The natural occurrence of platinum group metals, ruthenium, rhodium, and palladium as well as osmium, iridium and platinum, is very rare; making them extremely valuable. Even a tiny difference in the already very-low platinum metal concentrations in a raw material can determine whether or not extraction is worthwhile.
This is true for all forms of production, be it mining for metal ores, as a byproduct during nickel refining, recycling of electronic scrap or material recovery in spoil piles leftover from earlier platinum ore mining. The SPECTRO MS inductively coupled plasma mass spectrometer (ICP-MS) can establish the contents of platinum metals with a high precision and sensitivity. Even determination in the range of a few micrograms per kilogram is possible. SPECTRO demonstrates the instrument’s potential from April 16 to 19 at the 23rd International Mining Congress, IMCET, in Antalya, Turkey.
The high sensitivity and precision have been made possible by internal standardization of the instrument. With the conventional method for the solid material analysis of platinum metals, the sample is first mixed with nickel sulfate. The mixture is then processed to form a fused bead, whereby the platinum metals accumulate in the nickel sulfate, and the rest of the sample can be removed as slag. In the next step, the bead is subjected to a laser impulse. Using this laser ablation, a portion of the material at the sample surface is transformed into a plasma that can be evaluated with an analytical instrument.
“The problem is that the amount of sample that passes into the plasma is strongly dependent on the sample matrix,” explains Willi Barger, specialist for ICP mass spectrometry at SPECTRO. “If a large portion of the sample substance passes into the plasma, then the instrument measures high concentrations. But if only a small amount is removed, then the contents are low. To minimize the resulting fuzziness, the SPECTRO MS uses nickel, the main component in the bead, as an internal calibration standard.”
Because the SPECTRO MS is the first and only ICP mass spectrometer to offer fully simultaneous measurement of the complete organically relevant mass range from 6Li to 238U over a very wide dynamic range, the instrument is able to determine nickel at extremely high concentrations. At the same time, the instrument is able to detect the platinum metals group elements at trace levels.
“The results achievable with this simultaneous measurement are much more conventionally true and accurate than the results from sequential measurements,” adds Barger.
Sustainability and Profitability
ICP mass spectrometry form of analysis opens new economic possibilities for platinum metal extraction. With it exact assessment as to whether or not it is worthwhile to develop a given deposit can be formed. Incisive predictions dealing with the achievable amounts during the extraction of platinum metals as secondary products during non-ferrous metals production and the recycling of electronic scrap also can be made. A special economic advantage can be gained by combing again through mine tailings left over from earlier platinum ore mining. Large amounts of blasted stone were previously stored with the tailings, because with the metallurgical methods at that time, it was not economically feasible or the extraction was simply not possible. Current processing methods provide new possibilities for handling even deposits with low platinum metal concentrations. Mine tailings already are located above ground, saving mining companies from the cost intensive conveyance of ore from underground, thus improving the profitability.