Publikacje

Abstract:

The possibilities of applying halloysite in removing toxic anions of chromium(VI) compounds from
aqueous solutions were examined in this work. Natural halloysite obtained from the Dunino mine in
Poland was modified with intralayer cation exchange for hexadecyltrimethylammonium cations. The
influence of the modification on halloysite structure was described with the use of a scanning electron
microscope (SEM) together with surface analysis using energy dispersive X-ray spectroscopy (EDS/
EDX), texture characteristics on the basis of N2 adsorption–desorption analysis, as well as Fouriertransform
infrared spectroscopy (FTIR). Chromium(VI) equilibrium isotherms were determined in the
following temperature ranges: 293K, 303, 313K, and 323K. The experimental isotherms were analyzed
on the basis of the Freundlich equation, as well as Langmuir, Temkin and Dubinin-Raduskevich
models. It was observed that the Langmuir isotherm perfectly described the experimental data with
respect to adsorption equilibrium. Process thermodynamics was characterized together in determining
isothermal adsorption heat. Chromium(VI) adsorption kinetics was discussed based on the
following models: pseudo-first order, pseudo-second order, Elovich, intraparticle diffusion, and
the film diffusion model. Pseudo-second-order reaction rate constants determined at four various
temperature values were applied in setting activation energy. Process effectiveness, that is, removing
toxic chromium(VI) from the solution with the modified halloysite, is high, reaching 80%.

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Equilibrium and kinetic studies on the process of removing chromium(VI) from solutions using HDTMA-modified halloysite