Adsorption of Supranol Yellow 4 GL from aqueous solution by surfactant-treated aluminum/chromium-intercalated bentonite

The aim of this paper is to study the adsorption of the acid dye Supranol Yellow 4 GL (S.Y. 4 GL) from aqueous solution on an inorgano–organo clay. Bentonite is naturally occurring clay with good exchanging ability. By exchanging its interlamellar cations with cetyltrimethylammonium bromide (CTAB) and hydroxyaluminic or chromium polycations, the properties of natural bentonite can be greatly improved. Batch adsorption tests of Supranol Yellow 4 GL were carried out at 20 °C and constant pH 6.5. To investigate the adsorption mechanisms, the simplified kinetic models, such as pseudo-first-order, pseudo-second-order, Elovich equation and intraparticle diffusion are tested. The results show that adsorption follows second-order rate kinetic. The correlation coefficients obtained for second-order kinetics model are greater than 0.998 indicating a better fitting of this equation. The experimental data are analysed by Langmuir, Freundlich and Elovich isotherms. The equilibrium adsorption capacity of anionic dye is determined from the Langmuir equation and found to be 142, 85 and 128, 20 mg/g (standard deviation; Δq (%) = 3.52 and 18.51) for CTAB-Cr-B and CTAB-Al-B, respectively.