Journal of Hazardous Materials B136 (2006) 567–578 Adsorption isotherms, kinetics and column operations for the removal of hazardous dye, Tartrazine from aqueous solutions using waste materials—Bottom Ash and De-Oiled Soya, as adsorbents Alok Mittal ∗ , Jyoti Mittal, Lisha Kurup Department of Applied Chemistry, Maulana Azad National Institute of Technology, Bhopal 462 007, India Received 22 November 2005; received in revised form 16 December 2005; accepted 20 December 2005 Available online 27 January 2006 Abstract Adsorbents, Bottom Ash (a power plant waste) and De-Oiled Soya (an agricultural waste) exhibit good efficacy to adsorb a highly toxic dye, Tartrazine. Through the batch technique equilibrium uptake of the dye is observed at different concentrations, pH of the solution, dosage of adsorbents and sieve size of adsorbents. Langmuir and Freundlich adsorption isotherms are successfully employed on both the adsorbents and on the basis of these models the thermodynamic parameters are evaluated. Kinetic investigations reveal that more than 50% adsorption of dye is achieved in about 1 h in both the cases, whereas, equilibrium establishment takes about 3–4 h. The linear plots obtained in rate constant and mass transfer studies further confirm the applicability of first order rate expression and mass transfer model, respectively. The kinetic data treated to identify rate controlling step of the ongoing adsorption processes indicate that for both the systems, particle diffusion process is predominant at higher concentrations, while film diffusion takes place at lower concentrations. The column studies reveal that about 96% saturation of both the columns is attained during their exhaustion, while about 88 and 84% of the dye material is recovered by eluting dilute NaOH solution through exhausted Bottom Ash and De-Oiled Soya columns, respectively. © 2006 Elsevier B.V. All rights reserved. Keywords: Tartrazine; Azo dye; Adsorption; Bottom Ash; De-Oiled Soya; Waste materials 1. Introduction Today, almost every aspect of modern living poses potential health risks. Our environment is a complex and dynamic system, in which all forms of life are interdependent. However, man is constantly changing the basic characteristics of his environment by disposing hazardous materials like dyes into water. Unfor- tunately the toxic dyes once pass into the waste water cause detrimental effects on the human/animal health, which are not only limited to themselves but may be passed on to further gen- eration by the way of genetic mutations, birth defects, inherited diseases and so on. In order to remove hazardous materials, like dyes, adsorp- tion is a method which has gained considerable attention in the recent past. Adsorption is such a useful and simple tech- nique, which allows gathering of both kinetic and equilib- ∗ Corresponding author. Tel.: +91 942 5025427; fax: +91 755 2670904. E-mail address: aljymittal@yahoo.co.in (A. Mittal). rium data without needing any sophisticated instrument [1–3]. Although many mathematical models are available for predict- ing adsorption, the acquisition of equilibrium data remains fun- damental for validating all such models. Consequently, there has been a growing interest in developing and implement- ing various potential adsorbents for the removal of specific organics from water [4–7] and researchers are always in a hunt for developing more suitable, efficient, cheap and eas- ily accessible types of adsorbents, particularly from the waste materials. The present work is an attempt to develop two waste materials—Bottom Ash and De-Oiled Soya, as efficient adsor- bents for the removal of a hazardous dye, Tartrazine from aque- ous solutions. As far as usage of Tartrazine is concern, it is used in drugs especially for the shells of medicinal capsules, syrups and cosmetics [8,9]. It is also used in variety of food materials and confectionary products as coloring material [10]. It pos- sesses high water solubility, which maximizes its chance to be found as contaminant in industrial effluents. For the humans Tartrazine is considered highly toxic and can act as catalyst in 0304-3894/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jhazmat.2005.12.037