Sammendrag
The present work focuses on detection of some heavy metals in waste and process water from metallurgical and mining industry. The main goal has been to find possible voltammetric techniques for online and in situ analyses of heavy metals like nickel, cobalt, zinc, cadmium, lead, thallium and mercury with use of non-toxic electrode materials. Among the most used techniques for detection of heavy metals are atomic absorption, ICP, ICP-MS, chromatography, and different electrochemical techniques. Voltammetry is inexpensive, fast and easy to carry out. Contrary to most other methods, it is possible to con-struct voltammetric apparatus for in situ online monitoring, with sensitivity for many impor-tant heavy metals in the low ppb range (0.5 - 1 ppb). The use of liquid mercury has been superior as electrode material in voltammetry for analytical purposes. This is mainly due to the high overvoltage to hydrogen, which enables the detection of heavy metals (like Zn) with high negative half wave potentials. Because of the toxicity of mercury and liquid diluted mercury compounds, the use of such compounds are increasingly restricted, and cannot be included in voltammetric devices for field applications. In the present work, environmentally friendly electrodes like dental amalgam, silver, silver-alloys, gold and glassy carbon electrodes have been used. Of special interest are dental amalgam and silver alloy electrodes that have been found to act similarly to a silver electrode, but have a high hydrogen overvoltage, allowing it to be used for in situ detection of zinc, cobalt, nickel and other metals. In this work, anodic as well as cathodic stripping voltammetry is used, with application of audible sound as an alternative to conventional stirring of the system. The possibilities of using the presented method for remote monitoring of heavy metals are demonstrated.
Vis fullstendig beskrivelse
