A Study on the Removal of Cr(VI) Ions by Sesame (Sesamum indicum) Stems Dehydrated with Sulfuric Acid

Abstract

An alternative, low-cost absorbent is needed to replace other, expensive treatment methods for removing Cr(VI) from wastewater. The removal of Cr(VI) ions from aqueous solution onto dehydrated sesame (Sesamum indicum) stems (DSS) has been investigated using a batch adsorption technique. In such solutions, the influence of various experimental parameters, such as contact time, initial pH, initial concentration of Cr(VI) ions, and temperature, has been evaluated, and the adsorption process was found to be highly dependent on pH. The optimum, initial pH for the removal of chromium ions was found to be 1.5. Pseudo-first-order and pseudo-second-order rate equations were tested on the kinetic data, and the adsorption process was found to follow pseudo-second-order rate kinetics. The Langmuir and Freundlich isotherm models were applied to the experimental equilibrium data depending on temperature, and the isotherm constants were determined by using nonlinear regression analysis. Equilibrium data were represented better by the Langmuir model than the Freundlich model. The monolayer coverage capacities of DSS were calculated as 189.1 and 217.4 mg/g at 20 and 50 A degrees C, respectively. Thermodynamic studies showed that the adsorption of Cr(VI) ions onto (DSS) was endothermic in nature.