Influence of anionic surfactants on the extraction rate of lactic acid by alamine 336

Extraction rates of lactic acid from aqueous solutions using Alamine 336 dissolved in toluene have been studied by the single drop technique. Interfacial tensions as a function of extractant concentration and initial extraction rates as a function of lactic acid and Alamine 336 concentrations are reported. Assuming the extraction takes place by an interfacial reaction mechanism, a mass transfer model is proposed for lactic acid reactive extraction. The model assumes a mixed regime, in which the slow diffusion transport of the amine extractant to the inner drop interface, and its protonation at the inter-face are the rate controlling steps. The influence of a synthetic anionic surfactant, sodium n-dodecyl sulphate, on the extraction process has been also studied. For surfactant concentrations above the specific CMC (critical micelle concentration), the surfactant increases the overall mass-transfer rate up to 30%. The surfactant influence on the extraction kinetics is described on the basis of increasing the interfacial potential and the resulting rise of the proton concentration at the interface.