Efficient Water Purification by Photocatalysis and Rapid Adsorption of Dip-Coated Metal Foam with Nanostructured Bismuth Vanadate

Rapid removal of the organic methylene blue (MB) dye was achieved by simple stirring of highly porous Ni-Fe-Cr-Al metal foam coated with bismuth vanadate (BiVO₄). The metal foam was dip-coated with the BiVO₄ solution precursor and annealed for an hour, through which the foam surface was decorated with the highly porous nanostructure, yielding high adsorptivity. This bismuth-decorated metal foam was characterized by X-ray diffraction, X-ray photoelectron, and scanning electron microscopy to elucidate its physical, chemical, and morphological properties. The modeled pollutant, MB, was stirred with the metal foam both in darkness and in light. Complete decolorization was observed for both of these conditions, which indicates that adsorption dominates over photocatalysis; we found that photocatalysis contributed to less than 10% of the purification process. We also demonstrated that it would be possible to recycle the metal foam as many as 20 times, beyond which its purification capability degrades. However, the MB residues on the foam can be removed by simple annealing; thus, in theory the foam can be recycled indefinitely.