Shake Flask Leaching Experiments Research Articles

Isolation and identification of a phosphate solubilising fungus from soil of a phosphate mine in Chaluse, Iran

ABSTRACTMicrobial solubilisation of phosphorus from insoluble phosphates is an environmental friendly and cost effective approach in sustainable soil management. Introducing the indigenous microorganisms to soil requires shorter adaptation period and causes fewer ecological distortions than exogenous microorganisms. This study was conducted to isolate and identify the indigenous fungi for phosphate solubilisation in Mazandaran, Iran. A potent phosphate solubilising fungus was isolated from an Iranian phosphate mine and selected for solubilisation of rock phosphate (RP). The identified fungus was characterised by calmodulin-based polymerase chain reaction method as Aspergillus tubingensis SANRU (Sari Agricultural Sciences and Natural Resources University). The phosphate solubilisation ability of the fungal strain was carried out in shake-flask leaching experiments containing various concentrations of RP (1%, 2%, 4%, or 8% w/v). The maximum P solubilisation rate of 347 mg/l was achieved at 1% of RP concentration on day 9. The regression analysis indicated that the P solubilised mainly through acidification. This study shows the possibility of using A. tubingensis SANRU for application in the management of P fertilisation.

Bioleaching of copper, nickel and cobalt from the low grade sulfidic tailing of Golgohar Iron Mine, Iran

This study was conducted to establish the possible application of bioleaching to recover valuable metals from the sulfidic tailing of Golgohar Iron Mine (Kerman, Iran). Shake flask leaching experiments were carried out in the presence of a mixed culture of moderately thermopilic microorganisms at a stirring rate of 150rpm and a temperature of 45°C, with the addition of yeast extract (%0.02 (w/w). The influence of bacterial inoculation, pH, nutrient medium type and pulp density on the recovery of copper, nickel and cobalt from the tailing was investigated. The results showed that 55.0% of copper, 98.2% of nickel and 59.5% of cobalt could be extracted from the tailing through the bioleaching process after 30days at 5% (w/v) pulp density. The recovery of valuable metals from the tailing in the presence of microorganisms was approximately three times higher than that in the un-inoculated leaching experiment under similar conditions. It was also found that the recovery of copper at the initial pH of 1.2 was 17% higher than that at the pH of 1.8, while nickel and cobalt recoveries were 37% and 23% more at the pH of 1.8, respectively. It was also revealed that the recoveries of valuable metals were approximately similar in both 9K and Norris nutrient media. Moreover, the results showed that in both nutrient media, copper recovery at the higher pulp density was significantly higher than that at the lower pulp density; this was mainly attributed to the lower redox potential. On the other hand, nickel and cobalt recoveries were higher at the lower pulp density, probably due to the higher redox potential values. A two-stage bioleaching process in which the redox potential is controlled at a low level in the primary reactors, followed by the secondary reactors with a high redox potential is supposed to achieve the maximum recovery of valuable metals.

Suppression of Pyrite Oxidation by Carrier Microencapsulation Using Silicon and Catechol

Acid mine drainage (AMD) is formed from the natural oxidation of sulfide minerals such as pyrite and FeS2. Prevention of AMD is very important and several techniques are currently being investigated for the treatment and abatement of AMD. This paper proposes carrier-microencapsulation (CME) using Si–catechol complex – for preventing pyrite oxidation. In CME, the water soluble organic carrier, catechol, and metal ion, Si, make a complex, e.g., tris-catecholato complex of Si4+, which oxidatively decomposes on pyrite surface and forms a stable oxide or hydroxide, e.g., Si(OH)4 or SiO2 layer on the pyrite surface as a protective coating against pyrite oxidation. To demonstrate the effect of CME using on pyrite oxidation, shaking flask leaching experiments of pyrite without and with CME treatment were performed. Significant halt in pH drop was observed after the CME treatment of pyrite. The CME coating was found very effective even at low concentration of 1 and 5 mol m−3. The amount of Fe and S leached were lower from the pyrite with CME treatment than without CME treatment, indicating that CME using Si and catechol is effective in suppressing pyrite oxidation. The effect of pH and presence of microorganism were also evaluated. The CME coating was found very effective even in acidic pH range. The CME treatment suppressed pyrite oxidation even in the presence of iron oxidizing microorganism. Presence of Si and O on the residue pyrite surface in energy-dispersive X-ray spectroscopy analysis supported the sustainability of CME coating at acidic pH.

Bioleaching of metal ions from low grade sulphide ore: Process optimization by using orthogonal experimental array design

The present work was aimed at studying the bioleachability of metal ions from low grade sulphide ore containing high amount of carbonaceous materials by selected moderately thermophilic strain of acidophilic chemolothotrophic bacteria, Sulfobacilllus thermosulfidooxidans. The bioleaching process was optimized by constructing L25 Taguchi orthogonal experimental array design and optimization of variable proportions of process parameters. Five factors were investigated and twenty five batch bioleaching tests were run under lower, medium and higher levels of these factors. The parameters considered for shake flask leaching experiments were initial pH (1.8, 2, 2.5, 3, 3.5), particle size, (50, 100, 120, 200, 270
m), pulp density (1, 5, 10, 15, 25%), temperature (40, 45, 47, 52, 57oC) and agitation (100, 120, 180, 220, 280 rpm). Statistical analysis (ANOVA) was also employed to determine significant relationship between experimental conditions and yield levels. The experimental results for selective leaching showed that under engineered leaching conditions; pH 1.8, particle size 120
m, pulp density 10%, temperature 47°C and agitation 180 rpm, the percent bioleachabilities of metals were Zn 72%, Co 68%, Cu 78%, Ni 81% and Fe 70% with an inoculum size of 1.0 ×107 /mL.

Effects of coexisting metal ions on the redox potential dependence of chalcopyrite leaching in sulfuric acid solutions

The leaching rate of chalcopyrite (CuFeS 2) in H 2SO 4 solutions depends on the redox potential determined by the concentration ratio of Fe 3+ to Fe 2+, and the rate is higher at redox potentials below a critical value (critical potential). In actual leaching systems, different metal ions are released from coexisting minerals to the aqueous phase. The present study investigated the effects of coexisting metal ions on the critical potential of chalcopyrite leaching. Shaking-flask leaching experiments were carried out with 0.1 g of ground chalcopyrite and 10 cm 3 of 0.1 kmol m − 3 H 2SO 4 containing 0.1 kmol m − 3 Fe 2+ and 0.001 kmol m − 3 of the metal ions at 298 K in air. The initial redox potential was adjusted by adding Fe 3+, and the amount of Cu extracted after 24 h was investigated as a function of the potential. The results indicate that the critical potential increases by the addition of Ag + or Bi 3+ but is not affected by Pd 2+, Hg 2+, Cd 2+, Zn 2+, Ni 2+, Co 2+, or Mn 2+. The results were interpreted by a reaction model assuming the formation of intermediate Cu 2S due to the reduction of chalcopyrite and subsequent oxidation of the Cu 2S at potentials below the critical potential. Catalytic effects of metal ions on chalcopyrite leaching are also discussed based on the experimental results and the proposed model.

Optimization of Bacterial Oxidation Process Parameters for Selective Leaching of Nickel by Thiobacillus Ferrooxidans

Nickel bioleaching from copper flotation concentrate assumes greater significance because of its value and not many studies are carried out in these lines. Hence, nickel leaching was attempted and several process parameters of bacterial oxidation for copper flotation concentrate were examined for optimization. The parameters considered for shake flask leaching experiments were temperature, pulp density, particle size, agitation, residence time and inoculum size. The effect of variable proportions of each parameter on nickel leachability was studied. Optimum values of pulp density (10%) and agitation (140 rpm) played an important role in controlling the mass transfer resistance during leaching process. Increase in temperature from 27oC to 30oC has accelerated the bacterial oxidation process while initial concentration of inoculum (1-10%) has not shown considerable variation in nickel leachability. A particle size of ±60#size was found to be essential for bacterial attack. Maintenance of optimum conditions of leaching has yielded considerable nickel recovery (55%) compared to low recovery under unoptimal conditions.

黄銅鉱カラム浸出の無次元化電位に基づく解析

Column leaching experiments for two chalcopyrite concentrates agglomerated on supporting particles were performed with sulfuric acid solutions under various conditions. The results of the column leaching were compared to results of shaking flask leaching experiments reported previously.Factors such as solution composition, coexisting minerals like pyrite, and presence of iron-oxidizing bacteria affected chalcopyrite dissolution, causing a significant variation in the copper extraction fraction vs. time plots. However, copper extraction rate from unit surface area of chalcopyrite could be determined simply from the normalized redox potential proposed previously, a function of the ferric, ferrous and cupric ion concentrations. The copper extraction rate vs. normalized potential plot for the column leaching data fitted well with the plot obtained by shaking flask experiments, and the copper extraction rate has a maximum at normalized potentials of 0.4 to 0.5. These results suggest that the normalized potential could be used to assess and optimize chalcopyrite leaching with different methods and under various conditions.

硫酸溶液中での黄銅鉱浸出に対する活性炭と石炭の触媒作用

Activated carbon is known as a catalyst for chalcopyrite leaching in sulfuric acid solutions. This paper compares the effects of six different activated carbon samples on copper extraction from a chalcopyrite concentrate by shaking flask leaching experiments at 303 K under atmospheric conditions. Eight different coals were also evaluated as an alternative to activated carbon.Except for one activated carbon sample, activated carbon addition enhanced copper extraction. Increases in the weight ratio of activated carbon to the chalcopyrite concentrate caused increases in copper extraction. The effects of the coals on copper extraction were related to the rank of the coals: Low rank coals like brown coal, which have low fixed carbon contents and high contents of volatile matter, suppress copper extraction, and high rank coals, which contain more fixed carbon and less volatile matter, enhance copper extraction. High rank coals stored under atmospheric conditions over long periods (more than 7 months) suppressed copper extraction, implying that oxidation of the coal surface and its products cause the suppression in copper extraction.The experimental results are analyzed and discussed with a reaction model for the redox potential dependence of chalcopyrite leaching, which assumes the formation of intermediate Cu2S by chalcopyrite reduction and a subsequent oxidation of the Cu2S.

Alterations in surfaces and textures of minerals during the bacterial leaching of a complex sulfide ore

Abstract The purpose of the work was to characterize changes in surface textures of minerals during the biological leaching of a complex sulfide ore. The ore contained pyrrhotite (FeI_xS), pyrite (FeS2), sphalerite (ZnS), pentlandite [(Ni,Fe,Co)9S8], and chalcopyrite (CuFeS2). Several mixed cultures were initially screened using the ore material as the sole substrate. Shake flask leaching experiments showed no major differences among test cultures, which were all derived by enrichment techniques using environmental samples collected from a mine site. Leached pyrrhotite surfaces were invariably surrounded by a dark rim of elemental S. A reaction zone was also associated with leached sphalerite grains. Chemical analyses of leach solutions indicated that the relative ranking of biological leaching of the sulfide minerals was Zn > Ni > Co > Cu. Microscopic observations were in keeping with this rankin

Interaction of chalcopyrite and sphalerite with pyrite during leaching by Thiobacillus ferrooxidans and Thiobacillus thiooxidans

The interaction of chalcopyrite and sphalerite with pyrite during leaching by Thiobacillus ferrooxidans and Thiobacillus thiooxidans was studied in shake-flask leaching experiments and in respirometer experiments with resting cells. Two samples of pyrite (Nos. 1 and 2) were used. In shake-flask experiments in the absence of bacteria, the copper and zinc extraction rates increased in the presence of No. 1 pyrite from 1.6 to 10.2 and 13%, respectively, and in the presence of No. 2 pyrite from 1.6 to 3.5 and 5.8%, respectively. Thus the effect of pyrite was greater with sphalerite than with chalcopyrite and the No. 1 pyrite was more effective than the No. 2 pyrite. Thiobacillus ferrooxidans increased the leaching rates of Cu from chalcopyrite (from 1.6 to 11.1%), of Zn from sphalerite (from 1.6 to 36%), and of Fe from pyrite (from 7.3 to 29.9% (No. 1) and from 5.1 to 49.3% (No. 2)), although a period of adaptation was required for sphalerite leaching. Thiobacillus thiooxidans did not leach Cu form chalcopyrite, but increased leaching of Zn from sphalerite (from 1.6 to 8.3%) and some Fe from pyrite (from 7.3 to 9.5% (No. 1) and from 5.1 to 13.1% (No. 2)). In the chalcopyrite–pyrite mixture, Cu leaching was further stimulated by T. ferrooxidans (from 10.2 to 14.5% (No. 1) and from 3.5 to 12.2% (No. 2)) and by T. thiooxidans (from 3.5 to 5.8% (No. 2)). The Zn leaching from the sphalerite–pyrite combination increased further with T. ferrooxidans (from 13.0 to 61.7% (No. 1) and from 5.8 to 65.8% (No. 2)) and T. thiooxidans (from 13.0 to 22.4% (No. 1) and from 5.8 to 14.7% (No. 2)). The Fe solubilization from pyrite was inhibited by the presence of chalcopyrite or sphalerite with or without bacteria. Short-term respirometer studies generally supported the leaching results. Oxygen consumption was faster for chalcopyrite or sphalerite in the presence of pyrite. The effect was stronger for sphalerite, although the rapid pyrite oxidation by T. ferrooxidans was inhibited by the interaction. Chalcopyrite alone was oxidized by T. ferrooxidans but not by T. thiooxidans, while sphalerite alone was oxidized only by the latter. It is concluded that shake-flask leaching and Warburg respirometer experiments complement each other in elucidating the complex processes involved in bacterial metal leaching of sulfide ores. Key words: Thiobacillus, sulfide ores, oxidation, mineral leaching.

Effects of Cinnabar on Pyrite Oxidation by Thiobacillus ferrooxidans and Cinnabar Mobilization by a Mercury-Resistant Strain

The effect of cinnabar on pyrite oxidation by mercury-sensitive and mercury-resistant strains of Thiobacillus ferrooxidans was investigated by using percolation columns. Mercury-resistant strains oxidized pyrite in pyrite-cinnabar mixtures (1 and 10%, wt/wt), whereas a mercury-sensitive strain did not. Elemental mercury was produced by the mercury-resistant strains growing in the pyrite-cinnabar mixtures in percolation columns and in flasks containing cinnabar only. Manometric experiments showed that cinnabar had little effect on oxygen uptake of mercury-sensitive or mercury-resistant cells growing on ferrous sulfate, pyrite, or pyrite-ferrous sulfate mixtures. In addition, shake flask leaching experiments showed that cinnabar had little effect on pyrite oxidation at 1% (wt/wt) but inhibited growth of mercury-sensitive and mercury-resistant strains at 10%. Mercury-resistant strains were unable to grow on cinnabar as an energy source.