Crosslinked or non-crosslinked ultrathin semipermeable membranes based on the N-butylated and N-butylsulfonated polybenzimidazole (BPBI and BSPBI) were successfully prepared by spin-coating method. Structural characterization by FTIR and WAXD revealed that the N-substitution and the crosslinked structure of PBI suppressed the hydrogen bonding and increased the d-spacing. Furthermore, positron annihilation lifetime spectroscopy (PALS) clearly showed the pore radius change from 0.27-0.29 nm to 0.33 nm by crosslinking. As a result, the enhancement of water flux and NaCl rejection was achieved by the crosslinking of the BPBI and BSPBI. Especially, the crosslinked N-butylsulfonated PBI (CL-BSPBI) membrane significantly improved not only salt rejection but also water flux (NaCl rejection : 46 %, water flux : 22.1 L m-2 h-1) compared to those of non-crosslinked BSPBI one (NaCl rejection : 11 %, water flux : 1.88 L m-2 h-1) due to both the Donnan effect and the formation of larger pores in the membrane, respectively.

Advanced materials with desired wettability are extremely important for environmental sustainability, such as oily industrial wastewater treatment and oil spill cleanup. To meet this demand, a scalable nanoengineering approach was developed to fabricate superhydrophilic and underwater superoleophobic inorganic meshes for cross-flow filtration and oil/water separation. The resulting nanostructured copper meshes exhibit superhydrophilicity and underwater superoleophobicity (oil contact angle approaching to 159°). With these meshes, very high values of filtration flux (≥900,000 Lh-1m-2) have been achieved, with ultra-low oil residue in the filtrate (<40 ppm) and long water retention time (more than 1 h). The proposed nanoengineering method paves the way for effective gravity-driven separation of immiscible oil/water mixtures, especially for low-density oil purification.

Nanofiltration technology is being investigated as a cost-effective and environmentally acceptable mechanism of sustaining industrial and public water systems. Nanofiber membranes are part of the family of filtration devices being used to remove inorganics and organics from water systems. This study investigates the use of the natural material, Opuntia ficus-indica (Ofi) cactus mucilage, as a tool for nanofiber membrane filtration. Mucilage is a natural, non-toxic, bio-compatible, biodegradable, inexpensive and abundant material. Mucilage is a clear colorless substance comprised of proteins, mono-saccharides, and polysaccharides. It also contains organic species, which give it the capacity to interact with metals, cations and biological substances promoting flocculation for removing arsenic, bacteria, E. coli, and other particulates from drinking water. This natural material has the potential to be used as a sustainable method for water filtration and contaminant sensing. Therefore, mucilage nanofiber membranes were electrospun with volume ratios of polyvinyl alcohol (PVA) and polystyrene (PS) to mucilage comparing the interaction of non-polar solvents. Atomic Fluorescence Spectrometry (AFS) from PSAnalytical was used to evaluate electrospun nanofiber membranes made from volume ratios ranging from 30:70 to 70:30 of mucilage: polyvinyl alcohol, mucilage: polystyrene-D-limonene, and mucilage: polystyrene–toluene in different proportions. The mucilage nanofiber membranes were used as filtration devices for 50 ppb arsenic solutions. Arsenic, being a toxic substance, acts as a deadly poison in water systems and has plagued societal preservation for centuries. The total arsenic content in the samples were measured before and after treatment. Comparative tests were also performed using 1) coated and non-coated GVWP 0.22 µm and 0.45 µm filters from Millipore and 2) columnar flow through Pasteur glass pipets filled with 0.5 g of pre-washed sand from Fisher Scientific and 0.01 g of mucilage nanofibers. Results show mucilage: polystyrene nanofiber membrane filters were capable of removing arsenic from test solutions, in terms of the percentage of arsenic removed. These data elucidate that mucilage nanofiber membranes have the potential to serve as the basis for the next generation of economically sustainable filtration devices that make use of a natural non-toxic material for sustainable water systems.

Cellulose was selectively converted to sugar alcohols (sorbitol and mannitol) over a supported-metal catalyst ruthenium on carbon (Ru/C) by the application of plasma in cellulose aqueous suspension. Generally, conversion of cellulose to sugar alcohol should be done under H2 pressure and high temperature. The goal of using solution plasma process (SPP) in this study is to initiate “self-hydrogenation” by reactive hydrogen species generated from the plasma due to dissociation of water medium. The sugar alcohols were produced at room temperature and atmospheric pressure. Electrospray ionization mass spectrometric analysis indicates that the SPP is a potent tool to promote the conversion of cellulose to sugar alcohols.