Green-functionalized carbon nanotubes as adsorbents for the removal of emerging contaminants from aqueous media

Abstract

Emerging pollutants such as pharmaceuticals and endocrine disruptors are found in sewage systems and wastewater treatment plants in low concentrations. After being discharged into the river, these pollutants can contaminate surface and groundwater, causing harms to human health and to the environment. Due to this problem, this study aimed to produce functionalized carbon nanotubes (CNTs) impregnated with iron (Fe) nanoparticles produced from green synthesis for the adsorption of five pharmaceuticals and an endocrine disruptor: ciprofloxacin, diclofenac sodium, losartan, ofloxacin and propranolol, and bisphenol-A. To demonstrate the efficiency of the green synthesis, Fourier transforms infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analyses were performed. Affinity adsorption tests, molecular simulation via density functional theory, and the construction of an artificial neural network (ANN) were performed to evaluate the adsorbents performance. Characterization analyses indicated that the synthesis process of the green route was successful in the production of solids. The green functionalization of nanotubes previously composed with hydroxyl and carboxyl groups showed the best results in the adsorption tests (>80%), except for bisphenol A, which presented better results with the nanotube constituted by hydroxyl group (100%). Bisphenol A and propranolol molecules proved to be less reactive than the others and the constructed ANN was able to satisfactorily predict the adsorption capacity based on independent variables. Therefore, it can be concluded that carbon nanotubes impregnated with iron nanoparticles prepared by green synthesis are promising for the removal of pharmaceuticals and endocrine disruptors from aqueous media.