MX2013008030A

MX2013008030A - Process for simultaneously lixiviating and recovering manganese dioxide in an electrolytic cell.

Info

Publication number: MX2013008030A
Application number: MX2013008030A
Authority: MX
Inventors: Gretchen Terri Lapidus Lavine; Monserrat Gutierrez Muñoz
Original assignee: Univ Autónoma Metropolitana
Priority date: 2013-07-10
Filing date: 2013-07-10
Publication date: 2015-01-12
Also published as: MX365566B

Abstract

The present invention is related to the mining industry and the industry for treating minerals or materials that contain manganese. More particularly, the invention refers to a process for dissolving and electro recovering manganese dioxide with the same electrolytic cell, which performs both actions with the same energy. The patent particularly refers to a process for improving the speed for extracting manganese from minerals or other materials containing the same, using ferrous ions, such as the direct electro recovery of manganese dioxide from the aforementioned dissolution. The invention consists in a dissolution subjected to an electro-reduction in the cathodic compartment so as to regenerate ferrous ions acting as reducer agents for the mineral phases that contain the manganese. In the preferred embodiment, the electro-oxidation of the manganese dioxide by lixiviation is performed in the anodic compartment of the same cell, being separated in compartments by an anionic membrane.

Description

PROCESS OF SIMULTANEOUS LIXIVIATION AND RECOVERY OF MANGANESE DIOXIDE IN AN ELECTROLYTIC CELL FIELD OF THE INVENTION The present invention relates to the treatment of minerals and the recycling of materials. Specifically, it is related to a process that uses acid solutions and electric current to leach manganese from minerals and other materials that contain it and the electrolytic recovery of manganese dioxide simultaneously in the same electrolytic cell.

BACKGROUND OF THE INVENTION Industrially, manganese is used in the manufacture of steel, ferroalloys, ceramics and some types of batteries. It is found in nature, mainly, as pyrolusite (Mn02) and, to a lesser extent, rhodochrosite (MnC03). For most applications, manganese oxide is required to be of high purity. Over time, manganese-rich deposits have declined and increasingly coexist with other mineral phases. Many times, the presence of certain impurities precludes their use. There are huge reserves of low-grade pyrolusite ore that does not they are being exploited; Due to the high demand of this material, the selective recovery of manganese, from low grade ore (15-25%), has aroused interest in recent years.

At present the benefit of minerals and materials containing manganese use reduction processes at high temperatures (700-900 ° C) in furnaces, with the presence of carbon or SO2, followed by a solution using acid. Recovery, such as manganese dioxide, is carried out in conventional electrolytic cells. Said processing scheme is not very cost effective for minerals or low grade materials (<40% Mn). In recent years, several procedures have been proposed that involve reductive leaching to dissolve manganese in aqueous media. The proposed reductive agents have included, among others, SO2, sugars and ferrous ions (Fe + 2). Unlike the present invention, the use of SO2 requires strict control since this reagent is toxic and very careful, whereas with sugars and other organic substances, the disadvantage is the high temperature required (> 70 ° C). The use of ferrous ion is efficient, but the stoichiometry of the reaction dictates a high requirement (> 2 g Fe per each g Mn).

In an important exploration work (Elsherief, AE (2000), A study of the electroleaching of manganese ore Hydrometallurgy 55 (3): 311-326), Elsherief carried out studies of electroreduction of manganese minerals in sulfuric acid, in an electrolytic cell without separation of anodic and cathodic compartments; nothing more covered the anode so that the mineral did not have physical contact, but without limiting the passage of the cations from one electrode to another. However, the manganese extraction rate was low (< 20% in 75 minutes). On the other hand, Elsherief, supra, found that the addition of ferrous ions to the solution accelerated the reductive reaction of manganese but the design of the cell did not allow to take advantage of this catalytic effect.

Another important attempt to solve the problem of making the recovery of manganese from low grade minerals profitable is carried out by Chen, Y. et al. (Chinese patent application No. CN101709482) which discloses a method for obtaining electrolytic manganese that uses ammonia gas instead of in solution to neutralize and eliminate iron; however, unlike the present invention, in the proposed process it is necessary to remove the iron, in addition to using a higher temperature, with the consequent cost increase, and requires the installation of the ammonia gas pipeline from 2 to 4 meters below the liquid feed level.

On the other hand, Yang, S. et al. (Chinese patent application No. CN101591732) propose a method for the leaching of manganese ore that uses oxygen as an oxidant and although it uses ferrous ions that are oxidized to ferric by oxygen, it presents ... disadvantages of a temperature between 80 to 105 ° C, oxygen handling and the use of a high tank to maintain the necessary pressure for oxidation by oxygen.

Also Qi, M. et al. (Chinese patent application No. CN 102094124) present a method to obtain electrolytic manganese from the leaching of a mineral and using sulfuric acid, ferrous ions and ammonia in aqueous solution; that unlike the present invention, requires a higher concentration of ferrous ions, the ammonia is used to neutralize and the product obtained is metallic manganese, which entails a higher energy consumption both for its obtaining and for its later use unlike dioxide manganese that has a high demand for direct use, for the final applications in which it is used.

Regarding the proposal of Yan, W. et al. (Chinese patent application No. CN 102094119), this also consists of a method for the electrolytic obtaining of metallic manganese from the wet leaching of low grade pyrolusite. This method uses metallic iron and obtains metallic manganese with the aforementioned disadvantages. This method, unlike the present invention, is carried out in two separate stages and therefore takes more time, requires more labor, more equipment and therefore, is more expensive; it also requires purification and decontamination steps of the leaching solution to be subjected to electrolysis.

As already mentioned, electrolytic manganese dioxide has important applications with the disadvantage that its production requires a large consumption of electrical energy and there is no process that uses the same electric current to achieve both purposes: the reductive leaching of minerals or low grade manganese materials (<40% n) and recovery as electrolytic manganese dioxide, which would be very useful and would decrease the consumption of electrical energy and, therefore, lower production costs.

OBJECTIVES OF THE INVENTION An objective of the present invention is to use the combination of ferrous ions and electric current to reduce the oxidation state of the manganese present in minerals and materials for subsequent leaching in an acid solution.

Another objective is to recover the electrolytically pure manganese dioxide with the same electric current used to oxidize the manganese, thus decreasing the energy consumption of the entire process.

A further object of the present invention is to perform the leaching and recovery of the manganese simultaneously.

Other qualities and advantages of the process object of the present invention will become apparent with the following description of the same and the accompanying drawings for illustrative and non-limiting purposes only.

BRIEF DESCRIPTION OF THE INVENTION Broadly speaking, our invention solves the drawbacks of the use of toxic reducing agents and / or high temperatures to extract manganese from minerals and materials that contain it in low proportions, while recovering the manganese in its dioxide form, using the same electrical energy for both stages, that is, the process of the present invention simultaneously carries out the electro-reduction and the electrolytic oxidation in the same electrolytic cell with a membrane that separates the anodic and cathodic compartments. The process of the present invention comprises the following steps: a) Preparation of the ore to be processed, b) Preparation of the electrolytic leaching solution of the cathode compartment, c) Preparation of the electrolytic solution of the anodic compartment, d) Manganese reduction / iron oxidation, e) Filtration of the leaching solution, f) Manganese oxidation / iron reduction, g) Recovery of electrolytic manganese dioxide and h) Recycling of the leaching solution.

BRIEF DESCRIPTION OF THE FIGURES Figure 1 refers to the diagram of the process of simultaneous leaching and recovery of manganese dioxide in an electrolytic cell according to the present invention.

Figure 2 shows the schematic of the electrolytic cell used in the process object of the present invention.

Figure 3 presents a graph of both the percentage of manganese dissolved in the cathodic compartment from the low-grade ore (~ 19% Mn) and the percentage of manganese recovered from the leaching solution, such as Mn02, at the anode, over time that the process lasts.

Figure 4 shows a comparison of manganese extractions with respect to time using different concentrations of ferrous ion added at the start of each extraction.

DETAILED DESCRIPTION OF THE INVENTION The process object of the present invention uses an electrolytic cell open at the top, as shown in Figure 2, in which the anodic and cathodic compartments are divided by a highly selective anionic membrane with a total exchange capacity of 1.1. meq / g (lonac MA 7500), useful up to a maximum current density of 50 amperes / ft2 and stable up to a temperature of 80 ° C. An anode is used consisting of a lead-silver alloy bar (99-1%, respectively) and a cross-linked aluminum cathode (20 ppi). The cell, in its cathode compartment, has an outlet (3) for the leaching solution.

This process takes advantage of the fact that the ferrous ions, liberated by the ore or added intentionally, are oxidized to ferric ions while reacting with the manganese in its states of greater oxidation (?? + 4? +6), as it is found in the ore or material to be leached, reducing its oxidation state and releasing the manganese (Mn + 2) to the acid solution. The ferric ions produced, in turn, are reduced at the cathode with the energy supplied; At the anode, with the same energy, the manganese solution is oxidized, producing the electrolytic manganese dioxide (DME).

The following describes the process for the simultaneous leaching and recovery of manganese dioxide in an electrolytic cell, which It comprises the following stages: a) Preparation of the ore or material to be processed. The manganese ore, can be chosen, but without limitation, from pyrolusite or rhodochrosite, which is crushed in a ball mill enough to reduce the size of ore although for the present process a specific particle size is not required . b) Preparation of the electrolytic solution and leaching of the cathode compartment. Prepare an acid solution containing 1M sulfuric acid, from 200 to 2,000 ppm of ferrous ions (Fe + 2) that can be obtained from any ferrous salt except ferrous chloride (FeCb) and from 5 to 50 g of (NH4) 2S04 / liter solution, which is placed in the cathode compartment of the electrolytic cell.

Because the leaching of the ore or manganese-containing material is carried out in the cathode compartment, the terms "electrolytic solution of the cathode compartment and leaching solution" are used interchangeably herein. c) Preparation of the electrolytic solution of the anodic compartment. In the anodic compartment of the electrolytic cell, the solution resulting from the leaching performed in the cathodic compartment that has previously been used is used; filtered without However, to start the process, prepare a solution containing 1M sulfuric acid, from 4,000 to 10,000 ppm of dissolved manganese (Mn-2), from 5 to 50 g of (NFU ^ SC / liter of solution and from 200 to 2,000 ppm of ferrous ions.

It is worth mentioning that this solution is only prepared at the beginning of the process since afterwards, the anodic compartment is fed with the filtrate of the electrolytic solution and leaching of the cathodic compartment. d) Manganese reduction / iron oxidation. Whenever the electrolytic cell is prepared, the ore or manganese material is fed to leach, through the inlet (1) to the cathodic compartment, the solution is kept under agitation, by means of an electromagnetic stirrer, at 100 to 1,000 rpm , at a temperature of 10 to 50 ° C and subjected to an electric current to reach a potential difference of between 1 to 3 V for a period of between 2 to 8 h to complete the reaction. During this stage the manganese is electro-reduced to Mn-2 allowing it to remain dissolved and the ferrous ions (Fe-2) present in the solution are electro-oxidized to ferric ions (Fe-3). e) Filtration of the leaching solution. Once the reaction is completed, the leaching solution is removed from the cathode compartment with the dissolved manganese (Mn-2) through the outlet (3) that for this purpose is at the bottom of the cathodic compartment of the cell, the solution passes through a common first filter, sufficient to separate liquids from solids [L / S], solid waste and impurities are separated they are removed through the outlet (4), for disposal. The filtrate is the solution with dissolved manganese (Mn + 2) free of impurities that is fed to the anodic compartment of the electrolytic cell through (5). f) Manganese oxidation / iron reduction. The filtrate obtained from the previous step is fed to the anodic compartment where the dissolved manganese (Mn + 2) is electro-oxidized to electrolytic manganese dioxide (DME) for recovery. During this stage the ferric ions (Fe + 3) from the leaching solution are electro-reduced to ferrous ions (Fe * 2). The electrical energy required to reduce manganese in the cathode compartment is the same as that used to produce the DME in the anodic compartment. g) Recovery of the DME. The leaching solution exhausted in Mn + 2 with the solid DME leaves the anodic compartment through (6) and passes to a second common filter, sufficient to separate liquids from solids [L / S], the solid product is recovered through (7) h) Recycling of the leaching solution. The spent leaching solution is separated by some method of separation of liquid solid located in (8), which can be chosen, but without limiting, from between decantation, filtration, centrifugation, and it is fed to a tank to restore its original concentrations of acid and ferrous ions that are added through the inlet (9). Previously, a sample of this spent leaching solution is taken and subjected to a basic chemical analysis to determine the final concentrations of the reagents and add the necessary quantities of each of them until reaching the initial conditions of the leaching solution that will be fed again , it is recycled, to the cathodic compartment through (1).

It should be mentioned that the anodic and cathodic compartments are separated by a reinforced anionic membrane (lonac MA 7500), which is very important to avoid the passage of ferrous ions to the anode, which would negatively affect the oxidation of manganese and consequently, the DME production due to manganese re-oxidation.

The following example is intended to illustrate the invention, not to limit it, any variation thereof falling within the scope of the present invention which consists of electro-recovery of electrolytic manganese dioxide from the leaching solution containing the manganese. dissolved (Mn + 2).

EXAMPLE In the cathode compartment of the electrolytic cell, 30 g of low grade ore (~ 19% Mn in the form of pyrolusite) ground in a ball mill are placed with 250 mL of an aqueous solution of 1.36 g / L FeSÜ4 and 20 g / L (NFU SCh in 1 M H2S04, In the anodic compartment, introduce 250 mL of a solution with the same composition to the previous one to which 6 are added., 500 ppm Mn + 2. In the electrolytic cell the two compartments are divided by a reinforced anionic membrane (lonac MA 7500). The anode consists of a rod of a lead-silver alloy (99-1%, respectively) and the cathode is of cross-linked aluminum (20 ppi). Electric current is applied using a power source, to achieve a potential difference of 1.5 V for 6 hours, both compartments are kept under agitation by an electromagnetic stirrer. The behavior in both compartments is observed in Figure 2. After this time, more than 60% extraction of the manganese contained in the mineral is obtained.; at the anode, about 40% of the manganese contained in the leaching solution fed is recovered as Mn.sub.2.

It is important to mention that the iron in the present invention is considered a load carrier that favors the reduction of manganese because the Fe3 + is easily reduced by the cathode to Fe2 +; it is in solution with a solid particle containing MnC, reduces it to Mn2 + while re-oxidizing forming Fe3 +. This ferric-ferrous cycle eliminates the limiting stage in which the manganese oxide in the solid state has to be found with a nascent hydrogen formed in the cathode, whose half-life is very short.

In order to confirm the catalytic effect, experiments were carried out adding, initially, ferrous sulphate to the sulfuric acid solution. As shown in Figure 4, the comparison between manganese extractions shows a very marked catalytic effect. Especially, in the first hour an extraction kinetics can be noticed that increases as the concentration of ferrous sulphate increases.

The variations that the process modalities for electro-reduction and / or manganese electro-oxidation may have may vary in terms of the concentrations of the leaching solution and the concentration of manganese it contains, however, if at any time using an electro-reduced leaching solution, the process will be considered within the scope of the invention described with degree of rating, in the present application. Likewise, the electrodeposition or oxidation of manganese within the same cell where the pyrolusite is reduced, will also be considered within the scope of the present.

The invention has been described sufficiently and clearly so that a person with average knowledge in the field can reproduce and obtain the results that we mentioned in the present invention. However, any person skilled in the art in which the present invention is circumscribed may be able to make modifications not described in the present application, said modifications shall be understood within the scope of the invention.

Claims

R E I V I N D I C A C I O N S Having described the invention, it is considered as a novelty and therefore the content of the following claims is claimed as property.

1. Process of leaching and recovery of manganese from minerals and materials that contain it characterized because both processes are carried out simultaneously and include the following steps: to. preparation of the ore or material to be processed, by grinding in a ball mill preparation of the electrolytic solution and leaching cathode compartment, containing sulfuric acid, ferrous ions and ammonium sulfate c. preparation of the electrolytic solution of the anodic compartment d. manganese reduction / iron oxidation, which is carried out in the cathodic compartment of the electrolytic cell from a leaching solution to which the mineral or material to be leached is fed filtration of the leaching solution, F. manganese oxidation / iron reduction, which is carried out in the anodic compartment of the electrolytic cell from the leaching solution containing the dissolved manganese, M n +2, g. recovery of electrolytic manganese dioxide, h. recycling of the leaching solution, which once exhausted, is restored the original concentration of its components to be recycled to cathodic behavior.

The process of leaching and recovery of manganese from minerals and materials containing it according to claim 1, characterized in that the electric current required to reduce the manganese in the cathode compartment is the same as that used to produce the electrolytic manganese dioxide in the anodic compartment, a potential difference of between 1 to 3 V.

The process of leaching and recovery of manganese from minerals and materials containing it according to claims 1 and 2 characterized in that the anodic and cathodic compartments are separated by an anionic membrane.

The process of leaching and recovering manganese from minerals and materials that contain it in accordance with the claim 1 characterized in that the ore or material to be leached can be chosen from among pyrolusite or rhodochrosite.

The process of leaching and recovery of manganese from minerals and materials containing it according to claim 1, characterized in that the electrolytic solution of item b) for the cathodic compartment contains sulfuric acid in 1M concentration.

The process of leaching and recovery of manganese from minerals and materials containing it according to claim 1, characterized in that the electrolytic solution of item b) for the cathodic compartment contains ferrous ions in a concentration of between 200 to 2,000 ppm that obtain of any ferrous salt except ferrous chloride.

The process of leaching and recovery of manganese from minerals and materials containing it according to claim 1, characterized in that the electrolytic solution of part b) for the cathodic compartment contains ammonium sulphate in a concentration of between 5 to 50 g / liter of solution.

The process of leaching and recovering manganese from minerals and materials that contain it according to claim 1, characterized in that the electrolytic solution in part c) for the anodic compartment contains dissolved sulfuric acid and manganese, Mn2 +, in 1 M concentration and from 4,000 to 10,000 ppm; respectively.

9. The process of leaching and recovery of manganese from minerals and materials containing it according to claim 1 characterized in that the electrolytic solution of part c) for the anodic compartment contains ammonium sulfate and ferrous ions in a concentration of 5 to 50 g / liter of solution and from 200 to 2,000 ppm; respectively.

10. The process of leaching and recovery of manganese from minerals and materials containing it according to claim 1, characterized in that the reduction of manganese / iron oxidation of Clause d) is maintained in agitation between 100 to 1,000 rpm by a Electromagnetic stirrer and at a temperature between 10 to 50 ° C.

11. The process of leaching and recovery of manganese from minerals and materials containing it in accordance with claim 1, characterized in that the reduction of manganese / iron oxidation of item d) is subjected to an electric current to reach a potential difference. of between 1 to 3 V during a period of between 2 to 8 h.

12. The process of leaching and recovery of manganese to starting from minerals and materials containing it according to claim 1 characterized in that during the reduction of manganese / iron oxidation of part d) the dissolution of up to 60% of the manganese contained in the mineral is obtained.

13. The process of leaching and recovery of manganese from minerals and materials containing it according to claim 1 characterized in that the oxidation of manganese / iron reduction of part f) is maintained in agitation between 100 to 1,000 rpm by an agitator electromagnetic and at a temperature between 10 to 50 ° C.

14. The process of leaching and recovery of manganese from minerals and materials containing it according to claim 1 characterized in that the manganese oxidation / iron reduction of part f) is subjected to an electric current to reach a potential difference of between 1 to 3 V during a period of between 2 to 8 h.

15. The process of leaching and recovery of manganese from minerals and materials containing it according to claim 1 characterized in that during the oxidation of manganese / iron reduction of part f) is recovered as electrolytic manganese dioxide up to 40% of the manganese contained in the leaching solution fed.

16. The process of leaching and recovery of manganese from minerals and materials that contain it according to claim 1, characterized in that recovery of the electrolytic manganese dioxide of item g) is carried out by a liquid solid separation method that can be chosen from between decanting, filtration, centrifugation. SUMMARY The present invention relates to the mining industry and the treatment of minerals or materials containing manganese. Specifically, it is related to a process of dissolution and electrorecovery of manganese dioxide in the same electrolytic cell that achieves both purposes with the same energy. Specifically, the patent refers to a process for improving both the speed of extraction of manganese, from minerals or other materials containing it, using ferrous ions, and the direct electrorecovery of manganese dioxide from said solution. The invention consists of a solution in the cathodic compartment that has been subjected to electro-reduction to regenerate ferrous ions that act as a reducing agent for the mineral phases containing the manganese. In its preferred embodiment, the electrooxidation of the manganese dioxide from the leaching is carried out in the anodic compartment of the same cell, separated into compartments by an anionic membrane.