Single-Layered α-ZrP Nanosheet-Intercalated Graphene Oxide Membrane for Efficient Heavy-Metal–Organic Complex Removal
Wenbin Zhang, Daowen Wu, Mengyao Sun, Weiming Zhang, Bingcai Pan
Abstract
Heavy metals are present in the form of organic complexes in some industrial effluents, the stable structures of which enable them to be difficultly removed using traditional methods. Recently, graphene oxide (GO) membranes have attracted increasing attention in wastewater treatment; however, it remains challenging for GO membranes to efficiently remove heavy-metal–organic complexes due to their sub-1 nm sizes. Herein, a novel strategy is present to significantly enhance ion removal of GO membranes through the intercalation of as-prepared single-layered α-zirconium phosphate (α-ZrP) nanosheets. The X-ray diffraction and surface ζ potential measurements demonstrate that α-ZrP intercalation could decrease the wet interlayer distance (from ∼13.1 to ∼12.5 Å of 30 wt % α-ZrP added) of GO membranes and simultaneously enhance the surface ζ potential (from −35.4 ± 0.4 to −37.6 ± 0.9 mV at pH = 7). Using size exclusion and electrostatic repulsion, the obtained GO membranes could efficiently remove various heavy-metal complexes (e.g., >98.1% rejection toward Cu-EDTA2– and ∼5.8 L m–2 h–1 permeating flux) over a wide pH range (2–10), even at very low ion concentrations (e.g., 0.5 mg L–1). This single-layered α-ZrP nanosheet intercalation strategy for GO membranes opens new opportunities for the efficient removal of heavy-metal–organic complexes in wastewater.