Dye Separation and Antibacterial Activities of Polyaniline Thin Film-Coated Poly(phenyl sulfone) Membranes

Review on polyaniline-based nanocomposite heterogeneous catalysts for catalytic reduction of hazardous water pollutants

Water contamination by highly toxic substances has generated serious ecological disturbances and health problems for humans. Hence, decontamination of toxic pollutants using advanced, inexpensive, and eco-friendly approaches is the current demand. Heterogeneous catalyst-based catalytic reduction processes have offered the opportunity to transform hazardous water pollutants into non-hazardous products via sustainable, eco-friendly, and efficient routes and might be a competitive substitute for existing traditional water purification techniques. However, the key challenges linked with pure heterogeneous catalysts include agglomeration and poor dispersion, stability, recovery, and reusability, which result in poor activity and efficiency. Thus, it is essential to produce multipurpose polymer-based composite catalysts using conducting polymers, which are exceptionally good supportive and matrix materials. The blending of metal-based nanomaterials with polyaniline conducting polymers produces highly stable and efficient heterogeneous nanocomposite catalysts with amazing catalytic activity against a wide range of water pollutants. The heterogeneous catalytic reductive degradation of immensely toxic pollutant water has gained substantial curiosity because of its excellent physicochemical and surface characteristics, porous structure, recoverability, and recyclability. Therefore, this review presents the latest efforts to generate various polyaniline-based nanocomposite catalysts using a polyaniline matrix and various nanofiller materials and their potential applications in heterogeneous catalytic reduction degradation of water pollutants.

Influence of PEG-PPG-PEG Block Copolymer Concentration and Coagulation Bath Temperature on the Structure Formation of Polyphenylsulfone Membranes

The effect of amphiphilic block copolymer polyethylene glycol (PEG)-polypropylene glycol (PPG)-PEG concentration in the polyphenylsulfone (PPSU) casting solution and coagulation bath temperature (CBT) on the structure, separation, and antifouling performance of PPSU ultrafiltration membranes was studied for the first time. According to the phase diagram obtained, PPSU/PEG-PPG-PEG/N-methyl-2-pyrrolidone (NMP) systems are characterized by a narrow miscibility gap. It was found that 20 wt.% PPSU solutions in NMP with the addition of 5-15 wt.% of PEG-PPG-PEG block copolymer feature upper critical solution temperature, gel point, and lower critical solution temperature. Membrane composition and structure were studied by Fourier-transform infrared spectroscopy, scanning electron and atomic force microscopies, and water contact angle measurements. The addition of PEG-PPG-PPG to the PPSU casting solution was found to increase the hydrophilicity of the membrane surface (water contact angle decreased from 78° for the reference PPSU membrane down to 50° for 20 wt.%PPSU/15 wt.% PEG-PPG-PEG membrane). It was revealed that the pure water flux increased with the rise of CBT from 18-20 L·m-2·h-1 for the reference PPSU membrane up to 38-140 L·m-2·h-1 for 20 wt.% PPSU/10-15 wt.% PEG-PPG-PEG membranes. However, the opposite trend was observed for 20 wt.% PPSU/5-7 wt.% PEG-PPG-PEG membranes: pure water flux decreased with an increase in CBT. This is due to the differences in the mechanism of phase separation (non-solvent-induced phase separation (NIPS) or a combination of NIPS and temperature-induced phase separation (TIPS)). It was shown that 20 wt.% PPSU/10 wt.% PEG-PPG-PEG membranes were characterized by significantly higher antifouling performance (FRR-81-89%, DRr-26-32%, DRir-10-20%, DT-33-45%) during the ultrafiltration of bovine serum albumin solutions compared to the reference PPSU membrane prepared at different CBTs (FRR-29-38%, DRr-6-14%, DRir-74-89%, DT-88-94%).

Novel polyaniline-polyethersulfone nanofiltration membranes: effect of in situ polymerization time on structure and desalination performance

In this research, novel polyaniline-layered nanofiltration membranes were prepared by phase inversion of base polyethersulfone (PES) membranes and subsequent in situ solution-phase deposition of polyaniline as a thin surface layer. In these composite membranes, the impact of the polyaniline deposition time on steric hindrance and electrostatic interactions during permeation was elucidated. The chemical structure, thermal stability, and mechanical properties of the PES and PANI-PES membranes were investigated using Fourier-transform infrared spectroscopy (ATR-FTIR), thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA), respectively. The membranes' porosity and pore size decreased as PANI deposition time increased. As PANI deposition time increased, PANI layered nanofiltration membranes exhibited improved thermal stability but deteriorated mechanical characteristics due to free radical destruction from prolonged exposure to the oxidant. These PANI-PES membranes showed 43% rejection (NaCl) at 1.7 bar coupled with a flux of 11.59 L h-1 m2 that is quite promising when comparing with similar Nanofilteration (NF) membranes in the literature and commercial NF membranes, as well. As the deposited layer, PANI is partially doped; hence, permeation results have been interpreted in terms of steric hindrance and electrostatic repulsion by electrochemical PANI layering.

Recent Advances in the Removal of Organic Dyes from Aqueous Media with Conducting Polymers, Polyaniline and Polypyrrole, and Their Composites

Water pollution by organic dyes, and its remediation, is an important environmental issue associated with ever-increasing scientific interest. Conducting polymers have recently come to the forefront as advanced agents for removing dye. The present review reports on the progress represented by the literature published in 2020-2022 on the application of conducting polymers and their composites in the removal of dyes from aqueous media. Two composites, incorporating the most important polymers, polyaniline, and polypyrrole, have been used as efficient dye adsorbents or photocatalysts of dye decomposition. The recent application trends are outlined, and future uses also exploiting the electrical and electrochemical properties of conducting polymers are offered.

Development of High Flux Nanocomposite Polyphenylsulfone/Oxidized Multiwalled Carbon Nanotubes Membranes for Ultrafiltration Using the Systems with Critical Solution Temperatures

The study deals with the investigation of the effect of the modification of polyphenylsulfone (PPSU) flat sheet membranes for ultrafiltration using oxidized multiwalled carbon nanotubes (O-MWCNT) in order to enhance membrane permeability and antifouling performance. The effect of O-MWCNT loading to the PPSU-polyethylene glycol (PEG-20,000, M_n = 20,000 g·mol⁻¹)-polyvinylpyrrolidone (PVP K-30, M_n = 40,000 g·mol⁻¹)-N-methy-2-pyrrolidinone (NMP) colloid systems on the phase state and viscosity was studied. It was found that PPSU-PEG-20,000-PVP K-30-O-MWCNT-NMP colloid systems feature a gel point (T = 35–37 °C) and demixing temperature (T = 127–129 °C) at which two bulk phases are formed and a polymer system delaminates. According to the study of the phase state and viscosity of these colloid systems, a method for the preparation of high flux PPSU membranes is proposed which includes processing of the casting solution at the temperature higher than gel point (40 °C) and using a coagulation bath temperature lower than gel point (25 °C) or lower than demixing temperature (40 °C and 70 °C). Membrane structure, topology and hydrophilic-hydrophobic balance were investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM) and water contact angle measurements. The effect of coagulation bath temperature and O-MWCNT concentration on the membrane separation and antifouling performance in ultrafiltration of human serum albumin and humic acids solutions was studied. It was found that the modification of PPSU ultrafiltration membranes by O-MWCNTs yielded the formation of a thinner selective layer and hydrophilization of the membrane surface (water contact angle decreased from 53–56° for the reference PPSU membrane down to 33° for the nanocomposite membrane with the addition of 0.19 wt.% O-MWCNT). These changes resulted in the increase in membrane flux (from 203–605 L·m⁻²·h⁻¹ at transmembrane pressure of 0.1 MPa for the reference membrane up to 512–983 L·m⁻²·h⁻¹ for nanocomposite membrane with the addition of 0.19 wt.% O-MWCNT depending on coagulation bath temperature) which significantly surpasses the performance of PPSU ultrafiltration membranes reported to date while maintaining a high level of human serum albumin rejection (83–92%). It was revealed that nanocomposite membrane demonstrated better antifouling performance (the flux recovery ratio increased from 47% for the reference PPSU membrane up to 62% for the nanocomposite membrane) and higher total organic carbon removal compared to the reference PPSU membrane in humic acids solution ultrafiltration.

Antibacterial Performance of Protonated Polyaniline-Integrated Polyester Fabrics

During the last few years, there has been an increase in public awareness of antimicrobial fabrics, as well as an increase in commercial opportunities for their use in pharmaceutical and medical settings. The present study reports on the optimized fabrication of protonated polyaniline (PANI)-integrated polyester (PES) fabric. Para-toluene sulfonic acid (pTSA) was used to protonate the PANI fabric and thus grant it antibacterial performance. The results of a 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging assay showed high antioxidant activity of protonated PANI fabric at a scavenging efficiency of 84.83%. Moreover, the findings revealed remarkably sensitive antibacterial performance of PANI-integrated fabric against the following Gram-positive bacteria: methicillin-resistant Staphylococcus aureus (MRSA), S. epidermidis, and S. aureus; and also against the following Gram-negative bacteria: P. aeruginosa, E. coli, and S. typhi. Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy and energy dispersive X-ray fluorescence (EDXRF) were used to determine the changes in the structural and elemental compositions of PANI fabric upon treatment with bacterial strains. Electrochemical impedance spectroscopy (EIS) revealed that the electrical conductivity value of protonated PANI fabric decreased by one (1) order of magnitude against P. aeruginosa and S. aureus, from 3.35 ± 7.81 × 10-3 S cm-1 to 6.11 ± 7.81 × 10-4 S cm-1 and 4.63 ± 7.81 × 10-4 S cm-1, respectively. Scanning electron microscopy (SEM) analysis showed the disruption of bacterial membranes and their structures when exposed to protonated PANI fabric; meanwhile, thermogravimetric analysis (TGA) demonstrated that the fabric retained its thermal stability characteristics. These findings open up potential for the use of antimicrobial fabrics in the pharmaceutical and medical sectors.

Recent Advancements in Polyphenylsulfone Membrane Modification Methods for Separation Applications

Polyphenylsulfone (PPSU) membranes are of fundamental importance for many applications such as water treatment, gas separation, energy, electronics, and biomedicine, due to their low cost, controlled crystallinity, chemical, thermal, and mechanical stability. Numerous research studies have shown that modifying surface properties of PPSU membranes influences their stability and functionality. Therefore, the modification of the PPSU membrane surface is a pressing issue for both research and industrial communities. In this review, various surface modification methods and processes along with their mechanisms and performance are considered starting from 2002. There are three main approaches to the modification of PPSU membranes. The first one is bulk modifications, and it includes functional groups inclusion via sulfonation, amination, and chloromethylation. The second is blending with polymer (for instance, blending nanomaterials and biopolymers). Finally, the third one deals with physical and chemical surface modifications. Obviously, each method has its own limitations and advantages that are outlined below. Generally speaking, modified PPSU membranes demonstrate improved physical and chemical properties and enhanced performance. The advancements in PPSU modification have opened the door for the advance of membrane technology and multiple prospective applications.