Abstract
Arsenopyrite (FeAsS) is the most common primary arsenic-sulfide mineral in nature, and its oxidation causes the release of toxic arsenic (As). To mitigate these problems, carrier-microencapsulation (CME), a technique that passivates sulfide minerals by covering their surfaces with a protective coating, has been developed. In the previous study of authors on CME, Al-catecholate complex significantly suppressed arsenopyrite oxidation via electron donating effects of the complex and the formation of an Al-oxyhydroxide coating. For the application of this technique to real tailings, however, further study should be carried out to elucidate long-term effectiveness of the coating to suppress arsenopyrite oxidation. This study investigates the stability of the coating formed on arsenopyrite by Al-based CME using weathering tests. The Al-oxyhydroxide coating suppressed arsenopyrite oxidation until about 50 days of the experiment, but after this, the amounts of oxidation products like dissolved S and As increased due to the gradual dissolution of the coating with time as a result of the low pH of leachate. This suggests that co-disposal of Al-based CME-treated arsenopyrite with minerals that have appropriate neutralization potentials, so that the pH is maintained at around 5 to 8 where Al-oxyhydroxide is stable.
Highlights
Mining, mineral processing, and extractive metallurgy generate huge amounts of tailings containing sulfide minerals like pyrite (FeS2) and arsenopyrite (FeAsS), which are discharged into tailings ponds or dams
Sulfide minerals in the tailings are readily oxidized when exposed to oxygen (O2) and water, resulting in the formation of acid mine drainage (AMD), one of the most undesirable consequences of mining activities due to its serious negative impacts to the surrounding environment [1]
diffuse reflectance infrared Fourier transform (DRIFT) spectra of arsenopyrite leached in control and Alcatecholate complex solution [7]
Summary
Mineral processing, and extractive metallurgy generate huge amounts of tailings containing sulfide minerals like pyrite (FeS2) and arsenopyrite (FeAsS), which are discharged into tailings ponds or dams. Arsenopyrite is notorious because its dissolution generates acidity and releases arsenic (As), a toxic element known to increase the risks of developing numerous diseases like hyperpigmentation, keratosis, anemia, neuropathy, and several types of cancers even at minute amounts [2, 3]. Carrier-microencapsulation (CME) has been developed by the authors to prevent the generation of AMD. This technique has been shown to limit As release from arsenopyrite in batch leaching experiments. In CME, the first step is the formation of soluble complexes between a metal (loid) ion (e.g., Al3+ and Ti4+) and a redox-sensitive organic carrier (e.g., catechol, 1,2-dihydroxybenzene, C6H4(OH)). Metal ions freed from the complex precipitate and form a protective coating on the mineral surface limiting the access of oxidants (i.e., O2 and ferric ion) [2-4]
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