Gerardo León

Facilitated transport of cobalt through bulk liquid membranes containing diethylhexyl phosphoric acid

Abstract The transport of cobalt (II) ions through bulk liquid membrane containing di(2-ethylhexyl) phosphoric acid (D2EHPA) in kerosene as mobile carrier and protons as counterions in the product phase (H 2 SO 4 was studied. The transport kinetics was analysed by means of a kinetic model involving two consecutive irreversible first order reactions. The rate constants of the extraction and stripping reactions were experimentally determined. Model curves of tune dependence of Co (II) reduced concentrations in the feed, membrane and product phases show good agreement with the experimental data. The influence of the carrier concentration in the membrane phase and the counterion concentration in the product phase was analysed. The increase of both led to an increase in the recovery of cobalt (II), the optimal conditions in the range studied being 6% v/v of D2EHPA in the membrane phase and 1 M sulphuric acid in the product phase.

Reduction of sulphate content in aqueous solutions by reverse osmosis using cellulose acetate membranes

Abstract The contamination of water by sulphate is a pollution problem that has increased in severity in recent decades. The behaviour of cellulose acetate membranes in the treatment by reverse osmosis of aqueous sulphate solutions is described. Experimental essays were performed in a commercial cross flow test module in which solutions of sulphate of con-centrations between 0.145 kg/m 3 and 25.455 kg/m 3 were treated. Recycling of both the concentrate and permeate was carried out in order to keep the concentration constant and to simulate a continuous process in a quasi-stationary state. A simulation model described for a semi-batch and unsteady-state system was applied to our experimental conditions (batch and steady-state mode) and verified. The model uses the solution diffusion approach to depict the mass transfer through the membrane, while the constants are determined experimentally. Good agreement between the experimental and model results was obtained, so that the model can be considered suitable for simulating of reverse osmosis treatment of aqueous sulphate solutions by cellulose acetate membranes in the concentrations range studied.

Increasing stability and transport efficiency of supported liquid membranes through a novel ultrasound-assisted preparation method. Its application to cobalt(II) removal.

A novel ultrasound assisted method for preparing supported liquid membranes is described in this paper. The stability and efficiency of the supported liquid membrane obtained was tested by removing cobalt(II) from aqueous solutions through a facilitated countertransport mechanism using CYANEX 272 as carrier and protons as counterions. The results are compared with those obtained using supported liquid membranes prepared by soaking the polymeric material in the organic solution of the carrier at atmospheric pressure and under vacuum, both for 24h. Higher transport efficiency (>5%), flux (∼18%), permeability (∼20%) and stability (>6% in the second run and ∼10% in the third run) were obtained by the supported liquid membrane prepared using the ultrasound assisted method. These findings can be explained by the effects of cavitation and acoustical streaming - which result from the ultrasound passing through the organic solution of the extractant - on the porous structure of the polymer support and on the pore filling.

Application of the solution-diffusion model for the removal of atrazine using a nanofiltration membrane

Abstract The solution-diffusion model was used to predict the behaviour of four nanofiltration membranes, two were made of polyamide (NF-99 and NF-97) and the other two were made of polypiperazineamide (DL and DK), when used for the removal of atrazine from aqueous solutions. The mass transfer model applied is very simple and its linearization facilitates rapid calculation of the relevant parameters. The two main parameters, permeate concentration and volumetric permeate flux, are obtained from three different coefficients: water permeability, A w, solute permeability, B s, and osmotic pressure coefficients, Ψ. Good agreement between the experimental and the predicted atrazine concentrations was obtained for the NF-99, DL and DK membranes when the concentration was low. However, only the NF-99 membrane provided accurate values for the two main parameters in the whole range of concentrations studied, which suggests that the solution-diffusion model can only be applied to this membrane.

Removal of 4-chloro-2-methylphenol from aqueous solutions by nanofiltration and reverse osmosis

AbstractChloromethylphenols are typical phenolic pollutants frequently found in wastewater treatment plants and industrial landfill leachates, while pressure-driven membrane processes have been demonstrated to be a practical and competitive alternative for their removal. The performance of two membranes (an NF99 nanofiltration membrane and an RO99 reverse osmosis membrane) for removing 4-chloro-2-methylphenol (4C2MP) from synthetic solutions at different pressures, feed concentrations and feed pH values is compared in this paper using permeate flux and rejection as representative parameters. Higher permeate fluxes were obtained with the NF99 membrane but higher rates of 4C2MP rejection were obtained with the RO99 membrane. There was a substantial increase in 4C2MP rejection as the pH was increased from 8 to 11 in the case of the NF99 membrane. The results are explained by the different chemical structures of the active layers of both membranes.