Adsorption of methylene blue on corncob charcoal: Thermodynamic studies

Abstract

131 Ife Journal of Science vol. 23, no. 1 (2021) INTRODUCTION Dyes have found great use in several human activities such as textile, paper, paint, cosmetics, additives in food and many other uses. A large amount of these dyes find their way into water bodies where they cause harm for aquatic life and make the water unfit for human consumption. In the search of a cheap and sustainable means of removing dye pollutants, several researchers have embarked on experiments aimed at finding methods, optimum conditions and materials that can be used for efficient dye removal (Malik et al., 2007; Suteu et al., 2011; Garg et al., 2004; Adegoke et al., 2015; Amodu et al., 2015). Removal of dyes and metallic ions from wastewater has stimulated significant interest in the use of synthetic polymers. Materials such as polyphynylamine (Amodu et al . , 2015), p o l y ( c y c l o t r i p h o s p h a z e n e c o 4 , 4 sulfonyldiphenol) nano tubes (Ayad et al., 2012; Chen et al., 2014) and carbon based materials from agricultural wastes (banana peel, cassava peel, rice bran, periwinkle shell, corncob and palm kernel husk) have been employed in water purification (Kumur et al., 2008; Bello et al., 2008; Rajeshwarisivaraj et al., 2001). While much of the work in the past had been dedicated to finding the most suitable kinetic and adsorption model for fitting data from adsorption experiments (with the hope of ascertaining the mechanism of adsorption), the suitability of the equilibrium adsorption model had often been predicated on the goodness of the fit of a given adsorption isotherm model used in fitting the experimental data. Little data is available on the systematic studies of the relationship between fitting model and the thermodynamics of adsorption of adsorbates on adsorbents. Where such studies were carried out, adsorption properties of the adsorbates and adsorbents are often not related quantitatively or semi-quantitatively to the thermodynamic quantities obtained. To remove ambiguity that may arise from the shortcomings described above, we undertake to: (i) determine how adsorption of MB on corncob charcoal are affected by pH at the point of zero charge of the adsorbent and also above and below it; (ii) estimate the effect which acid treatment of corncob charcoal had on its adsorption properties compared to the untreated corncob; (iii) https://dx.doi.org/10.4314/ijs.v23i1.13