Graphene oxide (GO)‐based membranes have been widely investigated for separation of dyes, salt ions, heavy metal ions, and biomolecules due to their high mechanical strength, single‐layered structure, large surface area, and high affinity. However, due to irregular pore structure, nanochannels, interlayer distance, easy functionalization, swelling effect, and chemical stability under aqueous environment limited their separation efficiency. In this review, different fabrication methods of GO membranes are summarized. The role of functionalization and cross‐linking on membrane's structural properties, separation performance, and practical applications are discussed. Further, the GO‐based membranes (GOMs) for separation and removal of heavy metal ions are discussed in detail. The factors which influence the separation performance are also highlighted. Finally, recommendations and future directions are suggested.

Sufficient efforts have been carried out to fabricate highly efficient graphene oxide (GO) lamellar membranes for heavy metal ion separation and desalination of water. However, selectivity for small ions remains a major problem. Herein, GO was modified by using onion extractive (OE) and a bioactive phenolic compound, i.e., quercetin. The asprepared modified materials were fabricated into membranes and used for separation of heavy metal ions and water desalination. The GO/onion extract (GO/OE) composite membrane with a thickness of 350 nm shows an excellent rejection efficiency for several heavy metal ions such as Cr 6+ (∼87.5%), As 3+ (∼89.5%), Cd 2+ (∼93.0%), and Pb 2+ (∼99.5%) and a good water permeance of ∼460 ± 20 L m −2 h −1 bar −1 . In addition, a GO/quercetin (GO/Q) composite membrane is also fabricated from quercetin for comparative studies. Quercetin is an active ingredient of onion extractives (2.1% w/w). The GO/Q composite membranes show good rejection up to ∼78.0, ∼80.5, ∼88.0, and 95.2% for Cr 6+ , As 3+ , Cd 2+ , and Pb 2+ , respectively, with a DI water permeance of ∼150 ± 10 L m −2 h −1 bar −1 . Further, both membranes are used for water desalination by measuring rejection of small ions such as NaCl, Na 2 SO 4 , MgCl 2 , and MgSO 4 . The resulting membranes show >70% rejection for small ions. In addition, both membranes are used for filtration of Indus River water and the GO/Q membrane shows remarkably high separation efficiency and makes river water suitable for drinking purpose. Furthermore, the GO/QE composite membrane is highly stable up to ∼25 days under acidic, basic, and neutral environments as compared to GO/Q composite and pristine GO-based membranes.

In this study, two-dimensional graphene oxide-based novel membranes were fabricated by modifying the surface of graphene oxide nanosheets with six-armed poly(ethylene glycol) (PEG) at room conditions and used for organic solvent nanofiltration applications.