Ion-exchange properties of Zn4(OH)6(SO4) 2.5H2O

The aim of the present study is to check the possibilities for ion exchange of a new zinc-hydroxy-sulfate-hydrate phase, Zn4(OH)6SO4·2–2.25H2O. The new zinc hydroxy sulfate hydrate phase was obtained by mixing of 0.5 g of Zn5(OH)8(NO3)2.2H2O and 50 ml of 1M Na2SO4 for 48h at room temperature and pH of the solution between 5–7. Ion-exchange properties were investigated by mixing of 0.2 g Zn4(OH)6(SO4) 2.5H2O with 20 ml water solution of NaCl, CaCl2 or SrCl2 with different concentrations (0.5М, 1М, or 2M) for different time (24h, 48h and 72h) at room temperature. The pH of the solutions varied in the range 6–8. The new phase has exchange properties potentials, like other zinc hydroxy sulfate hydrates composed of octahedral-tetrahedral layers. The results obtained for the kinetics of ion-exchange reactions are additional useful data for the solving of the structure of the new zinc-hydroxy-sulfate-hydrate phase in the future.

Nonlinear Inverse Problem for an Ion-Exchange Filter Model: Numerical Recovery of Parameters

This paper considers the problem of identifying unknown parameters for a mathematical model of an ion-exchange filter via measurement at the outlet of the filter. The proposed mathematical model consists of a material balance equation, an equation describing the kinetics of ion-exchange for the nonequilibrium case, and an equation for the ion-exchange isotherm. The material balance equation includes a nonlinear term that depends on the kinetics of ion-exchange and several parameters. First, a numerical solution of the direct problem, the calculation of the impurities concentration at the outlet of the filter, is provided. Then, the inverse problem, finding the parameters of the ion-exchange process in nonequilibrium conditions, is formulated. A method for determining the approximate values of these parameters from the impurities concentration measured at the outlet of the filter is proposed.

History, Introduction, and Kinetics of Ion Exchange Materials

During the last few decades, ion exchange materials have evolved from laboratory tool to industrial products with significant technical and commercial impact. The current paper briefly summarizes the history of the development of the ion exchange materials. The paper defines the ion exchange materials and their types. The paper signifies the kinetics involved in the ion exchange process with description of factors affecting the rate of ion exchange. The mechanism of ion exchange has also been delineated through schematic diagram, illustrating that there are two types of diffusion, film and particle controlled diffusion. A brief of mathematical approach for kinetics of ion exchange has also been incorporated.

SYNTHESIS OF HYDROTALCITE Zn-Al-SO4 AS ANION EXCHANGER AND ITS APPLICATION TO TREAT OF POLLLUTANT CONTAINED HEXACYANOFERRAT(II)

Synthesis of Zn-Al-SO4 hydrotalcite and its application as anion exchanger for hexacyanoferrat (II) have been studied. Synthesis of Zn-Al-SO4 hydrotalcite was carried out by stoichiometric method and hydrothermal treatment. Sulphate in hydrotalcite interlayer was exchanged by hexacyanoferrat (II) that was assumed as pollutant. Kinetics of ion exchange was also investigated. The product of ion exchange was characterized by XRD, IR spectrophotometry and atomic absorption spectrometry. Zn-Al-SO4 hydrotalcite can be obtained by stoichiometric method at pH 8 and followed by hydrothermal treatment. The chemical formula of the hydrotalcite was Zn0.74Al0.26(OH)1.74(SO4)0.13.0.52H2O. The hexacyanoferrat (II) anion could exchange sulphate in hydrotalcite interlayer as showed by IR spectra and XRD patterns. The anion exchange capacity was 645.35 meq/100 g, and the kinetics of ion exchange reaction was first order with k = 5 x 10-5 s-1. It showed that Zn-Al-Fe(CN)6 could be regenerated easily, so it has been regenerate frequently. Keywords: hydrotalcite, anion exchanger, hexacyanoferrat