Efflorescence relative humidity for ammonium sulfate particles
Yonggang Gao1, Shing Bor Chen, Liya E Yu
1Department of Chemical and Biomolecular Engineering, National University of Singapore, Singapore 117576.
The Journal of Physical Chemistry. A
|June 16, 2006
Summary
The efflorescence relative humidity (ERH) of ammonium sulfate particles varies with size. Smaller particles (<30 nm) are significantly affected by the Kelvin effect, while larger particles (>50 nm) are primarily influenced by aerosol size.
Area of Science:
- Atmospheric Chemistry
- Physical Chemistry
- Aerosol Science
Background:
- Ammonium sulfate particles are common atmospheric aerosols.
- Understanding their efflorescence relative humidity (ERH) is crucial for atmospheric modeling.
- Previous studies have explored ERH but with limited focus on size-dependent effects.
Purpose of the Study:
- To theoretically calculate the ERH of ammonium sulfate particles across a wide size range.
- To investigate the influence of particle size and the Kelvin effect on ERH.
- To validate theoretical predictions against experimental measurements.
Main Methods:
- Application of classical homogeneous nucleation theory.
- Calculation of ERH for ammonium sulfate particles from 8 nm to 17 microm.
- Comparison of theoretical ERH values with experimental data.
Main Results:
- Theoretical ERH predictions closely matched experimental values.
- ERH decreased with decreasing particle size, reaching a minimum around 30% for 30 nm particles, then increased.
- The Kelvin effect was theoretically confirmed to significantly impact ERH for particles <30 nm.
- Aerosol size was identified as the dominant factor for particles >50 nm.
Conclusions:
- The study provides a theoretical framework for understanding size-dependent ERH of ammonium sulfate.
- Kelvin effect and aerosol size are critical factors influencing efflorescence behavior.
- Findings enhance the accuracy of atmospheric models involving sulfate aerosols.
More Related Videos
Related Concept Videos
01:29Atomic Fluorescence Spectroscopy
Atomic fluorescence spectroscopy (AFS) is an analytical technique that involves the electronic transitions of atoms in a flame, furnace, or plasma being excited by electromagnetic (EM) radiation. When these atoms absorb energy, they become excited and subsequently release energy as they return to their original state. This emitted light, or "fluorescence," is observed at a right angle to the incident beam. Both absorption and emission processes transpire at distinct wavelengths, which are...
00:52Washing, Drying, and Ignition of Precipitates
After filtration, the precipitate is washed to remove coprecipitated impurities and any remaining mother liquor. Colloidal precipitates, such as silver chloride, are washed with an electrolyte (such as dilute nitric acid) to prevent the peptization of the precipitate. In the case of slightly soluble precipitates, the wash solution contains a common ion to reduce solubility. Lead sulfate, which is slightly soluble in water, is washed with dilute sulfuric acid. Similarly, wash solutions may be...
01:25Atomic Absorption Spectroscopy: Atomization Methods
Atomic Absorption Spectroscopy (AAS) atomizes samples through flame atomization or electrothermal atomization. Flame atomization typically involves a nebulizer and spray chamber assembly to combine the sample with a fuel–oxidant mixture, creating a fine aerosol mist that enters a burner. Typically, the fuel and oxidant are combined in an approximately stoichiometric ratio. However, for atoms that are easily oxidized, a fuel-rich mixture may be more advantageous. Only about 5% of the aerosol...
03:24Common Ion Effect
Compared with pure water, the solubility of an ionic compound is less in aqueous solutions containing a common ion (one also produced by dissolution of the ionic compound). This is an example of a phenomenon known as the common ion effect, which is a consequence of the law of mass action that may be explained using Le Châtelier’s principle. Consider the dissolution of silver iodide:
01:12Precipitation Processes
The experimental conditions in a gravimetric analysis should be optimized to maximize the particle size and purity of the obtained precipitate. Ideally, the concentration of the precipitating reagent should be low with effective stirring to maintain low relative supersaturation for the growth of large crystals. In homogeneous precipitation, the precipitant is slowly generated by a chemical reaction in the solution to avoid local reagent excesses. For example, urea decomposes gradually to...
03:11Precipitation of Ions
Predicting Precipitation
The equation that describes the equilibrium between solid calcium carbonate and its solvated ions is:
The equation that describes the equilibrium between solid calcium carbonate and its solvated ions is: