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

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.

Removal of heavy metals and pollutants by membrane adsorption techniques

“…Numerous reports described the utilization of graphene and its composites as good adsorbents for the removal of dyes and heavy metal ions from aqueous solutions (Zhao et al 2011;Cong et al 2012;Huang et al 2011;Vilela et al 2016). The applications of graphene in environment are mainly the removal of pollutants in water.…”

Activated Carbon, Carbon Nanotubes and Graphene: Materials and Composites for Advanced Water Purification

“…Aerogels of graphene coated, chemically modified silica diatoms, impregnated with iron nanoparticles have shown a high affinity towards mercury ions, with an adsorption capacity of >500 mg/g [193]. The fabrication of GO-microbots, consisting of layers of GO, nickel and platinum have been used as environmental clean-up agents for the removal of lead from water, where depending on the GO-microbot dose, up to 95% removal of lead was observed [194]. In this case, the GO can capture lead from solution, while the platinum allows added hydrogen peroxide to be converted to H 2(g) and O 2(g) that act as propellants and the nickel facilitates magnetic control of the microbots.…”

Tubular microjets: Fabrication, factors affecting the motion and mechanism of propulsion

“…Recent reports showed application of the microjets for the removal of heavy metal [54,59] from the contaminated wastewater and long lasting reusable microjets [26] for the oxidation of organic pollutants in the water (Fig. 7).…”