The rapid efflorescence of individual seawater droplets on polytetrafluoroethylene (PTFE, hydrophobic) and quartz (hydrophilic) substrates was investigated using a high-speed camera for imaging and micro-Raman spectroscopy to spatially resolve the particle composition. The morphology of the evaporating sea salt particles was captured using millisecond time resolution and micrometer spatial resolution. Upon rapid desiccation with dry N-2 on a quartz substrate, Na2Ca5(SO4)(6)center dot 3H(2)O and Na2xCa6-x(SO4)(6)center dot 3H(2)O (0<x<1) crystallized first followed by NaCl and finally KMgCl3 center dot 6H(2)O. We determined the formation behavior of the mixed sodium-calcium salts as crystallization products during the quick desiccation process and CaSO4 center dot 2H(2)O during the slow desiccation process. In addition, the crystallization location of different crystal products were identified and the growth speed of Na2Ca5(SO4)(6)center dot 3H(2)O crystal was compared with that of CaSO4 center dot 2H(2)O crystal. Moreover, sea salt particles with a hollow structure were observed on the PTFE substrate at the end of the quick efflorescence process.
|Number of pages||7|
|Journal||Acta Physico-Chimica Sinica|
|Publication status||Published - Nov 2011|