Gangue mineral dissolution and jarosite formation in copper solution mining

In Situ Recovery of Copper: Identifying Mineralogical Controls via Model-Based Analysis of Multistage Column Leach Experiments

“…This suggests either the existence of other processes consuming Na during the experiments or a systematic underestimation of jarosite precipitation. Nevertheless, the experimental results were consistent with a higher stability of K-jarosite compared with Na-jarosite . The total mass of jarosite (as estimated from the model) that precipitated during the experiments was <2–4 wt % and exclusively precipitated next to the inlet.…”

“…60 Importantly, it has also been found previously under Cu-ISR conditions. 16 Corroborating the hypothesis of jarosite precipitation is (i) that the influent solution was oversaturated with respect to jarosite; (ii) site water samples (SGW1 and SGW2) also showed precipitates that formed during storage, which were identified as jarosite and gypsum by XRD (data not shown); and (iii) additional samples collected from the site, but not used in this study, were found to have jarosite. As can be seen in Figure 8, model simulation results for all columns showed an improved match with observed Na effluent concentrations, especially for stages 3 and 4, if jarosite precipitation is allowed to proceed.…”

“…Generally, those studies have focused on constructing data-validated models that quantified the rates of copper recovery, , typically coupling vadose zone transport processes with lumped formulations of the leaching kinetics without considering the competitive effects from gangue minerals and secondary mineral transformation processes. However, as previously shown for the case of uranium ISR, processes such as (i) the secondary precipitation of Fe hydroxides from dissolved cations, (ii) the dissolution of rock-forming minerals, − (iii) the oxidant-acid consumption from gangue minerals, , and (iv) metal adsorption can all substantially impact recovery.…”

“…The release of trace metals that occurred due to pyrite oxidation was considered by employing a modified pyrite stoichiometry that incorporated traces of Mn, Ni, and Co: Fe ( 1 − x ) Mn α Ni β Co γ S 2 + 2 H + + 2 e − → false( 1 − italicx false) Fe 2 + + α Mn 2 + + β Ni 2 + + γ Co 2 + + 2 HS − x = α + β + γ where α, β, and γ are values between 0 and 1 denoting the molar ratios of Mn, Ni, and Co, respectively. Furthermore, jarosite was included in the reaction network as its precipitation is commonly observed during both heap leaching and ISR, especially in environments with elevated sulfate concentrations. The applied generic rate expression for jarosite was similar to that for chalcanthite.…”

“…Nevertheless, the experimental results were consistent with a higher stability of K-jarosite compared with Na-jarosite. 16 The total mass of jarosite (as estimated from the model) that precipitated during the experiments was <2−4 wt % and exclusively precipitated next to the inlet. This, in combination with the amorphous morphology of these precipitates, implies that recognizing any jarosite phase in the postleaching solid samples would have been difficult with any characterization technique, and indeed, jarosite was not recognized during the examination of the leached selected subsamples with SEM-EDS.…”