A general route to modify diatomite with niobates for versatile applications of heavy metal removal.

A general solution-phase strategy is developed to synthesize nanostructure niobates such as MnNbO, SnNbO and ZnNbO on natural mineral diatomite for water environmental remediation. (NH)CO aqueous solution is the key to achieve a scalable and controllable synthesis of niobate/diatomite hybrid systems, which generates NH·HO for surface etching activation of diatomite, and HCO for complexation dissolution of NbO, enabling the heterogeneous crystallization process to proceed with controllable growth kinetics. First principle calculations indicate that both niobium atom and niobium-oxygen species have the lowest adsorption energy on SiO surface, and then induce the nucleating process of Nb-O-Mn (or Zn, Sn) networks. Cr(vi), Fe(iii), and Pb(ii) ions are taken as target pollutants to evaluate the water-cleaning ability of the niobate-modified diatomite. Possible mechanisms for the photoreduction of Cr(vi), physical adsorption of Fe(OH) colloids, and chemisorption of Pb(ii) ions are proposed on the basis of experimentally investigations. The possibility of combining the advantages of natural mineral diatomite and nanostructured niobates provides a highly robust and potential material system with versatile functionalities of heavy metal ion removal, demonstrating great promise for a wide range of water purification.