Ampicillin adsorption onto amine-functionalized magnetic graphene oxide: synthesis, characterization and removal mechanism

There are various chemical, physical and biological methods that have been applied to remove antibiotic residuals from aqueous environment. We investigated the removal of ampicillin (AMP) by a novel nanometer-size Fe3O4/graphene oxide/aminopropyltrimethoxysilane (FGOA). Based on the sol-gel method, the graphene oxide (GO) was first modified by aminopropyltrimethoxysilane (APTMS) to form GOA material containing both acidic and basic surface functional groups. The nanomagnetic iron oxide was then decorated to the GOA surface at various weight ratios by ultra-sonication in ethanol, resulting in different FGOA samples. The as-synthesized FGOA had single-layer structure and parallel array-like well-distributed Fe3O4. In laboratory-scale, the AMP treatment efficiency by FGOA with the ratio of Fe3O4: GOA as 1:5 ratio reached the highest value around 94% within 100 min and only lost 1% after five regeneration cycles. The maximum adsorption capacity of FGOA was 294mg g(-1), significantly much higher than the previously published materials applied to AMP uptake. Interestingly, the optimum pH of FGOA ranged extensively from 4 to 9, revealing high application potential to real wastewater without any pH adjustment. The reasonable mechanism might be mainly attributed to electrostatic attraction, hydrophilic, and pi-pi interaction.