Removal of Safranine T by a highly efficient adsorbent (Cotinus Coggygria leaves): Isotherms, kinetics, thermodynamics, and surface properties

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Leaf-based adsorbents have attracted many researchers due to their low cost, high efficiency, and high adsorption capacity. In the present study, the performance of Cotinus Coggygria leaves on the adsorptive removal of Safranine T dye from an aqueous solution was investigated. Before the adsorption studies, the inverse gas chromatography (IGC) method was performed to observe the surface properties of Cotinus Coggygria, for the first time. With the data obtained from IGC analysis, the acidity/basicity degree of the adsorbent surface and the required conditions for the highest adsorption capacity were determined. The surface of the leaves was found to have a basic characteristic. The adsorption studies were carried out under different parameters including contact time, temperature, pH, initial dye concentration, and adsorbent dosage. The maximum percentage of Safranine T was obtained as 93.62% at pH = 7 and 55 °C. The different isotherms were applied namely Langmuir, Freundlich, D-R, Harkins-Jura, and Temkin isotherm models. From the correlation coefficients, it was obtained that the adsorption took place in agreement with the Langmuir isotherm. The adsorption capacity showed the maximum at 2000 mg/g in pH = 7 at 55 °C. As a result of the kinetic studies, it was seen that adsorption followed the pseudo-second-order kinetic model. When thermodynamic parameters were obtained, it was seen that the adsorption occurred exothermically and spontaneously. This study suggests that Cotinus Coggygria leaves are highly efficient biobased materials as an adsorbent.