Adsorption isotherm, thermodynamic and kinetics studies of polyphenols onto tannery shavings

Shavings constitute a waste of the tannery industry. They consist of small pieces of leather cut or shaved off from the flesh side of leather to reduce the thickness or render it uniform. Vegetable extracts, which consist of polyphenolic substances, are used for tanning a variety of articles. The aim of this work was to study the adsorption capacity of tannery shavings (wet-white and chrome shavings) for vegetable extracts (polyphenols) when they are used at moderate offers and are present in aqueous solutions at the highest concentration of 2.0 g/L. Thermodynamic and kinetic parameters of the adsorption process were also determined. Both types of shavings are good adsorbents of polyphenols in aqueous solutions although wet white shavings exhibited a higher adsorption capacity. The thermodynamic study revealed that no very marked differences were observed for both adsorbents.

► Tannery wastes such as chrome and wet white shavings are good adsorbents of polyphenols in aqueous solutions. ► The adsorption capacity of wet white shavings for polyphenols is higher than that of chrome shavings. ► The adsorption isotherms exhibit Langmuir behaviour, indicating monolayer coverage. ► Thermodynamic parameters indicate that the adsorption process under study is exothermic and spontaneous. ► A pseudo-second order kinetic model satisfactorily describes the adsorption of polyphenols onto tannery shavings.