Synergistic Enhancement of Pb 2 + Removal Using Chitosan and Quaternary Ammonium Salt Modified Sepiolite: Preparation, Characterization, and Adsorption Mechanism

ABSTRACT Here, the chitosan (CS) modified sepiolite (CS‐Sep), chitosan quaternary ammonium salt (CAS) modified sepiolite (CAS‐Sep), and CS with CSA comodified sepiolite (CS‐CAS‐Sep) were prepared and their adsorption performance for lead ions (Pb 2+ ) from aqueous were well studied. All the prepared materials were well characterized by Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD), thermogravimetric analyzer (TGA), and transmission electron microscopy (TEM). Meanwhile, the structural stability of CS‐Sep, CAS‐Sep, and CS‐CAS‐Sep, along with the impact of their crystal structures on adsorption efficiency, was also investigated through treatments at different calcination temperatures. The results revealed that the modified sepiolite presented superior adsorbability for Pb 2+ compared to raw sepiolite. Especially composite materials CS‐CAS‐Sep showed excellent performance and the maximum adsorption efficiency for Pb 2+ could reach 91.8% and with a maximum adsorption capacity 292.21 µg/g. It is noted that the adsorption activity of these adsorbents significantly decreased when the calcination temperature exceeded 200°C, which implies structural degradation of the materials. The study on isothermal adsorption behavior indicates that the adsorption of Pb 2+ by modified sepiolite is mainly monolayer adsorption, and there is also chemical adsorption behavior.