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

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 Cr6+ (similar to 87.5%), As3+ (similar to 89.5%), Cd2+ (similar to 93.0%), and Pb2+ (similar to 99.5%) and a good water permeance of similar to 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 similar to 78.0, similar to 80.5, similar to 88.0, and 95.2% for Cr6+, As3+, Cd2+, and Pb2+, respectively, with a DI water permeance of similar to 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, Na2SO4, MgCl2, and MgSO4. 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 similar to 25 days under acidic, basic, and neutral environments as compared to GO/Q composite and pristine GO-based membranes.

Automated summary

Significant efforts have been made to develop efficient graphene oxide (GO) lamellar membranes for heavy metal ion separation and water desalination. However, the selectivity for small ions has remained a challenge. In this study, GO was modified using onion extractive (OE) and quercetin, and the resulting membranes showed excellent rejection efficiency for heavy metal ions and good water permeance. The modified membranes also demonstrated high rejection for small ions and effective filtration of river water. Furthermore, the GO/OE composite membrane exhibited superior stability compared to the GO/Q composite and pristine GO-based membranes.