The features of methanal sorption by the fibrous ion-exchange resin FIBAN A-5W
Abstract
Aliphatic carbonyl compounds, in particular methanal, make significant contribution to environmental pollution. Removal of this compound from various kinds of water is an important eco-chemical task. The granular anion-exchange resins are known as effective sorbents of aliphatic aldehydes. This study considers the equilibrium and kinetic characteristics of methanal sorption by the ion-exchange fibers containing secondary
amino groups in the free base form.
The ion-exchange fiber FIBAN A-5W is used as a sorbent. It has secondary and tertiary amino groups in the structure. The kinetic curves of methanal sorption have been obtained under static conditions in the thermostatic shaker using the limited volume procedure. The concentration of the initial solution is 0.0060 mol/dm3. Sorption isotherms have been measured by varying concentration procedure at temperature values of 298±2K and 323±2K.
The required time to reach equilibrium in the sorbate-sorbent system at a temperature of 298K and 323K is 240 minutes and 180 minutes, respectively. The decrease of time to reach equilibrium indicates on a change in the sorption mechanism of methanal when the temperature increases. The application of the Boyd-Adamson formal approach to the kinetic curves has revealed the limiting stage of methanal sorption at different temperatures. The study of the methanal uptake by the fibrous ion-exchange resin has shown that when the temperature increases, the capacity of the sorbent also increases from 4.90 mmol/g to 5.64 mmol/g. The monomolecular sorption has been described from the perspective of the Langmuir theory. Gibbs free energy of sorption has been estimated. The isotherm of methanal uptake at 298 K in the whole range of concentration is described by BET equation. The method of IR-spectroscopy confirms chemisorption of methanal by the ion-exchanger used.
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