Polymer Inclusion Membrane Composition Research Articles

Poly(vinyl chloride)-based advanced polymer inclusion membranes with Aliquat 336 and inorganic filler for efficient Cr(VI) removal

Poly(vinyl chloride) (PVC) hybrid polymer inclusion membranes (PIMs) with an ion carrier (Aliquat 336) and containing an inorganic filler (Cloisite (CNa) or mica) are successfully elaborated. The filler nature and its content in the PIM composition are optimized in terms of the PIM stability and reuse. It is found that the filler presence in the PVC matrix provokes a more irregular surface and an internal structure with apparent microvoids. Tensile tests reveal two different mechanical behaviors according to the filler type – a drop in Young’s modulus (up to ∼ 51 MPa) observed for membranes containing mica, thus resulting in more flexible membranes; on the contrary, membranes with decreased flexibility are obtained in the CNa presence. The higher Cr(VI) permeability of mica-based PIMs (∼9 µmol/(m2·s)) is attributed to their porous structure and high flexibility. During 5 cycles of Cr(VI) permeation measurements, membrane based on mica and Aliquat 336 preserves its stability, while the transport performance of both unfilled membrane and PIM with CNa is deteriorated. It is also noted that the carrier percolation threshold strongly affects the membrane stability – the lower is the percolation threshold, the higher is the membrane reusability, which is explained by the high stability of mica-based PIMs. This result testifies to the possibility of using hybrid PIMs loaded with mica and containing Aliquat 336 for metal ions separation.

PVC/EVA-based polymer inclusion membranes with improved stability and Cr(VI) extraction capacity: Water plasticization effect

Polymer inclusion membranes (PIMs) are far investigated for their ability to extract heavy metals and small organic compounds from aqueous media. Polyvinyl chloride (PVC) is one of the most widely used base polymers for the PIM elaboration. However, its use requires the incorporation of a relatively expensive liquid plasticizer. In the present work, poly(ethylene-co-vinyl acetate) (EVA) serves as a polymer plasticizer for the elaboration of PIMs based on PVC as a base polymer and Aliquat 336 as a carrier. The composition of PIMs was optimized in terms of the PVC/EVA ratio and the vinyl acetate (VA) groups content (x) of EVA (i.e. EVAx). Physical-chemical properties of the resulting membranes are analyzed and correlated with their structure. The results of SEM analysis revealed miscible PVC/EVA70 blends (i.e. with 70 wt% of VA groups) and partially miscible PVC/EVA40 blends. The plasticizing effect of the EVA copolymer was confirmed by the tensile test results. The results of transport measurements showed that PIMs containing EVA40 and PVC are more efficient for the Cr(VI) extraction than those with only PVC. Thus, EVA40 can effectively replace the conventional liquid plasticizers while improving the Cr(VI) permeability. Besides, it is stated that EVA40-based PIMs are more stable as compared with conventional PIMs due to the water plasticizing effect. After the membrane optimization, the highest Cr(VI) transport flux (54.7 µmol·m-2·s-1) was measured. Moreover, the addition of 10 wt% of tetradecanol causes the increase of the water plasticizing effect and allows obtaining a PIM with high stability (up to 24 cycles) required for the membrane long-term operation.

Selective extraction of Bi(III) from sulfate solutions by a poly(vinyl chloride) based polymer inclusion membrane incorporating bis(2-ethylhexyl)phosphoric acid as the extractant

The present paper reports on the first application of a polymer inclusion membrane (PIM) for the extraction of the bismuth(III) ion. Best results in terms of rate of Bi(III) extraction and amount extracted were achieved with a PIM composition of 50 wt% poly(vinyl chloride) as the base polymer and 50 wt% bis(2-ethylhexyl)phosphoric acid (D2EHPA) as the extractant and a feed solution adjusted to pH 1.3 and containing 0.2 mol L−1 sulfate. The back-extraction of Bi(III) was performed quantitatively in a 2 mol L−1 H2SO4 receiving solution. No deterioration in the PIM performance was observed in 15 consecutive extraction/back-extraction cycles and the membrane lost less than 4% of its mass when exposed to ambient air or a feed solution with the optimal composition mentioned above. The stoichiometry of the extracted Bi(III)-D2EHPA adduct was established to be BiL3(HL)3 where HL denotes D2EHPA. High selectivity for Bi(III) was achieved in the presence of common base metal ions such as Cu(II), Ni(II), Zn(II), Cd(II), Fe(III), Cr(III), Co(II), Mn(II), Al(III), and Mo(VI). The co-extraction of Fe(III) was suppressed by complexing it with fluoride. Fourier transform infrared spectroscopy, scanning electron microscopy, atomic force microscopy, contact angle measurements, thermogravimetric analysis, and stress-strain analysis were used for characterizing the PIM mentioned above.

Fabrication and Characterisation of Polyvinylidene Fluoride Co-Hexafluoropropylene Polymer Inclusion Membranes for Reactive Orange 16 Dye Removal

By implementing green technology, polymer inclusion membranes (PIMs) were used as an extractant for the removal of Reactive Orange 16 (RO16) dye as it is an easy and effective way. The extraction process is used because it is found to be more economical and effective compared to other dye removal methods. The PIMs consists of Polyvinylidene Fluoride Co-HFP (PVDF-Co-HFP) as a base polymer, Aliquat 336 as a carrier; dissolved in tetrahydrofuran (THF). The formulation of the components was varied to determine the optimum composition of PIMs with the effective extraction ability. The PIMs was characterised by Fourier Transform Infrared spectroscopy (FTIR), ion exchange capacity (IEC), water uptake, contact angle and Universal Testing Machine (UTM) methods to determine the physical, mechanical and chemical properties of the PIMs. Various parameters such as effect of carrier, initial dye concentration and pH were investigated. The optimum extraction of RO16 dye at 99.62% were obtained at PIMs were 9 % of carrier,10 mg/L initial dye concentration, pH 2 and agitation speed of 500 rpm at room temperature for 4 hrs. This proven that the fabricated PIMs has potential in removing dye.

Integration of Response Surface Methodology (RSM) and Principal Component Analysis (PCA) as an Optimization Tool for Polymer Inclusion Membrane Based-Optodes Designed for Hg(II), Cd(II), and Pb(II).

An optimization of the composition of polymer inclusion membrane (PIM)-based optodes, and their exposure times to metal ion solutions (Hg(II), Cd(II), and Pb(II)) was performed using two different chromophores, diphenylthiocarbazone (dithizone) and 1-(2-pyridylazo)-2-naphthol (PAN). Four factors were evaluated (chromophore (0.06–1 mg), cellulose triacetate (25–100 mg) and plasticizer amounts (25–100 mg), and exposure time (20–80 min)). Derringer’s desirability functions values were employed as response variables to perform the optimization obtained from the results of three different processes of spectral data treatment: two full-spectrum methods (M1 and M3) and one band-based method (M2). The three different methods were compared using a heatmap of the coefficients and dendrograms of the Principal Component Analysis (PCA)reductions of their desirability functions. The final recommended M3 processing method, i.e., using the scores values of the first two principal components in PCA after subtraction of the normalized spectra of the membranes before and after complexation, gave more discernable differences between the PIMs in the Design of Experiments (DoE), as the nodes among samples appeared at longer distances and varyingly distributed in the dendrogram analysis. The optimal values were time of 35–65 min, 0.53 mg–1.0 mg of chromophores, plasticizers 34.4–71.9 of chromophores, and 62.5–100 mg of CTA, depending on the metal ion. In addition, the method yielded the best outcomes in terms of interpretability and an easily discernable color change so that it is recommended as a novel optimization method for this kind of PIM optode.

Lithium extraction from synthetic brine with high Mg2+/Li+ ratio using the polymer inclusion membrane

Lithium extraction from brines with the high Mg2+/Li+ ratio is crucial for sustainable lithium resource and environmental protection. This study incorporated the classic tributylphosphate (TBP)/FeCl3 system into the polyvinyl chloride (PVC) based polymer inclusion membrane (PIM) to extract Li+ from the solution which is rich of Mg2+ (The initial Mg2+/Li+ molar ratio is 15). The morphology and composition of PIMs were characterized systematically, and the content of TBP/FeCl3 carrier in the PIM was optimized. Compared to liquid-liquid extraction, the extraction ratio of Li+ for PIM extraction increases by 20% and the separation factor of Li+ over Mg2+ increases by 5%. Besides, the loss ratio of Fe3+ after one loop of liquid-liquid extraction is 17.79%, which is close to that of PIM extraction after three loops (18.30%), demonstrating that the PIM showed a good stability. Furthermore, the separation factor of Li+ over Mg2+ for the PIM with 50 wt% TBP/FeCl3 is as high as 176 and the initial flux for Li+ is 8.12 × 10−4 mol m−2 h−1. This study displays a TBP/FeCl3 based PIM with high selectivity for Li+, providing a possible membrane technology for lithium extraction from brines.

Transport of Rhodium(III) from Chloride Media across a Polymer Inclusion Membrane Containing an Ionic Liquid Metal Ion Carrier.

Efficient and selective transport of rhodium(III) across a polymer inclusion membrane (PIM) from a 0.1 mol dm–3 HCl feed solution, also containing iron(III), to a receiving solution containing 0.1 mol dm–3 HCl and 4.9 mol dm–3 NH4Cl was achieved using a phosphonium-type ionic liquid, trioctyl(dodecyl)phosphonium chloride (P88812Cl), as the metal ion carrier. The optimum PIM composition for the Rh(III) transport was 50 wt % poly(vinylidene-co-hexafluoropropylene) (PVDF-HFP), 30 wt % P88812Cl, and 20 wt % plasticizer 2-nitrophenyl octyl ether (2NPOE). The driving force for the Rh(III) transport was suggested to be the concentration difference of the chloride ion between the feed and the receiving solutions. More than 70% rhodium(III) could be recovered from the receiving solution, and no transport of iron(III) was observed; however, the two metal ions cannot be separated by liquid–liquid extraction. This is the first report of selective transport of rhodium(III) across a polymer inclusion membrane.

Removal of picloram herbicide from an aqueous environment using polymer inclusion membranes

Abstract The picloram (4-amino-3,5,6-trichloro-2-pyridinecarboxylic acid) herbicide is widely applied to control the growth of woody plants and it has been frequently detected in aqueous environments due to its poor adsorption by soils and high leaching potential. Consequently, the removal of picloram from contaminated environmental waters is of major concern due to its adverse impacts on aquatic organisms, soils and animals. The development of a method for the extraction and transport of picloram from aqueous solutions using a polymer inclusion membrane (PIM) composed of cellulose triacetate, trioctylmethylammonium chloride (Aliquat 336) and 2–nitrophenyl octyl ether (NPOE) is reported. The experimental method was optimized for the PIM composition, and the type and concentration of stripping reagent. The optimized method demonstrated good performance indicators of flux and transport efficiency for picloram during non-competitive and competitive transport experiments. The PIM was also successfully applied in a passive sampling device to recover picloram at the maximum permissable concentration of 500 μg/L from a complex matrix of natural water. Findings from this study demonstrate that PIMs can serve as a potential alternative method for the removal and recovery of picloram and related herbicides from contaminated aqueous solutions.

Selective separation of uranium from sulfuric acid media using a polymer inclusion membrane containing alamine336

This study reports the extraction of U(VI) using poly(vinyl chloride)-based polymer inclusion membrane (PIM), possessing the extractant alamine336 and the plasticizer Polyoxyethylene alkyl ether (POE). The effects of transport parameters such as alamine336 and POE concentration in the PIM composition, uranium and sulfuric acid concentration in the feed phase, and the receiving phase type and concentration were discussed. Under the optimum conditions, 91.02 ± 2% of uranium was transported through the PIM. The prepared PIM showed excellent selectivity for U(VI) from the sulfuric acid leach solution. The stability of the PIM was found to be acceptable for 5 days.

Plasticization-induced oriented micro-channels within polymer inclusion membranes for facilitating Cu(II) transport

Although polymer inclusion membranes (PIMs) have been potentially used for facilitating the ion transport, the internal structure evolution of the PIMs is still controversial. This work focused on the effect of the composition and structure of PIMs on the transport of Cu(II), which were composed of poly(vinyl chloride) (PVC) as skeleton, 2-nitrophenyloctyl ether (NPOE) as the plasticizer, and commercial LIX84I as the carrier. The results suggested that the transport flux of Cu(II) is significantly dependent on the membranous composition. While correlating the membranous composition, the microstructural information of the PVC-based PIMs was explored and evaluated using X-ray diffraction (XRD), scanning electron microscopy (SEM), small-angle X-ray scattering (SAXS), and electrochemical impedance spectroscopy (EIS), respectively. XRD patterns and SAXS spectral features indicated that the significant structure transition occurred while increasing the NPOE content. Micro-channels of around 9 nm average diameter were clearly disclosed by SAXS for the PIM containing 40 wt% PVC, 30 wt% NOPE and 30 wt% LIX84I. And the well-organized pathway within in the PIMs was essential for efficient Cu(II) transport. The membrane's electrical parameters including dielectric constant and conductivity were also found to be depended on the membranous composition and structure. Besides, the selective transport of Cu(II) towards Ni(II) and Co(II) with PIM were further examined.

A novel approach in simultaneous extraction of basic dyes by using a batch reactor consisting a polymer inclusion membrane

A novel approach in simultaneous extraction of two basic dyes, malachite green (MG) and methylene blue (MB) from an aqueous solution was performed by using a batch reactor consisting a polymer inclusion membrane (PIM). The PIM is made up of poly(vinyl) chloride (PVC) as the base polymer, bis-(2-ethylhexyl) phosphate (B2EHP) as an extractant and dioctyl phthalate (DOP) as the plasticizer. The optimized extraction conditions for both dyes were identified by varying the composition of the PIM. It was found that the optimum PIM composition for simultaneous extraction was PIM with a composition of PVC 35% wt% (m/m): B2EHP 60% wt% (m/m): DOP 5% wt% (m/m). It shows that the average percent extraction efficiency achieved is more than 97% for the mixture of MG and MB (100 mg L−1) within 4 h of extraction process. The batch reactor consisting PIM prepared in this study is highly capable in performing simultaneous extraction of MG and MB in an aqueous solution.

Polymer inclusion membranes based on CTA/PBAT blend containing Aliquat 336 as extractant for removal of Cr(VI): Efficiency, stability and selectivity

Cellulose triacetate (CTA) and poly(butylene adipate-co-terephthalate) (PBAT)-based polymer inclusion membranes (PIMs) containing ionic liquid (tricaprylmethylammonium chloride (Aliquat 336)) as the carrier extractant were obtained for the facilitated and selective transport of Cr(VI) ions. The composition of PIMs was optimized in terms of the CTA/PBAT ratio. The obtained membranes were investigated using different techniques in order to show the influence of the membrane composition and the ionic liquid presence on the PIM resulting properties. The infrared analysis confirmed the presence of the intermolecular interactions of the hydroxyl groups of CTA with the carboxyl groups of PBAT and of the negatively charged carboxyl groups of CTA with the positively charged ammonium groups of Aliquat 336. The water contact angle measurements highlighted that the Aliquat 336 and PBAT presence modified the membrane hydrophobic/hydrophilic character. Moreover, it was shown that PIM containing the equivalent content of CTA and PBAT (35/35 wt%/wt%) with 30 wt% of Aliquat 336 revealed the optimized composition and was used for the Cr(VI) ions transport measurements. It was found that this PIM transported >99% of Cr(VI) in only 6 h and accumulated <5% of Cr(VI) ions with a high initial flux. For the first time it is shown that the selective Cr(VI) transport through blend PIM with reduced extractant content and without plasticizer is more efficient compared to common PIMs. Besides, the stability of obtained blend PIMs was confirmed by carrying out continuous transport studies over a long period of time (>120 h).

A poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)-based polymer inclusion membrane (PIM) containing LIX84I for the extraction and transport of Cu(II) from its ammonium sulfate/ammonia solutions

A comparison is made of the use of polymer inclusion membranes (PIMs) containing poly(vinyl chloride) (PVC), cellulose triacetate (CTA) or poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) as the base-polymer, LIX84I as the carrier and 2-nitrophenyloctyl ether (NPOE) as the plasticizer for the extraction of Cu(II) from its ammonium sulfate/ammonia solutions at pH 8.5 and its transport within the membrane. The optimal PIM composition for each base-polymer was determined, and the results showed that the PIMs containing CTA or PVC had an oily surface after extraction unlike the PIMs with PVDF-HFP which were homogenous and with oil-free surfaces. This oily residue indicated the loss of organic phase into the aqueous phase, as confirmed by Fourier transform infrared spectroscopy. Successive transport experiments were employed to study the stability of the PVDF-HFP-based PIM by evaluating the transport efficiency and the membrane mass change during each experiment. Relatively small membrane mass losses occurred during the extraction and back-extraction processes and the trace organic compounds lost from the PIM were identified using gas chromatography-mass spectrometry. The results obtained showed that the choice of base-polymer had a strong influence on the membrane stability, and that PVDF-HFP-based PIM exhibited superior stability and extraction rate compared to PIMs containing the other two base-polymers mentioned above.

Extraction of malachite green from wastewater by using polymer inclusion membrane

An extraction of a basic dye, Malachite Green (MG) from synthetic and real wastewaters solution was carried out by using polymer inclusion membrane (PIM). The PIM consists of poly(vinyl) chloride (PVC) as base polymer, bis-(2-ethylhexyl) phosphate (B2EHP) as extractant and dioctyl phthalate (DOP) as plasticizer. The composition of the components were varied to determine the optimum composition of the membrane with better extraction ability. After optimization the composition of PIM, the average extraction efficiency achieved was >98% for MG concentration of 20–80mgL−1. The PIM was characterized by Fourier Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA) and Scanning Electron Microscopy (SEM) methods PIM produced in this study is mechanical and chemically stable. Finally, the PIM was applied to remove MG in the wastewater samples. Results showed that average percent extraction achieved for MG were >98% and >96%, for both wastewater samples of 50 and 100mgL−1 respectively.

Polymer inclusion membrane containing a diglycolamide-functionalized calix[4]arene for actinide ion uptake and transport

Cellulose triacetate (CTA) -based polymer inclusion membranes (PIM) containing a diglycolamide-functionalized calix[4]arene (C4DGA) as the carrier extractant and 2-nitrophenyl octyl ether (NPOE) as the plasticizer were evaluated for the separation of actinides such as Am3+, Pu4+, UO22+, and Th4+ from dilute acidic feeds. The optimized PIM composition was found to be 6.5% C4DGA, 67.7% NPOE, and 25.8% CTA. The PIM of optimized composition was characterized physically by different techniques, viz., thermogravimetry, X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, and transmission infrared mapping microscopy (TIMM). The feeds in the batch uptake as well as transport studies involved solutions of the actinide tracer in the required oxidation state in 1M HNO3, while the receiver solutions used in the transport studies contained a 1M alpha-hydroxy-iso-butyric acid (AHIBA) solution at pH 3.0. The uptake efficiency followed the order: Am3+>Pu4+>Th4+≫UO22+, while the transport efficiency order was: Pu4+>Am3+>Th4+ with no detectable transport of the UO22+ ion. The effective diffusion coefficient (Deff) was determined from time-lag experiments, while the permeability coefficient (P) values were obtained from the transport studies and compared with those reported for TODGA (N,N,N′,N′-tetra-n-octyl diglycolamide) and T2EHDGA (N,N,N′,N′-tetra-2-ethylhexyl diglycolamide) containing PIMs. The reusability of the PIMs was assessed by successive uptake and stripping studies, while the stability of the PIMs was assessed by carrying out continuous transport studies over a period of time.

Polymer Inclusion Membranes Containing N,N,N′,N′-Tetra(2-ethylhexyl) Diglycolamide: Uptake Isotherm and Actinide Ion Transport Studies

Polymer inclusion membranes (PIMs) containing N,N,N′,N′-tetra(2-ethylhexyl) diglycolamide (T2EHDGA), a branched diglycolamide extractant as the carrier, cellulose triacetate (CTA) as the polymer matrix, and 2-nitrophenyloctyl ether (NPOE) as the plasticizer were evaluated for the recovery of actinide ions such as Am3+, Pu4+, UO22+, and Th4+ from acidic feed solutions. The optimized PIM composition used in this study was 69% T2EHDGA, 17% NPOE, and 14% CTA. Sorption isotherm experiments were carried out using macro concentrations of Eu carrier (100 mg/L) spiked with 152Eu tracer, and modeling of the data was performed. The sorption kinetics data fitted to the pseudo-second-order model and the Langmuir isotherm suggested a monolayer chemisorption mechanism. Transport studies were carried out in a two-compartment cell in which the feed solution was 1 M HNO3 spiked with the respective radiotracer while the receiver compartment contained 1 M α-hydroxy-iso-butyric acid (AHIBA) solution. Slow transport rate and l...

Comparative evaluation of actinide ion uptake by polymer inclusion membranes containing TODGA as the carrier extractant

Polymer inclusion membranes (PIM) containing TODGA (N,N,N′,N′-tetra-n-octyl diglycolamide) were evaluated for the separation of actinide ions such as Am3+, Pu4+, UO22+ and Th4+ from acidic feeds. The PIMs were prepared using cellulose triacetate (CTA) as the polymer matrix and 2-nitrophenyloctyl ether (NPOE) as the plasticizer along with the diglycolamide carrier extractants and were characterized by conventional techniques such as XRD, thermal analysis and AFM. The PIM composition was optimized by a series of studies which involved variation in the CTA, NPOE and carrier concentration which suggested 58% TODGA, 30% NPOE and 12% CTA to be optimum. The uptake studies were carried out using feed solutions containing varying concentrations of nitric acid and showed the trend: Am3+>Pu4+>Th4+>UO22+.Transport studies were carried out in a two-compartment cell where nitric acid concentration the feed was varied (1–3M) while the receiver compartment contained alpha-hydroxy-iso-butyric acid (AHIBA). The actinide ion transport efficiencies with TODGA containing PIMs followed the same trend as seen in the uptake studies. The AFM patterns of the PIMs changed when loaded with Eu3+ carrier (used as a surrogate for Am3+) while the regenerated membranes have displayed comparable morphologies. Diffusion coefficient values were experimentally obtained from the transport studies and were found to be 8.89×10−8cm2/s for Am3+ transport.

Phenol Removal Process Development from Synthetic Wastewater Solutions Using a Polymer Inclusion Membrane

This paper presents the results concerning the first use of a polymer inclusion membrane (PIM) for the removal and transport of phenol from an aqueous solution and polluted water. The PIM contains Cyanex 923 as the carrier, cellulose triacetate (CTA) as the base polymer, and o-nitrophenyl pentyl ether (ONPPE) as a plasticizer. The effects of variables on the transport percentage of phenol have been studied. These variables include the concentration of the carrier and the plasticizer in the membrane, pH of the aqueous phase, and the concentration of NaOH in the stripping phase. This study shows that PIM composition has a great influence in phenol recovery, while the pH of the feed phase is a determining factor for the transport of phenol. In optimal conditions (PIM: 1 cm3 ONPPE/g CTA, 0.5 M of Cyanex 923; feed phase: pH 2; stripping phase: NaOH 0.25 M), it is possible to transport 85% of phenol present in both the water lab feed phase and polluted water. Chemical oxygen demand (COD) shows that only 4.3% of organic compounds other than phenol are transported to the stripping phase, which indicates that the process is highly discriminative for phenol, even in extremely contaminated water.

Removal of chromium(VI) from aqueous solutions using a polyvinyl-chloride inclusion membrane: Experimental study and modelling

The present paper reports the use of a polymer inclusion membrane (PIM) prepared without addition of plasticizers as solid sorbent for the removal of Cr(VI) ions from aqueous solution simulating the real industrial effluents. The studied sorbent (PIM) contains 40% organic anion exchanger Aliquat 336 and a polymer matrix of 60% polyvinyl chloride (PVC). The influence of the Aliquat 336 content of the PIM, the contact time, the pH and the initial metal concentration in the aqueous solution on the Cr(VI) sorption process was analysed by using the batch extraction technique. The optimal PIM composition was found to be 40% Aliquat 336/60% PVC (w/w). This sorbent was further used for the kinetic, isotherm, desorption, reusability and selectivity studies. The sorption kinetics was well described by the pseudo-second order model (Ho), and the kinetic experiments confirm that the sorption process of Cr(VI) into the optimal non-plasticized PVC-based PIM is a chemisorption, which occurs through a “relay mechanism”. The adsorption isotherm was best fitted by the Sips equation, and the experimentally determined maximum sorption capacity of Cr(VI) into the 40% Aliquat 336/60% PVC PIM was found to be 0.978mmol/g (50.85mg/g). The retained metal ions can be desorbed by using 0.5M NaNO3, this desorption of metal ions occurring concomitantly with the PIM regeneration. The use of this less aggressive eluent permits the reuse of the same PIM for at least five consecutive sorption processes. Moreover, the optimal PIM possesses a high selectivity for Cr(VI) ions from mixtures with other metal ions and anions usually existing in the real industrial effluents.All these properties indicate that PIM with the composition 40% Aliquat 336/60% PVC has a potential to be used as solid sorbent for Cr(VI) ions. Another advantage is its lower price compared to the plasticized PIMs.

A method for the coating of a polymer inclusion membrane with a monolayer of silver nanoparticles

The preparation of silver nanoparticles (AgNPs) is described using a polymer inclusion membrane (PIM) consisting of 45% (m/m) di-(2-ethylhexyl)phosphoric acid (D2EHPA) and 55% (m/m) poly(vinyl chloride) (PVC) as a template. The Ag(I) ion was firstly extracted into the membrane via cation-exchange and then subsequently reduced with NaBH4, trisodium citrate, citric acid, or l-ascorbic acid to form AgNPs. The most effective reducing agent was found to be l-ascorbic acid which at pH 2.0 formed a uniform monolayer of AgNPs of an average size of 360nm on the surface of the PIM. Citric acid also produced AgNPs but these were embedded in the bulk of the membrane and did not provide a good surface coverage. NaBH4 and trisodium citrate, on the other hand, gave rise to the formation of black silver oxide on the membrane surface.Factors such as the membrane loading with Ag(I), PIM composition, reduction time, temperature and shaking time were found to have a significant influence on the surface coverage and size of the AgNPs.