An emerging application of chitosan and chitosan/spirulina films for Pb²⁺ adsorption: New physicochemical insights via experimental and theoretical studies

The paper describes the adsorption mechanism of Pb2+ metal ion using chitosan (CT) and chitosan/spirulina (CTSP) films via experimental and theoretical studies. Adsorption data were quantified at 25 -55 degrees C and pH 6 to analyze the adsorption mechanism. The maximum experimental adsorption capacity of Pb2+ on CT was 60.32 mg/g, and 63.32 mg/g on CTSP. The adsorption tests showed that CTSP slightly outperformed the adsorption properties of CT. A homogenous statistical physics adsorption model (HPM) was applied to correlate the experimental adsorption data at different temperatures. The modeling results indicated that Pb2+ ions were adsorbed via one and two functional groups on CT and CTSP surfaces at 25- 45 degrees C, while one functional group was involved in the adsorption of this heavy metal ion at 55 degrees C. Therefore, Pb2+ adsorption was a multi-interaction process at low temperature, while a multi-ionic process occurred at high temperature. It was concluded that physical interactions were involved in the removal of this heavy metal ion. These scientific findings provide a new physicochemical analysis of the adsorption of this heavy metal ion using film-based adsorbents prepared from biopolymers.