The inability of membranes to handle a wide spectrum of pollutants is an important unsolved problem for water treatment. Here we demonstrate water desalination via a membrane distillation process using a graphene membrane where water permeation is enabled by nanochannels of multilayer, mismatched, partially overlapping graphene grains. Graphene films derived from renewable oil exhibit significantly superior retention of water vapour flux and salt rejection rates, and a superior antifouling capability under a mixture of saline water containing contaminants such as oils and surfactants, compared to commercial distillation membranes. Moreover, real-world applicability of our membrane is demonstrated by processing sea water from Sydney Harbour over 72 h with macroscale membrane size of 4 cm2, processing ~0.5 L per day. Numerical simulations show that the channels between the mismatched grains serve as an effective water permeation route. Our research will pave the way for large-scale graphene-based antifouling membranes for diverse water treatment applications.

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Measurements of size distribution, hygroscopicity, and volatility of submicrometer sea spray particles produced by the bubble busting of artificial and natural seawater were conducted to determine their mixing state and volume fractions of hygroscopic and nonhygroscopic species or volatile and nonvolatile species. The particles sprayed from artificial seawater having insoluble silica particles were found to be an external mixture of two groups of particles having hygroscopic growth factors (HGFs) of 1.33 (an internal mixture of nonhygroscopic silica particles and hygroscopic salt species) and 1.68 (a similar mixture having more salt species) when the mass ratio of insoluble particles to dissolved salts was higher than 2. For sea spray particles from natural seawater, the external mixing was not significantly observed because of a high concentration of dissolved salts. The HGFs of sea spray particles (80-140 nm) from natural seawater were in the range of 1.70-1.76, which were lower than from pure artificial seawater (1.87), and the HGFs had no change before and after membrane filtration of seawater, suggesting that the sea spray particles from natural seawater contained a significant amount of nonhygroscopic dissolved organic matter in addition to hygroscopic salt species. The volume fraction of the nonhygroscopic species ranged from 20% to 29%, and the highest value was observed for seawater samples from the site where strong biological activity occurred, suggesting that biological materials played an important role in the formation of nonhygroscopic organic matter. Volatility measurements also identified the existence of volatile organic species in single particles from natural seawater, with the volume fraction of volatile species evaporated at 1008C being 4%-5%.

In this study, Schiff base network-1 (SNW-1) nanoparticles, which are covalent organic frameworks (COFs), were used as fillers in the polyamide (PA) active layer to elevate the performance of thin-film nanocomposite (TFN) forward osmosis (FO) membranes. The TFN membranes were prepared by interfacial polymerization (IP) of m-phenylenediamine (MPD) and trimesoyl chloride (TMC), and the SNW-1 nanoparticles were dispersed in the MPD aqueous solution at various concentrations. The secondary amine groups of SNW-1 nanoparticles reacted with the acyl chloride groups of TMC during the IP reaction to form strong covalent/amide bonds, which facilitated better interface integration of SNW-1 nanoparticles in the PA layer. Additionally, the incorporation of amine-rich SNW-1 nanoparticles into the TFN membranes improved their surface hydrophilicity, and the porous structure of SNW-1 nanoparticles offered additional channels for transport of water molecules. The TFN0.005 membrane with a SNW-1 nanoparticle loading of 0.005 wt.% demonstrated a higher water flux than that of pristine TFC membrane in both AL-FS (12.0 vs. 9.3 Lm -2 h -1 ) and AL-DS (25.2 vs. 19.4 Lm -2 h -1 ) orientations when they were tested with deionized water and 0.5 M NaCl as feed and draw solution, respectively.