Drying Kinetics and Particle Formation from Dilute Colloidal Suspensions in Aerosol Droplets
Drying Kinetics and Particle Formation from Dilute Colloidal Suspensions in Aerosol Droplets
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DOI：
10.1021/acs.langmuir.0c01830
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发表时间：
2020-10-27
期刊：
影响因子：
3.9
通讯作者：
Reid, Jonathon P.
中科院分区：
文献类型：
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作者：
Archer, Justice;Walker, Jim S.;Reid, Jonathon P.
诸如药品和食品的喷雾干燥等工业过程通常涉及将含有胶体悬浮液的气溶胶液滴干燥成具有所需性能的粉末微粒。干燥过程后获得的最终干燥产品/微粒的形貌和表面特性受到初始气溶胶液滴组成参数和干燥条件的强烈影响。特别是，最终的干燥微粒形态可以依赖于无量纲的佩莱特数（Pe），它表达了分散颗粒在液滴内的扩散和溶剂蒸发损失率之间的相对竞争。在这项工作中，我们研究了如何控制气相干燥条件和初始气溶胶液滴组成可以用来影响气溶胶液滴在气相中的干燥动力学在一定范围内的Peclet数。利用单颗粒悬浮仪——电动天平，测量了温度（263-326 K）和相对湿度（0-90%）的气相干燥条件下，硅胶胶体液滴（0.10-0.60% v/v）的干燥动力学，得到了Peclet数在4.05 ~ 184.5之间。我们证明，对于初始饲料胶体浓度较稀的气溶胶液滴，在恒定蒸发状态下，初始成分对溶剂蒸发速率没有强烈影响，其中包含的纳米颗粒（NPs）作为旁观者。然而，气相干燥条件，温度和相对湿度，通过蒸发冷却直接影响液滴温度，以及液滴干燥动力学和最终干燥的微粒性质。通过对单液滴测量的液滴干燥动力学的先验知识，我们进一步证明了定制干燥微颗粒形态的可能性。在Pe = 23.8处收集的干燥二氧化硅微粒具有致密的球形形貌，而在最高Pe = 180.0处收集的二氧化硅微粒具有皱褶的表面形貌，在这两个极限Pe值之间发生了形态过渡。我们的研究结果扩展了对胶体悬浮液中气溶胶液滴干燥控制机制的基本理解，涵盖了从喷雾干燥到含有细菌和病毒的呼吸道液体液滴的干燥以及大气气溶胶液滴的干燥的广泛应用领域。
Industrial processes such as spray drying of pharmaceutical and food products often involve the drying of aerosol droplets containing colloidal suspensions into powdered microparticles of desired properties. The morphology and surface properties of the final dry products/microparticles obtained after the drying process are strongly influenced by the parameters of the initial aerosol droplet composition and the drying conditions. In particular, the final dry microparticle morphology can be dependent on the dimensionless Peclet number (Pe), which expresses the relative competition between the diffusion of the dispersed particles within the droplet and the rate of solvent loss via evaporation. In this work, we examine how control over the gas phase drying conditions and initial aerosol droplet composition can be used to influence the aerosol droplet drying kinetics in the gas phase for a range of Peclet numbers. We used a single-particle levitation instrument, the electrodynamic balance, to measure the drying kinetics of colloidal silica droplets (0.10-0.60% v/v) under controlled gas phase drying conditions of temperature (263-326 K) and relative humidity (0-90%) and obtained Peclet numbers ranging from 4.05 to 184.5. We demonstrate that, for aerosol droplets with initially dilute feed colloid concentrations and within the constant evaporation regime, the starting composition does not strongly influence the solvent evaporation rate with the included nanoparticles (NPs) acting as spectators. However, the gas phase drying conditions, temperature, and relative humidity, directly influence the droplet temperature via evaporative cooling as well as the droplet drying kinetics and the final dry microparticle properties. With a priori knowledge of the droplet drying kinetics from the single droplet measurements, we further demonstrate the possibility of tailoring the morphology of the dried microparticles. Dried silica microparticles collected at Pe = 23.8 had dense spherical morphologies, while those at the highest Pe = 180.0 had crumpled surface morphologies with a transition in morphology between these limiting Pe values. Our results extend the fundamental understanding of the mechanisms controlling the drying of aerosol droplets in colloidal suspensions across a wide range of application areas extending from spray drying to the drying of respiratory fluid droplets containing bacteria and viruses and the drying of atmospheric aerosol droplets.