CD shopping page |
2011-Sustainable Industrial Processing Summit
|
| Editors: | Florian K |
| Publisher: | Flogen Star OUTREACH |
| Publication Year: | 2012 |
| Pages: | 764 pages |
| ISBN: | 978-0-9879917-5-1 |
| ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
Copper Removal From Cyanide Solutions By Three Different Methods
Omero Alonso1; Fabiola Nava-Alonso2; Alejandro Uribe-Salas2;1UNIVERSIDAD AUTóNOMA DE ZACATECAS, Zacatecas, Mexico; 2CINVESTAV, Ramos Arizpe, Mexico;
Type of Paper: Regular
Id Paper: 68
Topic: 14
Abstract:
The main method for the extraction of gold and silver used in Mexico and worldwide is cyanidation. In this process some specific minerals contains species of copper which are soluble in the cyanide solution, causing difficulties in the process (increase of reagent consumption, contamination of the final metal, increase of the water consumption due to the impossibility of recycling the solution back to the process, etc.). According to the above, in this work three methods are proposed in order to eliminate the copper cyanide complexes, namely: 1) the acid precipitation of CuCN, 2) the use of amines at alkaline pH to precipitate the copper-cyanide-amine complexes and 3) the solvent extraction of the copper-cyanide complexes with amines at alkaline pH. These processes were evaluated using synthetic solutions of composition similar to those found in cyanidation plants (197-739 mg/L copper and different cyanide/copper molar ratios). For the precipitation of copper by lowering the pH, it was found that 93 – 98% of the copper can be removed as CuCN (70 % copper, 10 µm average size particle) at pH 2.5 by filtration. When the CuCN solid is formed, more than 80% of cyanide contained in the copper-cyanide complexes is liberated as CN- (free cyanide), which can eventually be recycled back into the cyanidation process. The use of quaternary amines salts (hexadecyl trimethyl ammonium chloride, tallow trimethyl ammonium chloride, and ditallow hydrogenated dimethyl ammonium chloride) were evaluated in order to remove the copper-cyanide complexes by forming a precipitate of copper-cyanide-amine. The best efficiency of copper removal (more than 93%) was obtained using the amine tallow trimethyl ammonium chloride at pH of 12 and 12.32 g amine/g of copper.For the solvent extraction technique, tallow trimethyl cmmonium chloride, methyl trialkyl ammonium chloride and tricaprylylmethylammonium chloride were studied as extractants. The experimental results showed that it is possible to obtain a copper removal of 99% when using 0.033 mol/L of the extractant Adogen 464 (organic/aqueous volume ratio (O/A) = 1) in the range of pH of 9 – 11. Up to 99% of copper can be stripped from the organic solution after three contact times (5 min each) with 50 mL of sodium hydroxide 0.5 M (O/A =1).