Determination of Sulfide in Mining Leachates Using Ion Chromatography

Sulfide is an effective reagent for the precipitation of copper and other base metals in metal winning control. For an effective and economic operation of the SART Process (sulfidisation, acidification, recycling, thickening), monitoring the sulfide concentration is essential. Normally sulfide is determined by acidifying the sample and collecting the H2S gas through a membrane in a buffer solution.
The collected gas is then determined spectrophotometrically at 230 nm or
after reaction with methylene blue at 600 nm. However, this offline method is very time-consuming and prone to interferences by other substances present. According to Metrohm coupling a gas diffusion cell to an IC with subsequent spectrophotometric detection is an online alternative yielding faster and more accurate results. The H2S gas derived from acidification of the sample enters a gas diffusion cell where it selectively diffuses through the hydrophobic membrane into a non- UV-absorbing acceptor solution. There it is deprotonated to the IC-compatible hydrogen sulfide anion (HS–).
Potentially interfering species cannot pass the membrane. Due to the selectivity of the gas diffusion cell and the direct ultraviolet absorption of the hydrogen sulfide anion at 230 to 250 mm (no post-column reagent is necessary), the overall analysis time is less than eight minutes.