Use of bulk liquid membranes for the removal of aspartame from aqueous media

A chloroform bulk liquid membrane and Aliquat 336 ionic liquid as a carrier (ligand) were used to remove aspartame (ASP) from an aqueous solution. Experiments were performed in a tube-in-tube setup, under mechanical stirring of inner tube (200 rpm), for 7 h. The inner tube contained a stripping phase (an aqueous solution of HCl) and the outer tube the liquid membrane at the bottom and a feed phase (an aqueous solution of ASP and NaOH) at the top. Maximum extraction, stripping, and recovery efficiencies of ASP of 97.0 %, 75.4 %, and 73.1 % were obtained under the following working conditions: initial concentrations of ASP and NaOH in the feed phase of 10(-4) mol/L and 10(-2) mol/L, respectively, initial concentration of Aliquat 336 ligand in the chloroform membrane of 10(-2) mol/L, and initial concentration of HCl in the stripping phase of 10(-2) mol/L. A characteristic kinetic model of consecutive irreversible first-order reactions was used to predict ASP concentrations in the phases of the membrane system under optimal conditions. The extraction and stripping rate constants (k(1) = 2.48 x 10-4 s(-1) and k(2) = 0.574 x 10-4 s(-1)), i.e., the model parameters determined from experimental data, suggested that the chemical reaction occurring at the interface between the membrane and stripping phase was the rate-limiting step in the mass transfer of ASP.