Lamellar Graphene Oxide-Based Composite Membranes for Efficient Separation of Heavy Metal Ions and Desalination of Water

[Image: see text] 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 as-prepared 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.