ELECTROCHEMICAL EXTRACTION OF COPPER, SILVER, AND GOLD FROM ENVIRONMENTAL WATER AND SOIL SAMPLES

摘要

This present work presents an extraction technique for copper, silver and gold, from water and soil environmental samples based on electrodeposition. The methodology involves potentiostatic electrodeposition of the metals from a large-volume sample at a large platinum gauze electrode. The deposited metal at the electrode was then stripped off in a small-volume by application of a high positive potential to the electrode. The optimal conditions were potentiostatic electrodeposition at extreme negative potential, and the stripping at an extreme potential in the allowed potential window of platinum in 0.5 M H_2SO_4 solution, -0.26 V and 1.2 V, respectively. The kinetics of deposition was found to follow a pseudo-first order, and the time of electrodeposition was found to be not greater than 120 min for 5.00 ppm concentrations. The method was evaluated and found to exhibit high precision (relative standard deviation <5% for most of the analyzed samples), high accuracy (recoveries between 95 and 103%, for most of the samples).