Continuous Laboratory Gold Solvent Extraction from Cyanide Solutions using LIX 79 Reagent

Abstract

Continuous laboratory solvent extraction of gold from cyanide solutions has been investigated by using LIX 79 guanidine-based extractant. Different variables that affected the extraction included aqueous pH, extractant concentration and modifier concentration. Extraction isotherms of the aurocyanide complex with respect to the other cyanoanions were compared, and the following order of selectivity was observed: Au > Ag > Cu > Zn > Fe. According to the pH isotherms, aurocyanide can be extracted in alkaline media, and a better separation with respect to other cyano anions was obtained in the pH range 10.5-11.2. From the McCabeThiele diagrams, better recovery was observed when using LIX 79 and tridecanol at 10 vol.-%. Stripping gold from the loaded organic was carried out at pH > 12 by using NaOH and NaCN solutions. The pilot plant tests indicate that a twostage extraction followed by one strip step are more than adequate to obtain an overall process efficiency of 92 %. However, for those cases where copper is present significantly, a copper wash stage is recommended before gold stripping. In this case, stripping of copper is accomplished at a pH 10.8, whereas the gold stripping was done at a pH of 12.0.

Solvent extraction of gold using ionic liquid based process

“…Moreover, several extractants are used for gold extraction in commercial operation such as dibutyl carbitol (DBC), MIBK (methyl isobutyl ketone) and DIBK (diisobutyl ketone). Some companies developed commercial amine-derivatives as the extracting agents which was claimed to have better separation performance, such as Lix (LIX 84-I was used for nickel extraction, LIX 63 was used for copper extraction) 49,50 , Hostarex 51 and Cyanex 52 . Those were reported to give significant improvements in term of kinetic to reach equilibrium, organic phase diluent and the concentrations of metal and the extractant 52 .…”

New Technology for Recovery of Gold and Silver by Pressure Cyanidation Leaching and Electrocoagulation

“…Only recently, in the past years, has the carbon adsorption process become popular for recovering gold from large volumes of low grade pregnant leach solutions that contain mainly gold. Other processes, Ion-Exchange Resins and Solvent Extraction, have recently been reviewed as an alternative for gold and silver recovery from alkaline cyanide solutions, (Aguayo et al, 2007). Commercially available resins were unable to compete with activated carbon due to poor selectivity, mechanical breakdown of the beads and the requirement for complex elution, generation of HCN and regeneration process.…”

Recovery of Silver from Cyanide Solutions Using Electrochemical Process Like Alternative for Merrill-Crowe Process

“…Modern hy-drometallurgy technology of precious metals is based on the application of cyanide leaching for the dissolution of silver. Silver cyanidation has been reported to involve the chemical reactions shown in Equations (1) and (2)…”

“…Lime or sodium hydroxide (caustic) is added to keep the system at an alkaline pH of 10 −11 . This protective alkalinity is required to counteract the generation of acid during cyanidation, thereby preventing cyanide degradation and the formation of the deadly HCN gas [2].…”