Measurement of dissolved H_2S, (hydrogen sulphide), in difficult applications such as tanneries, circuit board waste and waste water treatment

摘要

Measurement and control of H_2S levels after pre-treatment is vital because the presence of even low levels of H_2S will have a detrimental impact on subsequent biological treatment processes. Measurement at the discharge point is important to ensure compliance with legal requirements. PCB manufacture. Hydrogen Sulphide gas is used to treat exhaust etching solutions from PCB industries, containing high level of Copper under Ammoniacal complex form. The gas is used to precipitate Copper Sulphide. The sulphide level must be always in a small excess (few ppm, usually 5 - 10) in order to be sure that all Copper is precipitated. Measurement of dissolved sulphide would allow control of the process. The waste water from this process also needs to be processed to remove dissolved sulphides.