Effect Of Organic Species Research Articles

Molecular dynamics investigation on structural and interfacial characteristics of aerosol particles containing mixed organic components

Microscopic morphology plays a significant role in the description of aerosol particle evolution, but the knowledge on particles containing mixed organic matters is insufficient. In this study, molecular simulation (MD) method is employed to investigate the morphologies of particles containing two or three of malonic acid (MA), adipic acid (AA) and eicosane (C20). The key point is the effects of organic species and water content on structural and interfacial characteristics of particles. Results show that all dry particles exhibit the approximate core-shell structure with the shell composed of organic with longer hydrocarbon chain. With water content increasing from 100 to 1000, MA + AA + H2O particles present the core-shell structure with decreasing MA in the core, while particles containing C20 successively exhibit the core-shell structure and the ball-cap structure with three layers. These structural differences are caused by the surface propensity of organics, which is positively correlated with both the length of hydrocarbon chain and the water content. At the particle surface, hydrophobic groups of organic molecules direct towards the gas phase. MA (AA) located between water droplet and C20 cluster orient their hydrophobic groups toward C20. Furthermore, ratios of hydrophilic and hydrophobic atoms (K) at the surface of all studied particles increases with increasing water content, and at each water content the order is K(MA + AA) > K(MA + AA + C20) > K(AA + C20) > K(MA + C20). These findings provide microscopic information support for the development of theoretical model for the particle formation and growth.

Investigation into composition and deposition of artificially produced marine aerosols on austenitic stainless steels

This study focused on the effect of organic species on the occurrence of atmospheric-induced stress corrosion cracking (AISCC) in intermediate level waste (ILW) container materials under ‘wetted’ deposits of artificial sea-water (SW). Artificial SW solutions enriched with one of two bio-exudates – with organic carbon concentrations of between 92 and 451 μM – were employed to investigate changes in interfacial behaviour, associated with organic content, at the liquid–solid boundary on type 304L stainless steel (SS). These effects were determined in terms of contact angle and deposit diameter. On evaporation organically-enriched SW droplets deposited on 304L SS maintain a constant contact diameter on exposure to a relative humidity (RH) of 70±1%. By contrast deposits produced from artificial SW alone contract radially inwards. The bio-exudate that remained on the SS surface following the cleaning of deposits formed from organically enriched SW was visualised via cyanoacrylate fuming. This technique confirmed that bio-exudate adheres to 304L SS after removal of the inorganic components. The impact of organic enrichment on AISCC was investigated using droplets of test solutions on 304L U-bend specimens exposed to environmental conditions of 50·0±0·5°C and 30±1% RH.

Corrosion behavior of metallic materials in biomedical applications. I. Ti and its alloys

AbstractThe use of metallic materials for implantable medical devices has prompted numerous studies aimed at characterizing the corrosion susceptibility of these materials and understanding their electrochemical behavior in simulated and actual physiological liquids. This review focuses on the forms of corrosion that are of principal interest for Ti and its alloysin vivo: general corrosion, pitting corrosion, crevice corrosion, galvanic corrosion, and fretting corrosion. It also addresses environmentally assisted cracking in the form of hydrogen embrittlement. Of particular interest is the susceptibility of Ti and its alloys to the different forms of corrosion with regard to both solution chemistry, especially the effect of organic species, and surface characteristics such as oxide composition, surface inclusions, and wear/fretting.

Effect of organic species on the solar detoxification of water polluted with pesticides

The effect of organic species on a solar-driven photo-Fenton treatment of a mixture of pesticides (methyl-oxydemethon, methidathion, carbaryl and dimethoate) has been studied in this paper. Triethoxyisododecyl alcohol, acetophenone and ethylenediaminetetraacetic acid (EDTA) have been used as examples of surfactants, solvents and complexing agents, respectively. An inhibitory effect on mineralization as well as on the elimination of the pesticides was observed in the case of the aliphatic surfactants, most probably due to the competition between the pesticides and the added organic matter for reaction with the relatively unselective hydroxyl radical. A methodology combining chemical analyses and bioassays was tested in order to explore the applicability of coupling a photo-Fenton process with a biological treatment in the presence of the surfactant. Despite the complexity of the mixture under study, a reliable monitoring of the process was accomplished; the biocompatibility of the mixture was enhanced and the optimal irradiation intensity was achieved just after complete removal of the pesticides.

The effects of organic species on the hygroscopic behaviors of inorganic aerosols.

Water-soluble organic compounds have recently received much attention because of their ability to absorb water and alter the hygroscopic properties of inorganic aerosols. The effects of glycerol, succinic acid, malonic acid, citric acid, and glutaric acid on the water cycles (water activities during particle evaporation and growth), crystallization relative humidities (CRH), and deliquescence relative humidities (DRH) of sodium chloride (NaCl) and ammonium sulfate (AS) were studied using an electrodynamic balance (EDB). The growth factors of these inorganic and organic mixtures were lower than those of the pure inorganic species. The presence of all these organics in the mixed particle reduce the water absorption of NaCl but enhance that of AS relative to that of the pure inorganic salts. Glycerol and succinic acid did not affect the deliquescence properties of NaCl and AS, although succinic acid increased the CRH of NaCl and AS. Malonic acid and citric acid, behaving as nondeliquescent species in single particle studies, caused NaCl and AS particles to absorb a significant amount of water before deliquescence. Glutaric acid caused NaCl and AS to deliquesce gradually, spanning a wide range of relative humidity. The ZSR model was found to be useful in predicting the water activity of the mixtures and the growth ratios. However, the detailed crystallization and deliquescence behaviors of the organic/inorganic mixtures cannot be easily predicted from the hygroscopic properties of the individual components.

The Application of Calcium Phosphate Precipitation Chemistry to Phosphorus Recovery: The Influence of Organic Ligands

This paper describes current knowledge of phosphate precipitation chemistry in the context of phosphorus recovery from wastewaters, and presents experimental results on the effect of organic species, as key potential inhibitors, to the precipitation of calcium phosphate. The supersaturation required for precipitation at 25°C, pH 7, 0.1 M ionic strength and near-stoichiometric (for hydroxylapatite) calcium to phosphate molar ratio was determined under spontaneous precipitation conditions. The experiments were carried out in air. The phase precipitating at the critical concentration was allowed to grow under constant supersaturation. The influence of organic ligands on the precipitation was investigated using two small molecular weight organic ligands, acetate and citrate, present at a concentration of 10−3 M. The precipitate was studied using X-ray diffraction and scanning electron microscopy. Good reproducibility of the experiments, which were carried out in triplicate, was observed. The study assessed the supersaturation necessary for spontaneous precipitation of hydroxylapatite to be 10.93, calculated using a solubility constant of log K=−57.74. The required supersaturation was not affected by the presence of acetate. However, citrate was found to increase the supersaturation required for precipitation to 11.73. It is likely that this increase is due to binding of citrate on the active growth sites of newly formed nuclei, thereby inhibiting precipitation. All experiments showed formation of a single phase: micro-crystalline hydroxylapatite.

Effect of Organic Additives or Counterions on the Supramolecular Assembly Structures Constructed by Amphiphiles. A Small-Angle Neutron Scattering Investigation

Small-angle neutron scattering (SANS) was measured for aqueous solutions of amphiphiles with organic additives or counterions such as 2-indenecarboxylic acid, cinnamic acid, and salicylic acid or their ions. The effect of organic species on the supramolecular assembly structure was investigated. Equimolar mixtures of dodecyldimethylamine oxides and aromatic carboxylic acids constructed vesicles. The vesicular bilayer thicknesses were 29−30 A, independent of organic species. On the other hand, hexadecyltrimethylammoniums with aromatic carboxylate counterions always formed rodlike micelles with axial ratios 8−10. Aqueous solutions of tetradecyltrimethylammonium salicylate displayed a strong interparticle interference effect on SANS profiles at concentrations above 0.8 × 10-2 g cm-3, although such an effect disappeared with addition of more than 5/mM sodium salicylate.

Effect of organic species on the synthesis and properties of ZSM-5

The synthesis and properties of ZSM-5 zeolites crystallized from the reaction mixture 10Na 2 O Al 2 O 3 60SiO 2 3000H 2 O 10 organic (organic = tetrapropylammonium bromide, hexane-1, 6-diol, hexane-1, 6-diamine or piperazine) at 150°C are compared with those of ‘organic free’ ZSM-5. It is shown that the organic species has a marked effect on the composition and excess cation content of the product. Only the tetrapropylammonium ion is considered to be a true structure directing template, piperazine and hexane-1, 6-diol act as hydrophobic void fillers, and hexane-1, 6-diamine holds an intermediate position.