Biodepression of Copper-Activated Pyrite with Acidithiobacillus ferrooxidans in Flotation with Fresh and Seawater

Abstract

Acidithiobacillus ferrooxidans has been shown to be a good depressant of pyrite in freshwater and seawater flotation. However, the effect of these bacteria over copper-activated pyrite has not been studied. At the industrial scale, the activation of pyrite with copper is a common process that occurs because Cu2+ ions, released from other minerals, react with pyrite. This is a problem because Cu2+ ions facilitate the reaction of pyrite with the xanthate collectors, becoming hydrophobic and reaching the froth. In this study, microflotation experiments in a Hallimond tube were conducted to evaluate the depressant effect of A. ferrooxidans over non-activated and Cu-activated pyrite in freshwater and seawater flotation. The experiments were carried out at pH 4, 6, 8, 10 and 12 and pyrite was mixed with CuSO4 at 2.5×10−5 and 5×10−5 M in order to activate its surface. Considering the results obtained in the microflotation tests, it is possible to conclude that Acidithiobacillus ferrooxidans is able to depress non-activated and Cu-activated pyrite at the entire pH range studied (4–12) in freshwater. On the other hand, the use of bacteria in flotation with seawater proved to be effective to depress non-activated and Cu-activated pyrite at pH 8 and 10 with better results achieved at pH 10. At this pH, the non-activated pyrite recovery dropped from 96% to 15%, and the recovery of Cu-activated pyrite dropped from 95% to 32% when the activation was carried out at 2.5×10−5 M, and from 87% to 50% when the activation was conducted at 5×10−5 M of CuSO4. The XPS analysis showed that chalcopyrite and copper (II) hydroxide were formed on the pyrite surface when it is contacted with CuSO4.

Kalsit Biyoflotasyonunda Deniz ve Şebeke Suyunun Karşılaştırılması

“…Son yıllarda yapılan deniz suyu ile doğal pH'ta yapılan flotasyon çalışmalarında, At. Ferrooxidans'ın molibdenit veya kalkopirit flotasyonunu etkilemeden pirit bastırıcısı olarak kullanılabileceği gösterilmiştir [6,7]. Sonuç olarak, böyle bir uygulama sadece daha sürdürülebilir bir teknoloji olarak kalmayıp, aynı zamanda kurak (yeraltı su kaynağı sınırlı) ve denize yakın bölgelerdeki işletme koşullarını da iyileştirebilecektir.…”