Additional adsorption–desorption data, isotherm modeling, and kinetic analysis for calcium ion (Ca²⁺) adsorption on maize-derived biochar

Additional adsorption–desorption data, kinetic model fitting results, and raw experimental datasets are provided to support the interpretation of calcium ion adsorption behavior on the biochar surface. These data offer detailed insight into the equilibrium characteristics, rate-controlling mechanisms, and reversibility of the adsorption–desorption process, thereby enhancing the transparency and reproducibility of the study.