High-Efficiency Recovery of Acetic Acid from Water Using Electroactive Gas-Stripping Membranes.

Recovery of carbon-based resources from waste is a critical need for achieving carbon neutrality and reducing fossil carbon extraction. We demonstrate a new approach for extracting volatile fatty acids (VFAs) using a multifunctional direct heated and pH swing membrane contactor. The membrane is a multilayer laminate composed of a carbon fiber (CF) bound to a hydrophobic membrane and sealed with a layer of polydimethylsiloxane (PDMS); this CF is used as a resistive heater to provide a thermal driving force for PDMS that, while a highly hydrophobic material, is known for its ability to rapidly pass gases, including water vapor. The transport mechanism for gas transport involves the diffusion of molecules through the free volume of the polymer matrix. CF coated with polyaniline (PANI) is used as an anode to induce an acidic pH swing at the interface between the membrane and water, which can protonate the VFA molecule. The innovative multilayer membrane used in this study has successfully demonstrated a highly efficient recovery of VFAs by simultaneously combining pH swing and joule heating. This novel technique has revealed a new concept in the field of VFA recovery, offering promising prospects for further advancements in this area. The energy consumption was 3.37 kWh/kg for acetic acid (AA), and an excellent separation factor of AA/water of 51.55 ± 2.11 was obtained with high AA fluxes of 51.00 ± 0.82 g.m-2hr-1. The interfacial electrochemical reactions enable the extraction of VFAs without the need for bulk temperature and pH modification.

Ultra-low graphene oxide loading for water permeability, antifouling and antibacterial improvement of polyethersulfone/sulfonated polysulfone ultrafiltration membranes.

The aqueous dispersion of graphene oxide (GO) was employed as additive to fabricate antifouling and antibacterial polyethersulfone (PES)/sulfonated polysulfone (SPSf)/GO mixed matrix membranes (MMMs) by the non-solvent induced phase separation (NIPS). The effect of different amounts of GO on the morphology and performance of MMMs were studied. The results showed that the casting solution exhibited an increasing trend in viscosity with increment in GO concentration (from 0 to 0.016 wt%) owing to the hydrogen bonding (H-bonding) interaction among GO, H2O and SPSf. Raman and molecular dynamic (MD) simulations analyses confirmed that there existed H-bonding interaction among SPSf, GO and H2O. Specifically, the agglomeration of GO was inhibited and stable homogeneous casting solution was obtained. Meanwhile, the H-bonding interaction also played a key role in the MMMs structure and improved properties. It was found that GO nanosheets were uniformly embedded to form many cellular-like voids in the asymmetric PES/SPSf/GO MMMs with a sponge-like structure. The pure water flux of the MMMs with a very low GO content of 0.012 wt% was up to 816.9 L/m2h and the rejection of bovine serum albumin (BSA) was more than 99.2% under a pressure of 0.1 MPa. Additionally, the mechanical properties of MMMs was also improved with the increase of GO content. Importantly, the MMMs displayed excellent antifouling and antibacterial performance. A high fouling recovery (94.2%) and antibacterial rate (90.0%) against Escherichia coli (E. coli) obtained were attributed to improved hydrophilicity, enhanced negative charge and GO nano-size effect. In summary, our study provides a simple approach to tailor MMMs with the enhancement of permeation, antifouling and antibacterial properties at a very low content of GO.

The role of nanoparticles in the performance of nano-enabled composite membranes - A critical scientific perspective.

This review looks into the efforts made towards commercializing nano-enable flat sheet membranes as well as the challenges that need to be overcome. There is a question mark on the argument that the nano-pores of the fillers play a significant role in the performance of the membrane. Non porous nanomaterials have been reported to cause in increase in water flux, yet there are still articles that credit the nano-pores of the nanomaterials for improved membrane performance. There are two points that are important to highlight: (1) the nanoparticles, e.g. zeolites, are smaller in diameter compared to the thickness, (2) the loading rate of the filler phase is significantly small in relation to continuous phase. Therefore, it cannot be correct to assume that the nanomaterials provide continuous flow channels in the selective layer. There is no dispute here that the addition of NP enhances the performance of a membrane, but it is the perception that the nano-pores are the reason that we disagree with.