Evaluating and Selecting Kinetic and Isotherm Models for Copper and Nickel Removal Using Cow Bone Char as an Adsorbent via Excel Solver Functions

This study explores the effectiveness of cow bone char as a low-cost, eco-friendly, and biodegradable adsorbent for removing Cu(II) and Ni(II) ions from acidic wastewater as challenging is due to heavy metal-contaminated industrial wastewater. Batch adsorption experiments were conducted to evaluate performance, with advanced nonlinear kinetic and isotherm models applied to analyze the adsorption behavior. Model fitting was performed using Microsoft Excel Solver, and model selection was validated using the Akaike Information Criterion and Average Absolute Relative Deviation Percentage. The FL-PFO kinetic model provided the best fit for time-dependent data, while the Liu and Toth isotherm models most accurately described equilibrium adsorption. Maximum adsorption capacities were 110 mg g^-1 for Cu(II) and 95 mg g^-1 for Ni(II), with Cu(II) exhibiting faster and more complete removal. Reusability testing over five cycles showed good potential for repeated use, though with gradual efficiency decline due to structural degradation and limited site regeneration. These results confirm the suitability of cow bone char as a sustainable and effective adsorbent for heavy metal removal, particularly in low-resource or decentralized water treatment systems.