Congren Yang

Bioleaching of chalcopyrite by moderately thermophilic microorganisms.

The leaching of chalcopyrite by moderately thermophilic microorganisms was investigated by employing cyclic voltammetry (CV), accompanying with the leaching behavior elucidation. Leaching experiment showed that there was clear benefit in leaching chalcopyrite within the low solution potential (below 400 mV vs. SCE), compared to the high potential leach (above 550 mV vs. SCE). Simultaneous maintenance of an appropriate concentration of total dissolved iron was necessary and also beneficial to leach chalcopyrite. The leaching results showed the existence of an optimum pH in the leaching of chalcopyrite by the moderately thermophilic microorganisms. The analysis of CV results revealed that the chalcopyrite was reduced to a series of intermediate products (such as talnakhite, bornite and chalcocite) in the cathodic, and then the intermediate product (chalcocite) was oxidized in the anodic.

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.

Solution chemistry and utilization of alkyl hydroxamic acid in flotation of fine cassiterite

Solution chemistry and ?otation of cassiterite in the presence of alkyl hydroxamic acid collector were investigated. Results show that the alkyl hydroxamic acid is able to float fine cassiterite very well at relatively alkaline conditions, and the pH range of better flotability broadens with the increase of chain length of the collector. Moreover, the metal cations influence the flotation mostly depending on the pH of the medium and to some extent on the concentration of metal cations. Theoretical calculation on the group electronegativity indicates that the alkyl chain length of about seven is of great superiority in the synthetization of hydroxamic acid collector for cassiterite flotation. A co-adsorption between molecules and ions onto cassiterite surface is considered according to the lg c—pH diagram analysis. In terms of zeta potential and infrared spectra, the main interaction involves electric charge interaction, hydrogen bonding interaction and complexation, with the proposed formation of an O, O-five membered rings chelate compound .

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.

Sulfur composition on surface of chalcopyrite during its bioleaching at 50 °C

Abstract The composition of passive layer of chalcopyrite was investigated by X-ray photoelectron spectroscopy (XPS), accompanied with cyclic voltammetry (CV). The leaching experiment shows that the extraction rates of Cu with leaching for 30 d by sterile control and microorganisms are 4.0% and 21.5%, respectively. In comparison, 3.8% and 10.5% Fe are leached by sterile control and microorganisms, respectively. The results of XPS studies suggest that Fe atoms dissolve preferentially from the chalcopyrite lattice, and disulfide (S 2 2− ), polysulfide (S n 2- ) and elemental sulfur (S 0 ) are identified on the chalcopyrite surfaces leached by sterile control and microorganisms. Additionally, sulfate (SO 4 2- ) is detected on the chalcopyrite surfaces leached by microorganisms, and most of it probably originates from jarosite. The analysis of CV results reveals that metal-deficient sulfide (Cu 1- x Fe 1- y S 2- z , y > x ) and elemental sulfur (S 0 ) passivate the surface of chalcopyrite electrode. The elemental sulfur and/or jarosite coating on the chalcopyrite surface may have impact on the leaching process; however, the disulfide, polysulfide or metal-deficient sulfide plays a more key role in the chalcopyrite leaching.

Floc flotation of marmatite fines in aqueous suspensions induced by butyl xanthate and ammonium dibutyl dithiophosphate

The hydrophobic flocculation of marmatite fines in aqueous suspensions induced by butyl xanthate (KBX) and ammonium dibutyl dithiophosphate (ADD) was investigated using laser particle size analysis, microscopy analysis, electrophoretic light scattering, contact angle measurement and infrared spectroscopy. The studies were performed on single minerals with size ≤20 µm by varying several parameters, including pH, collector concentration and kerosene addition. The results show that the floc flotation closely correlated with the size of flocs and the particle hydrophobicity, but was not lowered with increasing the particle surface charges due to collector adsorption. Under good operating conditions, the floc flotation of marmatite fines as a function of KBX and ADD can all reach floatability over 90%, in comparison with conventional flotation obtaining floatability of about 60%. It also has been found that a small addition of kerosene greatly improved the floc flotation because of the formation of oil films on marmatite particles. The results of FTIR spectra indicate that adsorption of the two collectors onto marmatite were chemical adsorption.