Methylphenidate adsorption onto graphene derivatives: theory and experiment

Nowadays environmental pollution is one of the major problems caused by unrestrained human activity, associated with emerging micropollutants, such as pharmaceutical compounds. Thus, this work aimed to analyse the methylphenidate (MPH) drug removal from aqueous solutions, using graphene derivatives, graphene oxide (GO) and reduced graphene oxide (rGO), as adsorbent materials, combining experimental and theoretical methods. The ab initio theoretical study is based on density functional theory and presents the structural and electronic properties of the nanoadsorbents and the MPH. The simulations show a physisorption regime between methylphenidate and the nanoadsorbents. The adsorbents were characterized by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The experimental analysis was carried out in batch conditions with methylphenidate solutions (20 mg L-1) in a protocol employing GO/rGO (0.7 g L-1), performing equilibrium (Langmuir and Freundlich models) and kinetic (pseudo-first order and pseudo second-order models) adsorption studies. From the kinetic point of view, experimental data was represented satisfactorily by the pseudo first-order model. The Freundlich model showed better adjustment for the MPH adsorption, with the maximum values for the adsorption capacities of 6.53 mg g(-1) and 8.35 mg g(-1) for GO and rGO, respectively. In this way, the correlating theoretical and experimental studies have indicated a coherence about the physisorption regime, showing these nanomaterials as an important alternative for the removal of methylphenidate and furnishing possibilities of further studies aiming at the removal of different drug contaminants from wastewater.

Automated summary

This study focused on the removal of the drug methylphenidate from aqueous solutions using graphene derivatives as adsorbent materials. Theoretical and experimental methods were combined to analyze the adsorption process, showing that graphene oxide (GO) and reduced graphene oxide (rGO) have high adsorption capacities for methylphenidate, providing a promising alternative for the removal of drug contaminants from wastewater.