Graphene-boron nitride composite aerogel: A high efficiency adsorbent for ciprofloxacin removal from water

Pharmaceuticals are emerging contaminants causing a lot of concerns and posing a threat to the aquatic environment and human health. In this study, graphene nanoplatelet/Boron Nitride composite aerogels (GNP/BNA) comprising BN ribbon fibers and multilayered graphene were prepared at a relatively low temperature of 1423 K for 3 h via a one-pot foam-gelcasting/nitridation route, and tested as an adsorbent for the removal of pharmaceutical ciprofloxacin (CIP) from its aqueous solutions. The density, porosity and compressive strength of the as-prepared GNP/BNA were respectively 28–34 mg/cm³, ~99% and 40–52 kPa. They exhibited a rapid adsorption rate and effective removal performance (99%) for CIP under the experimental conditions of C₀ = 10.5 mg/L, pH = 7 and 295 ± 3 K, even at a low adsorbent dose of 250 mg/L. The maximum adsorption capacity and normalized adsorption capacity of the composite foam were respectively 185 mg/g and 2.03 mg/m² at the CIP concentration of 10.5 mg/L. Based on the density functional theory calculations, the adsorption mechanism was clarified. BN and GNP exhibited evident selective adsorption for the functional groups of CIP. The –COO (–C[dbnd]O, the carbonyl group in the carboxyl group) and –CO were adsorbed stably on the BN nanosheets and GNP, respectively. The combined interactions of BN and GNP with the functional groups of CIP were responsible mainly for the excellent adsorption performance of the prepared composite foam. The as-prepared GNP/BNA composites with robust strength, good recyclability and high efficiency in the CIP removal, could be a promising candidate for efficient removal of a range of similar emerging contaminants.