Copyright © Safiyya Ibrahim Abubakar et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. International Journal of Advanced Chemistry, 8 (1) (2020) 147-154 International Journal of Advanced Chemistry Website: www.sciencepubco.com/index.php/IJAC Research paper Adsorption of Methyl Orange Dye onto Raw Maize Cob and Maize Cob Activated Carbon: Isotherms and Thermodynamic Studies Safiyya Ibrahim Abubakar 1 *, Muhammad Adamu Ibrahim 1 , Muhammad Bashir Ibrahim 1 1 Department of Pure and Industrial Chemistry, Bayero University, P.M.B. 3011, Kano –Nigeria *Corresponding author E-mail: safiyyaiaramadan@gmail.com Abstract This study was aimed to evaluate the adsorption of Methyl orange (MO) onto raw maize cob (RMC) and maize cob activated carbon (MCAC) from aqueous solution using batch adsorption studies. The produced adsorbents were characterized by Scanning electron mi- croscope (SEM), and Fourier transform infrared spectroscopy (FTIR). The influence of contact time, dosage, concentration, temperature, and pH were investigated as well as Isotherm and Thermodynamic studies. Effect of contact time showed that Methyl orange adsorption were found to reach equilibrium within 125 and 110 minutes with optimum percentage removal of about 86.98% and 94.57% for raw maize cob and maize cob activated carbon respectively. The dye removal efficiency was found to increase with increasing initial dye concentration from 10 mg/L to 100 mg/L, and adsorption efficiency was found to be high at lower pH. However, increase in the dosage of the adsorbents lead to the increase in the adsorption process. The equilibrium adsorption data were analyzed using four adsorption models: Langmuir, Freundlich, Temkin, and D-R. The results revealed that MO with raw maize cob and maize cob activated carbon fit well to Freundlich with R 2 value 0.977 and Temkin with R 2 value 0.990 respectively and mean adsorption energy calculated from D-R shows it is physical adsorption and also values of enthalpy and Gibbs free energy proves that. Values of activation parameters such as free energy changes (∆G), enthalpy change (∆H) and entropy change (∆S) were calculated using Van't Hoff equation. All ∆G values were negative indicating that the adsorption was feasible and spontaneous. The result indicated that RMC and MCAC can be used for removal of MO from aqueous solution. The maize cob waste which is discarded as waste material was found to be effective adsorbent for the removal of Methyl orange dye from aqueous solution. Keywords: Adsorbate; Adsorbent; Adsorption; Maize Cob; % Removal. 1. Introduction The discharge of dye bearing wastewater into natural stream or on land has created significant concern as the dye impact toxicity and impedes light penetration and thus upsets the biological activity [1]. The wastewater from the spent dye baths and dye rinsing unit shows unfixed dyes in it. Due to the low biodegradable nature of the dyes and also its color produces serious health problems to human beings and also other living organisms in the environment [2]. Therefore, removal of such dyes from wastewater is very important for the envi- ronment [3]. Activated carbon has been proven to be an effective and widely used adsorbent for the removal of a variety of organic and inorganic pollutants dissolved in aqueous solution [4]. Activated carbon (AC) are widely used in various fields such as purification and separation in many industrial processes including medicinal use, gas storage, pollutant, odor removal, gas separation, catalysis, pharma- ceuticals, as electrode materials in electrochemical devices and in the wastewater treatment. Therefore, the demand for ACs is continu- ously increasing day by day. In practice, for the production of commercial ACs two primary sources such as coal and lignocellulosic materials are usually utilized. The composition of the lignocellulosic material regarding the cellulose, hemicelluloses and lignin content determines, to some extent, the porosity development of the produced ACs [5]. Agricultural by-products are renewable sources of raw materials for activated carbon production for the removal of color, dissolved metallic salts from aqueous solutions and also reduction of COD by adsorption [6]. The aim of this research is to study the adsorption properties of raw maize cob and activated carbon prepared from maize cob for the removal of Methyl orange which is a direct dye due to the presence of Azo group. Methyl orange (MO) is a commonly used an anionic monoazo dye in laboratory assays, textiles and other commercial products [7]. It is also a pH indicator fre- quently used in titrations because of its clear and distinct color change. It is toxic if ingested Studies have shown to be mutagen. 2. Materials and Methods 2.1. Adsorbents Preparation