Comparative studies on the adsorption of rhodamine B and malachite green from simulated wastewater onto bentonite clay

Abstract

Bentonite clay, a readily available adsorbent was employed in the investigation of the removal of synthetic basic dyes from simulated wastewater. Batch adsorption experiments were carried out for the sorption of the basic dyes, i.e. Rhodamine B and Malachite green onto the clay. The specific surface area (Sear’s method), point of zero charge (Solid addition method) and functional groups present on the clay were determined using the Fourier Transform Infrared Spectroscopy (FTIR). The influence of process variables such as initial dyes concentrations, ionic strength, pH and contact time were also investigated. The isotherm equilibrium data were fitted to the linear forms of the Langmuir, Freundlich and Temkin isotherm models. The result of the Freundlich plots showed that both dyes were adsorbed onto a heterogeneous adsorbent surface with sorption capacities of Rhodamine B and Malachite green being 0.386 mg/g and 0.805 mg/g respectively. The data from the kinetic studies were fitted into the pseudo-first order, pseudo-second order and Boyd kinetic models. Over the study of these parameters, the pseudo-second order and film diffusion mechanism was found to predominate in the adsorption process of the dyes. Process variables such as pH and ionic strength was found to have a significant effect on the uptake of both dyes.

Keywords: Adsorbent, Adsorption, Fourier Transform Infrared Spectroscopy, Simulated, Synthetic