Kinetics and isotherm studies for adsorptive removal of methylene blue from aqueous solutions using organoclay

Abstract

The presence of dyes in various industrial effluents has emerged as a global environmental concern. The removal of dyes from effluents thus becomes essential to reduce their risks to different life forms. Keeping this in view, raw bentonite (Ben) has been modified with hexadecyltrimethylammonium bromide (HDTMA-Br) by cation exchange to form HDTMA modified bentonite (HDTMA-Ben). Both Ben and HDTMA-Benwere analyzed using Brunauer–Emmet–Teller (BET) method, Scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy and Thermogravimetric analysis (TGA). Studies are conducted at room temperature to determine the behaviour of Ben and HDTMA-Ben towards the adsorptive removal of Methylene blue (MB) from aqueous solutions. Thermodynamics studies were carried out to assess the effect of temperature on adsorption behaviour of both the adsorbents. The experimental adsorption capacity of HDTMA-Ben at equilibrium time was found to be 93.14 mg g-1. Characterization results revealed insertion of alkylammonium chain in between the layers of bentonite. Thermodynamics data indicated that the adsorption is spontaneous, exothermic and enhanced on increasing temperature. HDTMA-Ben showed higher dye removal efficiency in comparison to Ben under all conditions. The adsorption data of both the adsorbents was better explained by Freundlich isotherm whereas the pseudo-second-order (PSO) model explained the adsorption kinetics of the adsorbents.