Rapid, efficient and economic removal of organic dyes and heavy metals from wastewater by zinc-induced in-situ reduction and precipitation of graphene oxide

A graphene oxide (GO) reduction-based method for rapid, efficient and economic removal of organic dyes and heavy metal ions is reported. This method is performed by adding GO, Zn powder and NH4Cl into wastewater and stirring the solution at ambient conditions for a short period (< 10min). During this process, NH4Cl catalyzes the reduction of GO by Zn powder and causes the rapid in-situ adsorption and almost complete precipitation of pollutants by freshly reduced and nanoporous graphene oxide (rGO), therefore efficiently improving adsorption capacity and reducing adsorption time for water treatment. The adsorption capacities for organic dyes (methylene, congo red, lemon yellow) and heavy metal ions (Cd2+ and Pb2+) were 2.6, 7.6, 3.2, 8.4 and 17.9 g g(-1). The removal efficiencies are all above 98.46% and a maximum removal efficiency of 99.99% is obtained for Pb2+. Moreover, the byproducts of water treatment, i.e., rGO with excessive Zn powder and NH4Cl-containing water, can be further used in energy or agricultural fields. The present work establishes a new approach for the promising application of GO in the field of water treatment with high efficiency and good economic prospects. (C) 2018 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.