Graphene-Like Biochar from Agricultural Waste for Cyanide Removal: Kinetic Study and Adsorption Isotherms

Abstract

Cyanide is well-known for its toxic nature and is frequently employed in the mining and chemical industries. The discharge of wastewater containing cyanide into the natural environment in various forms poses a serious threat to human health and the ecosystem. In fact, its presence can inhibit mitochondrial function in humans, leading to headaches, dizziness, irregular heartbeat, convulsions, fainting, and even death. As part of the study, an approach was developed for removing cyanide through adsorption on an adsorbent that contains graphene. The process of collecting and converting agricultural waste led to the obtention of this adsorbent. Oil palm shells were used to prepare graphene-like biochar (GpB). The obtained GpB was characterized by X-ray diffraction and its ash content, humidity, and zero charge point pH were determined. The adsorption efficiency was assessed using parameters such as initial concentration, adsorbent mass, and contact time. According to the study, 0.1 g of GpB in 50 ml of cyanide solution resulted in a 97.39% elimination after 60 minutes of equilibrium time. The study of adsorption kinetics demonstrated that GpB's cyanide removal process is chemisorption, which follows the pseudo-second order kinetic model. The Freundlich and Temkin isotherms better describe the adsorption of cyanide on GpB, confirming the presence of multilayers and an exothermic reaction.