Search Results

You are looking at 1 - 10 of 978 items for :

  • "ion exchange" x
  • Refine by Access: All Content x
Clear All

Abstract  

The thermodynamic characteristics of proton exchange in SO3H groups of a sulfonated network polymer based on cis-tetraphenylmetacyclophanoctol for Na+, Cu2+ cations from aqueous solutions were considered for the first time. Microcalorimetric measurements of the heat effects of Na+-H+ and Cu2+-H+ exchanges were performed, equilibrium compositions of polymer and solution were determined. The changes of Gibbs energy, enthalpy and entropy of ion exchange were calculated.

Restricted access

Abstract  

Thermogravimetric data were used to calculate the number of acidic Brnsted sites in lamellar α-titanium (α-TiP), γ-titanium (γ-TiP), α-zirconium (α-ZrP) and γ-zirconium (γ-ZrP) hydrogenphosphates. The numbers of acidic sites calculated for these lamellar compounds were 7.81, 5.67, 6.33 and 5.56 for α-TiP, γ-TiP, α-ZrP and γ-ZrP, respectively. These values are in good agreement with those found through potentiometric titration. The data obtained prove that thermogravimetric measurements can be used as a reliable analytical tool to follow the ion-exchange capacity of this kind of crystalline lamellar compounds.

Restricted access

Improved inorganic ion-exchangers

I. Systems with organic polymers as binding materials

Journal of Radioanalytical and Nuclear Chemistry
Authors: J. Stejskal, J. Soukup, J. Doležal, and V. Kouřím

Abstract  

The use of organic polymers as binding agents for inorganic ion-exchangers has been studied. Poly-vinyl acetate and polystyrene polymers were applied to ammonium phosphomolybdate and zinc ferrocyanide. The method of preparation and hydromechanical properties of the resulting materials in ion-exchange columns are described. The materials were used for caesium removal from simulated Purex high-level radioactive waste solutions. The break-though capacities and results of repeated sorption-elution cycles are presented.

Restricted access

Improved inorganic ion-exchangers

II. Ammonium molybdophosphate—Silica gel system

Journal of Radioanalytical and Nuclear Chemistry
Authors: J. Doležal, J. Stejskal, M. Tympl, and V. Kouřím

Abstract  

The possibility of using the sol-gel method for preparation of inorganic ion-exchangers with a silica gel matrix has been demonstrated on the ammonium molybdophosphate-silica gel (AMP-SG) system. For the preparation of the ion-exchanger a sodium silicate solution, containing AMP and components to cause gelling to silica gel after increase of the temperature of the solution, is poured into a hot stirred silicone oil. The solution forms droplets, which are filtered off after their gelling, washed and dried. Beads containing 65 wt.% of AMP per gram of dry material have been prepared by this method and tested in ion-exchange columns for caesium removal from nitric acid solutions. Caesium may easily be desorbed with ammonium chloride or nitrate solutions. The ion-exchanger is suitable for long-time reversible column operation, having not only good chemical, thermal and radiation stabilities but also good mechanical and hydrodynamic properties and resistance to abrasion. It combines the advantage of the good kinetics of ion-exchange obtained with microparticles of precipitated inorganic ion-exchanger, with the low flow resistance of large particles.

Restricted access

Improved inorganic ion-exchangers

III. Polyantimonic acid and mixed sulphate-silica gel systems

Journal of Radioanalytical and Nuclear Chemistry
Authors: V. Kouřím, J. Stejskal, and M. Santarová

Abstract  

A series of mixed sulphates of lead and calcium as well as the polyantimonic acid have been tested for their ability to isolate strontium from acidic solutions. The sol-gel method was used for preparation of particles with a silica gel matrix. Both polyantimonic acid and lead-calcium sulphate were found to be promising ion-exchangers.

Restricted access

Abstract  

This paper discusses the changes in the structure and thermal reduction of nanosize hexagonal ammonium tungsten bronze (HATB), (NH4)0.33−xWO3−y, which were caused by K+ ion exchange (doping) and studied by XRD, XPS, 1H-MAS NMR, FTIR, SEM and TG/DTA-MS. Comparison of the cell parameters of undoped and doped HATB revealed that both a and c cell parameters decreased after the ion exchange reaction, which showed that smaller K+ ions partly replaced the larger NH4 + ions in the hexagonal channels of HATB. After the reaction, from the hexagonal channels less NH3 evolved, which also supported the incorporation of K+ ions into the hexagonal channels.

Restricted access

Introduction Inorganic ion exchangers have been of great interest for the last six decades, zirconium(IV) phosphate being the most extensively studied material [ 1 , 2 ]. Next to this are the tin(IV)-based materials, due to

Restricted access

M. Qureshi, K.G. Varshney (eds.), Inorganic Ion-Exchangers in Chemical Analysis, CRC Press, Boca Raton, 1991. Inorganic Ion-Exchangers in Chemical Analysis 1991

Restricted access

Ion exchange in organic solvents

IV. Separation of plutonium from uranium in 30% TBP on amberlyst-15

Journal of Radioanalytical and Nuclear Chemistry
Authors: P. Mayankutty, N. Pillai, S. Shinde, and M. Nadkarni

Abstract  

Studies on the partitioning of plutonium from 30% TBP by ion-exchange absorption on macroporous cation exchanger Amberlyst-15 have been described. Detailed loading experiments indicate that the resin absorbs plutonium in preference to uranium from loaded organic phase at low organic phase acidities (around 0.2M). Absorption behaviour of some fission products on the resin in 30% TBP is also reported. Possibility of using this procedure as an alternate method for plutonium partitioning from IAP stream of Purex process has been discussed.

Restricted access

. 1997 15 831 M. Qureshi and K.G. Varshney (Eds) Inorganic Ion-Exchangers in Chemical Analysis, CRC

Restricted access