Dispersion-Free Solvent Extraction and Stripping of Gold Cyanide with LIX79 Using Hollow Fiber Contactors: Optimization and Modeling

Abstract

This paper reports experimental data on hollow fiber dispersion-free membrane extraction (DFSX) of gold(I) from alkaline cyanide media using microporous hydrophobic polypropylene hollow fiber contactor. A recently developed new solvent extraction reagent, namely, LIX79 (Henkel Corporation), was employed as an extractant. The DFSX operation was carried out with 12% LIX79 in n-heptane by passing alkaline feed containing gold through the tube side and organic extractant through the shell side. Extraction studies were performed under different hydrodynamic conditions and mass correlations for the tube and shell side were presented for cocurrent and countercurrent flow conditions. A model is presented that identifies the different rate-controlling steps under various chemical and hydrodynamic experimental conditions in feed, organic, and membrane phases. The mass-transfer resistance resulting from a chemical extraction reaction at the surface was observed to be dominant during the entire extraction process. The validity of this model was evaluated with experimental data and found to tie in well with theoretical values. It was possible to separate and concentrate Au(I) (up to 400 mg/L) in the presence of other metal cyanide salts such as Fe(II), Cu(I), Ni(II), Ag(I), and Zn(II) (NaCN = 1000 mg/L) by employing this technique. The stripping of gold from LIX79 was accomplished efficiently by using NaOH, which flowed through the tube side (11.11 cm3/s) and the organic was passed through the shell side at (6.94 cm3/s).