The effect of DTAC on the extraction of Co(II) with Cyanex272 in a neutral micellar phase

• Two-step mechanism was found to describe the rate of Co(II) extraction by Cyanex272.
• The addition of a cationic surfactant, DTAC slowed the rate of extraction.
• Rate influenced by surfactants, has been modelled by changes in surface potential.

The equilibrium constant, Kex for the complexation between Co(II) and Cyanex272 in a neutral micelle system, Teric G12A8 (octa-ethylene glycol mono-n-dodecyl ether) was determined and the rate of the reaction was monitored using a combination of stopped flow and UV–vis spectrophotometry. A two-step mechanism was found to fit the experimental data and reaction rate constants for the forward and reverse reactions were obtained. The addition of a cationic surfactant, dodecyl trimethyl ammonium chloride (DTAC) slowed the rate of Co(II) extraction. The effect of charge on the reaction rate could be modelled based on the electrostatic surface potential generated by the added surfactant.

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