Abstract:
Pyrite, one of the most abundant metal sulfide minerals found in nature, is considered as main cause of a serious anthropogenic environmental impact caused by mining activities known as acid mine drainage (AMD), releasing highly acidic leachate contaminated with various heavy metals and contaminating natural waterway. In general, dissolution process of pyrite is an electrochemical phenomenon, of which pyrite dissolution at anode and reducing oxidants at cathode on the pyrite surface. Study results on effects of common metal oxides, like hematite (α-Fe2O3) and alumina (α-Al2O3), which naturally come to contact with pyrite at the AMD contaminated sites, and also preliminary study results on redox behavior and stability of metal-organic complexes (i.e. Ti- and Si-catechol complexes) on the pyrite surface are reported in this thesis.
The hematite was chosen for this study because it is one of the main final products from pyrite dissolution process and the alumina was chosen as a representative of alumino-silicate minerals commonly found in nature. Results of the study on effects of hematite and alumina on pyrite dissolution dynamics based on batch-type experiment indicated the pyrite dissolution decreased with the presence of hematite but increased with the presence of alumina. Upon electrochemical study using pyrite crystal electrode, it was found that anodic half-cell reaction of pyrite dissolution was enhanced with the presence of either hematite or alumina. Whereas, the cathodic half-cell reaction was lessened due to the attached metal oxide particles physically reduce contact area between the pyrite and oxidants.
Carrier Microencapsulation is a pyrite passivation technique that utilize metal-organic complexes to suppress pyrite oxidation and change pyrite’s surface condition. In this study, stability of metal-catechol complexes in solution and on pyrite were evaluated as fundamental study for further researches in the future. The results confirmed the presence of metal-catechol complexes in alkaline solution.
