Recyclable Ag-decorated highly carbonaceous magnetic nanocomposites for the removal of organic pollutants.

Here, we report a novel fabrication of a magnetic carbon nanotube-reduced graphene oxide-silver nanocomposite for the adsorption and simultaneous catalytic reduction of two environmental pollutants. Fe3O4 nanoparticles were grown and anchored onto the multi-walled carbon nanotube (CNT) first to generate magnetic CNT (MCNT), which was further coated with polydopamine to enhance the stability of the Fe3O4 particles and introduce new functionalities on the surface. Hydrothermal treatment of the polydopamine-coated MCNT (PD-MCNT) with graphene oxide (GO) produced a highly carbonaceous reduced GO-PD-MCNT (rGO-PD-MCNT), which by itself exhibited very high adsorption capability. The catalytic property was integrated by depositing silver nanoparticles (AgNPs) on the rGO-PD-MCNT by reducing Ag(I) ions. High catalytic efficacy besides fast and efficient adsorption of the as-synthesized nanocomposites was demonstrated at variable pH during the removal of a toxic model dye, methylene blue (MB), and an aromatic nitro compound, 4-nitrophenol (4-NP). The nanocomposites were found to be magnetically separable, easily regenerable through desorption using water and ethanol, and thus highly recyclable (more than 15 cycles). The rare combination of all these properties in a single scaffold makes this nanocomposite potentially useful in a wide range of engineering and environmental applications.