Electronegativity Of Metal Ion Research Articles

Average metal ion electronegativity as a general descriptor for screening Ni-based double hydroxides with high electrocatalytic water oxidation activity

A descriptor based on the metal ion electronegativity is designed to screen the optimal Ni-based double hydroxides OER electrocatalyst. • The metal ion electronegativity (MIE) represents the intrinsic chemical property. • A volcano trend for MIE vs OER intrinsic activity of Ni-based DHs is described. • The best DHs in the peak of the volcano plot is Ni 0.8 Co 0.2 DHs (MIE = 1.39). • MIE differences affect the metallic electronic structure in OER activity. • A MIE descriptor is used to rapidly screen the DHs-based electrocatalyst. Due to the multiclass complex processes in the oxygen evolution reaction (OER) by Ni-based double hydroxides (DHs) electrocatalysts, it is necessary to seek a comprehensive assessment to uncover the electrochemical nature. Here, Ni 0.8 M 0.2 DHs and Ni 0.7 M 0.3 DHs nanowires (M = Zn, Co, Fe, Cu) were prepared by a hydrothermal method. As the intrinsic chemical property, metal ion electronegativity (MIE) as the descriptor, the structure–activity relationship between MIE and OER reaction intermediates' adsorption and desorption capacity was researched by the electrochemical impedance analysis. At the top of the volcano trend (MIE = 1.39, Ni 0.8 Co 0.2 DHs), it is screened and exhibits the lowest interfacial charge transfer resistance and the adsorption and desorption resistance of intermediates. This work provides a cost-effective method based on the theory of electronegativity equilibrium for the precise screening and design of high-active OER electrocatalysts.

Functionalized nanostructured silica by tetradentate-amine chelating ligand as efficient heavy metals adsorbent : Applications to industrial effluent treatment

Organofunctionalized nanostructured silica SBA-15 with tri(2-aminoethyl)amine tetradentate-amine ligand was synthesized and applied as adsorbent for the removal of Cu2+, Pb2+, and Cd2+ from both synthetic wastewater and real paper mill and electroplating industrial effluents. The prepared materials were characterized by XRD, N2 adsorption-desorption, TGA, and FT-IR analysis. The Tren-SBA-15 was found to be a fast adsorbent for heavy metal ions from single solution with affinity for Cu2+, Pb2+, than for Cd2+ due to the complicated impacts of metal ion electronegativity. The kinetic rate constant decreased with increasing metal ion concentration due to increasing of ion repulsion force. The equilibrium batch experimental data is well described by the Langmuir isotherm. The maximum adsorption capacity was 1.85 mmol g−1 for Cu2+, 1.34 mmol g−1 for Pb2+, and 1.08 mmol g−1 for Cd2+ at the optimized adsorption conditions (pH=4, T=323 K, t=2 h, C0=3 mmol L−1, and adsorbent dose=1 g L−1). All Gibbs energy was negative as expected for spontaneous interactions, and the positive entropic values from 103.7 to 138.7 J mol−1 K−1 also reinforced this favorable adsorption process in heterogeneous system. Experiment with real wastewaters showed that approximately a half fraction of the total amount of studied metal ions was removed within the first cycle of adsorption. Hence, desorption experiments were performed by 0.3M HCl eluent, and Tren-SBA-15 successfully reused for four adsorption/desorption cycles to complete removal of metal ions from real effluents. The regenerated Tren-SBA-15 displayed almost similar adsorption capacity of Cu2+, Pb2+, and Cd2+ even after four recycles. The results suggest that Tren-SBA-15 is a good candidate as an adsorbent in the removal of Cu2+, Pb2+, and Cd2+ from aqueous solutions.

Electron paramagnetic resonance probed oxygen deficiency in SrTiO3 with different cap layers

The oxygen vacancies in the SrTiO3 (STO) single crystal with two different cap layers, CoFe2O4 (CFO) and BiFeO3 (BFO), are investigated with the technique of electron paramagnetic resonance (EPR). EPR spectra show the resonance lines of the residual oxygen vacancy in air annealed STO, STO/CFO, and STO/BFO, showing the high sensitivity of EPR to the low concentration defects. The experimental results indicate that the oxide cap layers enhance the oxygen deficiency in bulk STO and the amount of oxygen vacancy is dependent on the electronegativity of metal ion in the cap layer. Accordingly, STO/BFO has a larger amount of oxygen vacancy than that of STO/CFO.

Adsorption of divalent heavy metal ions onto IDA-chelating resins: Simulation of physicochemical structures and elucidation of interaction mechanisms

The adsorption performances, under static as well as dynamic conditions, for such metal ions as Cu(II), Pb(II) and Cd(II) toward chelating resins (IRC748 and NDC702) similarly containing iminodiacetic acid group but diverse pore structures, are systematically performed and deeply exploited. The physicochemical characteristics of both IDA-chelating resins are thoroughly explored by EA, FT-IR, SEM-EDX and PSD. Langmuir isotherm and pseudo-second-order equation could satisfactorily describe the batch experimental data, based on which the equilibrium and kinetic parameters are calculated and compared. The adsorption capacities follow the order of Cu(II)>Pb(II)>Cd(II), due to the complicated impacts of metal ion electronegativity as well as resin pore textures. In the contrast of single and binary adsorption performances, more reduction of Cd(II) than Cu(II) is expectably investigated with the coexistence of competitive ion since the less affinity and hence weak competition of the former onto solid-phase. Using aqueous solution of 15 wt% HCl, nearly 100% recovery of Cu(II) and Cd(II) from IDA-resins could be strictly achieved in the column-tests. Furthermore, a schematic illustration of possible pore structure has been proposed and simulated. Meanwhile, the interaction mechanisms are thereby deduced and evidently confirmed by FT-IR as well as SEM analysis.

Study on the removal of iron and manganese in groundwater by granular activated carbon

One of the problems related to groundwater is the reddish colour caused by the presence of ferrous and manganese. Initially, this colour cannot be seen but after it has been exposed to the air, the oxidation of groundwater will promote the precipitation of ferrous and manganese. Eventually, the groundwater turns into reddish in colour. Batch test had been carried out to determine the potential and the effectiveness of granular activated carbon (GAC) in removal of ferrous and manganese from water. The test was conducted by mixing certain amount of GAC with 200 mL sample solution and shook for 6 h in room temperature to achieve an equilibrium. The two most common adsorption equations, Freundlich and Langmuir adsorption isotherms, were used in the study to verify the adsorption performance. From interpretation of the equations, the Langmuir adsorption isotherm was found to fit the experimental data better than that of the Freundlich adsorption isotherm. This shows that the relatively high ambient temperature allowed only monolayer adsorption to occur between the adsorbate and adsorbent. According to Langmuir adsorption isotherm’s assumption, the bonding that was established between the adsorbent and adsorbate are chemically bonded which known as chemisorption. In this study, the adsorption capacity of Fe(II) and Mn(II) were 3.6010 and 2.5451 mg/g, respectively. Therefore, the adsorption capacity for Fe(II) was higher than Mn(II). The main factors that contribute to difference adsorption capacity of Fe(II) and Mn(II) onto GAC are due to ionic radius and electronegativity of metal ions.

A model for the adsorption of single metal ion solutes in aqueous solution onto activated carbon produced from pecan shells

Adsorption isotherms for activated carbon made from pecan shells have been obtained at 25 °C and an approximate pH of 3 for a number of metal ion solutes. It was found that the Slips and Freundlich equations were satisfactory for explaining the experimental data. The correlation of metal ion adsorption with the solute parameters of metal ion electronegativity and first stability constant of the metal hydroxide was investigated. In the case of most of the metal ions studied, higher electronegativities and stability constants corresponded to the higher adsorption levels of metal ions onto the activated carbon. A correlation was developed that predicts the constants of the Freundlich equation from the selected parameters of the metal ions, and thus can predict the adsorption isotherms at constant pH. The developed correlation gives results with acceptable deviations from experimental data. A procedure is proposed for obtaining similar correlations for different conditions (temperature, pH, carbon type and dosage). The ratio of equivalent metal ions adsorbed to protons released is calculated for the studied metal ions over a range of concentrations. In most cases, particularly at low concentrations, this ratio is close to one, confirming that ion exchange of one proton with one equivalent metal ion is the dominant reaction mechanism.

Organic electroluminescent devices using alkaline-earth fluorides as an electron injection layer

We investigated the properties of organic electroluminescent (EL) devices using alkaline-earth fluorides as an electron injection layer, and found that the alkaline-earth fluorides are desirable materials to reduce the turn-on voltage of the EL devices with Al cathode. In the devices using the fluorides as the electron injection layer, we found that the turn-on voltage can be associated with electronegativity of metal ion of the fluoride; the fluoride with a low electronegativity metal ion results in lowering the barrier height at the organic/Al interface and enhanced the electron injection.

Variation of monolayer behaviour and molecular packing in zinc arachidate LB films with subphase pH

Monolayer characteristics and multilayer LB films of zinc arachidate (ZnA) have been studied as a function of subphase pH in the range 4.9–8.0. The monolayer stability was found to be strongly dependent on the subphase pH. Measurement of bilayer spacings in transferred multilayers using X-ray diffraction revealed that depending on subphase pH, three types of molecular packing arrangements corresponding to alkyl chain tilt angles of 0°, 19° and 31° are possible in ZnA multilayers. In certain ranges of subphase pH, more than one type of packing arrangements were found to coexist. These results suggest that the packing arrangement in ZnA multilayers is significantly affected by the properties of the monolayer at the air–water interface and may not be simply related to metal ion electronegativity.

Basic Metal Oxides as Co-Catalysts in the Conversion of Synthesis Gas to Methanol on Supported Palladium Catalysts

The catalytic behavior of Pd catalysts supported on ultrapure silica and promoted with basic metal oxides was investigated in the hydrogenation of CO and CO2to methanol at high pressure. In contrast to previous claims, Pd on very pure silica produced hardly any methanol from CO and H2or CO2and H2, while doping with basic additives led to a high activity. Molecular adsorption of CO or CO2and the availability of activated hydrogen are not sufficient to form methanol; basic metal oxides are needed to give Pd a high methanol activity. The promoting effect on the silica-supported Pd catalysts and the absence of a promoting effect for alumina-supported Pd catalysts suggest that the basic oxide additives must be close to or in contact with the Pd particles to be effective in methanol synthesis. The rate enhancements for methanol formation of the metal oxides followed a volcano curve when plotted as a function of the metal ion electronegativity, with a maximum for metal oxides with a moderate basic nature. Calcium and lanthanum were best for CO hydrogenation, and barium and lanthanum were best for CO2hydrogenation. In contrast to Cu/ZnO, the methanol activity of Ca/Pd/SiO2increased with increasing CO content in a CO–CO2–H2mixture, suggesting that CO rather than CO2is the main carbon source for methanol.

Decomposition of Methanol over Alumina Supported Rhodium Catalysts

The decomposition of methanol was investigated over a variety of alumina (Al2O3) supported rhodium (Rh) catalysts. Decomposition as well as dehydration took place in the reaction of methanol over Rh/Al2O3 catalyst. Pyridine adsorption during the reaction revealed that Rh was active sites for the decomposition, and Al2O3 was those for the dehydration.When base metals were added to Rh/Al2O3, the selectivity for the decomposition increased with lowering electronegativity of metal ions added. Thus, alkali metals such as potassium (K) gave the highest selectivity for the decomposition. Further addition of some base metals to Rh-K/Al2O3 selectively promoted the decomposition of methanol.

Regularity in Catalytic Properties of Various Promoted 61203 for the Vapor-Phase Oxidative Dehydrogenation of Isobutylaldehyde

Vapor-phase oxidative dehydrogenation of isobutylaldehyde over various B403 catalysts promoted with alkali metal oxides or alkaline earth metal oxides has been investigated to the reaction mechanism of methacrylaldehyde formation and the effect of addition of these oxides on the catalytic activity of Bi2O3. Almost selective formation of methacrylaldehyde was observed during the reaction of isobutylaldehyde with these promoted Bi2O3 in the absence of gaseous oxygen; the Bi2O3 containing these oxides at 10-15 atm% was most effective for methacryl- aldehyde formation. Furthermore, the conversion of isobutylaldehyde and the yield of methacrylaldehyde at zero reaction time increased with the decrease in the electronegativity of metal ion added to Bi2O3. Similar regularity was also observed in the catalytic oxidative dehydrogenation of isobutylaldehyde and the catalytic oxidation of carbon monoxide over these oxides. In the catalytic oxidative dehydrogenation over Cs20-Bi2O3 (Cs=15 atm %), the yield of methacryl- aldehyde was 47.1%, the selectivity being 65.5% at 450°C. Formations of carbon dioxide and of methacrylaldehyde were kinetically discussed on the basis of the regularity observed, and participation of lattice oxygen rather than oxygen species adsorbed in the oxidative dehydrogenation was proposed. Metal oxides added probably control the strength of Bi-O bond according to the electronegativities of metal ions.

Stereochemical Studies of Elimination Reactions of 2-Bromobutane and 2,3-Dibromobutane over Bivalent-Ion Exchanged Silica Gels

Abstract Elimination reactions of 2-bromobutane and 2,3-dibromobutane over silica gels in which silanol protons on the surface were exchanged with bivalent ions such as Ba(II), Ca(II), Mg(II), and Ni(II) have been investigated. Dehydrobromination of 2-bromobutane was found to proceed mainly with syn elimination. Debromination by anti mode and non-stereospecific dehydrobromination were observed for 2,3-dibromobutane. The catalytic activities of these silica gels exhibit reversed volcano-type patterns when they are plotted against the electronegativity of metal ion together with those of alkali-ion exchanged silica gels. Reaction intermediates consistent with the stereochemistry observed are a s-butyl cation and a bromonium ion, respectively for 2-bromobutane and 2,3-dibromobutane.

ChemInform Abstract: ALKYLATION OF PHENOL WITH CYCLOHEXENE

AbstractDie Alkylierung von Phenol mit Cyclohexen in Gegenwart von kationvariierten Zeolith‐Katalysatoren wird untersucht.

Alkylation of Phenol with Cyclohexene

The alkylation of phenol with cyclohexene in the vapor phase has been studied over the cation-exchanged X zeolite catalysts. Because of the dealkylation of products, the catalytic activity decreased with rising reaction temperature. The yield of cyclohexylphenol increased linearly with increase in the amount of acid. Furthermore, the catalytic activity decreased by the addition of pyridine. However, the order of catalytic activity for alkylation of phenol with cyclohexene was not in accord with that for the cracking of cumene. On the other hand, the volcanoshape relation was observed between the catalytic activity for alkylation of phenol with cyclohexene and the electronegativity of metal ion in the catalyst. On the basis of these results, it is concluded that the alkylation reaction proceeds on the acid sites, and the active sites are the surface protons and the metal ions of the catalyst.

ChemInform Abstract: ISOMERIZATION OF 2‐PINENE OVER MONOHYDRATES OF METAL SULFATES

Catalytic activity of the monohydrates of various metal sulfates for the isomerization of 2-pinene was found to be related to the infrared wave numbers of the rocking mode of the water of crystallization and the transition temperatures from the monohydrates to the anhydrates, but not to the electronegativity of metal ions.

Isomerization of 2-Pinene over Monohydrates of Metal Sulfates

Abstract Catalytic activity of the monohydrates of various metal sulfates for the isomerization of 2-pinene was found to be related to the infrared wave numbers of the rocking mode of the water of crystallization and the transition temperatures from the monohydrates to the anhydrates, but not to the electronegativity of metal ions.

The Catalytic Activity and Selectivity of Acidic Metal Salt Catalysts for n-Butene Isomerization

Abstract Double-bond isomerization of n-butenes over several supported acidic metal salts such as metal sulfates, perchlorates and phosphates including free acids has been investigated at 60°C with the butene pressure of 14 cmHg. The activity and the selectivity of cis-trans isomerization over double-bond migration increased monotonously, as the acid strength of catalysts increased. Acid strength, activity and selectivity of metal salt catalysts increased with the electronegativity of metal ion where free acids were the most strongly acidic and active catalysts (H+>Al3+>Ni2+>Mg2+>Na+), and for a given metal ion they increased with the acid strength of the conjugated acid (ClO4−>SO42−PO43−CH3COO−). The activity and selectivity were explained on the basis of a sec-hutyl carbonium ion mechanism which appears more concerted over weak acids. The active sites for the reaction were suggested to be protonic acid sites closely connected to acid radical.

Photoconduction of Metal 8-Hydroxy-Quinolinate

The photoconduction of metal 8-hydroxy-quinolinate (Me(C 9 H 6 NO) 2 , where Me=Cu, Pd, Zn, Cd and Mg) was measured. The spectral response of the photoconduction was found in lower wavenumber region than the optical absorption bands. There is a linear relation between the wavenumber of the photoconductive peak and the electronegativity of metal ion. It seems that the photoconduction in the low wavenumber region arises from an intrinsic excitation of the constituent molecule.

Polymerization of vinyl monomers with salts of bronsted acids

AbstractThe polymerization of vinyl monomers (N‐phenylmaleimide, acrylamide, acrylonitrile, methyl vinyl ketone, methyl methacrylate, vinyl chloride, and styrene) with sodium salts of Brønsted acids (sodium cyanide, sodium nitrite, sodium hydroxide, etc.) were investigated at 0°C in dimethylformamide. N‐Phenylmaleimide, acrylonitrile, and methyl vinyl ketone were found to undergo polymerization with sodium cyanide, however the other monomers were not polymerized with this salt. In the polymerizations of acrylonitrile and N‐phenylmaleimide with sodium cyanide, the rates of the polymerizations were found to be proportinal to the initiator concentration and to the square of the monomer concentration. The activation energy of acrylonitrile polymerization was 3.7 kcal/mole, and that of N‐phenylmaleimide ws 3.0 kcal/mole. The results of the copolymerization of acrylonitrile with methyl methacrylate at 0°C in dimethyl‐formamide with sodium cyanide confirm that these polymerizations proceeded by an anionic mechanism initiated by the Michael addition reaction of the monomers with the salts. In these polymerizations, the monomer reactivity increased with increase in the e values. The initiation ability of sodium salts increased with increasing pKa of the conjugate acids and with decreasing electronegativity of metal ion in the series of lithium, sodium, and potassium cyanide. The polymerizations took place only in aprotic polar solvents, and did not occur in weak polar solvents and in protonic solvents.