Visible Light Photodegradation of Rhodamine B Dye by Two Forms of Carbon-Covered Alumina Supported TiO2/Polysulfone Membranes

Leaching of CuO Nanoparticles from PES Ultrafiltration Membranes

Recent studies have incorporated nanoparticles such as CuO, ZnO, and TiO₂ to improve membrane physical and filtration properties. However, one of the major concerns about membrane modification with nanoparticles is the possible leaching of the nanoparticles leading to further contamination of source waters. Therefore, this study investigated the effects of prolonged exposure of polyethersulfone (PES) membranes incorporated with CuO nanoparticles, to different cleaning solutions. The cleaned membranes were extensively characterized for both material properties and separation performance, which enabled a closer look at particle leaching effect through a prolonged exposure. After 840 h of exposure, the presence of CuO in the cleaning solutions was confirmed using dynamic light scattering (DLS), energy-dispersive X-ray spectroscopy (EDS), and inductively coupled plasma mass spectroscopy (ICP-MS) techniques. Nanoparticle leaching resulted in changes in membrane hydrophobicity, surface roughness, pure water permeability, and salt rejection properties. Through comparison with the bare PES membranes, it was shown that cleaning solutions also degraded the membrane polymer. However, the marked effect was less pronounced compared to combined leaching of nanoparticles and degradation of the polymer noted with PES membranes incorporated with CuO nanoparticles. Therefore, when membranes incorporated with nanoparticles are used, a polishing step may be required to remove potentially leached nanoparticles. Leached nanoparticles may result in secondary pollution and pose a health risk concern to nontarget organisms. This work provides insights into the stability of nanocomposite membranes, and the achieved results can be extrapolated to other nanoparticles such as TiO₂ and ZnO because they possess similar physicochemical behavior.

Non-purified commercial multiwalled carbon nanotubes supported on electrospun polyacrylonitrile@polypyrrole nanofibers as photocatalysts for water decontamination

We present a photoactive composite material for water decontamination consisting of non-purified commercial multiwalled carbon nanotubes (CNT(NP)s) supported on an electrospun polymeric mat made of core-sheath polyacrylonitrile-polypyrrole nanofibers. This is the first system that specifically exploits the superior photocatalytic activity of CNT(NP)s compared with the purified carbon nanotubes usually employed. A CNT(NP) still contains the catalytic metal oxide nanoparticles (NPs) used for its synthesis, embedded in the nanotube structure. Under UV-visible irradiation, these NPs generate highly reactive ˙OH radicals capable of degrading the organic molecules adsorbed on the nanotube. Photocatalytic tests on the composite material show that CNT(NP)s act mostly as a source of photogenerated charge carriers. The adsorption of target substrates occurs preferentially onto the polypyrrole sheath, which shuttles the reactive carriers from CNT(NP)s to the substrates. In addition, UV-visible irradiation of semiconducting polypyrrole generates radical species that directly react with the adsorbed substrates. All synthetic procedures reported are scalable and sustainable. This mechanically resistant and flexible composite overcomes one of the weakest aspects of water treatments that employ suspended nanocatalysts, namely the expensive and poorly scalable recovery of the catalyst through nanofiltration. All these features are required for large-scale photocatalytic treatments of polluted water.

Organic–inorganic bimetallic hybrid particles with controllable morphology for the catalytic degradation of organic dyes

Amphiphilic bimetallic hybrid Janus nanoparticles with controllable morphology and ability to perform highly efficient catalytic degradation of organic dyes.

Development of hydrophilic GO-ZnO/PES membranes for treatment of pharmaceutical wastewater

Membrane application in water reclamation is challenged by fouling which deteriorates membrane performance in terms of permeate flux and solute rejection. Several studies focusing on antifouling membranes incorporated with nanoparticles have been carried out, but these membranes are not yet a viable solution due to their high energy requirements and inability to completely remove or degrade trace organic compounds (TOrCs). Therefore, this study aims at fabricating polyethersulfone (PES) membranes for treatment of pharmaceutical wastewater by using a unique membrane synthesis approach. PES membranes were synthesised by casting two different solutions before coagulation. Therefore, the synthesis technique was called 'double-casting phase inversion'. The membranes were impregnated with nanohybrid graphene oxide-zinc oxide (GO-ZnO) to increase their hydrophilicity, rejection of pharmaceuticals (by decreasing membrane-solute hydrophobic interactions), resistance to organic fouling and photodegradation properties. The addition of GO-ZnO increased membrane hydrophilicity and pure water permeability. The rejection of TOrCs and anti-fouling properties were also improved due to a reduction in membrane-solute and membrane-foulant hydrophobic interactions, respectively. In addition to improved TOrC rejection properties and resistance to fouling, GO-ZnO/PES membranes degraded Brilliant Black.

Fabrication of organic–inorganic hybrid membranes composed of poly(vinylidene fluoride) and silver cyanamide and their high photocatalytic activity under visible light irradiation

An active photocatalytic membrane composed of silver cyanamide and poly(vinylidene fluoride) showed high photocatalytic efficiency toward the degradation of Acid Blue 1 under visible light irradiation.

Synthesis of a visible-light active V2O5–g-C3N4 heterojunction as an efficient photocatalytic and photoelectrochemical material

Synergistic enhancement of the photocatalytic degradation of DR81 using V₂O₅–g-C₃N₄ is due to an increase in visible-light absorption efficiency and rapid photoinduced charge separation.

Preparation and performance studies of polysulfone-sulfated nano-titania (S-TiO2) nanofiltration membranes for dye removal

Polysulfone nanofiltration membranes containing sulfated nano-titania (S-TiO₂) were fabricated, with the aim to enhance the membrane properties along with the possible rejection of Methylene Blue (MB) dye by membranes.