Compositions of stable ionic xanthates in aqueous solutions

Abstract

The present invention relates to compositions of long-term stable ionic xanthates in aqueous solutions that can be used as collector reagents in froth flotation processes. The stable ionic xanthate of the present invention is dissolved in an aqueous solution with its maximum water solubility (28-30%) as an ionic product with high stability and safety, avoiding the instability and flammability of solid products, which enables safe operation by an operator in mining work and is also safe to the environment.

Description

Technical Field

[0001] The present invention relates to aqueous compositions of xanthates such as ethyl xanthate (EXS), isopropyl xanthate (IPXS), isobutyl xanthate (IBXS) and amyl xanthate (PAX) and their salts which are stable in aqueous media and methods for their preparation so as to be directly used in froth flotation processes of sulfide minerals without prior treatment of the flotation reagents.

[0002] The xanthates of the present invention have the property of being ionic xanthates, which have the advantage that they are stable over time despite their liquid state being at a concentration in water at which they have maximum solubility. Background Art

[0003] Xanthates are widely used in the mineral flotation process in the mining industry, and different types of chemicals including the above-mentioned IEXS, IPXS, IBXS, PAX and their derivatives have been used for decades to collect valuable species at the lowest possible cost.

[0004] Xanthates are noble, low-cost and stable solid molecules with polar groups containing divalent sulfur of the RO-CS2 type that interact with the metals and provide hydrophobic properties to the ore. Thus, the functional group that provides the hydrophobic properties is an anionic thiol group.

[0005] Xanthate is a sodium or potassium salt of xanthate that is stable in the solid state and is widely used as a collector due to its low cost and high selectivity. Xanthate available on the market is a yellow powder or crystal.

[0006] They are basically made of three elements: carbon disulfide (CS2), alkali (sodium hydroxide or potassium hydroxide) and alcohol (methanol, ethanol, propanol, etc.). It is worth mentioning that they must be used in a neutral or alkaline medium, because in an acidic medium they will hydrolyze and lose their collection properties.

[0007] Recent evidence suggests that xanthates readily decompose to produce carbon disulfide (CS2) in aqueous solution in the absence of minerals. 。 The production of CS2 is pH dependent, therefore, the decomposition of xanthates produces toxic waste that is dangerous for operators and harmful to the environment as it produces a volatile, colorless and highly flammable liquid, which is a long-standing problem in the mining industry. In addition, due to the partial or complete hydrolysis of xanthates, hydrogen sulfide (H2S) is released, which is also a highly toxic compound.

[0008] At present, the main methods for producing xanthate are:

[0009] Direct synthesis: The industrial production of xanthates is carried out batchwise using a kneading process, where alcohol and carbon disulfide are added to a kneader, followed by the addition of a base in powder form. The production of xanthates using this kneading process is difficult to achieve because different variables must be controlled, such as the requirement for the base to have a fine particle size and the high energy consumption required to crush the base in order to achieve the required particle size. In addition to this high energy consumption, the xanthate synthesis reaction is highly exothermic and requires a high-power refrigerator to strictly control the reaction temperature, otherwise it not only affects the product quality but also leads to dangerous exothermic reactions. In short, it is difficult to achieve mass production using this method because there is also a loss of volatile reagents such as carbon disulfide during the production process. In addition, since temperature is a parameter that is difficult to control during the production process, this will lead to incomplete reactions, coupled with secondary reactions, resulting in low product purity.

[0010] Wet alkali method: The wet alkali method involves adding a small amount of water to wet the caustic soda (sodium hydroxide) when producing sodium alkoxide, thereby preventing the caustic soda from agglomerating and allowing the reaction to complete. The prepared sodium alkoxide is reacted with carbon disulfide to form a xanthate (i.e., an aqueous solution of a xanthate). The liquid xanthate product obtained by this method has the advantages of low production cost, no need to dissolve when used, simple operation, and controllable free alkali content in the product. This method is mainly suitable for small-scale local production. However, the liquid xanthate obtained by this method is unstable and difficult to store, and since it must be used immediately once it is made, its application is greatly limited.

[0011] Crystallization method: caustic soda and alcohol are converted into sodium alcohol in a large amount of organic solvents such as benzene and gasoline, and then reacted with carbon disulfide to crystallize the resulting xanthate in solution, filtered and then dried to obtain the product. The xanthate produced by this method has good quality, but the production cost is high.

[0012] Although the solid xanthates described in the prior art offer wide utility, low cost and metallurgical advantages, they have two features that are problematic for their use in industry and environmental impact:

[0013] 1. Solid xanthates are dangerous and highly flammable products due to the production of CS2, which forces the industry to comply with known standards for the handling of dangerous products. Therefore, given its high flammability, it requires storage and distribution logistics that must meet the following requirements: closure and construction of storage bunkers, qualified personnel and certified (explosion-proof) facilities for daily handling, etc., which means that a large investment is required to minimize the risks and continuous monitoring in this regard.

[0014] 2. Xanthate is used in the flotation process at a concentration of about 10% in aqueous solution. The quantity or volume produced in batches is generally consumed within one day, i.e., about 22 to 26 hours of operation, because xanthate decomposes into CS2, alcohol and carbonate and sulfurcarbonate when diluted in water, and loses metallurgical and collection properties within 24 to 26 hours after solution production.

[0015] CN107698475 discloses the synthesis of sulfide ore collectors, and in particular relates to a method for synthesizing liquid xanthate without organic solvents, with the purpose of facilitating the recovery of xanthate at the end of the synthesis process and avoiding the problem of difficulty in recovering organic solvents. The method comprises the following steps: in a three-necked flask equipped with a thermometer, a stirrer, a dropping funnel, a condenser and a water bath, liquid sodium butyl xanthate / potassium butyl xanthate is synthesized without organic solvents. The method comprises: adding butanol and carbon disulfide solution, fully stirring the mixed solution and heating it to 28-35°C; while stirring, slowly dripping sodium hydroxide solution into the mixed solution in the three-necked flask, controlling the dripping rate to 1-3ml / minute; after the sodium hydroxide solution is dripped, stirring and keeping warm to obtain liquid sodium butyl xanthate / potassium butyl xanthate. The preparation method of liquid xanthate is carried out under normal pressure, controlled reaction temperature and dripping rate of sodium hydroxide solution.

[0016] The liquid sodium butyl xanthate / potassium butyl xanthate obtained in the document is a product that must be used in a short time and cannot be stored because it is not stable for a long time. Therefore, the document does not aim to solve the technical problem of stability and long-term stability of xanthate in aqueous media. Therefore, the product disclosed in document CN107698475 is not a product that can be stored and needs to be prepared when used.

[0017] Document CN107235879 also mentions the synthesis of flotation reagents, and in particular relates to a method for synthesizing liquid xanthate. The synthesis method of the compound is: ethanol, C n H 2n +OH and carbon disulfide are mixed in a certain molar ratio, and then a certain proportion of strong alkali solution is added to the solution mixture. The synthesis method provided in the document adopts a reverse feeding method, firstly, alcohol and carbon disulfide are mixed, and then alkali solution is added to the mixed solution to obtain liquid xanthate. Although the document emphasizes that the synthesis of the liquid xanthate has the advantages of simple production process, low equipment investment, safe working environment, low labor intensity, and no need for drying of the product, it does not establish the technical problem of obtaining a long-term stable liquid xanthate in an aqueous medium. The xanthate obtained in the document should be used in a short time.

[0018] JPS567757 describes the preparation of liquid xanthate in an organic solvent such as benzene, toluene, xylene, etc., crystallization in the solvent and extraction with water. The target liquid xanthate is separated directly from the solvent. The organic solvent can be recovered. Compared with the conventional method comprising separating the crystalline xanthate and drying the crystals, the preparation steps can be reduced. The main goal of this document is to recover the organic solvent with the least impurities by liquid-liquid separation of the xanthate solution. Therefore, the technical problem solved by this document is aimed at recovering the solvent rather than obtaining a long-term stable xanthate in an aqueous medium, because the obtained liquid xanthate must be used in a short time.

[0019] Unlike the methods described in the prior art, the method of the present invention solves and develops the technology of diluting the xanthate to its maximum solubility in water (28-30%), thereby obtaining an ionic product with high stability and safety, solving the two most important variables for its use in the mining industry, namely eliminating flammability and improving stability in aqueous solution, since xanthate in solid form (powder or granules) is flammable and very unstable when dissolved in aqueous media, generating volatile compounds that lose their properties and effectiveness over time. Therefore, the technology developed by the present invention provides a safe product with a proven stability of at least 10 months in aqueous solution, thus maintaining its metallurgical properties.

[0020] Thus, the aqueous ionic xanthate technology of the present invention addresses and eliminates flammability, provides high stability over time for safe and reliable processing, while maintaining efficiency and metallurgical performance.

[0021] Currently known industrial evidence indicates that an aqueous liquid ethyl xanthate is manufactured by Coogee, Australia, which is stable for 15 to 30 days when refrigerated and stored at 3-5°C to maintain adequate performance for use in the flotation process of the local mining industry. Unlike this commercial product, the ionic xanthate in aqueous solution of the present invention does not require refrigerated storage and has been shown to have a shelf life of up to 10 months.

[0022] The main difference that makes the technology of the present invention significantly advantageous over the technologies described and / or disclosed or reported in the prior art is that it has zero flammability and high stability over time, which makes the product attractively priced and can be transported or exported worldwide through warehousing logistics without having to consider the handling of flammable products or building shelters in different environmental conditions without losing its effectiveness. One of its advantages that should also be considered is that the production and storage methods have low production and operating costs, which makes the technology highly competitive and excellent metallurgical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1. FT-IR spectra of a) sodium isopropyl xanthate as a commercial reagent and b) stable ionic isopropyl xanthate in aqueous medium.

[0024] Figure 2. Reverse phase HPLC chromatograms of a) commercial sodium isopropyl xanthate; b) stable ionic isopropyl xanthate of the present invention in aqueous medium. Chromatograms c) and d) correspond to enlarged chromatograms a) and b), respectively.

[0025] Experimental conditions: mobile phase (70% 0.1% formic acid solution and 70% acetonitrile, stationary phase (C-18, 25 cm), UV-VIS detector (301 nm)).

[0026] Figure 3. FT-IR spectra and detailed chromatograms of the stable ionic isopropyl xanthate in aqueous medium according to the present invention, a) and c) immediately after preparation, time 0; b) and d) 10 months after preparation.

[0027] Figure 4. FT-IR spectra of a) sodium isobutyl xanthate as a commercial reagent and b) stable ionic isobutyl xanthate in aqueous media.

[0028] Figure 5. Reverse phase HPLC chromatograms of a) commercial sodium isobutyl xanthate; b) stable ionic isobutyl xanthate of the present invention in aqueous medium. Chromatograms c) and d) correspond to enlarged chromatograms a) and b), respectively.

[0029] Experimental conditions: mobile phase (70% 0.1% formic acid solution and 70% acetonitrile, stationary phase (C-18, 25 cm), UV-VIS detector (301 nm)).

[0030] Figure 6. FT-IR spectra and detailed chromatograms of stable ionic isobutyl xanthate in aqueous medium according to the present invention, a) and c) immediately after preparation, time 0; b) and d) 10 months after preparation.

[0031] Figure 7. FT-IR spectra of a) potassium amyl xanthate as a commercial reagent and b) stable ionic amyl xanthate in aqueous medium.

[0032] Figure 8. Reverse phase HPLC chromatograms of a) potassium amyl xanthate and (b) stable ionic amyl xanthate salts of the invention in aqueous medium. Chromatograms c) and d) correspond to enlarged chromatograms a) and b), respectively.

[0033] Experimental conditions: mobile phase (70% 0.1% formic acid solution and 70% acetonitrile, stationary phase (C-18, 25 cm), UV-VIS detector (301 nm)).

[0034] Figure 9. FT-IR spectra and detailed chromatograms of stable ionic amyl xanthate in aqueous medium according to the present invention, a) and c) immediately after preparation, time 0; b) and d) 10 months after preparation.

[0035] Figure 10. Changes in the metallurgical behavior of the stabilized ionic liquid isopropyl xanthate (X30) in different ores over time compared to the standard isopropyl xanthate collector (IPXS). a) Percent copper recovery; b) Percent iron recovery; c) Percent molybdenum recovery. DETAILED DESCRIPTION

[0036] The present invention aims to provide stable xanthate in aqueous solution and its preparation method as a collector in the flotation stage of the mining industry, which has the advantages of long-term stability and can be safely stored, transported, distributed and easily and quickly handled at an industrial level to obtain effective results.

[0037] The inventors of the present invention have developed a method to keep compounds derived from xanthates soluble and stable by forming a stable ionic xanthate product in aqueous solution, overcoming the problems usually associated with xanthates. The chemical stability of xanthates has been reported in the industry to be 12 hours after dissolution. After this time, its efficiency as a trapping agent decreases. On the other hand, the ionic xanthates obtained and developed by the present invention in aqueous solution completely avoid the risk of exothermic reactions in the solid state, which may lead to combustion or explosion.

[0038] In this way, the product of the invention allows long-term storage, which simplifies its transportation, and its direct use in the mining industry, without requiring a dissolution treatment before use, avoiding toxicity problems arising from the release of toxic gases such as CS2 and H2S, and also avoiding the violent exothermic reactions that characterize the high flammability of these products.

[0039] The collectors developed in the present invention allow the storage and transportation of compounds derived from xanthates in a "ready to use" state, which is beneficial and reduces the operating costs of flotation processes in the mining industry, since these collectors are stable over long periods of time, which increases the durability of the product and does not pose the risk of solid xanthates, since they do not release volatile toxic compounds and there is no risk of combustion.

[0040] The preparation of the xanthate obtained by the method of the present invention is mainly carried out through the following stages:

[0041] Stage 1: In a suitable reactor, depending on the batch size to be produced, 65-72%, preferably 68-69%, relative to the total weight, of water with a neutral pH value (pH 6.5-7.0) is charged and the temperature is adjusted to 5-30°C, preferably 15-25°C.

[0042] Stage 2: Keep the stirring speed at 15-100 rpm, preferably 30-70 rpm, and add the xanthate in a concentration of 25-31%, preferably 28-30%, relative to the total weight in the stirred water. The xanthate is added in solid form, which can be granules or powder. The xanthate is selected from ethyl xanthate (EXS), isopropyl xanthate (IPXS), isobutyl xanthate (IBXS) and / or amyl xanthate (PAX).

[0043] Stage 3: Stir for 5-30 minutes, preferably 5-10 minutes, until the solid is completely dissolved.

[0044] Stage 4: After the solid is completely dissolved, add 0.5-5.0 wt % or preferably 1-3 wt % of a nitrogen-containing base relative to the total weight, wherein the nitrogen-containing base is selected from monoethanolamine, diethanolamine, triethanolamine or a mixture thereof, until the pH value reaches 10-12, and stir for 3-20 minutes, preferably 3-7 minutes.

[0045] Stage 5: 1-5 wt %, preferably 2.3-3 wt %, relative to the total weight, of a low molecular weight alcohol selected from methanol, ethanol, propanol, isopropanol, butanol, isobutanol, sec-butanol, n-pentanol, 2-pentanol, 3-pentanol, hexanol, amyl alcohol, preferably isopropanol and isobutanol, is added with continuous stirring. The reaction mixture is stirred for 3-30 minutes, preferably 3-7 minutes.

[0046] The product obtained by the process of the present invention produces an ionic xanthate salt that is stable in aqueous media.

[0047] Example of the preparation of aqueous compositions of ionic xanthates and their stability over time.

[0048] 1. Preparation of Stable Sodium Isopropyl Xanthate Compositions in Aqueous Solution

[0049] In a glass or carbon steel reactor filled with 70 liters of pH neutral (pH 6.5-7.0) water at 25°C, add 28 kg of sodium isopropyl xanthate in granular or powder form. Stir for 30 minutes until the solid is completely dissolved. Subsequently, add 1 kg of ethanolamine / triethanolamine mixture (1:1) and 2.5 kg of isopropanol until the pH reaches 10-12 and stir for 20 minutes.

[0050] The reaction product obtained is a stable ionic isopropyl xanthate, such as Figure 1b , 2b and as shown in 2d.

[0051] Figure 1a) shows the FT-IR spectrum of the commercially available product sodium isopropyl xanthate, showing the -1 、1091cm -1 and 1188cm -1 Symmetrical and asymmetric C=S and COC bond tension bands. Figure 1b ) corresponds to the FT-IR spectrum of the reaction product of the present invention, which shows 6 and -6 cm -1 The inconspicuous band shifts attributed to C=S and COC bond strains indicate that the RO-CS2 functional group has not been altered and therefore it is still free to interact with metals or metal ions.

[0052] Figures 2-a and 2-c show reversed-phase HPLC chromatographic analyses of aqueous solutions of commercially available sodium isopropyl xanthate standards, while Figures 2-b and 2-d show reversed-phase HPLC chromatographic analyses of aqueous solutions of ionic isopropyl xanthate reaction products of the present invention.

[0053] As can be seen from the chromatogram, the polarity change of the sodium isopropyl xanthate component (FIG. 2-a) relative to the stable ionic isopropyl xanthate component of the present invention (FIG. 2-b) is very prominent. The signal corresponding to isopropyl xanthate (retention time = 6.5 minutes) significantly reduces its concentration in the product of the present invention (FIG. 2-d), and the signal assigned to the ionic compound appears at a retention time of less than 5 minutes. In addition to this main compound, non-polar compounds appear in a lower proportion, which can be classified as by-products, corresponding to impurities of the initial product and do not interfere with the metallurgical process (FIG. 2-d).

[0054] In summary, there is experimental evidence to support that the isopropyl xanthate reaction product of the present invention, which is stable in aqueous media, is a stable ionic product that is different from commercially available products and keeps the RO-CS2 group free to interact with metals or metal ions, thereby achieving efficient flotation.

[0055] Stability of isopropyl xanthate compositions in aqueous solutions

[0056] FIG3 shows the FT-IR spectra and chromatogram details of the isopropyl xanthate ionic product of the present invention in aqueous solution at time 0 just prepared and 10 months after preparation. The experimental evidence is consistent with the stability of the isopropyl xanthate ionic product. The chromatograms of the freshly prepared and 10-month-old preparations did not show significant differences. The appearance of the only new minor by-product was observed between signals 4 and 5 in FIG3-d. In the FT-IR spectrum, no significant shift of the band corresponding to the RO-CS2 group was observed. However, a -OH stress band (3380 cm-1) was observed. -1), which is consistent with the partial hydrolysis of the ionic product derived from isopropyl xanthate.

[0057] 2. Preparation of Stable Sodium Isobutyl Xanthate Compositions in Aqueous Solutions

[0058] In a glass or carbon steel reactor filled with 70 liters of pH-neutral (pH 6.5-7.0) water at a temperature of 25°C, 28 g of sodium isobutyl xanthate in granular form are added. Stir for 30 minutes until the solid is completely dissolved. Subsequently, 1 kg of a monoethanolamine / triethanolamine (2:1) mixture and 2.5 kg of isobutanol are added until a pH of 10-12 is reached and stirred for 20 minutes.

[0059] The reaction product obtained is a stable aqueous solution of ionic isobutyl xanthate, such as Figure 4b , 5b and as shown in 5d.

[0060] FIG4-a shows the FT-IR spectrum of a commercially available sodium isobutyl xanthate product, showing that the -1 、1114cm -1 and 1189cm -1 Figure 4-b shows the FT-IR spectrum of the ionic isobutyl xanthate product of the present invention, in which no obvious band shifts attributed to C=S and COC bond strains were observed, which proves that the RO-CS2 group in the compound of the present invention has not changed, as observed for the isopropyl xanthate described previously, and therefore it is still free to interact with metals or metal ions.

[0061] Figures 5-a and 5-c show reversed-phase HPLC analysis of a commercial sodium isobutyl xanthate standard in aqueous solution, and Figures 5-b and 5-d show reversed-phase HPLC analysis of an aqueous solution of the reaction product of the present invention, ionic isobutyl xanthate.

[0062] From the chromatographic analysis ( FIG. 5 ), it can be seen that a significant change in polarity of sodium isobutyl xanthate ( FIG. 5 -a ) is shown relative to the ionic isobutyl xanthate of the present invention ( FIG. 5 -b ), similar to the change observed for isopropyl xanthate in FIG. 2 . The retention times of most components have changed, tending to be shorter than 5 minutes, indicating the formation of an ionic compound, which retains a free RO-CS2 group according to the information provided by the infrared spectrum in FIG. 4 .

[0063] In the enlarged chromatogram of the ionic isobutyl xanthate of the present invention ( FIG. 5 - d ), original signals of unreacted isobutyl xanthate (retention time = 18 and 20.5 minutes) and other minor byproducts of different polarities were observed.

[0064] Stability of ionic isobutyl xanthate compositions in aqueous solutions

[0065] Figure 6 shows the FT-IR spectra and chromatogram details of the stable aqueous ionic isobutyl xanthate composition of the present invention at time 0 and 10 months after preparation. The experimental evidence is consistent with the stability of the ionic isopropyl xanthate derivative product.

[0066] No band shift corresponding to the RO-CS2 group was observed in the FT-IR spectrum, nor was the relative change in the band intensity observed.

[0067] The chromatograms of the aqueous solution of the ionic isobutyl xanthate of the invention after time 0 and 10 months show no difference in the signals corresponding to ionic compounds. However, changes in minor non-polar compounds were observed ( FIG. 6 -d ). It should be emphasized that there is a decrease in the isobutyl xanthate signal (signal 5, FIG. 6 -c and 6 -d ), an increase in non-polar byproducts (signal 7) and the appearance of new non-polar products (signal 8).

[0068] These results are consistent with the stability of the major ionic compound and the transformation of the minor compound.

[0069] 3. Preparation of Stable Amyl Xanthate Compositions in Aqueous Solutions

[0070] In a glass or carbon steel reactor filled with 70 liters of pH neutral (pH 6.5-7.0) water at a temperature of 25°C, 28 g of potassium amyl xanthate in granular form are added. Stir for 30 minutes until the solid is completely dissolved. Subsequently, 1 kg of a monoethanolamine / triethanolamine (2:1) mixture and 2.5 kg of amyl alcohol are added until a pH of 10-12 is reached and stirred for 20 minutes.

[0071] The reaction product produces a stable aqueous solution of ionic amyl xanthate, such as Figure 7b , 8b and 8d.

[0072] FIG. 7 shows the FT-IR spectra of the commercially available potassium amyl xanthate product (a) and the reaction product of the aqueous solution of the stable ionic amyl xanthate of the present invention (b), at 1010 cm -1 , 1100cm-1 and 1150cm-1 -1Symmetrical and asymmetric C=S, COC bond tension bands were exhibited at the positions. No significant differences were observed between the commercial potassium amyl xanthate product and the stable ionic amyl xanthate reaction product of the present invention in terms of the relative positions and intensities of the bands. Thus, in the same manner as mentioned for the previously analyzed compounds, no changes in the RO-CS2 functional group were found, indicating that the RO-CS2 group in the compounds of the present invention has not been altered, as was observed previously for isopropyl and isobutyl xanthates, and therefore the bond remains free to interact with the metal or metal ion.

[0073] The chromatogram shown in Figure 8 shows a dramatic change in polarity of the aqueous composition of the ionic xanthate, similar to that observed for the ionic xanthate in aqueous solution previously analyzed.

[0074] According to the information provided by the IR spectrum in Figure 7, the shift in retention time of most components is toward retention time shorter than 5 minutes, indicating the formation of ionic compounds retaining free RO-CS2 groups. In the enlarged chromatogram of the preparation (Figure 7-d), the original unreacted amyl xanthate signal is observed (retention time = 21.0 and 30 minutes). Among the minor compounds and different from the previous samples, Figure 7-d shows the presence of at least 4 compounds that are more polar than the commercial amyl xanthate, but are not ionic.

[0075] Stability of amyl ionic xanthate compositions in aqueous solutions

[0076] Figure 9 shows the FT-IR spectra and chromatogram details of the stable aqueous amyl xanthate composition of the present invention immediately before preparation (time 0) and 10 months after preparation. The experimental evidence is consistent with the stability of the ionic amyl xanthate derivative product.

[0077] No band shift corresponding to the RO-CS2 group was observed in the FT-IR spectrum, nor was the relative change in the band intensity observed.

[0078] The chromatograms of the ionic amyl xanthate of the present invention after time 0 and 10 months showed no distinction in the signals corresponding to the ionic compounds and in the minor components ( FIGS. 9 - c and 9 - d ).

[0079] Method for recovering metals using the aqueous xanthate composition of the present invention:

[0080] In order to evaluate the metallurgical performance, a flotation process was performed using the ionic xanthate composition of the present invention that is stable in aqueous solution as a collector. The composition of the present invention was tested, and the flotation process performed using the stable ionic isobutyl xanthate composition in aqueous solution obtained by the method described in the present invention is shown below.

[0081] These tests were designed on a large scale in a simulated environment using a validated evaluation system using a laboratory metallurgical flotation cell with a rougher flotation unit. The recoveries of a variety of metals were tested by trying different ores.

[0082] Figure 10 is constructed based on Table No. 1 below and shows the metallurgical behavior of an aqueous stable ionic isopropyl xanthate composition of the invention used as a collector at time 0 immediately after preparation and over time at 1, 4, 5, 6, 7, 8 and 10 months compared to a standard solid isopropyl xanthate ready for use. In order to determine the efficiency of an aqueous solution of a stable ionic isopropyl xanthate composition of the invention, the recoveries of copper, iron and molybdenum were determined and compared to a standard process using a solid xanthate dissolved in an aqueous medium at the time of use.

[0083] Table N° 1 : Comparison of metallurgical results of aqueous compositions of stable ionic isopropyl xanthate of the invention with standard isopropyl xanthate solutions.

[0084]

[0085] In this study, 7 separate flotation runs were considered, with ores 1, 2, 3, 4 and 5 containing different copper, iron and molybdenum grades tested as shown in Table N° 1.

[0086] The purpose of this study was to demonstrate that the xanthate compositions of the present invention in aqueous solution are as effective as standard xanthate salts when used as collectors in flotation processes.

[0087] Independent flotation and mineral extraction procedures were performed on each ore in order to demonstrate the behavior of aqueous solutions of the ionic xanthate salts of the invention when stored for up to 10 months and used at different times, compared to using standard xanthate salts as prepared.

[0088] There were no significant differences in the recovery of copper, iron and molybdenum, thus demonstrating that the composition of ionic xanthate in aqueous solution was as effective as the standard solid xanthate used at the mine site after storage for up to 10 months. Furthermore, the recovery efficiency was observed to be independent of the ore being processed.

[0089] Thus, the advantages offered by the aqueous compositions of the stable ionic xanthates of the present invention enable their direct use in froth flotation processes without the need for pre-treatment of the flotation reagents, unlike standard xanthates which need to be dissolved before use. On the other hand, the xanthates of the present invention in aqueous solution do not decompose to produce carbon disulfide (CS2) or other toxic residues harmful to operators and to the environment, they do not hydrolyze and therefore do not release hydrogen sulfide (H2S), and they can be stored without the risk of combustion or explosion, facilitating their use in the mining industry, and moreover, making it possible to achieve metal recoveries comparable to those of xanthate collector products commonly used in mining and known in the prior art.

Claims

1. An aqueous composition for use as a collector reagent in a froth flotation process, wherein the composition is a stable aqueous solution comprising an ionic xanthate, a nitrogenous base and a low molecular weight C2-C6 alcohol.

2. The aqueous composition according to claim 1, wherein the xanthate is selected from sodium isopropyl xanthate, sodium isobutyl xanthate, and potassium amyl xanthate.

3. The aqueous composition of claim 1, wherein the nitrogenous base is selected from the group consisting of monoethanolamine, diethanolamine and triethanolamine, and mixtures thereof.

4. The aqueous composition according to claim 1, wherein the alcohol is selected from the group consisting of methanol, ethanol, propanol, isopropanol, butanol, isobutanol, sec-butanol, n-pentanol, 2-pentanol, 3-pentanol, hexanol, and pentanol.

5. The aqueous composition according to claim 4, wherein the alcohol is selected from isopropanol, isobutanol, and amyl alcohol.

6. A method for preparing an aqueous composition for use as a collector reagent in a froth flotation process, comprising the following stages: a) charging a reactor with 65-72% water relative to the total weight, the water having a neutral pH and a temperature of 5-30° C., preferably 15-25° C.; b) maintaining constant stirring at 15-100 rpm, preferably 30-70 rpm, and adding solid xanthate in granular or powder form to water at a concentration of 25-31%, preferably 28-30%, relative to the total weight, under stirring; c) maintaining constant stirring for 5-30 minutes, preferably 5-10 minutes, until the solid is completely dissolved; d) adding a nitrogen-containing base in a concentration of 0.5 to 5.0% by weight or preferably 1 to 3% by weight relative to the total weight until a pH of 10-12 is reached and stirring for 3-20 minutes, preferably 3-7 minutes; e) Add 1 to 5% by weight, preferably 2.3 to 3% by weight, relative to the total weight, of a low molecular weight alcohol under constant stirring.

7. The method according to claim 6, wherein the xanthate is selected from sodium isopropyl xanthate, sodium isobutyl xanthate and potassium amyl xanthate.

8. The method of claim 6, wherein the nitrogenous base is selected from monoethanolamine, diethanolamine and triethanolamine, or a mixture thereof.

9. The method of claim 6, wherein the alcohol is selected from the group consisting of methanol, ethanol, propanol, isopropanol, butanol, isobutanol, sec-butanol, n-pentanol, 2-pentanol, 3-pentanol, hexanol and pentanol.

10. The method according to claim 9, wherein the alcohol is preferably selected from isopropanol, isobutanol and pentanol.

11. A process for the recovery of metals by froth flotation, wherein an aqueous composition of a stable ionic xanthate according to claim 1 is used as a collector.

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