Free cyanide analysis by silver nitrate titration with sulfide ion as interference

• Published in: Minerals engineering 2017-05, Vol.105, p.19-21
• Main Authors: Alonso-González, Omero, Jiménez-Velasco, César, Nava-Alonso, Fabiola, Alvarado-Hernández, Fransico, González-Anaya, Juan Antonio
• Format: Article
• Language: English
• Subjects: Cyanide chemical analysis; Free cyanide; Sulfide titration
• ISSN: 0892-6875; 1872-9444
• DOI: 10.1016/j.mineng.2017.01.001

•It is proposing the potentiometric titration technique using silver nitrate to determine both, sulfide and cyanide.•The endpoint by visually determination is not possible when sulfide ion is present in free cyanide solution.•The sequence of reaction mechanism of sulfide ion and free cyanide with silver relies on their Standard Gibbs Free Energy. In cyanidation process, the free cyanide concentration is the main variable that controls the efficiency of the process, and the plant operators determine it by silver nitrate titration. If sulfide ion is present in the solution the free cyanide concentration cannot be determined by titration as the silver added in the titration reacts with the sulfide ion to form a black solid (silver sulfide) that hinders the visual detection of the titration endpoint. This work proposes the potentiometric detection of the endpoint of the titration and demonstrates, thermodynamically and with analyses performed in synthetic solutions, that it is possible to determine both, sulfide and cyanide in the solution, even if the endpoint of the titration cannot be visually detected.