Adsorption of cobalt (II) ions from aqueous solution using orange peel waste: equilibrium, kinetic and thermodynamic studies

This study describes the evaluation of orange peel waste (OPW) to remove Co(II) ions from aqueous solutions. First, parameters such as pH, initial metal ion concentration, and contact time, which affect the adsorption efficiency, were studied. It was determined that the best initial Co(II) ion concentration, the adsorption contact and the solution pH were 125 mg/L, 100 min and 5.47, respectively. The surface properties of the orange peel were investigated using SEM, energy-dispersive spectroscopy, scanning and FTIR. The results showed that the isotherm data fit the Langmuir isotherm model, which corresponds to chemisorption and possible irreversibility of the process. The adsorption capacity for Co(II) was calculated to be 4.257, 4.491 and 5.128 mg/g at 298, 308 and 318 K, respectively. As a result of the adsorption kinetic data, it was determined that the adsorption of Co(II) metal ion conformed with the second-order kinetic model. Thermodynamic studies showed that the adsorption of Co(II) ion on orange peel is spontaneous and exothermic. It was shown that OPW can be used as an effective and alternative material in the removal of Co(II) ions from aqueous media due to its high capacity, easy availability and low cost.