Study of the adsorption mechanism of certain dyes from wastewater on commercial activated carbon using the Langmuir and Freundlich methods

Abstract

In today's society, there is significant emphasis on environmental protection, with research focused on reducing pollution and developing effective depollution techniques. A growing concern is the presence of colored discharges in wastewater, which contain high levels of toxic substances that pose substantial risks to ecosystems. To mitigate these risks, various methods are employed to remove pollutants from industrial effluents, with adsorption being one of the most effective. Among the adsorbents used, activated carbon is the most commonly utilized due to its high surface area and adsorption capacity. This study aims to enhance the understanding of how two organic dyes, Methyl Red and Methylene Blue, can be removed from aqueous media through adsorption onto commercial activated carbon. The adsorption kinetics and isotherms were employed to elucidate the mechanisms involved in the elimination of these dyes from water. The kinetics were investigated using a stirred reactor, with experiments designed to vary parameters such as the initial dye concentration, the mass of the adsorbent, and the contact time. The experimental data were modeled using kinetic equations of first and second order. The results indicated that the adsorption of both Methyl Red and Methylene Blue onto activated carbon followed a pseudo-second-order kinetic model, as evidenced by large regression coefficients, signifying a good fit. This suggests that the adsorption process is likely controlled by chemisorption, involving valency forces through sharing or exchange of electrons between adsorbent and adsorbate. Additionally, the adsorption isotherms were analyzed to further understand the adsorption mechanisms and capacity. The results showed that the adsorption of both dyes onto commercial activated carbon conformed well to the Freundlich isotherm model. This model implies that adsorption occurs on a heterogeneous surface with a non-uniform distribution of adsorption heat over the surface. Overall, this study provides valuable insights into the adsorption behavior of Methyl Red and Methylene Blue on activated carbon, highlighting the effectiveness of this adsorbent in removing organic dyes from wastewater. The findings underscore the potential of using commercial activated carbon in the treatment of industrial effluents, contributing to the development of more efficient and sustainable water purification methods.