ABSTRACT

From Coulomb’s Law, the higher the charge on some ion, the greater the force of attraction to an oppositely charged ion (a.k.a “counterion”). As a result, as the magnitude of the charge on the ion increases, the greater the likely stability of a solid formed with a given counterion. Since many different calcium phosphates have very low solubilities, subtle and difficult-to-detect mineral interconversions at the mineral/water interface can occur over the course of an experimental effort, as with “incongruent” dissolution, i.e., dissolution of one solid with subsequent formation of another solid. Ammonia and phosphate are high-value agricultural fertilizers, and struvite is sufficiently soluble to dissolve after application to soils. Thus, struvite is a valuable commodity if it can be harvested in a controlled manner, even if it does not tend to form on its own in a given system. Struvite precipitation can be used with high efficiency in removing phosphate.