Graphene-Based Microbots for Toxic Heavy Metal Removal and Recovery from Water

TLDR

Heavy metal contamination in water poses serious public health risks, and nanotechnology is developing nanosystems for rapid, efficient pollutant removal. This study introduces graphene oxide‑based microbots as self‑propelled agents for capturing, transporting, and removing lead from water while enabling its recovery for recycling. The microbots comprise multilayer graphene oxide, nickel, and platinum: the outer graphene oxide layer adsorbs lead, the inner platinum layer catalyzes hydrogen peroxide decomposition for propulsion, and the nickel layer provides magnetic steering. Mobile GOx‑microbots reduce lead from 1000 ppb to below 50 ppb in 60 min—ten times more efficient than non‑motile counterparts—and can be regenerated after chemical detachment, with magnetic control demonstrated in a microfluidic proof‑of‑concept.

Abstract

Heavy metal contamination in water is a serious risk to the public health and other life forms on earth. Current research in nanotechnology is developing new nanosystems and nanomaterials for the fast and efficient removal of pollutants and heavy metals from water. Here, we report graphene oxide-based microbots (GOx-microbots) as active self-propelled systems for the capture, transfer, and removal of a heavy metal (i.e., lead) and its subsequent recovery for recycling purposes. Microbots' structure consists of nanosized multilayers of graphene oxide, nickel, and platinum, providing different functionalities. The outer layer of graphene oxide captures lead on the surface, and the inner layer of platinum functions as the engine decomposing hydrogen peroxide fuel for self-propulsion, while the middle layer of nickel enables external magnetic control of the microbots. Mobile GOx-microbots remove lead 10 times more efficiently than nonmotile GOx-microbots, cleaning water from 1000 ppb down to below 50 ppb in 60 min. Furthermore, after chemical detachment of lead from the surface of GOx-microbots, the microbots can be reused. Finally, we demonstrate the magnetic control of the GOx-microbots inside a microfluidic system as a proof-of-concept for automatic microbots-based system to remove and recover heavy metals.