Structural effects on metal ion migration across polymer inclusion membranes: Dependence of transport profiles on nature of active plasticizer

Removal of Methylene Blue Dye from Aqueous Solutions Using Polymer Inclusion Membrane Containing Calix[4]pyrrole

The effective purification of aqueous solutions of methylene blue dye was tested using polymer inclusion membranes (PIMs) that contained cellulose triacetate (CTA) as a polymer base, o-nitrophenyl octyl ether (o-NPOE) as a plasticizer, and meso-tetra methyl tetrakis-[methyl-2-(4-acetlphenoxy)] calix[4]pyrrole (KP) as a carrier. Scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy were used to define the microstructure and surface of PIMs. Experimental results showed that, with an increased concentration of methylene blue in an aqueous solution, the removal percentage also increased. Further observation showed that the flux increased with the rise in the source phase pH values from 3 to 10. The carrier and plasticizer content in the membrane significantly influenced the membrane's transport properties. The optimal composition of the membrane in percent by weight for KP was 74% plasticizer; 18% support, and 8% carrier. The maximum MB removal (93.10%) was achieved at 0.10 M HCl solution as the receiving phase. It was shown that the membrane with optimal composition showed good reusability and enabled the easy and spontaneous separation of methylene blue from aqueous solutions.

A Comprehensive Study on the Effect of Plasticizers on the Characteristics of Polymer Inclusion Membranes (PIMs): Exploring Butyl Stearate as a Promising Alternative

This study investigated the influence of various plasticizers commonly used in the manufacture of polymer inclusion membranes (PIMs), such as 2-nitrophenyl octyl ether (NPOE), phthalates, adipates, and sebacates on the mechanical, thermal, and transport properties of membranes. Additionally, butyl stearate (BTS), chosen for its non-toxic nature compared to phthalates and its cost-effectiveness relative to adipates and sebacates, was evaluated as a plasticizer in PIMs for the first time. All plasticizers were incorporated in PIMs made of either cellulose triacetate (CTA) or poly(vinyl chloride) (PVC) as the base polymers and the task-specific ionic liquid trioctylmethylammonium thiosalicylate (TOMATS) as the carrier. The plasticizers were found to significantly affect the characteristics of membrane hydrophilicity, mechanical flexibility, and thermal stability. Transport experiments using Hg(II) as a model target ion revealed that, for CTA-based PIMs, the plasticizer did not significantly affect transport efficiency. However, for PVC-based PIMs, BTS exhibited better efficiency when compared to NPOE. These findings highlight the potential of BTS as an attractive alternative to currently used plasticizers in PVC-based PIM formulations.

Modified LIX®84I-Based Polymer Inclusion Membranes for Facilitating the Transport Flux of Cu(II) and Variations of Their Physical-Chemical Characteristics

A unique facilitation on the transport flux of Cu(II) was investigated by using modified polymer inclusion membranes (PIMs). LIX^®84I-based polymer inclusion membranes (LIX^®-based PIMs) using poly(vinyl chloride) (PVC) as support, 2-nitrophenyl octyl ether (NPOE) as plasticizer and Lix84I as carrier were modified by reagents with different polar groups. The modified LIX^®-based PIMs showed an increasing transport flux of Cu(II) with the help of ethanol or Versatic acid 10 modifiers. The metal fluxes with the modified LIX^®-based PIMs were observed varying with the amount of modifiers, and the transmission time was cut by half for the modified LIX^®-based PIM cast with Versatic acid 10. The physical-chemical characteristics of the prepared blank PIMs with different Versatic acid 10 were further characterized by using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), contract angle measurements and electro-chemical impedance spectroscopy (EIS). The characterization results indicated that the modified LIX^®-based PIMs cast with Versatic acid 10 appeared to be more hydrophilic with increasing membrane dielectric constant and electrical conductivity that allowed better accessibility of Cu(II) across PIMs. Hence, it was deduced that hydrophilic modification might be a potential method to improve the transport flux of the PIM system.

Polymer inclusion membrane applications for transport of metal ions: A critical review

The co-existence of heavy metals in industrial effluents is a prevalent problem. Heavy metals are not biodegradable and can remain in the environment when left untreated. Therefore, metals must be removed from wastewater to protect people's health and the environment. Also, these pollutants usually have dissimilar compositions and properties. Generally, metal treatment is performed using traditional methods, but new processes have been developed due to the disadvantages of traditional methods. Especially in the last 20 years, studies on polymer inclusion membranes have been carried out and the transport performance of metal ions has been investigated. It is a more convenient process than both ion exchange and liquid-liquid extraction methods due to the potential and performance of polymer inclusion membranes. When the studies in the literature are examined, it is seen that the performance of polymer inclusion membranes is higher than expected and also when the production conditions are examined, polymer inclusion membrane is more advantageous than other processes. This review is a summary of the studies on the removal and transport of metal by using polymer inclusion membranes in the literature over the last 20 years.

Structural Characterization of the Plasticizers' Role in Polymer Inclusion Membranes Used for Indium (III) Transport Containing IONQUEST® 801 as Carrier

Polymer inclusion membranes containing cellulose triacetate as support, Ionquest^® 801 ((2–ethylhexyl acid) -mono (2–ethylhexyl) phosphonic ester) as extractant, and 2NPOE (o–nitrophenyl octyl ether) or TBEP (tri (2–butoxyethyl phosphate)) as plasticizers were characterized using several instrumental techniques (Fourier Transform Infrared Spectroscopy (FT–IR), Reflection Infrared Mapping Microscopy (RIMM), Electrochemical Impedance Spectroscopy (EIS), Differential Scanning Calorimetry (DSC)) with the aim of determining physical and chemical parameters (structure, electric resistance, dielectric constant, thickness, components’ distributions, glass transition temperature, stability) that allow a better comprehension of the role that the plasticizer plays in PIMs designed for In(III) transport. In comparison to TBEP, 2NPOE presents less dispersion and affinity in the PIMs, a plasticizer effect at higher content, higher membrane resistance and less permittivity, and a pronounced drop in the glass transition temperature. However, the increase in permittivity with In (III) sorption is more noticeable and, in general, PIMs with 2NPOE present higher permeability values. These facts indicate that In (III) transport is favored in membranes with chemical environment of high polarity and efficiently plasticized. A drawback is the decrease in stability because of the minor affinity among the components in 2NPOE–PIMs.

A Polymer Blend Electrolyte Based on CS with Enhanced Ion Transport and Electrochemical Properties for Electrical Double Layer Capacitor Applications

The fabrication of energy storage EDLC in this work is achieved with the implementation of a conducting chitosan–methylcellulose–NH₄NO₃–glycerol polymer electrolyte system. The simple solution cast method has been used to prepare the electrolyte. The impedance of the samples was fitted with equivalent circuits to design the circuit diagram. The parameters associated with ion transport are well studied at various plasticizer concentrations. The FTIR investigation has been done on the films to detect the interaction that occurs among plasticizer and polymer electrolyte. To get more insights into ion transport parameters, the FTIR was deconvoluted. The transport properties achieved from both impedance and FTIR are discussed in detail. It was discovered that the transport parameter findings are in good agreement with both impedance and FTIR studies. A sample with high transport properties was characterized for ion dominancy and stability through the TNM and LSV investigations. The dominancy of ions in the electrolyte verified as the t_ion of the electrolyte is established to be 0.933 whereas it is potentially stable up to 1.87 V. The rechargeability of the EDLC is steady up to 500 cycles. The internal resistance, energy density, and power density of the EDLC at the 1st cycle are 53 ohms, 6.97 Wh/kg, and 1941 W/kg, respectively.

Selective Transport of Ag(I) through a Polymer Inclusion Membrane Containing a Calix[4]pyrrole Derivative from Nitrate Aqueous Solutions

Cellulose-triacetate-based polymer inclusion membranes (PIMs) with different concentrations of a calixpyrrole ester derivative as the membrane carrier were studied to determine their ability to transport Ag(I) from aqueous nitrate solutions. The effects of the concentrations of ion carriers and metal ions, the pH of the source aqueous phase, and stripping agents on the effective transport of Ag(I) were assessed. All studied parameters were found to be important factors for the transport of Ag(I) metal ions. The initial fluxes were determined at different temperatures. The prepared membranes were found to be highly permeable. The selectivity of silver transport from an aqueous solution containing Ag(I), Cu(II), Pb(II), Cd(II), Ni(II), Zn(II), and Co(II) ions was also investigated.

Design and optimization of a single-use optical sensor based on a polymer inclusion membrane for zinc determination in drinks, food supplement and foot health care products

A single-use optical sensor was designed for Zn(II) determination based on the immobilisation of the colorimetric reagent 2-acetylpyridine benzoylhydrazone (2-APBH) in a polymer inclusion membrane (PIM) adhered on the surface of an inert rectangular strip of polyester (Mylar). Different components for the membrane preparation were tested and those resulting in membrane with good appearance, proper physical and optical properties and ease of preparation were selected. Factorial design 23 with three replicates of the central point was applied for the optimisation of the membrane composition. The optimal composition consisted of 2.5 g of poly(vinyl chloride) (PVC), 4 mL of tributyl phosphate (TBP) and 0.04 g of 2-APBH. The optode showed a linear dynamic range from 0.03 (detection limit) to 1 mg L-1 of Zn(II) ions with a response time of 30 min in aqueous solution at pH 6 and a relative standard deviation of 3.90% for 0.4 mg L-1 of Zn(II). The sensor exhibited good selectivity to Zn(II) over other commonly ions. It was successfully applied to the determination of Zn(II) in a water certified reference material, spiked tap water, vitamin-mineral drink, food supplement and foot health care products, as contribution to the concern about this heavy metal due to its significant role in many biological and physiological processes although toxicant at high doses.

Study on stable mass transfer and enrichment of phenol by 1-octanol/kerosene/polyvinyl chloride polymer inclusion membrane

A polymer inclusion membrane (PIM) that contains a polyvinyl chloride (PVC) polymer matrix and 1-octanol (OCT) as specific carrier (PO-PIM) was prepared to investigate the mass transfer behaviour of phenol in aqueous solutions. Results showed that the mass transfer behaviour of the PO-PIM for phenol conformed to the first-order kinetics. In addition, the mass transfer efficiency for phenol reached the maximum when the OCT content was 82.8 wt%. The mass transfer activation energy (E_a) was 14.46 kJ mol^-1, which indicated that intramembranous diffusion was the main controlling factor in the mass transfer process. The introduction of hydrophobic additives, such as kerosene, liquid paraffin and vegetable oil, into the PO-PIM could remarkably improve its stability. In an aqueous solutions of phenol ranging from 0 mg L^-1 to 9000 mg L^-1, the initial flux (J₀) of kerosene/PVC/OCT-PIM (KPO-PIM) was positively correlated with the initial concentration of phenol. For a stripping solution with a feed solution pH of 2.0 and a sodium hydroxide concentration of 0.1 mol L^-1, the maximum permeability coefficient during stable mass transfer reached 12.55 μm s^-1. At a mass transfer area of 3.14 cm², an enrichment factor (EF) of 3.5 for 200 mg L^-1 of phenolic aqueous solution was achieved within 48 h through KPO-PIM.

Liquid-liquid extraction and facilitated transport of f-elements using an N-pivot tripodal ligand

Diglycolamide (DGA)-functionalized tripodal ligands offer the required nine-coordinated complex for effective binding to a trivalent lanthanide/actinide ion. A N-pivot tripodal ligand (TREN-DGA) containing three DGA pendant arms was evaluated for the extraction and supported liquid membrane transport studies using PTFE flat sheets. Solvent extraction studies indicated preferential extraction of 1:1 (M:L) species, while the metal ion extraction increased with increasing HNO₃ concentration conforming to a solvated species extraction. Flat sheet-supported liquid membrane studies, carried out using 4.0 × 10^-3 M TREN-DGA in 95% n-dodecane + 5% iso-decanol indicated faster mass transport for Eu³⁺ ion as compared to Am³⁺ ion. The determined transport parameters indicated slow diffusion of the M-TREN-DGA (M = Am or Eu) complex being the rate-determining step. The transport of lanthanides and actinides followed the trend: Eu³⁺ > Am^3+∼ Pu⁴⁺ >> UO₂²⁺ and Am can be selectively separated from a mixture of U and Pu by oxidizing the latter to its +6 oxidation state. The liquid membrane stability was not encouraging and was deteriorating the transport efficiency with time, which was attributed to carrier loss into the aqueous phases.

Application of polymer-based membranes containing ionic liquids in membrane separation processes: a critical review

The interest in ionic liquids, particularly in polymerizable ionic liquids, is motivated by their unique properties, such as good thermal stability, negligible vapor pressure, and wide electrochemical window. Due to these features ionic liquids were proposed to be used in the membrane separation technology. The utilization of conventional ionic liquids is, however, limited by their release from the membrane during the given separation process. Therefore, the incorporation of polymerizable ionic liquids may overcome this drawback for the industrial application. This work is a comprehensive overview of the advances of ionic liquid membranes for the separation of various compounds, i.e. gases, organic compounds, and metal ions.

Simultaneous AuIII Extraction and In Situ Formation of Polymeric Membrane-Supported Au Nanoparticles: A Sustainable Process with Application in Catalysis

A polymeric membrane-supported catalyst with immobilized gold nanoparticles (AuNPs) was prepared through the extraction and in situ reduction of Au^III salts in a one-step strategy. Polymeric inclusion membranes (PIMs) and polymeric nanoporous membranes (PNMs) were tested as different membrane-support systems. Transport experiments indicated that PIMs composed of cellulose triacetate, 2-nitrophenyloctyl ether, and an aliphatic tertiary amine (Adogen 364 or Alamine 336) were the most efficient supports for Au^III extraction. The simultaneous extraction and reduction processes were proven to be the result of a synergic phenomenon in which all the membrane components were involved. Scanning electron microscopy characterization of cross-sectional samples suggested a distribution of AuNPs throughout the membrane. Transmission electron microscopy characterization of the AuNPs indicated average particle sizes of 36.7 and 2.9 nm for the PIMs and PNMs, respectively. AuNPs supported on PIMs allowed for >95.4 % reduction of a 0.05 mmol L^-1 4-nitrophenol aqueous solution with 10 mmol L^-1 NaBH₄ solution within 25 min.

Studies on the selective Am3+ transport, irradiation stability and surface morphology of polymer inclusion membranes containing Cyanex-301 as carrier extractant

Transport behaviour of Am(3+) across cellulose triacetate (CTA) based polymer inclusion membranes (PIM) containing Cyanex-301 (bis(2,4,4-trimethylpentyl)dithiophosphinic acid) as the carrier extractant and tri-n-butyl phosphate (TBP) or 2-nitrophenyloctylether (NPOE) as the plasticizer was investigated from different feed and strip conditions. The TBP plasticized membrane resulted back transport of Am when alpha-hydroxy iso-butyric acid was used as the complexing agent in the strip phase while no such effect was seen when ethylene diamine tetraacetic acid (EDTA) was used as the complexant. Effect of varying Cyanex-301 concentration and bipyridyl (bipy) concentration on Am transport was also investigated. Long term reusability of the membrane was studied by measuring the permeability coefficient (P) after exposing the PIMs to a maximum gamma ray dose of ∼ 200 kGy. The surface morphology of the membranes was analyzed by atomic force microscopy and the roughness parameter was correlated to transport efficiency.

Electrochemical impedance spectroscopy-a simple method for the characterization of polymer inclusion membranes containing aliquat 336

Electrochemical impedance spectroscopy (EIS) has been used to estimate the non-frequency dependent (static) dielectric constants of base polymers such as poly(vinyl chloride) (PVC), cellulose triacetate (CTA) and polystyrene (PS). Polymer inclusion membranes (PIMs) containing different amounts of PVC or CTA, along with the room temperature ionic liquid Aliquat 336 and plasticizers such as trisbutoxyethyl phosphate (TBEP), dioctyl sebecate (DOS) and 2-nitrophenyloctyl ether (NPOE) have been investigated. In this study, the complex and abstract method of EIS has been applied in a simple and easy to use way, so as to make the method accessible to membrane scientists and engineers who may not possess the detailed knowledge of electrochemistry and interfacial science needed for a rigorous interpretation of EIS results. The EIS data reported herein are internally consistent with a percolation threshold in the dielectric constant at high concentrations of Aliquat 336, which illustrates the suitability of the EIS technique since membrane percolation with ion exchangers is a well-known phenomenon.