N. Miralles

Heavy metal uptake from aqueous solution by cork and yohimbe bark wastes

In this work the ability of cork and yohimbe bark wastes to remove Cu(II) and Ni(II) from aqueous solutions has been studied. The influence of pH, sodium chloride and metal concentration on metal uptake was investigated. Metal uptake showed a pH-dependent profile. Maximum sorption for both metals was found to occur at around pH 6–7. In the case of cork an increase of sodium chloride concentration provoked a decrease in metal removal. Adsorption isotherms at the optimum pH were expressed by the non-competitive Langmuir adsorption model, and model parameters were determined. It was seen that the adsorption equilibrium data fitted very well to the model in the concentration range studied. When comparing both biomaterials, yohimbe bark waste was found to be the most efficient adsorbent for both metals studied. © 2000 Society of Chemical Industry

Modelling of mass transfer in facilitated supported liquid membrane transport of gold(III) using phospholene derivatives as carriers

Abstract An experimental study of gold(III) transport through solid-supported liquid membranes using phospholene derivatives as carriers has been performed using batch experiments. A model is reported describing the transport mechanism which consists of a diffusion process through a feed aqueous diffusion layer, a fast interfacial chemical reaction and a diffusion of HAuCl 4 L and HAuCl 4 L 2 through the membrane. The mathematical equations describing the rate of transport are derived and correlate the membrane permeability coefficient to diffusional and equilibrium parameters as well as the chemical composition of the system, such as extractant concentration in the membrane phase and HCl concentration in the feed phase. The experimental data are explained with the derived equations, and the diffusion resistances to mass transfer are evaluated. The influence in the transport of stirring speed in the feed phase, the nature of the diluent and stripping agent, and the type of polymeric support have been also discussed.

Solvent impregnated resins containing Cyanex 272. Preparation and application to the extraction and separation of divalent metals

Abstract Impregnated resins containing di-(2,2,4-trimethylpentyl)phosphinic acid (Cyanex 272) were prepared by adsorption of the extractant into Amberlite XAD-2 polymeric adsorbant. The distribution of Cyanex 272 between the aqueous and resin phase was studied as a function of pH and loading of the organophosphorous extractant on the resin. The concentration of organophosphorous compound was determined by ICP. XAD-2-Cyanex 272 impregnated resins were tested for the recovery and separation of Zn(II), Cd(II) and Cu(II) from aqueous solutions. The distribution coefficient of Zn(II), Cd(II) and Cu(II) between the aqueous phase and the resin phase were determined under different conditions. The separation factors between the three metal ions are sufficiently large to allow effective separation of Zn from Cd (100%) and Cu (90%). The selective recovery of Zn(II) from aqueous solutions has been carried out by using SIR as the column stationary phase. The retained metal ions were released from the resin quantitatively by elution with hydrochloric acid solutions at the correct concentration for each metal ion.

Solid-liquid extraction studies of divalent metals with impregnated resins containing mixtures of organophosphorus extractants

The extraction of Zn(II), Cu(II) and Cd(II) from nitrate solutions by impregnated resins containing mixtures of di(2-ethylhexyl)phosphoric acid (DEHPA) and tri-n-octyl-phosphine oxide (TOPO) have been studied. Impregnated resins containing TOPO and mixtures of DEHPA and TOPO have been prepared by direct adsorption of both extractants into macroporous supports, Amberlite XAD2. The adsorption of DEHPA and TOPO molecules on the macroporous support is shown by FTIR spectroscopy to be result of only weak extractant-support interactions. The distribution coefficients of Zn(II), Cu(II) and Cd(II) were determined as a function of pH and extractant concentration (DEHPA, TOPO) in the resin phase and the data were analyzed graphically using the slope analysis method in terms of synergistic effect. Analysis of the results showed that the extraction of these metal ions can be explained assuming the formation of metal complexes in the resin phase with a general composition MLp(NO3)tSs(HL)q where p, t, s, q take values depending on the metal and the extractant concentration ratio in the resin phase ([HL]r[S]r).

KINETIC STUDIES ON HEAVY METAL IONS REMOVAL BY IMPREGNATED RESINS CONTAINING DI-(2,4,4-TRYMETHYLPENTYL) PHOSPHINIC ACID

ABSTRACT Kinetics measurements on the extraction of divalent metal ions (Zn, Cu and Cd) with impregnated resins prepared by adsorption of di(2,4,4-tri-methylpentyl)phosphinic acid (DTMPPA=HL) onto a macroporous polymeric support of Amberlite XAD2 were made. The extraction process is accompanied by fast chemical reaction and is characterized by a sharp moving boundary between the reacted shell and the shrinking unreacted core within the impregnated resin. Analyses of the respective rate data in accordance with two theoretical models used to explain the metal extraction kinetics showed that process is controlled by the rate of difilision of the ions penetrating the reacted layer at high metal ion concentration (1×10−2 mol.L−1) and controlled by the rate of diffusion of the ions across the liquid film surrounding the resin particle at low metal ion concentration (1×10−4 mol.L−1). Particle diffusion coefficients and mass transfer constants across the liquid film were determined from the graphical representati...

Solid-liquid extraction studies of Zn(II), Cu(II) and Cd(II) from chloride media with impregnated resins containing mixtures of organophosphorus compounds immobilized on to Amberlite XAD2

Abstract The solid-liquid extraction of Zn(II), Cu(II) and Cd(II) from chloride medium at 0.1 and 0.5 M inonic strength and 25°C by impregnated resins containing mixtures of di(2-ethylhexyl)phosphoric acid (DEHPA = HL) and tri-n-octylphosphine oxide (TOPO = S) was studied. Impregnated resins containing TOPO and mixtures of DEHPA and TOPO, by direct adsorption of both extractants into a styrene/divinylbenzene macroporous support, Amberlite XAD2, using the dry impregnation method, were prepared. The distribution coefficients of Zn(II), Cu(II) and Cd(II) were determined as a function of pH, chloride concentration in the aqueous phase and extractant concentration (DEHPA and TOPO) in the resin phase and the data were analyzed graphically using the slope analysis method in terms of synergistic effect. Analysis of the results showed that the extraction of these metal ions with resins containing mixtures of DEHPA and TOPO (XAD2-DEHPA-TOPO) can be explained assuming the formation of metal complexes in the resin phase with a general composition MCl t L p (HL) q S s where, p , t , s and q take different values depending on the metal and the extractant concentration ratio in the resin phase ([HL] r /[S] r ). Finally, a comparison between the extraction of Zn(II), Cu(II) and Cd(II) in terms of the separation factors with Amberlite XAD2-DEHPA-TOPO resins and using Amberlite XAD2-DEHPA resins was made.

SOLVENT IMPREGNATED RESINS CONTAINING DI(2-ETHYL-HEXYL)PHOSPHORIC ACID.II. STUDY OF THE DISTRIBUTION EQUILIBRIA OF Zn(II), Cu(II) AND Cd(II).

ABSTRACT The extraction of Zn(II), Cu(II) and Cd(II) from nitrate solutions at 0.1 M ionic strength by impregnated resins containing di(2-ethylhexyl)phosphoric acid has been studied at 25 °C. The distribution coefficient was determined as a function of both pH and extractant concentration in the resin phase. The data were analyzed graphically using the slope analysis method, and numerically using the program LETAGROP-DISTR. The composition of the extracted species in the resin phase has been determined. Analysis of the results showed that the extraction of these metal ions can be explained assuming the formation of metal complexes in the resin phase with a general composition ML2(HL) q where q takes different values depending on the metal. An extraction reaction is proposed and the extraction constants of these species are given. Finally, a comparison between the extraction of Zn(II), Cu(II) and Cd(II) by di(2-ethylhexyl)phosphoric acid into Amberlite XAD2 and the extraction using organic solvents has bee...

EXTRACTION OF DIVALENT METALS WITH BIS(2,4,4 TRIMETHYLPENTY) PHOSPHINIC ACID

ABSTRACT The extraction of Cd(II), Cu(II) and Zn(II) from 0.1 mol dmminus3 aqueous nitrate solutions with bis(2,4,4-trimethylpentyl)phosphinic acid (HBTMPP) dissolved in Isopar-H has been studied with relation to the total extractant concentration, the equilibrium pH and the total metal concentration in the aqueous phase. The stoichiometry of the extracted species and their equilibrium constants have been determined by graphical and numerical methods and appear to be CdA2 (HA)2 and CdA2 (HA)3 for Cd(II), CuA2(HA)2 for Cu(II) and ZnAzHA and ZnAz(HA)2 for Zn(II). The extraction efficiency follows the order Zn(II)

Extraction studies of Zn(II), Cu(II) and Cd(II) with impregnated and Levextrel resins containing di(2-ethylhexyl) phosphoric acid (Lewatit 1026 Oc)

Impregnated resins are an alternative approach to the usual techniques for the recovery of metal ions, such as solvent extraction and ion exchange resins. This paper presents the results of the extraction of Zn(II), Cu(II) and Cd(II) from nitrate and chloride solutions at 0.1 M ionic strength and 25°C by the Levextrel impregnated resin Lewatit 1026 Oc containing di(2-ethylhexyl)-phosphoric acid (DEHPA). The distribution coefficients were determined as a function of both pH and ionic medium and the data were analyzed graphically, using the slope analysis method, and numerically using the program letagrop-distr. Analysis of the results shows that the extraction of these metal ions can be explained assuming the formation of metal complexes in the resin phase have a general composition ML2(HL)q where q takes different values depending on the metal. An extraction reaction is proposed and the extraction constants of the species are given. The adsorption of DEHPA molecules on the styrene/divinyl benzene macroporous support is due to weak extractant-support interactions, as indicated by FTIR spectroscopy. Furthermore, it is also shown that the ability of the extractant towards Zn(II), Cu(II) and Cd(II) changes in the solid support, in comparison with organic solvents. Finally, a comparison is made between the extraction of Zn(II), Cu(II) and Cd(II) with Lewatit 1026 Oc resins and impregnated resins prepared by direct adsorption of DEHPA into Amberlite XAD2 (XAD2-DEHPA resins).

Solvent-impregnated resins containing di-(2,4,4-trimethylpentyl) phosphinic acid II. Study of the distribution equilibria of Zn(II), Cu(II) and Cd(II)

Abstract The extraction of Zn(II), Cu(II) and Cd(II) from nitrate solutions at 0.1 ionic strength by impregnated resins containing di-(2,4,4-trimethylpentyl)phosphonic acid (HL) has been studied at 25°C. The distribution coefficient of the metal ion was determined as a function of both pH and extractant concentration in the resin phase, and the data were analyzed graphically using the slope analysis method and numerically using the program LETAGROP-DISTR. Analysis of the results showed that the extraction of these metal ions can be explained by the formation of metal complexes in the resin phase with a general composition ML2(HL)q where the value of q depends on the metal. Extractions reactions are proposed and the extraction constants of these reactions are presented. Finally, a comparison between the extraction of Zn(II), Cu(II) and Cd(II) with di-(2,4,4-trimethylpentyl)phosphinic acid sorbed into Amberlite XAD-2 and the extraction using an organic solvent as Isopar H has been made.