Yan-sheng Zhang

Bioleaching of chalcopyrite by pure and mixed culture

The bioleaching of chalcopyrite in shake flasks was investigated by using pure Acidithiobacillus ferrooxidans and mixed culture isolated from the acid mine drainage in Yushui and Dabaoshan Copper Mine in China, marked as YS and DB, respectively. The mixed culture consisted mainly of Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans, and Leptospirillum spp. (Leptospirillum ferriphilum and Leptospirillum ferrooxians). The results show that the mixed culture is more efficient than the pure Acidithiobacillus ferrooxidans because of the presence of the sulfur-oxidizing cultures that positively increase the dissolution rate and the recovery of copper from chalcopyrite. The pH value decreases with the decrease of chalcopyrite leaching rate, because of the formation of jarosite as a passivation layer on the mineral surface during bioleaching. In the bioleaching using the mixed culture, low pH is got from the sulfur oxidizing inhibiting, the formation of jarosite. The copper extraction reaches 46.27% in mixed culture and 30.37% in pure Acidithiobacillus ferrooxidans after leaching for 75 d.

Bacterial leaching of chalcopyrite and bornite with native bioleaching microorganism

Abstract A native mesophilic iron-oxidizing bacterium, Acidithiobacillus ferrooxidans , has been isolated (30°C) from a typical, lead-zinc concentrate of Dachang Mine in the region of Liuzhou located in the southwest of China. Two typical copper sulfide minerals, chalcopyrite and bornite, were from Meizhou Copper Mine in the region of Guangdong Province, China. Variation of pH and cell growth on time and effects of some factors such as temperature, inoculation cell number, and pulp density on the bioleaching of chalcopyrite and bornite were investigated. The results obtained from the bioleaching experiments indicate that the efficiency of copper extraction depends on all of the mentioned variables, especially the pulp density has more effect than the other factors on the microorganism. In addition, the results show that the maximum copper recovery was achieved using a mesophilic culture. The copper dissolution reached 51.34% for the chalcopyrite while it was 72.35% for the bornite at pH 2.0, initial Fe(II) concentration 9 g/L and pulp density 5%, after 30 d.

Electro-flotation and collision-attachment mechanism of fine cassiterite

In order to discuss the particle-bubble interaction during the electro-flotation of cassiterite, the recovery of cassiterite with different particle sizes was investigated, and the collision mechanism between the cassiterite particles and H2 bubbles was explored. The flotation tests were carried out in a single bubble flotation cell. The results show that cassiterite particles <10 μm, 10–20 μm, 20–38 μm and 38–74 μm match with bubbles with size of 50–150 μm, about 250 μm, 74 μm and 74 μm, respectively, and a better recovery can be obtained. It is demonstrated that the recovery of cassiterite is influenced by the size of cassiterite particles and bubbles. Furthermore, the probabilities of collision, adhesion, detachment and collection were calculated using the collision, attachment and collection models. Theoretical calculation results show that the collision probability decreases sharply with decreasing particle size and increasing bubble size (below 150 μm). The attachment probability would increase from the effective collision, leading to the increase of recovery.

Bioleaching of low grade nickel sulfide mineral in column reactor

Abstract Jinchuan low grade nickel (0.4%–0.6% Ni, mass fraction) sulfide mineral ore contains a remarkably high content of magnesia (30%–35% MgO, mass fraction) present in the main gangue minerals. Bioleaching was performed to investigate the feasibility to process the mineral due to its relative simplicity, eco-friendly operation and low capital cost requirements. The mixed mesophiles were enriched from acid mine drainage samples collected from several acid mines in China. Considering that the magnesia is easily extracted by acid solution and the excessive Mg 2+ will exceed the tolerance of the mixed mesophiles, three effective means were used to reduce the disadvantage of magnesia during the bioleaching operation. They were adaptation of the mixed mesophiles to improve the tolerance; pre-leaching to remove most leachable magnesia and periodic bleeds of a portion of the pregnant leaching solution to control the level of Mg 2+ based on the tolerance of the mixed mesophiles. An extraction of nickel (90.3%) and cobalt (88.6%) was successfully achieved within a 300 d leaching process from the Jinchuan low grade nickel sulfide mineral ore using a column reactor at ambient temperature.

Microbial leaching of marmatite by Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans

The bioleaching of marmatite in shaken flasks was studied. After leaching for 29 days, the leaching ratio of zinc was 91%. Three kinds of bacteria, mixture-based bacteria, 9K-based bacteria and sulfur-based bacteria were used in marmatite leaching, of which the mixture-based bacteria have the best leaching result while the sulfur-based bacteria have the worst. By analyzing the leaching residue using SEM and EDXA, the marmatite leaching mechanism was discussed.

Simulated small-scale pilot heap leaching of low-grade copper sulfide ore with selective extraction of copper

Abstract The bioleaching of low-grade copper sulfide ore and the selective extraction of copper were investigated. Lix984 dissolved in kerosene was used as extractant. The results show that it is possible to selectively leach copper from the ores by heap leaching. The copper concentration of leaching liquor after 250 d is 2.17 g/L, and the copper concentration is 0.27 g/L after solvent extraction. The leach liquor was subjected to solvent extraction, scrubbing and selective stripping for the enrichment of copper and the removal of impurities. The pregnant copper sulfate solution produced from the stripping cycle is suitable for copper electro-winning.