T. Rhlalou’s research while affiliated with French National Centre for Scientific Research and other places

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Publications (6)


Mercury removal from wastewater using a poly(vinylalcohol)/poly(vinylimidazole) complexing membrane
  • Article

October 2010

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72 Reads

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65 Citations

Chemical Engineering Journal

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T. Rhlalou

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J.-F. Verchère

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L. Lebrun

Removal of Hg(II) ions from aqueous solutions by a novel complexing membrane was investigated by performing sorption and filtration experiments. The membrane, prepared by the technique of semi-interpenetrated polymer networks, consists in a matrix of poly(vinylalcohol), crosslinked by gaseous dibromoethane, that immobilizes chains of poly(vinylimidazole), a complexing polymer synthesised for this purpose. The morphology of the membrane was observed by scanning electron microscopy, showing an homogeneous structure, but surface unevenness. The dissolution of the membrane in water was slow and limited to 8% in 2 months, showing the efficiency of the crosslinking process. Efficient retention of Hg(II) was observed at pH 2.5. The kinetics of sorption were studied. The sorption equilibrium was satisfactorily represented by the Langmuir model. Isotherms performed at different temperatures allowed the calculation of the thermodynamical parameters. The sorption of mercury was endothermic, with a large positive entropy change that was ascribed to proton release. The effects of parameters such as water hardness, and the presence of complexing chloride anions were investigated, showing little influence on the retention ratio. Fast and efficient regeneration of the membrane was performed with a 0.5 M HNO3 solution. The maximum capacity of the membrane was 120 mg Hg g−1, whereas the theoretical exchange capacity was 853 mg Hg g−1, showing that most internal complexing sites of the membrane were not accessible to mercury ions in sorption experiments. When used in the filtration mode, the elimination ratio of Hg(II) was ≥99.4% for solutions containing 91.6 or 17.5 mg Hg L−1.


Novel Metal-Complexing Membrane Containing Poly(4-vinylpyridine) for Removal of Hg(II) from Aqueous Solution

July 2009

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40 Reads

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43 Citations

The Journal of Physical Chemistry B

A novel poly(vinyl alcohol)/poly(4-vinylpyridine) (PVA/P(4)VP) complexing membrane for removal of Hg(II) ions from aqueous solutions represents a significant improvement over a previously reported PVA/poly(ethylenimine) (PEI) membrane. This membrane was prepared by the semi-interpenetrating polymer network technique, and its cross-linking by three different agents was studied. The best results were obtained with gaseous 1,2-dibromoethane at 140 degrees C for 1 h that gave a membrane with a swelling ratio of 0.66. The sorption reaction of Hg(II) followed a first-order rate law, and the rate-limiting step was shown to be the association of Hg(II) ions with the complexing sites of P(4)VP. Sorption experiments at pH 2.5 showed that the retention ratio could reach 100% under optimized conditions for the initial concentration of Hg(II) and mass of membrane, c(0) = 100 mg L(-1) and m(D) = 100 mg, respectively. The retention ratio was remarkably insensitive to water hardness or the presence of NaCl, suggesting possible use for the purification of real wastewaters. The retention capacity of the membrane was 450 mg g(-1) compared to 311 mg g(-1) reported for the PVA/PEI membrane. Sorption isotherms were determined at various temperatures, according to the Langmuir model, for the determination of the thermodynamical parameters. When T increased, mercury uptake at equilibrium did not change, whereas the sorption coefficient b decreased and the change in free energy DeltaG degrees decreased. This result is probably due to a large favorable entropic effect, ascribed to the displacement of protons from the protonated sites of P(4)VP while they bind with Hg(II) ions. The membrane could be regenerated by 0.5 M nitric acid with less than 3% loss of efficiency. The membrane was used for filtration experiments. The elimination ratio was 99.9% or more for filtration of Hg(II) solutions in the c(0) = 16.6-89.1 mg L(-1) range.


Sorption and filtration of Hg(II) ions from aqueous solutions with a membrane containing poly(ethyleneimine) as a complexing polymer

December 2008

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36 Reads

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75 Citations

Journal of Membrane Science

The performances of a PVA/PEI complexing membrane for the removal of Hg(II) from aqueous solutions were investigated by performing sorption and filtration experiments. This membrane, that was previously shown to ensure efficient sorption of the heavy metal ions Pb(II), Cd(II) and Cu(II) at pH 5, presented a higher affinity for Hg(II) at pH 2.5. The sorption equilibrium was satisfactorily represented by the Langmuir model. In view of possible application to the treatment of industrial wastewaters, the effects of parameters such as pH, temperature, water hardness, and the presence of complexing chloride anions were investigated. The effect of increasing temperature was not straightforward: the complexation equilibrium constant decreased, but the mass of mercury sorbed increased, probably due to the higher mobility of the polymer chains that made internal sites available for complexing mercury. The maximum retention capacity of the membrane was 311 mg Hg g−1. Also, operating at large calcium or chloride concentrations was not detrimental to the membrane performances. For regeneration of the membrane, a 0.05 M solution of EDTA is recommended on the basis of limited performance loss. When used in the filtration mode, the elimination ratio of Hg(II) was close to 99%.


Removal of Heavy Metal Ions From Aqueous Solutions by Filtration With a Novel Complexing Membrane Containing Poly(Ethyleneimine) in a Poly(Vinyl Alcohol) Matrix

January 2008

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261 Reads

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312 Citations

Journal of Membrane Science

A novel complexing membrane was used for the removal of heavy metal ions such as Pb(II), Cd(II) and Cu(II) from aqueous solutions. The membrane consists in a semi-interpenetrating polymer network of crosslinked poly(vinyl alcohol) as the matrix and poly(ethyleneimine) as the complexing polymer. The absorption reactions followed pseudo-first-order kinetics with similar rate constants for the three cations. A model is proposed for the absorption–desorption process in order to rationalize the data obtained for the retention ratio and the retention efficiency ratio. The corresponding equilibrium constants were determined for the three metal ions, showing that the affinity order of the membrane is Pb > Cu > Cd. This sequence is consistent with the order of maximum uptake of the ions per gram of membrane: 0.59, 0.47 and 0.33 mmol g−1, respectively. On the other hand, the uptake order is different on a mass basis: 123, 30 and 37 mg g−1, respectively. Regeneration of the membrane and metal recovery were studied with HCl and HNO3 at different concentrations. Filtration of solutions of each metal ion showed large elimination ratios (96–99.5%) with a retention sequence Cd > Cu > Pb. The membrane remained efficient until complete saturation of its sites. Moreover, Cu retention is larger than expected, indicating possible additional chelation by the PVA matrix. Better retention ratios were observed when the concentration of the feed solution was kept constant. Filtration of a mixture of the three cations (all at 100 ppm concentration) resulted in the same retention sequence, but the elimination ratios were smaller and Pb was eventually displaced by Cu and Cd that were present in larger molar concentrations.


Facilitated transport of sugars by a resorcinarene through a supported liquid membrane

April 2000

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21 Reads

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51 Citations

Journal of Membrane Science

T Rhlalou

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M Ferhat

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M.A Frouji

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[...]

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J.-F Verchère

Supported liquid membranes (SLM) containing the resorcinarene carrier 1 have been used for the selective transport of monosaccharides (pentoses and hexoses) from concentrated aqueous solutions. The membranes, made of PTFE films of different porosities impregnated with a CCl4 solution of 1, are stable for at least 10 days. The permeabilities of the SLMs for various sugars were calculated. The results are compared with those of selective extraction of sugars performed with a CCl4 solution of 1. On the basis of the flux dependence on the initial concentrations of carrier and sugar, the rate-determining step in the transport mechanism is shown to be the migration of the 1 : 1 carrier–sugar complex in the immobilized organic phase.


Selectivity factors in the transport of carbohydrates through an organic solution of resorcinarene

January 1999

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6 Reads

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6 Citations

Carbohydrate Letters

Using a CCI4 solution saturated with water, alditols and sugars are extracted by forming host-guest complexes with resorcinarene 1. The selectivity is lower than in anhydrous conditions. However, carbohydrates that possess xylo or ribo configurations are extracted in higher yield than those with arabino or manno configurations.

Citations (6)


... Boronic acids were among the first agents used to selective extraction of some simple sugars [25][26][27]. Later, a derivative agent of calix [4]arene with a perfectly symmetrical structure, was used in organic phase CCl 4 for facilitated but not specific extraction of several alditols and sugars from aqueous solutions [28][29][30][31][32][33][34]. For more selectivity, we have recently suggested a commercial carrier agent, having unsymmetrical structure, and derived from a non-toxic natural compound (sterol) [35,36], especially the methyl cholate ester (Fig. 1). ...

Reference:

Membrane processes for the facilitated extraction of disaccharide sugars: Parameters and mechanism
Selectivity factors in the transport of carbohydrates through an organic solution of resorcinarene
  • Citing Article
  • January 1999

Carbohydrate Letters

... Although these techniques have negative noneconomic effects, it is said that liquid-based extraction (Nasu et al., 1997), Coprecipitation (Soylak & Erdogan, 2006), exchange of ions (Tao & Fang, 1998), adsorption, membrane filtration (Bessbousse et al., 2008), resin chelation (Atia et al., 2005), and electrochemical technologies are efficient at eliminating heavy metal ions from water bodies. On the other hand, improved enrichment factors, easy ease of use, protection with reference to noxious substances, great selectivity, decreased cost, quick recovery, and versatility to integrate it with many advanced detection strategies are only a few of the major advantages of solid-phase extraction (SPE) (Zhang et al., 2010). ...

Sorption and filtration of Hg(II) ions from aqueous solutions with a membrane containing poly(ethyleneimine) as a complexing polymer
  • Citing Article
  • December 2008

Journal of Membrane Science

... For instance, a novel complexing membrane containing poly(ethyleneimine) in a poly(vinyl alcohol) matrix exhibited remarkable removal efficiencies for heavy metals such as Cd²⁺ (96-99.5%), Cu²⁺ (94-99%), and Pb²⁺ (80-96%) 33 . However, these membranes reach saturation quickly, limiting their long-term effectiveness. ...

Removal of Heavy Metal Ions From Aqueous Solutions by Filtration With a Novel Complexing Membrane Containing Poly(Ethyleneimine) in a Poly(Vinyl Alcohol) Matrix
  • Citing Article
  • January 2008

Journal of Membrane Science

... In this context, the interpretation of data on the extraction process is useful to suggest systems more selective and more efficient. Rhlalou et al. (2000); Tbeur et al. (2000); and Hassoune et al. (2008) discussed the influence of structure and nature of complexes formed between the extractive agent and various carbohydrate compound on the liquid-liquid extraction process. Similarly, a number of studies (Munro and Smith 1997;White et al. 2001) which are available in this context have shown that the diffusion of organic compounds through the organic phase is carried out by the interaction of substrate-extractive agent according to reversible reactions (association/dissociation), which stabilities depend on the structure of the compounds and the nature of interaction sites. ...

Facilitated transport of sugars by a resorcinarene through a supported liquid membrane
  • Citing Article
  • April 2000

Journal of Membrane Science

... A pseudo-first order kinetic is commonly observed for metal ion sorption, e.g., by complexing membranes [38]. It has also been reported in biorefractory organics molecules or azo-dye removal in MFC [39,40]. ...

Mercury removal from wastewater using a poly(vinylalcohol)/poly(vinylimidazole) complexing membrane
  • Citing Article
  • October 2010

Chemical Engineering Journal

... Polymers with functional groups containing lone electron pairs, such as nitrogen, hydroxyl, or sulfur, can form coordination bonds with metal ions. Nitrogen-containing polymers, including polyamides, poly(ethylenimine) (PEI), and poly(vinylpyridine) (PVP), have been widely used for metal ion adsorption [19][20][21], catalyst resins [22][23][24], and biosensors [25,26]. The organic polymer component not only imparts structural support but also enhances the material's mechanical properties and processability. ...

Novel Metal-Complexing Membrane Containing Poly(4-vinylpyridine) for Removal of Hg(II) from Aqueous Solution
  • Citing Article
  • July 2009

The Journal of Physical Chemistry B