Mechanism and electrochemical experimental results of bacterial oxidation leaching of gold arsenic containing pyrite

1、 Preface
With the increasingly serious global ecological problems, the drying up of easily selected and easily treated gold ore resources, and the advancement of metallurgical skills, metallurgical skills with low environmental negative effects, good economic benefits, and the ability to effectively handle difficult to treat gold ore have become increasingly valued and possible Refractory gold ore, also known as refractory gold ore or refractory gold ore, refers to gold ore with a direct conversion rate of less than 70% in conventional processes About one-third of gold mineral resources are attributed to refractory gold mines, and currently, refractory gold accounts for 60% of international gold reserves There are many elements that make gold mines difficult to handle, such as gold being wrapped in ultra-fine particles in the carrier gold production, and the ore containing certain elements that inhibit leaching (such as C, As). A large category of difficult to handle gold deposits is gold bearing sulfide ore. Pyrite and arsenopyrite FeAsS (arsenopyrite) are common gold advantages and main uses of high precision ceramic bearings sulfide ores, with gold enclosed in secondary particles. In order to improve the leaching rate of gold from such ores, pre-treatment is necessary. Compared with traditional pre-treatment methods, bacterial oxidation pre-treatment has lower environmental negative effects and better economic benefits. However, due to its own shortcomings, such as long pre-treatment time, exothermic oxidation process, and the toxic effect of arsenic during leaching process on leaching bacteria, its further application is constrained Strengthening the pre-treatment process of bacterial leaching of arsenic containing gold concentrate requires a deeper understanding of the mechanism of bacterial oxidation leaching of sulfide ores. This process is essentially a reaction of bacterial participation in oxidation recovery, involving the relocation of electrons between the interface between the mineral and bacteria adsorbed on the mineral surface, the mineral leaching solution, and the leaching solution suspended bacteria. With modern electrochemical analysis skills, electrochemical signals of the bacterial oxidation process can be obtained, Effectively conduct mechanism research.
2、 Bacterial oxidation pretreatment process for arsenic containing gold concentrate
Various bacteria can be selected for the bacterial oxidation leaching process, with the most widely used being the strain mainly composed of Acidithiobacillus ferrooxidans At. f Currently, there are three perspectives on the mechanism of bacterial leaching: direct action, direct action, and combined action. Taking Thiobacillus ferrooxidans as an example, the direct and direct effects are shown in Figure 1. The combined action mechanism refers to the fact that direct and direct actions often coexist during the bacterial leaching process, sometimes dominated by direct action, and sometimes dominated by direct action. The bacteria adsorbed on the surface of the mineral undergo initial oxidation, together providing a growth substrate for the bacteria suspended in the leaching solution.
Although the mechanism research has not reached a universal conclusion, the bacterial leaching process of difficult to leach gold ore has been widely used due to its significant advantages compared to traditional pre-treatment processes. Its main advantages include: (1) low investment and low cost; (2) No need for messy and profound skills; (3) Simple handling of equipment; (4) Beneficial to environmental protection.
The initial research on the biological leaching pretreatment process has achieved outstanding results. Li Ximing and others conducted a kilogram grade experiment on arsenic containing gold concentrate. After 5 days of bacterial pretreatment, the arsenic removal rate of the gold concentrate was greater than 80%, and the gold leaching rate was greater than 90%; Xiang Lan et al. selected the process of filtration column leaching to study the bacterial pretreatment of arsenic containing gold concentrate. The leaching rate of 44 days without bacterial pretreatment in the leaching column of mining and petrochemical industry is 27.4%, while the chemical leaching rate after treatment can reach 66.8% to 73.2%. These research results provide a basis for the further industrial application of bacterial pre oxidation, arsenic removal, and gold extraction. Since the first biological pre oxidation chemical plant on the international list was built in Fairvie, South Africa in 1986, the biological gold extraction plant of Shaanxi Zhongkuang Biological Mining Engineering Co., Ltd., which processes 10 tons of gold concentrate per day in China, was officially put into operation in 1998. The successful construction and operation of the biological oxidation project of Yantai Gold Smelter in 2000 marked that China has become one of the few countries in the world with this high-tech skill. Currently, there are mainly the following processes for bacterial pretreatment: BIOX (R) process, BacTech process, Newmont process, and Geobiotics process.
The pre-treatment process of arsenic containing gold concentrate bacterial leaching has its own shortcomings, such as long residence time and oxidation in acidic solutions. Therefore, it is necessary to use anti-corrosion materials. The exothermic heat generated during the oxidation process leads to temperature rise, and the toxic effect of arsenic on the leaching bacteria during the leaching process restricts its further industrial application. The development and optimization of bacterial pretreatment require a deeper understanding of the mechanism of bacterial oxidation leaching of sulfide ores, and based on this, strengthen the kinetic process, and promote the further industrial application of bacterial leaching pretreatment under the guidance of detailed mechanisms
3、 Discussion on the mechanism of bacterial oxidation of arsenic containing gold concentrate
（1） Bacterial oxidation process of arsenopyrite
Arsenic pyrite (arsenopyrite) is one of the most common minerals in arsenic containing refined gold mines, with a molecular formula of FeAsS, a monoclinic system, consisting of cation Fe2+and anion group [AsS] 2- to form arsenopyrite crystals There are many reports on the mechanism of bacterial leaching of toxic sand. In FeAsS, the content of As and S often changes, from FeAs0.9S1.1 to FeAs1.1S0.9. Poisonous sand is a sulfide ore with high oxidation activity Edwards et al. investigated the modification of the polished surface of arsenopyrite in the presence of At. f through electron microscopy, and found that the polished surface of arsenopyrite did not show bacterial shape or large and fine oxidation marks around the adsorbed bacteria through the long-term action of At. f. Instead, it formed deep grooves on the surface, and the oxidation of arsenopyrite along the deep grooves was strengthened. Then, it was found that the At of arsenopyrite F oxidation may be mainly through direct action Yang Hongying et al. studied the shape and chemical composition of polished surfaces of arsenopyrite at different stages and found that bacterial oxidation of arsenopyrite primarily starts from the surface and gradually deepens along the cracks and fissures towards the interior of the crystal. During the oxidation process of arsenopyrite, As exhibits a valence change of [AsS] 2- → As (III) → As (V), and analyzed that the yellow sediments of bacterial oxidation of arsenopyrite are potassium iron oxide KFe3 (SO4) 2 (OH) 6 and arsenide As2O3, When they cover up on the surface of toxic sand, they inhibit further oxidation of bacteria. Jones et al. discussed the different parts of the cracks formed by bacterial leaching process on the surface of arsenopyrite and the changes in the chemical components of the leaching solution. They tested the surface products of arsenopyrite through electron microscopy and found that even if the surface of arsenopyrite covered the oxidized sediment film, which hindered direct contact between bacteria and minerals, only Fe3+and O2 in the solution could reach the unoxidized crystals through dispersion, The oxidation of arsenopyrite can continue until the sediment film completely obstructs the dispersion of Fe3+and O2 into the unresponsive crystals Min et al. compared the leaching characteristics of arsenopyrite and pyrite, and found that the direct mechanism of bacterial leaching of arsenopyrite is based on: (1) the leaching process only requires a small amount of bacteria to adsorb on the surface of arsenopyrite, and the direct action of bacteria requires the participation of adsorbed bacteria; (2) The leaching process exhibits selective priority leaching of arsenic, as the toxic effect of arsenic on bacteria cannot be explained by direct mechanisms; (3) During the leaching process, no bacterial shaped corrosion pits were observed on the surface of the poisoned sand, but rather exhibited overall oxidation, which can only be explained by chemical oxidation behavior.
The above discussion elucidates the important role of direct bacterial oxidation in the bacterial leaching process of arsenopyrite. However, these discussions do not fully elucidate At F only has a direct effect on the oxidation of arsenopyrite Fernandez et al. conducted more detailed tests on the At. f oxidation process of arsenopyrite, the physical and chemical properties of its surface, the dispersion of bacteria in mineral particles and leachate, and the composition of the leachate The oxidation of arsenopyrite can be divided into three stages. The first stage is when bacteria adsorb onto the surface of the mineral at the beginning of the oxidation of arsenopyrite, and the number of adsorbed bacteria rapidly increases, corroding the surface of the mineral and strengthening the direct action of bacteria. The direct action of Fe2+will promote the growth of bacteria in the solution, and the increase in the number of bacteria in the solution will cause more bacteria to adsorb onto the surface of the mineral. This process is primarily the direct action of bacteria:
In the second stage, many active bacteria oxidize Fe2+, As (III) to Fe3+, As (V), and the attacking Fe3+can also oxidize As (III) and arsenopyrite crystals This process is primarily the direct action of bacteria, that is, the primary role of At. f is to regenerate Fe3+:
The increase in Fe3+and As (V) concentrations in the third stage solution leads to an increase in the concentration of sediment iron in the leaching solution. The increase in sediment reduces the concentration of Fe3+in the solution, suppressing the direct oxidation of bacteria:
The bacterial oxidation process can be indicated by the following total response equation:
During this period, the number one, second stage n=2, and third stage n=4 From the above research results, it can be concluded that the At. f oxidation of arsenopyrite has different mechanisms of action that play a dominant role at different stages. In order to clarify the leaching mechanism, it is necessary to further determine the following issues: how does the bacteria oxidize the arsenopyrite during the top stage, and what medium is used to oxidize the arsenopyrite crystals; How does the oxidation of arsenopyrite crystals by Fe 3+ions occur in the second stage; Based on the conclusions of the first two stages, how to prevent sediment from inhibiting oxidation. Further discussion is needed on the detailed mechanisms of each stage.
（2） The kinetic process of bacterial oxidation of arsenic sulfide ore
There have been many discussions on the kinetic model of bacterial leaching of sulfide ores, and these research results are of certain assistance in establishing the kinetic model of bacterial leaching of arsenopyrite The initial discussion focused on the mass transfer factors of bacterial oxidation based on traditional chemical models, attempting to establish a widely applicable leaching kinetics theory by establishing a model with universal implications With the deepening of the discussion, we will have a deeper understanding of the bacterial leaching process Recent studies on bacterial leaching have shown that there are two processes involved in the leaching process of sulfide ores Based on this, it can be assumed that the leaching of sulfide ore is primarily the chemical leaching of Fe3+, and the role of bacteria is primarily the Fe3+ions in the regeneration system. In this way, the leaching effect of Fe3+on sulfide ore and the oxidation of Fe3+by bacteria can be relatively independently studied and strengthened. During the leaching process, the oxidation of Fe3+by bacteria is completed through iron oxidase, which is an enzymatic reaction. Most models describing the oxidation of Fe3+by bacteria are established through the combination of Monod equation and electrochemical theory As shown in Table 1, different researchers only considered the inhibition or promotion of different environmental parameters on the reaction of bacterial oxidation of Fe3+during the leaching process, and then adjusted the mathematical expression of the model. It can be seen that the reaction mechanism obtained by different researchers is different in fineness. This is mainly because the process of bacterial leaching involves the physical and chemical properties of minerals, physiological characteristics of bacterial strains, and the chaos of selected environmental parameters According to different experimental conditions, different researchers have obtained different experimental results, and under the guidance of fundamentally the same mechanism, the interpretation of the experimental results leads to different adjustments to the fundamental mechanism Therefore, it is meaningful to discuss the detailed bacterial leaching process and obtain a specific kinetic model for the leaching process through experiments.
Table 1: Kinetic models of bacterial growth and Fe3+oxidation in different studies
As for the transformation of elemental sulfur in the process of bacterial leaching, there is currently no consistent kinetic theoretical foundation. In the process of mineral oxidation, elemental sulfur products may adhere to the surface of the mineral as sediment, hindering further oxidation of the mineral. The role of bacteria may be to remove the obstruction of sulfide deposits and promote the continuation of bacterial leaching.
The leaching effect of Fe3+on sulfide ore can be studied using electrochemical theory. In 1999, Ruitenberg et al. derived and validated the Fe3+leaching kinetics model of arsenopyrite based on the bacterial leaching process of arsenic containing gold concentrate.
The shares of Fe3+and Fe2+in the bacterial leaching system can be expressed using the Nernst equation:
In the formula, E is the oxidation recovery potential (mV) of the solution, E0 ‘is the standard electromotive force (mV), R is the universal gas constant [kJ/(mol. K)], T is the temperature (K), z is the number of charges participating in the oxidation recovery reaction, and F is the Faraday constant (C/mol).
The leaching rate expression of arsenopyrite obtained from the conservation of iron element in the system is
The relationship between the leaching rate of arsenopyrite and Fe3+and Fe2+in the system can be obtained from the above equation:
Further obtaining the final expression for Fe3+leaching of arsenopyrite
In subsequent validation experiments, Ruitenberg et al. concluded that the model fundamentally matched the experimental results Of course, this model only provides a simple chemical and electrochemical derivation process, and only describes the leaching kinetics at the micro scale. A more accurate model should consider the leaching effect of bacteria adsorbed on the mineral surface on the mineral and the mass transfer effect of Fe3+and Fe2+.

（3） Biochemistry of bacterial oxidation of arsenic sulfide ore
During the leaching process, bacteria adsorbed on the surface of minerals and suspended in the leaching solution play different roles. It is generally believed that adsorbed bacteria play a direct leaching role, while suspended bacteria oxidize Fe2+in the system and regenerate Fe3+. This is based on different biochemical functions. Bacteria adsorbed on the surface of minerals in the leaching system play an important role in the leaching process Nemati et al. proposed the general process of bacterial adsorption on mineral surfaces: firstly, bacteria adsorb on mineral surfaces, and there is a balance mechanism between free bacteria and adsorbed bacteria; Secondly, extracellular polymers (EPS) excreted by bacteria form the connection between the cell membrane and minerals. Bacteria adsorbed on the surface of minerals are enveloped by their own EPS, which mediates energy communication between bacteria and sulfide minerals, playing an important role in the formation of biofilms and the interface between bacteria and substrates Hansford et al. believed that only bacteria that have excreted extracellular polymers can adsorb on the surface of minerals and corrode them. Different substrates may cause bacteria to excrete different extracellular polymers, such as the extracellular polymer excreted by At.f growing on the surface of pyrite. Glucuronic acid residues were found in the extracellular polymer, which can form complexes with Fe3+. The leaching of minerals only has a significant effect when the Fe3+concentration reaches a certain value, No significant leaching effect was observed when Fe3+concentration was low. The main functions of Fe3+in this process include: (1) forming polymer Fe3+complexes, which may be the starting agents of biological leaching. Additionally, extracellular polymers also have the function of enriching Fe3+; (2) Bacteria have a positive charge on their surface and can adsorb on mineral surfaces with negative charges. Bacteria that excel at sulfur elemental surfaces excrete different extracellular polymers, and their binding to their surface mainly relies on hydrophobic forces, which are relatively weak Tributsch et al. believed that substances containing thiol bonds (- SH) based acids (such as cysteine) in extracellular polymers were the key to the interaction between bacteria and minerals with special crystal structures. These compounds can leach sulfur in a colloidal manner. The above discussion did not touch on the bacterial oxidation process directly involving biological enzymes in extracellular polymers. The bacteria adsorbed on the surface of minerals also play a crucial role in the oxidation of minerals by the complex of Fe 3+and glucuronic acid residues in extracellular polymers; The direct mechanism of action is currently a widely accepted bacterial oxidation mechanism. This study believes that due to the physical and chemical properties of mineral resources and the chaotic nature of At. f itself, bacterial leaching does not have a universal mechanism of action. Whether it is a direct action or a direct action should depend on the detailed mineral and the entire process of bacterial leaching.
Most researchers use chemical immersion theory to explain the coupling effect of ATP in the process of iron oxidation in organisms. They believe that Fe2+enters the respiratory chain of bacteria at suitable sites, and the released electrons are transmitted along the respiratory chain to the final electron acceptor O2 in the bacterial body. The energy generated by this process is used for bacterial growth. As shown in Figure 2, Xe represents the enzyme series involved in electron transfer from Fe2+to O2 in the cell plasma membrane, while Xep and Xen indicate their oxidation and recovery states separately; Xc indicates the enzyme series participating in CO2 biofixation, and Xc represents its inactivation status; Xn is a substance used to store carbon and energy in cells, and Xn ‘is its state of energy storage. Electrons are transferred from Fe2+to O2 through a series of enzymes, forming a proton and electron gradient on the surface of the plasma membrane. Protons are transferred from outside the plasma membrane to inside the plasma membrane through ATP synthase (ATPase), providing energy for the composition of ATP; ATP provides energy for cell fixation of CO2 and the composition of biological macromolecules.
Figure 2. At. f Oxidation Fe2+Reaction Model
Through thermodynamic calculations, Lu Diankun et al. found that the orientation of Fe2+entering the biological respiratory chain is before cytochrome C and after ubiquinone (coenzyme Q). Clearly participating in the enzyme series for electron transfer from Fe3+to O2 is a concern for bacterial workers. Figure 3 shows a number of electron transfer pathways proposed in the study. Some researchers believe that there is an undiscovered electron transport enzyme between electrons from Fe2+to ferritin, as the electron transfer rate obtained through kinetic calculations is too slow compared to the Fe2+oxidation rate obtained in experiments; Unlike the above electron transfer sequence, Hazra et al. believed that electrons were transferred to ferritin through cytochrome C Further research is needed on the electron transfer enzyme system of mining bacteria.
Figure 3 At. f Oxidized Fe2+Electron Transfer Chain
The biochemical characteristics of bacteria are the results of their genetic factors. It is necessary to remind the correlation and rules between sulfide ore bioleaching and bacterial growth biochemical processes. It is necessary to uncover the bacterial oxidation mechanism at the molecular level, which can then be genetically modified to reveal the foundation of a new generation of high-performance leaching bacteria. From the discussion of biochemical processes within bacteria at the molecular level, it is necessary to remind the mechanism of sulfide ore bacterial oxidation leaching, The fundamental issues of demand processing include: the genetic structure of bacteria, which specific segment of the gene participates in the response, what the response process is, close-up and sequencing of genes, how to affect or modify the function of specific genes, and so on Ayme et al. conducted a detailed study on the structure and characteristics of the operons encoding various components of the respiratory chain in At. f ATCC33020, and speculated that the genes encoding all electron transfer enzymes during the leaching process exist in a certain order within the same operon, and these genes are transcribed together; These genes can be transcribed when grown in iron or sulfur substrates, elucidating the role of the protein encoded by this operon in both ferrous oxidation and sulfur oxidation processes.
In the study of the iron oxidation system of Thiobacillus ferrooxidans, different researchers have come up with different conclusions. The reason may be that on one hand, their interpretations of the obtained materials are different, and on the other hand, it reflects the genetic diversity caused by strong selection pressure in the polar growth environment, resulting in differences in energy metabolism systems between different populations.
（4） Electrochemical oxidation of arsenic sulfide ore by bacteria (interface electron transport)
The biological leaching of sulfide ore should be a combination of chemistry, solid surface chemistry, biochemistry, and electrochemistry, as this process is essentially a reaction to oxidation and recovery. The transfer of electrons between the mineral surface and the interface between the leaching solution and the adsorption bacteria interface is the most fundamental reason for the reaction. Therefore, studying the electrochemistry of the leaching process is extremely important. The electrochemical principle of bacterial leaching mainly investigates the role of the following two elements in bacterial leaching: (1) the modification rules of the primary electrical pair Eox (O2/H2O), Esox (S component/adhesive bacteria), and EEP (Fe2+/Fe3+) in the system; (2) The responsive electron transfer chain. As shown in Figure 4 (a), if the iron in the solution mainly exists in the form of Fe2+, resulting in a relatively low EEP in the system, the point difference between Eox and EEP is the largest, resulting in bacterial oxidation manifested in the oxidation process of Fe2+, where electrons are transported from Fe2+to O2 in the bacterial protoplast; Figures 4 (b) and 4 (c) compare the differences in the presence and absence of O2 in the system, where the iron element primarily exists in the form of Fe2+. At this time, electrons are transported from the sulfide to Fe3+and converted into Fe2+. If O2 is sufficient, Fe2+can be de novo converted into Fe3+with the participation of bacteria, allowing the leaching process to continue. Conversely, the consumption of Fe3+will lead to the dominance of Fe2+in the solution, leading to the cessation of leaching.
Figure 4 Connection between the primary oxidation-recovery pair and electron transfer in the bacterial leaching system
The electrochemical interaction between leaching bacteria and mineral interfaces during the leaching process can be considered from two aspects: on the one hand, modifying the electrochemical elements in the leaching system to enhance the leaching effect of bacteria; On the other hand, by detecting the electrochemical signals of the leaching process, a reasonable explanation of the changes in the detection signals with the process is provided, and the possible mechanism of the bacterial leaching process is obtained. The above discussion can be considered using electrochemical methods based on the following ideas: on the one hand, investigating the connection between electrochemical elements and bacterial activity, and on the other hand, investigating the connection between bacterial activity and mineral leaching. The two are combined to investigate the general rules for the connection between electrochemical elements and mineral leaching.
Modern electrochemical analysis skills can serve as a useful tool for studying the electrochemical behavior of sulfide ore bioleaching interfaces. The preparation of mineral electrodes is a condition for electrochemical skills to study the bacterial leaching process Based on the physical and chemical properties of minerals, they can be processed into minerals – carbon paste electrodes or mineral crystals with good conductivity can be processed into mineral electrodes.
Shi Shaoyuan used various electrochemical methods such as cyclic voltammetry curve, potentiodynamic scanning, potentiostatic polarization, and communication impedance to study the electrochemical properties of iron sphalerite carbon paste electrode [Figure 5 (a)], reminding the electrochemical mechanism and micro electrochemical reaction process of iron sphalerite biological leaching process, investigating the corresponding effects of various elements in the leaching system on its electrochemistry, and further reminding the reaction mechanism of mineral biological leaching, And provide a basis for strengthening measures of biological leaching Yu Jingkai studied the electrochemical behavior of arsenopyrite electrodes during anodic oxidation in alkaline, especially aqueous solutions using methods such as potential scanning, potential step analysis, constant potential Coulomb analysis, and communication impedance Cabral et al. [31] described three more sophisticated electrode manufacturing methods (Figure 5) in discussing the interface mechanism of pyrite bacterial leaching systems, where the improved electrodes enhance conductivity and minimize disturbance factors. The detailed biological leaching process of arsenic containing refined gold ore should consider increasingly complex factors. Taking arsenopyrite as an example, Yang et al. studied the submicro structure of arsenopyrite and concluded that the ultrafine gold particles are mostly encapsulated in the crystal of arsenopyrite in a submicro state, and the distribution of gold particles is uneven. Generally speaking, mineral areas with high arsenic content have high gold content, and there is no gold component present in the core area of mineral crystals In gold containing mineral crystals, a natural “gold/arsenopyrite” electric pair is formed. Compared to the laziness of gold, arsenopyrite has high activity because the primary battery function is very simple and is oxidized, which then damages the arsenopyrite lattice,
Expose the gold particles The areas rich in gold are generally located at the lattice edge, crystal surface, and surface cracks of arsenopyrite, and there is no presence of gold components in the core area of mineral crystals. Therefore, in order to achieve the purpose of useful pre-treatment, it is not necessary to completely oxidize arsenopyrite.
The above recalled the discussion on bacterial leaching of sulfide ores, and in detail, there is no universally accepted oxidation mechanism for arsenopyrite. To clarify the mechanism of bacterial leaching, at least three aspects should be clarified: (1) what is involved in the oxidation of sulfide ore, and who is the top electron acceptor in the oxidation process; (2) What is the reaction pathway of this oxidation process, that is, what is the end product of the reaction, and what intermediate stages have been experienced before reaching the end product; (3) What does bacteria do and how they do it. The proposal of these issues all touches on the electrochemical research between the mineral surface, leaching solution, and bacterial interface. Therefore, it can be concluded that electrochemical research skills can play an important role in the research of biological leaching
4、 Enhanced bacterial oxidation process
In the process of practical production application and mechanism discussion, changes to the parameter settings of the leaching system can reduce production costs and help to explore and verify the mechanism. It is necessary to consider the impact of metal ions generated during different mineral leaching processes on bacterial activity in bacterial leaching. The resistance of Thiobacillus ferrooxidans to metal ions can be distinguished as Zn 119, Cu 55, Mn 40, and Ni 72g/T. Xiang Lan discussed the impact of metal ions that occur during the leaching process of different minerals on bacterial activity, believing that domestication can improve bacterial tolerance to specific metal ions, and then improve bacterial activity during the leaching process. Compared with general sulfide ore leaching processes, the toxicity of arsenic to bacteria during the leaching process of arsenic containing gold concentrate is an important factor limiting the selection of high concentration ore slurry for this type of mineral leaching, The high concentration of arsenic will inhibit the oxidation of Fe2+by At. f, and then inactivate Fe3+ The domestication of F can improve its tolerance to arsenic Various physical and chemical factors in the bacterial leaching system may have an impact on the leaching process, such as the influence of flotation reagents on bacterial growth and differentiation of toxic sand during the treatment of flotation gold ore, the behavior of elemental sulfur in microbial oxidation, and the effects of As3+and As5+on bacterial oxidation. Deng et al. discussed the influence of the following factors on the power of bacterial leaching: (1) the selection of arsenic resistant domesticated bacteria; (2) Selection of magnetized water skills; (3) The increase of surfactants; (4) The introduction of catalytic metal ions. The mechanism of action of these elements may not be clear or further verification is needed. The results indicate that they have all improved the effect of bacterial leaching to varying degrees.
The selection of new skills such as hydrothermal, ultrasonic, electric field, and magnetic field enhancement provides key opportunities for the development of new chemical and chemical engineering skills. In terms of biometallurgy, the emergence of Sonobioleaching indicates a broad space for the development of biometallurgy. Swamy et al. investigated the process of bacterial leaching of nickel and lead ore and the combined leaching effect of ultrasonic technology, described the role of ultrasound in enhancing the leaching effect, and proposed a hypothesis on the mechanism of ultrasound enhancing biological metallurgy. The selection of new skills in the field of bio metallurgy helps promote the industrial application of bio metallurgy and provides more methods for its mechanism research.
5、 Conclusion
Biometallurgy is a useful way to deal with the negative effects of metallurgical occupational environment and reduce its costs, especially by applying bioleaching to the pretreatment of refractory gold mines. Due to the chaotic physicochemical properties of various minerals and the physiological characteristics of different leaching microorganisms, there is no universally applicable mechanism for the biological leaching of minerals. The separation of arsenopyrite and Thiobacillus ferrooxidans is one of the most common gold carriers and leaching microorganisms. The study of the mechanism of Thiobacillus ferrooxidans oxidizing arsenopyrite has important academic significance and practical value. Biological oxidation is essentially a reaction to the oxidation of minerals, and the disorderly composition of minerals naturally forms various primary batteries in the system, in which electron transport plays an important role. Modern electrochemical analysis skills can provide comprehensive and accurate electrochemical signals for the system, providing useful techniques for strengthening the role of mineral leaching and studying the leaching mechanism. It can be foreseen that the use of electrochemical methods can effectively explore the bacterial leaching mechanism of refractory gold mines and propose strengthening measures.