Rapid and highly selective removal of lead from water using graphene oxide-hydrated manganese oxide nanocomposites

To overcome the limits of graphene oxide (GO) as a novel sorbent for heavy metal removal (e.g., low sorption selectivity and difficulty in solid-liquid separation), a nanocomposite (HMO@GO) with excellent settling ability (<2 min) was fabricated through in situ growing nanosized hydrated manganese oxide (HMO) (10.8 +/- 4.1 nm) on GO. As a graphene-based adsorbent, HMO@GO exhibited fast sorption kinetics (<20 min). Meanwhile, the introduced HMO endowed HMO@GO with outstanding sorption selectivity and capacity toward Pb(II) (>500 mg g(-1)) in the presence of high-level competing Ca(II). Cyclic sorption batches showed that 1 kg HMO@GO can treat at least 22 m(3) Pb(II)-laden synthetic industrial drainage (5 mg L-1 Pb(II)) and 40 m(3) drinking water (0.5 mg L-1 Pb(II)) to their corresponding limits (0.1 mg L-1 for wastewater and 10 mu g L-1 for drinking water) enforced in China. Additionally, the exhausted HMO@GO can be effectively regenerated using 0.3 M HCI for repeated uses. The eminent performance of HMO@GO was attributed to its specific structure, that is, the abundant oxygen-containing groups on GO mediated the growth of highly dispersed HMO that preferably sequestrated Pb(II) through specific interaction, and the host GO offered the preconcentration of Pb(II) for enhanced sequestration through the Donnan membrane effect. (C) 2016 Elsevier B.V. All rights reserved.