Kinetics of rhenium sorption from weakly basic macroporous and gel anion exchangers Purolite A170 and Purolite A172 from sulfuric acid solutions

Effect of the grain size of anion exchangers, agitation intensity, and temperature on the kinetics of rhenium sorption on weakly basic macroporous and gel anion exchangers Purolite A170 and Purolite A172 from a 1 M H₂SO₄ solution was studied.     

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.     

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.     

Remazol Black B removal from aqueous solutions and wastewater using weakly basic anion exchange resins

In this study, the use of the weakly basic anion exchange resins of phenol-formaldehyde (Amberlyst A 23), polyacrylate (Amberlite IRA 67) and polystyrene (Lewatit MonoPlus MP 62) matrices for removal of the reactive dye Remazol Black B (RBB) from aqueous solution and wastewater were investigated. RBB sorption on the anion exchangers was a time dependent process. Color reduction percentiles of 75.2, 33.9 and 25.1% in wastewater treatment were found after 216 h of phase contact time with Lewatit MonoPlus MP 62, Amberlyst A 23 and Amberlite IRA 67, respectively. Inorganic salts and anionic surfactant action influenced RBB uptake by the anion exchangers. The amounts of dye retained by the anion exchangers increased with a rise in temperature. The maximum sorption capacities calculated from the Langmuir model were 66.4, 282.1 and 796.1 mg g⁻¹ for Amberlite IRA 67, Amberlyst A 23 and Lewatit MonoPlus MP 62, respectively. Regeneration of phenol-formaldehyde and polystyrene resins were possible using 1 M NaOH, 2 M KSCN, 1M KSCN in 40–60% methanol as well as 1 M NaOH in 60% methanol.      

The equilibrium sorption of sulfuric acid by weakly basic polyacrylic anion exchangers synthesized on the basis of polyamines

The equilibrium ion-exchange sorption of sulfuric acid by the free base form of weakly basic polyacrylic anion exchangers with the gel (Relite MG1) and porous (Relite MG1/P) structures was studied. It was proved that the bisulfate variety of the anion exchangers did not form. Solutions of resinates were found to be nonideal. Their nonideality was analyzed in terms of the theory of exchange equilibria to suggest a model of the exchange of doubly-charged anions on fixed polyamine exchange centers of Relite MG1 and Relite MG1/P anion exchangers. The type of the ion was found to have no effect on sorption parameters.     

Sorption of aldonic acids from ethyl alcohol-water solutions on anion exchangers

Aldonic acids can be retained quantitatively from ethyl alcohol-water solutions by means of anion exchangers in the sulfate form. After the sorption step the aldonic acids can be easily displaced by washing with water. The sorption is explained by a partition mechanism of the same type as demonstrated in earlier work with strongly polar non-electrolytes. Precautions have to be taken to prevent uptake by means of an ion exchange mechanism. The method permits a separation from exchangeable anions and from non-adsorbable solutes.     

The hydration of MG-1 weakly basic anion exchanger in the basic and citrate forms

The hydration of MG-1 weakly basic anion exchanger in the basic and citrate forms was studied by IR spectroscopy and optical microscopy. It was found that the OH^? from of the ion exchanger contained the largest amount of water with different degrees of binding.     

Elution and analysis of residual chloride from anion exchangers

Summary Strong anion exchangers can be transformed to the hydroxyl forms by elution with analytical grade sodium hydroxide. The residual chloride contents remain above the 0.1% level. Such chloride amounts can rapidly and easily be determined with a radiochemical method using ^110mAg as tracer. This method was compared with neutron activation and potentiometric titration methods.

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Zusammenfassung Starke Anionenaustauscher können durch Spülen mit Natronlauge in die Hydroxylform übergeführt werden. Der Rest-Chloridgehalt bleibt jedoch immer über 0.1%. Diese Chloridgehalte können unter Zuhilfenahme des Isotopes ^110mAg mit einer radiochemischen Methode bestimmt werden. Vergleiche mit potentiometrischen Titrationen und Neutronenaktivierungsanalysen werden gegeben.

     

Selective extraction and concentration of dispersed copper from dilute solutions of copper and zinc ions with weakly basic aminoanionites

The possibility of selective extraction and multiple concentration of copper in the form of ultrafine precipitate from dilute Cu²⁺-Zn²⁺ solutions by using a suitable sorbent and an effective mode of its regeneration was demonstrated. The extraction was performed in the dynamic mode in column-type reactors filled with an aminoanionite as a selective complexing sorbent, the regeneration of which was conducted by chemical reduction of Cu²⁺ in the ionite after its saturation. It was established that saturation-reduction cycles repeated many times result in the accumulation of metallic copper at the surface and in the bulk of the sorbent. The mechanism of the process includes the formation of complexes of copper and zinc with amino groups of the ionite and the subsequent displacement of Zn²⁺ ions from the anionite due to its higher affinity to Cu²⁺ ions followed by the conversion of Cu²⁺ ions to an unsorbable form (dispersed metallic copper). It was demonstrated that the presence of dispersed copper stimulates the additional sorption of Cu²⁺ ions via redox conproportionation. This method makes it possible to obtain a degree of concentration of copper ions in three cycles >300% higher than that attainable in the purely ion-exchange mode (without chemical reduction).     

Recovery of rhenium from sulfuric acid solutions with activated coals

Equilibrium and kinetic characteristics of rhenium sorption from sulfuric acid solutions (pH 2) by activated coals produced from coal raw materials (China) were studied. Constants of the Henry equation describing isotherms of rhenium sorption by activated coals were calculated. The effective diffusion coefficients of rhenium in the coals were determined. The dynamic characteristics of rhenium sorption and desorption were determined for the activated coal with the best capacity and kinetic characteristics.     

Kinetics and exchange behaviour of certain sulphur anions on strongly basic anion exchangers in aqueous KCl medium

The kinetics of the exchange of sulphate and chloride ions on the strongly basic anion exchanger Dowex 1X8, of different particle diameters is investigated. The diffusion coefficient values are calculated by two diferent methods, discussed in the light of the processes governing the exchange reactions encountered, and found to be mainly controlled by particle diffusion. The distribution behaviour of sulphate, sulphite, thiosulphate and sulphide between aqueous KCl solutions of different concentrations and a number of selected anion exchange resins is studied. The data are explained on the premises of the different interactions involved in both aqueous and resineous phases. The effect of the alkali metal chloride molarities in the aqueous phase (LiCl, NaCl and KCl) on the exchange behaviour of the different S-anions is also investigated. The results are interpreted in the light of the water—water interaction and the competition for hydration between the alkali metal cations and the exchanged S-anions.     

Specific features of disposal of sulfuric acid solutions resulted from magnesium silicate decomposition

The photocatalytic activity of crystalline titania nanopowders synthesized in a stream of ultrahigh-frequency discharge oxygen-containing low-temperature plasma was assessed. To this end, oxidation of an organic dye was carried out in UV-irradiated aqueous suspensions of TiO₂ at different concentrations and varied irradiation times.     

Sorption of zinc complex ions from chloride solutions with ion exchangers

To characterize the reaction of zinc ions with anion exchangers of various types, the equilibrium compositions of all the components of the sorption system (zinc salt, hydrochloric acid, and water) and distribution of associated molecules in the resin phase were considered.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 9, 2004, pp. 1456–1461.Original Russian Text Copyright © 2004 by Skorokhodov, Radionov, Goryaeva.     

Dehydration of zinc hydroxide precipitate produced by neutralization of weakly concentrated zinc sulfate solutions with aqueous ammonia

Method for dehydration of zinc-containing products is suggested. The method makes lower the energy expenditure in filtration, drying, and calcination, diminishes the expenditure of reagents, and improves ecological characteristics of the process.     

Extraction of rhenium(VII) with aliphatic alcohols from acid solutions

Extraction of rhenium(VII) with C₇–C₁₀ aliphatic alcohols from HCl and H₂SO₄ solutions was examined. The rhenium(VII) distribution coefficients were examined in relation to the acidity and temperature. The composition of the extracted complexes and the thermodynamic parameters of extraction were determined. The extraction method of recovery and preconcentration of rhenium(VII) from H₂SO₄ solutions with secondary octyl alcohol was tested in the counterflow mode.     

Recovery of rhenium(VII) with triisooctylamine from sulfuric acid solutions

Extraction recovery of rhenium(VII) with triisooctylamine from model sulfuric acid solutions was studied. The effect of the composition of the organic and aqueous phases on the recovery of rhenium(VII) was analyzed, and the composition of rhenium(VII) complexes in the organic phase was determined. The possibility of effective re-extraction of rhenium(VII) from triisooctylamine with ammonia solutions was demonstrated.     

Specific features of the absorption of divalent manganese ions from aqueous solutions by zeolites

Sorption properties of natural zeolites from various Russia’s deposits for the Mn²⁺ ion were studied in comparison with various industrial adsorbents and some minerals. It was demonstrated that the equilibrium sorption capacity of these materials can be raised by their Na⁺-modification. The natural zeolites are advantageous at low Mn²⁺ ion concentrations over synthetic cation exchangers and activated carbons. The sorption capacity of the natural zeolites grows with increasing temperature.     

Paper chromatography of noble metals in mixed chloride-nitrate media with use of solutions of liquid anion exchangers as mobile phases

Summary The chromatographic behaviour of nine noble metals on paper strips impregnated with mixtures of HCl and HNO₃ and developed with solutions of secondary and tertiary amine salts or quatermary alkylammonium salts in organic diluents was investigated. It was found that very sharp separation of the pair Pt–Pd is obtainable at development of chromatograms with 0.1 Aliquat 336 in xylene or with 0.1 mol dm^–3 TOA in kerosene at high concentrations of the acids in the stationary phase. The increase of concentration of HNO₃ in acids mixture decreases the R_F or R_M values for the platinum metals more distinctly than increase of concentration of HCl.     

Influence of sulfate and nitrate uptake from aqueous solutions on surface exchange in Purolite A-520E resin

Removal of nitrate anions from aqueous solutions is the principal goal of many studies concerning water treatment. The ion exchanger capacity to remove nitrate from water was investigated using commercial type A-520E anion exchange resins. The nitrate and sulfate ion exchanger capacity, in static conditions, depends on the concentration of ions and on the pH value of the aqueous solution. The local structural environment exchanged on A-520E has been investigated by scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX) and 2D and 3D atomic force microscopy (AFM). All images of the ion exchanger were obtained before and after contact with solutions that contain NO₃⁻ and SO₄²⁻ separately as well as mixtures of both.     

Wave packet dynamics of photon- and electron-stimulated desorption of ammonia from surfaces

Time-dependent quantum mechanical calculations have been carried out for the photon- and electron-stimulated desorption of ammonia from metal or semiconductor surfaces. The desorption is facilitated by a short-lived complex which excites the N---H₃ inversion mode. The desorption yield and its isotope effect have been obtained from a wave packet on two-dimensional empirical potential energy surfaces. The translational and vibrational distributions of the desorbed ammonia are also calculated. The desorption mechanism includes both direct and predesorption, but the latter predominates. It is shown that the quantum desorption dynamics is much more complex than the simple MGR model.