High-conductivity microfiltration membranes incorporated with ionic liquids and their superior anti-fouling effectiveness

Molecular Understanding of Polyaniline in Imidazolium-Based Ionic Liquid and Water Mixtures: A Molecular Dynamics Simulation Study

Monitoring interactive influence of cations and anions is inevitable for the development of conductive membranes using polyaniline (PANI). Herein, emeraldine base (EB) and emeraldine salt (ES) forms of PANI structural properties are understood in different imidazolium ionic liquid-water mixtures using molecular dynamics (MD) simulations. The conformational and structural properties of PANI using the combinations of two cations (1-ethyl-3-methylimidazolium [EMIM]+ and 1-butyl-3-methylimidazolium [BMIM]+) and five anions (acetate [ACT]-, formate [FRM]-, trifluoromethyl-sulfonate [TFS]-, benzoate [BEZ]-, and nitrate [NO3]-) are calculated. Based on various structural properties, it is understood that the anions play a dominant interaction with EB or ES compared to cations. Interestingly, it is observed that the radius of gyration shows an increase with [BMIM]+ and a decrease with [EMIM]+ with respect to the increasing size of the anion. There is a decrease in van der Waals interaction for ES due to the elongation of the chain when compared to EB. The excess molar volume shows more solvation behavior for ES than EB. Nevertheless, an increase in anion size leads to the favorable solvation of EB and ES. These observations help in the selection of the best combination of ILs for the sustainable designing of polymer membranes and their applications.

Enhancing textile wastewater reuse: Integrating Fenton oxidation with membrane filtration

The textile industry produces large volumes of wastewater with complex organic pollutants, dyes, and chemicals that are challenging to treat. This study introduces an integrated approach combining Fenton oxidation and membrane filtration in a continuous flow system to improve textile wastewater treatment. The study optimized the removal efficiencies of COD, TOC, and colour by varying the dosages of Fe2+ and H2O2, as well as adjusting the pH and flow rates. Optimal conditions were pH 3.0, 3 mM Fe2+, 10 mM H2O2, and a flow rate of 25 mL/min for both Fenton and photo-Fenton processes. Artificial Neural Networks (ANNs) were employed to simulate and forecast treatment outcomes, identifying reaction time as the most critical factor with relative importance values of 57% for COD and 55% for TOC in Fenton oxidation, and 57% for COD and 49% for TOC in photo-Fenton oxidation. The optimized Fenton process was integrated with microfiltration (MF) and reverse osmosis (RO), to enable the recycling and reuse of wastewater. In the integrated system, COD and TOC removal efficiencies reached 96% and 95%, respectively, following the RO process. Prior to this, after Fenton oxidation, sedimentation, and sand filtration, the COD and TOC removal efficiencies were 70% and 73%, respectively. Colour removal efficiency was 98% after Fenton oxidation, and complete removal was achieved after membrane filtration. The system also significantly reduced electrical conductivity (EC) and concentrations of chloride, sulphate, calcium, and sodium, making the water suitable for reuse. Additionally, the study addressed membrane fouling and proposed strategies to improve long-term operational efficiency. This integrated approach offers a scalable and effective solution for textile wastewater treatment, supporting environmental sustainability and resource conservation.

Antimicrobial polymer-based zeolite imidazolate framework composite membranes for uranium extraction from wastewater and seawater

Extraction uranium (VI) (U(VI)) from wastewater and seawater is highly important for environmental protection and life safety, but it remains a great challenge. In this work, the growth of the zeolitic imidazolate framework-8 (ZIF-8) nanoparticles on the tannic acid (TA)-3-aminopropyltriethoxysilane (APTES) modified PVDF (TAP) membrane was designed to obtain an excellent U(VI) adsorbent. The zeolite imidazolate framework composite membrane (TAPP-ZIF-60) was prepared through polyethyleneimine (PEI) bridging strategy and temperature regulation strategy in solvothermal method. The coordination bond between PEI and ZIF-8 and the covalent bond between PEI and TAP are essential in forming stable composite membrane. TAPP-ZIF with different properties was synthesized through a temperature regulation process and the TAPP-ZIF prepared at 60 °C has the uniform morphology and good performance. The adsorption capacity of TAPP-ZIF-60 is 153.68 mg/g (C0 = 95.01 mg/L and pH = 8.0) and water permeability is 5459 L m-2 h-1 bar-1. After ten adsorption-desorption cycles, it is proved that TAPP-ZIF-60 has good repeatability and stability. In addition, the TAPP-ZIF-60 composites membrane has a good inhibitory effect on Staphylococcus aureus and Escherichia coli. X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) analysis reveal that the coordination between TAPP-ZIF-60 and uranyl ions is the primary factor contributing to the high adsorption capacity.

Structure and Conformational Properties of a Short Polyaniline Chain in a Mixture of Water and Ionic Liquid [1-Ethyl-3-methyl-imidazolium][bistriflimide] Investigated by All-Atom Molecular Dynamics Simulations

Development of antifouling membranes for water treatment using conducting polymers and their composites is a fundamental strategy to mitigate the fouling. This manuscript presents an all-atom molecular dynamics simulations of a conducting polymer, polyaniline (PANI), immersed in an ionic liquids (ILs)-water mixtures. We have considered the ionic liquid 1-ethyl-3-methyl imidazolium bistriflimide, [EMIM]+[BIS]-. The two forms of polyaniline, emeraldine base (EB) and emeraldine salt (ES), were considered. Various intra- and intermolecular structural properties of PANI were analyzed, such as polymer chain radius of gyration Rg, radial distribution functions, and torsional angle distributions. The Rg of EB shows an increase, while the Rg of ES shows a decrease with an increase in the IL concentration. The backbone torsional angle probability distributions show a significant trans state for EB, while a combination of trans and gauche states was observed for ES. Similar supportive distributions were seen in the backbone angular distributions. Radial distribution functions between the carbon atoms at ortho and meta positions of the benzene ring on both ES and EB, as well as the amine group attached between two benzene rings, show an enhanced interaction with the ionic liquid compared to water. Anions have a dominant interaction with the polymer chain when compared to cations. The solvent accessible surface area (SASA) calculations were in accordance with the EB and ES structural properties. The SASA values are more favorable for ES than for EB. H-bond analysis shows a decrease in the number of H-bonds with water as the IL concentration increases.

Facile fabrication of a conductive polypyrrole membrane for anti-fouling enhancement by electrical repulsion and in situ oxidation

Conductive membranes provide a promising method to alleviate membrane fouling, but their cost-effective fabrication, which is urgently needed, is still a challenge. This paper describes the facile fabrication of an ultrafiltration conductive polypyrrole (PPy)-modified membrane (PMM) by in situ chemical polymerization of FeCl₃ and monomer pyrrole vapor on a commercial membrane surface. The resulting membrane had a high electrical conductivity and an outstanding water flux of 2766.55 L m^-2 h^-1 bar^-1. The preparation cost of the PPy deposition was $2.22/m², which was ∼8% of the commercial ultrafiltration membrane cost. Once the PMM was charged at -1 V as a membrane electrode, the normalized water flux was maintained at 92.48 ± 1.14% after fouling by bovine serum albumin (BSA) solutions, which was 18.82% higher than that when the PMM was not charged. The reduced membrane fouling was ascribed to the electrical repulsion between the negatively charged BSA and the PMM cathode. In addition, hydroxyl and sulfate radicals were generated by peroxymonosulfate (PMS) activation on the PMM surface through electron transfer by PPy, which facilitated foulant oxidation. The PPy on the PMM surface was oxidized after catalysis and electrochemically reduced when the PMM was charged as a cathode, exhibiting continuous catalytic ability for PMS activation. These findings provide an alternative method for the facile fabrication of cost-effective conductive membranes to mitigate membrane fouling.