Ayoa Fernández

Uptake of copper and cobalt in a complexing resin: shrinking-core model with two reaction fronts

The kinetics of simultaneous ion exchange of copper and cobalt with iminodiacetic chelating resins has been studied. Microscopic studies of the ion-exchange process clearly show two different reaction fronts allowing the use of shrinking-core type models. The influence of system parameters is studied both theoretically and experimentally. Experimental results obtained at different total ion concentrations for various copper-cobalt ratios and particle diameters are reasonably predicted by the shrinking-core model, allowing diffusivity calculations.

Equilibrium and simulation of the operation for the adsorption of albumin proteins in an iminodiacetic-Cu bounded ion exchange resin (IMAC)

IMAC (Immobilized Metal Affinity Chromatography) is one of most selective chromatographic techniques for protein retention. In this technique, a complexing resin containing, for example, iminodiacetic groups, is saturated with a metallic ion, and when the solution of proteins is contacted with the saturated resin; the affinity of the proteins for the metallic ions produces the retention of the protein by the support. In the present study, an iminodiacetic resin (Lewatit TP-207) was saturated with copper and the retention of bovine serum albumin and α-lactalbumin was tested. Equilibrium analysis was carried out in column, a constant separation factor isotherm being used to obtain the equilibrium constants. The kinetics was studied in batch experiments; a superficial mass transfer and a pore diffusion model were considered to obtain the mass transfer coefficient in the film and the pore diffusivity. The equilibrium is unfavorable and the kinetics very fast. Finally, breakthrough curves were obtained and modeled with a proposed column model taking into account equilibrium, kinetics and hydrodynamic parameters. The column model adequately fits the experimental breakthrough curves. This resin may be used to retain proteins from wastes from the food industry.

Caseinomacropeptide behaviour in a whey protein fractionation process based on α-lactalbumin precipitation

This work studied the behaviour of caseinomacropeptide (CMP) in a whey protein fractionation process based on the selective precipitation of α-lactalbumin (α-la) in an acid medium. Three different acids (hydrochloric, citric and lactic) and different operating conditions (protein concentration, temperature and pH) were considered to perform the precipitation step. Under the optimised precipitation conditions obtained for α-la (pH 4, 55°C, initial α-la concentration around 12 g/l) CMP presents quite similar behaviour to that observed for β-lactoglobulin (β-lg), namely remaining in the supernatant fraction. However, at a lower pH value (3.5) the amount of precipitated CMP increases up to 72% when citric acid is added. This behaviour could be due to the fact that CMP is close to its isoelectric point, which allows a supernatant fraction enriched in β-lg that is almost free from the rest of proteins in sweet whey.

Advancements in the Fractionation of Milk Biopeptides by Means of Membrane Processes

Nowadays the most common way to obtain bioactive peptides is by enzymatic hydrolysis of protein solutions. The most studied substrates used to produce bioactive peptides are milk proteins in the form of co-products from dairy industries: caseins, cheese whey, buttermilk, whey protein concentrates and isolates or even pure single proteins that can be obtained at a reasonable price on an industrial scale (e.g. β-lactoglobulin, β-Lg).

EQUILIBRIUM OF METALS WITH IMINODIACETIC RESIN IN BINARY AND TERNARY SYSTEMS

ABSTRACT Experiments of binary and ternary ion exchange equilibrium of heavy metals and sodium were carried out in a complexing iminodiacetic resin Lewatit TP 207. First, binary equilibrium data were obtained at different temperatures and ionic strength and fixed to models considering two different ion exchange stoichiometrics. For ternary equilibrium data, two distinct simple models were applied. One to be applied to systems showing very different selectivity for the metals (for instance, Cu2+/Co2+/Na+) and the other for systems with similar selectivity for the metals (such as Zn2+/Co2+/Na+). The ternary equilibrium data obtained is presented in this work and fitted using the two above mentioned models. These models allow us to obtain the equilibrium parameters for binary and ternary system to be used in the design of equipment using this iminodiacetic resin.

Hydrometallurgy Wastewater Split-Up by Fluidized-Bed Ion-Exchange Continuous Equipment

ABSTRACT A proposed operation of a semicontinuous fluidized-bed ion-exchange system was studied. The system splits a liquid current into two currents, one being more concentrated and the other more depleted. This operating technique has been used to split up a mixture of alkaline ions (Na+, K+) using a strongly acidic resin. The equipment operates simultaneously in two multistage columns, one for loading and the other for elution of the resin. The experimetal testing system employs a hydrometallurgy wastewater containing cobalt and copper as heavy metallic ions, and the resin used was of the chelating iminodiacetic type, Lewatit TP-207. At cyclic steady state, the equipment can split up the wastewater, producing an effluent concentrated in cobalt in the outlet stream of the loading column, and a concentrated stream of copper in the effluent of the elution column. The hydrodynamics and approach to the stationary state of the system were analyzed, and the selective recovery of metals was subsequently tested...