Preparation of Chitosan‐Modified Distillers Dregs and Chicken Manure‐Based Biochar and Its Adsorption Performance for Cadmium‐Containing Wastewater

With the rapid advancement of industrialization, cadmium (Cd (II)) pollution in aqueous solutions has become increasingly severe, necessitating the development of cost-effective and efficient adsorbents. In this study, biochar was prepared through co-pyrolysis of chicken manure and distiller's grains, followed by chitosan modification to enhance its Cd (II) adsorption capacity. Characterization confirmed successful chitosan loading, which increased pore structure, expanded specific surface area, and introduced amino and hydroxyl functional groups. Adsorption kinetics experiments revealed R² values exceeding 0.95 for both pseudo-first-order and pseudo-second-order models, with the pseudo-second-order model better describing the adsorption process. This indicates that both physical and chemical adsorption contribute to Cd (II) removal by the modified biochar, with chemical adsorption playing a dominant role. Adsorption isotherm fitting revealed a Langmuir maximum adsorption capacity (Q_m) of 165.2 mg·L^-1, validating the modified biochar's excellent Cd (II) adsorption performance. Mechanism studies identified complexation, ion exchange, electrostatic attraction, and precipitation as primary removal pathways. Furthermore, CBC maintained over 80% removal efficiency after four adsorption-desorption cycles. In summary, the chitosan-modified distiller's grains with chicken manure-based biochar developed in this study represent an environmentally friendly and highly efficient adsorbent, providing an effective strategy for treating Cd (II)-contaminated wastewater.