Skip to content

Drying Kinetics of Salt Solution Droplets: Water Evaporation Rates and Crystallization

Research output: Contribution to journalArticle

Standard

Drying Kinetics of Salt Solution Droplets : Water Evaporation Rates and Crystallization. / Gregson, F. K.A.; Robinson, J. F.; Miles, R. E.H.; Royall, C. P.; Reid, J. P.

In: Journal of Physical Chemistry B, Vol. 123, No. 1, 10.01.2019, p. 266-276.

Research output: Contribution to journalArticle

Harvard

APA

Vancouver

Author

Bibtex

@article{a20c780c9933405e84f8417b49195b9c,
title = "Drying Kinetics of Salt Solution Droplets: Water Evaporation Rates and Crystallization",
abstract = "Drying and crystallization of solution droplets is a problem of broad relevance, determining the microstructures of particles formed in spray-drying, the phase of particles delivered by, for example, aerosol formulations for inhalation therapies, and the impact of aerosols on radiative forcing and climate. The ephemeral nature of free droplets, particularly when considering the drying kinetics of droplets with highly volatile constituents, has often precluded the accurate measurement of transient properties such as droplet size and composition, preventing the robust assessment of predictive models of droplet-drying rates, nucleation, and crystallization. Here, we report novel measurements of the drying kinetics of individual aqueous sodium chloride solution droplets using an electrodynamic balance to isolate and trap single aerosol droplets (radius ≈ 25 μm). The initial solution droplet size and composition are shown to be highly reproducible in terms of drying rate and crystallization time when examined over hundreds of identical evaporating droplets. We introduce a numerical model that determines the concentration gradient across the radial profile of the droplet as it dries, considering both the surface recession because of evaporation and the diffusion of components within the droplet. Drying-induced crystallization is shown to be fully determined for this system, with nucleation and instantaneous crystallization occurring once a critical supersaturation level of 2.04 ± 0.02 is achieved at the surface of the evaporating droplet. This phenomenological model provides a consistent account of the timescale and surface concentration of free-droplet crystallization on drying for the different drying conditions studied, a necessary step in progress toward achieving control over rates of crystallization and the competitive formation of amorphous particles.",
author = "Gregson, {F. K.A.} and Robinson, {J. F.} and Miles, {R. E.H.} and Royall, {C. P.} and Reid, {J. P.}",
year = "2019",
month = "1",
day = "10",
doi = "10.1021/acs.jpcb.8b09584",
language = "English",
volume = "123",
pages = "266--276",
journal = "Journal of Physical Chemistry B",
issn = "1520-6106",
publisher = "American Chemical Society",
number = "1",

}

RIS - suitable for import to EndNote

TY - JOUR

T1 - Drying Kinetics of Salt Solution Droplets

T2 - Water Evaporation Rates and Crystallization

AU - Gregson, F. K.A.

AU - Robinson, J. F.

AU - Miles, R. E.H.

AU - Royall, C. P.

AU - Reid, J. P.

PY - 2019/1/10

Y1 - 2019/1/10

N2 - Drying and crystallization of solution droplets is a problem of broad relevance, determining the microstructures of particles formed in spray-drying, the phase of particles delivered by, for example, aerosol formulations for inhalation therapies, and the impact of aerosols on radiative forcing and climate. The ephemeral nature of free droplets, particularly when considering the drying kinetics of droplets with highly volatile constituents, has often precluded the accurate measurement of transient properties such as droplet size and composition, preventing the robust assessment of predictive models of droplet-drying rates, nucleation, and crystallization. Here, we report novel measurements of the drying kinetics of individual aqueous sodium chloride solution droplets using an electrodynamic balance to isolate and trap single aerosol droplets (radius ≈ 25 μm). The initial solution droplet size and composition are shown to be highly reproducible in terms of drying rate and crystallization time when examined over hundreds of identical evaporating droplets. We introduce a numerical model that determines the concentration gradient across the radial profile of the droplet as it dries, considering both the surface recession because of evaporation and the diffusion of components within the droplet. Drying-induced crystallization is shown to be fully determined for this system, with nucleation and instantaneous crystallization occurring once a critical supersaturation level of 2.04 ± 0.02 is achieved at the surface of the evaporating droplet. This phenomenological model provides a consistent account of the timescale and surface concentration of free-droplet crystallization on drying for the different drying conditions studied, a necessary step in progress toward achieving control over rates of crystallization and the competitive formation of amorphous particles.

AB - Drying and crystallization of solution droplets is a problem of broad relevance, determining the microstructures of particles formed in spray-drying, the phase of particles delivered by, for example, aerosol formulations for inhalation therapies, and the impact of aerosols on radiative forcing and climate. The ephemeral nature of free droplets, particularly when considering the drying kinetics of droplets with highly volatile constituents, has often precluded the accurate measurement of transient properties such as droplet size and composition, preventing the robust assessment of predictive models of droplet-drying rates, nucleation, and crystallization. Here, we report novel measurements of the drying kinetics of individual aqueous sodium chloride solution droplets using an electrodynamic balance to isolate and trap single aerosol droplets (radius ≈ 25 μm). The initial solution droplet size and composition are shown to be highly reproducible in terms of drying rate and crystallization time when examined over hundreds of identical evaporating droplets. We introduce a numerical model that determines the concentration gradient across the radial profile of the droplet as it dries, considering both the surface recession because of evaporation and the diffusion of components within the droplet. Drying-induced crystallization is shown to be fully determined for this system, with nucleation and instantaneous crystallization occurring once a critical supersaturation level of 2.04 ± 0.02 is achieved at the surface of the evaporating droplet. This phenomenological model provides a consistent account of the timescale and surface concentration of free-droplet crystallization on drying for the different drying conditions studied, a necessary step in progress toward achieving control over rates of crystallization and the competitive formation of amorphous particles.

UR - http://www.scopus.com/inward/record.url?scp=85059901213&partnerID=8YFLogxK

U2 - 10.1021/acs.jpcb.8b09584

DO - 10.1021/acs.jpcb.8b09584

M3 - Article

VL - 123

SP - 266

EP - 276

JO - Journal of Physical Chemistry B

JF - Journal of Physical Chemistry B

SN - 1520-6106

IS - 1

ER -