Establecimiento de los parámetros de una técnica electroanalítica que permita cuantificar la concentración de arsénico(III) en aguas asociadas con la actividad minera

Abstract

Small-scale gold mining is an activity that in Colombia is frequently carried out illegally and without control, which triggers a large problem of environmental contamination and public health. Usually, to extract gold from rocks, cyanidation processes are carried out, which generally contain sulphide minerals such as pyrite (FeS_2) and arsenopyrite (FeAsS), which release leachates with amounts of As(III) and Fe(III) into the environment, causing high levels of water pollution. To contribute to meeting the goals of the 2030 United Nations Agenda to guarantee clean water and sanitation, the establishment of an electrochemical technique is proposed as a viable alternative to the detection and monitoring of arsenic. The strategy proposed here consists of: (a) performing a series of modifications to a gold electrode with nano and micro copper and silver particles, (b) qualitatively determining which modified electrode material allows a better determination of As( III) in a model synthetic water that simulates wastewater from small-scale gold mining, this through the evaluation of the electrochemical behavior of As(III), and finally (c) establish an electroanalytical technique to quantify As(III) on the selected electrode material. The best results for the determination of As(III) were obtained for a gold electrode modified with copper nanoparticles, which were deposited at a potential of 0.1 V vs Ag/AgCl (3 M KCl) at a time of 500 ms. The arsenic pre-concentration time that leads to the best results was 120 s, resulting in a calibration curve with a determination coefficient of 0.997, a detection limit of 0.356 ppm and a quantification limit of 1.188 ppm.