Biofouling/acid resistant nanofiltration membranes interfacially polymerized with nickel-doped carbon dots for highly efficient removal and real-time monitoring of chromate in wastewater

Abstract

The high-efficiency removal and real-time monitoring of chromate (Cr(VI)) in wastewater remains an enormous challenge, and few studies considered the use of nanofiltration (NF) membranes for these purposes. Herein, Ni²⁺-doped carbon dots (Ni-CDs) with a highly negative charge, photosensitivity and acid resistance were successfully coupled onto a polyethersulfone substrate via interfacial polymerization (IP) as an active layer (termed as x%-Ni-CDs-M, and the mass percentages were x = 0, 0.25, 0.5, 0.75, and 1.0). Ni-CDs-Ms not only naturally inherited the acid restitance and nanozyme activities, but also greatly increased the hydrophilicity and negative charge property of the membrane surface, resulting in membranes with excellent photodynamic anti-bacterial, acid resistant, and divalent anions separation abilities. Most significantly, both the Ni-CDs and 0.25–1.0%-Ni-CDs-Ms can selectively detect Cr(VI) in wastewater via an inner filter effect. In particular, the sensitivity of the Ni-CDs-Ms-based sensor was nearly 9 times greater than that of the Ni-CDs-based chemosensor. 0.75%-Ni-CDs-M was therefore successfully applied for the highly efficient removal and real-time monitoring of Cr(VI) in wastewater. The proposed strategy is dedicated to real-time warning of abnormal changes in Cr(VI) level in wastewater, and provides the technical support for the prevention and handling of sudden Cr(VI) incidents in the environment.