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

Process optimization and mechanism for the selective extraction of copper(ii) from polymetallic acidic solutions using a polymer inclusion membrane (PIM) with Mextral®5640H as the carrier

This study introduces a novel approach by integrating solvent extraction and polymer inclusion membrane (PIM) separation technologies to engineer an innovative PIM membrane material for the selective separation and enrichment of strategic metals, particularly copper, from polymetallic acidic solutions. The primary objectives were to streamline the technological process, reduce production costs, and enhance separation coefficients between copper and other metals. The optimal extraction conditions were determined as a mass fraction of Mextral®5640H : PVC : NPOE = 3 : 3 : 4, extraction temperature of 35 °C, and 0.9 mol L-1 H2SO4 in the stripping solution. Under these conditions, we achieved remarkable extraction efficiencies, with copper reaching 100%, and the separation coefficients between Cu2+ and Ni2+, Co2+, and Zn2+ exceeding 106. To elucidate the substantial differences in extraction performance between Cu2+ and the other metals (Ni2+, Co2+, and Zn2+), we employed an integrative analytical approach that combines FT-IR spectroscopy, BET analysis, and theoretical calculations. All extracted complexes demonstrated molecular sizes compatible with PIMs, underscoring the critical role of stability and back-extraction performance in the selective extraction of these metal ions.

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. EVA_x). 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.

Technical design and optimisation of polymer inclusion membranes (PIMs) for sample pre-treatment and passive sampling - A review

This review reports on the increasing interest in technical designs, calibration, and application of PIM-based devices in sample pre-treatment and passive sampling in environmental water monitoring from 2010 to 2021. With regards to passive sampling, devices are calibrated in a laboratory setup using either a dip-in or flow-through approach before environmental application. In sample preparation, the device set-ups can be offline, online or in a continuous flow separation device connected to a flow injection analysis system. The PIMs have also demonstrated potential in both these offline and online separations; however, there is still a draw-back of low diffusion coefficients obtained in these PIM set-ups. Electro-driven membrane (EME) extraction has demonstrated better performance as well as improved analyte flux. Critical in electro-driven membrane extraction is applying correct voltage that may not compromise the PIM performance due to leaching of components to the aqueous solutions. Further, besides different PIM configurations and designs being developed, PIM based extractions are central to PIM components (base polymer, carrier and plasticizer). As such, recent studies have also focused on improving PIM stability by investigating use of various PIM components, incorporating nano additives into the PIM composition, and investigating novel green PIM synthetic routes. All these aspects are covered in this review. Further, some recent studies that have demonstrated the ability to eliminate effects of flow patterns and membrane biofouling in PIM based applications are also included.

A Review on Promising Membrane Technology Approaches for Heavy Metal Removal from Water and Wastewater to Solve Water Crisis

Due to the impacts of water scarcity, the world is looking at all possible solutions for decreasing the over-exploitation of finite freshwater resources. Wastewater is one of the most reliable and accessible water supplies. As the population expands, so do industrial, agricultural, and household operations in order to meet man’s enormous demands. These operations generate huge amounts of wastewater, which may be recovered and used for a variety of reasons. Conventional wastewater treatment techniques have had some success in treating effluents for discharge throughout the years. However, advances in wastewater treatment techniques are required to make treated wastewater suitable for industrial, agricultural, and household use. Diverse techniques for removing heavy metal ions from various water and wastewater sources have been described. These treatments can be categorized as adsorption, membrane, chemical, or electric. Membrane technology has been developed as a popular alternative for recovering and reusing water from various water and wastewater sources. This study integrates useful membrane technology techniques for water and wastewater treatment containing heavy metals, with the objective of establishing a low-cost, high-efficiency method as well as ideal production conditions: low-cost, high-efficiency selective membranes, and maximum flexibility and selectivity. Future studies should concentrate on eco-friendly, cost-effective, and long-term materials and procedures.

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.

Characterization and Kinetic Studies of Poly(vinylidene fluoride-co-hexafluoropropylene) Polymer Inclusion Membrane for the Malachite Green Extraction

Textile industry effluent contains a high amount of toxic colorants. These dyes are carcinogenic and threats to the environment and living beings. In this study, poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP) was used as the based polymer for PIMs with bis-(2-ethylhexyl) phosphate (B2EHP) and dioctyl phthalate (DOP) as the carrier and plasticizer. The fabricated PIMs were employed to extract the cation dye (Malachite Green; MG) from the feeding phase. PIMs were also characterized by scanning electron microscopy (SEM), atomic force microscope (AFM), contact angle, water uptake, Fourier-transform infrared spectroscopy (FTIR) and ions exchange capacity. The performance of the PIMs was investigated under various conditions such as percentage of carrier and initial dye concentration. With permeability and flux values of 0.1188 cm/min and 1.1913 mg cm/min, PIM produced with 18% w/w PVDF-co-HFP, 21% w/w B2EHP, 1% w/w DOP and 40% w/w THF and was able to achieve more than 97% of MG extraction. The experimental data were then fitted with a pseudo-second-order (PSO) model, and the calculated R2 value was ~0.99. This shows that the data has a good fit with the PSO model. PIM is a potential alternative technology in textile industry effluent treatment; however, the right formulation is crucial for developing a highly efficient membrane.

Recent advances in the removal of pharmaceuticals and endocrine-disrupting compounds in the aquatic system: A case of polymer inclusion membranes

The presence of pharmaceuticals and endocrine-disrupting compounds in aquatic systems is a matter of great concern. The occurrence, fate, and potential toxicity of these compounds have triggered the interest of the scientific community. As a result of their high solubility and low volatility, they are common in aquatic systems, and wastewater treatment plants (WWTP) are the main reservoir for these contaminants. Conventional WWTPs have demonstrated an inability to remove these contaminants completely; hence, different advanced treatment processes have been explored to compensate for the lapses of the conventional system. The outcome of this study revealed the significant improvements made using advanced treatment processes to diminish the number of contaminants; however, some contaminants have proven to be refractory. Thus, there is a need to modify various advanced treatment processes or employ additional treatment processes. Polymer inclusion membranes (PIMs) are a liquid membrane technology that is highly efficient at removing contaminants from water. They have been widely studied for the removal of heavy metals and nutrients from aquatic systems; however, only a few studies have investigated the use of PIMs to remove pharmaceutically active compounds from aquatic systems. This research aims to raise awareness on the application of PIMs as a promising water treatment technology which has a great potential for the remediation of pharmaceuticals and endocrine disruptors in the aquatic system, due to its versatility, ease/low cost of preparation and high contaminant selectivity.

Lactic Acid Permeation through Deep Eutectic Solvents-Based Polymer Inclusion Membranes

Lactic acid that is prepared by fermentation is a compound in food, cosmetic pharmaceutical, and chemical industries. Since a simple technique is desired that separates lactic acid from the cultures, we propose lactic acid permeation through a poly(vinyl chloride)(PVC)-based membrane that contains deep eutectic solvents (DESs) as a carrier. Lactic acid was successfully permeated through polymer inclusion membranes (PIMs) containing hydrophilic DESs, urea-choline chloride and glucose-choline chloride. The permeation behavior was explained by the facilitated transport mechanism based on the solution-diffusion model. Simple preparation of thinner membranes in the PIM process and higher permeation rates are advantages over the supported liquid membrane process. The PVC-based membrane process containing environmentally benign hydrophilic DESs is promising for lactic acid separation on an industrial scale.

Separation and Recovery of Scandium from Sulfate Media by Solvent Extraction and Polymer Inclusion Membranes with Amic Acid Extractants

We report on the separation and recovery of scandium(III) from sulfate solutions using solvent extraction and a membrane transport system utilizing newly synthesized amic acid extractants. Scandium(III) was quantitatively extracted with 50 mmol dm-3 N-[N,N-di(2-ethylhexyl)aminocarbonylmethyl]glycine (D2EHAG) or N-[N,N-di(2-ethylhexyl)aminocarbonylmethyl]phenylalanine (D2EHAF) in n-dodecane at pH 2 and easily stripped using a 0.5 mol dm-3 sulfuric acid solution. The extraction mechanisms of scandium(III) extraction with D2EHAG and D2EHAF were examined, and it was established that scandium(III) formed a 1:3 complex with both extractants (HR), that is, Sc(SO4)2 - aq + 1.5(HR)2org ⇄ Sc(SO4)R(HR)2org + H+ aq + SO4 2- aq. The equilibrium constants of extraction were evaluated to be 4.87 and 9.99 (mol dm-3)0.5 for D2EHAG and D2EHAF, respectively. D2EHAG and D2EHAF preferentially extracted scandium(III) with a high selectivity compared to common transition metal ions under high acidic conditions (0 < pH ≤ 3). In addition, scandium(III) was quantitatively transported from a feed solution into a 0.5 mol dm-3 sulfuric acid receiving solution through a polymer inclusion membrane (PIM) containing D2EHAF as a carrier. Scandium(III) was completely separated thermodynamically from nickel(II), aluminum(III), cobalt(II), manganese(II), chromium(III), calcium(II), and magnesium(II), and partially separated from iron(III) kinetically using a PIM containing D2EHAF as a carrier. The initial flux value for scandium(III) (J 0,Sc = 1.9 × 10-7 mol m-2 s-1) was two times higher than that of iron(III) (J 0,Fe = 9.3 × 10-8 mol m-2 s-1).

Selective removal of silver(i) using polymer inclusion membranes containing calixpyrroles

The transport of Ag(i) across polymer inclusion membranes is reported with derivatives of calixpyrroles with methyl (KP1) and carboxyl (KP2) groups as ion carriers, o-nitrophenyl pentyl ether as a plasticizer and cellulose triacetate as support.

The Effect of Surface Confined Gold Nanoparticles in Blocking the Extraction of Nitrate by PVC-Based Polymer Inclusion Membranes Containing Aliquat 336 as the Carrier

Clusters of gold nanoparticles (AuNPs) formed on the surface of PVC-based polymer inclusion membranes (PIMs) with a liquid phase containing Aliquat 336 as the carrier and in some cases 1-dodecanol or 2-nitrophenol octyl ether as plasticizers were found to inhibit the extraction of nitrate by the PIMs. This observation was based on gradually increasing the mass of AuNPs on the membrane surface and testing the ability of the membrane to extract nitrate after each increase. In this way, it was possible to determine the so-called “critical AuNP masses” at which the studied membranes ceased to extract nitrate. On the basis of these results, it can be hypothesized that the surfaces of these PIMs are not homogeneous with respect to the distribution of their membrane liquid phases, which are present only at certain sites. Extraction takes place only at these sites, and at the “critical AuNP mass” of a PIM, all these extraction sites are blocked and the membrane loses its ability to extract.

A polymer inclusion membrane composed of the binary carrier PC-88A and Versatic 10 for the selective separation and recovery of Sc

This study reports on the selective separation of scandium (Sc) from other rare earth metals (REMs) using a polymer inclusion membrane (PIM). The PIM prepared with PC-88A (2-ethylhexyl hydrogen-2-ethylhexylphosphonate) alone as the carrier showed high extractability but the poor back-extraction of the extracted Sc³⁺ ions did not allow the transport of these ions to the receiving solution of a membrane transport system. To overcome this problem, a novel approach was introduced using a mixture of carriers that allowed Sc³⁺ transport into the receiving solution. A cellulose triacetate (CTA) based PIM containing both PC-88A and Versatic 10 (decanoic acid) as carriers and dioctyl phthalate (DOP) as a plasticizer was prepared for the selective separation of Sc³⁺ from other REM ions in nitrate media. The membrane composition was optimized and the effect of operational parameters such as pH of the feed solution and composition of the receiving solution was explored. The flux at the membrane/feed solution interface was found to depend significantly on the carrier concentration in the PIM, pH of the feed solution and the receiving solution acidity. The newly developed PIM allowed quantitative and selective transport of Sc³⁺ thus demonstrating its suitability for the selective recovery of this metal.

This study reports on the selective separation of scandium (Sc) from other rare earth metals (REMs) using a polymer inclusion membrane (PIM).