Morphological Control of Magnesium Phosphate Hydrate from a Highly Concentrated Alkaline Earth Metal Phosphate Solution by Microwave Heating

Abstract

A CO2 blowing method was used to obtain a highly concentrated magnesium phosphate solution (47 times more concentrated than conventional solutions). In the present study, we exposed the solution to microwave heating. Fine and uniform spherical particles were obtained by microwave heating at a heating rate of 2030oC·min-1. Conversely, the products formed plate-like particles after a retention time of 5 min with a low heating rate. The spherical particles had a relatively uniform size of 0.51.0 μm and were composed of magnesium phosphate octahydrate, while the plate-like particles were composed of magnesium phosphate pentahydrate. Spherical particles could not be obtained by heating at a gradual heating rate using a hot plate; instead, large and non-uniform plate-like particles were formed. From this result, it is evident that microwave heating enables the production of unusual shaped particles that are not accessible using ordinary heating methods.