Jumping into metastable 1:1 urea-succinic acid cocrystal zone by freeze-drying

Aqueous solutions with molar ratios between urea and succinic acid from 0.3:1 to 3:1 were evaporated at room temperature, and products were pure or mixtures of stable 2:1 urea-succinic acid cocrystals, urea or succinic acid. By freeze-drying, metastable 1:1 urea-succinic acid cocrystal formed. The different mixtures of the 1:1 cocrystals reveal several "hidden" metastable zones in a ternary phase diagram of the 2:1 cocrystal. The formation of the 1:1 cocrystal indicated that the solution composition points in the phase diagram "jump" over the stable zone into the metastable zones

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 NaHCO3 or (NH4)(H2PO4). The freeze-drying method sublimates ice, and nanoparticles of NaHCO3 or (NH4)(H2PO4) 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 NaHCO3 or (NH4)(H2PO4) 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.</p

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 NaHCO3 or (NH4)­(H2PO4). The freeze-drying method sublimates ice, and nanoparticles of NaHCO3 or (NH4)­(H2PO4) 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 NaHCO3 or (NH4)­(H2PO4) 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

Jumping into metastable 1:1 urea-succinic acid cocrystal zone by freeze-drying

Aqueous solutions with molar ratios between urea and succinic acid from 0.3:1 to 3:1 were evaporated at room temperature, and products were pure or mixtures of stable 2:1 urea-succinic acid cocrystals, urea or succinic acid. By freeze-drying, metastable 1:1 urea-succinic acid cocrystal formed. The different mixtures of the 1:1 cocrystals reveal several "hidden" metastable zones in a ternary phase diagram of the 2:1 cocrystal. The formation of the 1:1 cocrystal indicated that the solution composition points in the phase diagram "jump" over the stable zone into the metastable zones

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 NaHCO3 or (NH4)(H2PO4). The freeze-drying method sublimates ice, and nanoparticles of NaHCO3 or (NH4)(H2PO4) 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 NaHCO3 or (NH4)(H2PO4) 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.</p

Cocrystallization of urea and succinic acid in “Nano-Crystallizer”

In the bulk scale of crystallization, urea-succinic acid (U-SA) cocrystals have been reported to only form stable 2:1 U-SA cocrystal, without any metastable 1:1 cocrystal, by slow evaporation and cooling crystallization in an aqueous solvent. In this work, cooling crystallization and evaporation crystallization were applied in nano-crystallizers, i.e. the nano-pores in controlled pore glass (CPG). It is the first time to demonstrate that, with confined solution, it is possible to produce and maintain metastable cocrystals during the slow crystallization process, indicating the strong influences of the confinement on the phase diagram and the thermodynamic properties of the nano-scale cocrystals. The influences of the urea and succinic acid concentration and the pore size of CPG on the polymorphs and melting point of the nanocrystal have been investigated. Further understanding of the mechanism may contribute to new methods for maintaining the unstable materials and discovering new forms of pharmaceutical compounds and materials

Cocrystallization of urea and succinic acid in “Nano-Crystallizer”

In the bulk scale of crystallization, urea-succinic acid (U-SA) cocrystals have been reported to only form stable 2:1 U-SA cocrystal, without any metastable 1:1 cocrystal, by slow evaporation and cooling crystallization in an aqueous solvent. In this work, cooling crystallization and evaporation crystallization were applied in nano-crystallizers, i.e. the nano-pores in controlled pore glass (CPG). It is the first time to demonstrate that, with confined solution, it is possible to produce and maintain metastable cocrystals during the slow crystallization process, indicating the strong influences of the confinement on the phase diagram and the thermodynamic properties of the nano-scale cocrystals. The influences of the urea and succinic acid concentration and the pore size of CPG on the polymorphs and melting point of the nanocrystal have been investigated. Further understanding of the mechanism may contribute to new methods for maintaining the unstable materials and discovering new forms of pharmaceutical compounds and materials

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

Microparticles featuring specific attributes are essential for the chemical industries. Microparticles of KHCO3 were prepared by a freeze-dissolving method, with one solvent or with additional antisolvent. Firstly, KHCO3 aqueous solution was dripped into liquid nitrogen to prepare ice spherical particles, and additional antisolvent, ethanol, was used to dissolve the ice scaffolding to isolate the microparticles of KHCO3. In this work we have developed a new freeze-dissolving method with only one solvent, water. After formation of ice particles, a low-temperature saturated aqueous solution of KHCO3 was used to dissolve the ice in frozen spherical particles at low temperature to isolate the microparticles. Both freeze-dissolving methods were 100 times faster and more energy-efficient than the traditional freeze-drying method. The microparticles of KHCO3 obtained by the freeze-drying method and freeze-dissolving with antisolvent and with saturated solution were characterised with SEM and the particle size distributions were compared.</p

Supplementary information files for "Fast and simple preparation of microparticles of KHCO₃ by a freeze-dissolving method with single solvent or additional antisolvent"

Supplementary files for article "Fast and simple preparation of microparticles of KHCO3 by a freeze-dissolving method with single solvent or additional antisolvent"Microparticles featuring specific attributes are essential for the chemical industries. Microparticles of KHCO3 were prepared by a freeze-dissolving method, with one solvent or with additional antisolvent. Firstly, KHCO3 aqueous solution was dripped into liquid nitrogen to prepare ice spherical particles, and additional antisolvent, ethanol, was used to dissolve the ice scaffolding to isolate the microparticles of KHCO3. In this work we have developed a new freeze-dissolving method with only one solvent, water. After formation of ice particles, a low-temperature saturated aqueous solution of KHCO3 was used to dissolve the ice in frozen spherical particles at low temperature to isolate the microparticles. Both freeze-dissolving methods were 100 times faster and more energy-efficient than the traditional freeze-drying method. The microparticles of KHCO3 obtained by the freeze-drying method and freeze-dissolving with antisolvent and with saturated solution were characterised with SEM and the particle size distributions were compared.© The Authors, CC BY 3.0</p

Supplementary information files for " Application of efficient and sustainable freeze-dissolving technology in manufacturing of KHCO3 ultrafine particles"

Supplementary files for article "Application of efficient and sustainable freeze-dissolving technology in manufacturing of KHCO3 ultrafine particles"The development of ultrafine particles provided a new way to solve problems in the fields of energy, environment, and medicine, and had become one of the most promising technologies. Therefore, the application of ultrafine particles required the development of cleaner, greener, and more efficient preparation methods. The new freeze-dissolving technology has been applied in manufacturing of KHCO3 ultrafine particles, with an aqueous solution of 0.02–0.1 g KHCO3/g water. Frozen ice particles were formed after dripping the solution into liquid nitrogen. The antisolvent ethanol was used to dissolve the ice spherical template at a temperature below 273.15 K, and the pre-formed KHCO3 ultrafine particles inside the ice template remained in the ethanol aqueous solution. The ice particles were put into the freeze dryer to isolate the ultrafine KHCO3 particles. Compared with the particles produced with traditional freeze-drying technology, the ultrafine powder/particles produced by the freeze-dissolving technology were smaller with narrower size distribution. The freeze-dissolving technology has demonstrated a much more sustainable and efficient manufacturing process than the traditional freeze-drying process. In addition, the influence of the concentrations of KHCO3 and the sizes of ice particles were investigated with the discussions of mechanisms.©The Authors, CC BY-NC-ND 4.0</p