A new online detection method for arsenic minerals in process streams

Arsenic is a significant inorganic pollutant and is a penalty element in base metal concentrates. There is both an economic and environmental need to control the level of arsenic in processing streams. For example, there may be benefit in real time monitoring of mineral species that contain arsenic in flotation cells to aid control of arsenic removal. The mineral speciation of tailing streams may also be a useful indicator of plant performance. CSIRO is developing on-line instrumentation for mineral phase analysis based on magnetic resonance spectroscopy. The method used is non-contact, suitable for measurement on conveyor ore streams or slurries, and has high resolution and low detection limits for selected minerals. The method is highly specific, as each target has a response unaffected by other mineral resonances. This technique is suited to the detection of arsenic mineral phases due to the high sensitivity associated with the arsenic nuclei, and other resonant nuclei contained in the phase, such as copper. Preliminary results are presented for selected arsenic minerals including orpiment, metallic arsenic and tennantite. It is demonstrated that detection limits below 0.1 weight per cent, measured online within several minutes, are feasible for certain arsenic minerals. Lower detection limits can be achieved with increased measurement time. Prospects for on-line detection of minerals containing bismuth or antimony are also discussed.