A study on the adsorption of Cd(Ⅱ) in aqueous solutions by Fe-Mn oxide-modified algal powder gel beads

Using Microcystis aeruginosa as the raw material, the microalgae was modified through a potassium permanganate–-ferrous sulfate treatment process to prepare Fe-Mn oxide - modified algal powder. Sodium alginate was then combined with this modified powder to create Fe-Mn- modified algal powder gel beads, which were employed for the adsorption of Cd(Ⅱ) from water. At pH = 9, with dosage of 6 g·L−1 and a contact time of 8 h, the Cd(Ⅱ) solution at an initial level of 1.0 mg·L⁻¹ achieved a removal efficiency of 96%, and the maximum adsorption capacity is 15.06 mg·g⁻¹. The adsorption behavior conformed to the Langmuir isotherm and obeyed the pseudo-second-order kinetics, and was primarily gov-erned by chemical adsorption. This involved complexation with hydroxyl(-OH) and car-boxyl(-COO⁻) functional groups, the ion exchange of Ca²⁺ with Cd(Ⅱ) and, and surface complexation on Fe-Mn oxides. This study provides a valuable basis for the resource utilization of algae and the remediation of Cd contamination.