Removal of Cyanide from Aqueous Solutions by Biosorption onto Sorghum Stems: Kinetic, Equilibrium, and Thermodynamic Studies

Abstract

Sorghum stems will be considered in this work as an alternative for the adsorption of cyanides in aqueous solution. It is an abundant material in southern Algeria, and it does not require any specific pretreatment. Therefore, it is a much cheaper adsorbent than the adsorbents usually used for cyanide adsorption, such as activated carbon. In this work, a complete study will be presented that includes the physicochemical characterization of prepared sorghum stem particles (SSPs) and the kinetic and thermodynamic adsorption studies. The pseudo-second-order kinetic model best described the experimental data with a high coefficient of determination and that the Langmuir isotherm model fitted better than the Freundlich and Temkin models. The Langmuir maximum adsorption capacity (qm) was 76.92 mg/g at 293 K. The thermodynamic study showed that the adsorption of cyanides on SSPs was endothermic and spontaneous and that it was chemisorption. The comparison with the usual adsorbents tested by other authors showed that SSP could be an interesting candidate due to its high adsorption capacity and easy preparation.