pH-sensitive and magnetically separable Fe/Cu bimetallic nanoparticles supported by graphene oxide (GO) for high-efficiency removal of tetracyclines.

Nanoscale zero-valent iron (nZVI) has been recognized as one of the most promising materials for the removal of a wide range of pharmaceuticals in water; however, aggregation and instability of nZVI in aqueous media reduces its efficacy. In this study, graphene oxide (GO) supported nZVI/copper bimetallic-nanoparticles (BNPs) were fabricated for high-efficiency removal of tetracyclines (TCs). In comparison to pure nZVI, the addition of Cu to the nano-adsorbents enhanced the efficacy of TC removal by 13%. The GO supporter mitigated the aggregation of BNPs and reduced the dissolution of metal nanoparticles, thereby demonstrating a higher working efficacy than Fe/Cu BNPs, even over five consecutive runs. At the optimal condition (pH 5-7, [TCs]: [Fe/Cu-GO] = 1:2.5 w/w), the Fe/Cu-GO nanocomposite showed near-complete (∼100%) TCs-removal within 15 min. The adsorption of TCs by Fe/Cu-GO fits the Freundlich model, with an adsorption capacity of 201.9 mg g-1. The Fe/Cu-GO nanocomposite showed pH-dependent assembly behavior to potentially recycle GO at a pH > 9 condition to generate new nanoparticles. The high removal efficiency of TCs, combining with high stability and easy separation performance in the aqueous environment, makes Fe/Cu-GO nanocomposites a promising material for treating latent antibiotics in water.