Growth characteristics of Fe, Zn, and Zr oxide nanotubes and their novel applications for phosphate recovery from wastewater

Abstract

This study adopted a novel approach for phosphorus recovery by growing nanotubes on the surfaces of Fe, Zn, and Zr metal foils. Electrochemical anodization was employed to generate nanotubes, with stable growth observed as the cell potential increased. Conversely, lower cell potentials resulted in more unstable anodic oxidation current densities, forming irregular nanotubes and a consequent decrease in specific surface area. The adsorption and desorption mechanisms of each material were investigated using adsorption isotherms, thermodynamics, adsorption kinetics, the intra-particle diffusion model, and desorption kinetic modeling. For Fe3O4 nanotubes (R=0.9788), the Freundlich isotherm fits better, whereas for ZnO (R=0.9865) and ZrO2 (R=0.9950) nanotubes, the Langmuir isotherm fits better. Additionally, the maximum adsorption capacities of Fe3O4, ZnO, and ZrO2 nanotubes were 42.3, 61.2, and 188.3 mg/g, ​​respectively, with ZrO2 nanotubes exhibiting the highest adsorption capacity. FT-IR analysis validated the adsorption and desorption mechanisms, allowing for refining nanotube development parameters to enhance phosphorus recovery efficiency.