Adsorption of (methylene blue) onto natural oil shale: kinetics of adsorption, isotherm and thermodynamic studies

Abstract

This study presents two environmental aspects: valorisation of natural oil shale (NOS), on the one hand, and, on the other hand, to study the effectiveness of adsorption of methylene blue (MB) dye onto material (NOS). In this context, the most characterisations of adsorbent before and after adsorption process were investigated by several methods such as x-ray diffraction (XRD), scanning electronic microscopy (SEM) and Fourier transforms infrared spectrometry (FTIR), according to these results, the NOS is rich in quartz and calcite, the matrix clay contains the kaolin and illite and present a layer structure. The total number of results showed that the adsorption of MB onto NOS is best by pseudo-second-order fitting model with a good correlation (R2 = 0.98), on the other hand the adsorption process was described well by Langmuir isotherm with a maximal capacity of adsorption equal 29 mg/g. The effect of temperature on the adsorption of the dye was also evaluated and the thermodynamic parameters were determined. The negative values of the three thermodynamic parameters ΔH °, ΔG ° and ΔS ° of the NOS/MB system indicate that the adsorption is spontaneous, exothermic and the activated energy indicates that the adsorption mechanism might be a physical sorption process.