Electrochemical and Spectroscopic Analysis of Arsenopyrite (FeAsS) Oxidation under Calcareous Soil Conditions

摘要

Electrochemical and spectroscopic studies of arsenopyrite samples were carried out under calcareous soil weathering conditions. Electrochemical study consisted of cyclic voltammetry using carbon paste electrodes with embedded FeAsS particles (CPEFeAsS) in order to evaluate the oxidation process and the effect of the oxidation products on global reactivity. Leaching procedure consisted of mineral alteration by humid and aeration stages under calcareous conditions. Leached samples were characterized by cyclic voltammetry, SEM-EDS, Raman spectroscopy and XPS. Chemical analysis of leachates provided understanding of the extent of the mineral weathering process. The results indicated the formation of non-stoichiometric layers with variable composition (NL, e.g., Fe_(1-x)As_(1-y)S) at all stages and the formation of α,β,δ-FeOOH compounds. Arsenic species were retained in this phases. A cyclic dissolution process of arsenopyrite was identified that seems to be influenced by NL composition. On the experimental basis, a dissolution process of arsenopyrite under calcareous soil weathering conditions is proposed.