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Extraction of gold from cyanide or chloride media by Cyanex 923
Author(s) -
Alguacil Francisco J.,
Caravaca Concha,
Martínez Susana
Publication year - 1998
Publication title -
journal of chemical technology and biotechnology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.64
H-Index - 117
eISSN - 1097-4660
pISSN - 0268-2575
DOI - 10.1002/(sici)1097-4660(199808)72:4<339::aid-jctb912>3.0.co;2-l
Subject(s) - chemistry , cyanide , extraction (chemistry) , chloride , reagent , inorganic chemistry , phosphine oxide , ionic strength , protonation , stripping (fiber) , phosphine , ionic liquid , ionic bonding , aqueous two phase system , aqueous solution , chromatography , ion , organic chemistry , catalysis , materials science , composite material
A new phosphine oxide extractant, commercially known as Cyanex 923, has been studied in order to be applied in the recovery of gold from either cyanide or chloride aqueous media. Au(CN) 2 − is extracted by this reagent throughout the whole pH range. The presence of lithium salts in the media improves the extraction. The extraction mechanism proposed can be explained in terms of a solvating reaction, the species formed in the organic phase being the following: Li + Au(CN) 2 − 3(R 3 PO). The stripping can be performed by low ionic strength solutions such as dilute KCN solutions, and the reaction is enhanced by an increase in temperature. In chloride media, the extractant is able to extract gold (III) in the entire range of acid concentrations. The amount of extraction agent required, to achieve the same level of extraction, in this medium is much lower than in the cyanide media. The temperature has a negative effect on the extraction. Another difference observed between the two media, is that the presence of ionic salts in chloride media has no influence on the extraction, which may be attributed to the fact that the extracted species, HAuCl 4 , is a protonated instead of an ionic species. © 1998 SCI