The Removal of Single and Binary Basic Dyes from Synthetic Wastewater Using Bentonite Clay Adsorbent

In order to broaden the application of Bentonite clay, an easily obtainable and bio-available low cost adsorbent, it was employed for the decolourization of synthetic wastewater consisting of single and binary basic dyes (Malachite green and Rhodamine b). The adsorbent was used as obtained without any further modification and also characterized for its specific surface area, point of zero charge and its surface functional groups pre and post dyes sorption was determined using Fourier Transform Infrared Spectroscopy (FTIR). Batch adsorption methods were employed in order to study the effects of pH, Ionic strength and contact time in the single solute system. The parameters of sorption of Rhodamine B (RDB) and Malachite green (MG) were obtained and fitted to three isotherm models; Freundlich, Langmuir and Temkin. The Freundlich plot analysis indicated the process occurred via heterogeneous coverage of adsorbent by both dyes. The kinetics of adsorption data were analyzed using the; pseudo-first order, pseudo-second order, Intraparticle diffusion, film diffusion, and Boyd kinetic models. Over the study of these parameters, the film diffusion mechanism was found to predominate in the sorption process of the dyes. Competitive sorption studies were carried out by using both dyes as either the adsorbate of interest or as the interfering specie. The competitive co-coefficient values obtained from interfering MG in RDB removal were significantly lower than those obtained from interfering RDB in MG removal, indicating that the presence of RDB in the aqua matrix had antagonistic effect on MG adsorption by Bentonite