Effects of pH and temperature on the sorption of sodium dodecyl sulfate by cellulose acetate/polyaniline blend membranes

Pereira, Rui F. P.; Cerqueira, Daniel Alves; Valente, Artur J.M.; Polishchuk, A. Ya.; Lobo, Victor M.M.

doi:10.1002/app.29223

Cited by 4 publications

(1 citation statement)

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“…At higher molar ratios, Δκ S–M reaches a plateau, meaning that the specific electrical conductances of the mixed solutions are similar to those observed with surfactant solutions in the absence of metal ions. These results clearly imply that carboxylate–metal ion interactions are controlled by charge neutralization and that the interaction involves removal of free metal ion from solution, similar to what was observed with trivalent metal ions and decyl and dodecyl sulfates. , …”

Section: Resultssupporting

confidence: 71%

Effect of Metal Ion Hydration on the Interaction between Sodium Carboxylates and Aluminum(III) or Chromium(III) Ions in Aqueous Solution

2011

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The interaction between sodium octanoate, decanoate, and dodecanoate and aluminum(III) and chromium(III) has been studied in water at natural pH values, starting well below the surfactant critical micelle concentration, using electrical conductivity, turbidity, and potentiometric measurements. With decanoate or dodecanoate, maximum interaction occurs at 3:1 stoichiometry, corresponding to charge neutralization. Although the solutions become turbid with both metal ions, indicating phase separation, differences are observed and attributed to the fact that aluminum(III) is relatively labile to substitution and rapidly replaces its water ligands, whereas chromium(III) is substitution inert. This shows up in well-defined floc formation with Al(3+), whereas Cr(3+) suspensions do not precipitate, probably because that replacement of coordinated water by carboxylate ligands is impeded. This can be overcome by increasing temperature, and differences in the thermal behavior with Al(3+) and Cr(3+) are suggested to be due to increased involvement of substitution reactions in the latter case. The effect of octanoate on the trivalent metal ions is less clear, and with Cr(3+) interaction only occurs when the carboxylate is in excess. Hydrophobic interactions between alkyl chains play a major role in driving phase separation. At high surfactant concentrations, the solid phases do not dissolve, in contrast to what is observed with the corresponding alkylsulfates. This has implications for use of these systems in metal separation through froth flotation. The concentration of metal ions in supernatant solution has been determined for sodium dodecanoate and sodium dodecylsulfate with Al(3+) and Cr(3+) over the whole surfactant concentration range by inductively coupled plasma-mass spectrometry (ICP-MS). From this, association constants have been determined and are found to be larger for the carboxylate than the alkylsulfate, in agreement with the greater Lewis basicity of the -CO(2)(-) group.

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Section: Resultssupporting

confidence: 71%