Fehér Béla (szerk.): Az ásványok vonzásában, Tanulmányok a 60 éves Szakáll Sándor tiszteletére (Miskolc, 2014)
Móricz Ferenc - Mádai Ferenc - Walder Ingar F.: Szulfidos bányászati meddőkben lezajló piritoxidáció időbeni változása
Temporal changes of pyrite oxidation in sulphidic mine wastes 187 minerals dissolve back and under such a low pH only sulphate minerals are formed, such as jarosite, melanterite or gypsum. The increase in pyrite oxidation rate means that in the future the reactions will become faster. Because of the low pH and speeding up of the reactions, the heavy metal mobility increases. Partly oxidized stage (marked type “B”) covers the samples Bol 3 (Fig. 2), Itos Granza 2 (Fig. 3) and Itos jig 1 (Fig. 4), where the pyrite oxidation is maximal, thus stable - changes only within a few percentage — in the different years. The maximal pyrite oxidation rate also means that this stage has the lowest pH, which keeps for longer time. In the beginning of this stage still the sulphate minerals will be the dominant secondary phases, but in the end of the stage as the pyrite oxidation rate starts decreasing and the pH increasing, beside the sulphates, some oxi-hydroxide minerals can appear. Strongly oxidized stage (marked type “C”) includes the samples Bol 1 (Fig. 2) and Itos Granza 1 (Fig. 3), where the pyrite oxidation rate is decreasing in consecutive years. The reaction rate slows down, thus the pH continuously increasing, but not as steep as the decreasing was in the first stage. The slow increase of pH in this phase is due to pyrite being excused. Bulk oxidation rate becomes lower due to less pyrite available. Beside the determination of the three differentiated stages, on those samples which are in the “Partly oxidized stage”, thus the sample Bol 3, Itos Granza 2 and Itos jig 1, further establishment was done. In this stage the pyrite oxidation rate is stable in the consecutive years, thus the oxidation itself does not change in function of time, at least for several years. Average of the pyrite oxidation rates from the consecutive years were calculated, which were divided by the pyrite content of the samples. In case of the three samples, between the pyrite oxidation rate and the pyrite content linear correlation was defined (Fig. 8). For those Bolivian samples, which are in “Partly oxidized stage”, calculated to 1 kg of sample, every percentage of pyrite means apx. 12-13 mg of pyrite oxidation weekly. ♦ Bol 3 ■ Itos Granza 2 * Itos jig 1 — Trend line Fig. 8. Correlation between oxidation rate and pyrite content. 8. ábra. A piritoxidáció mértéke és a pirittartalom közötti összefüggés.
