Hacène Kerdjoudj

Modification of the cation exchange resin properties by impregnation in polyethyleneimine solutions: application to the separation of metallic ions.

A commercial cation exchange resin Amberlite 200 has been modified after immersion in solutions of polyethyleneimine (PEI). The kinetic of fixation of the metallic ions have been determined. The modification of the surface of the resin deals with a change in the order of the affinities of the resins towards cations. The retention is the function of the formation and the stability of the complex. The conditions of modification (pH, PEI concentration and time of immersion) have been examined and the modification was confirmed by the determination of the exchange capacities, the distribution coefficient (P) and the selectivity factors (S). The obtained results revealed the effect of PEI on the exchange properties of the resin. The pH range selected (6-8) permitted a good adherence of PEI onto the resin surface. The quantity of the adsorbed PEI was increased by raising the initial concentration and the immersion period. The exchange capacity for copper ion passed from 2.6 mmol g(-1), in the case of unmodified resin, to 3.9 mmol g(-1) for the modified one.

Modification of cation-exchange membrane properties by electro-adsorption of polyethyleneimine

Abstract A cation-exchange membrane has been modified by fixation of polyethyleneimine on its surface. This fixation was carried out under an electric field effect, thus it is called electro-adsorption. The polycation formed in an acidic medium migrated toward the membrane and a charged layer was deposited on the surface, and the selectivity towards divalent ions decreased, yielding to the increase of the proton transfer. When the amount of adsorbed PEI increased, the electrical resistance ofthe membrane increased and the transport number of zinc decreased. However, suitable conditions like pH, current density and electro-adsorption time were controlled in the order to obtain membranes with better selectivity and low electrical resistance.

Removal of Ag(l), Cu(II) and Zn(ll) ions with a supported liquid membrane containing cryptands as carriers

Abstract The interface behaviour in the facilitated co-transport of Ag(I), Cu(II) and Zn(II) ions through supported liquid membranes (SLMs) made of a flat-sheet polypropylene membrane support containing cryptands (2.2.2 or 2.2.1) as carriers was studied. The liquid-liquid extraction tests showed a maximum distribution coefficient when the carrier concentration was greaterthan 10−4M. In transport experiments the transmembrane flux increased with increasing carrier concentration reaching a limiting value at greater than 10−3M concentration. The calculation ofthe diffusion coefficients in membranes showed ahigherdiffusivityof2.2.2-metal complexes with respect to 2.2.1-metal complexes for silver ions. A sequence of diffusivity D(Ag+)>D(Cu2+)>D(Zn2+) was obtained, but carrier 2.2.1 showed a higher selectivity through copper ions. A sequence of diffusivity D(Cu2+)>D(Zn2+)>D(Ag+) was obtained. The diffusivity was significantly higher when using Celgard 2500 support compared to Celgard 2400 or 2402. Variable metal ion concentrations in the feed phase fluxes almost zero, at less than 10−2 M concentration, were obtained. In the transient state of the transport through the SLM, different molar flow rates at the feed-membrane and membrane-strip interfaces were observed. The selectivity of the interfaces containing 2.2.2 in the separation binary mixtures of ions showed the following separation factors: SFAgZn = 2.50, SFAgCu = 1.64, SFcuZn = 1.42.

Donnan dialysis of copper, gold and silver cyanides with various anion exchange membranes☆

Donnan dialysis is an ion exchange membrane process that can be used for the purification and concentration of diluted solutions. In this work, the behaviour of gold, silver and copper in cyanide medium is examined. Flux of cyanide complexes and corresponding free cyanide are determined using five commercial anion exchanger membranes (AMV, ACS, RAI 5035, ADP and ADS). The results show that the rate transfer depends upon the nature of the anion exchanger membrane. It is observed that the species number in the feed solution influences the transfer selectivity of metal ion complex against free cyanide Thus, gold which forms only one stable species with cyanides is transferred faster through an ACS membrane than copper which forms three species. However, this result is not verified when an ADS membrane is used. A model of the complex transfer through anion exchange membranes based on Donnan dialysis is proposed. A three compartment Donnan dialysis is performed to improve the separation between the studied metals. Decyanidation is also examined and separation factors are calculated. It is shown that Donnan dialysis can be an efficient technique for the separation of cyanides complexes of copper, gold and silver when parameters such as anion exchange membrane and the number of compartments are optimised. An advantage of this technique is also the possibility of recycling all reactants with a good impact on the environment.

Modified membranes applied to metallic ion separation and mineral acid concentration by electrodialysis

Abstract Two modified membranes are used for the treatment of industrial effluent by electrodialysis. This surface modification of membrane using both immersion and electrodeposition method improves the selectivity for monovalent ions against to divalent. In this work both neutralisation of the effluent and acid enrichment are achieved. The immersion method appears more efficient when not morethan two compounds are inside the solution. On the other hand, electrodeposition technique should be used allowing to attain 2.8 N acid concentration. It was noticed that polyethyleneimine plays two different roles according to the modification method. The multilayer was formed by adsorption using immersion method though electrodeposition technique permits PEI to penetrate into the pores and play a role of an effective carrier for proton.

Facilitated co-transport of Ag(I), Cu(II), and Zn(II) ions by using a crown ether as carrier: influence of the SLM preparation method on ions flux

This article reports and discusses the study of facilitated co-transport of silver(I), copper(II), and zinc(II) ions through a supported liquid membrane (SLM) containing a specific extractant of metals: dibenzo-18-crown-6 (DB18C6) in chloroform as solvent. Mode and duration of immersion of the macroporous support in the organic phase, physical characteristics of the support (porosity, pore size, and thickness) as well as wettability of the SLM that influence the transport have been examined. Three preparation modes of the SLM (vacuum impregnation, impregnation by immersion in a high-vacuum chamber, simple impregnation by immersion (SI)) were compared and the best result was obtained with SI. In the last case, the obtained results showed that full impregnation of the support in the organic phase can take a long time (26 days) for obtaining high fluxes, if DB18C6 concentration is above 5×10−3 M because of the difficulty in impregnation due to carrier aggregation and precipitation. After 26 days, the support degrades under the action of the solvent. In fact, Fourier transformed-infrared spectroscopy showed support degradation while scanning electron microscopy observations showed that porosity and pore size were reduced with increasing impregnation time. On the other hand, at DB18C6 concentration below 5×10−3 M, impregnation took less time (30–60 min) because of the reduced ability of the carrier to form aggregates. Transport experiments showed an order of permeability, Ag(I)>Cu(II)>Zn(II). The Cu(II) flux, using 1 hr impregnation time, reached the highest value when the organic solution was made by dissolving 10−3 M DB18C6 in CHCl3. The flux for the above-mentioned ions increased with the increasing pore size and porosity of the polymeric support and decreasing thickness.

Removal of gold as Au(Tu)2+ complex with a supported liquid membrane containing macrocyclic polyethers ligands as carriers

Facilitated transport of gold(I) ions in acidic thiourea medium, across a Supported Liquid Membrane (SLM) by using dibenzo-18-crown-6 (DB18C6), diaza-18-crown-6 (DA18C6), hexathia-18-crown-6 (HT18C6) and hexaaza-18-crown-6 (HA18C6) as carriers, dissolved in chloroform, has been investigated. The fundamental parameters influencing the transport have been determined, they are: thiourea concentration in the feed phase, pH of the feed solution, carrier concentration in the membrane phase, gold concentration in the feed phase and type of acid. Thiourea can form, with gold ions, only one type of complex which is less mobile than the free metal cation. In fact, the mass transport flux of gold ions decreases when thiourea is added to the feed solution. However, when thiourea concentration increases, mass flux remain constant. Transport fluxes of gold ions from feed solutions of different anionic composition followed the order: NO 3 - >Cl - >SO 4 2- >PO 4 3- . This means that preferentially nitric acid should be used in preparing leaching solutions of polymetallic ores that are then used as feed in the SLM system.

Modified cation exchange resin applied to demineralisation of a liquid industrial waste. Comparison to a classical treatment and electrodialysis

Abstract An experimental study has been made on the separation and recovery of some metals from an effluent waste. Three methods (i.e. classical neutralisation, electrodialysis and ion exchange) were used and compared. Purification efficiency was determined in all cases of treatment. It was found that classical treatment causes formation of a large amount of sludge constituted principally of Al(OH) 3 , Fe(OH) 3 and CaSO 4 . Ten grams of solid were formed using 1 L of effluent treated. The electrodialysis process was efficient for removal of monovalent anions such as Cl − and NO 3 − from effluent using a monovalent selective anion exchange membrane. Increase of current density causes an increase of efficiency. Finally, a cation exchange resin modified by adsorption of tetrabutylammonium or polyethyleneimine on its surface was used and compared to unmodified resin and the two methods of treatment cited above. Modification of the resin surface allowed separation of species according to their valencies and hydration. Cations with high valencies were fixed on the resin modified by tetrabutylammonium, while transition metals were retained by chelate bonding with polyethyleneimine fixed on resin modified by this polyelectrolyte.

Effect of thiourea on the facilitated transport of silver and copper using a crown ether as carrier

Abstract Facilitated co-transport of both silver and copper ions in acidic-thiourea medium has been studied. Thiourea can form successive complexes, which are less mobile than the free metal cation. In fact, the mass-transport fluxes of both silver and copper ions decrease when the concentration of thiourea in the feed phase increases. The results obtained have been confirmed by the partition of the different species in the feed aqueous phase versus the concentration of thiourea by means of a conditional calculation which showed that Ag+ and Cu2+ species predominate at very low thiourea concentration (10−5–10−4 M) and are substituted by complexes M Tu n + (M=Ag, Cu with n=1–4) with increasing Tu concentration. The fundamental parameters influencing the transport of silver and copper ions have also been determined: Thiourea concentration in the feed phase, pH of the feed-solution, silver and copper concentration in the feed phase, crown-ether concentration in the membrane phase and the membrane support characteristics. It was possible to take advantage of the different chemical characteristics of Ag+ and Cu2+ in presence of thiourea. Working in the right conditions the selectivity of the transport (JAg+/JCu2+) increased from 1.6 to 5.5 with increasing Tu concentration from zero to 10−1 M.

Cadmium (II) and lead (II) transport in a polymer inclusion membrane using tributyl phosphate as mobile carrier and CuFeO2 as a polarized photo electrode

In this work, a development of polymeric inclusion membranes for the cations separation is reported. The membrane was made up of cellulose triacetate (CTA) with a tributyl phosphate (TBP) incorporated into the polymer as metal ions carrier. The transport of lead (II) and cadmium (II) ions in two membrane systems polymer inclusion membrane (PIM), PIM coupled with photo-chemical electrode using TBP as carrier and 2-nitro phenyl octyl ether (NPOE) or tris ethylhexyl phosphate (TEHP) as plasticizer have been investigated. The membranes: polymer+plasticizer+carrier were synthesized and characterized by FTIR, X-ray diffraction and scanning electron microscopy (SEM). Transports of lead and cadmium have been studied using these systems and the results were compared to commercial cation exchange membrane (CRA). The obtained results showed that for Pb(2+) ion, the concentrations of the strip phase increases using synthesized membranes. The conduction band of the delafossite CuFeO(2) (-1.25 V(SCE)) yields a thermodynamically M(2+) (=Pb(2+), Cd(2+)) photo electrodeposition and speeds up the diffusion process. In all the cases, the potential of the electrode M/M(2+) in the feed compartment increases until a maximum value, reached at approximately 100 min above which it undergoes a diminution.