Abstract

The aim of the present investigation was to immobilize nanocrystalline diatomite within calcium alginate matrix for the adsorption of Direct Red23 (DR23) in aqueous media. Scanning electron microscopy (SEM), x-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy were used to characterize the samples. As a result, the adsorption process obeyed pseudo-second-order kinetic model (R2 = 0.9934) and Langmuir isotherm model (R2 = 0.9732) with a maximum adsorption capacity of 24.10 mg/g. The value of mean free energy (15.81 kJ/mol) demonstrated that the process has been taken place chemically. As the adsorbent dosage increased from 0.5 to 3.0 g/L, the decolorization efficiency () increased from 26.0 to 75.5, respectively. Inversely, the decolorization efficiency () decreased from 98.0 to 29.0 with increasing initial dye concentration from 5 to 160 mg/L, respectively. The negative values obtained for Gibbs free energy (�G°) and positive value of enthalpy change (�H°) indicated spontaneous and endothermic nature of the process. © 2016, Copyright © Taylor & Francis Group, LLC.