A method of producing ferrate is disclosed, in which Fe.sup.3+ is oxidized with monoperoxosulfate (HSO.sub.5.sup.-) to form K.sub.2 FeO.sub.4 /K.sub.2 SO.sub.4. The isolation of the potassium ferrate (K.sub.2 FeO.sub.4) product in a sulfate matrix (K.sub.2 SO.sub.4) stabilizes the ferrate against decomposition and inhibits clumping of the solid product by inhibiting moisture adsorption. The method is a safe, simple process for the production of ferrate that is reliable, fast, and inexpensive, and that avoids the use of chlorine or chlorinated products, thus avoiding their harmful side effects. The improved ferrate product of this method is particularly useful for water and wastewater treatment, especially in the treatment of sulfides and hydrazines, and in other applications.