Facile synthesis of smart magnetic graphene for safe drinking water: Heavy metal removal and disinfection control

Bacterial infections, the toxicity of engineered nanomaterials, the presence of inorganic pollutants in the environment, and providing safe drinking water are the most threatening problems of the 21st century. To tackle these challenges, we develop a one-pot, solvent free, and rapid synthesis of smart magnetic graphene (SMG) by microwave irradiation of graphene oxide (GO) and ferrocene precursors. The SMG possesses increased adsorption sites with tunable superparamagnetic properties (50 emu/g, 1:7 wt %), facilitating the adsorption and magnetic separation of aqueous Cr(VI), As(V), and Pb(II) with ∼99% removal efficiencies down to the 1 ppb level. The X-ray photoelectron spectroscopy (XPS) analysis of SMG-Cr(VI) reveals the reduction of Cr(VI) to Cr(III), presumably due to the surface phenolic groups and unprotected ferrous ions on the SMG surface. The maximum adsorption capacity of SMG is 4.86, 3.26, and 6.00 mg/g for respectively Cr(VI), As(V), and Pb(II) at an initial concentration of 5.0 ppm. The addition of KNO₃ does not affect Cr(VI) adsorption efficiency; whereas Na₂SO₄ shows a decreasing trend on Cr(VI) adsorption. The SMG exhibits disinfection action (40 μg/L) toward E. coli bacteria with 100% killing efficacy and low toxicity (0.1 ng/nL) toward zebrafish without inducing any abnormalities. The SMG is reusable and successfully works on drinking water sources, suggesting that SMG is a preferred adsorbent for safe drinking water.