Described herein are ferrate-containing compositions, methods of preparing and using such compositions, and methods of stabilizing such compositions. Methods of stabilizing ferrate are described. Certain such methods comprise a step of freezing a ferrate composition wherein the ferrate composition contains a solvent. Frozen ferrate, comprising a frozen composition of ferrate and a solvent, is described. In certain embodiments, the frozen ferrate comprises a divalent cation as a counter ion.