Nanoesferas de carbono dopadas con nitrógeno empleadas en la detección y remoción de metales pesados en agua

Abstract

Electro-adsorption is an effective, fast, and relatively cheap technique used to remove contaminants from the water. The first step is the adsorption of a contaminant on the electrode´s surface, so, it is important that the electrode´s material presents good adsorption capacity and low resistivity to charge transfer. Carbon materials have been successfully used for both adsorption and electro-adsorption. Carbon nanospheres (CNS) are a relatively new nanometric form of carbon, which demonstrated excellent properties and have been proposed for different applications. It was shown that N-dopped CNS presents acceptable adsorption capacities for Pb(II). This work aimed to assess the possibility of using CNS in electro-adsorption and for electrochemical detection of Pb(II) and Cu(II). To study electro-adsorption, two electrode cell was used, using 4 different CNS materials as a cathode. Adsorption isotherms were acquired, and the kinetics of the process was assessed. For electrochemical detection square wave voltammetry and chronoamperometry were performed using a standard 3-electrode standard cell. The results showed that nitrogen doping did not augment the adsorption capacities of CNS, however, significantly increased the adsorption velocity. In the case of heavy metals detection, N doping decreases the detection limits of the electrochemical system, from 1.01 ppm to 0.21 ppm for Cu(II) and from 0.52 ppm to 0.18 ppm for Pb(II). In a conclusion, nitrogen doping of CNS improves the electrochemical properties of the materials making them a more suitable option to be applied in electrochemical systems for heavy metals electro-adsorption and detection.

Keywords: heavy metals; electro-adsorption; detection.