Freeze-Dissolving Method: A Fast Green Technology for Producing Nanoparticles and Ultrafine Powder.

A new technology, a freeze-dissolving method, has been developed to isolate nanoparticles or ultrafine powder and is a more efficient and sustainable method than the traditional freeze-drying method. In this work, frozen spherical ice particles were produced with an aqueous solution of sodium bicarbonate or ammonium dihydrogen phosphate at various concentrations to generate nanoparticles of NaHCO or (NH)(HPO). The freeze-drying method sublimates ice, and nanoparticles of NaHCO or (NH)(HPO) in the ice templates remain. The freeze-dissolving method dissolves ice particles in a low freezing point solvent at temperatures below 0 °C, and then, nanoparticles of NaHCO or (NH)(HPO) can be isolated after filtration. The freeze-dissolving method is 100 times faster with about 100 times less energy consumption than the freeze-drying method as demonstrated in this work with a much smaller facility footprint and produces the same quantity of nanoparticles with a more uniform size distribution.