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 governed by chemical adsorption. This involved complexation with hydroxyl (-OH) and carboxyl (-COO−) functional groups, the ion exchange of Ca2+ with Cd(II), 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.