Copper recovery from chalcopyrite concentrate by acidophilic thermophile Acidianus brierleyi in batch and continuous-flow stirred tank reactors

The mechanism and kinetics of bioleaching of chalcopyrite concentrate by the thermophilic archaea Acidianus brierleyi was studied in batch and continuous-flow stirred tank reactors (CSTR). In the batch reactor, the thermophile A. brierleyi solubilized chalcopyrite much faster at 65°C than did the mesophile, Thiobacillus ferrooxidans at 30°C. The chalcopyrite leaching with A. brierleyi was found to take place with a direct attack by adsorbed cells on the mineral surface, the chemical leaching with ferric iron being insignificant. Rate data collected in the batch reactor were analyzed to estimate kinetic and stoichiometric parameters for the growth of A. brierleyi on chalcopyrite. The batch model and the estimated parameter values were used to find optimum levels of initial cell concentration and initial mineral/liquid loading ratio. Simulations based on continuous reactor model and the parameter values were used to predict the leaching fraction as a function of the number of reactors connected in series.     

Bioleaching of Rare Metals from Manganese Nodules by Thiobacillus Ferrooxidans

Manganese nodules, which constitute a potential future resource of rare metals, are composed mainly of oxides of manganese and iron, with various metals such as copper, nickel, and cobalt. Although physical and chemical processes have been developed for extracting the rare metals from manganese nodules, another possible process is the leaching of metals by microbial means.

This paper describes leaching of raw manganese nodules by sulfurous acid and sulfuric acid which are biologically produced by oxidation of elemental sulfur by Thiobacillus ferrooxidans. The bioleaching behavior of each metal from nodules was measured at 30°C and pH 2 in a well-mixed batch reactor. The metal content of the nodules used in this work was 0.29% Cu, 0.49% Ni, 0.27% Co, 16% Fe and 17% Mn by weights. For both the microbial system and the control culture containing no T.ferrooxidans, copper and nickel exhibited close to 100% leaching in two weeks and less than 5% for iron and manganese. On the other hand, leaching of cobalt was markedly accelerated in the microbial system reaching 50% in two weeks compared with the sterile control. The bioleaching rate of cobalt was enhanced as the initial sulfur-liquid loading ratio became higher, but is was practically independent of the nodule size which was less than 330 mesh. Moreover, there was an optimal relation between the bioleaching rate and the initial cell concentration, and the addition of T.ferrooxidans cells in excess of the optimal concentration resulted in a decrease in the leaching rate of cobalt.     

Bioleaching of Metal-Contaminated Soil in Semicontinuous Reactor

Recently, microbial leaching of heavy metals from contaminated soils with indigenous iron-oxidizing microflora has been successfully applied in flask experiments. However, the long hydraulic residence time (HRT) required and the batch mode are not well suited for an industrial scale process. Therefore, this research focused on bioleaching of Zn, Cu, and Mn from a contaminated soil in the semicontinuous mode. Metal leaching experiments were carried out in an 8 L semicontinuous stirred tank reactor (SCSTR) with a soil concentration of 100 g∕L, as well as in 500 mL shake flasks. It was found that bioleaching in the SCSTR entails a reduction of treatment duration (from 10 to 2 days) and an increase in the solubilization efficiency. Metal solubilization efficiency in the SCSTR was 40% for Zn, 47% for Cu, and 34% for Mn. When the volume of the soil suspension remaining in the SCSTR between transfers was small (20% instead of 50%), corresponding to a shorter HRT (2.5 days instead of 4 days), the solubilization efficiencies were reduced. The volumetric oxygen transfer coefficient and the oxygen uptake rate were calculated in the SCSTR for both HRTs tested. The dissolved oxygen concentration below which the microflora does not grow was found to be 0.2 to 0.3 mg∕L, and the concentration below which oxygen is limiting was 0.8 mg∕L.     

An Overview of the Studies about Heavy Metal Adsorption Process by Microorganisms on the Lab. Scale in Turkey

Abstract

Heavy metal ions, Cr(VI), Pb(II), Cu(II), Fe(III) and Ni(II) were removed from synthetic aqueous solutions by using Z. ramigem, an activated sludge bacterium, and R. arrhizus, a filamentous fungus. The adsorption isotherms were developed and it was seen that the adsorption equilibrium data fit both Freundlich and Langmuir isotherms. Heavy metal adsorption on free and immobilized cells was also investigated in various reactor types such as stirred tank reactors (single and multi-stage) and packed bed reactors.     

Biodegradation Kinetics of MTBE in Laboratory Batch and Continuous Flow Reactors

Methyl tert-butyl ether (MTBE) biodegradation was investigated using a continuously stirred tank reactor with biomass retention (porous pot reactor) operated under aerobic conditions. MTBE was fed to the reactor at an influent concentration of 150 mg/L (1.70 mM). An identical reactor was operated as a killed control under the same conditions. Operation of these reactors demonstrated that removal of MTBE was biological and suggests that biomass retention is critical for effective degradation. MTBE removal exceeded 99.99% when the volatile suspended solids concentration in the reactor was above 600 mg/L. Batch experiments conducted using mixed liquor from the porous pot reactor indicated that the individual rates of biodegradation of MTBE and tert-butyl alcohol (TBA) increase with increasing initial concentration. When batch tests were later repeated, the MTBE degradation rates were found to have increased while the TBA degradation rates remained constant. All batch tests confirmed that the degradation rate of TBA governed the overall degradation rate (degradation rate of both MTBE and TBA). The presence of TBA at lower concentrations did not affect the rate of MTBE degradation; however, higher concentrations of TBA did reduce the rate of MTBE biodegradation.     

Mechanism of enhanced bioleaching efficiency of Acidithiobacillus ferrooxidans after adaptation with chalcopyrite

To clarify the role and mechanism of bacterial adaptation in bioleaching, the leaching of chalcopyrite by adapted and unadapted Acidithiobacillus ferrooxidans was compared. Three extrinsic factors (adsorption, tolerance to shearing stress and copper tolerance) in relation to bioleaching were investigated. The results showed that there were significant differences in bacterial attachment and tolerance to shearing stress of unadapted and adapted cells due to the variation of cellular wall component and structure. Consequently, there was significant difference in bioleaching rate between unadapted and adapted bacteria. In addition, some differences of copper accumulation and distribution in adapted and unadapted cells also existed, but this was not one of the key factors that affected their bioleaching rates.     

PAC-Membrane Filtration Process.?I: Model Development

Adsorption is modeled when powdered activated carbon (PAC) is applied in continuous-flow reactors followed by membrane filtration units operated without carbon wastage between backwash events. Four reactor configurations are studied: (1) A membrane reactor dosed with a step input of PAC; (2) a continuous-flow stirred tank reactor dosed with a step input of PAC and followed by a membrane reactor; (3) a plug-flow reactor dosed with a step input of PAC and followed by a membrane reactor; and (4) a membrane reactor dosed with a pulse input of PAC at the beginning of the filtration cycle. A steady-state operation is considered to describe the adsorption process through the continuous-flow stirred tank reactor and plug-flow reactor, whereas adsorption in the membrane reactor is modeled as a non-steady-state process. Adsorption kinetics is assumed to occur by homogeneous surface diffusion, and adsorption equilibrium is described with the Freundlich isotherm model. Analytical solutions of the homogeneous surface diffusion model with no external mass transfer limitation are used to evaluate adsorbate concentrations in the solid phase as a function of time. Part II of this study presents model simulations and verification with experimental data obtained in a bench-scale apparatus.     

The effect of particle size,irrigation rate and aeration rate on column bioleaching of uranium ore

The effect of hydrodynamic factors such as particle size, irrigation rate and aeration rate on the dissolution of uranium by Acidithibacillus ferrooxidans in column reactor was studied. Response surface methodology (RSM) was applied to predict the behavior of effective parameters and their interactions on the bioleaching process. Under the optimum conditions particle size of 5 mm, irrigation rate of 0.34 L/m²/min and aeration rate of 210 L/m²/min, the maximum value of uranium recovery was 63.85% for 19 days. The results from the statistical model and the experimental data showed good agreement and the most effective factor was the aeration rate. The interaction between particle size and irrigation rate has a negative effect and two other interactions have a positive effect on uranium recovery. Analysis of bioleaching residue confirmed the formation of K-jarosite on the surface of particles. The modified kinetic model at optimum conditions showed that cathodic ferric reduction is the rate controlling step on uranium bioleaching recovery.     

Influence of the medium composition and plasmid combination on the growth of recombinant Escherichia coli JM109 and on the production of the fusion protein EcoRI::SPA

Plasmid-free and plasmid-harbouring E. coli JM109 strains were investigated in shaken flasks, stirred tanks in batch and continuous operation. The shaken flask cultivations were performed in M9 minimal medium and in media with various protein supplements. The host hardly grows on M9 minimal medium as opposed to the plasmid-harbouring cells, which grow well on this medium. All of the investigated cells propagate well on protein-containing media. The influence of the combinations of repressor plasmid pRK248cI, the protection plasmid EcoR4 and the production plasmid pMTC48 were determined on the initial specific growth rate of the E. coli JM109 without gene expression, on the yield coefficient of cell growth, acetate concentration and acetate yield coefficient in the yeast extract-containing (HM) medium. The influence of various media on the induction of the gene expression were evaluated. In cultivation media with protein supplement, the growth rate and yield coefficient increased. The variation of the volumetric and specific beta-lactamase activities with the cultivation time were determined in a stirred tank reactor in HM medium. With increasing dilution rate the process performance decreased. Simple relationships exist between the substrate uptake rate and the specific growth rate of the continuous cultivated cells in M9 and HM media. The influence of the dilution rate on the cell mass concentration, colony forming units, acetate formation, yield coefficients of growth and acetate formation, substrate uptake rate, CO2 production rate, ammonium formation rate and beta-lactamase activity in M9 and HM media were determined as well. Carbon balances of the batch and continuous cultivations indicated high carbon recoveries. On account of the higher growth rate of plasmid-harbouring cells than than of the plasmid-free cells, the behaviour of the investigated plasmid-free and plasmid-harbouring E. coli JM109 cells deviates from the published properties of other plasmid-free and plasmid-harbouring E. coli cells.     

Iron ore reduction in a continuously operated multistage lab-scale fluidized bed reactor—Mathematical modeling and experimental results

Industrial-scale fluidized bed processes for iron ore reduction (e.g., FIOR and FINMET) are operated by continuous feeding of ore, while laboratory tests are mostly performed under batchwise operation. The reduction behavior under continuous operation is influenced by both the residence time of the iron ore particles and the reduction kinetics, which is obtained by batch tests. In a mathematical model for such a process, the effect of both phenomena has to be considered. The residence time distribution of iron ore particles in a laboratory fluidized bed reactor was obtained by measuring the response of a step input and described by mathematical models similar to a continuously stirred tank reactor. In the same reactor, reduction tests with continuous feeding of iron ore were performed. Based on batch tests in a fluidized bed reactor, a mathematical model was developed to describe the kinetics of iron ore reduction under fluidized bed conditions. This kinetic model was combined with the fluidized bed reactor model to describe continuous iron ore reduction. In this detailed model, the change of gas composition while rising in the fluidized bed was considered. The degree of reduction and the gas conversion for reactors in series were calculated. The results obtained by the mathematical model were compared with experimental data from the laboratory-scale reactor.     

生物浸出低品位镍铜硫化矿

阐述了氧化亚铁硫杆菌 (TF5)和氧化硫硫杆菌 (TT)浸出金川低品位镍铜硫化矿的机理、过程动力学、工艺条件和反应工程。研究表明 ,含镍磁黄铁矿的细菌浸出以细菌氧化生成的Fe3 +的作用为主 ,浸出速率受表面反应控制 ;镍黄铁矿的细菌浸出以矿物表面吸附菌的作用为主。细菌对Mg2 +离子的耐受浓度因驯化而提高 ,极限浓度可达 15～ 2 0g/L。低品位镍铜矿的细菌浸出过程中 ,pH控制、细菌的初始接种量、矿浆浓度及TF和TT的混合比是影响镍、铜、钴等有价金属元素浸出速率和最终浸出率的主要因素。优化条件下气升式和搅拌式反应器中试验表明 ,优化条件下 ,在生物浸出低品位镍铜硫化矿 ,镍浸出率可达到 92 %～ 94 % ,铜达 4 8%～ 50 % ,钴达 88%～ 91%。     

Mathematical modeling of an exothermic leaching reaction system: pressure oxidation of wide size arsenopyrite participates

In the design of processes involving exothermic reactions, as is the case of several sulfide leaching systems, it is desirable to utilize the energy liberated by the reaction to drive the reactor toward autogenous operation. For optimal reactor design, models which couple leaching kinetics and heat effects are needed. In this paper, the principles of modeling exothermic leaching reactions are outlined. The system investigated is the high-temperature (160 °C to 200 °C) pressure (O2) oxidation of arsenopyrite (FeAsS). The reaction system is characterized by three consecutive reactions: (1) heterogeneous dissolution of arsenopyrite particles, (2) homogeneous oxidation of iron(II) to iron(III), and (3) precipitation of scorodite (FeAsO4-2H2O). The overall kinetics is controlled by the arsenopyrite surface reaction. There was good agreement between laboratory-scale batch tests and model predictions. The model was expanded to simulate the performance of large-scale batch and single-stage continuous stirred tank reactor (CSTR) for the same rate-limiting regime. Emphasis is given to the identification of steady-state temperatures for autogenous processing. The effects of operating variables, such as feed temperature, slurry density, and retention time, on reactor operation and yield of leaching products are discussed.     

生物氧化浸矿反应器的研究进展

生物氧化浸出技术工业应用和发展将过程工程的研究和高效生物浸矿反应器的研制推上一个重要位置。综合分析了搅拌槽式和气升式这两种工业常用生物浸出反应器,指出其不完全适用于生物氧化浸矿,评述了近十年来生物氧化浸矿反应器的现状和发展趋势,总结了反应器设计的一般指导原则,介绍了几种最具开发潜力的反应器。     

活性炭在原生硫化铜矿细菌浸出中对铜与铁离子吸附的影响

通过摇瓶实验,研究了活性炭在原生硫化铜矿细菌浸出中对铜与铁离子吸附的影响。研究结果表明,活性炭浓度和pH值对活性炭吸附铜和铁离子有重要影响,活性炭对铜和铁离予的吸附量随活性炭浓度增加而增加。在原生硫化铜矿石细菌浸出的初始阶段,添加活性炭可以大大加快铜的浸出速度和提高铜的浸出率,在600h内,铜的浸出率可以达到79％,比不添加活性炭时提高了68％。     

A review of rate equations proposed for microbial ferrous-iron oxidation with a view to application to heap bioleaching

In view of the fact that the microbial oxidation of ferrous iron to the ferric form is an essential sub-process in the bioleaching of sulphide minerals, the development of a comprehensive rate equation for this sub-process is critical. Such a rate equation is necessary for the design and modelling of both tank and heap bioleach systems.Most of the rate equations presented in the literature define the specific microbial growth rate using a Monod-type form for ferrous substrate limitation, with further terms added to account for ferric product inhibition, ferrous substrate limitation and inhibition. A few of the published rate equations describe the specific substrate utilization rate in terms of a modified Michaelis–Menten equation and include the maximum yield constant and cell maintenance via the Pirt equation. Other rate equations are based on chemiosmotic theory or an analogy with an electrochemical cell.In the present paper a selection of rate equations are compared against each other by calibrating them against the same set of data and comparing the fits. It was found that none fits the data particularly well and that some of the underlying assumptions need to be questioned. In particular, it appears that ferric inhibition is perhaps not as significant a factor than previously assumed and that rate control by the availability of ferrous is more significant.Some rate equations include terms to account for the effects of temperature, pH, biomass concentration, ionic strength as well as inhibition due to arsenic. In general these effects have been studied in isolation and in ranges not too far off the optimum. Few rate equations combine more than 2 effects and there is no clarity on how a comprehensive model to account for all effects should be constructed.Rate equations have been applied to tank bioleach systems, which usually operate under controlled conditions near the optimum. Heap bioleach systems, on the other hand, often operate far from optimum conditions with respect to temperature, pH, solution conditions, etc., at the same time. The kinetics of such sub-optimal systems are still poorly understood. Future studies should be directed towards the development of a comprehensive rate equation useful for describing the kinetics of heap bioleaching over a wide range of conditions.     

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。     

Separation and recovery of iron and scandium from acid leaching solution of red mud using D201 resin

Red mud is a byproduct of alumina refining of bauxite ores, and is a significant source for extracting scandium. However, a large amount of iron in red mud makes it difficult to recover scandium because Fe(III) and Sc(III) have similar physicochemical properties. In this study, a new method was developed for selective separation of iron and scandium in acid leachate of red mud using D201 resin. Theoretical calculations indicate that the ferric species mainly exists as FeCl₃ or FeCl₄⁻ at chloride concentration above 6.65 mol/L, while scandium still exists as ScCl₂⁺, making it possible to selectively separate iron from scandium through anion resin adsorption. The factors affecting the adsorption of iron and scandium such as chloride concentration, resin dosage, adsorption time, and temperature were evaluated in batch experiments. The Langmuir model was successfully applied to both iron and scandium adsorption, and the maximum adsorption capacities of iron and scandium are 147.06 and 0.95 mg/g, respectively, indicating a significant difference between iron and scandium. Raman analysis further demonstrates that the iron is adsorbed onto D201 resin as FeCl₄⁻ anion.     

The mechanism of elution of gold cyanide from activated carbon

Numerous articles have appeared on the mechanism of the adsorption of gold cyanide onto activated carbon. In contrast, little information is available on the mechanism of elution of the adsorbed gold. It is the objective of this article to formulate such a mechanism on the basis of batch and column elution tests without analyzing adsorbed species on the carbon directly. The presence of spectator cations (M ⁿ⁺) enhances the formation of M ⁿ⁺{Au(CN) ₂ ⁻ } _n ion pairs on the carbon, which in turn suppress the elution of gold cyanide. The dynamics of removal of these cations determine the horizontal position of the gold peak in an elution profile. When the concentration of cations in the eluant is high and no cyanide is present in the solution or on the carbon, very little desorption of gold is observed. The quantitative effect of the concentration of spectator cations on the equilibrium for desorption of aurocyanide can be estimated from the elution profiles for gold and cations. Free cyanide in the eluant, which causes some competitive adsorption of cyanide with aurocyanide, therefore plays a minor role at the elevated temperatures used in industry. A more important effect of cyanide is its reaction with functional groups on the carbon, the products of which passivate the surface for adsorption of aurocyanide, and thereby cyanide promotes the elution of aurocyanide. The degree of passivation, which is determined to a large extent by the temperature of pretreatment, also affects the elution of cations and the degradation/adsorption of cyanide itself. Reactivation of the carbon surface occurs when the adsorbed/decomposed cyanide is removed by the eluant. At high temperatures of pretreatment, such as used in practice, it is not necessary to include a reactivation term in the mathematical model for elution.     

PAC-Membrane Filtration Process.?II: Model Application

The models developed in the first part of this study are applied to predict the removal of 4-nitrophenol by powdered activated carbon (PAC) in a bench-scale reactor. A series of continuous-flow filtration experiments were conducted with different carbon doses to verify the modeling approach when the activated carbon was added directly to the membrane reactor, either as step or pulse input, and when the carbon was dosed as a step input to a continuous-flow stirred tank reactor followed by the membrane reactor. The models predicted well the experimental data for all cases investigated. The verified model was used to investigate the effect of various operating parameters on the efficiency of the adsorption process. This analysis included the effect of filtration time, membrane reactor volume, dosing procedure, and the effect of dosing the carbon in reactors installed in series upstream of the membrane reactor.     

Adsorption Characteristics of Oxide Coated Buoyant Media (ρs<1.0) for Storm Water Treatment. II: Equilibria and Kinetic Models

Divalent metal species adsorption onto a manganese oxide coated polymeric medium (MOPM) was evaluated through batch adsorption experiments using a flow-through batch reactor. In this paper, Part II, the batch equilibrium and kinetic data examined in Part I are modeled using a triple layer surface complexation model and a potential driving second order kinetic model. Surface complexation modeling using FITEQL-TLM generated intrinsic surface acidity constants for the MOPM of log?K?a1int = 3.196 and log?K?a2int = ?5.802. The intrinsic surface reaction constants for Pb(II), Cu(II), and Zn(II) were log?K?Pbint = ?1.91, log?K?Cuint = ?2.53, and log?K?Znint = ?4.45, respectively. A potential driving second order kinetic model was developed to predict sorption of the divalent metal ions onto the MOPM. The general adsorption kinetics for MOPM can be described as a fast reaction occurring within 30 min and a slower reaction continuing from 5 to 15 h. Kinetic results can be interpreted using assumptions of the potential driving second order model that the dominant control forces are the chemical potential of the MOPM activated surface sites and chemical potential of sorbate in the solution.