Formation of surface protective coatings on arsenopyrite using Al-catecholate complex and its mode of inhibition of arsenopyrite oxidation

Abstract

Arsenopyrite is the most common arsenic-bearing sulfide mineral in nature. It is readily oxidized and releases toxic arsenic (As) into the environment when exposed to atmospheric conditions via anthropogenic activities like mining, mineral processing, extractive metallurgy, and underground space developments. Carrier-microencapsulation (CME) is a technique that uses metal(loid)-organic complexes to selectively form protective coatings on the surfaces of sulfide minerals. In this study, CME using Al-catecholate complexes (i.e., Al-based CME) was investigated to suppress the oxidation of arsenopyrite. Aluminum(III) and catechol form three complex species depending on the pH and among them, [Al(cat)]+ was the most effective in suppressing arsenopyrite oxidation. Its suppressive effect was improved as [Al(cat)]+ concentration increased due most likely to the formation of a more extensive surface protective coating at higher concentrations. Surface characterization of leaching residues using SEM-EDX and XPS indicates that CME-treated arsenopyrite was covered with bayerite (γ-Al(OH)3). The results of electrochemical studies showed that the surface protective coatings suppressed both anodic and cathodic half-cell reactions of arsenopyrite oxidation.

Carrier-microencapsulation of arsenopyrite using Al-catecholate complex: nature of oxidation products, effects on anodic and cathodic reactions, and coating stability under simulated weathering conditions

“…The predominant As species found in contaminated waters and acid mine drainage (AMD) are arsenite (As 3þ ) and arsenate (As 5þ ), both of which are highly soluble and mobile over a wide range of pH and Eh conditions (Park et al, 2018a(Park et al, , 2019aTabelin et al, 2010Tabelin et al, , 2012aTabelin et al, , b, 2014aTabelin et al, , 2017a. Arsenic is a toxic metalloid known to cause numerous diseases like hyperpigmentation, keratosis, anemia, and neuropathy as well as the increased risk of developing several types of cancers even at minute amounts (i.e., μg/L levels) when ingested continuously for prolonged periods of time (i.e., chronic poisoning) (Duker et al, 2005;Mohan and Pittman, 2007;Park et al, 2019b;Seno et al, 2019;Tabelin et al, 2018). Like pyrite (FeS 2 ), the oxidation of arsenopyrite also generates AMD.…”