Simultaneous suppression of acid mine drainage formation and arsenic release by Carrier-microencapsulation using aluminum-catecholate complexes. (August 2018)

• Record Type: Journal Article
• Authors: Park, Ilhwan; Tabelin, Carlito Baltazar; Seno, Kensuke; Jeon, Sanghee; Ito, Mayumi; Hiroyoshi, Naoki
• Is Part Of: Chemosphere. Volume 205(2018)
• Page Start: 414
• Page End: 425
• Publication Date: 2018-08
• Subjects: Acid mine drainage -- Al-catecholate complexes -- Arsenopyrite -- Microencapsulation -- Pyrite; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2018.04.088
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: Pyrite (FeS2 ), the most common sulfide mineral in nature, plays an important role in the formation of acid mine drainage (AMD), one of the most serious environmental problems after the closure of mines and mineral processing operations. Likewise, arsenopyrite (FeAsS) is an important sulfide mineral because its dissolution releases toxic arsenic (As) into the environment. To mitigate the serious environmental problems caused by pyrite and arsenopyrite, this study investigated carrier-microencapsulation (CME) using Al-catecholate complexes, a technique that selectively forms protective coatings on the surfaces of sulfide minerals, by electrochemical techniques and batch leaching experiments coupled with surface sensitive characterization techniques. Cyclic voltammetry (CV) of Al-catecholate complexes (mono-, bis-, tris-catecholate) suggest that these three species could be oxidatively decomposed in this order: [Al(cat)3 ] 3– →[Al(cat)2 ] – →[Al(cat)] + →Al 3+, and these reactions were irreversible. Among these three species, [Al(cat)] + was the most effective in suppressing pyrite and arsenopyrite oxidations because it requires less steps for complete decomposition than the other two complexes. Analyses of CME treated minerals by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) indicated that they were covered with Al-oxyhydroxide (γ–AlO(OH)), which became more extensive at higher [Al(cat)] + concentrations. In addition, this coating was stable even at relatively high applied potentials that simulated surface oxidizing conditions. Based on these results, a detailed mechanism of Al-based CME is proposed: (1) adsorption of [Al(cat)] + on the surface of mineral, (2) oxidative decomposition of [Al(cat)] + and release of "free" Al 3+, and (3) precipitation and formation of Al-oxyhydroxide coating. Graphical abstract: Image 1 Highlights: Al-catecholate complexes were oxidatively and sequentially decomposed. [Al(cat)] + was the most effective in suppressing pyrite and arsenopyrite oxidations. Minerals were covered with an Al-oxyhydroxide coating after Al-based CME. Coating was stable and inhibited the anodic half-cell reaction. Mechanism of Al-based CME involves adsorption, decomposition and coating formation.