María O. Ruiz

α-Phenylglycine Extraction with Trialkylmethylammonium Chloride Free and Immobilized in a Macroporous Resin: 1. Equilibria

The phase equilibria of α-phenylglycine in sodium hydroxide solutions at pH =11 and 12 with the extractant trialkylmethylammoniumchloride (Tomac) dissolved in kerosene and toluene and with Amberlite XAD-4 resin coated with Tomac at 30°C is reported.The extraction of α-phenylglycine and co-extraction of hydroxyl ions take place simultaneously by ion exchange reactions with the extractant. Phase equilibria are discussed as a function of α-phenylglycine concentration, pH of the aqueous phase and Tomac concentration either in the organic phase or in resin phase. An equilibrium model, which considers the hydroxyl ion co-extraction, has been used for the correlation of the equilibrium data.

Valeric Acid Extraction with Tri‐N‐butyl Phosphate Impregnated in a Macroporous Resin. I. Equilibrium and Mass Transfer Rates

Abstract Equilibrium and mass transfer data for the extraction of valeric acid from aqueous solutions containing less than 2.5 wt% of acid with a macroporous fresh resin, Amberlite XAD‐4, and containing tri‐N‐butyl phosphate (TBP) at 25°C are reported. An equilibrium model, which takes into account the valeric acid physical adsorption by the resin (Freundlich isotherm) and the reactive extraction with the TBP inside the pores, provided a good correlation of experimental data. Valeric acid extraction rates were comparatively faster under the initial conditions of higher TBP concentration in the resin and lower concentration of acid in the aqueous phase. Intraparticle effective diffusivities were determined using a homogeneous mass‐transfer model. A heterogeneous diffusion model which considers parallel diffusion of the TBP–valeric acid complex in the organic phase inside the particle pores and surface diffusion of the valeric acid in the polymeric structure of the resin was employed to derive the pore diffusivity and solid surface diffusivity. Both diffusivities were of the same order of magnitude (10−11 m2/s) showing that both diffusion paths in parallel make significant contributions to the intraparticle mass transfer of valeric acid in the extractant‐impregnated resins (EIR).

α-Phenylglycine extraction with a trialkylmethylammonium chloride-impregnated macroporous resin. 2. Kinetics

The sorption rates of α-phenylglycine in sodium hydroxide solutions by Amberlite XAD-4 resin impregnated with trialkylmethylammonium chloride (Tomac), at pH 11 and 12 at 30°C, have been investigated in a batch stirred tank. By using a modified shrinkingcore model that considers reversibility of the sorption process, it was shown that the amino acid sorption was controlled by particle diffusion. A more rigorous diffusion model was also used; both models led to similar diffusion coefficient values. The amino acid uptake was comparatively faster under the initial conditions of higher Tomac concentration in the resin, higher amino acid concentration in the aqueous phase and at pH = 11.

Application of Crossflow Ultrafiltration to Emulsion Separation in the Extraction of Valeric Acid with Tri-n-butyl Phosphate

Extractive ultrafiltration (EUF) of valeric acid from aqueous solutions with tri-n-butyl phosphate dissolved in kerosene, at two different phase ratios and using two ceramic membranes, was studied. The membranes used were ZrO2 supported on α-alumina and ZrO2 + TiO2, supported on carbon with an average pore size of 20 and 45 nm, respectively. Permeation rates and degree of extraction were determined under three different modes of operation of the membrane unit: total recirculation, permeate removal, and continuous operation.