Electrospun Nanofibers from Waste Polyvinyl Chloride Loaded Silver and Titanium Dioxide for Water Treatment Applications.

The electrospun nanofiber membrane from polyvinyl chloride (PVC) waste for water treatment applications has been successfully produced. The PVC precursor solution was prepared by dissolving the PVC waste in DMAc solvent, and a centrifuge was used to separate undissolved materials from the precursor solution. Ag and TiO2 were added to the precursor solution before the electrospinning process. We studied the fabricated PVC membranes using SEM, EDS, XRF, XRD, and FTIR to study the fiber and membrane properties. The SEM images depicted that Ag and TiO2 addition has changed the morphology and size of fibers. The EDS images and XRF spectra confirmed the presence of Ag and TiO2 on the nanofiber membrane. The XRD spectra showed the amorphous structure of all membranes. The FTIR result indicated that the solvent completely evaporated throughout the spinning process. The fabricated PVC@Ag/TiO2 nanofiber membrane showed the photocatalytic degradation of dyes under visible light. The filtration test on the membrane PVC and PVC@Ag/TiO2 depicted that the presence of Ag and TiO2 affected the flux and separation factor of the membrane.

Recent advances and rational design strategies of carbon dots towards highly efficient solar evaporation.

Solar evaporation using photothermal materials is an environmentally friendly and feasible solution to overcome the water scarcity issue by utilizing the abundant solar energy source. Some key points for efficient solar-to-thermal energy conversion have been extensively studied. Among them, the advancement of solar absorber materials has emerged as an attractive research topic, owing to their potential to enhance the efficiency of solar to thermal conversion significantly. Recently, carbon dots (CDs) have attracted great interest for their applications in this field. CDs have many desirable properties, such as broad light absorption (200-800 nm), high photothermal conversion efficiency (more than 90%), tunable structure and surface functionalization, easy to produce and abundant raw materials that meet the requirements for this application. In this review, the integration of CDs into solar evaporation systems and recent advances in CD-based solar absorbers will be summarized and discussed. Before that, brief knowledge of carbon-based solar thermal evaporation, including its mechanism and strategies to improve the efficiency, is provided, followed by CDs' synthesis and tunable properties that can be optimized for this application. Finally, the challenges and perspectives of research for CD-based solar evaporation are proposed, for example, optimizing solar absorbers by decorating hydroxyl-rich CDs in 2D or 3D structures.

Toughened chitosan-based composite membranes with antibiofouling and antibacterial properties via incorporation of benzalkonium chloride.

Biofouling due to biofilm formation is a major problem in ultrafiltration membrane applications. In this work, a potential approach to solve this issue has been developed by functionalization of chitosan-based membranes with benzalkonium chloride (BKC). The chitosan composite membranes consisting of poly(ethylene glycol) (PEG), multiwalled carbon nanotubes (MWCNT), and BKC were synthesized by mixing the membrane precursors and the antibacterial solution, and casting via an inversed phase technique. The effects of the BKC content on the morphology and performance of the membranes are investigated by varying the BKC feed compositions. The composite membranes demonstrate better antibacterial efficacy against Staphylococcus aureus than Escherichia coli. The permeability and selectivity performances of the composites as filter membranes are examined by employing a dead-end filtration system. Interestingly, enhanced toughness of the membranes is observed as a function of the BKC content. Mechanisms of the structural formation are investigated. The results from SEM, XRD, and FTIR spectroscopy revealed that MWCNT/BKC are located as nanoclusters with π-π stacking interactions, and are covered by PEG chains. The shape of the dispersed domains is spherical at low BKC contents, but becomes elongated at high BKC contents. These act as soft domains with an anisotropic shape with toughening of the brittle chitosan matrix, leading to enhanced durability of the membranes, especially in ultrafiltration applications. The composite membranes also demonstrate improved rejection in dead-end ultrafiltration systems due to high porosity, high hydrophilicity, and the positive charges of the membrane surface.