Membrane-assisted crystallization (MCr), is a new unit operation for the separation and/or promotion of solid pure crystals where microporous hydrophobic membranes are used not as selective barriers but to promote the water vapor transfer between phases inducing supersaturation in solution. MCr aiming to induce supersaturation in a solution, has been successfully tested in the crystallization of ionic salts, low molecular organic acids, and proteins [1]. Although some experimental studies probed the early stage of crystals formation [2], molecular modelling helped to investigate the mechanism of nucleation and crystals growth [3]. Poly(vinylidene fluoride) (PVDF) is one of the most utilized polymers because of its excellent combination of properties and processability and has been used in wide plethora of applications in membrane technology including membrane crystallization. PVDF has different polymorphs, that can be obtained depending on the membrane preparation technique and solvent used [4], and this property is important in membrane technology, because different phases might significantly affect the final membrane properties and performances, e.g. on membrane fouling and membrane wetting. A clear correlation between the dominating crystalline phases in PVDF and the performance in membrane contactor applications, and in particular in membrane crystallization is still missing and necessary. Here we will present a detailed computational analysis [5] of the crystal nucleation and growth of sodium chloride in contact with hydrophobic polymer surfaces at a supersaturated concentration of salt. Amorphous, ? and ? PVDF surfaces were studied. Results specified the crystals (as cluster) size distributions, the size of critical nuclei, and the nucleation rate. The amorphous PVDF lead to the formation of smaller but more regular clusters in reference to the other samples; ? PVDF produced much more inhomogeneous and of small dimensions crystals; ? PVDF produces crystals of larger dimensions than ? PVDF. [1] E. Drioli, G. Di Profio, E. Curcio, Progress in membrane crystallization. Curr. Opin. Chem. Eng. 2012, 1, 178-182. DOI. 10.1007/s11705-017-1649-8 [2] T. Yamazaki et al., Two types of amorphous protein particles facilitate crystal nucleation. PNAS USA, 2017, 114, 2154-2159. DOI: 10.1073/pnas.1606948114 [3] J.H. Tsai, F. Macedonio, M. L. Perrotta, A. Gugliuzza, L. Giorno, K.-L. Tung, E. Drioli, E. Tocci, Membrane-Assisted Crystallization: A Molecular View of NaCl Nucleation and Growth, Appl. Sci. 2018, 8(11), 2145-2162; DOI:10.3390/app8112145 [4] E. Tocci, C. Rizzuto, F. Macedonio, E. Drioli, Effect of Green Solvents in the Production of PVDF-Specific Polymorphs. Ind. Eng. Chem. Res. 2020, 59, 5267-5275. DOI: 10.1021/acs.iecr.9b06701 [5] M.L. Perrotta, A.G. Bruno, F. Macedonio, Z. Cui, E. Drioli and E. Tocci, Influence of PVDF polymorphs in Membrane-assisted Crystallization: NaCl crystals nucleation and growth, General Chemistry, 2021, 7, 200015 (1-10). DOI: 10.21127/yaoyigc20200015
Crystallization behavior of NaCl on PVDF polymorphs
M L Perrotta;F Macedonio;E Drioli;E Tocci
2020
Abstract
Membrane-assisted crystallization (MCr), is a new unit operation for the separation and/or promotion of solid pure crystals where microporous hydrophobic membranes are used not as selective barriers but to promote the water vapor transfer between phases inducing supersaturation in solution. MCr aiming to induce supersaturation in a solution, has been successfully tested in the crystallization of ionic salts, low molecular organic acids, and proteins [1]. Although some experimental studies probed the early stage of crystals formation [2], molecular modelling helped to investigate the mechanism of nucleation and crystals growth [3]. Poly(vinylidene fluoride) (PVDF) is one of the most utilized polymers because of its excellent combination of properties and processability and has been used in wide plethora of applications in membrane technology including membrane crystallization. PVDF has different polymorphs, that can be obtained depending on the membrane preparation technique and solvent used [4], and this property is important in membrane technology, because different phases might significantly affect the final membrane properties and performances, e.g. on membrane fouling and membrane wetting. A clear correlation between the dominating crystalline phases in PVDF and the performance in membrane contactor applications, and in particular in membrane crystallization is still missing and necessary. Here we will present a detailed computational analysis [5] of the crystal nucleation and growth of sodium chloride in contact with hydrophobic polymer surfaces at a supersaturated concentration of salt. Amorphous, ? and ? PVDF surfaces were studied. Results specified the crystals (as cluster) size distributions, the size of critical nuclei, and the nucleation rate. The amorphous PVDF lead to the formation of smaller but more regular clusters in reference to the other samples; ? PVDF produced much more inhomogeneous and of small dimensions crystals; ? PVDF produces crystals of larger dimensions than ? PVDF. [1] E. Drioli, G. Di Profio, E. Curcio, Progress in membrane crystallization. Curr. Opin. Chem. Eng. 2012, 1, 178-182. DOI. 10.1007/s11705-017-1649-8 [2] T. Yamazaki et al., Two types of amorphous protein particles facilitate crystal nucleation. PNAS USA, 2017, 114, 2154-2159. DOI: 10.1073/pnas.1606948114 [3] J.H. Tsai, F. Macedonio, M. L. Perrotta, A. Gugliuzza, L. Giorno, K.-L. Tung, E. Drioli, E. Tocci, Membrane-Assisted Crystallization: A Molecular View of NaCl Nucleation and Growth, Appl. Sci. 2018, 8(11), 2145-2162; DOI:10.3390/app8112145 [4] E. Tocci, C. Rizzuto, F. Macedonio, E. Drioli, Effect of Green Solvents in the Production of PVDF-Specific Polymorphs. Ind. Eng. Chem. Res. 2020, 59, 5267-5275. DOI: 10.1021/acs.iecr.9b06701 [5] M.L. Perrotta, A.G. Bruno, F. Macedonio, Z. Cui, E. Drioli and E. Tocci, Influence of PVDF polymorphs in Membrane-assisted Crystallization: NaCl crystals nucleation and growth, General Chemistry, 2021, 7, 200015 (1-10). DOI: 10.21127/yaoyigc20200015I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
