Suppression of arsenopyrite oxidation by microencapsulation using ferric-catecholate complexes and phosphate

Mineral processing, pyro- and hydrometallurgical processes of auriferous sulfide ores porphyry copper deposits (PCDs) generate arsenopyrite-rich wastes. These wastes are disposed into the tailings storage facilities (TSF) in which toxic arsenic (As) is leached out acid mine drainage (AMD) generated due to oxidation arsenopyrite (FeAsS). To suppress oxidation, this study investigated passivation by forming ferric phosphate (FePO4) coating on its surface using ferric-catecholate complexes simultaneously. Ferric iron (Fe3+) catechol form three types (mono-, bis-, triscatecholate complexes) depending pH, but mono-catecholate complex (i.e.,[Fe(cat)]+) became unstable presence because chemical affinity Fe3+—PO43– most probably stronger than that Fe3+—catechol [Fe(cat)]+. When two or more molecules were coordinated with Fe3+ (i.e., [Fe(cat)2]– [Fe(cat)3]3–), however, these stable irrespective phosphate. The treatment could formation FePO4 coating, evidenced SEM-EDX XPS analyses. mechanism was confirmed linear sweep voltammetry (LSV): (1) oxidatively decomposed (2) resultant product [Fe(cat)]+) reacts phosphate, resulting FePO4.