AQUEOUS COMPOSITION WHICH IMPROVES THE EFFICIENCY OF HYDROMETALLURGICAL AND PYROMETALLURGICAL PROCESSES FOR METALS WHEN USED IN SAME, SAID COMPOSITION COMPRISING: AN AQUEOUS BASE, ONE OR MORE SURFACTANTS, ONE OR MORE ADJUVANT GASES IN THE AFOREMENTIONED PROCESSES, ADDED THERETO AS NANO- AND MICRO-SIZED BUBBLES

Abstract

One or more surfactants and one or more adjuvant gases in the hydrometallurgical and pyrometallurgical processes, which are added thereto in the state of nanobubbles and microbubbles, both the gases used and the nanobubbles and the microbubbles thereof, are in a variable proportion depending on the physicochemical requirements of each of the stages of the process where it is applied. The nanobubbles and microbubbles, of the proposed composition, make it possible to significantly increase the physicochemical properties of these gases such as: flotation speed, oxidizing power, reducing power, contact area provided and coalescence speed.

Claims

1. An aqueous composition that increases the efficiency in the hydro-metallurgical and pyrometallurgical processes of metal extraction comprising: water, at least one surface-active agent and one or more gases that are adjuvants of these processes, in the nano and microbubble state.

2. The composition according to claim 1, wherein the water can be drinking water, industrial water, sea water, a leaching solution or a mixture of the above.

3. The composition according to claim 1, wherein the surface-active agent is saponin.

4. The composition according to claim 3, wherein the concentration of the surface-active agent saponin comprises a range of between 0.1 ppm and 30 ppm.

5. The composition according to claim 1, wherein the surface-active agent can be one of the groups: hydrocarbonates, fluorocarbonate or mixtures thereof.

6. The composition according to claim 1, wherein said adjuvant gases are selected from the group consisting of: oxygen, ozone, air, nitrogen dioxide, argon, nitrogen, helium, carbon dioxide and mixtures thereof.

7. The composition according to claim 1, wherein the size of the nanobubbles is 100 nm.

8. The composition according to claim 1, wherein the size of the nanobubbles comprises a range of between 1 nm and 1 .Math.m.

9. The composition according to claim 1, wherein the size of the microbubbles comprises a range of between 1 .Math.m and 100 .Math.m.

10. A process for applying the aqueous composition according to claim 1, wherein the process comprises the following steps: a) connecting a source supplying the gases to be injected with the nano- and/or microbubble generator; b) selecting the proportion of gases to be injected; c) activating the nanobubble and microbubble producing source; d) connecting the nanobubble and microbubble generating source to a conduit that conveys the leaching solution to the leaching pile of a solution tank; e) adding the nanobubble and microbubble composition to the tank containing the water or to the tank containing the leaching solution.

11. The aqueous composition according to claim 1, wherein the composition is applied to the processes of: mineral flotation, leaching of concentrates, flotation of clay minerals, leaching of arsenic minerals, leaching of metal powders, agitated leaching of minerals, electrorefining, agglomeration, leaching in piles and solvent extraction.

12. The composition according to claim 1, wherein the metal is copper, zinc, gold, uranium, silver or nickel.

Description

DESCRIPTION OF THE INVENTION

[0146] The present application discloses an aqueous composition that is applied in strategic processes and of greater impact on the efficiency of hydrometallurgy and pyrometallurgy, detailed in the following list and flow diagram shown on sheet 5/5. [0147] Mineral flotation [0148] Leaching of high arsenic minerals [0149] Leaching of melting metal powders [0150] Electrorefining. [0151] Leaching of Minerals in piles [0152] Solvent extraction [0153] Concentrate leaching

[0154] The composition of the present application comprises: One or more surfactants and one or more adjuvant gases in the hydrometallurgical and pyrometallurgical processes in which it is applied, which are added thereto in the state of nanobubbles and microbubbles. In addition, it understands that both the gases used and the nanobubbles and the microbubbles thereof, are in a variable proportion depending on the physicochemical requirements of each of the stages of the process where it is applied.

[0155] More specifically, the present invention discloses an aqueous composition that increases the efficiency in the hydro metallurgical and pyrometallurgical processes of metal extraction such as: copper, zinc, gold, uranium, silver, nickel comprising: water, at least one surface-active agent and one or more gases that are adjuvants of these processes, in the nano- and microbubble state.

[0156] In the present invention the water may be drinking water, industrial water, sea water, a leaching solution or a mixture thereof.

[0157] In the present invention preferably the surface-active agent is saponin and is used in a range between 0.1 ppm and 30 ppm.

[0158] In another embodiment of the present invention the surface-active agent may be one of the groups: hydrocarbon compounds, fluorocarbonate or mixtures thereof.

[0159] In the present invention the size of the nanobubbles is in the range of 1 nm to 1 .Math.m.

[0160] In the present invention preferably the size of the nanobubbles is 100 nm

[0161] In the present invention the size of the microbubbles is in the range of 1 .Math.m to 100 .Math.m.

[0162] Further, the present invention discloses a process for applying the above disclosed aqueous composition:

[0163] The process comprises the following steps: [0164] a) connecting a source supplying the gases to be injected with the nano- and/or microbubble generator; [0165] b) selecting the proportion of gases to be injected; [0166] c) activating the nanobubble and microbubble producing source; [0167] d) connecting the nanobubble and microbubble generating source to a conduit that conveys the leaching solution to the leaching pile of a solution tank; [0168] e) adding the nanobubble and microbubble composition to the tank containing the water or to the tank containing the leaching solution.

[0169] Furthermore, the present invention discloses the use of the above-disclosed aqueous composition in processes such as: mineral flotation, concentrate leaching, clay mineral flotation, arsenic mineral leaching, metal powder leaching, agitated mineral leaching, electrorefining, agglomerating, pile leaching and solvent extraction.

[0170] The nanobubbles and microbubbles, of the proposed composition, make it possible to significantly increase the physicochemical properties of these gases such as: flotation speed, oxidizing power, reducing power, contact area provided and coalescence speed.

[0171] The gases that can be considered adjuvants of the hydrometallurgy and pyrometallurgy processes are: pure oxygen, ozone, carbon dioxide, nitrogen, nitrous oxide, air, helium, argon or any other gas or mixture thereof, which, due to their physical or chemical properties, favor the kinetics of said processes.

[0172] In the present invention more specifically the adjuvant gases are selected from: oxygen, ozone, air, nitrogen dioxide, argon, nitrogen, helium, carbon dioxide or mixtures thereof.

[0173] In the mineral flotation process, the proposed composition allows, through its application, the recovery of the particles of valuable mineral of fine and ultrafine size, which currently is not recovered by the bubbles of conventional size, thus avoiding the loss of this valuable fraction and also preventing it from being discarded in tailings reservoirs, with the consequent increase in the environmental pollution that this implies.

[0174] By incorporating the composition of nanobubbles and microbubbles, they provide greater contact area or surface for the capture of valuable species and due to their size, they are distributed throughout in volume of the flotation solution that is between the conventional bubbles. In this way they capture on their surface the particles of fine and ultrafine mineral that has not been recovered by conventional bubbles.

[0175] Mineral-laden nanobubbles and microbubbles coalesce with conventional sized bubbles and rise up the water column to the surface where it is collected.

[0176] To favor the flotation of the different types of minerals and cover their different physical properties such as specific weight or presence of steriles and dimensions of the flotation equipment, the composition comprises that the gases used to obtain them are: oxygen, air, argon, helium, a mixture of them or another gas that is adjunctive to the process.

[0177] In flotation of minerals with high content of fine clays, the application of the proposed composition allows the capture of the particles of these elements that present a fine and ultrafine particle size.

[0178] Nanobubbles and microbubbles capture these particles and then coalesce with each other first and then with conventional bubbles.

[0179] In this way the fine clay particles float towards the surface where they are collected. For this process the composition comprises that the adjuvant gases of the flotation are: air, argon, helium or other gas, or mixture thereof.

[0180] For the agitated leaching process of high arsenic sulfur minerals, the composition comprises that the gases of the composition that the gases used for obtaining the nanobubbles and microbubbles is oxygen, ozone, air or mixture thereof. Thus, arsenic is oxidized in an efficient and controlled manner, avoiding the use of oxidizing agents such as hydrogen peroxide.

[0181] In the process of leaching metal concentrates, the application of the composition in the water with which the pulp is formed allows, in the presence of sulfuric acid, to precipitate arsenic and oxidize metal sulfides forming sulfates. The enormous amount of contact area provided by the nanobubbles and microbubbles of the proposed composition, allow the control of the kinetics of the reaction, significantly increasing the efficiency of the process, and decreasing the amount of energy required. For this process, the composition comprises that the adjuvant gases for leaching concentrates are: air, ozone, oxygen, or a mixture thereof.

[0182] In the process of leaching metal powders from melting, the composition comprises that the gases used for obtaining the nanobubbles and microbubbles is oxygen, ozone, air or a mixture thereof. The nanobubbles and microbubbles of this composition efficiently provide the oxygen necessary for the efficient leaching of metallic melting powders, avoiding the use of dangerous and difficult-to-manage reagents such as hydrogen peroxide.

[0183] For the electrorefining process, the composition comprises that the gases used to obtain the nanobubbles and microbubbles are: oxygen, ozone, air or mixture thereof. The composition is applied to the ducts carrying the electrolyte to the electrorefining cells, where the nanobubbles and microbubbles increase the dissolved oxygen available in the contact zone between the anodes and the electrolyte. This eliminates the passivation of the anode by avoiding the formation of cuprous ions, generating an increase in the efficiency of the process.

[0184] In the mineral agglomeration process prior to leaching, the application of the proposed composition, in the water or leaching solution used to form the pulp, allows ensuring the presence of oxygen throughout the interior of the glomer, in its microcracks and interstices. Thus, the chemical reaction of the leaching is favored and the kinetics of the leaching piles are increased, thereby reducing the time of treatment of the mineral in them. For this agglomeration process, the composition comprises that the gases used to obtain the nanobubbles and microbubbles are: air, oxygen, ozone, a mixture thereof, or another gas that is adjuvant to the subsequent process that is leaching.

[0185] For the process of leaching minerals into piles, the composition comprises that the gases used to obtain the nanobubbles and microbubbles are: oxygen, ozone, air or mixture thereof. The proposed composition is added to the leaching solution before it is incorporated into the leaching piles, whereby the same flow of said solution is transformed into the medium of distribution of the adjuvant gases to all sectors of the pile. This is added to the duct or pipe that conveys the leaching solution to the leachate pile or to the pools or tanks where the leaching solution is accumulated before being sent to the pile.

[0186] The application of the proposed composition guarantees a high efficiency and control of the leaching of oxidized minerals, in addition to avoiding the use of forced aeration networks of the piles and the environmental pollution produced by the discarding of these ducts in the dumps.

[0187] In the solvent extraction process or SX, the proposed composition is applied for the removal of aqueous debris and for the removal of organic debris.

[0188] For the removal of organic debris in pools, tanks or wells for intermediate and final solutions, the proposed composition is applied in the flotation columns and/or in the pools. The composition is applied to the ducts that provide the water or directly to the columns or pools. For application in these two processes, the proposed composition comprises that the gases used for obtaining the nanobubbles and microbubbles are: air, nitrogen, argon or helium in pure form or mixture thereof.

[0189] For aqueous debris, the proposed composition allows them to coalesce with water microdroplets or aqueous debris contaminated with chloride ion, thus facilitating their capture and coalescence. In this way, the application of the proposed composition efficiently allows the removal of contamination with the chloride ion, contained in the water microdroplets present in the extractant, significantly reducing the consumption of water and avoiding the use of filtering systems.

[0190] After the solvent extraction process the proposed composition can also be applied to the enriched electrolyte for removal of the organic debris present therein. The nanobubbles and microbubbles of the composition coalesce with the microdroplets of organic extractant, increasing their floatability and therefore facilitating their separation and recovery on the surface of the tanks or pools, also allowing the recovery of this debris, avoiding loss of this valuable element

[0191] For application in the organic debris recovery step, the composition comprises that the gases used for obtaining the nanobubbles and microbubbles is oxygen, ozone, air, argon, helium or a mixture thereof. The composition is applied to electrolyte accumulating pools or tanks that are arranged between the solvent extraction and electro-obtaining processes.

Composition and Application Examples

[0192] Example of the proposed composition applied in the mineral leaching step.

[0193] A laboratory test was carried out on leaching columns, with 5 kilos of mixed mineral from a deposit in the second region of Chile, which had a composition of 0.53% of total copper and 0.15% of soluble copper and also 20 liters of electrolyte.

[0194] For them, a preparation of the mineral was carried out at P100 = 1½ (in) and then proceeded to the homogeneous separation of each of the columns. Subsequently, the acid curing process (10 kg/ton) was generated, where the mineral was rolled until the correct curing process of the sample was achieved. This was allowed to stand for a period of 24 hours.

[0195] Subsequently, each of the columns of 1 meter in height was loaded with 1 kilo of mineral, carefully and homogeneously, so as not to damage the glomers and allowed to rest in the column.

[0196] After 3 days, the irrigation step was started with recirculation, with electrolyte that is composed of water (96%), copper sulfate (1%), sulfuric acid (3%) and quillaja saponin (5 ppm), at a rate of 8 (It/hr/m.sup.2)

[0197] In the electrolyte accumulation tank, which feeds the irrigation system pump, the nanobubble generation equipment, fed with pure oxygen, was connected at 20 PSI and 0.8 liter/minute flow.

[0198] After 3 hours, the nano bubbles of oxygen dissolved in the electrolyte, allowed the value of oxygen dissolved in the electrolyte to rise from 10 ppm to between 25 and 27 ppm, also remained in that range throughout the test.

[0199] The efficacy of the proposed composition was noted when performing the measurements of dissolved copper and sulfuric acid. The copper recovery was determined to be 63.2% and at the current prior art this value is close to 45.6%.

[0200] These tests were carried out in duplicate, in a total of 4 columns

[0201] For the preparation of the proposed composition, the following equipment is required: [0202] A supplier source of the gas(s) to be used that is composed of one or more generating equipment of the gas(s) to be used or tank of any supplier of these industrial gases. [0203] A storage tank consisting of a tank of suitable volume containing the water or leaching solution to which it or the nano- or microbubbles of gases will be added. [0204] A nanobubble and/or microbubble generating equipment comprising one or more nanobubble and microbubble generating equipment purchased from a supplier, according to the requirements and needs of use for each process to which the composition is applied. [0205] A storage tank for the prepared composition comprising a pool of suitable volume containing the composition and connected with the duct carrying the prepared composition to the process where it is applied.

[0206] For the control of the preparation of the composition, the same variables and measurement equipment of the solutions used in the processes are used, such as, dissolved oxygen (ppm of 02), Percentage of saturation (%), bubble size (nm), and bubble frequency (%) of the type of bubbles (nano or micro), type and composition of dissolved gases, etc.

[0207] Both the accumulation tanks, as well as the nanobubble and microbubble generating equipment are properly connected by a pumping system, ducts and suitable valves, so that the prepared composition is added to each process.

[0208] The procedure for preparation and application of the composition comprises the following steps: [0209] a) Connect the sources supplying the gas or gases to be injected with the nanobubble generator. [0210] b) Selecting the proportion of gases to be injected [0211] c) Activating the nanobubble and microbubble production source. [0212] d) Connecting the nanobubble generating source to the composition storage tank. [0213] e) Measuring the parameters of size, proportion and composition of gases. [0214] f) Adding nanobubbles to meet the requirements of the process to which the composition is to be applied. [0215] g) Adding nanobubble and microbubble composition to the process to which it will be applied.

Example of the Composition and Application Thereof

[0216] To obtain 1,000 liters of the proposed composition to be applied to the process of leaching minerals into piles, the following procedure must be followed. [0217] a) Connecting the nanobubble generating equipment to an oxygen cylinder (b) [0218] b) Connecting the nanobubble generating source to the accumulation tank (b) [0219] c) Activating the nanobubble generating equipment [0220] d) Measuring dissolved oxygen [0221] e) Adding oxygen nanobubbles until a concentration of 16 ppm of dissolved oxygen is obtained, and [0222] f) Adding the composition to the heap leaching process.

[0223] Example of application of the proposed composition in increasing dissolved oxygen.

[0224] The proposed composition was applied to two different aqueous media to visualize the beneficial effect on the content of oxygen dissolved in type IV water (Maximum 5 .Math.S/cm) and copper refining electrolyte with 1.2 g/l of copper and 15.4 g/l of sulfuric acid, also comparing with the effect of conventional compressed air and the use of oxygen, under different conditions of geographical height, sea level and 2,326 meters above sea level, in addition to the addition of surfactant agent.

[0225] These tests were performed with IDEC FZ1N-04M nanobubble generating equipment and recorded with a portable dissolved oxygen monitor YSI ProODO model and with a preferred size less than 100 nm of nanobubble diameter.

[0226] The results are shown in Table 4.

TABLE-US-00004 Test Barometric Pressure (hPa) Geographic Height (msnm) Flow rate Liq (l/min) Liq temp. (°C) Water Type Gas flow rate(l/min) Gas Type Surfactant Quillay (PPm) Surface Tension (dyne/cm) Amount of turns to the tank Time (sec) Dissolved Oxygen (ppm O.sub.2) 1 1012.9 23 7.5 20.1 Type IV 8.35 compressed air 0 8 10.1 2 1012.9 23 7.5 20.3 Type IV 0.35 compressed air 1 180 10.8 3 1012.9 23 7.5 20.3 Type IV 8.35 compressed air 2 360 11.1 4 1012.9 23 7.5 202 Type IV 0.35 compressed air 3 540 11.5 5 1012.9 23 7.5 20.1 Type IV 8.35 oxygen 0 8 10.2 6 1012.9 23 7.5 20.1 Type IV 0.35 oxygen 1 180 16.2 7 1012.9 23 7.5 20.3 Type IV 0.35 oxygen 2 360 23.4 8 1012.9 23 7.5 202 Type IV 0.35 oxygen 3 540 30.5 9 1012.9 23 7.5 20.5 Copper refining 0.35 oxygen 0 0 6.0 10 1012.9 23 7.5 20.7 Copper refining 0.35 oxygen 1 180 9.0 11 1012.9 23 7.5 20.6 Copper refining 0.35 oxygen 2 360 12.6 12 1012.9 23 7.5 20.6 Copper refining 0.35 oxygen 3 540 16.2 13 759.9 2326 7.5 20.2 Type IV 0.35 compressed air 0 0 7.2 14 759.9 2326 7.5 20.3 Type IV 0.35 compressed air 1 180 7.6 15 759.9 2326 7.5 20.3 Type IV 0.35 compressed air 2 360 8.2 16 759.9 2326 7.5 20.1 Type IV 0.35 compressed air 3 540 8.3 17 759.9 2326 7.5 20.2 Type IV 0.35 oxygen 0 8 7.2 18 759.9 2326 7.5 20.1 Type IV 0.35 oxygen 1 180 12.9 19 759.9 2326 7.5 20.5 Type IV 0.35 oxygen 2 360 17.7 20 759.9 2326 7.5 202 Type IV 0.35 oxygen 3 540 24.3 21 759.9 2326 7.5 20.1 Copper refining 0.35 oxygen 0 0 3.2 22 759.9 2326 7.5 20.3 Copper refining 0.35 oxygen 1 180 4.8 23 759.9 2326 7.5 20.3 Copper refining 0.35 oxygen 2 360 67 24 759.9 2326 7.5 202 Copper refining 0.35 oxygen 3 540 8.6 25 759.9 2326 7.5 21.1 Copper refining 0.35 oxygen 0 0 3.2 26 759.9 2326 7.5 21 Copper refining 0.35 oxygen 11 46.82 1 180 5.8 27 759.9 2326 7.5 21.2 Copper refining 0.35 oxygen 11 46.82 2 360 10.4 28 759.9 2326 7.5 21.1 Copper refining 0.35 oxygen 11 46.82 3 540 16.6

[0227] The results show that the amount of dissolved oxygen present in the water depends on factors such as the quality of the type of water, geographical height and content of salts present, which agrees with what is collected in the prior art.

[0228] In reviewing in detail, it is also observed that, when performing such tests at sea level, the amount of oxygen transferred by applying the composition allows reaching a value of 30 ppm of O.sub.2, after 3 recirculation processes. In comparison, performing these tests only with conventional compressed air achieves only 11.5 ppm of O.sub.2.

[0229] The foregoing indicates that the amount of oxygen present in the atmospheric air does not strongly impact the dissolved oxygen in the sample. By carrying out a similar experiment in a copper refining solution, a value of 16.2 ppm of O.sub.2 is reached at sea level.

[0230] Since the mining operations are over 2,000 meters high in Chile, the importance of this variable must be analyzed, so it repeats these tests with the same conditions, reaching only 8.3 ppm of O.sub.2 for the case of compressed air, with oxygen a value of 24.3 ppm of O.sub.2. Then this experiment is performed with copper refining, a value of 8.6 ppm of O.sub.2 is reached. Finally, the test is carried out with a surfactant, where a concentration of 11 ppm of surfactant Quillaja Saponin is added, observing that a value of 16.6 ppm of O.sub.2 is reached.

[0231] The foregoing makes it possible to affirm that regardless of the characteristics of the available aqueous solutions, by applying the proposed aqueous composition of nano and microbubbles, it is possible to significantly increase the degree of dissolution of a gas such as dissolved oxygen. By significantly increasing the amount of the gas or gases dissolved in the solutions, the beneficial impact of them is increased, in the processes to which they are applied.

Example of Application of the Composition in the Copper Electrorefining Process

[0232] The following table 5 shows the result of the tests carried out to measure the effect of the proposed composition on the anodic efficiency in copper electro refining process as a function of the dissolved oxygen in the electrolyte.

[0233] Three Hull cell assays were carried out, with copper anode, copper foil cathode, electrolyte with 40 grams per liter of dissolved copper and 180 grams per liter of sulfuric acid. For air agitation the air injection agitation system of the Hull cell kit was used and for the electrolyte recirculation a centrifugal pump was used which provided a flow of 1 cubic meter per hour. The anodic efficiency is reflected by the behavior of the current intensity as a function of the working time, for the same voltage. The drop in current intensity is a reflection of the passivation of the anode.

[0234] In each test a voltage of 2.0 volts and a current intensity of 2.0 Amps were applied, which are the standard values for this process and these data were recorded every 10 minutes.

[0235] In test number three, the proposed composition was applied to the electrolyte flow, with nanobubbles of 81 nm size, until a saturation of 175% of oxygen was obtained.

[0236] Test 1: Represents anode efficiency behavior at the current prior art in electro refining cells

TABLE-US-00005 Voltage (V) Current (Amp) Temperature °C Time (min) 2 2 55 10 2 1.8 55 20 2 1.7 55 30 2 1.7 55 40 2.1 1.6 55 50 2.1 1.4 55 60 2.1 1.2 55 70

[0237] Test 2: With agitation, by bubble air injection

TABLE-US-00006 Voltage (V) Current (Amp) Temperature °C Time (min) 2 2 55 10 2 2.1 54 20 2 2.1 54 30 2 2 53 40 2 2 53 50 2 1.8 50 60 2 1.8 50 70

[0238] Test 3: With O.sub.2 Saturation of oxygen (175%), by oxygen nanobubbles of composition.

TABLE-US-00007 Voltage (V) Current (Amp) Temperature °C Time (min) 2 2.1 55 10 2 2.1 55 20 2 2.2 55 30 2 2.2 55 40 2 2.1 55 50 2 2.2 55 60 2 2.2 55 70

[0239] The application of the composition in test number three made it possible to avoid anodic passivation and maintain a high anodic efficiency, without influencing the temperature of the electrolyte or contaminating it.

Description of the Sheets

[0240] Sheet 1 represents a schematic of the connection of the gas supplier source and the nano- and microbubble generating source where: [0241] a) Is the gas supplier source [0242] b) It is the nanobubble and microbubble generating source [0243] c) It is the water accumulation tank or leaching solution. [0244] d) It is the connection system between the nanobubble and microbubble generating source. [0245] e) It is the tank with the prepared composition

[0246] The hatched area represents the presence of nanobubbles and microbubbles Sheet 2 represents a schematic of the hydro-metallurgical process of metal extraction by means of the mineral leaching process where: [0247] f) Is the leaching pile [0248] g) It is the outlet pool of the electrolyte that each pile has [0249] h) It is the pool of electrolyte accumulation coming from the piles [0250] i) It is the solvent extraction process [0251] j) It is the electro-obtaining plant [0252] k) It is the pool of electrolyte accumulation that passes to the pile [0253] I) It is the irrigation duct between the settling pool and the leaching pile [0254] m) It is the forced aeration system of the pile

[0255] Sheet 3 depicts a schematic of the connection of the nanobubble and microbubble generating source to the leaching solution accumulation pool where: [0256] n) It is the pool [0257] The hatched zone represents the leaching solution [0258] Sheet 4 depicts a schematic of a mineral flotation tank where: [0259] ñ) It is the zone of the volume of the solution where the hatched zone represents the sectors in which conventional size bubbles are not present.