Solid Phase Extraction and Spectrophotometric Determination of Methylene Blue in Environmental Samples using Bentonite and Acid Activated Bentonite from Egypt

Abstract

In the present work, bentonite (Bn) clay, from Egypt, has been modified using HCl to produce the acid-activated bentonite (A-ABn). Both Bn and A-ABn adsorbents have been characterized using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and nitrogen adsorption measurements. The prepared adsorbents have been used for removal of methylene blue(MB) dye from environmental samples via batch test. The factors influencing the adsorption capacities of Bn and A-ABn, such as: pH, adsorbent dosage, initial dye concentration, contact time, ionic strength and temperature, were systematically investigated and discussed. The adsorption capacities are 336.741 mg/g and 174.83 for Bn and A-ABn, respectively.The experimental data were analyzed using first order kinetics, pseudo-second order kinetics and intra-particle diffusion models. It is found that kinetics followed the pseudo-second order equation. The equilibrium isotherm data are analyzed according to Langmuir and Freundlich equations. The thermodynamic parameters including ΔG°, ΔH° and ΔS°for the adsorption processes of MB on Bn and A-ABn were also calculated; and the negative values of ΔG° indicated the spontaneous nature of adsorption. The proposed adsorbents were successfully applied to the removal of MB from different water samples with a recovery % >95% and a relative standard deviation, RSD,<3%.