Cyanide removal by graphene-type oxidized biochar: kinetic study and adsorption isotherms

The use of biomass to convert it into valuable chemicals has recently attracted the interest of researchers. In this study, graphene-type oxidized biochar was synthesized by calcination using oil palm (Elaeis guineensis) seed hulls of the hybrid variety dura x pisifera as the main carbon source. Graphene-like oxidized biochar (BOGp) was prepared from BGp by modification of the oxidation method described by Panicker and colleagues. The influences of mass variation, concentration and contact time were investigated, respectively. The study showed that for 0.1 g of BOGp used in 50 mL of a 1 mg/L cyanide solution, the elimination rate is 65%, for an equilibrium time of 60 minutes, and the elimination process is chemisorption, which follows the pseudo-second-order kinetic model. Absorption is described by the Freundlich isotherm, confirming multilayer adsorption. The BOGp characteristics were analyzed using modern analytical methods. Characteristic analysis of the BOGp results indicated that it is a low-moisture material with a high ash percentage, a density of 0.71 and a zero-charge point pH of 4. DRX analysis showed characteristic graphitic carbon peaks at 2θ ≈ 26.03° followed by peaks at 2θ ≈ 10° and 2θ ≈ 43° characteristic of oxidized graphitic carbon. Infrared analysis revealed OH and C=O functions confirming BOGp oxidation and C=C and CH2 groups corresponding to the skeletal vibration of the graphene sheet.