Analysis of the Behavior of As and Pb during the Pretreatments Applied to a Jarosite Residue for the Recovery of Gold and Silver

Abstract

The recovery of valuable metals from jarosites is a topic of great relevance regarding the implementation of the circular economy; however, these materials also contain metals such as arsenic and lead, which are harmful to health and the environment. Considering these factors, it is important to monitor these metals at each stage of treatment used to recover the valuable metals. In the present work, the behavior of As and Pb was assessed during the pretreatment conducted on a jarositic residue using direct zinc leaching (DLR), as well as leaching in cyanide and cyanide media with glycine. It was found that when no DLR pretreatment was performed, As and Pb naturally dissolved in the cyanide-leaching medium at concentrations of 34.08 mg/L and 99.12 mg/L, respectively. When an alkaline treatment was conducted on the residue (DLR-AH), it was found that there was no presence of As and Pb in the cyanidation solution, while in the case of the cyanide solution with glycine, we observed 83.35 mg/L of As and 213.63 mg/L of Pb. During the oxidizing alkaline hydrothermal treatment (DLR-AHO), 27.5 mg/L of As and 106.78 mg/L of Pb were detected in the cyanide solution. In the cyanide solution with glycine, there was less dissolution of As and Pb (11.68 and 66.75 mg/L), respectively. Finally, when desulfurization of the DLR was conducted prior to the DLR-AHO treatment, the dissolution of As and Pb increased due to the elemental sulfur covering the arsenopyrite and galena particles, so that, when removed, these were more susceptible to pretreatment and cyanidation.

Jarosites: Structure, Formation, Leaching, Environmental, and Applications

“…In their study, Picazo-Rodríguez et al [10] examined the effect of different pretreatment methods: (1) alkaline hydrothermal pretreatment (1 M NaOH), (2) alkaline-oxidizing pretreatment (1 M NaOH/0.1 M Na 2 S 2 O 8 ), and (3) alkaline-oxidizing (1 M NaOH/0.1 M Na 2 S 2 O 8 0.1) pretreatment prior to desulfurization of the residue. After pretreatment, the concentrations of Pb, As, Fe, and S were analyzed in the pretreatment liquid and in those of cyanidation (CN − 0.06 M) or cyanidation with glycine (CN − 0.06 M, Glycine 0.06 M, 1% H 2 O 2 ) liquids.…”

“…In general [3], numerous authors have studied different aspects of jarosites: their mineralogy, structure, formation in natural environments or through synthesis, immobilization, stability, reactivity in acid and alkaline media, and applications [9][10][11][12]. Jarosites are also formed during leaching or bioleaching processes, for example, over chalcopyrite [13].…”