A TiO2 Nanotube-Based Sensor for the Detection of Cyanide in Water

Abstract

Cyanide is an acutely toxic compound capable of reducing or eliminating oxygen utilization in living organisms on exposure. Natural and industrial processes contribute to the presence of cyanide in the environment. However, the concentrated nature of industrial-process-derived cyanide calls for greater attention. The ability to bind to other compounds makes cyanide capable of spreading to ground and surface waters more easily than other industrial contaminants. Cyanide concentrations in waste waters need monitoring to ensure that they are within permissible levels. Furthermore, cyanide is an essential reagent in some processes, and thus tracking of cyanide concentrations in the process line is essential. Real-time monitoring of cyanide concentrations calls for a robust and quick method for detection of cyanide concentrations in water. As such, this work focuses on the application of titanium dioxide (TiO2) nanotubes for the sensitive and selective electrochemical detection of cyanide in water. The TiO2 nanotubes were modified by the addition of iron (Fe) and sulfur (S) to the nanotube structures. Characterization of the prepared sensing electrode was carried out using X-ray diffraction and electron microscopy. Electrochemical sensing of the cyanide in water was performed using a three-electrode system with an Fe-S-TiO2 working electrode. Cyclic voltammetry was used to establish the sensing of the cyanide species as well as the response to cyanide concentration in water. Chronoamperometry was used to test the effect of interfering species as well as the sensor sensitivity, with an observed current response to a 0.1μM change in cyanide concentration. The sensor response indicated that an Fe-S-TiO2 sensing electrode could effectively be used for the sensing of cyanide concentrations lower than the recommended limits in water, and with good sensing electrode reusability.