Carbonization parameters optimization for the biosorption capacity of Cu2+ by a novel biosorbent from agroindustrial solid waste using response surface methodology

This research focuses on optimizing the carbonization parameters of Exhausted Kahwa Coffee (EKC) for enhanced biosorption of Cu(II) from aqueous solutions. Utilizing the Box-Behnken design (BBD), the study systematically investigates the combined effects of carbonization temperature, time, and gradient on EKC biochar (EKC-BC) formation, maintaining a constant initial copper concentration. The BBD demonstrates statistical significance through ANOVA testing. The optimized carbonization conditions obtained are at 575.42 °C, 2.59 hours, and a gradient of 19.52 °C/min, yielding a maximum predicted biosorption capacity of 6.62 mg/g. Experimental values for Cu2+ removal rate and adsorption capacity confirm the model's accuracy, with a 2% deviation from predictions. Response surface methodology effectively enhances the preparation conditions of EKC-BC, leading to improved biosorption capacity. Copper biosorption aligns well with a linearly transformed Langmuir isotherm model, while the pseudo-second-order kinetic model accurately forecasts the rate constant. Instrumental analyses, including scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX), Fourier-transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD), provide insights into the surface structural modification of EKC-BC after adsorption of Cu2+.