NUCLEATION AND GROWTH OF NANOCRYSTALS ON PVDF SURFACES

Membrane assisted crystallization (MCr) is a well-known technology where microporous hydrophobic membranes are used to promote the water vapor transfer between phases inducing supersaturation in solution1. Membrane crystallization is an efficient process for production, purification and/or recovery of solid materials with interesting advantages in comparison to traditional crystallization techniques, such as well-controlled nucleation and growth kinetics and fast crystallization rates and reduced induction time2. It is generally difficult to monitor the growth mechanisms of crystals formation however, molecular modelling helps to investigate the mechanism of nucleation and crystals growth3,4. Our contribution was aimed at analyzing the crystal nucleation and growth of sodium chloride in contact with hydrophobic polyvinylidene fluoride (PVDF) surfaces (amorphous together with alpha and beta phases) at a supersaturated concentration of salt. The results show that salt nucleation is faster with amorphous PVDF model then ? and ? PVDF. Molecular models confirm the highly efficient packing of the alfa and beta polymer chains, in comparison to the amorphous one resulting in greater diffusion of water molecules References 1. Drioli E., Di Profio G., Curcio E., Membrane-assisted crystallization technology (Vol. 2) (World Scientific, 2015). ISBN: 978-1-78326-333-2. 2. Macedonio F., Drioli E., Desalination and Water Treatment, 18 (1-3): 224-234, 2010. 3. D. Chakraborty et al., How crystals nucleate and grow in aqueous NaCl solution Chem. Phys. Letters, 587: 25-29, 2013. 4. Tsai J.H. et al., Membrane-Assisted Crystallization: A Molecular View of NaCl Nucleation and Growth. App. Sci. 2018, 8, 2145. Applied Sci., 8:2145-2152, 2018.