Coprecipitation

Coprecipitation is a solid state synthesis technique enabling atomic-level mixing of reactants. In one example, soluble transition metal salts are dissolved in water in a desired ratio. This solution is then added to a concentrated solution of Potassium Hydroxide, causing the rapid precipitation of insoluble metal hydroxides, now uniformly mixed. Often, a chelating agent such as Ammonium Hydroxide is added to the potassium hydroxide solution to encourage uniform nucleation.

This reaction is amenable to scale, and large quantities of coprecipitated reagents can be generated in a tank reactor.

Example: Create 10ml of a 0.5M NiSO4 and 1.5M MnSO4 solution in water. Add this solution dropwise to 100ml of a 2M KOH 0.05 NH4OH solution in water. Collect the precipitate via vacuum filtration, and wash off any residual soluble salts.