsorption performance of SWM was much better than the unmodified walnut shell due to complexation by sulfur-containing functional group and ion exchange. The Pb (II) adsorption onto SWM was found to follow Temkin isotherm model and has a good correlation with the pseudo-second-order kinetic model. In addition, the adsorption process was spontaneous and exothermic. All the results showed that the high adsorption performance and low cost of SWM make it a potential biosorbent in the treatment of lead-contaminated water. [ABSTRACT FROM AUTHOR]

Graphical abstract Surface sulphidization was achieved by an initial adsorption of xanthate on the lead oxide surface followed by the thermolysis of xanthate coated metal oxides. Highlights • Thermolysis of xanthate coated lead oxides can lead to the surface sulphidization. • The mechanism of surface sulphidization depends on redox properties of samples. • Xanthate can be strongly adsorbed at the surface of PbS, S@PbO and PbO. • The desorption order of xanthate is PbO > S@PbO > PbS with increasing solution pH. Abstract In this study, ultra-fine lead oxide, lead carbonate and lead hydroxyl carbonate particles were synthesized and modified by a surface sulphidization route to form a sulphide surface layer which is interesting in electronic and optoelectronic device as well as vacuum tribological applications. All the samples were characterized using XRD and nitrogen adsorption/desorption techniques to obtain information on the crystal structure and the specific surface area of the samples. The surface physical-chemical properties of the samples were studied by potentiometric titration, adsorption of xanthate, and measurements of contact angles and zeta potentials. The sulphidization mechanisms of xanthate for various lead oxide samples were also discussed. [ABSTRACT FROM AUTHOR]

Highlights • Be CuFe 2 O 4 and Be MnFe 2 O 4 were used for removal of xanthate from solution. • At optimum conditions more than 94% of the residual xanthate was removed. • The adsorption kinetics, isotherm and thermodynamics studies were conducted. • The adsorbents were successfully removed xanthate from the real samples. Abstract The residual organic reagents (including xanthates) in the flotation tailings can cause environmental issues during their disposal, besides their deleterious influence on the flotation performance during recycling. In this study, the adsorption characteristics of bentonite modified with copper and manganese ferrite nanoparticles (Be CuFe 2 O 4 , Be MnFe 2 O 4) for xanthate removal from the synthetic and real solutions was studied. The characterization studies by XRF, XRD, BET, SEM, EDX, VSM and FTIR techniques confirmed the formation of magnetic nanoparticles. The adsorption capacity of Be CuFe 2 O 4 was found to be higher than Be MnFe 2 O 4 and at optimum conditions (adsorbent dosage: 4 mg/mL; xanthate concentration: 1000 mg/L; pH = 9.2; time = 40 min) more than 94% of the residual xanthate was removed by this adsorbent. The kinetic studies showed that rate of xanthate adsorption on both adsorbents followed the pseudo-second order model. The intraparticle diffusion was not the only rate-limiting step of the adsorption process. The equilibrium isotherms were best fitted to the Langmuir model. This suggests monolayer adsorption of xanthate on homogenous sites of the adsorbents. The thermodynamic studies revealed that the adsorption process was spontaneous, endothermic and entropy-driven. The synthesized adsorbents were capable of completely removing xanthate from the actual samples taken from the tailings of a copper flotation plant (Qaleh-Zari, Iran). [ABSTRACT FROM AUTHOR]

Abstract The structure and spectroscopic properties of nickel methylxanthate, Ni(S 2 COCH 3) 2 , as isolated molecule and in crystalline phase, were investigated both experimentally and theoretically. Experimentally, single crystal X-ray diffraction, infrared and ultraviolet–visible spectroscopies have been used, while the applied theoretical approaches include density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations. The isolated molecule of the complex under study was found to exist in two nearly degenerated conformers (cis and trans , with the methyl groups of the ligand molecules positioned the same side or in opposite sides of the molecule, respectively). The trans conformer is selected upon crystallization. The crystal structure (at 100 K) was solved and discussed, with emphasis given to the characterization of the main intermolecular interactions. The infrared spectrum (in the 3500-300 cm−1 range) of the crystalline material was assigned in details, also taking into account the results of the normal coordinate analysis performed for the isolated molecule, which in turn was made using the data resulting from the DFT calculations. The UV–visible spectrum of the compound in CHCl 3 solution was also obtained and interpreted based on results of TD-DFT calculations, demonstrating the importance of the metal to ligand charge transfer in the studied complex. Finally, the catalytic activity of the complex for ring-opening reaction of styrene oxide resulting from nucleophilic attack of anilines was also evaluated, showing that the compound presents potential as catalyzer of this type of reactions. Graphical abstract Image Highlights • The isolated molecule of Ni(S 2 COCH 3) 2 exists in two nearly degenerated conformers, cis and trans. • The trans conformer is selected upon crystallization. • TD-DFT calculations, demonstrated the importance of the metal to ligand charge transfer in the complex. • The catalytic activity of the complex for ring-opening reaction of styrene oxide with anilines was evaluated. [ABSTRACT FROM AUTHOR]