Surface-modified anion exchange membranes with self-cleaning ability and enhanced antifouling properties

Eco-friendly, green synthesized copper oxide nanoparticle (CuNPs) from an important medicinal plant Turnera subulata Sm. and its biological evaluation

In this report, the green fabrication of copper oxide nanoparticles (CuNPs) using Turnera subulata leaf extract and assessed for the antibacterial and photocatalytic activities. The synthesis of CuNPs was performed using the leaves of T. subulata (TS-CuNPs) and characterized using UV-visible spectrophotometry, Fourier transforms infrared spectroscopy (FT-IR), Scanning electron microscopy (SEM), and Energy-dispersive X-ray spectroscopy (EDX). Produced TS-CuNPs showing transmittance peaks approximately 707-878 cm^-1, with a spherical shape particle with an average size of 58.5 nm. As synthesized TS-CuNPs were used as a coating material in cotton fabrics and tested the efficacy against Gram-negative and Gram-positive bacterial pathogens. TS-CuNPs inhibited the growth of Escherichia coli and Staphylococcus aureus on cotton fabrics. Antibiofilm activity of TS-CuNPs showed a 4-fold reduction in the biofilm formation of E. coli and S. aureus. Structural morphology of TS-CuNPs coated on cotton fabric analysis using SEM-EDX confirmed the attachment of TS-CuNPs and reduction in the bacterial attachment to the cotton fabrics. Thus, this study provides a potential strategy to improve the antibacterial property of cotton fabrics in textile production for medical, sportswear, and casual wear applications. Further, the photocatalytic activity against the tested dyes evident the potential in dye industry wastewater treatment. Hence, this work represents a simple, greener, and cost-effective route for in situ synthesis of CuNPs with the potential antibacterial and as a dye degradation agent for water remediation.

Effect of the bio-inspired modification of low-cost membranes with TiO2:ZnO as microbial fuel cell membranes

Microbial fuel cells (MFCs) are a novel technique for converting biodegradable materials into electricity. In this study, the efficiency of mixed crystal (TiO₂:ZnO) as a membrane modifier of a low-cost, antifouling and self-cleaning cation exchange membrane for MFCs was studied. The modification was prepared using polydopamine (PDA) as the bio-inspired glue, followed by gravity deposition of a mixture of catalyst nanoparticles (TiO₂:ZnO 0.03%, 1:1 ratio) as anti-biofouling agents. The effects of the membrane modification were evaluated in terms of power density, open circuit potential, coulombic efficiency, anti-biofouling properties and also color and COD removal efficiency. The results showed that the use of the PDA-modified membrane and a mixture of catalysts facilitated the transfer of cations released during the oxidation process in the anodic compartment of the MFC, which increased the power generation in the MFC by 2.5 times and 5.7 times the current compared to pristine and PDA pristine membranes, decreased the MFC operating cycle time from 5 to 3 days, doubled the lifetime of the membranes and demonstrated higher COD removal efficiency and color removal. Finally, SEM and AFM analysis showed that the modification significantly minimized surface fouling. The modified membranes in this study proved to be a potential alternative to the expensive membranes currently used in MFCs, furthermore, this modification could be an interesting alternative modification for other potential membranes for use in MFCs, due to the fact that the catalyst activation was only performed with visible light (artificial and solar), which could decrease operating costs.

The Development of Electroconvection at the Surface of a Heterogeneous Cation-Exchange Membrane Modified with Perfluorosulfonic Acid Polymer Film Containing Titanium Oxide

One way to enhance mass transfer and reduce fouling in wastewater electrodialysis is stimulation of electroconvective mixing of the solution adjoining membranes by modifying their surfaces. Several samples were prepared by casting the perfluorosulfonic acid (PFSA) polymer film doped with TiO₂ nanoparticles onto the surface of the heterogeneous cation-exchange membrane MK-40. It is found that changes in surface characteristics conditioned by such modification lead to an increase in the limiting current density due to the stimulation of electroconvection, which develops according to the mechanism of electroosmosis of the first kind. The greatest increase in the current compared to the pristine membrane can be obtained by modification with the film being 20 μm thick and containing 3 wt% of TiO₂. The sample containing 6 wt% of TiO₂ provides higher mass transfer in overlimiting current modes due to the development of nonequilibrium electroconvection. A 1.5-fold increase in the thickness of the modifying film reduces the positive effect of introducing TiO₂ nanoparticles due to (1) partial shielding of the nanoparticles on the surface of the modified membrane; (2) a decrease in the tangential component of the electric force, which affects the development of electroconvection.