Method for mineral separation by adopting biological reagent extracted from gram-positive bacteria

Abstract

The present application relates to a method for mineral separation using biological reagents extracted from gram-positive bacteria. Specifically, the invention relates to a mineral beneficiation method adopting gram-positive bacteria rhodococcus turbid and rhodococcus erythropolis extracts as biological reaction reagents. In this regard, the floatability of minerals is embodied by using gram-positive bacteria as a biological reaction reagent, so that the future prospects of the gram-positive bacteria as substitutes for synthetic reaction reagents and substitutes for separately using microorganisms (biomass) are shown.

Description

[0001] This application is a divisional application of an application with an application date of May 16, 2018, application number 201880032574.3, and invention name “Method for mineral beneficiation using biological reagents extracted from Gram-positive bacteria”. Technical Field

[0002] The invention is mainly used in the mining industry, and comprises a method for mineral beneficiation using a biological reaction reagent extracted from Gram-positive bacteria (Rhodococcus turbidus and Rhodococcus erythropolis). Background Art

[0003] One of the main mineral beneficiation processes used in the mining industry is flotation. Bioflocculation is defined as a separation process in which reagents of biological origin, i.e. bioreactive reagents, are used to selectively float or depress specified mineral types.

[0004] In recent years, bioflocculation has been widely studied as an attractive alternative to traditional reagents with green reagents. Bioreactors are characterized by low toxicity, easy degradation after disposal, and low cost, renewable and readily available raw materials. In addition, bioreactors can be used to treat low-grade ores and tailings, thus enabling their application in low commercial grade deposits.

[0005] On the other hand, although there is evidence that bioflocculation is a reaction process with good recovery and selectivity, there are also several factors that hinder the development of this technology, including little technical progress and poor understanding of the reaction mechanism, reaction kinetics and reaction thermodynamics of the process.

[0006] Bioreagents are heterogeneous mixtures of various compounds that are difficult to characterize, making it difficult to understand the specific reaction mechanisms during flotation, where they can selectively change the characteristics of the target mineral. In addition, it is important to note that theoretical models used to represent mineral / bacteria adhesion behavior have not yet incorporated biological factors. Including these factors is essential to fully understand the bioflocculation reaction process.

[0007] The use of microorganisms and / or their metabolites as reactive agents, in particular trapping agents, frothers and modified mineral processing operations, has become very attractive, as it has great technological potential, is environmentally acceptable and is selective in the processing of mineral particles. These microorganisms and / or their metabolites can modify the characteristics of the mineral directly or indirectly. Direct reaction mechanisms involve direct adhesion of microbial cells to mineral particles, while indirect reaction mechanisms involve product metabolism or soluble cell composition as surface active agents. Both interactions lead to changes in the chemical character, making it hydrophilic or hydrophobic, which is determined by the characteristics of the bacteria and the mineral.

[0008] The main function of microorganisms and / or their metabolites as bioreactive agents in mineral processing is related to the presence of supporting functional groups (hydrocarbon chains) and polar groups (carboxyl, phosphate, hydroxyl) on their cell surface or in the cells. Microorganisms produce internal and / or external compounds that can modify the interfacial properties and thus the amphiphilic molecular characteristics of the mineral surface.

[0009] Bacteria of the genera Rhodococcus erythropolis and Rhodococcus opacus are Gram-positive, non-pathogenic, and widely found in nature from a wide range of sources.

[0010] For example, CN102489415 describes the use of Rhodococcus erythropolis as a capture agent in the flotation process of a hematite-containing system. This document differs from the present invention in that it uses the bacteria themselves (biomass) as the capture agent, rather than a bioreactor extracted from the bacteria.

[0011] CN102911904 describes the use of bacteria as capture agents in the flotation process of ores containing refractory hematite. As in CN 102489415, this document differs from the present invention in that it uses the bacteria themselves (biomass) as its capture agent, rather than a bioreagent extracted from the bacteria.

[0012] The article "Production of Biosurfactants from Rhodococcus erythropolis and Their Application in Oil Removal" published by the Federal University of Rio de Janeiro on October 29, 2010 mentioned a biosurfactant extracted from Rhodococcus erythropolis for treating oil-contaminated soil. The difference between the present invention and the said document is that it is mineral flotation, not oil-contaminated soil treatment.

[0013] The article "Effect of Rhodococcus erythropolis on Flocculation and Flotation of Pure Minerals in Hematite" published by the University of Science and Technology Beijing on February 27, 2013 describes the use of Rhodococcus erythropolis bacteria as a capture agent in the flotation process of hematite-containing systems. As in CN 102489415 and CN102911904, the difference between this document and the present invention is that it uses bacteria (biomass) as its capture agent, rather than a bioreactor extracted from bacteria.

[0014] The article "Floatation of serpentine and quartz using biosurfactants" published by Wroclaw University of Technology, Poland on May 6, 2012, mentioned a biosurfactant extracted from Bacillus circulans and Streptomyces for flotation of quartz and serpentine. The difference between the present invention and the said document is that they are different bacteria and different minerals to be floated.

[0015] As will be described in further detail below, the present invention provides a method for mineral beneficiation using a bioreagent extracted from the bacteria Rhodococcus opacus and Rhodococcus erythropolis. Summary of the invention

[0016] The main purpose of the present invention is to provide a method for mineral beneficiation using a bioreactor extracted from Rhodococcus turbidus and Rhodococcus erythropolis bacteria.

[0017] Therefore, the extraction of metabolites, especially protein compounds, from Rhodococcus opacus and Rhodococcus erythropolis was evaluated for their use as collecting bioreagents in mineral flotation, as proteins tend to provide hydrophobicity on the mineral surface, thus facilitating the flotation process.

[0018] In this regard, the floatability of minerals was evaluated using a bioreagent extracted from Rhodococcus to determine its potential as an alternative to synthetic reagents and to microorganisms (biomass) alone. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The detailed description given below refers to the accompanying drawings and their respective reference numerals.

[0020] Figure 1 The process flow diagram for extracting bioreaction reagents from microorganisms is illustrated;

[0021] Figure 2 Infrared spectra of Rhodococcus opacus bacteria (blue line) and crude bioreagent (black line) are shown;

[0022] Figure 3 The infrared spectra of Rhodococcus erythropolis (blue line) and crude bioreagent (black line) are shown;

[0023] Figure 4 The effect of bioreagent concentration on the surface tension of deionized water at neutral pH at 20 °C is shown: the solid line represents the bioactivity extracted from Rhodococcus opacus and the solid line represents the bioactivity extracted from Rhodococcus erythropolis;

[0024] Figure 5 Bar graphs showing the comparison of hematite floatability using bacteria (biomass) and bioreactors: (a) pH 3, (b) pH 5, (c) pH 7, (d) pH 9, (e) pH 11;

[0025] Figure 6 is a graph illustrating the floatability of hematite in different concentrations of bioreactor extracted from Rhodococcus opacus;

[0026] Figure 7 is a graph illustrating the floatability of hematite in different concentrations of bioreactor extracted from Rhodococcus erythropolis;

[0027] Figure 8Bar graphs showing the comparison of the floatability of hematite, quartz, dolomite, calcite, and apatite using bioreagents extracted from Rhodococcus opacus at: (a) pH 3, (b) pH 5, (c) pH 7, (d) pH 9, (e) pH 11;

[0028] Fig. 9 Bar graphs showing the comparison of the floatability of hematite, quartz, dolomite, calcite, and apatite using bioreagents extracted from Rhodococcus erythropolis: (a) pH 3, (b) pH 5, (c) pH 7, (d) pH 9, (e) pH 11. DETAILED DESCRIPTION

[0029] First, it is emphasized that the following description will start from a preferred embodiment of the present invention. However, it is obvious to those skilled in the art that the present invention is not limited to this specific embodiment.

[0030] The invention discloses a method for mineral processing using biological reaction reagents extracted from bacteria Rhodococcus turbidus and Rhodococcus erythropolis. The method comprises the following steps: i) ore crushing and pulping; ii) adding and adjusting biological reagents; and iii) flotation.

[0031] As is well known to those skilled in the art, the growth broth used to inoculate the bacteria in the present invention should preferably contain sources of nutrients, proteins and carbohydrates. Broth can be prepared using commercial reagents, or can be partially or completely replaced with ingredients from other production chains (e.g., food industry residues). The growth of microorganisms can be carried out in a rotary kiln, or, for large-scale processes, fermenters or bioreactors can be used. The presence of temperature and pollutants must first be controlled.

[0032] According to the present invention, the extraction of the bioreagent from Rhodococcus bacteria (Rhodococcus turbidus, Rhodococcus erythropolis) is carried out by a solvent extraction process, preferably hot ethanol extraction (100-140° C.).

[0033] Figure 1 The process flow chart of extracting bioreactors from microorganisms is shown, including the steps of (i) solid / liquid separation and water washing; (ii) resuspension with ethanol; (iii) high pressure sterilization; (iv) new solid / liquid separation; (v) drying or freeze-drying the biomass; (vi) resuspension with water (vii) new solid / liquid separation.

[0034] The solid / liquid separation step can preferably be carried out by centrifugation or filtration using a 25 μm pore opening membrane. Autoclaving should preferably be carried out at a pressure of 0.5 to 1.5 bar and a temperature range of 100 to 140°C.

[0035] The ratio of ethanol to water used in the extraction and dissolution of the soluble fraction, respectively, can be adjusted according to the growth process of the microorganisms. Factors that may lead to process changes: broth composition (e.g., it can be replaced by food industry tailings), equipment and growth conditions (e.g., use of bio-fermentation cultures, immobilized cell inoculation).

[0036] According to the present invention, the extraction of the bioreaction reagent from Rhodococcus bacteria (Rhodococcus opacus, Rhodococcus erythropolis) may include a purification step.

[0037] The bioreactive reagent obtained is preferably stored at 4°C for a maximum of 5 days to be used later in the flotation process. The extraction method used allows the recovery of components related to intracellular compounds and compounds present in the cell walls of microorganisms. These substances are responsible for conferring hydrophobicity on the mineral surface.

[0038] The bioreagent extracted from the Gram-positive bacteria belonging to the genus Rhodococcus (Rhodococcus turbidus, Rhodococcus erythropolis) of the present invention can be used for the flotation of any iron mineral, preferably hematite. It is also possible to flotate mineral systems, preferably hematite-quartz systems. However, the method of the present invention can also be used to float ores containing other minerals of interest such as calcite, dolomite and apatite.

[0039] According to the present invention, the reagent added in the flotation step may contain only a bioreactor extracted from Rhodococcus bacteria (Rhodococcus turbidus, Rhodococcus erythropolis) in a concentration range of 5 to 200 mg / L, or may be used in combination with any of the following reagents, which are inhibitors, capture agents and frothers.

[0040] According to the invention, the conditioning step may be performed in a pH range of 3 to 7 for the hematite-quartz system.

[0041] Still according to the invention, the flotation step can be carried out in a Hallimond tube, a flotation cell or a flotation column.

[0042] According to the invention, the flotation step preferably consists of direct flotation of the metal / element of interest.

[0043] Still according to the invention, the flotation step of the hematite-quartz system can be carried out in a pH range of 3 to 7.

[0044] As shown in Examples 4, 5 and 6, the results of the bioreactor flotation tests according to the present invention show the potential use of bioreactors as a substitute for synthetic reagents in mineral flotation processes. For example, in addition to accelerating the flotation process, the use of bioreactors also improves the recovery rate of hematite. Figure 5The composition of the bar graph is shown, comparing the floatability of hematite using Rhodococcus opacus and its bioreactor at different pH values: (a) pH 3, (b) pH 5, (c) pH 7, (d) pH 9, (e) pH 11.

[0045] The maximum floatability of hematite obtained using bacteria (biomass) at neutral pH is 43% ( Figure 5 (c)), while the maximum recovery rate of the bioreactor at acidic pH was 95% ( Figure 5 (a) and (b)). The high performance of the bioreactors even in acidic environments is characteristic of most bioreactors, and they exhibit stability even under extreme conditions of temperature, pH and salinity. The results show that the bioreactors of the present invention have a high affinity for hematite particles and a relatively low reagent consumption compared to those using bacteria (biomass).

[0046] Example 1

[0047] The bioreaction extraction test was carried out from microorganisms. The Rhodococcus bacteria (Rhodococcus opacus, Rhodococcus erythropolis) were purchased from the Brazilian Collection of Environmental and Industrial Microorganisms (UNICAMP).

[0048] The culture medium used for the growth of Rhodococcus turbidus bacteria consists of 10 g dm -3 Glucose, 5g dm -3 Peptone, 3g dm -3 Malt extract, 3g dm -3 Yeast extract, and 2g dm -3 CaCO3. The culture medium for Rhodococcus erythropolis consists of 17 g dm -3 Casein extract, 3g dm -3 Soy flour, 5g dm -3 Sodium chloride, 2.5 g dm -3 Glucose and 2.5gdm -3 The bacteria were cultured in a rotary oven at 125 rpm for 7 days.

[0049] After the growth period, the biomass ( Figure 1 ). The biomass was washed with deionized water and centrifuged again to remove the remaining growth broth. The wash was repeated twice.

[0050] The biomass was resuspended with 500 ml of ethanol per liter of cell suspension used for the initial centrifugation process. For the bioreagent extraction, the solution containing the biomass and ethanol was autoclaved at 1 bar, 121°C for 20 minutes.

[0051] After extraction, a new centrifugation step was performed to separate the biomass from the extract. The supernatant was discarded and the biomass was dried in an oven at 50°C for 24 hours.

[0052] The dried biomass was resuspended in deionized water at a rate of 125 ml of water per liter of growth broth (the cell suspension was used for the extraction process). The mixture was centrifuged and the water-insoluble portion was discarded, while the soluble portion was stored at 4°C for up to 5 days for microbial cultivation and characterization analysis.

[0053] Example 2

[0054] In order to identify the functional groups present in the bioreaction reagent obtained in Example 1, infrared analysis was performed using a Nicolet Fourier Transform Infrared Spectrometer 2000 and a KBr matrix as a reference. The sample was dried at 50°C and homogenized with KBr.

[0055] In order to compare the properties of the bioreactor with those of the microorganisms themselves (biomass), Rhodococcus opacus and Rhodococcus erythropolis were analyzed under the same conditions as above, e.g. Figure 2 and Figure 3 shown.

[0056] In the infrared spectrum of bacteria (biomass), it is observed that 1500cm -1 The region below has a large number of adsorption peaks due to possible variations in carbon-carbon, carbon-oxygen, and carbon-nitrogen bonds; this region is unique to each substance. In addition, aromatic compounds, aldehydes, ketones, and esters are found in the 1750-1620 cm -1 There is a strong peak between them. Mycolic acids are part of the cell coat and are responsible for the hydrophobicity of bacteria, which can be reflected by the peaks of alkane, ketone and aldehyde clusters. The presence of amino and aromatic compounds, probably part of aromatic amino acids, indicates that proteinaceous matter plays a decisive role in the flotation and flocculation processes.

[0057] Regarding the bioreactive agents, Table 1 shows the possible functional groups found in the infrared spectroscopy analysis. -1 The presence of alcohol, alkane, alkene and ketone groups in the region between 1400, 1548 and 3350 cm -1 The identification of aromatic and amino groups can indicate the presence of polar amino acids such as tyrosine.

[0058] According to the literature, proteins present in bacteria and their bioproducts can be responsible for the flocculation-flotation process due to their amphiphilic nature.

[0059] Table 1: Possible functional groups identified in IR spectroscopy analysis of crude bioreagents.

[0060]

[0061] Example 3

[0062] In order to verify another important feature of the bioreaction reagent obtained in Example 1, the effect of the bioreaction reagent on the surface tension of distilled water at neutral pH was evaluated by varying the bioreaction reagent concentration from 0 ppm to 250 ppm. Surface tension measurements were performed by the ring method on a Kruss K10 digital tensiometer. In order to estimate the critical micelle concentration (CMC), two tangent lines were constructed at the points of minimum and maximum surface tension, and the CMC was represented at the intersection of these lines. For the bioreaction reagent from Rhodococcus opacus (RoBR), the CMC was 92 ppm, while for the bioreaction reagent extracted from Rhodococcus erythropolis (ReBR), it was 62 ppm.

[0063] Figure 4 The surface tension is shown as a function of the bioreagent concentration. When RoBR is used, the surface tension is reduced to 50.5 mN m -1 When ReBR is used, the surface tension is reduced to 62 mN m -1 Bioreactors can be composed of polymeric substances that do not necessarily reduce surface tension, but can effectively reduce the interfacial tension between immiscible liquids and form stable emulsions.

[0064] Example 4

[0065] In order to verify the floatability of hematite, according to the present invention, a 10 -3 mol·L -1 Modified Hallimond tube with sodium chloride as different electrolytes and air flow rate of 35dm 3 min -1 , microflocculation tests were performed with a mineral size fraction of +75-150 microns, a conditioning time of 2 minutes, and a flotation time of 1 minute. The concentration of the bioreagent was varied between 25 and 150 ppm, and the pH was varied between 3 and 11. The buoyancy was calculated as the ratio of the floating mass to the total mass of the mineral.

[0066] Figure 6 and Figure 7The floatability of hematite with RoBR and ReBR is shown, respectively. Both bioreagents show similar behavior: the maximum floatability of hematite (about 90%) occurs at pH 3 and a bioreagent concentration of 75 ppm. However, it was found that hematite floats at acidic and neutral pH values ​​with RoBR, while with ReBR, hematite floats only at acidic pH values. Literature indicates that most non-toxic bioreagents are anionic. In addition, the isoelectric point of hematite is about 5.1. In this way, it is possible to link the pH of the culture medium to the adsorption of the bioreagent on the mineral surface. In acidic media, there will be electrostatic attraction between the mineral surface and the anionic bioreagent, resulting in maximum adsorption and thus maximum recovery of hematite. On the other hand, in alkaline media, the adsorption of the bioreagent on the mineral surface will be minimal due to electrostatic repulsion.

[0067] Example 5

[0068] To verify the floatability zones of calcite, dolomite, apatite, quartz and hematite, tests were performed under the same conditions as described in Example 4. The tests were performed with pure minerals.

[0069] Figure 8 and Fig. 9 The bar graph composition comparing the floatability of the different minerals mentioned above using two bioreactors (ReBR and RoBR) is shown. Several selective areas (windows) in the studied minerals can be observed, for example:

[0070] a) Considering that the ore is composed of hematite and quartz minerals, RoBR can be used to directly float hematite at pH 3, 5 and 7 at 50 to 150 ppm, while when ReBR is used, this method is only applicable to pH 3 and pH 5. This is because at pH 3, the concentration of the bioreactor can be lower, 25 ppm.

[0071] b) Considering the mineralogy of apatite and calcite, direct apatite flotation has been demonstrated at pH 5, 7 and 9 with 25 ppm RoBR and 50 ppm RoBR at pH 11. Separation between apatite and calcite has been performed at pH 7 by direct flotation with 100-150 ppm calcite.

[0072] c) Considering the mineralogy consisting of apatite and dolomite, it has been demonstrated that direct flotation of dolomite is possible at pH 3 in the presence of 25 ppm ReBR.

[0073] Example 6

[0074] The hematite-quartz system was studied using the same procedure and flotation conditions as listed in Example 5. The pH was maintained at 3 and three different hematite-quartz ratios (25H-75Q; 50H-50Q; 75H-25Q) ReBR and two concentrations (50 mg / L -1 and 100 mg L -1 ). The results are shown in Table 2.

[0075] Table 2: Results of microbial phase test in hematite-quartz system

[0076]

[0077] The results show that metallurgical recoveries are similar for the two bioreactor concentrations studied when comparing the same mineral system. For the 25% hematite-75% quartz ratio, the difference in metallurgical recoveries was 1% (50 and 100 mg L -1 The recoveries of the bioreactors were 55.5 and 56.5%, respectively. For a 5% hematite-50% quartz ratio, 50 and 100 mg·L -1 When the biological reaction reagent was used, the iron recovery was 83.6% and 85.5%, respectively. For the 75% hematite-25% quartz ratio, 50 and 100 mg·L -1 The metallurgical recoveries of the bioreactor reagents were 89.7% and 91.3%, respectively.

[0078] The same behavior can be seen when comparing the mass recovery and iron content of the (flotation) concentrates. -1 ) had little interference with the results of the above flotation process. This effect can be attributed to the RoBR efficiency in the bioflocculant process.

Claims

1. A mineral beneficiation method, characterized in that: The method uses a biological reaction reagent extracted from Rhodococcus erythropolis cultured with bacteria, and comprises the following steps: A-Ore crushing and slurry preparation; B-addition and adjustment of biological reagents; C-flotation, wherein the minerals include calcite and dolomite, in order to recover a specified metal / element from an ore containing any of the foregoing minerals, The biological reaction reagent extracted from the cell wall of Rhodococcus erythropolis is extracted by a solvent extraction process, preferably by hot ethanol extraction (100-140° C.).

2. The mineral beneficiation method according to claim 1, characterized in that: The mineral comprises a mineral system, preferably a hematite-quartz system.

3. The mineral beneficiation method according to claim 1, characterized in that: The reaction reagent added in step B contains only biological reaction reagent extracted from the cell wall of Rhodococcus erythropolis in a concentration range of 25 to 200 mg / L.

4. The mineral beneficiation method according to claim 1, characterized in that: The reaction reagents in step B include a biological reaction reagent extracted from Rhodococcus erythropolis, an inhibitor, a collection reaction reagent and a foaming agent.

5. The mineral beneficiation method according to claim 1, characterized in that: For the hematite-quartz system, the adjustment of step B is carried out in the pH range of 3 to 7.

6. The mineral beneficiation method according to claim 1, characterized in that: The flotation of step C can be carried out in a Hallimond tube, a flotation cell or a flotation column.

7. The mineral beneficiation method according to claim 1, characterized in that: The flotation in step C is preferably direct flotation of the specified metal / element.

8. The mineral beneficiation method according to claim 1, characterized in that: For the hematite-quartz system, the flotation of step C is carried out in the pH range of 3 to 7.

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