Enhanced adsorption of nalidixic acid from aqueous solutions using molybdenum oxide-decorated graphene oxide

The persistence of antibiotic residues in aquatic environments poses significant ecological and public health challenges, necessitating the development of advanced remediation strategies. This study investigates the efficacy of graphene oxide (GO) and molybdenum oxide-decorated graphene oxide (GO/MoO3) adsorbents for the removal of nalidixic acid (NA), persistent antibiotic pollutant, from aqueous solutions. GO was synthesized via a modified Hummers' method, while MoO3 nanoparticles, produced by electric arc discharge, were anchored onto GO sheets. Comprehensive characterization using FTIR, XRD, BET, SEM, and EDX, confirmed the structural integrity and enhanced surface functionality of the GO/MoO3 composite. Under optimized conditions (pH 7.2; 40 mg L- 1 initial NA concentration; 1 mg adsorbent dosage; 2 h contact time), GO achieved 87% removal efficiency and 130 mg g- 1 adsorption capacity. In comparison, GO/MoO3 reached 91% removal efficiency and an adsorption capacity of 135 mg g- 1 at an initial NA concentration of 80 mg L- 1. Adsorption followed pseudo-second-order kinetics and the Freundlich isotherm, indicating multilayer chemisorption with the rate-limiting step governed by synergistic interactions between MoO3's redox-active sites and GO's oxygenated functional groups. These results highlight the potential of GO/MoO3 as a scalable and efficient adsorbent for mitigating pharmaceutical pollutants in water treatment systems.