Photocatalytic Membranes for Efficient Water Treatment

Membrane processes which combine the physical separation through filtration and pollutant degradation or antibacterial properties achieved by photocatalysis in a single unit are gaining popularity as wastewater treatment alternatives. There has been considerable progress in the development of photocatalytic membranes through incorporation of metal-oxide photocatalysts to enhance the performance of the membranes. An optimum amount of the photocatalyst should be incorporated into the membrane in order to realise reasonable photocatalytic activity with minimal consequences on water flux. Besides TiO2 loading, membrane performance is also affected by light intensity and irradiation time. This chapter highlights some of the recent progresses in photocatalytic membrane fabrication, reactor configuration and membrane application in disinfection and pollutant removal from wastewater

Platinum Group Metal Based Nanocatalysts for Environmental Decontamination

Research and development in chemical engineering is currently focused on design of highly active and selective catalytic systems for process intensification. In recent years, there has been growing interest in the use of catalysts based on nanosized metal particles to improve catalytic processes. Among the many metal catalysts, platinum group metals (PGMs) have received greater attention because of their physical and catalytic properties. They have found applications in a wide range of chemical conversion and environmental decontamination reactions due to their chemical stability and enhanced catalytic reactivity in the nano range. This chapter reviews some of the major innovative applications of PGM nanocatalysts for catalytic environmental decontamination

Nitrogen/palladium-codoped TiO² for efficient visible light photocatalytic dye degradation

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Mixed matrix PVDF membranes with in-situ synthesized PAMAM dendrimer- like particles: A new class of sorbents for Cu(II) recovery from aqueous solutions by ultrafiltration

A one-pot method for the preparation of a new family of mixed matrix polyvinylidene fluoride (PVDF) membranes with in-situ synthesized poly(amidoamine) [PAMAM] particles is described. The key feature of this membrane preparation method is the in-situ synthesis of PAMAM dendrimer-like particles in the dope solutions prior to membrane casting using low-generation dendrimers with terminal primary amine groups (G0 and G1-NH2) as precursors and epichlorohydrin (ECH) as cross-linker. By using a combined thermally induced phase separation (TIPS) and non-solvent induced phase separation (NIPS) casting process, a new family of asymmetric PVDF ultrafiltration membranes with (i) neutral and hydrophilic surface layers of average pore diameters of 22−45 nm, (ii) high loadings (∼48 wt %) of dendrimer-like PAMAM particles with average diameters of ∼1.3−2.4 μm, and (iii) matrices with sponge-like microstructures characteristic of membranes with strong mechanical integrity were successfully prepared. Preliminary experiments show that these new mixed matrix PVDF membranes can serve as reusable high capacity sorbents for Cu(II) recovery from aqueous solutions by ultrafiltration

Visible light photodegradation of methyl orange and Escherichia coli O157:H7 in wastewater

Water pollution due to dyes and pathogens is problematic worldwide, and the disease burden is higher in low-income countries where water treatment facilities are usually inadequate. Thus the development of low-cost techniques for the removal of dyes and pathogens in aquatic systems is critical for safeguarding human and ecological health. In this work, we report the fabrication and use of a photocatalyst derived from waste from coal combustion in removing dyes and pathogens from wastewater. Higher TiO2 loading of the photocatalyst increased the removal efficiency for methyl orange (95.5%), and fluorine-doping improved the disinfection efficacy from 76% to 95% relative to unmodified material. Overall, the work effectively converted hazardous waste into a value-added product that has potential in point-of-use water treatment. Future research should focus on upscaling the technique, investigating the fate of the potential of the photocatalysts for multiple reuse, and the recovery of TiO2 in treated water. Significance: • The study provides a pathway for the fabrication of a value-added product from coal fly ash waste.• The use of the proposed nanocomposite material for wastewater treatment represents a potentially affordable, simple, and sustainable technology for point-of-use water treatmen

Double Walled Carbon Nanotube/TiO2 Nanocomposites for Photocatalytic Dye Degradation

Double walled carbon nanotube (DWCNT)/N,Pd codoped TiO2 nanocomposites were prepared by a modified sol-gel method and characterised using FTIR, Raman spectroscopy, TGA, DRUV-Vis, XRD, SEM, and TEM analyses. TEM images showed unique pearl-bead-necklace structured morphologies at higher DWCNT ratios. The nanocomposite materials showed characteristic anatase TiO2 Raman bands in addition to the carbon nanotube D and G bands. Red shifts in the UV-Vis absorption edge were observed at low DWCNT percentages. The photocatalytic activity of DWCNT/N,Pd TiO2 nanocomposite was evaluated by the photocatalytic degradation of eosin yellow under simulated solar light irradiation and the 2% DWCNT/N,Pd TiO2 nanocomposite showed the highest photoactivity while the 20% DWCNT/N,Pd TiO2 hybrid was the least efficient. The photocatalytic enhancement was attributed to the synergistic effects of the supporting and electron channeling role of the DWCNTs as well as the electron trapping effects of the platinum group metal. These phenomena favour the separation of the photogenerated electron-hole pairs, reducing their recombination rate, which consequently lead to significantly enhanced photoactivity

In Situ Generation of Fouling Resistant Ag/Pd Modified PES Membranes for Treatment of Pharmaceutical Wastewater

In this study, Ag and Pd bimetallic nanoparticles were generated in situ in polyethersulfone (PES) dope solutions, and membranes were fabricated through a phase inversion method. The membranes were characterized for various physical and chemical properties using techniques such as FTIR, SEM, AFM, TEM, EDS, and contact angle measurements. The membranes were then evaluated for their efficiency in rejecting EOCs and resistance to protein fouling. TEM micrographs showed uniform distribution of Ag/Pd nanoparticles within the PES matrix, while SEM images showed uniform, fingerlike structures that were not affected by the presence of embedded nanoparticles. The presence of Ag/Pd nanoparticles resulted in rougher membranes. There was an increase in membrane hydrophilicity with increasing nanoparticles loading, which resulted in improved pure water permeability (37–135 Lm2h−1bar−1). The membranes exhibited poor salt rejection (<15%), making them less susceptible to flux decline due to concentration polarization. With a mean pore radius of 2.39–4.70 nm, the membranes effectively removed carbamazepine, caffeine, sulfamethoxazole, ibuprofen, and naproxen (up to 40%), with size exclusion being the major removal mechanism. Modifying the membranes with Ag/Pd nanoparticles improved their antifouling properties, making them a promising innovation for the treatment of pharmaceutical wastewater