外源Fe2+浓度及矿物粒径对生物浸铀的影响

为改善以往生物浸铀效率不高的缺陷,通过添加外源Fe2+及改变矿物粒径来提高生物对铀的浸出率。研究结果表明：外源Fe2+浓度分别为0、0.5、1.0和2.0 g/L时,铀浸出率分别为87.34%、88.27%、91.23%、89.13%,当浸出体系中Fe2+浓度为1.0 g/L时,铀矿石会产生部分溶解且表面粗糙孔隙明显,有利于铀的浸出,溶浸液中存在适量的Fe2+对生物浸铀的能力具有提升效果。另外,外源Fe2+对铀矿生物浸出符合固体产物层缩核模型,浸出过程主要受扩散控制。当粒径＜- mm和-5 mm时铀浸出率分别为91.23%和83.70%,矿物粒径适当减小可增大颗粒比表面积,同样利于铀的浸出。     

Column Bioleaching of a Low-Grade Silicate Ore of Uranium

The bioleaching of a low-grade Indian uraninite ore (triuranium octoxide, U₃O₈: 0.024%), containing ferro-silicate and magnetite as the major phases, and hematite and pyrite in minor amounts, has been reported. Experiments were carried out in laboratory scale column reactors inoculated with enriched culture of Acidithiobacillus ferrooxidans isolated from the source mine water. The pH effect on uranium recovery was examined with the same amounts of ores in different columns. With the presence of 10.64% Fe in the ore as ferro-silicate, the higher uranium biorecovery of 58.9% was observed with increase in cell count from 6.4 × 10⁷ to 9.7 × 10⁸ cells/mL at pH 1.7 in 40 days as compared to the uranium recovery of 56.8% at pH 1.9 with a corresponding value of 9.4 × 10⁸ cells/mL for 2.5-kg ore in the column. The dissolution of uranium under chemical leaching conditions, however, recorded a lower value of 47.9% in 40 days at room temperature. Recoveries were similar with 6-kg ore when column leaching was carried out at pH 1.7. The bioleaching of uranium from the low-grade ore of Turamdih may be correlated with the iron(II) and iron(III) concentrations, and redox potential values.     

Silver catalyzed bioleaching of low-grade copper ores. Part III: Column reactors

A study of the effect of different variables (inoculation, [Ag], silver addition mode, reactivation of the ore (i.e. delayed silver addition), composition of the pregnant liquid solution, ore particle size, pH and aeration) on the silver-catalyzed bioleaching of two different low-grade copper (> 600 μm) has been investigated in column reactors.The two low-grade copper ores tested, lower K-ore and Pinto Valley Dump ore, behaved similarly during the silver catalyzed process. After more than 300 days of leaching, the addition of both silver and bacteria improved the copper extraction from both low-grade chalcopyritic ores. Copper extraction in the presence of silver displays paralinear kinetics with two stages very well defined, with the first stage being much faster than the second one.Copper extraction from the K-ore surpassed 70% after 350 days of bioleaching using low concentrations of silver (1.4 g Ag/kg Cu). The addition of silver was effective even after the bioleaching process was started. Conversely, silver addition mode and aeration were not significant variables in the bioleaching process. The effect of a pregnant liquid solution collected from a first bioleaching experiment demonstrated that the build up of the solution can negatively affect the copper extraction during the silver-catalyzed chalcopyrite process.Copper extraction from PVD ore surpassed 60% after 300 days of bioleaching using 1.24 g Ag/kg Cu. Copper extraction was substantially affected by both [Ag] and ore particle size. For the ranges between 0.25 and 1.00 g Ag/kg Cu and between < 5.08 × 10⁴ and < 1.27 × 10⁴ μm, the dissolution of copper was favoured with the highest amount of silver and the smallest particle size. On the other hand, silver concentration, pH and silver addition mode were not influential variables in the process.Chemical analyses, XRD and SEM/EDX studies were carried out on different residues after 100, 200 and 325 days of experimentation. Chemical analysis showed that copper is selectively bioleached in the presence of silver and bacteria, while silver remains in the solid phase. The SEM study showed that pyrite remains mainly unattacked during the bioleaching of chalcopyrite from the low-grade copper ore. Jarosite, gypsum and elemental sulphur precipitates have been identified on the residues.     

某砂岩型铀矿床矿石微生物浸出试验

对某砂岩型铀矿床的矿石进行了不同酸度和Fe~(3+)浓度的微生物浸出试验,以及与酸法浸出(H_2SO_4浓度5 g/L)的对比试验。结果表明,微生物浸铀在4 g/L酸度、2 g/L Fe~(3+)条件下铀浸出率最高(96.43%),比酸法浸出率高27%;微生物溶浸时Fe~(3+)浓度超过2 g/L对浸铀没有明显的提升作用。     

Silver-catalyzed bioleaching of low-grade copper ores. Part II: Stirred tank tests

A study of the effect of different variables (inoculation, aeration, silver complexants, [Ag], [Fe³⁺], temperature and chemical activation stage) on the silver-catalyzed bioleaching of two different low-grade copper ores has been carried out in stirred tanks. The catalyzed bioleaching process was greatly affected by bacterial activity. Aeration and the use of different complexing agents (thiosulfate and thiosulfate plus cupric ions) did not enhance but also did not inhibit the copper kinetics in the silver-catalyzed process. On the contrary, the presence of 5 g/L Cl⁻ inhibited the catalytic effect of silver. The effect of silver concentration was tested on two different low-grade copper ores in the range between 10 and 500 mg Ag/kg for the lower K-ore and between 1.4 and 35.7 g Ag/kg Cu for the PVD ore, the former with a higher content of copper. Silver catalysis was effective for both ores but the PVD ore was basically unaffected by silver concentration in the range studied. Maximum copper extractions and copper dissolution rates were obtained with a very small amount of silver (3.6 g Ag/kg Cu). In all cases, the copper recovery was at least twice that in the absence of silver (∼ 30%). High ferric concentrations have been tested in the absence and in the presence of silver. The presence of silver was essential to improve the copper extraction from chalcopyrite in acidic ferric sulfate solutions. However, bioleaching experiments conducted with silver and 1 g/L Fe³⁺ produced lower copper extractions (20%) compared to experiments where ferric iron was absent (55%). The copper dissolution in the silver-catalyzed lower K-ore bioleaching is temperature dependent, with an optimum temperature around 35 °C. The activation energies of the copper dissolution process were 109.7 and 20 kJ/mol in the ranges of temperature between 15 and 28 °C and 28 and 45 °C respectively. The chemical activation stage establishes optimum conditions that promote higher copper extractions in the presence of silver.     

Application of the HeapSim model to the heap bioleaching of the Pueblo Viejo ore deposit

The HeapSim computer model can simulate column, crib, and heap leach processes for a variety of sulfide ores. In this work, the model was used to evaluate the feasibility of heap biooxidizing the high-grade pyrite ore from the Pueblo Viejo deposit in the Dominican Republic. Simulations have revealed few but critical conditions for the success of a full-scale heap.The heap should be inoculated with mesophiles and moderate thermophiles bacteria, as well as extreme thermophilic archaea at the start-up of the biooxidation pretreatment. These microorganisms were isolated from two slurry cultures collected at site and grown in the laboratory at different temperatures. All cell types may be indigenous to the site, but inoculation of the ore and leach solution with all cell types is necessary for the transition into different temperature regimes for best sulfide oxidation performance.To ensure that all parts of the heap achieve at least 65% sulfide oxidation in the planned 400 days of treatment, the heap height should be less than 8 m if aerated at 2 m³/m²/h and irrigated at 8 L/m²/h. These conditions would preclude the formation of “hot spots” that could inhibit even the extreme thermophiles. By increasing the aeration rate to 4 m³/m²/h and the irrigation rate to 11 L/m²/h, the heap could be stacked to 8 m. Large aeration and irrigation rates would lower the temperatures at the top and bottom of the heap. Under these conditions, all parts of the heap could be expected to achieve 65% sulfide oxidation in only 250 days, as indicated by the model.     

Simulation of Bioleaching Heat Effects for Enhancement of Copper Recovery from Sarcheshmeh Chalcopyrite

A heat-transfer model was formulated to determine the distribution of temperature within a bioheap of chalcopyrite of Sarcheshmeh copper mine. Bioleaching employs mixed mesophilic and thermophilic microbes for Cu extraction. Thermophiles are better than mesophiles to dissolve CuFeS₂. The solution irrigation and aeration rates were taken into account as the main operational factors. The model was validated by comparing the temperature profiles of test columns with those of bioheap. The model was used to find the optimal ratio of irrigation to aeration. It was found that when the solution was fed at a flow rate of 5 kg/m² h and air was blown at a flow rate of 7.5 kg/m² h, the transition from a mesophilic to thermophilic state inside the heap was possible. In this situation, the maximum temperature rise inside the heap was about 332 K (59 °C) after 60 days.     

低品位铀矿石微生物柱浸试验

对某低品位铀矿石进行了不同喷淋条件的微生物柱浸试验。结果表明,试验用混合菌群对目标铀矿石具有较强适应性,浸出周期172d,菌浸期间5%和10%喷淋量条件下渣计平均浸出率分别为87.70%和88.53%,耗酸率分别为5.36%和5.37%。菌浸阶段采用较大喷淋量可提高浸出率,但液固比会显著增加,综合成本相应提高。因此,喷淋量的选择应综合考虑铀资源回收率与浸出成本。     

Toxicity of metal extraction and flotation chemicals to Sulfolobus metallicus and chalcopyrite bioleaching

The effect of chemicals used in preparation of mineral concentrates and subsequent extraction of metals to the thermophilic, acidophilic microorganism Sulfolobus metallicus has been tested. The chemicals tested included collectors and frothers employed during flotation of the ore to produce a mineral concentrate, solvent extraction reagents used to remove metals after leaching, and thiocyanate produced as a decomposition product during cyanidation for gold recovery. The effect of these chemicals to S. metallicus depends on the conditions and time frame that the experiments were carried out due to their mode of toxicity and stability in acid pH. The metal extraction chemical that had the least effect on bioleaching was potassium amyl xanthate that increased the leaching rate, possibly due to solubilization of sulfur that can form passivation layers on the surface of minerals. The frother Flotanol C-7 decreased the chalcopyrite leaching rate, despite having no effect on Fe²⁺ oxidation by S. metallicus resting cells. This is probably due to inhibition of oxygen transfer during bioleaching that had little effect on Fe²⁺ oxidation over 20 min. Solvent extraction chemicals inhibited both Fe²⁺ oxidation and bioleaching suggesting their mode of inhibition is due to Fe²⁺ oxidation. The results suggest that relevant concentrations of metal extraction and flotation chemicals can be toxic to chalcopyrite bioleaching by S. metallicus.     

The selective leaching of uranium,vanadium and phosphorus from phosphate ore with hydrochloric acid

The selective leaching of uranium, vanadium, and phosphorus from phosphate ore may be useful in by-product recovery. Experimental results have shown that it is possible to preferentially remove uranium from phosphate ore using dilute HCl (0.05 M). 93 pct of the uranium is leached within 90 min, leaving 94 pct of the phosphorus and 82 pct of the vanadium unattacked. Phosphorus may then be removed by increasing the pH. The apparent activation energies and orders for the leaching reactions were found. For uranium, the apparent order with respect to H⁺ is 1.05 and the apparent activation energy is 7750 J. The apparent order for the leaching of the vanadium minerals with respect to H⁺ is 1.93 and the apparent activation energy is 12800 J. The phosphorus reaction has an apparent order, with respect to H⁺, of 1.98 and an apparent activation energy of 10200 J. The uranium readsorbs at longer times. The readsorption reaction is a function of temperature, particle size, and H⁺ concentration. Two methods of selectivity analysis were used in the analysis of the data-end point analysis and initial rate analysis.     

生物堆浸后期清水洗堆对浸铀的影响

对即将出堆的六个铀矿生物浸出柱,采用不同时间间隔的清水喷淋洗堆,并获取最佳的洗堆工艺参数。结果表明,矿堆尾期连续喷淋10天清水,对pH的提高效果明显,并且可以浸出0.6%左右的铀金属,使浸出液中的铀浓度降低到10mg/L。     

Microbiological leaching of copper from lead mattes

The possibility of recovering copper from lead blast furnace mattes by bioleaching, using bacteria of the genus Thiobacillus ferrooxidans, has been studied. In this paper, the influence of certain variables on the dissolution rate and the adaptation period of the bacteria have been evaluated, including energy source, nutrient, type of matte, type of stirring, pulp density, and particle size. In addition, the influence of bioleaching for different periods of time, as a preparatory stage before chemical or biological leaching of the matte, was studied. The optimum conditions for recovery are achieved by way of the two-stage bioleaching process. The degradation of the solid caused by bacterial activity during the first stage is the reason for the high recovery during the second stage.     

化学淋洗法对铀污染土壤的修复效果研究

采用振荡淋洗方法对三种粒径(+2mm、-2mm+0.15mm、-0.15mm)某尾矿库周边铀污染土壤进行去污试验,选用盐酸、硝酸、柠檬酸、草酸为淋洗剂,通过控制淋洗浓度、液固比、时间、温度、混合淋洗等因素来确定较优的淋洗条件。结果表明:各淋洗剂对铀污染土壤的去污效果为草酸盐酸硝酸柠檬酸;当淋洗浓度大于0.5mol/L、淋洗时间大于8h或液固比大于10∶1时,其淋洗效果都逐渐趋于稳定;提高淋洗温度可显著提升淋洗效果;选用草酸+盐酸和草酸+硝酸两组较优混合淋洗组合对全粒径土壤进行淋洗时,土壤中铀去除率均达50%以上,总含铀量分别降至27.15、24.32mg/kg,均达到土壤修复目标(40mg/kg)。     

Column bioleaching of a low grade nickel-bearing sulfide ore containing high magnesium as olivine,chlorite and antigorite

This work investigates the bioleaching of Jinchuan low grade nickel-bearing sulfide ore containing rather high levels of olivine, chlorite and antigorite (MgO 30–35%) present in the main gangue minerals using a mixed mesophiles which are composed of Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans. It aims to test the technical feasibility to recover valuable metals from Jinchuan low-grade nickel-bearing sulfide ore by bioleaching process. The tolerance of the mixed bacteria to Mg²⁺ could be improved markedly from 10 g/L to 25 g/L after nearly 2 years adaptation. A nickel recovery of 91% and a cobalt recovery of 81% were achieved in 312 days column leaching process including 60 days acid pre-leaching stage and 252 days bioleaching stage.     

Uranium sorption from phosphoric acid solutions using selective ion exchange resins: Part II. Kinetic studies

Experiments have shown that the sorption of uranium from strong phosphoric acid solutions onto four D2EHPA/TOPO based ion exchange resins and one aminophosphonic acid resin is particle diffusion controlled in the uranium concentration range 42–780 μM. Interdiffusion coefficients of about 10^?12 m²s^?1 were obtained for D2EHPA/TOPO resins and 0.14 × 10^?12 m²s^?1 with the aminophosphonic acid exchanger at 20°C in 3 M H₃PO₄. Both homogeneous particle diffusion, based on Fick's Law, and the ash layer diffusion model fitted the kinetic measurements.     

砂岩铀矿围岩中性条件下对铀的吸附试验

砂岩型铀矿地浸采铀体系中,溶解铀在水岩界面发生的吸附作用对铀的浸出造成一定影响。为研究CO_2+O_2中性地浸条件下含矿层砂岩介质对溶解铀的吸附特征,采用取自新疆蒙其古尔铀矿床围岩和含铀浸出液,在实验室开展了不同粒径介质和不同固液比的吸附试验。结果表明,不同粒径介质对铀的平衡吸附量介于11.62～20.28mg/g,铀的平衡吸附量以及吸附率与粒径负相关;不同液固比试验条件的平衡吸附量介于10.07～18.23mg/g,铀的平衡吸附量与液固比正相关,铀的吸附率则与液固比负相关。围岩对铀的吸附动力学特征符合粒内扩散模型。试验结果可以为地浸采铀溶质运移模拟过程中吸附模型及其参数的确定提供依据。     

Bioleaching of apatite rich low grade Indian uranium ore

Abstract

Uranium ore from Narwapahar Mines, UCIL contains 0·047% U₃O₈ with some refractory minerals and high apatite (5%) results in a maximum 78% recovery through conventional processing at UCIL, with a fairly high consumption of sulphuric acid and pyrolusite, and loss of uranium as uranium phosphate. To avoid usage of non-ecofriendly oxidants, obviate the influence of phosphate and improve the overall process output of uranium, an alternate extraction technology using microbial isolate(s) is elucidated in this study. A. ferrooxidans isolated from Narwapahar mine water was used in bioleaching of uranium from this apatite rich low grade uraninite ore. Optimum uranium biorecovery of 96% is achieved at 10% pulp density (w/v), pH 1·7 and 35°C in 40 days with the fine particles of <45 μm size. Under the optimum condition at pH 1·7, rise in redox potential is recorded to be 594–708 mV in 40 days. Bioleaching of uranium seems to follow the indirect mechanism of leaching with the involvement of Fe(III) biogenically generated by Acidithiobacillus ferrooxidans (A. ferrooxidans). Uranium recovery was also examined using another mesophilic isolate of Leptospirillum ferrooxidans (L. ferrooxidans) which showed 98% uranium leaching at 40°C, which shows the possibility of improving the kinetics of the process. The high R² values in the temperature range (298–308 K) indicated uranium dissolution by the chemical reaction occurring at the ore surface with Fe(III) generated biogenically, with E_a value of 28·3 kJ mol^?1. The mechanism of uranium bioleaching is also elucidated with X-ray diffraction phase identification of the leach residues with time, followed by observing the surface morphology through SEM at varying temperatures.

Le minerai d’uranium des Mines de Narwapahar, d’UCIL, contient 0·047% d’U₃O₈ avec quelques minéraux réfractaires et une teneur élevée en apatite (5%). On note une récupération maximale de 78% par traitement conventionnel à UCIL, avec une consommation relativement élevée d’acide sulfurique et de pyrolusite, ainsi qu’une perte d’uranium sous forme de phosphate d’uranium. Afin d’éviter l’utilisation d’agents oxydants non écologiques, de prévenir l’influence du phosphate, et d’améliorer la production globale d’uranium du procédé, dans cette étude on examine une autre technologie d’extraction utilisant un (des) isolat(s) microbien(s). On a utilisé A. ferrooxidans, isolée de l’eau de mine de Narwapahar, pour la biolixiviation de l’uranium de ce minerai pauvre en uraninite et riche en apatite. La bio récupération optimale de l’uranium de 96% est obtenue à 10% PD (poids/volume) au pH de 1·7 et à 35°C en 40 jours avec les particules fines d’une taille <45 μm. Sous la condition optimale d’un pH de 1·7, on a enregistré l’augmentation du potentiel rédox à 594–708 mV en 40 jours. La biolixiviation de l’uranium semble suivre le mécanisme indirect de lixiviation avec l’implication de Fe(III) engendré bio génétiquement par A. ferrooxidans. On a également examiné la récupération de l’uranium en utilisant un autre isolat mésophile de L. ferrooxidans, qui a montré une lixiviation de 98% de l’uranium à 40°C, ce qui montre la possibilité d’améliorer la cinétique du procédé. Les valeurs élevées de R² dans la gamme de température (298–308 K) indiquaient que la dissolution de l’uranium par réaction chimique se produisait à la surface du minerai avec Fe(III) engendré bio génétiquement, à une valeur de Ea de 28·3 kJ mol^?1. Le mécanisme de biolixiviation de l’uranium est également examiné avec l’identification de phase par XRD des résidus de lixiviat en fonction du temps, suivi par l’observation de la morphologie de la surface au moyen du SEM, à des températures variées.     

酸度及酸化介质对铀矿石微生物浸出酸化的影响

通过室内柱浸试验,研究了溶浸液加入硫酸的浓度和酸化介质类型对铀矿石生物浸出酸化阶段的影响。结果表明,当初始硫酸浓度相同时,尾液比清水酸化时间短、耗酸率低,两者浸铀率相差不大,尾液比清水的累计净铁浸出量小,但后期差值逐渐缩小。尾液介质酸化时,随着初始酸度的增大,酸化时间缩短,累计净铁浸出量增加,但耗酸率增高,累计铀浸出率增大。合适的方案为酸化阶段采用尾液介质、40g/L初始硫酸浓度酸化。     

Study on preferential flow in dump leaching of low-grade ores

Preferential flow in dump leaching of low-grade ores was investigated in this paper. The production of the dump leaching plant at Dexing Copper Mining in China was significantly influenced by preferential flow due to the heterogeneity of the ores in dump. Surface tension, negative pore water pressure, matrix suction and permeability of dump were found to be correlated to particle size. Preferential flow, which occurred in the fine and coarse region, was determined by solution application rate. Experiments showed that preferential flow happened in the fine region at an application rate below 1070 L/m² min. Experiment of solute transportation under preferential flow was conducted by selecting NaCl as solute. The NaCl concentration of the outflow from the coarse region was greater than that of the fine region. The leaching rate increased slowly as the leaching process proceeded because NaCl dissolved in the immobile water could only be leached through diffusion. The percentage recovery of coarse region surpassed 100%. The preferential flow within the fine region under the condition of small application rate was confirmed.     

Kinetics of sphalerite bioleaching by Acidithiobacillus ferrooxidans

In the present study, the effect of some important parameters including particle size, pulp density and temperature on the rate of Zn dissolution from sphalerite concentrate by Acidithiobacillus ferrooxidans was investigated. The highest rate of sphalerite bioleaching was obtained at particle size, pulp density and temperature of 38–150 μm, 4% wt/vol and 33 °C respectively. The formation of a product layer over sphalerite concentrate particles was confirmed by SEM images whereas XRD, EDS and BET analysis showed that this layer is composed of elemental sulfur and is non-porous. Based on these results, it was decided that a kinetic model in which the rate of Zn dissolution is limited by diffusion of ions through a non-porous product layer is appropriate to describe the sphalerite bioleaching process. Determinations of ferrous iron ion concentration during bioleaching showed that the concentration of this ion varies significantly during bioleaching and hence the kinetic model was revised to take account of this fact. The predictions of this model had a good compatibility with the experimental data and the value of activation energy was determined as 39 kJ/mol.