High-efficiency adsorption of phosphate by Fe-Zr-La tri-metal oxide composite from aqueous media: Performance and mechanism

In this study, Fe-Zr-La tri-metal oxide (FZLO) composite was synthesized by co-precipitation method as new complex adsorbent for effective phosphate removal from aqueous media. The scanning electron microscopic study revealed that the adsorbent was of amorphous structure and consisted of the inhomogeneous aggregated nanoparticles with different sizes. Various influencing parameters such as pH values, initial concentration of phosphate ions, contact time, temperature and co-existing anions were studied to perform batch adsorption experiments. The experimental results demonstrated that the adsorption process was highly pH-dependent and obtained the maximum phosphate adsorption capacity of 101.0 mg g −1 at pH = 6. The adsorption process occurred on surface of FZLO composite has been found to be mono-layered and chemisorption dominated in nature as the data fitted well to Langmuir isotherm as well as the pseudo-second-order kinetic model. The structure and properties of the adsorbent before and after adsorption using FT-IR, XRD and XPS techniques suggested that the adsorption mechanisms involved electrostatic attraction, complexation and ligand exchange. After the adsorption, the remained P concentration met the permissible limit by the Environmental Protection Agency. The Fe-Zr-La tri-metal oxide composite could be a promising adsorbent for phosphate removal from aqueous media.