An Investigation of the Practicality, Effectiveness, and Thermodynamic Properties of Waste-Derived Adsorbents for the Removal of Methylene Blue

Contaminants in water are becoming a greater hazard; therefore, both economical and effective adsorbents hold the key to removing pollutants and protecting our most valuable resource. This study employed three adsorbents—Bentonite clay, corn leaves, and cement crumbs—to remove the colour methylene blue from water solutions. The adsorption equilibrium isotherms of methylene blue are related to established isotherm equations such as Langmuir, Freundlich, Temkin, Elovich, Dubinin–Radushkevich, and Flory–Huggins models. The adsorption data showed a better fit with the Freundlich isotherm. Bentonite clay exhibited greater adsorption capabilities than corn leaves and cement crumbs. The highest removal efficiency (85.3%) was obtained with cement crumbs. The impact of operating conditions, such as the initial dye concentration and temperature, was investigated. The adsorbent’s ability to remove increased as the initial concentration increased. The thermodynamic analysis demonstrated that the adsorption process occurred spontaneously. Releasing heat and the negative value of ΔS° point to the strong attraction between molecules and the adsorbent surface. This investigation demonstrated that the newly developed adsorbent exhibits promising potential as a suitable choice for certain samples. The experiment concluded that Bentonite clay, corn leaves, and cement crumbs are efficient in removing organic dye, particularly methylene blue, leading to a notable decrease in colour.