Gold recovery from very dilute solutions from a mine in closing process: adsorption-desorption onto carbon materials

Abstract

"The aurocyanide complex recovery by precipitation with zinc decreases when gold concentration drops to < 20 μg L− 1. Therefore, a technology capable of recovering gold from very diluted solution is necessary. Adsorption and desorption experiments were carried out with real solutions in batch and in continuous processes to determine the gold adsorption capacity and rate onto two activated carbons (AC). The results showed that AC F400 and CSC removed 86 and 81 μg g− 1, respectively, at pH 11 and Ce of 10 μg L− 1 in about 4 h. Whereas desorption test by NaOH and CN− showed a gold recovery of up to 86%. These experiments were correlated to the textural and chemical properties of adsorbents and to the chemical composition of samples from a heap leach process. AC is a highly efficient and selective adsorbent for gold cyanide solutions when gold is present in very low concentration (< 12 μg L− 1)."