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PITTCON 08 Oral Session
Determination of sulfide in mining leachates
Session Number 2670-10
Abstract
Sulfide is an effective reagent for precipitation of copper and base metals for both metal winning and environmental control. For an effective and economic operation of the SART Process (sufidization, acidification, recycling, thickening) a control of the sulfide concentration is essential.
2 Cu(CN)32- + S2 --> Cu2S + 6 CN
Normally sulfide is determined by acidifying the sample and collecting the H2S gas through a membrane in a buffer solution. The collected dissolved gas is then determined spectrophotometrically at 230 nm or after the reaction with methylene blue at 600 nm. The method is very time-consuming and prone to interferences by other substances present. Another problem is the fact that at a pH below 10, sulfide is very unstable; therefore, a direct measurement at the SART process is preferable to offline measurements in the laboratory. As a further advantage, the online measurement provides faster and more accurate results. This paper presents a simple direct-injection method for the determination of sulfide in goldmine leachates. Using a carbonate eluent, sulfide is separated from the other ions on a Metrosep A Supp 1 column and detected at 220 nm using a UV/VIS detector. The external calibration curve is linear in the range from 1 – 10 ppm. Spike recovery rates for the addition of 2, 4, 8 and 10 ppm sulfide to an artificial matrix solution ranged from 96 – 112%. By means of the presented method further sulfur species, such as sulfite, sulfate or thiocyanate, can reliably be detected.
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