Studies on kinetics and thermodynamics of biomachining pure copper

The kinetics and thermodynamics of biomachining pure copper by Thiobacillus ferrooxidans were quantitatively analyzed. The kinetic effect of bacteria on the ion-cycle between Fe2 and Fe3 and the thermodynamic effect of hydrolysis on the changes of pH in biomachining processes were expounded through six series of experiment. Finally a model of ion-cycle in the biomachining processes was proposed, and the measures for maintaining the stable equilibrium of the ion-cycle were also discussed.     

Integrated biological process for the treatment of a Chilean complex gold ore

Abstract: A process for gold recovery from a complex Chilean ore from Burladora (IV Region) which integrates concentration by flotation, bacterial leaching and cyanidation was studied at a laboratory scale. The chemical composition of the ore is 8.2% Fe, 0.78% Cu, 0.88% As and 3.5 g/t Au, with pyrite, hematite, covelite, arsenopyrite and chalcopyrite as the main metal-bearing minerals. The initial gold recovery by conventional cyanidation on a crushed ore sample was only 54%. The ore was ground and concentrated by flotation with a gold recovery of only 56%. The gold content of the concentrate is 17 g/I Au. Concentrate samples were leached in 1.5 l stirred reactors at 10% pulp density in 1000 ml of acid medium (pH 1.8). Some experiments were inoculated with harvested bacteria previously isolated from mining solutions. Dissolved metals, pH and bacteria concentration in the leaching solutions were periodically determined. In the presence of bacteria, oxidation of the ferrous ion produced by acid dissolution of the concentrate was observed, and after 4 days of leaching 100% of the dissolved iron was present as ferric ion. Gold recovery by cyanidation increased from 13% for the initial concentrate to 34% after 10 days of chemical acid leaching and 97% after 10 days of bacterial leaching. To increase the total gold recovery, the flotation tailings were submitted to cyanidation. A complete flowsheet of the process and a first economical evalualion are proposed. As a possible alternative process, heap bacterial leaching and further cyanidation of the ore are suggested.     

The role of exopolymers in the bioleaching of a non-ferrous metal sulphide

Exocellular polysaccharides were extracted from Thiobacillus ferrooxidans cells grown in the presence of iron. Cells without these compounds could not adhere to covellite. The loss of the layer of exocellular polysaccharides also affected the direct mechanism of bioleaching of covellite in a negative way. This ability to attach to and leach covellite was restored within a few hours when exopolymeric material was produced again. The addition of exocellular compounds to cells stripped of exocellular polymers also restored their ability to the same level as that of untreated cells. Thiobacillus thiooxidans was not able to attach to and leach covellite even when exocellular compounds from Thiobacillus ferrooxidans were added. Received 2 June 1998/ Accepted in revised form 8 January 1999     

Dissolution of sulphur particles by Thiobacillus ferrooxidans: substrate for unattached cells

The growth of Thiobacillus ferrooxidans on sulphur is known to proceed through the attachment of cells to the sulphur particles. Experiments, However, show that the cells in the liquid phase, which are not attached to the sulphur particles, also grow. It has been shown through the use of a two-compartment membrane reactor that this increase is partially due to the release of ions, corresponding to partially oxidized of sulphur, into the solution by the attached cells. The main soluble ion has been found to the thiosulphate, but traces of sulphite have also been detected. (c) 1993 John Wiley & Sons, Inc.     

Biological oxidation of metallic copper by Acidithiobacillus ferrooxidans

This is a report on the kinetic aspects and the analytical study of the bioproducts of the oxidation of zero-valence copper by immobilized Acidithiobacillus ferrooxidans. Two different mechanisms of oxidation were considered: direct and indirect. A custom-built bioreactor was used to grow A. ferrooxidans in an iron-free media, which was required for the study of the direct mechanism. X-ray microdiffraction analysis of the copper after biooxidation in the sulfate-free medium revealed the presence of the copper sulfate, piypite, K(2)Cu(2)O(SO(4))(2), which indicates biooxidation of Cu metal has occurred. It was shown that the direct oxidation exists, but it is relatively slow, as compared to the indirect mechanism.     

Bacterial leaching of uranium ore from Figueira—PR, Brazil, at laboratory and pilot scale

Abstract: A bacterial leaching program was carried out in order to evaluate the potential of applying this process to leach uranium from the ore of Figueira-PR, Brazil. The experiments were carried out in shake flasks, column percolation (laboratory and scmipilot scale)and in heap leaching. In shake flasks and in column percolation experiments at laboratory scale, bacterial activity on Ihe ore was confirmed: approximately 60% of uranium was leached, against around 30% in sterilized controls. Colunm percolation experiments at semipilot scale and heap leaching (850 tons of ore) showed uranium extractions of approximately 50%. In both experiments, a complementary sulfuric acid attack, after the bacterial leaching phase, was neccssaw to reach this level of uranium extraction.     

A method for enucleation of Saccharomyces cerevisiae

Abstract We have analysed the response of the acidophilic chemolithotroph Thiobacillus ferrooxidans to phosphate starvation. Cultivation of the bacteria in the absence of added phosphate induced a remarkable filamentation of the cells. Polyacrylamide gel electrophoresis revealed several proteins whose levels increased upon phosphate limitation, as well as some polypeptides that were exclusively synthesized under this growth limitation. One of the proteins whose level increased by the lack of phosphate was apparently an acid phosphatase with a pH optimum of about 3.8, and a molecular mass of 26 kDa, which was located in the periplasm. The N-terminal sequence of a 26 kDa protein derepressed by starvation, which may correspond to the T. ferrooxidans phosphatase, showed 30% and 35% identity with the known sequence of Lysobacter enzymogenes and Escherichia coli alkaline phosphatases, respectively.     

Relationship between the nitrogenase activity and dark respiration rate of Synechococcus RF-1

Growth of three different anaerobic rumen fungi Neocallimastix frontalis, Piromonas communis and Sphaeromonas communis was assessed in vitro at regular intervals by measurements of protein and chitin content and of chitin synthase activity of the cell free extracts. Similar trends and a comparable amount of protein and chitin were observed in the three species. However, chitin synthase activity was higher in S. communis and contrary to the activity of the other two strains did not decrease after maximum enzyme activity was reached. There were positive correlations between chitin content, protein content and chitin synthase activity during the active growth phase of the fungi indicating that they could be confidently used to determine in vitro growth phase and biomass concentration.     

海藻酸钙包埋氧化亚铁硫杆菌的固定化研究

采用非稳态法测定FeSO4在包埋和未包埋氧化亚铁硫杆菌的凝胶中的有效扩散系数。结果表明,FeSO4在凝胶中的有效扩散系数De随着海藻酸钠浓度的升高而降低,当海藻酸钠浓度为2%时最优;凝胶剂CaCl2的浓度对扩散系数的影响较小。包埋的氧化亚铁硫杆菌在10h达到增殖平衡,而FeSO4在包埋细菌的凝胶内扩散系数明显减少。     

Influence of lipopolysaccharides on the attachment of Thiobacillus ferrooxidans to minerals

The loss of part of the lipopolysaccharides (LPS) of the outer membrane of T. ferrooxidans negatively influenced the attachment of the bacteria to minerals and the bioleaching process. LPS previously extracted from T. ferrooxidans and which had come into contact with pyrite inhibited the attachment of cells to minerals and also negatively affected the bioleaching. These results suggest that LPS play an important role in the attachment of the microorganisms and therefore, its presence or absence could affect the bioleaching process.     

Bio-oxidation of iron using Thiobacillus ferrooxidans

The effects of pH, ferrous and ferric ion concentrations on iron oxidation by Thiobacillus ferrooxidans were examined. The initial temperature and bacterial concentration were maintained at 37°C and 2±1×104cells/ml, respectively. The iron oxidation rate increased with increased initial ferrous iron concentration to 4g/l and thereafter decreased. The presence of iron(III) showed a negative effect on the bacterial iron oxidation rate. The increase of pH also showed an increase in the oxidation rate up to pH 1.75. The oxidation rate followed first order kinetics for the parameters studied. A rate equation has been developed.     

Chemotaxis of chemolithotrophic Thiobacillus ferrooxidans toward thiosulfate

Abstract The chemotactic response of Thiobacillus ferrooxidans toward thiosulfate was observed. The traditional assay technique was modified by direct microscopic enumeration of cells which moved into the attractant solution. The optimum concentration shown by thiosulfate-grown cells, tetrathionate-grown cells as well as iron-grown cells was 10³ times the optimum concentration shown by cells grown on elemental sulfur. Iron-grown cells which lack thiosulfate-oxidizing activity showed increased accumulation at optimum concentration as compared to cells grown on elemental sulfur and other reduced sulfur compounds. This indicated the constitutive nature of chemotaxis by T. ferrooxidans toward thiosulfate.     

氧化亚铁硫杆菌培养过程中沉淀的研究

为了减少氧化亚铁硫杆菌培养过程中产生的沉淀,对氧化亚铁硫杆菌培养过程中产生的沉淀物进行了研究,确定了在pH为1．5,K2HPO4用量为0．25g/l,KH2PO4为0．195g/l时菌体可以保持其最高氧化活性,同时产生最少量沉淀物的培养条件,并发现沉淀物对菌体的生长和氧化Fe^2 没有影响。利用饥饿状态的氧化亚铁硫杆菌证明了菌体在一定条件下可以利用黄铁钒沉淀中的部分离子进行生长繁殖。     

Thermal characterization of different isolates of Thiobacillus ferrooxidans

Abstract Ten different isolates of Thiobacillus ferrooxidans were characterized with respect to temperature in the range 2–35°C. Four of the ten strains oxidized ferrous iron exponentially over the entire range of incubation temperatures, including the lowest temperature tested (2°C), and were therefore characterized as psychrotrophic. Jarosite production was substantially reduced at temperatures less than 10°C and was not observed at 2°C. Energy of activation values were in the range 75.2–96.6 kJ/mol°C and indicated that iron oxidation at low temperatures was governed by both a chemical and a physical control.     

氧化亚铁硫杆菌固定化技术研究

在生物脱硫过程中 ,以H - 2软性填料作为氧化亚铁硫杆菌 (Thiobacillusferrooxidans)的固定化载体 ,构建了固定床生化反应器。考察了不同稀释率固定下床生化反应器氧化Fe2 + 的情况 ,在通气量为 330L/h ,稀释率为 0 6h-1条件下 ,Fe2 + 最大氧化速率达 7 6 7g[Fe2 + ]/L·h。该反应器连续运行 10 0d,固定化细胞稳定性良好     

Use of Thiobacillus ferrooxidans for iron oxidation and precipitation

Fe(II) oxidation reaction was carried out using an acidophilic microorganism, Thiobacillus ferrooxidans. Four different parameters such as pH, Fe(II), Fe(III) and biomass concentration were studied. The oxida-tion reaction follows a pseudo first order rate equation. Apparent reaction rate constants were calculated. Unified rate equation was developed using the four parameters. Along with oxidation, a part of the iron also was precipitated. The extent of Fe(III) precipitation in each case was calculated. © Rapid Science 1998     

Spatial and temporal distribution of Caulobacter spp. in two mesotrophic lakes

The seasonal distribution of Caulobacter spp. has been determined in the water column of two mesotrophic lakes using most probable number (MPN) viable counting techniques from April, 1972 to March, 1973. Concentrations in Lake Washington, a monomictic lake, peaked at 1000–3300 per ml in the epilimnion during the late spring and summer and reached lows in October of less than 2 per ml prior to fall turnover. The reason for the decrease in viable numbers is not known. Caulobacter spp. began to increase gradually in December, during the winter mixing period well before the spring bloom. Concentrations in Hall Lake, a small kettle lake, were somewhat higher than in Lake Washington, ranging from 0.27 per ml in October to over 5000 per ml during May. In contrast to Lake Washington, the highest populations were found in the metalimnion and upper hypolimnion of Hall Lake. Caulobacter spp. were also found in the anaerobic depths of the hypolimnion. However, these did not grow anaerobically, suggesting that they had settled into the hypolimnion and survived in the cold anaerobic zone. The populations of Caulobacter spp. reached maximum numbers at the approximate times and depths at which algal biomass would be expected to be greatest.     

Bioleaching of a Spanish uranium ore

Abstract: The bioleaching of a low-grade uranium ore in shaker and columns using natural, pure and mixed cultures has been studied. Initially, a chemical and microscopical characterization of the mineral was carried out. Orbital shaker experiments were performed to quickly obtain the best bacterial leaching conditions. Afterwards, small columns were used to determine other variables related to percolation leaching. Finally, an uranium ore from the F6 mine (Ciudad Rodrigo, Spain) was leached in the presence of bacteria using large columns (24 cm diameter and 275 cm height). The most important results were: (i) the ore contains sufficient pyrite in order for uranium bioleaching to take place under optimum conditions; (ii) shaker experiments showed that temperature, pH and type of inoculum are the most important variables in bioleaching; (iii) two different ores were attacked in the columns: altered and non-altered. In the first case, the extraction rate of uranium was higher. However, in both cases the final efficiency was very similar (95%).     

Analysis of muramic acid in holocene microbial environments by gas chromatography,electron impact,and fast atom bombardment mass spectrometry

Analytical procedures have been modified to determine the abundance of muramic acid in four different Holocene sediment samples. Muramic acid is specific to the peptidoglycan moiety of the cell walls of most eubacterial pro‐karyotic organisms. The following procedure seemed to be the most appropriate for the detection of muramic acid and amino acids, including diaminopimelic acid. Hydrolysis of the samples (in 6 N HCl, 4.5 h, at 100°C) was followed by separation and purification of amino sugars and amino acids using Amberlite XAD‐2 and then Bio‐Rad AG 50W‐X8 resins. The N,O‐heptafluorobutyryl‐n‐butyl ester derivatives were prepared by esterification in acidified (3 N HCl) n‐butanol for 3 h at 100°C, followed by acylation by refluxing with heptafluorobutyric anhydride in acetonitrile (2:1 v/v) for 12 min at 150°C. The derivatives were analyzed by gas chromatography (GC) and gas chromatography‐mass spectrometry. Fast atom bombardment (FAB) ionization was used for the muramic acid derivative to determine its molecular weight and structure, d‐and l‐amino acids were separated by GC and a capillary chiral column. By using this technique a stable N,O‐heptafluo‐robutyryl‐n‐butyl ester derivative of muramic acid was identified at picogram levels in Holocene sedimentary microbial communities. It has been reported previously that microorganisms in sediments rapidly degrade muramic acid from cell walls of dead prokaryotes. Kinetic experiments revealed that muramic acid was relatively stable in intact cell walls but decomposed rapidly in the free form. These investigations noted above showed that the concentration of muramic acid may be used as an indicator of the presence of the intact cell walls of cyanobacteria and most other bacteria in Holocene microbial communities, and of microbial contamination in samples older than the Holocene.     

Kinetics improvement of high-grade sulphides bioleaching by effects separation

Abstract: The kinetics of bioleaching of sulphide concentrates by Thiobacillus ferrooxidans can be improved by performing separately the two operations relating the two effects involved in the indirect contact mechanism, (1) chemical leaching and (2) biological oxidation of the Fe2+ produced in the chemical stage (IBES: Indirect Bioleaching with Effects Separation). This scheme permits the separate enhancement of each stage. On the one hand, the chemical attack of the ferric iron to sulphides can be performed at a higher temperature. On the other hand, the biological oxidation stage is more effective when biofilm models are applied. At the same time, inhibitory phenomena produced as a result of the bacterial breaking caused by the abrasion of the solid particles on microorganisms are prevented. In this work the 1BES process has been applied to a Spanish copper-zinc and a copper sulphide concentrate. The objective has been to selectively dissolve zinc, which may be recovered by solvent exraction, the remaining residue being a copper concentrate suitable for pyrometallurgical treatment. The attributes of moderate temperature, atmospheric pressure, low cost of the leaching agent, flexibility and effectiveness make the process very attractive from an economic point of view.