Adsorption behavior of various metals on a weakly basic anion-exchange resin in sulfuric acid media

A systematic study is presented on the adsorption behavior of some 20 metals on a weakly basic condensed phenol resin, Amberlite CG-4B, in sulfuric acid media. The distribution coefficients were determined over a sulfuric acid concentration range of 0.005 M to 2 M. The metals adsorbed are similar to those which exhibit strong adsorption on a strongly basic resin, but the magnitudes of the distribution coefficients and the adsorption sequences differ considerably between the two types of the resin. Several two- and three-component separations of analytical interest are possible. A new method for the separation of titanium(IV) is described; this is based on its high adsorption on CG-4B from sulfuric acid media containing hydrogen peroxide.     

Separation of platinum and palladium from base metals with a weakly basic cellulose ion exchanger

Platinum(IV) and palladium (II) are strongly adsorbed on the weakly basic cellulose ion exchanger DEAE from dilute thiocyanate media, while most other metal ions do not show any marked tendency to adsorb from the same media. It is possible to separate and concentrate the noble metal ions from a large quantity of base metals such as iron, cobalt, nickel, copper, zinc and lead. As little as 1 mg of platinum(IV) and/or palladium (II) can be quantitatively separated from as much as 20–25 g of base metals on a small column of DEAE (thiocyanate form). The noble metal ions adsorbed are easily stripped from DEAE.     

Ion-exchange behaviour of metals on deae-cellulose in methanol-thiocyanate-hydrochloric acid media

Only a few metals can be adsorbed on DEAE-cellulose from aqueous thiocyanate-chloride media. However, several metal ions, including Cu(II), Zn, Cd, In, Bi and U(VI), exhibit enhanced adsorption on DEAE-cellulose from methanol-thiocyanate-hydrochloric acid mixtures. The distribution coefficients for these metals are given as functions of methanol, ammonium thiocyanate and hydrochloric add concentration. Differences in adsorption among metals permit many useful separations, including those of two-, three- and four-component mixtures, on short columns containing 1-1.5 g of DEAE-cellulose.     

Thin-layer chromatography of a number of metals on cellulose phosphate in phosphoric acid media

Summary The thin-layer chromatographic behavior of 48 metals on cellulose phosphate (P-cellulose), an interediately acidic cation exchanger, has been examined systematically in aqueous phosphoric acid media (0.01–2 M). Differences in the R_f values among the metals in 1 M phosphoric acid are large enough to permit multicomponent separations of analytical interest.     

Equilibrium sorption of sulfuric acid by weakly basic polyacrylic anionites

The sorption of sulfuric acid on Amberlite IRA 67 and (2) Lewatit VP.OC.1072 weakly basic polyacrylic anionites in the free-base form was studied. It was demonstrated that the bisulfate form of the anionites was not produced. In contrast to the sorption of hydrochloric acid, the solution of resinates formed during the sorption of sulfuric acid is nonideal. A model of exchange of doubly charged anions on fixed singly charged ion-exchange sites of polyacrylic anionites was developed based on the theory of ion-exchange equilibria. The model was used to analyze the isotherms of equilibrium sorption of sulfuric acid on IRA 67 and Lewatit VP.OC.1072 anionites in the free-base form.     

Adsorption of acid and basic dyes on NiO-SiO2 composites

A series of composites containing 2.5–21.0% NiO on a surface of macroporous silica is synthesized. The specific surface area of the composites measured by the thermal desorption of nitrogen decreases with an increase in the NiO content from 24 for the original silica carrier to 16 m²/g the for composite containing 21.0% NiO. The basic dye, methylene blue (MB), is only adsorbed on SiO₂ in water solutions, while acid blue anthraquinone (ABA) is only adsorbed on the NiO. The effective specific surface area Seff and effective diameters D _eff of NiO nanoparticles are calculated from the adsorption isotherms of ABA on NiO composites and on NiO synthesized without a carrier. S _eff of NiO nanoparticles decreases from 76 to 42 m²/g and D _eff increases from 8 to 14 nm with rising NiO content in the composites. The NiO nanoparticles synthesized without a carrier are characterized by the lowest S _eff (30 m²/g) and the largest D _eff (20 nm).     

Anion-exchange behaviour of metals on deae-cellulose in hydrochloric acid-acetic acid media

The anion-exchange behaviour of 35 metal ion species on a weakly basic cellulosic ion-exchanger (DEAE-cellulose) in mixed hydrochloric acid-acetic acid media has been investigated. The sorption of metal chloro-complexes on DEAE-cellulose is greatly enhanced with increasing concentration of acetic acid. Differences in sorbability of metals allow many useful analytical separations to be conducted on short columns, containing approximately 1 g of DEAE-cellulose(Cl(-)). Procedures for the chromatographic separations of two-, three-, four- and five-component mixtures are given.     

Anion-exchange behaviour of a number of metal ions on DEAE-cellulose in hydrobromic and hydriodic acid media

Summary The adsorption behaviour of 48 metal ions on DEAE-cellulose layers has been investigated in aqueous hydrobromic and hydriodic acid media. R_F values are given as a function of the hydrobromic and hydriodic acid concentration over the ranges 0.01–6 mol dm^–3 and 0.01–3 mol dm^–3, respectively, and are compared with those obtained with Avicel SF. R_F spectra are comparatively simple in both media, reflecting the strong affinity of the bromide and iodide ions to the DEAE-cellulose phase. Pd, Pt, Re, Au and Hg are distributed chromatographically in either system, while most other metal ions exhibit rather extreme R_F values of near unity or zero. Therefore, the selectivity of the systems is particularly high for Pd, Pt, Re, Au and Hg, providing the possibility of their excellent selective separations.     

Thin-layer chromatographic behavior of a number of metals on carboxymethyl-cellulose in sulfuric acid and ammonium sulfate media

Summary The thin-layer chromatographic behavior of 57 metals on a weakly acidic cation exchanger, carboxymethyl (CM) cellulose, has investigated systematically in sulfuric acid (0.01–1.0 M) and the acidic ammonium sulfate media. Thin-layer plates of a microcrystalline cellulose, Avicel SF, were also used to compare with the chromatographic behavior of the metals in the acidic sulfate system. The Rf values obtained for many metals tested on CM-cellulose plates increase with increasing concentration of sulfuric acid. Most of metals tested are distributed chromatographically on the CM-cellulose in the low acid concentration. The characteristic retention of many metals, including sulfato-complexes forming metals, on the CM-cellulose can be observed in ammonium sulfate solutions of a low concentration of the acid. Useful multicomponent separations of analytical interest on CM-cellulose layers are presented to demonstrate the use of Rf measurements for predicting separations in the acid and the acidic ammonium sulfate systems.     

Anion-exchange behaviour of various metals on DEAE-cellulose in mixed acetic acid-nitric acid media

A number of nitrato complexes of metals have been found to be adsorbed on DEAE-cellulose from mixed acetic acid-nitric acid media, although none can be adsorbed from aqueous nitric acid solutions. The distribution coefficients of Sc, Mo, La, Sm, W, Re, Bi, Th and U are given as functions of acetic acid and nitric acid concentrations (sometimes in the presence of hydrogen peroxide to prevent hydrolytic precipitation). For 25 other metals column adsorption behaviour is described for a 90% acetic acid-10% 7.6M nitric acid mixture. Favourable differences in the distribution coefficients allow useful separations such as FeMoW and USmMoBiTh, to be achieved.     

The dynamics of sorption of sulfuric acid by weakly basic polyacrylic anion exchangers

The nonequilibrium dynamics of sorption of sulfuric acid by free base forms of Amberlite IRA-67 and Lewatite VP.OC.1072 weakly basic anion exchangers is studied. It is established that, in hydrodynamic regimes of filtration, which are typical of OH filters of the first stage of water-desalting plants, the limiting stage of sorption kinetics is inside diffusion. It is concluded that the process is correctly described by an asymptotic solution to the inside-diffusion model of sorption dynamics. Original Russian Text ? A.V. Mamchenko, T.V. Kushnir, 2009, published in Zhurnal Fizicheskoi Khimii, 2009, Vol. 83, No. 5, pp. 967–971.     

Adsorption of propylene on platinum-group metals

Propylene adsorption and transformation on metals of the Pt group have been studied. Propylene chemisorption decreases in the following series: Rh>Pt>Ir>Ru>Pd and it is accompanied by the formation of -allyl and -complexes. The lowest conversions of propylene are observed on Pt, next are Ru, Rh, Ir and Pd.

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Pt-. , : Rh>Pt>Ir>Ru>Pd - -. Pt, Ru, Rh, Ir, Rd.

     

Potentiometric titrations in non-aqueous solution : Anomalous behaviour of weak oxygen acids in inert and weakly basic solvents

A number of carboxylic acids, phenols and certain related compounds have been found to yield anomalous titration curves in inert and weakly basic solvents. Amongst the effects observed are reproducible potential rises in the region of half-neutralization and irrcproducible potential drops often at stages of the titration corresponding to simple fractions of total neutralization.An investigation has been made into the influence of the basic and amphiprotic character of the solvents, of steric hindrance in the acid molecules, of substitution of —OH (in phenols) by —SH, and of —COOH (in carboxylic acids) by —SOOH, and of the type of electrodes on the occurrence and type of anomalies.These, and the other observed anomalies are interpreted.     

The chromatography of a number of metals on cellulose phosphate layers in sulfuric acid and ammonium sulfate media

Summary The thin-layer chromatographic behavior of 58 metals on an intermediately acidic cation exchanger, cellulose phosphate (P-cellulose), has been surveyed systematically in sulfuric acid and ammonium sulfate media (0.01–2.0 M). The R_f values for many bivalent and univalent metal ions on P-cellulose plates increase with increasing concentration of sulfate ions. Howerver, manganese (II), arsenic (III) and selenium (IV) are not adsorbed on the cellulose to any great extent. Beryllium (II) and other metals, which form either strong phosphate complexes or insoluble sulfate precipitates, are strongly retained on the P-cellulose. The thin-layer chromatographic separations of various metal ions of analytical interest were accomplished to demonstrate the use of R_f measurements for predicting separations in the acid and the sulfate media.     

Adsorption of comb copolymers on weakly attractive solid surfaces

In this work continuum and lattice Monte Carlo simulation methods are used to study the adsorption of linear and comb polymers on flat surfaces. Selected polymer segments, located at the tips of the side chains in comb polymers or equally spaced along the linear polymers, are attracted to each other and to the surface via square-well potentials. The rest of the polymer segments are modeled as tangent hard spheres in the continuum model and as self-avoiding random walks in the lattice model. Results are presented in terms of segment-density profiles, distribution functions, and radii of gyration of the adsorbed polymers. At infinite dilution the presence of short side chains promotes the adsorption of polymers favoring both a decrease in the depletion-layer thickness and a spreading of the polymer molecule on the surface. The presence of long side chains favors the adsorption of polymers on the surface, but does not permit the spreading of the polymers. At finite concentration linear polymers and comb polymers with long side chains readily adsorb on the solid surface, while comb polymers with short side chains are unlikely to adsorb. The simple models of comb copolymers with short side chains used here show properties similar to those of associating polymers and of globular proteins in aqueous solutions, and can be used as a first approximation to investigate the mechanism of adsorption of proteins onto hydrophobic surfaces.     

Adsorption of mixtures of vapors on zeolites

Conclusions The adsorption of a binary mixture of vapors[CHCl₃-(C₂H₅)₂O]on zeolite NaX was studied at 60 and 72°. The thermodynamic properties of the adsorption solutions formed were described.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1309–1311, July, 1964     

Sorption of levulinic acid onto weakly basic anion exchangers: equilibrium and kinetic studies

The equilibrium and dynamics of levulinic acid sorption on two weakly basic anion exchangers, in free base form, in single-component aqueous solutions were investigated. Adsorption isotherms such as Langmuir, Sips, Radke-Prausnitz, and Toth were applied to correlate the experimental data in the temperature range 285-315 K. Modeling results showed that the Toth model is the best one to correlate the sorption isotherms. The resulting Toth equations were used with the Clausius-Clapeyron equation to determine the isosteric heat of sorption. The sorption kinetics was experimentally measured via a completely stirred finite-bath batch experiment under different initial concentrations and at varying solution temperatures. The pseudo-second-order kinetic model and the Elovich equation were used to represent the kinetic data and the equation parameter values were also evaluated. The pseudo-second-order equation cannot simulate the experimental kinetic data, while the Elovich equation fitted the sorption dynamic data very well under all the operating conditions studied. Finally, the apparent activation energy of sorption was also determined.