Abstract: The present invention provides a multi-stage filter system suitable for the production of drinking water from a wide variety of contaminated water sources. The modular nature of the multi-stage filter system allows for the customization of filter combinations according to the remediation requirements. The multi-stage filter system comprises a coarse filter (S1); an ultrafiltration filter (S2); a graphene-based filter (S3); and a residual nanoparticle filter (S4). The graphene-based filter cartridge comprises few-layer graphene powder; a combination of few-layer graphene powder and pellets comprising a mixture of polyethersulfone, graphene oxide (GO), and dimethylformamide; a composite comprising chitosan, GO, sodium sulfate and ferric chloride; or a combination of few-layer graphene powder, granular activated carbon and a composite comprising chitosan, GO, sodium sulfate and ferric chloride.

Abstract: There is provided a graphene-based membrane, particularly a free-standing one, comprising: a plurality of partially oxidised few-layer graphene (POFG) sheets; and a polymer for interconnecting the plurality of POFG sheets in a matrix. In the preferred embodiment, the polymer is water-based polymer. There is also provided a method of forming the free-standing graphene-based membrane; and a method of preparing the POFG sheets, comprising: electrochemically exfoliating graphite to form intercalated graphite powder; expanding the intercalated graphite powder to form few-layer graphene (FG); and partially oxidizing the FG with an oxidizing agent for a pre-determined period of time to form POFG sheets.