The adsorption of trifluoromethanesulfonate anions at the mercury/electrolyte interface

Recently, there has been much interest in the use of trifluoromethanesulfonic acid as an electrolyte in advanced fuel cell systems because of the enhanced rate of oxygen reduction in this medium. In order to elucidate this characteristic from a double layter point of view, the present work was undertaken to study the adsorption of trifluoromethanesulfonate ions on mercury electrodes. Differential capacities and potentials of zero charge were measured in constant ionic strength solutions of composition X M CF₃SO₃ K + (1-X) M KF at 25°C. Analysis of the results shows that the extent of specific adsorption of CF₃SO₃^? anions is small, and the anions even desorb from the surface at sufficiently positive electrode charges. The structure of the inner layer is elucidated, and an isotherm for the adsorption of CF₃SO₃^? based on electrostatic models of the double layer is derived. The results indicate that at the potentials for the electroreduction of oxygen CF₃SO₃^? anions will not interfere with the adsorption of the reactant and of intermediates, allowing faster rates to be achieved.     

Electrochemical syntheses—XIII[1]. The hydroxylation of chlorobenzene via the electrosynthesis of trifluoroacetates

Anodic substitution of chlorobenzene in CF₃COOH/0.2-0.4M CF₃COONa leads to 94% product yield of trifluoroacetates (at 70% c.e.). Prolonged electrolysis yields 72% of disubstituted derivatives (at 61% c.e.). By hydrolysis of the trifluoroacetates the corresponding phenol, resorcinol, and pyrocatechol derivatives can easily be obtained.     

The electrodepositions of copper and nickel from trifluoroacetate-H2O baths

In the present study, the electrodepositions of copper from the Cu(CF₃COO)₂CF₃COOHH₂O bath and nickel from the Ni(CF₃COO)₂NH₄ClH₂O bath, were studied.In the copper electrodeposition from Cu(CF₃COO)₂ (100 g/l)CF₃COOH(0.1 N)H₂O bath, the cathode current efficiency showed about 100% and the anode current efficiency showed over 100% at low cd. In the nickel electrodeposition from Ni(CF₃COO)₂ (200 g/lH₄Cl(15.0 g/l)H₂O bath, the efficiencies of the cathode and anode were about 100%. The range of current density to obtain bright and smooth copper and nickel deposits were 4.0 ～ 24 A/dm², 5.0 ～ 16 A/dm² respectively, and the cross-section of the electrodeposits showed a granular structure.The rates of the electrodeposition of copper and nickel from the above-mentioned baths were controlled by the charge-transfer reaction in the same way as in the reaction in non-aqueous solution[1, 2].     

New soluble π-conjugated polymers containing 2-diisopropylamino-1,3,5-triazine unit: synthesis,characterization and optical properties

A new type of π-conjugated polymers containing 2-diisopropylamino-1,3,5-triazine were prepared via Sonogashira or Suzuki coupling reaction. The structures of the polymers were performed by FT-IR, ¹H-NMR, UV–vis spectroscopy, photoluminescence spectroscopy, gel permeation chromatography, thermal analysis and X-ray diffraction analysis. These derived polymers were soluble in common organic solvents such as tetrahydrofuran, chloroform, toluene, and showed good thermal stability. Polymers containing 1,4-diethynyl-2,5-bis(dialkoxy)benzene unit in polymer main chain emitted blue-green light in solution phase under UV light irradiation except with polymer containing 9,9-dioctylfluorene(blue light). Acidochromic behaviors of polymers were studied in CHCl₃-CF₃COOH mixtures. 9,9-Dioctylfluorene-containing polymer displayed better acidochromic property and linear relationship between absorbance and concentration with the concentration of CF₃COOH from 5.384?×?10^?4 to 26.92?×?10^?4 mol/L. Electrochemical behaviors of polymers depicted p-doping and some hole-transporting properties. XRD results showed that polymers exhibited certain crystallinity.     

The conductance of 1:1 electrolytes in sulfolane in the presence of proton donors at 30°C

The molar conductances of LiCl, LiNO₃, KCHCl₂COO and Na p-(NO₂)C₆H₄O in sulfolane, in the presence of HCl, CH₃COOH, CHCl₂COOH and p-(NO)₂C₆H₄OH have been determined. The data were analysed by the full Pitts equation and interpreted in terms of the ionic association constant (K_A) of the salts K⁺A^? and K⁺RHA^?, and the heteroconjugation constant (K_f) of RHA^?. Values of K_f have been calculated from the ratio of association constant K_A(K⁺A^?)/K_A(K⁺RHA^?).     

Facile synthesis of imprinted submicroparticles blend polyvinylidene fluoride membranes at ambient temperature for selective adsorption of methyl <Emphasis Type="Italic">p</Emphasis>-hydroxybenzoate

We developed a simple phase inversion technique to prepare molecularly imprinted membrane (MIM) at room temperature for membrane selective adsorption and separation of methyl p-hydroxybenzoate (M4HB). The prepared SMIP-MIM was characterized by SEM, FT-IR, TGA. Compared with non-imprinted membrane (NIM_1-5) adsorbent, SMIP-MIM_1-5 adsorbent with high specific surface area and showed higher binding capacity, faster kinetic and better selectively adsorption capacity for M4HB. The maximum isotherm adsorption capacity for M4HB of SMIP-MIM₄ was 3.519mg·g^?1, and the experimental data was well fitted to the slips model by multiple analysis. The maximum kinetic adsorption capacity and equilibrium adsorption time for SMIP-MIM₄ were 1.335mg·g^?1 and 160 min, respectively. The mechanism for dynamic adsorption of M4HB onto SMIP-MIM₄ was found to follow pseudo-first-order model and pseudo-second-order model. Additionally, the permeability separation factor of SMIP-MIM₄ for M4HB compared to a structural analogues methyl 2-hydroxybenzoate (M2HB) could reach 2.847. The adsorption capacity of SMIP-MIM₄ for M4HB and M2HB was 0.549mg·cm^?2 and 1.563mg·cm^?2, respectively. The adsorption behavior of M4HB through SMIP-MIM₄ followed the retarded permeation mechanism.     

Surface hydrolysis of postconsumer polyethylene terephthalate to produce adsorbents for cationic contaminants

In this work, the surface hydrolysis of postconsumer polyethylene terephthalate (PET) was used to produce an ion exchange material to adsorb cationic contaminants from water. The PET surface hydrolyses were carried out in neutral, alkaline, and acid media (NaOH or HNO₃ at 7, 10, and 15 mol L^?1) under reflux producing surface carboxylic acid sites (? COOH) characterized by ATR‐IR, pyridine adsorption, titration, TG, and DSC analyses. Acid hydrolysis produced high concentrations of ? COOH (up to 0.5 mmol g^?1_PET), whereas no significant concentration of carboxylic acid sites was obtained by neutral and alkaline hydrolysis. SEM analyses suggest that the acid sites are likely located at the cracks and defects produced on the PET surface by acid hydrolysis. Neutral or alkaline hydrolysis produced a very regular and smooth PET surface with very low acid site concentrations. The adsorption isotherms of Cd⁺² as a model of heavy metal and the dye methylene blue as a model of large organic cationic molecules showed high adsorption capacities for the HNO₃‐hydrolyzed PET, whereas no adsorption takes place on the neutral‐ or alkaline‐hydrolyzed polymer. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5284–5291, 2006     

A trinuclear anionic trifluoroacetato derivative of iron(II) containing a central O(–I) ligand

The reaction of Fe(CO)₅ with CF₃COOH/(CF₃CO)₂O, or with CF₃COOH, in DMF at about 140 °C produces the colourless compound 1, [Fe(DMF)₆][Fe₃(μ₃-O) (CF₃COO)₆(DMF)₃]₂, constituted by the [Fe(DMF)₆]²⁺ cation and by two [Fe₃(μ₃-O)(μ₂-CF₃COO)₆(DMF)₃]⁻ anions, with a triangular disposition of the three iron atoms, the central substantially coplanar oxygen atom being formulated as a singly charged anion O(–I) stabilized by complexation to iron(II).     

Synthesis of brominated acenaphthylenes and their flame-retardant effects on ethylene–propylene–diene terpolymer

Bromoacenaphthylenes and their condensates as flame-retardant reagents were synthesized by bromination of acenaphthylene using ZnCl₂? CF₃COOH or FeCl₃ as catalysts and subsequent dehydrobromination. The chief components were identified as bromoacenaphthylene monomers when ZnCl₂? CF₃COOH were used, and as their condensates (mostly trimers) in the case of FeCl₃. Their performance as flame-retardant reagents for ethylene–propylene–diene terpolymer (EPDM) was evaluated by measuring the oxygen index of finished compounds, and flammability by a vertical flammability test based on UL-94-VO. Both the monomers and the condensates demonstrated high flame-retardant effectiveness. The high efficiency was attributed to their excellent dispersity in the base polymer and their characteristic thermal decomposition behavior. In TGA, they decomposed in a very wide range of temprature (ca.200–560°C), which covers the decomposition range of EPDM. This was attributed to the existence of bromines of different thermal stabilities in one molecule.     

Specific adsorption of acetate ions at the mercury—lithium acetate (AQ) interface

Specific adsorption of acetate ions at the mercury—lithium acetate (aq) interface has been investigated using both differential capacity and electrocapillary measurements. Variation of charge due to surface excess of lithium ions (q⁺) and of charge due to specifically adsorbed acetate ions (q^?1 with electrode charge (q^M) have been discussed. Such discussion inferred superequivalent adsorption of acetate ions at all positive charges for concentrations of lithium acetate ≥0.20 M whereas Esin-Markov plots predicted the absence of specific adsorption; the prediction of Esin-Markov plots has been shown to be faulty under certain conditions. The plots of φ^M-2vsq^?1 at constant q^M for acetate ion resembled the corresponding plots for F^? and BF^?₄ ions; the slope of these plots is negative up to coverages corresponding to 0.20 M lithium acetate. The identification of the isotherm parameter, (?φ^M-2/?q^?1)_q^M with the reciprocal of inner layer capacity at constant charge (_^?1Cⁱ) has been questioned.     

Synthesis and Surface Activities of Novel Succinic Acid Monofluoroalkyl Sulfonate Surfactants

Two environmentally friendly succinic acid monofluoroalkyl sulfonate surfactants were synthesized from maleic anhydride and polyethylene glycol mono (1H,1H,7H‐dodecafluoroheptyl) ether, i.e. H(CF₂)₆CH₂OCH₂CH₂OCOCH(SO₃Na)CH₂COOH (FEOS‐1) and H(CF₂)₆CH₂(OCH₂CH₂)₃OCOCH(SO₃Na)CH₂COOH (FEOS‐3). The obtained surfactants were characterized by FT‐IR, ¹H NMR, ¹³C NMR and ¹⁹F NMR in detail. The synthesized fluorinated surfactants have a high thermal stability on the basis of thermogravimetric analysis. Their surface properties were examined and the results show that FEOS‐1 and FEOS‐3 surfactants can reduce the surface tension of water to 25.55 mN m^?1 at 10.25 mmol L^?1 and 21.63 mN m^?1 at 8.33 mmol L^?1, respectively; meanwhile, the introduction of oxyethylene groups enhances the hydrophilicity and micellar forming ability and the longer oxyethylene chains the better surface properties. The Krafft points (K_p) of FEOS‐1 and FEOS‐3 were both below 0 °C, which was lower than perfluoro‐n‐heptanesulfonic acid sodium salt (n‐C₇F₁₅SO₃Na, K_p = 56.5 °C) at a similar length of fluorocarbon chains. Comparison studies on two surfactants above and the conventional fluorocarbon surfactants, perfluorooctanoate of ammonium (PFOA) show that the surfactants have comparable properties to PFOA, thus offering an environmentally friendly synthesizing alternatives to PFOA.     

Ionic association equilibria of copper(II) trifluoroacetate in dimethyl sulphoxide

The molar conductivity curve and changes in the visible spectrum induced by changing concentrations have been determined for Cu(CF₃COO)₂ in dimethyl sulphoxide (DMSO) solution, at 25°C. Coupled with the spectra of the Cu(ClO₄)₂ + Bu₄N CF₃COO mixed solutions the results indicate occurence of the CuCF₃COO⁺ complex as the predominant copper(II) species in the solutions of Cu(CF₃COO)₂. The next higher complex, Cu(CF₃COO)⁰₂, is only formed at high concentrations of Cu(CF₃COO)₂ or under excess concentration of the CF₃COO^? anion. Formation of the first complex has also been studied callorimetrically, its derived thermodynamic characteristics being: K⁰₁ = 697 ± 12, ΔH⁰ = (7.85 ± 0.2) kJ/mol, and ΔS° = (80.6 ± 1.6) J/K mol, at 25°. On the other hand, K⁰₂ is only estimated as 13 ± 5. The results are compared with those previously obtained for the other divalent transition metal trifluoroacetates and the nature of the CuCF₃COO⁺ complex is discussed.     

Observations of the diffusion coefficient of the perhydroxyl ion (HO−2) in lithium hydroxide solutions

The diffusion coefficient of the perhydroxyl ion (HO^?₂) was determined in 4.5 M LiOH supporting electrolyte. Over the range of concentration 0.2–0.8 M H₂O₂ it was found to be independent of concentration and had a value of 5 ± 0.2 × 10^?6 cm²/s at 293 K. The experimental data were obtained chronoamperometrically used a rde. At the limiting current, O₂ evolution was found to be almost entirely suppressed and the current limiting species was therefore assumed to be the HO^?₂ ion. The electrochemical mechanism for the perhydroxyl reduction reaction was invoked to explain the experimental results.     

Reusability and selective adsorption of Pb<Superscript>2+</Superscript> on chitosan/P(2-acrylamido-2-methyl-1-propanesulfonic acid-<Emphasis Type="Italic">co</Emphasis>-acrylic acid) hydrogel

Reusability and selective adsorption toward Pb²⁺ with the coexistence of Cd²⁺, Co²⁺, Cu²⁺ and Ni²⁺ ions on chitosan/P(2-acrylamido-2-methyl-1-propanesulfonic acid-co-acrylic acid) [CS/P(AMPS-co-AA)] hydrogel, a multi-functionalized adsorbent containing –NH₂, –OH, –COOH and –SO₃H groups was studied. The CS/P(AMPS-co-AA) was prepared in aqueous solution by a simple one-step procedure using glow discharge electrolysis plasma technique. The reusability of adsorbent in HNO₃, EDTA-2Na and EDTA-4Na was investigated in detail. The competitive adsorption of the metal ions at the initial stage was compared between their equal mass concentration and equal molar concentration. In addition, the adsorption mechanism of the adsorbent for adsorption of Pb²⁺ was also analyzed by XPS. The results showed that the optimum pH of adsorption was 4.8, and time of adsorption equilibrium was about 180 min. Adsorption kinetics fitted well in the pseudo second-order model. The equilibrium adsorption capacities of Pb²⁺, Cd²⁺, Co²⁺, Cu²⁺, and Ni²⁺ at pH 4.8 were obtained as 673.3, 358.3, 176.7, 235.0 and 171.7 mg g^?1, in their given order. The adsorbent displayed an excellent reusability using 0.015 mol L^?1 EDTA-4Na solution as the eluent, and the desorption ratio could not correctly reflect the true characteristics of adsorption/desorption process. Moreover, the adsorbent showed good adsorption selectivity for Pb²⁺. The molar adsorption capacity at the initial stage with equal molar concentration was more reliable than the mass adsorption capacity during the study of selective adsorption. According to the XPS results, the adsorption of Pb²⁺ ions by the CS/P(AMPS-co-AA) absorbent could be attributed to the coordination between N atom and Pb²⁺ and ion-exchange between Na⁺ and Pb²⁺.     

Specific adsorption of formate ions at the mercury—aqueous solution interface

Adsorption on polarized Hg electrode of formate ions from aqueous solutions of pure HCOONa using differential capacity measurements was studied. Anion specific adsorption was indicated by the cathodic shift of potential of zero charge with increase in bulk-electrolyte activity. Variation of charge due to surface excess of sodium ions (Γ ₊ Z₊ F) and of charge due to specifically adsorbed formate ions (q¹), with electrode charge (q^M) indicated super-equivalent adsorption of formate ions at all positive charges and for all concentrations studied. Esin—Markov coefficient was found to be unreliable criterion of the occurence of specific adsorption. Logarithmic form of constant charge adsorption isotherms were found to be followed. The plots of φ^{M ? 2}vs q¹ at constant q^M were not linear and resembled those for F^?, BF₄^? and CH₃COO^? ions; which is attributed to relatively weak specific adsorption of anions.     

Adsorption and desorption dynamics of CF<Subscript>4</Subscript> on activated carbon beds: Validity of the linear driving force approximation for pressure-changing steps

Adsorption and desorption dynamics of CF₄ on an activated carbon bed were studied experimentally and theoretically, focusing on pressure-changing steps. The theoretical model used the ideal adsorbed solution (IAS) theory and the linear driving force (LDF) approximation as equilibrium and mass transfer models, respectively. Adsorption breakthrough curves of raw CF₄ gas (500, 1,000, and 1,500 ppm) were well predicted by the theoretical model and the diffusion time constant for CF₄ was found to be 3.3×10^?3 s^?1 from breakthrough curve fitting. Changes in the CF₄ concentration during depressurization could be easily predicted using the above mathematical model when the half-cycle time (θ _c ) was above 0.1. However, significant discrepancies were observed between the predicted CF₄ concentrations and the experimental data when θ _c was 0.1. Nakao and Suzuki also reported that proportional constant of LDF approximation (=KD _e /R _p ²) needs to be modified when θ _c is less than 0.1.     

Simple introduction of anion trapping site to polymer electrolytes through dehydrocoupling or hydroboration reaction using 9-borabicyclo[3.3.1]nonane

Organoboron-based anion trapping polymer electrolytes were synthesized through hydroboration or dehydrocoupling reaction between poly(propylene oxide) (PPO) oligomer (M_n = 400, 1200, 2000 and 4000) and 9-borabicyclo[3.3.1]nonane (9-BBN). Obtained oligomers were added various lithium salts (LiN(CF₃SO₂)₂, LiSO₃CF₃, LiCO₂CF₃ or LiBr) to analyze the ionic conductivity and lithium ion transference number (tLi⁺). The ionic conductivity of the oligomer in the presence of LiN(CF₃SO₂)₂ showed higher ionic conductivity than other systems, however, the tLi⁺ was less than 0.3. When LiSO₃CF₃ or LiCO₂CF₃, was added high tLi⁺ over 0.6 was obtained. Such difference in tLi⁺ can be explained by HSAB principle. Since boron is a hard acid, soft (CF₃SO₂)₂N⁻ anion can not be trapped effectively. High ionic conductivity of 1.3 × 10⁻⁶ S cm⁻¹ and high tLi⁺ of 0.73 was obtained when PPO chain length was 2000. These values of facilely prepared polymer electrolytes are comparable to those of the PPOs having covalently bonded salt moieties on the chain ends.     

Outer-sphere association of ions in DMSO solutions of nickel(II) salts

The visible absorption spectra and the molar conductance curves of solutions of NiI₂, NiBr₂, Ni(BF₄)₂, Ni(ClO₄)₂ and Ni(CF₃COO)₂ DMSO at 25°C have been determined. The results indicate a weak association which is only of the outer-sphere type, in each case involving the Ni(DMSO)^{2 +}₆ complex. The conductance data are analysed using the Lee-Wheaton conductance equation for unsymmetrical electrolytes. The first-step association constants (K₁) and the limiting ionic conductances, λ₀, for the Ni(DMSO)^{2 +}₆ cation as well as for the BF^?₄ and CF₃COO^? anions are obtained. A linear relation between log K₁ and the reciprocal of the anionic radius is observed. On the basis of this relation, the relative contribution of the outer-sphere association for solutions of NiCl₂ in DMSO is estimated.     

Marked reduction in the thermal conductivity of (La0.2Gd0.2Y0.2Yb0.2Er0.2)2Zr2O7 high-entropy ceramics by substituting Zr4+ with Ti4+

The (La_0.2Gd_0.2Y_0.2Yb_0.2Er_0.2)₂(Zr_1-xTi_x)₂O₇ (x = 0–0.5) high-entropy ceramics were successfully prepared by a solid state reaction method and their structures and thermo-physical properties were investigated. It was found that the high-entropy ceramics demonstrate pure pyrochlore phase with the composition of x = 0.1–0.5, while (La_0.2Gd_0.2Y_0.2Yb_0.2Er_0.2)₂Zr₂O₇ shows the defective fluorite structure. The sintered high-entropy ceramics are dense and the grain boundaries are clean. The grain size of high-entropy ceramics increases with the Ti⁴⁺ content. The average thermal expansion coefficients of the (La_0.2Gd_0.2Y_0.2Yb_0.2Er_0.2)₂(Zr_1-xTi_x)₂O₇ high-entropy ceramics range from 10.65 × 10^?6 K^?1 to 10.84 × 10^?6 K^?1. Importantly, the substitution of Zr⁴⁺ with Ti⁴⁺ resulted in a remarkable decrease in thermal conductivity of (La_0.2Gd_0.2Y_0.2Yb_0.2Er_0.2)₂(Zr_1-xTi_x)₂O₇ high-entropy ceramics. It reduced from 1.66 W m^?1 K^?1 to 1.20 W m^?1 K^?1, which should be ascribed to the synergistic effects of mass disorder, size disorder, mixed configuration entropy value and rattlers.     

Synthesis and characterization of fluorescent PEG-polyurethane with free carboxyl groups

An innovative spherical poly(vinyl alcohol)(PVA)/peat/clay porous composite bead was prepared and shown to be suitable for use as an adsorbent. The mass transport process for the adsorption of metal ions onto this composite bead in an aqueous system was investigated. In the external mass transport process, the diffusion coefficient (D₁) of Cu⁺² and Zn⁺² ions increased with increasing initial metal ion concentration and the increasing effect was more pronounced in the initial metal ion concentrations range of 18?×?10^-3 to 22?×?10^-3?M. The diffusion rate of Zn⁺² ions was faster than that of Cu⁺² ions. In the intraparticle diffusion process, the diffusion coefficient (D₂) decreased with increasing initial metal ion concentration in the initial concentration range of 1?×?10^-3 to 4?×?10^-3?M, and the value of D₂ maintained an almost constant value in the initial concentration range of 8?×?10^-3 to 22?×?10^-3?M. The rate of ion diffusion within the adsorbent for Cu⁺² ions was faster than that for Zn⁺² ions. The adsorption mechanism was controlled by the intraparticle diffusion process. The adsorption followed the Langmuir adsorption isotherm model. The maximum amount of adsorbed metal ions for Cu⁺² and Zn⁺² ions were 22.57 and 13.62?mg/g composite bead, respectively.