Preparation of ferrihydrite nanoclusters using hydrolysis enhanced by CuO and their subsequent characterisation

Abstract

A new method of preparing iron oxyhydroxide was developed, in which nanoclusters were precipitated from heated aqueous Fe(NO₃)₃ solution through promotion by CuO. The products of this reaction were characterised. The composition of the products changed with the content of CuO added, but no copper ferrite or solid solution was identified. When the molar ratio of CuO to Fe(NO₃)₃ was limited to 1∶1, the products were nanoclusters consisting of very small Fe₅O₇(OH).4H₂O ferrihydrite (FH) crystallites. The nanoclusters adsorbed a small amount of Fe(NO₃)₃, which decreased as the amount of CuO increased when the molar ratio of CuO to Fe(NO₃)₃ was less than 1∶1. When the molar ratio of the precursors exceeded 1∶1, the amount of Fe(NO₃)₃ adsorbed onto the FH nanoclusters decreased, and Cu₂(OH)₃NO₃ was found in the precipitate. The experimental results were attributed to the hydrolysis of Fe(NO₃)₃ being enhanced by CuO acting as a hydrolyte. Saturation behaviour was observed for the addition of CuO. This is a new route to prepare oxide nanoclusters by enhanced hydrolysis.

Keywords:

• Ferric nitrate
• Copper oxide
• Hydrolysis
• Ferrihydrite
• Nanocluster

Acknowledgements

Financial support for this work was provided by the National Science Foundation of China (Grant No. 11074205).