Use of CdS quantum-dots for mine water treatment

Abstract

A large amount of tailing water is generated from mines around the world every day. Tailing water requires adequate procedures to reduce its toxicity and, if feasible, to recover metallic ions present in its. This work describes a novel low cost, high performance photoelectrochemical system based on titanium dioxide photoanodes sensitized with CdS quantum dots that carry out Cu recovery and sulfur treatment of mine tailings simultaneously. Excitation of QDs by solar light promotes hole transfer to soluble sulfates and thiosulfates, while photogenerated electrons travel to a counter electrode where they reduce copper and facilitate its recovery. Under 1000 W·m-2 illumination, a maximum short-circuit current density of 7.4 A·m-2 was achieved meaning a copper recovery rate of 8.6 g m-1·h-1. At the same time the device provided the highest open circuit potential of 1.13 V and a maximum power density of 3.0 W·m-2, one order of magnitude higher than that provided by microbial fuel cells in wastewater decontamination systems.