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- Andersson, M., et al.
(författare)
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A New Class of Labile Surfactants that Break Down to Non-surface Active Products upon Heating or after a Pre-set Time, without the Need for a pH Change
- 2007
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Ingår i: Tenside Surfactants Detergents. - : Walter de Gruyter GmbH. - 0932-3414 .- 2195-8564. ; 44:6, s. 366-372
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Tidskriftsartikel (refereegranskat)abstract
- A new class of labile surfactants that break down at a controllable rate without the need for a change in pH will be presented. The invention has been patented by YKI Institute for Surface Chemistry, and is based on use of β-keto acids or their salts as surface-active compounds. These surfactants spontaneously break down through decarboxylation, to form an oil-like ketone and CO 2/HCO 3 -/CO 32 - depending on pH. The rate of breakdown can be controlled within a wide range by temperature or by certain additives, but, unlike most cleavable surfactants, a change in pH is not needed. Furthermore the surfactants can be conveniently activated from a stabile precursor just before use, and one (of many possible) precursors of this kind is already available on the industrial scale in the form of a wellknown chemical that is FDA-approved in other, non-surfactant, applications. The compound in question, alkyl ketene dimer (AKD), is produced in large scale by a number of large chemical producers today, and used for hydrophobization of paper. The present article gives an overview of the surfactant chemistry, with focus on recent studies of the kinetics of activation of the surfactant precursor and breakdown kinetics of the labile surfactant at different conditions. Furthermore, possible industrial applications of the surfactant will be discussed, with one example taken from a recent feasibility study performed within the car washing area. © Carl Hanser Publisher.
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| 3. |
- Younesi, S. R., et al.
(författare)
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Kinetic mechanisms of cementation of cadmium ions by zinc powder from sulphate solutions
- 2006
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Ingår i: Hydrometallurgy. - : Elsevier BV. - 0304-386X .- 1879-1158. ; 84:3–4, s. 155-164
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Tidskriftsartikel (refereegranskat)abstract
- The cementation of cadmium ions by zinc powder was studied in a batch reactor at low and high concentrations at pH 5.2–5.4 and it is shown that the reaction is first-order. XRD and SEM analysis confirm that the deposited layer is metallic with no evidence of basic zinc sulphate or re-dissolution of cadmium. Dependence of the reaction constant on initial cadmium concentration proves the reaction mechanism. Different possible kinetic controlling models of cadmium ion (Cd2+) cementation from aqueous solution by zinc powder were studied with respect to initial cadmium concentration, temperature, zinc powder size and stoichiometric ratio. The experiments demonstrate that at initial cadmium concentrations > 1000 ppm, the ash diffusion control model prevails, while at concentrations < 500 ppm, the data has good agreement with the film diffusion model. For concentrations between 500 ppm and 1000 ppm, a combination of ash diffusion and film diffusion models controls the reaction rate. Based on numerical analysis, the calculated activation energies at high and low concentrations are 9.6 and 7.2 kJ/mol, respectively. Statistical data analysis was performed and different reaction rate constants were estimated from the equations for high and low initial cadmium concentrations.
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