Efflorescence of Ammonium Sulfate and Coated Ammonium Sulfate Particles: Evidence for Surface Nucleation

Using optical microscopy, we investigated the efflorescence of ammonium sulfate (AS) in aqueous AS and in aqueous 1:1 and 8:1 (by dry weight) poly(ethylene glycol)-400 (PEG-400)/AS particles deposited on a hydrophobically coated slide. Aqueous PEG-400/AS particles exposed to decreasing relative humidity (RH) exhibit a liquid−liquid phase separation below 90% RH with the PEG-400-rich phase surrounding the aqueous AS inner phase. Pure aqueous AS particles effloresced in the RH range from 36.3% to 43.7%, in agreement with literature data (31−48% RH). In contrast, aqueous 1:1 (by dry weight) PEG-400/AS particles with diameters of the AS phase from 7.2 to 19.2 μm effloresced between 26.8% and 33.9% RH and aqueous 8:1 (by dry weight) PEG-400/AS particles with diameters of the AS phase from 1.8 to 7.3 μm between 24.3% and 29.3% RH. Such low efflorescence relative humidity (ERH) values have never been reached before for AS particles of this size range. We show that these unprecedented low ERHs of AS in PEG-400/AS particles could not possibly be explained by the presence of low amounts of PEG-400 in the aqueous AS phase, by a potential inhibition of water evaporation via anomalously slow diffusion through the PEG coating, or by different time scales between various experimental techniques. High-speed photography of the efflorescence process allowed the development of the AS crystallization fronts within the particles to be monitored with millisecond time resolution. The nucleation sites were inferred from the initial crystal growth sites. Analysis of the probability distribution of initial sites of 31 and 19 efflorescence events for pure AS and 1:1 (by dry weight) PEG-400/AS particles, respectively, showed that the particle volume can be excluded as the preferred nucleation site in the case of pure AS particles. For aqueous 1:1 (by dry weight) PEG-400/AS particles preferential AS nucleation in the PEG phase and at the PEG/AS/substrate contact line can be excluded. On the basis of this probability analysis of efflorescence events together with the AS ERH values of pure aqueous AS and aqueous PEG-400/AS particles aforementioned, we suggest that in pure aqueous AS particles nucleation starts at the surface of the particles and attribute the lower ERH values observed for aqueous PEG-400/AS particles to the suppression of the surface-induced nucleation process. Our results suggest that surface-induced nucleation is likely to also occur during the efflorescence of atmospheric AS aerosol particles, possibly constituting the dominating nucleation pathway

Electrophotolysis oxidation system for measurement of organic concentration in water

Methods and apparatus for determining organic carbon in aqueous solution are described. The method comprises subjecting the aqueous solution to electrolysis, for generating oxygen from water, and simultaneously to ultraviolet radiation, for oxidation of substantially all organic carbon to carbon dioxide. The carbon dioxide is measured and the value is related to the concentration of organic carbon in the aqueous solution

Aqueous-Phase Adsorption Of Phenolic Compounds On Activated Carbon.

Laboratory batch studies were conducted on adsorption of phenol, 3-chlorophenol and o-cresol from aqueous solution by Norit Granular Activated Carbon (NAC 1240)

Activity of water in aqueous systems; A frequently neglected property

In this critical review, the significance of the term ‘activity’ is examined in the context of the properties of aqueous solutions. The dependence of the activity of water(ℓ) at ambient pressure and 298.15 K on solute molality is examined for aqueous solutions containing neutral solutes, mixtures of neutral solutes and salts. Addition of a solute to water(ℓ) always lowers its thermodynamic activity. For some solutes the stabilisation of water(ℓ) is less than and for others more than in the case where the thermodynamic properties of the aqueous solution are ideal. In one approach this pattern is accounted for in terms of hydrate formation. Alternatively the pattern is analysed in terms of the dependence of practical osmotic coefficients on the composition of the aqueous solution and then in terms of solute–solute interactions. For salt solutions the dependence of the activity of water on salt molalities is compared with that predicted by the Debye–Hückel limiting law. The analysis is extended to consideration of the activities of water in binary aqueous mixtures. The dependence on mole fraction composition of the activity of water in binary aqueous mixtures is examined. Different experimental methods for determining the activity of water in aqueous solutions are critically reviewed. The role of water activity is noted in a biochemical context, with reference to the quality, stability and safety of food and finally with regard to health science.

Method for producing oxygen from lunar materials

This invention is related to producing oxygen from lunar or Martian materials, particularly from lunar ilmenite in situ. The process includes producing a slurry of the minerals and hot sulfuric acid, the acid and minerals reacting to form sulfates of the metal. Water is added to the slurry to dissolve the minerals into an aqueous solution, the first aqueous solution is separated from unreacted minerals from the slurry, and the aqueous solution is electrolyzed to produce the metal and oxygen

Prevention of endotoxin-induced uveitis in rabbits by Triphala, an Ayurvedic formulation

Purpose: Triphala (TA) is an Ayurvedic formulation used to treat various disorders. The present study was designed to investigate the anti-inflammatory effect of TA aqueous extract on experimental uveitis in the rabbit. Methods: Anterior uveitis was induced in rabbits by intravitreal injection of lipopolysaccharide from Eschericha coli after pretreatment with TA aqueous extract. Subsequently the anti-inflammatory activity of TA was evaluated by grading the clinical signs and estimating the inflammatory cell count, protein, and TNF-α level in the aqueous humour. Results: The anterior segment inflammation in the control group was significantly higher than in TA and prednisolone treated groups, as observed by clinical grading. The inflammatory cell count in the control group was 31.23 ± 0.80 × 105cells/ml, whereas it was 3.29 ± 0.47 × 105cells/ml (P < 0.0001 vs. control) and 1.31 ± 0.31 × 105 (P < 0.0001 vs. control) cells/ml in the TA and prednisolone treated groups, respectively. The protein content of the aqueous humour was 15.43 ± 0.54, 3.13 ± 0.35 (P < 0.0001 vs. control), and 1.96 ± 0.39 (P < 0.0001 vs. control) mg/ml in the control, TA and prednisolone treated groups respectively. The aqueous TNF- α level in the control group was 942.20 ± 6.46 pg/ml and was 261.30 ± 13.60 (P < 0.001 vs. control) and 104.00 ± 4.50 (P < 0.0001 vs. control) pg/ml in the TA and prednisolone treated groups, respectively. \ud Conclusions: Topical administration of aqueous extract of TA prevented uveitis in endotoxin-induced experimental rabbits.\u

A study on the reaction between CO2 and alkanolamines in aqueous solutions

Literature data on the rates of reaction between CO2 and alkanolamines (MEA, DEA, DIPA, TEA and MDEA) in aqueous solution are discussed. These data induced us to carry out absorption experiments of CO2 into aqueous DEA, DIPA, TEA and MDEA solutions from which the respective rate constants\ud \ud The results for DEA and DIPA were analysed by means of a zwitterion-mechanism which was derived from the mechanism originally proposed by Danckwerts [1\ud \ud The reaction rate of CO2 with aqueous TEA and MDEA solutions shows a significant base catalysis effect which is also reported by Donaldson and Ngu