Lanthanum-modified magnetic oyster shell and its use for enhancing phosphate removal from water

A lanthanum-modified magnetic oyster shell (La-Fe-OSP) was prepared by magnetization and lanthanum loading, and then its properties and phosphorus removal capability were studied. The results showed that La-Fe-OSP was magnetic, and the specific surface area and porosity increased remarkably compared with those before modification. La-Fe-OSP achieved a removal rate greater than 90% for various phosphate solutions (10–100 mg L−1) and could be successfully recycled by applying a magnetic field. The phosphorus adsorption process of La-Fe-OSP could be characterized by a pseudo-second order model and Langmuir model and displayed intraparticle diffusion properties. La-Fe-OSP could maintain the novel adsorption performance within the pH range of 3.0–8.0, and its adsorption capability was negligibly affected by coexisting ions and dissolved organic matter (DOM) in water. Moreover, the maximum phosphorus removal rates of La-Fe-OSP for the overlying water and the pore water were 96.4% and 41%, respectively. In addition, La-Fe-OSP application also slightly changed the order of various phosphorus forms in sediment and promoted the transformation of easily released iron-bound P (Fe-P) to hardly released occluded P (Oc-P). After five successive cycles, La-Fe-OSP still obtained 85.1% phosphate removal efficiency and thus showed excellent application prospects.