An eco-friendly approach for copper (II) ion adsorption onto cotton seed cake and its characterization: Simulation and validation

• Cotton seed cake was used to adsorb copper (II) from an aqueous solution.
• The Box–Behnken design was applied to study the effect of process variables.
• Second-order polynomial regression models were developed.
• Optimal conditions were determined by Derringer's desired function methodology.
• The adsorption process was confirmed by FTIR, SEM, EDS and XPS analyses.

In this study, copper (II) ion reduction was investigated using a four-factor three-level Box–Behnken statistical experimental design (BBD) under different adsorption conditions, such as initial concentration, cotton seed cake dose, pH and temperature. Optimum conditions for maximizing the copper (II) reduction were determined using Derringer's desired function methodology and were found to be an initial concentration of 300 mg/l, cotton seed cake dose of 1 g/l, pH of 7, and a temperature of 50 °C. Under optimum conditions, copper (II) reduction was found to be 88% with a desirability value of 0.982. The suitability of the predicted optimum conditions was validated using experimental data. The Langmuir isotherm model clearly explains the copper (II) adsorption on the cotton seed cake. The best fit of the kinetic model was found to be a pseudo first order rate equation. Finally, the characteristics of the cotton seed cake were analyzed using FTIR, XPS and SEM with EDS.