Potassium Ethyl Xanthate Research Articles

Flotation Behavior of Arsenopyrite and Pyrite, and Their Selective Separation

This study investigated the effect of pH and pulp potential (EH) on the floatability of arsenopyrite and pyrite, which are single minerals, in Hallimond tube, by using xanthate as a collector. On this basis, the study further investigated the selectivity index of arsenopyrite and pyrite, using a mixed sample of arsenopyrite and pyrite. To examine the flotation behavior of each mineral by pH change, flotation was carried out at pH 4 and pH 10. The test results showed arsenopyrite had higher floatability at pH 4, regardless of the potassium ethyl xanthate (PEX) concentration. This is because xanthate ion was oxidized to be stable dixanthogen, which was well adsorbed onto arsenopyrite surface, due to the high EH of pulp. Meanwhile, arsenopyrite had relatively lower floatability at pH 10 than at pH 4, which was because the dixanthogen remained unstable, and was not adsorbed onto the arsenopyrite surface, due to the relatively low EH of pulp. Pyrite had low floatability at both pH 4 and pH 10. Just as for arsenopyrite, the result for pH 10 was caused by the low EH of pulp. Yet, interestingly enough, different from the case of arsenopyrite, pyrite at pH 4 had low floatability, despite its high EH. FTIR analysis was performed, to examine the reason for such contradictory behavior. The analysis result showed that this was caused by poor adsorption with xanthate, due to sulfate ion (SO4) that was generated by the oxidation of pyrite surface in reaction with oxygen in pulp at pH 4. To further investigate the selectivity index (i.e., the pyrite recovery/ arsenopyrite recovery ratio) of arsenopyrite and pyrite, additional flotation tests were carried out on mixed sample of the two minerals. Different from the flotation behavior of single minerals, the results showed that the recovery of arsenopyrite was lower than that of pyrite, and the selectivity index of arsenopyrite and pyrite was the highest when the PEX concentration was the lowest. Such a different trend in flotation behavior of the mixed sample from the flotation behavior of the single minerals was because the surface oxidation reaction of arsenopyrite, which was more affected by EH among the mixed arsenopyrite and pyrite, generated ferric arsenate, a hydrophilic compound, on the surface of arsenopyrite, resulting in poor adsorption with xanthate; in turn, this depressed the floatability of arsenopyrite. [doi:10.2320/matertrans.M2014369]

Conformational and spectroscopic study of xanthogen ethyl formates, ROC(S)SC(O)OCH2CH3. Isolation of CH3CH2OC(O)SH

ROC(S)SC(O)OCH2CH3, with R=CH3, (CH3)2CH and CH3(CH2)2, were obtained through the reaction between potassium xanthate salts, ROC(S)SK, and ethyl chloroformate, ClC(O)OCH2CH3. The liquid compounds were identified and characterized by 1H and 13C NMR and mass spectrometry. The conformations adopted by the molecules were studied by DFT methods. 6 conformers were theoretically predicted for R=CH3 and (CH3)2CH, while the conformational flexibility of the n-propyl substituent increases the total number of feasible rotamers to 21. For the three molecules, the conformers can be associated in 3 groups, being the most stable the AS forms – the CS double bond anti (A) with respect to the CS single bond and the SC single bond syn (S) with respect to the CO double bond – followed by AA and SS conformers. The vibrational spectra were interpreted in terms of the predicted conformational equilibrium, presenting the ν(CO) spectral region signals corresponding to the three groups of conformers. A moderated pre-resonance Raman enhancement of the ν(CS) vibrational mode of CH3(CH2)2OC(S)SC(O)OCH2CH3 was detected, when the excitation radiation approaches the energy of a n→π∗ electronic transition associated with the CS chromophore. UV–visible spectra in different solvents were measured and interpreted in terms of TD-DFT calculations. The unknown molecule CH3CH2OC(O)SH was isolated by the UV–visible photolysis of CH3OC(S)SC(O)OCH2CH3 isolated in Ar matrix, and also obtained as a side-product of the reaction between potassium xanthate salts, ROC(S)SK, and ethyl chloroformate, ClC(O)OCH2CH3.

Study of Solution Polymerization of Styrene in the Presence of Poly(ethylene glycol)-RAFT Agents Possessing Benzoyl Xanthate Derivatives

In this work, Macro-Reversible addition fragmentation termination (RAFT) agents based on poly(ethylene glycol) (PEG) possessing different molecular weights and bearing benzoyl xanthate moieties were synthesized by the reaction of PEG potassium xanthate salts with benzoyl chloride, 4-methyl benzoyl chloride and 4-chloro benzoyl chloride. Controlled free radical polymerization of the styrene were carried out in the presence of these macro-RAFT agents using 2,2′-azobisizsobutyronitrile (AIBN) as an initiator to yield PS-b-PEG-b-PS block copolymers. The linear kinetic plot ln [M]o/[M] vs. polymerization time indicated that was first order with reference to monomer concentration. The block copolymerization possessed controlled/living character. The controlled character of the RAFT polymerization of the styrene was confirmed by the formation of narrow polydispersity of the polymers, linear increases in the molecular weight with polymerization time and molecular weight of the products that agreed well with theoretical values. Polymers having relatively narrow molecular weight distributions and predetermined number average molecular weights were obtained by the RAFT polymerization of the styrene. However, molecular weights of the polymers deviated from the theoretical values when low molecular weight RAFT agents are used. The results indicate that PEG benzoyl xanthate RAFT agents can more efficiently control the polymerization comparing methyl or chlorobenzoyl derivatives. The block copolymers were characterized by spectroscopic and GPC methods.

Study of flotation conditions for cadmium(II) removal from aqueous solutions

Flotation conditions for cadmium(II) removal from aqueous solutions were investigated. Precipitate flotation techniques “of the first kind” (PFFK) and “of the second kind” (PFSK) were tested, using potassium ethyl xanthate (KEtX) as a precipitating agent for cadmium(II). The surfactants sodium dodecyl sulfate (SDS) and hexadecyltrimethylammonium bromide (HDTMA) were used as collectors for PFFK. The effects of KEtX and collector concentrations, induction time, bubbling time, solution pH and some foreign ions on cadmium(II) removal were studied. Under optimum conditions, cadmium(II) could be removed by PFFK by ∼93% and >99% using SDS and HDTMA, respectively. By PFSK, removal of about 64% for cadmium(II) was obtained. The two developed precipitate flotation methods were also tested for simultaneous removal of cadmium(II), nickel(II) and cobalt(II) from distilled water and tap water. The effectiveness of PFFK suggests its employment for metal-polluted wastewaters.

Synthesis and Characterization of the Novel Thermoresponsive Conjugates Based on Poly(3-hydroxy alkanoates)

Novel thermoresponsive polymer conjugates based on microbial polyesters and poly-N-isopropyl acryl amide, PNIPAM, have been reported. The unsaturated poly-3-hydroxy alkanoates, poly (3-hydroxy undecenoate), PHU, and 1:1 mixture of 10-undecenoic acid and soy oil acids, PHU-Sy, were brominated by using bromine in the dark, at room temperature. Brominated PHAs were transformed to macro reversible addition–fragmentation chain transfer (RAFT) agents via the substitution reaction with potassium ethyl xanthate. RAFT polymerization of N-isopropyl acryl amide, NIPAM, was initiated by the PHA-derivative containing xanthate pendant groups in order to obtain brush type PHA-g-PNIPAM thermo responsive amphiphilic graft copolymers. The water uptake of the PHU-g-PNIPAM and PHU-Sy-g-PNIPAM amphiphilic graft copolymers changed from 50 % to completely soluble in water. Structural and thermal characterization of the novel conjugates were carried out by using 1H NMR, GPC, DSC and TGA techniques.

Depressant function of high molecular weight polyacrylamide in the xanthate flotation of chalcopyrite and galena

A high molecular weight polyacrylamide (PAM) was tested as a potential selective depressant in the differential flotation separation of galena and chalcopyrite using potassium ethyl xanthate (KEX) as a collector. In single mineral flotation, PAM depressed chalcopyrite while galena was floatable. Adsorption mechanism study indicated that PAM could adsorb on galena through hydrogen bonding, and on chalcopyrite through hydrogen bonding as well as ammonium-copper complexation. KEX could only break up the galena-PAM bonding. Therefore the combined use of PAM and KEX rendered the flotation of the two minerals selective.In the flotation of mixtures of the two minerals, galena and chalcopyrite could be separated by PAM and KEX only after EDTA treatment of the mineral mixtures. Time of flight secondary ion mass spectrometric (ToF-SIMS) measurements indicated that when galena and chalcopyrite were present together in the suspension, PAM adsorbed on both galena and chalcopyrite. However, after prior treatment of the mineral mixtures by EDTA, PAM was found to mainly adsorb on chalcopyrite.

Removal of Zn(II) ions from aqueous solutions by ethyl xanthate impregnated activated carbons

A coconut shell based granular activated carbon (AC) was aged in solutions containing different amount of potassium ethyl xanthate (PEX) for 24h and then separated from the solutions, rinsed with distilled several times and used for Zn(II) ion removal. It was shown that the loading capacity of PEX impregnated AC at an initial Zn(II) concentration of 112mg/L slightly increased by increasing PEX preloading, so that it increases from 1.56 to 1.88mg/g by increasing the PEX concentration in the aging solution from zero to 200mg/L.Aging of AC in 0.1N sodium hydroxide solutions containing different amounts of PEX was also performed for 24h and it was shown that the loading capacity of the resultant AC samples for Zn(II) ions at an initial Zn(II) concentration of 112mg/L slightly increased by increasing PEX loading, so that it increases from 7.18 to 8.06mg/g by increasing PEX concentration in aging solution from zero to 600mg/L.Aging of nitric acid oxidized AC in 0.1N sodium hydroxide solutions containing different amounts of PEX also performed for 24h. It was shown that the loading capacity of these modified AC samples for Zn(II) ions at an initial Zn(II) concentration of 112mg/L increased by increasing PEX loading, so that it increases from 15.11 to 16.43mg/g by increasing PEX concentration in aging solution from zero to 1000mg/L.It was revealed that the impregnation of AC samples with PEX results in the decreasing of adsorption kinetics of Zn(II) ions, since the hydrophobic nature of PEX molecules retards solution diffusion onto PEX impregnated AC samples.In order to get the highest Zn(II) loading capacity, the optimum condition for surface modification was determined to be oxidizing of AC with 4M nitric acid solution and then aging in 0.1M sodium hydroxide solution containing 661mg/L PEX for 24h. These surface modified activated carbons were named ACABPEX. The effect of Zn(II) initial concentration in the range of 59 to 165mg/L on its adsorption kinetics and loading capacity onto ACABPEX was investigated. The equilibrium and kinetic data were best represented by the Koble–Corrigan isotherm model and the pseudo second order kinetic model, respectively. It was understood that three mechanisms play main roles in the adsorption of Zn(II) onto ACABPEX.

Electrochemical investigation of cold worked copper in alkaline solution with the presence of potassium ethyl xanthate

This paper presents the investigation results of the electrochemical behavior of copper in 1 M Na2CO3 solution in the presence of potassium ethyl xanthate (KEtX) with different concentrations. Tests were conducted on copper samples obtained without deformation and with deformation of 83, 91 and 99 %. Samples were obtained by cold drawing of wire, which was previously obtained by dip-forming procedure. Corrosion behavior of cold deformed copper wire is characterized by its open circuit potential and behavior during anodic polarization. Experiments were carried out in aqueous solution 1 M Na2CO3 with added various amounts of KEtX between 0.008 g/l and 0.15 g/l. It was experimentally proved that the degree of deformation between 83 and 99 % does not have a large effect on the open circuit potential, as well as on the behavior of copper during anodic polarization in 1 M Na2CO3. Voltammograms show no significant differences between peak heights obtained for different electrodes. The first peak which occurs at potential of around -0.06 V vs. SCE corresponds to the formation of copper oxide Cu2O. The second wide peak is at potential of around 0.15 V vs. SCE and corresponds to the formation of CuO. Addition of potassium ethyl xanthate in alkaline 1 M Na2CO3 solution changes the mechanism of the process in anodic part, which is reflected in the change of shape of voltammograms. In presence of KEtX in concentration between 0.008 g/l and 0.15 g/l on voltammograms a sharp peak appears at potential of about -0.2 V vs. SCE and corresponds to the oxidation of xanthate. Current density, which determines the rate of the process which takes place at the electrode surface, yet in the presence of smallest amounts of KEtX (<0,08 g/l) is higher than in the absence of KEtX. It allows one to conclude that the processes of oxidation of copper accelerate in presence of potassium ethyl xanthate.

Synthesis of Fluorescent Gold Nanodot–Liposome Hybrids for Detection of Phospholipase C and Its Inhibitor

We report the synthesis of fluorescent 11-mercaptoundecanoic acid-gold nanodot-liposome (11-MUA-Au ND/Lip) hybrids by incorporation of gold nanoparticles (∼3 nm) and 11-MUA molecules in hydrophobic phospholipid membranes that self-assemble to form small unilamellar vesicles. A simple and homogeneous fluorescence assay for phospholipase C (PLC) was developed on the basis of the fluorescence quenching of 11-MUA-Au ND/Lip hybrids in aqueous solution. The fluorescence of the 11-MUA-Au ND/Lip hybrids is quenched by oxygen (O2) molecules in solution, and quenching is reduced in the presence of PLC. PLC catalyzes the hydrolysis of phosphatidylcholine units from Lip to yield diacylglycerol (DAG) and phosphocholine (PC) products, leading to the decomposition of Lip. The diacylglycerol further interacts with 11-MUA-Au NDs via hydrophobic interactions, leading to inhibition of O2 quenching. The 11-MUA-Au ND/Lip probe provides a limit of detection (at a signal-to-noise ratio of 3) of 0.21 nM for PLC, with high selectivity over other proteins, enzymes, and phospholipases. We have validated the practicality of using this probe for the determination of PLC concentrations in breast cancer cells (MCF-7 and MDA-MB-231 cell lines) and nontumor cells (MCF-10A cell line), revealing that the PLC activity in the first two is at least 1.5-fold higher than that in the third. An inhibitor assay using 11-MUA-Au ND/Lip hybrids demonstrated that tricyclodecan-9-yl potassium xanthate (D609) inhibits PLC (10 nM) with an IC50 value of 3.81 ± 0.22 μM. This simple, sensitive, and selective approach holds great potential for detection of PLC in cancer cells and for the screening of anti-PLC drugs.

ChemInform Abstract: One‐Pot Synthesis of Disubstituted Imidazole Derivatives from α‐Azido Ketones Catalyzed by Potassium Ethylxanthate.

AbstractDimerization of aryl‐ or alkyl glyoxal imines generated in situ from α‐azido ketones in the presence of potassium ethylxanthate gives rise to new imidazole derivatives.

AFM surface force measurements conducted between gold surfaces treated in xanthate solutions

Surface forces have been measured in situ between gold surfaces hydrophobized by self-assembly of xanthates from aqueous solutions using an atomic force microscope (AFM). The measurements conducted in potassium amyl xanthate (KAX) and potassium ethyl xanthate (KEX) solutions showed long-range hydrophobic forces, with the force curves showing no evidence for nanobubbles on the surfaces. The strongest hydrophobic force was observed at contact angle above 90° and in pure water, with a decay length of 29.5nm. Both the contact angle and hydrophobic force increased with increasing xanthate concentration. At an excessively high concentration, the hydrophobic force diminished substantially. When the xanthate solution was replaced with pure water, however, a strong hydrophobic force reappeared, suggesting that the presence of residual xanthate ions in solution is detrimental to obtaining a strong and long-range hydrophobic force. This finding is consistent with the observation that hydrophobic force becomes weaker in the presence of NaCl in solution.

One-pot synthesis of disubstituted imidazole derivatives from α-azido ketones catalyzed by potassium ethylxanthate

An efficient, novel procedure for the synthesis of new imidazole derivatives from α-azido ketones is described. This reaction proceeds via dimerization of aryl glyoxal imino generated from α-azido ketones in the presence of potassium ethylxanthate as a catalyst. A possible mechanism for the entire sequence is proposed.

Copper and xanthate adsorption onto pyrite surfaces: Implications for mineral separation through flotation

The findings of synchrotron based spectromicroscopic investigations of Cu and xanthate adsorption onto pyrite surfaces are reported. Synchrotron based photoemission electron microscopy measurements have revealed that Cu adsorbs only onto specific surface sites on pyrite. The Cu 2p X-ray absorption near edge structure and position (2p3/2 peak at 934.3eV) confirms the presence of Cu+ with transitions from 2p to 4s states being apparent. Moreover, the peak position is typical of Cu+ bonded to S, Cu(I)S. This is confirmed by S 2p X-ray photoelectron spectroscopy with oxidised S2− species (S−), most likely resulting from electrochemical interaction of solution Cu2+ and surface S2− species, being observed. Fe 2p X-ray absorption spectroscopy shows that surface Fe does not take part in the Cu adsorption or subsequent restructuring processes.Synchrotron FTIR microscopy analysis of xanthate (potassium ethyl xanthate, KEX) adsorbed onto Cu activated surfaces also shows a heterogeneous distribution on pyrite. The use of a dilute (10−5M) KEX concentration shows Cu(I)–xanthate as the only surface xanthate containing species. This species may have formed through a chemical process involving previously adsorbed Cu+ and the xanthate from solution. When a greater (10−3M) concentration of KEX is used significant concentrations of Cu(I)–xanthate precipitate from solution onto the pyrite surfaces and cannot be easily removed. Under this condition, the predominant surface species remains Cu(I)–xanthate with smaller concentrations of diethyl dixanthogen also being present. The latter species may form in solution although some previous studies also suggest direct surface formation.

Effect of sulfide and petroleum aromatic concentrates on gold ore processing by flotation

The authors have analyzed applicability of butyl potassium xanthate coupled with sulfuraromatic concentrate, recovered from high sulfur diesel fraction of South Uzbekistan oil in two-stage extraction in the zinc chloride solution in N,N-dimethyl formamide, in flotation of gravity circuit tailings. The best performance has been reached at the ratio of the said concentrates as 2/1, which results in 12.2% reduction of gold loss in tailings, and, for another thing, the quality of the rougher sulfide flotation concentrate grows by 6 g/t.

Continuous removal of ore floatation reagents by an anaerobic–aerobic biological filter

A laboratory scale up-flow anaerobic–aerobic biological filter was constructed to treat synthetic ore floatation wastewater. Volcanic stone was applied as packing media for aerobic section. Biodegradation of some common ore floatation reagents as potassium ethyl xanthate dithiophosphate and turpentine were evaluated. An average COD reduction rate of 88.7% for potassium ethyl xanthate by the biofilter was obtained at HRT of 6h, air water flow ratio of 10:1 and pH of 7. Its effluent COD concentration varied between 17 and 43mg/L. Xanthates and dithiophosphate were found to be easily biodegradable, whereas turpentine was not favorable for microorganism to digest. The performance of the reactor fluctuated slightly within the temperature range of 10–35°C. Operation of the biofilter was sensitive to influent pH values. A neutral to weak basic influent was preferred for biofilter to maintain an efficient operation. Anaerobic treatment was able to enhance the biodegradability of influents significantly.

AFM force measurements between gold and silver surfaces treated in ethyl xanthate solutions: Effect of applied potentials

Many investigators measured surface forces between hydrophobic macroscopic surfaces using atomic force microscope (AFM). Some investigators observed long-range attractions and attributed them to the presence of hydrophobic forces, while others suggested that they are artifacts of the nano-bubbles and cavities associated with the hydrophobic surfaces. Still others suggested that the long-range attractions are due to the electrostatic interactions between charged patches present on opposing surfaces and hence are unrelated to surface hydrophobicity. In the present work, we have measured long-range attractions between gold- (or silver-) coated surfaces hydrophobized in potassium ethyl xanthate (KEX) solutions at pH 9.2 under controlled potential conditions. The results of our AFM force measurements are consistent with those of the contact angle and voltammetry experiments, indicating that the long-range attractions are hydrophobic forces.

Stabilization of Chromium(VI) from Chromic Slag with Two Types of Thiol Collectors

Two thiol collectors, sodium diethyldithiocarbamate (DDTC) and potassium ethyl xanthate (EXT), were adopted to stabilize hexavalent chromium from chromic slag. The average usage of each thiol collector is 62.5 μmol∙g-1 in chromic slag. The leaching characteristic of Cr6+ in chromic slag was analyzed according to the acidic extraction process with the toxicity characteristic leaching procedure (TCLP) and the procedures of extraction in water with the horizontal vibration method (HMV). Under the 0.1 mol∙L-1 TCLP and HMV conditions, we compared them with FeSO4 and found that two thiol collectors presented better stabilization effects for Chromium (VI) from chromic slag, especially the effect by DDTC is more stabilized than that by EXT. The rate of their stabilized treatments is 78.42% and 83.18%, respectively, which both are obviously higher than that by FeSO4. Heavy metal-thiol collectors such as flocculent mass is more stabilized under the neutral and alkalized conditions (pH>8), but it may be partly dissolved under the acidic conditions (pH<6) and the leaching amount of Cr6+ from chromic slag will increase quickly with pH decreasing.

Development of synthesis technology for the selective anxiolytic drug afobazole

The optimum synthetic scheme, methods of obtaining intermediates, and stage-by-stage analytical control techniques have been developed for industrial manufacturing of the new anxiolytic drug afobazole. According to the scheme, 2-nitro-p-phenethidine reduction by sodium dithionite is followed by cyclization of the diamine with potassium ethylxanthate. Alkylation of 2-mercapto-5-ethoxybenzimidazole with 4-(2-chloroethyl) morpholine was carried out. Thus, the technology for obtaining afobazole parent substance of pharmacopoeial quality is worked out.

Fouling effect of different flotation and dewatering reagents on activated carbon and sorption kinetics of gold

In carbon-in-pulp and carbon-in-leach circuits, among different organic and inorganic compounds present in the gold cyanide solution, flotation reagents play the main role in the fouling of activated carbon. In this study the effects of different types and variable concentrations of flotation and dewatering reagents on the kinetics of gold sorption onto granular activated carbon (GAC) were evaluated on the basis of kinetic rate constant (i.e., k value) of an empirical rate equation. The lower the k value, the greater is the fouling effect. It was observed that the k value rapidly decreases by increasing the concentration of collectors including potassium isobutyl xanthate (PIBX) and potassium ethyl xanthate (PEX) up to 20 mg/L and at higher concentrations, the k value gradually leveled off to 53 h − 1 for PIBX, which is 46% lower than the 99 h − 1 for PEX. At low concentrations (i.e., up to 15 mg/L) of methyl isobutyl carbinol, the k value gradually reduced and at higher concentrations, the decrease is found to be more pronounced. The fouling effect of flocculant was negligible and it would be even insignificant at high concentrations. The combinational effect of flotation reagents on the kinetic activity of GAC towards gold sorption was synergistically better. The cumulative adsorption of flotation reagents onto GAC in a continuous circuit within 28 days resulted in 40% decrease of k value, although it was still above admissible limit of 80–100 h − 1 .

Preparation and visible light photocatalytic activity of mesoporous N, S-codoped TiO2(B) nanobelts

The mesoporous N, S-codoped TiO2(B) nanobelts are synthesized via hydrothermal synthesis and post-treatment, and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption–desorption measurements (BET), X-ray photoelectron spectra (XPS), and UV–vis diffuse reflectance spectra (DRS). The results show that the prepared samples are mesoporous structured and exhibit stronger absorption in the visible light region with red shift in the absorption edge. The photocatalytic activity of N, S-codoped mesoporous TiO2(B) nanobelts is evaluated by the photocatalytic photodegradation of potassium ethyl xanthate (KEX) under visible light irradiation. It is found that the photocatalytic activity of the prepared samples increases with increasing the molar ratio of thiourea to Ti (R). At R=3, the photocatalytic activity of the N, S-codoped TiO2(B) sample TBLTS-3 reaches a maximum value. With further increasing R, the photocatalytic activity of the sample decreases. The high photocatalytic activity of N, S-codoped TiO2(B) nanobelts can be attributed to the balance between strong absorption in visible light region and low recombination rate of electron/hole pairs.