Removal of methylene blue pollutant from the textile industry by adsorption onto Zeolithe: Kinetic and thermodynamic study

Abstract

In the textile industry, various acidic, basic and reactive dyes are used for different applications; the aim of this study is to eliminate Methylene blue (MB) a dangerous dye by a zeolithe produced at low economic cost by adsorption in batch mode. The adsorbent was characterized by the FTIR spectroscopy, X-ray diffraction (XRD), and point of zero charge (pHpzc = 10.42). Some examined factors were found to have a significant impact on the adsorption capacity of the zeolithe like the initial dye concentration (5–25 mg/L), solution pH (2–14), adsorbent dose (0.1–2 g/L), agitation speed (150–500 rpm), particles size (100–500 µm) and temperature (298–333 K). The best capacity was found at pH 6 with an adsorbent dose 0.2 g/L, an agitation speed 200 rpm and a contact time of 40 min. Modeling the Kinetics and Isotherms data shows respectively that the pseudo-second-order kinetic model and Langmuir isotherm provide better fitness to the experimental data with the maximum adsorption capacity of 12.50 mg/g at 25°C. The adsorption isotherms at different temperatures have been used for the determination of the free energy (ΔG°); enthalpy (ΔH°) and entropy (ΔS°) to predict the nature of MB adsorption. The positive values of ΔG° and ΔH° indicate a non-spontaneous and endothermic MB adsorption with a physisorption process. The adsorbent elaborated from the zeolithe was found to efficient and suitable for the removal of reactive dyes from aqueous solutions, due to its, low cost preparation and good adsorption capacity. The photocatalysis of MB in the presence of hybrid semiconductor (TiO2/Zeolithe) constitutes the logical continuation of this study.