Copper Dissolution Rate Research Articles

Study of a Copper Oxide Leaching in Alkaline Monosodium Glutamate Solution

Oxide copper minerals are commonly extracted via acidic leaching, using acids such as H2SO4, HCl, or HNO3. These strong acids are the most widely used because of their high dissolution kinetics. However, their main concern is the high acid consumption because copper oxide deposits contain large amounts of acid-consuming gangue. This paper proposes using an alternative aqueous alkaline monosodium glutamate (MSG) system to leach copper oxide minerals. Tenorite (CuO) was used as the copper oxide mineral under study. The influence of process variables (such as temperature and glutamate concentration) and kinetics of this system on copper leaching from tenorite were studied. The results showed that temperature has a significant effect on copper dissolution rates. Increased temperature from 15 °C to 60 °C enhanced the copper extraction from 9.1% to 97.7% after 2 h. Leaching kinetics were analyzed using the shrinking core model (SCM) under various conditions, indicating that the leaching rate presented a mixed control. This method, however, fails to describe leaching for broad particle sizes due to its requirement for single-sized solid grains. This study demonstrated that a large particle size distribution in tenorite supported a successful extension of the SCM for leaching it from mixed glutamate solutions. The activation energy for the 15–60 °C temperature range was calculated to be 102.6 kJ/mol for the chemical control.

The ultrasound leaching kinetics of copper in the H2SO4 dissolution process

ABSTRACT The atmospheric immersion copper dissolution method, commonly employed in the current copper foil production process, is confronted with challenges such as low oxidation ability and the formation of passivation layers on the copper surface. These issues result in slow copper dissolution rates, significantly restricting copper foil production. To overcome this limitation, ultrasound is used to improve the copper dissolution process. The impact of ultrasound on the rate and kinetics of copper dissolution in a sulfuric acid solution was studied. Various factors, including ultrasound power, temperature, Cu2+ concentration, sulfuric acid concentration, and air flow rate, were analysed to assess their influence on the rate of copper dissolution. The optimised dissolution conditions were determined to be 30 g/L Cu2+, 120 g/L sulfuric acid, 300 mL/min air flow, 60°C, and 300 W ultrasonic power. The copper dissolution rate is 1.96 times higher when ultrasound is applied compared to conventional conditions. According to the kinetic study, ultrasound reduced the apparent activation energy from 61.12 kJ/mol to 46.44 kJ/mol, significantly lowering the potential barrier for copper dissolution. This study provides valuable insights for accelerating the dissolution process of copper using ultrasound-assisted technology.

Rotating disc method to study the dissolution kinetics of copper metal in citric acid and hydrogen peroxide

This study reports the kinetics of copper metal dissolution in citric acid-hydrogen peroxide solution using the rotating disc method. The effect of the concentration of citric acid as well as hydrogen peroxide, stirring speed, disc surface area, and temperature was investigated. The concentration of hydrogen peroxide (0.25–1.5 mol/L) has a strong effect on the dissolution rate (mg/min) of copper with a reaction order of 0.92, compared to a reaction order of 0.42 with respect to the concentration of citric acid (0.125–1.5 mol/L). The reaction rate is directly proportional to the disc area (A) and square root of the disc rotation speed (ω1/2), as expected from the Levich equation. The activation energy of 33 kJ/mol, in the temperature range 30-60 °C is also comparable with the values reported in previous studies.

Intensification of the rate of heat and mass transfer at the wall of a stirred tank reactor by integrating a helical coil turbulence promoter with the tank wall

ABSTRACT The influence of a helical coil turbulence promoter on liquid-solid mass transfer rates in a stirred tank was investigated using a technique that involved measuring the rate of diffusion-controlled copper dissolution in acidified dichromate. The study examined the effects of helical coil tube diameter (d), helical coil pitch (p), impeller rotation speed, impeller geometry (axial and radial), the presence of baffles, and solution physical properties. The presence of the helical coil near the reactor wall significantly enhanced mass transfer rates, with a factor ranging from 1.01 to 2.48. This improvement was accompanied by a corresponding increase in the volumetric mass transfer coefficient (kA), ranging from 2.68 to 4.55, depending on operating conditions. Further analysis revealed that the average mass transfer coefficient increased with decreasing coil tube diameter, while coil pitch had a minimal impact. Additionally, radial flow turbines demonstrated superior mass transfer performance compared to axial flow turbines. The presence of baffles also promoted higher mass transfer rates compared to unbaffled reactors. The experimental data were successfully correlated using dimensionless correlations, emphasizing the significance of these correlations in scaleup and design optimization of catalytic stirred tank reactors with efficient cooling systems.

Properties governing the flow of solution through crushed ore for heap leaching: Part III – Low-permeability ores

Heap leaching is used extensively for the processing of low-grade copper and gold ores. If the ore has low permeability, it may lead to underperformance or even project failure. Poor permeability is caused by a high fines content, resulting in a high steady-state moisture hold-up which causes the bed to operate close to saturation. The problem of low permeability can be addressed by either desliming (removal of the fines by wet screening), or by agglomeration (binding the fines together) with a cementitious binder. Fines removal by desliming is shown to reduce the steady-state moisture hold-up, resulting in the bed operating further away from saturation and increasing the maximum solution application rate. Agglomeration with Ordinary Portland Cement modified with additives resulted in fine particles binding together as lumps or coatings onto coarser rocks. These bonds were not destroyed after prolonged exposure to dilute sulphuric acid, due to the pozzolanic properties of the additives (e.g. fly ash), which cause cementitious Ca-bonds to be substituted with more stable Al- or Mg-bonds. Agglomeration with cementitious binder was also found to reduce slumping in leach column tests. This resulted in a higher bed porosity, higher limits on the solution application rate and higher copper dissolution rates. Agglomeration with modified cement may provide a novel, cost-effective method for the treatment of low-permeability ores in acid medium (e.g. copper, uranium and nickel), since cement agglomeration has only been applied commercially in alkali medium (e.g. cyanide solutions for gold ores) to date. Desliming is less attractive due to the high losses of the target metal to the fines.

Bioleaching of chalcopyrite using native Acidithiobacillus ferrooxidans isolated in a mining area in Kitwe Zambia

This study aimed to assess the influence of the physical-chemical factors (particle size, shake flask speed, starting pH, and pulp density) in bioleaching of Zambian chalcopyrite using a novel native isolated Acidithiobacillus ferrooxidans strain DJN1 2021 from samples collected within mining area at Copper Nkana slag dump also known as the Black Mountain in Kitwe, Copperbelt Province in Zambia. The bacterium isolation was done using the modified 9 K selective media and was identified as A. ferrooxidans by using conventional procedures and 16S rRNA gene sequencing. The resulting sequences were analyzed by trimming and generating consensus sequences using Bio-edit software. Blasting results produced a significant alignment of 99.6% similarity with the corresponding sequences of A. ferrooxidans in GenBank. The phylogenetic analysis entails that the isolated strain was identified as A. ferrooxidans and named A. ferrooxidans strain DJN1 2021 with accession number MZ713091. Bioleaching of chalcopyrite (CuFeS2) by A. ferrooxidans (DJN1 2021) was conducted in shake flasks (100 ml) with a 9 K medium. The experiments were tested to optimize the initial pH, particle size, pulp density, and shake flask speed in the recovery of copper from its ore. The results revealed that all of the factors significantly influence the bioleaching process. When the initial pH was 1.8, copper was extracted at the rate of 30.6% within 30 bioleaching days. This was the maximum dissolution observed. The effect of revolution speed in the three different shake flask speeds (i.e. 50 rpm, 90 rpm, and 150 rpm) showed a significant difference in the rate of copper dissolution. A marked difference was observed between shake flask speeds of 50 rpm and 90 rpm with dissolutions of 29.4% and 30.0% respectively. In experiments to look into the effect of particle size, two size fractions were subjected to bioleaching on a shake flask, i.e. (<45 and 45-<63) µm. Results showed that the (45-<63) µm size fraction gave the highest copper extraction of 29.2%. A pulp density of 6% produced the highest extraction of 32.6%. These findings reveal that this novel native A. ferrooxidans strain DJN1 2021 has the potential to bioleaching of copper from chalcopyrite upon optimization in a bioreactor.

Enhancement of copper metal dissolution in sulfuric acid solution with oxygen and ultrasound

A new method for copper metal dissolution by simultaneous use of oxygen and ultrasound was proposed to enhance the copper dissolution rate in sulfuric acid (H2SO4). The influence factors such as ultrasonic power, oxygen flow rate, reaction temperature, initial copper ion (Cu2+) and H2SO4 concentration was studied to study the dissolution behaviour of copper metal. The dissolution rate of Cu could reach 7.52 g h−1 L−1 after the ultrasonic strengthening, which is 1.83 times higher than that without ultrasonic irradiation (4.109 g h−1 L−1). The study of leaching kinetics found that the Cu leaching process with and without ultrasound were both controlled by surface chemical reaction. The ultrasound could significantly reduce the apparent activation energy of the leaching reaction from 43.52 kJ mol−1 to 28.40 kJ mol−1. Characteristics revealed that the cavitation effect of ultrasound could increase the specific surface area of copper metal and oxygen bubble, and enhance the oxidizing capability of this leaching system, which is beneficial for the dissolution of Cu. Therefore, ultrasonic-assisted technology has provided novel insights for the hydrometallurgical recovery of copper.

Phenomenological Model of SEI Formation and Growth Leveraging Real-Time Expansion Measurements

Every commercial lithium-ion battery undergoes formation at the end of the manufacturing process [1]. The formation process is time and capital-intensive, motivating battery manufacturers to develop new formation recipes to decrease formation time while preserving battery lifetime and safety [2]. Yet, despite its importance, a general framework for modeling formation of commercial lithium-ion battery systems is lacking, hindering the innovation cycle. While first-principles solid electrolyte interphase (SEI) formation modeling approaches exist [3], such models are often computationally expensive and challenging to validate, limiting their application towards predicting macroscopic variables relevant to commercial lithium-ion batteries such as capacity loss and resistance growth over life. Semi-physics based (i.e. semi-empirical, or phenomenological) approaches are popular [4], but such models are often parameterized using cell data collected after formation has already completed, making them unsuitable for capturing the initial stages of the SEI formation process.This work presents a framework for developing semi-physics based models of SEI formation and growth dynamics for use in commercial lithium-ion battery systems. The model enables real-time prediction of lithium consumption during the formation (i.e. first charge) process, which can be extended to track the lithium consumption over the entire lifespan of the cell. By explicitly considering the electrolyte reduction reaction dynamics during the first cycle, the model enables the study of how different formation protocols influence SEI passivation properties [5] and hence battery lifetime. The model leverages half-cell near-equilibrium potential curves to track the evolution of lithium stoichiometries and electrode potentials at each electrode, during and after the formation process. The model thus enables real-time tracking of the SEI-forming electrolyte reduction rates which can be used to estimate the quantity of lithium consumed to create the SEI. Model parameters are tuned against experimental electrode expansion measurements collected on NMC622|graphite pouch cells (Figure 1), which resolves both the reversible (i.e. lithiation-induced) and irreversible sources of electrode expansion [6],[7]. Model-predicted lithium consumption rates and electrode expansions are validated against an experimental dataset consisting of three different formation protocols which includes cycle life testing until the end of life.The modeling framework we propose enables practical pathways for bridging the electrochemistry of battery formation to macroscopic variables related to battery safety and lifetime, including total capacity loss, resistance growth, gas generation (during SEI and due to electrolyte oxidation at the positive electrode), and copper dissolution rates.[1] S. J. An, J. Li, C. Daniel, D. Mohanty, S. Nagpure, and D. L. Wood, “The state of understanding of the lithium-ion-battery graphite solid electrolyte interphase (SEI) and its relationship to formation cycling,” Carbon N. Y., vol. 105, pp. 52–76, 2016.[2] Y. Liu, R. Zhang, J. Wang, and Y. Wang, “Current and future lithium-ion battery manufacturing,” iScience, vol. 24, p. 102332, Apr. 2021.[3] A. Wang, S. Kadam, H. Li, S. Shi, and Y. Qi, “Review on modeling of the anode solid electrolyte interphase (SEI) for lithium-ion batteries,” npj Computational Materials, vol. 4, no. 1, 2018.[4] L. von Kolzenberg, J. Stadler, J. Fath, M. Ecker, B. Horstmann, and A. Latz, “A four parameter model for the solid-electrolyte interphase to predict battery aging during operation,” J. Power Sources, vol. 539, p. 231560, Aug. 2022.[5] P. M. Attia, S. J. Harris, and W. C. Chueh, “Benefits of fast battery formation in a model system,” J. Electrochem. Soc., vol. 168, no. 5, p. 050543, 2021.[6] P. Mohtat, S. Lee, J. B. Siegel, and A. G. Stefanopoulou, “Towards better estimability of electrode-specific state of health: Decoding the cell expansion,” J. Power Sources, vol. 427, pp. 101–111, July 2019. Figure 1

Modeling the distribution of an adsorbing solute in a catalyzed column

• Ethylene Thiourea (ETu) is a model catalytic reagent used to leach copper from chalcopyrite . • ETu interacts with the bed of ore as shown by comparison to Cu and Li which are inert. • A 2-D axisymmetric model of an adsorbing, reacting solute is used to explain ETu curves. • The Redlich Peterson adsorption isotherm explains the ETu curves generated. • The 2-D model is validated for different concentrations of ETu, flow rates and heights of column. Catalytic solutes have been reported to significantly enhance dissolution rates of copper from chalcopyrite. Ethylene thiourea (ETu), a thiocarbonyl compound which has been shown to have such a catalytic effect, is used as a model solute to study the distribution of solute in a column of crushed ore under a point source to simulate the effects of a single drip emitter. Steady state infiltration tests of ETu solution are performed to generate ETu breakthrough curves which are compared with curves from metal ions such as copper and lithium to estimate solute transport properties such as adsorption and reaction. The Redlich-Peterson isotherm is used successfully to describe the adsorption behavior of ETu in a column of crushed ore. A 2D axisymmetric model of solute transport is used to estimate adsorption and reaction rate constants by analyzing the sensitivity of model break through curves and comparing them to experimental results. Further, the model populated with the computed parameters is used to estimate ETu breakthrough curves resulting from varying input concentrations, column heights and infiltration rates.

Copper recovery from unground printed circuit board by biogenic ferric at high solid/liquid ratio

• Biogenic ferric sulphate leaches Cu from large PCB pieces at high solid–liquid ratio. • A bioreactor that regenerates the spent ferric ion assits the leaching. • Bioreactor operated continuously without showing inhibition problems. In this work, the recovery of Cu from large waste printed circuit board ( PCB) pieces by biogenic ferric sulphate at high solid to liquid ratio was studied. PCB parts were packed in a column and biogenic ferric was constantly recirculated. A high oxidation reduction potential (ORP) decrease was observed in ferric leaching due to ferric ion consumption; this drop caused a slower copper dissolution kinetics. After 25 days, 62.2% of copper was leached from PCBs column. PCBs column was connected to a flooded packed-bed (FPB) bioreactor to study the biological regeneration of ferric ion consumed in chemical reaction. The bioreactor connection enabled working at a constant ORP (700 mV vs. Ag/AgCl) during the whole test time. The improvement of oxidising conditions hugely increased copper dissolution rate, reaching 90% of copper recovery after 25 days. The FPB bioreactor operated continuously without showing inhibition problems and generating a leaching liquor with a high and constant ORP. The novel proposed configuration consists of a chemical reactor, where large PCBs pieces are piled at a high solid load, connected to a FPB bioreactor that regenerates the spent ferric ion enabling the leaching without reagents consumption, is a simple, inexpensive, low energy consumption, eco-friendly and effective system to recover copper from PCBs.

Studying the Effect of Butanol on the Anode Behavior of Copper in Phosphoric Acid Solutions

The anode behavior of the copper electrode immersed in butanol phosphate electrolytes has been studied. The polarization dependences of the electrode allowed us to detect the sections that correspond to the passive and active states of copper and we also established the zone of the combined behavior of the processes of the copper dissolution and oxygen release. It was also established that a butyl alcohol contributes to an abrupt decrease in current densities in the entire region of anode potentials. The addition of butanol conditions the disappearance of current oscillations that can be seen on polarization dependences in phosphate solutions. Evidently, a decrease in the current densities is a consequence of the butanol adsorption on the copper surface and its participation in the formation of passive films. The specific features of the copper passivation in butanol phosphate electrolytes are characterized by the appearance of the explicit current peak that separates active and passive state zones at the ratio of C4H9OН:H3PO4 =1:3.As the alcohol-to-acid ratio increases, the peak gradually decreases. The addition of butanol has no determining influence on the potential value that corresponds to the started oxygen release. Currentefficiency values for the copper dissolution depend on the anode current density ja and the electrolyte composition. An increase in ja results in a decreased current efficiency value. An increase in the С4Н9ОН content has a similar action. Maximum current efficiency values are observed at ja=0.5–2 А∙dm-2, and they correspond to the active copper state. The dependences obtained for the copper dissolution rate allowed us to establish that υрalso increases with an increase in the current density up to ja=20 А∙dm-2. The copper treatment quality depends on the current density and the electrolyte composition. The solutions with the ratio of C4H9OН:H3PO4=2:1fail to provide a high quality treatment; the surface is not glossy and it has grinding traces. A high-quality treatment is observed in the electrolytes with the ratio of C4H9OН:H3PO4 =1:2 and lower. The electrochemical polishing in such solutions results in the glossy copper surface with the smoothed relief and it has no polishing traces.

Iodine-assisted chalcopyrite leaching in ferric sulfate media: Kinetic study under fully controlled redox potential and pH

The addition of iodide has been found to significantly accelerate chalcopyrite leaching in ferric sulfate media at ambient conditions. Solution potential is the principal factor determining the leaching performance through controlling the iodine speciation. In order to develop a kinetic equation that incorporates the iodine speciation, a series of leaching tests were carried out in specially-designed sealed reactors that allows the solution potential together with other leaching parameters to be fully controlled. The experimental results showed that the rate of copper dissolution was increased by increasing the solution potential in the range of 669 to 769 mV vs. SHE), increasing the total iodide concentration in the range of 50 to 200 mg/L, and increasing the temperature between 25 and 40 °C. The formation of elemental sulfur and jarosite did not hinder the leaching reaction. A kinetic model was developed that relates the rate of copper extraction to the solution potential with a reaction order of 0.32, the diiodine concentration with a reaction order of 1.17, and temperature with an activation energy of 43.1 kJ/mol. The kinetic analysis supported that the leaching process was controlled by surface chemical reaction.

Kinetic Model for Dissolution of Cement Copper in Sulfuric Acid Solutions Containing Cupric Ions

In this paper, the dissolution kinetics of cement copper powder in sulfuric acid solutions containing cupric ions was examined. It was observed that the dissolution rate of copper increased with increasing the acid concentration, temperature, and stirring speed. It was determined that the dissolution rate of copper enhanced with increasing the cupric ion concentration up to 0.025 M. It was found that the temperature and concentration of cupric ion had more considerable effects on the dissolution of copper powder. The kinetic analysis of the process was performed, and it was observed that it fits the first order pseudo-homogenous reaction model. The activation energy was calculated to be 31.1 kJ/mol.

Experimental and Kinetic Modeling Investigation of Copper Dissolution Process from an Iranian Mixed Oxide/Sulfide Copper Ore

In the present work, the leaching behavior of copper from an oxide/sulfide ore was assessed in two work phases including process optimization and kinetics modeling. In the first phase, the individual and synergistic impacts of the influential parameters such as sulfuric acid concentration, liquid/solid ratio, pulp mixing rate, temperature, and contact time were investigated on the dissolution rate of copper using response surface modeling. The findings demonstrated that the linear effects of dissolution time and temperature and the quadratic impact of acid concentration had the largest influence on the recovery and the linear impact of stirring speed had the least degree of importance. Process optimization was also performed utilizing the desirability function approach and more than 88.17% copper was recovered at the optimum conditions: ~ 17% acid concentration, ~ 11.3 mL/g liquid/solid ratio, ~ 390 rpm stirring speed, 50 °C temperature, and 60 min leaching time. In the second phase, the leaching kinetics was examined by heterogeneous shrinking core models and it was realized that diffusion through product layer was the dissolution rate controlling step with the activation energy of 28.92 kJ/mol and frequency factor of 6.155 min−1. Ultimately, a mathematical kinetics model was developed and suggested to understand the leaching process. a 3D response surface graphs displaying the synergistic effects between “temperature and liquid/solid ratio” and “stirring speed and leaching time” on the leaching recovery of copper; b the optimum conditions of influential factors; c plot of diffusion through product layer versus leaching time for temperature effect.

Modeling study of the bio-dissolution of copper concentrate in a continuous bioreactors system

The objective of the present research was to use two different bacterial cultures in continuous tank bioleaching circuits and to use this knowledge for mathematical modeling of the chalcopyrite bioleaching kinetic. Using three different particle size distributions (PSD) with the indices (d80) of 45, 32 and 16 µm of a chalcopyrite concentrate from the main Iranian copper processing plant and two types of bacteria, one and two-step continuous tests were performed in stirred tanks. In the first phase, tests were performed at 50 ± 2 °C using moderate thermophilic bacteria. The second part consisted of two-step continuous tests at 50 ± 2 °C using moderate thermophilic bacteria in the first reactor and extremely thermophilic bacteria at 65 ± 2 °C in the second reactor. The results of one-step continuous tests indicated that the highest rate of copper dissolution (5.21 g/l·day) resulted from test using feed with d80 = 16 µm. The Field Emission Scanning Electron Microscopy (FE-SEM) analysis of bioleaching residue indicated that the surface of particles was mostly covered with secondary layers. The Energy-dispersive X-ray spectroscopy (EDS) analysis of the formed layer revealed high concentrations of iron, sulfur and a certain amount of potassium. The results of two-step tests showed that under the specified conditions of this study, about 95% of copper was leached and transferred to solution. The analysis of FE-SEM and EDS residue indicated that the particle surface activity at this stage was higher than that of a single-step system probably due to the high temperature of the reaction medium (50 °C for the first reactor and 65 °C for the second reactor) and the presence of Oxidation-Reduction Potential (ORP) of solution in the range between 360 and 480 mV, Ag/AgCl. The results of the mathematical modeling for predicting the PSD of existing particles in the one -step reactor indicated that the maximum rate of size reduction kinetics was related to the first five days. The maximum difference between the experimental and predicted results was 19%. In case of two-step system, the reduction in particle size between the first and fifth days was significantly more than the next days. From the results of this study, it can be pointed out that firstly the two-steps bioleaching of chalcopyrite concentrate is more effective than the one-step and the reduction of particle size distribution can be predicted using the presented mathematical modeling.

Digital Holographic Study of pH Effects on Anodic Dissolution of Copper in Aqueous Chloride Electrolytes

The anodic dissolution of copper in chloride electrolytes with different pH has been investigated by using polarization measurements and digital holography. In acidic and neutral NaCl solutions, the oxidation processes of copper are almost the same: copper firstly dissolves as cuprous ions, which then produces the CuCl salt layer. The dissolution rate in the acidic solution is a little higher than that in the neutral. However, the mechanism is quite different in the alkaline NaCl solution: copper turns passive easily due to the formation of a relatively stable Cu2O film which results in pitting, and the dissolution rate of copper decreases before pit initiation.

Microstructural and electrochemical properties of TiAlN(Ag,Cu) nanocomposite coatings for medical applications deposited by dc magnetron sputtering

AISI 420 stainless steel is currently used in the manufacture of surgical and dental instrumentation due to its hardenability, acceptable biocompatibility and suitable resistance to corrosion in low acid or basic medium. However, it is necessary to increase the wear and corrosion resistance of this type of steel when it is used in certain biomedical applications. Therefore, multiple surface modification strategies have been used in order to overcome these drawbacks in the properties of this material. In this work, TiAlN coatings doped with Ag and Cu nanoparticles in four different quantities (11 at.% to 20 at.%) were deposited onto 420 steel by DC magnetron sputtering technique. The microstructure, and chemical and phase composition, were analyzed by scanning and transmission electron microscopy (SEM/TEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction, while roughness was determined using atomic force microscopy (AFM). The electrochemical behavior of the coatings was evaluated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. A reduction in the corrosion current density of the steel substrate was evident once it was superficially modified with the TiAlN matrix coating, which formed a protective barrier to the corrosive medium. The TiAlN(Ag,Cu) coatings developed superior electrochemical activity to the TiAlN matrix, and consequently exhibited higher corrosion current densities. This behavior was accentuated with increased Ag/Cu content in the coating, and it was correlated mainly with the increase in the dissolution rates of silver and copper to the surrounding medium. This suggests a potential bactericidal effect of this kind of coating, which might be considered for potential application in surgical and dental instrumentation.

Effect of carbonaceous matter on copper behavior in bioleaching from waste printed circuit boards

In this paper, the effects of humic acid, activated carbon and graphite on the bioleaching behavior of copper from waste printed circuit boards (WPCBs) with HQ0211 bacteria strain have been investigated. The compatibility test and the optimal additive amount of carbonaceous matter and the mechanism analysis were studied. It was demonstrated that humic acid has good compatibility with microorganisms. Humic acid can significantly promote the dissolution rate of copper with appropriate amount. The addition of activated carbon and graphite could inhibit the growth of bacteria. And the inhibition was weakened on the bioleaching process. The optimal condition of bioleaching copper was WPCBs 50 g L−1, initial pH 1.5, bacterial leaching time 7 days, the leaching rate of copper increased by 11.08%, 8.71% and 6.84% respectively in the experimental group with proper dosage of humic acid, activated carbon and graphite.

Development of a Kinetic Model of the Bacterial Dissolution of Copper Concentrate

The present study introduces a new approach to understand the copper dissolution rate and to find an adapted mathematical statement for particle shrinkage rate in a batch bioleaching system. Four size classes of a chalcopyrite concentrate, namely [D1 : (−54 + 44)μm, D2 : (−44 + 38)μm, D3 : (−38 + 25)μm and D4 : (−25)μm], were used in the batch bioleaching tests by applying a mixed culture of moderately thermophilic microorganisms. The pulp density and temperature were 8 (%w/v) and 50 °C, respectively. Findings delineated that the bioleaching time can be divided into two specific time intervals: first, the surface reactions were the prevailing controlling step; second, the prevailing mechanism was diffusion through the product layer, whereas the overall rate of the process may be related to both through a Q factor using a mixed model. A mathematical model was developed based on particle size distribution (PSD) and a kinetic model. Experimental validation of the mixed model was accomplished by the representative sample with d80 = 54 microns. Results showed that the PSD of the specific sample was in good agreement with Rosin–Rammler function. Besides, the simulation result of the conversion fraction had the best conformity with the experimental data (with a maximum error of approximately 7%). This paper should be considered as an initial part of a larger, global model for chalcopyrite concentrate bioleaching.

Enhanced bioleaching of copper from circuit boards of computer waste by Acidithiobacillus ferrooxidans

Computer circuit boards are a major electronic waste containing higher concentrations of copper, gold and silver. These metals may be recovered by bioleaching, an eco-friendly process to recover metals from natural ores. However, the application of the bioleaching to electronic waste is still in the infancy stage. Here, the bioleaching capability of Acidithiobacillus ferrooxidans to extract copper from printed circuit boards was investigated at laboratory scale using shake flasks. The effect of initial pH, amount and size of printed circuit boards, and volume of inoculum on copper dissolution rates were evaluated. Results show that the highest dissolution rate of 32.44% was achieved after 7 days of leaching at initial pH 2.0, 10 g/L of waste printed circuit board, 40% v/v of inoculum for 1 mm size of circuit board. The smallest size of 1 mm induces the higher dissolution rates, which is explained by higher surface area and thus better bacterial adhesion. Also, the copper dissolution rates increase with the inoculum volume. Overall, bioleaching of copper from waste printed circuit boards using Acidithiobacillus ferrooxidans is achievable.