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

Abstract

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 3 or (NH 4 )(H 2 PO 4 ). The freeze-drying method sublimates ice, and nanoparticles of NaHCO 3 or (NH 4 )(H 2 PO 4 ) 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 3 or (NH 4 )(H 2 PO 4 ) 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.

Fast and simple preparation of microparticles of KHCO3 by a freeze-dissolving method with single solvent or additional antisolvent

“…These values were about half of those obtained with the average particle size of 0.04 cm 3 at the same concentration. The outcomes were consistent with NaHCO 3 system, 22 in which smaller ice particles resulted in smaller particles of NaHCO 3 , as the microparticle formation was completed during the ice frozen steps, and for smaller droplets freezing rate was faster to form smaller ice particles.…”

“…The energy consumption was much lower without the requirement of a vacuum, which was about 1% energy consumption for both FDas and FDss compared to the application of FDry. 22 Due to the dissolution process occurring at higher temperature, the energy consumption of FDss was even less than that of FDas. Comparing the FDss, FDas and FDry methods, the freeze-dissolving methods (FDss and FDas) did not require a vacuum, providing a rapid method for preparing microparticles with low energy requirements, leading to the benefit of sustainability, shown in Fig.…”

“…For FDas, only one solvent (water) was used to obtain KHCO 3 (or NaHCO 3 (ref. 22)) aqueous solution. For the second solvent, it is easy to choose an organic solvent as antisolvent, as most salts do not dissolve in organic solvents.…”

“…In previous work, we demonstrated the freeze-dissolving method. 22 With the same first step to form ice particles, the second step is to dissolve the ice particles in an antisolvent at temperature below 283.15 K, and then the microparticles are easily isolated after filtration. Compared with the traditional FDry method, the freeze-dissolving in antisolvent (FDas) method is much faster, with much smaller facility footprint and much less energy consumption.…”

Solubility correlation by model with partial molar volume

“…[ 1 ] Most of the crystallization processes employ the addition of an anti‐solvent and involve simultaneous alterations in the temperature of the solution. [ 2 ] Experimental measurement of solubility is the most reliable method and provides the most accurate solubility data [ 3,4 ] ; however, it has limitations, including long time and money consumption. To overcome these limitations, mathematical models could be used for prediction purposes or detecting possible outliers for re‐determination.…”