Improving reverse osmosis (RO) membrane performance is important for mitigating increasing stresses on global water demand. Membrane fouling by mineral scaling, natural organic matter, and biofilm formation during RO will decrease drinking water production efficiency. To reduce fouling and extend membrane life, we modified a commercial, polyamide (PA) thin film composite membrane surfaces with: (1) graphene oxide (GO), a bactericidal nanosheet which was also used to template Au nanoparticle formation; (2) Au nanostars (AuNS) which exhibit photothermal properties to kill bacteria at the membrane surface; and (3) polyethylene glycol (PEG) grafted to the AuNS to help repel bacteria and organic matter and decrease mineral scaling. Scale formation was examined using calcium carbonate and calcium sulfate, natural organic matter fouling was modeled using humic acid, and Escherichia coli was used to model biofouling in our study. Membrane surfaces were characterized using scanning electron, transmission electron, and Raman microscopy. Batch experiments on the PA–GO–AuNS–PEG membrane show that mineral scaling was dramatically reduced mineral scaling and organic fouling, and E. coli fluorescence images indicate complete bacterial lysis after exposure to an 808 nm laser at low power density (0.4 W/cm2). Interestingly, in addition to its intended function of killing bacteria on the membrane surface, the AuNS modification also possesses anti-scaling properties. Furthermore, to determine whether the extensive membrane surface modifications would reduce membrane flux and permeate rejection, the PA–GO–AuNS–PEG membranes were tested in a benchtop RO system. Compared to PA membranes, the PA–GO–AuNS–PEG membranes exhibited higher permeate flux, and similar or superior rejection of salts and humic acid. Our unique, synergistic membrane design suggests a highly effective low-energy RO system option by offering new and exciting improvement towards strengthening RO water treatment.

Photothermal and hydrophilic functionalization of reverse osmosis membranes for enhanced resistance of mineral scaling, organic, and bio-fouling

253rd National Meeting (2017)

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