Removal of lead (II) from aqueous solution using epichlorohydrin cross-linked shrimp waste-derived chitosan based @ calcium phosphates biocomposite: Experimental study and computational approach

•The chitosan preparation is made from shrimp shells.•Calcium Apatite biomaterial was extracted from bovine bones.•Apatites calcium helps in enhancing the surface area of chitosan.•Cs@Epic/calcium Apatite composite successfully removed Pb (II) with the high adsorption capacity.•Theoretical and experimental data coincided with other very well. An economical composite has been synthesized utilizing chitosan derived from discarded shrimp shells and hydroxyapatite extracted from waste bovine bones. This research delves into the composite's adsorption properties for the purpose of eliminating Pb ions from wastewater. The structure of this novel composite has been meticulously examined through techniques including scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and Brunauer–Emmett–Teller (BET) analyses. Factors such as concentration, time, temperature, adsorbent dosage, and pH have been scrutinized to understand their impacts on lead ion adsorption. Concurrently, relevant adsorption parameters have been ascertained. Notably, the adsorption capacity, as determined by the Langmuir model, was found to be 154.88 mgg−1. To elucidate the adsorption kinetics, the PSO and IP models were employed. The adsorption enthalpy exhibited a positive value, while the free enthalpy displayed negativity. The mechanism governing adsorption was expounded upon through theoretical calculations, which concurred with and validated the experimental results.