Adsorption Of Ethyl Xanthate Research Articles

Synergistic adsorption of ethyl xanthate and butyl xanthate on pyrite surfaces: A DFT study

AbstractPyrite is the most widely distributed sulfide mineral with a wide range of uses, and pyrite is mainly recovered by means of flotation in practical production, and the commonly used flotation collectors are mainly xanthates with good flotation performance. The adsorption behavior of commonly used collectors ethyl xanthate and butyl xanthate on the surface of pyrite is investigated by using the density functional tight bounding theory (DFTB). The results show that when a single reagent acts on the pyrite surface, butyl xanthate has a stronger effect than ethyl xanthate, and the adsorbed mineral surface shows obvious hydrophobicity. The interaction between ethyl xanthate and butyl xanthate had a stronger effect than that of a single reagent, and the simulation of the flotation environment at ordinary temperature using molecular dynamics revealed that the synergistic adsorption of the two different reagents on the surface of pyrite was more hydrophobic, that is, the synergistic adsorption of the combined collector of ethyl xanthate and butyl xanthate on the surface of pyrite was stronger. The results of the study are of great significance for the synergistic effect between the combined collector and the mineral.

Ethyl xanthate adsorption on different surfaces of jamesonite: A DFT study

Adsorption of ethyl xanthate (EX) on jamesonite surfaces with exposing Pb, Fe and Sb (M1), Sb and Pb (M2) and Pb and Fe (M3) was investigated by DFT method. Adsorption energy of EX on M3 is the largest, −236.51 kJ/mol; and then M2, −189.62 kJ/mol; and M1, −65.84 kJ/mol in order. For EX adsorption on M1 surface, S1 and S2 of EX are bonded to Fe1 and Sb1 of jamesonite surface, respectively. However, high spin distribution of d-electrons of Fe2+ leads to the weak interaction between Fe1 and S1. Despite the high polarization rate of Sb3+, the interaction of Sb1 of M1 with S2 of EX is weak, which may be due to the coordination structure of Sb (3-coordination) and structure change of EX. Two sulfur atoms (S1 and S2) of EX are simultaneously bonded to Sb1 (2-coordination) of M2 surface for EX adsorption on M2, leading to the stronger interaction between EX and M2 than that between EX and M1. As for EX adsorption on M3, only S1–Pb1 bond is formed, but the far larger polarization rate of Pb2+ than Sb3+ leads to the stronger interaction between EX and M3 than that between EX and M2.

Selective Separation of Chalcopyrite from Pyrite Using Sodium Humate: Flotation Behavior and Adsorption Mechanism.

Flotation separation of chalcopyrite from pyrite using lime or cyanides as depressants results in serious problems, such as the blockage of pipelines and environmental pollution. Eco-friendly organics are a future trend for beneficiation plants. In this research, the eco-friendly organic depressant sodium humate (SH) was chosen as a depressant to separate chalcopyrite from pyrite by flotation. The results indicated that SH could selectively depress pyrite owing to the oxidation species (FeOOH, Fe2(SO4)3) on its surface. The oxidation species were the adsorption sites for the COO- in the SH structure and impeded the subsequent collector potassium ethyl xanthate (KEX) adsorption. However, chalcopyrite was slightly oxidized with fewer oxidation species for SH adsorption, and KEX could be adsorbed and functioned effectively. This research suggested that SH could be an effective and eco-friendly depressant in chalcopyrite-pyrite flotation separation, which had potential use in the industry.

Trifunctional mesoporous magnetic adsorbent-photocatalyst nanocomposite for efficient removal of potassium ethyl xanthate from mining wastewater

Xanthates are largely used in the mining industry as mineral flotation agents, causing serious environmental problems, and therefore, removing them effectively is a significant barrier for sustainable green mining that needs to be addressed. Here, nanostructured mesoporous CoFe2O4/Co3Fe7@carbon prepared by clean and facile mechanochemical-molten salt process is employed as a trifunctional magnetic adsorbent-photocatalyst agent (M-APh) for the efficient adsorption of potassium ethyl xanthate (KEX) from its solutions in dark, and the photocatalytic degradation of the compound under LED-light irradiation. The surface- and bulk‑carbon content of M-APh is evaluated to be around 88 and 80 wt%, with the surface area of 355 m2/g and the average pore size of 3.7 nm, enabling the adsorption of 6.12 wt% KEX on its surfaces in dark. The ferromagnetic performance of M-APh, characterized by the coercivity (Hc), saturation magnetization (Ms) and remnant (Mr) values of 735 Oe, 17.9 emu/g and of 6.1 emu/g, respectively, is an asset supporting the facile separation of the agent from its suspensions. The effects of various parameters including the concentration of KEX in the solution, the dosage of M-APh, the wavelength of the LED-light, and the initial pH on the KEX removal performance of M-APh are studied. Within 5 h of LED-light irradiation of wavelengths 450, 385 and 365 nm, the KEX removal rates are recorded at 96.59, 98.61 and 99.49 %, respectively. Possible mechanisms involved in the adsorption and photocatalytic degradation of KEX are discussed.

DFT study the adsorption of ethyl xanthate on the S-site of Cu-activated sphalerite (1 1 0) surface in the presence of water molecule

Abstract The research investigates whether the copper activation of sphalerite can result in the adsorption of xanthate on the S-site of sphalerite surface at the atomic level. The adsorption of ethyl xanthate (EX) molecule on the un-activated and Cu-activated sphalerite (1 1 0) surface in the presence of water molecule was conducted by using the density functional theory (DFT). The DFT results showed that there was little chemical interaction between EX and S atom of the un-activated sphalerite (1 1 0) surface. However, the copper activation of sphalerite changed the properties of S atom by inducing a strong covalent interaction between EX and the S atom. The EX molecule did not only adsorbed on the metal atom, but also adsorbed on the S-site.

Carboxymethylcellulose (CMC) as PbS depressant in the processing of Pb-Cu bulk concentrates. Adsorption and floatability studies

Adsorption of CMC on galena (PbS) was investigated through electrokinetic, adsorption and ATR-FTIR spectroscopic studies. In addition, CMC adsorption on chalcopyrite (CuFeS2) was carried out to compare it to that on PbS. The effect of CMC on the floatability of PbS and CuFeS2 was assessed by microflotation using PbS and CuFeS2 crystals and ethyl xanthate as collector. Furthermore, the effect of oxidation of the minerals on the floatability and CMC adsorption was studied. CMC adsorption on PbS took place within a pH range of significant concentration of the hydroxo-complex species PbOH+ wherein the COOH group of the CMC is as COO−. It is proposed that CMC adsorbs through intramolecular electrostatic and acid/base interactions between the COO− and PbOH+ at the PbS/aqueous solution interface. Adsorption of ethyl xanthate on PbS is more stable than that of CMC. Oxidation creates SO4 species on the PbS surface promoting co-adsorption of CMC, through which the PbS surface becomes hydrophilic on top of the hydrophobicity due to adsorbed ethyl xanthate. Upon oxidation, the high PbS floatability was largely hindered by CMC while that of CuFeS2 was not affected. Flotation strategies are presented for the application of the non-toxic polysaccharide CMC as a depressant of PbS in the separation of Pb-Cu bulk concentrates while floating CuFeS2.

Optical luminescence studies of diffusion times at the potassium ethyl xanthate adsorption layer on the surface of sphalerite minerals

We propose reflectance measurements as a method for the evaluation of the kinetics of adsorption processes, to compute the diffusion times of the adsorption products at the thin layers formed at the sphalerite natural mineral-potassium ethyl xanthate solution interface. The method is based on the intensity measurement of the reflected monochromatic radiation obtained from the mineral-xanthate thin layer as a function of time. These determinations were made at the thin layer formed between the sphalerite or activated sphalerite natural minerals with potassium ethyl xanthate, for different solutions concentrations and pH values at constant temperature. Diffusion times of desorbed molecular species into the liquid bring important information about the global kinetics of the ions in this phase during adsorption processes at interfaces. Analysing the time dependence of this parameter one concluded on the diffusion properties of the xanthate molecule in the solution depending on its concentration and pH, knowing that at the initial time these molecules had a uniform spread. This method enabled us to determine that, in time interval of approximately 35 minutes to achieve dynamic equilibrium in the formation of the interface layer, one had three different kinetic behaviours of our systems. In the first 5-8 min one had highly adsorbent character, the state of equilibrium is followed by low adsorbent properties. Gaining information on the adsorption kinetics in the case of xanthate on mineral surface leads to the optimization of the industrial froth flotation process.

Adsorption of ethyl xanthate on ZnS(110) surface in the presence of water molecules: A DFT study

The interaction of collector with the mineral surface plays a very important role in the froth flotation of sphalerite. The adsorptions occurred at the interface between the mineral surface and waters; however most of DFT simulations are performed in vacuum, without consideration of water effect. Semiconductor surface has an obvious proximity effect, which will greatly influence the surface reactivity. To understand the mechanism of xanthate interacting with sphalerite surface in the presence of water molecules, the ethyl xanthate molecule adsorption on un-activated and Cu-activated ZnS(110) surface in the absence and presence of water molecules were performed using the density functional theory (DFT) method. The calculated results show that the adsorption of water molecules dramatically changes the properties of ZnS surface, resulting in decreasing the reactivity of surface Zn atoms with xanthate. Copper activation of ZnS surface changes the surface properties, leading to the totally different adsorption behaviors of xanthate. The presence of waters has little influence on the properties of Cu-activated ZnS surface. The xanthate S atom can interact with the surface S atom of Cu-substituted ZnS surface, which would result in the formation of dixanthogen.

Competitive Adsorption of Xanthates with Different Chain Lengths on Chalcopyrite Particles

We studied competitive adsorption of ethyl xanthate (C2X) and amyl xanthate (C5X) on an aqueous suspension of chalcopyrite particles. We first investigated their chemi- and physisorption separately and then explored whether there was any difference in the bonding strengths of the chemisorbed cuprous–xanthate complexes with C2X and C5X. Further, we monitored the competition between C2X and C5X in chemi- and physisorption on the chalcopyrite surface using different C2X and C5X binary solutions. It was found that prechemisorbed C2X can be desorbed and replaced by postadded C5X but that prechemisorbed C5X cannot be replaced by postadded C2X. This clearly indicates that the bonding strength of the cuprous–xanthate complex is much higher for C5X than for C2X. When C2X and C5X are simultaneously added to the chalcopyrite suspension, C5X is chemisorbed first, and only when C5X cannot cover the full surface is C2X chemisorbed. An adsorption phase diagram is defined that describes how the chemi- and physisorption o...

Optical luminescence studies of the ethyl xanthate adsorption layer on the surface of sphalerite minerals

In this work we propose optical luminescence measurements as a method to evaluate the kinetics of adsorption processes. Measurement of the intensity of the integral optical radiation obtained from the mineral–xanthate interface layer, stimulated with a monochromatic pulsating optical signal, as a function of time were made. The luminescence radiation was obtained from the thin interface layer formed at the separation surface between the sphalerite natural mineral and potassium ethyl xanthate solution, for different solution concentrations and pH-es at the constant industry standard temperature. This method enabled us to determine the time to achieve dynamic equilibrium in the formation of the interface layer of approximately 20min, gaining information on the adsorption kinetics in the case of xanthate on mineral surface and leading to the optimization of the industrial froth flotation process.

DFT study of ethyl xanthate interaction with sphalerite (110) surface in the absence and presence of copper

Abstract The interaction among sphalerite (1 1 0) surface, copper and ethyl xanthate (EX) was simulated using the density functional theory (DFT). The results of DFT indicate that four types of stable interaction models exist among sphalerite surface, copper and EX, i.e., EX interacts with the Cu substituted for Zn, Cu adsorbed on the top site of S, Cu adsorbed on the bridge site of S and Cu(OH) 2 adsorbed on the sphalerite surface. The four interaction models can result in the activation flotation of sphalerite. Density of states (DOS) analysis shows that the energy level discrepancy of the Zn 3d orbital in ZnS and the bonding S 3p orbital in EX results in the weak adsorption of EX on un-activated sphalerite surface. However, after copper activation, the Cu 3d orbital peak and bonding S 3p orbital peak are just maximally overlapped nearby the Fermi level. This study provides an insight into the nature that sphalerite responds not well to EX and also a comprehensive understanding on the possible interaction cases existing among sphalerite surface, copper and EX.

Ethyl xanthate adsorption and adsorption kinetics on lead-modified galena and sphalerite under flotation conditions

Infrared attenuated total reflection spectrophotometry, UV data, microelectrophoresis and a Hallimond tube flotation cell have been used to investigate the effect of Pb(II) on the galena and sphalerite surface properties (hydrophobicity and charge of the surface), ethyl xanthate adsorption and ethyl xanthate adsorption kinetics in alkaline medium. It has been found that lead adsorbed on the galena or sphalerite surface as Pb(OH) + and less as Pb 2+ reduced the collectorless galena floatability from pH 7 to 9.5, but had a strong activating effect on natural sphalerite floatability (in pH range 7.6–10.5). Collecting of Pb(II)-modified minerals with K-ethyl xanthate both forms of lead ethyl xanthate, monolayer, Pb EX (chemically adsorbed (EX) −), and multilayer, physically adsorbed Pb(EX) 2, were detected on the mineral surfaces. Sphalerite floated 90–100% in pH range from 7 to 9.5, but galena floated better only from pH 8 to 9.5 (85–95%). The main surface reaction in pH range 8–9.5 is probably the ion-exchange reaction M Pb OH + (EX) − = M Pb EX + (OH) − (M—mineral), which contributes to the chemical adsorption of (EX) − as monolayer Pb EX, on the surface of either mineral. The reaction between Pb(II)-treated mineral and (EX) − ion is a reaction of pseudo-first order with respect to ethyl xanthate (on Pb(II)-modified galena the rate constant is k 1 = 0.711 min −1; on Pb(II)-modified sphalerite k 1 = 0.1014 min −1).

Effect of copper atoms on the adsorption of ethyl xanthate on a sphalerite surface

Ab initio cluster model calculations were performed to study the interaction of hydroxyl ion (OH −) and ethyl xanthate ( CH 3 CH 2 OCS 2 - ) with a copper doped and pure sphalerite (1 1 1) surface. Calculations showed that both adsorbates interact strongly. The interaction energy of ethyl xanthate depends more on the position of copper and zinc sites of the Cu-doped ZnS structure than the number of copper atoms. The coordination mode of ethyl xanthate is bridge-like. The hydroxyl ion interacts more strongly on the zinc sites of the surface. The replacement of hydroxyl ion by ethyl xanthate is more favourable when hydroxyl ion is on the copper site of the surface and the second layer zinc atom has been replaced with copper. The copper atoms in the sphalerite crystal structure enhance the electron acceptor ability of sphalerite.

Adsorption and Electrosorption of Ethyl Xanthate and Thiocyanate Anions at High-Area Carbon-Cloth Electrodes Studied by in Situ UV Spectroscopy: Development of Procedures for Wastewater Purification

Adsorption and electrosorption behavior of ethyl xanthate (EtX-) and thiocyanate (SCN-) anions, individually and when they are together in a solution, were studied at high-area C-cloth electrodes by in situ UV spectroscopy in relation to development of methodologies for purification of industrial wastewaters. The employment of straightforward, yet demonstrably useful spectrophotometric techniques of kinetics and scanning kinetics is described. Adsorption isotherms of EtX- and SCN- were also derived. However, EtX- was found to decompose to a small extent during electrosorption on C-cloth and/or Au or Pt surfaces, causing some interference with the spectrophotometric analysis of SCN- at 215 nm. After long prior contact of the C-cloth with water, the adsorption rates of EtX- and SCN- are somewhat increased. Competitive adsorption studies show that SCN- ion does not become adsorbed on the C-cloth in the presence of EtX-, thus demonstrating a remarkable discriminatory effect.

Ethylxanthate Adsorption on Copper Sulfide Influence of the Copper Sulfide Composition

The adsorption of ethylxanthate upon copper sulfide has been studied by electrochemical impedance spectroscopy. Prior to each experiment being performed, the copper sulfide composition was fixed by imposing a constant potential. The spectra with and without ethylxanthate in the solution show no difference below the potential threshold, but above this potential the spectra differed dramatically. The shapes of the impedance diagrams were interpreted by formation of a bilayer structure at the surface of the mineral which develops in two steps at the same potential. The first layer corresponds to a chemisorbed layer while the porous second layer comprises copper xanthate. An explanation for the suppressor effects of the anions is also given in terms of the redox potential for the redox couple. © 2000 The Electrochemical Society. All rights reserved.

In situ orientation study of xanthate on copper under potential control

Abstract Adsorption and orientation of ethyl xanthate on a copper electrode was studied using an in situ spectroelectrochemical set up. Cuprous xanthate was identified to be the major product over the potential range −0.5 to −0.1 V (SCE). A further increase in electrode potential to 0.1 V resulted in the formation of dixanthogen in addition to cuprous xanthate. The characteristic dixanthogen bands disappeared and the intensity of cuprous xanthate bands increased when the potential was brought back and held at −1.0 V. With polarized radiation, the spectral appearance of cuprous xanthate changed in contrast to that of dixanthogen, suggesting preferential orientation of cuprous xanthate molecules but random orientation for dixanthogen.

Characterization of the ethyl xanthate adsorption layer on galena (PbS) by synchrotron radiation excited photoelectron spectroscopy

Utilization of synchrotron radiation excitation in photoelectron spectroscopy (SR-XPS) of solid surfaces provides a significant improvement in surface sensitivity of the method. It has recently been shown that almost an order of magnitude increase in relative intensity of the sulfur 2p signal from the very first atomic layer of a sulfide can be achieved by using SR instead of conventional AlKα or MgKα X-rays for photoelectron excitation. In this work, SR-XPS was applied to characterize the xanthate layer adsorbed on galena in 10 −4 M potassium ethyl xanthate solution (pH 9.2) in equilibrium with air. Chemisorption of xanthate radicals rather than formation of bulk lead ethyl xanthate was observed. Prolonged irradiation of the sample by the SR beam was observed to decompose the adsorption layer. Means to avoid radiation damage during the SR-XPS measurement is discussed.

A combined in situ infrared spectroscopy and scanning tunnelling microscopy study of ethyl xanthate adsorption on Au(111)

We have used insitu FTIR and STM in a complementary study of chemisorbed ethyl xanthate on gold. We have limited the potential region to avoid the formation of oxidation products of ethyl xanthate. The FTIR results show a clear adsorbate band at ca. 1210 cm-1, which is assigned to the asymmetric C–O–C stretch of the chemisorbate. Notably, no asymmetric CS2 stretch is observed. This data favours an adsorbate structure, in which both sulfur atoms bond to the surface, the molecular plane of the S2C–O group is perpendicular to the surface and the alkyl chain of the molecule face towards the electrolyte. Two ordered ethyl xanthate overlayers are imaged on Au(111) by insitu STM. We propose a unit cell for one of these overlayers.

The adsorption of potassium ethyl xanthate on pyrite and effect of Na 2S on the concentration of xanthate ion in the potassium ethyl xanthate solution

In the adsorption of potassium ethyl xanthate on pyrite at pH 3, it was observed that approximately half of the commercial potassium ethyl xanthate remains in the solution and the remaining xanthate is not as xanthate ion; it is in the form of decomposition products of xanthate ion. Addition of Na 2S increases the xanthate ion concentration in the commercial ethyl xanthate solution.

Characteristics of Ethyl Xanthate Adsorption Reaction on Silver and Silver-Gold Alloys

ABSTRACT The interaction of ethyl xanthate with silver and silver-gold alloys was investigated by voltammerty, FITR spectroscopy, UV/Vis spectroscopy, and measurements of contact angle. Voltammograms for silver and silver-gold alloy electrodes were characterized by a prewave occurring at potentials lower than that for the formation of silver ethyl xanthate. Identification of the prewave with chemisorption was substantiated by monitoring solution composition with UV/Vis spectroscopy and FTIR spectra of silver surfaces polarized in the chemisorption region. It was found that chemisorption of xanthate occurred on the silver and alloy surfaces prior to silver xanthate formation and rendered the surfaces hydrophobic. Coverage of chemisorbed xanthate was found to obey a Frumkin isotherm. Eh-pH diagrams have been constructed that include chemisorption in addition to silver xanthate and dixanthogen formation.