ES2451567A1 - Procedure for obtaining high purity oxide and magnesium hydroxide from dunites (Machine-translation by Google Translate, not legally binding) - Google Patents

Abstract

Procedure for obtaining high purity oxide and magnesium hydroxide from dunites. The present invention relates to a process for obtaining high purity magnesium compounds, such as magnesium oxide and hydroxide, and other valuable metal by-products from dunites. (Machine-translation by Google Translate, not legally binding)

Description

The present invention relates to a process for obtaining high purity magnesium compounds, such as magnesium oxide and hydroxide, and other valuable metal by-products, from dunites. Therefore, the invention could be framed in the area of mining.

BACKGROUND OF THE INVENTION

Mineral magnesium silicates are an indisputable source of magnesium. For the extraction of the same from mineral magnesium silicates there are various processes based on acid digestion [US2549798, US4100254 and WO 00/017408]. Many of them require complex conditions to prevent the formation of silica gels and colloidal silicic acid, compounds that slow filtration and retain considerable amounts of unwanted salts soluble in the acid.

The acid solution obtained during digestion, brine, contains various impurities, such as compounds of iron, aluminum, nickel, etc. These impurities can be removed from the brine by precipitation in the presence of magnesium oxide, magnesium silicates or with any compound that increases the pH of the brine. For the removal of calcium, for example, calcium sulfate [US3980753] is used. In the case of iron compounds a magnetic separation can be performed, but this separation is only partial and requires further chemical extraction [US2389493].

In US2398493 and US4944928, for example, calcined serpentine is added as a precipitating agent. The drawback of the process described in this patent is related to the silicic acid that the serpentine possesses, since, during calcination, it is transformed into a more soluble form and is retained in the magnesium chloride solution. As a consequence, this high content of silicic acid makes precipitated impurities, such as Fe (OH) 3 among other hydroxides, of gelatinous consistency and, therefore, difficult to filter.

On the other hand, in some acid digestion processes, a final stage of purification of the magnesium chloride solution is required. Ion exchange columns are commonly used [US5091161]. This fact makes the industrial process more expensive, especially with regard to installation and maintenance. In addition, these columns admit only a certain amount of cargo and, consequently, can be an impediment to large-scale productions.

Therefore, there is a need to develop a simple method, which avoids the formation of silica gels, for the continuous extraction of magnesium compounds with high purity from natural magnesium silicates.

DETAILED DESCRIPTION OF THE INVENTION

The inventors have found a simple process for obtaining high purity MgO and Mg (OH) 2 from dunites. With this procedure, valuable metal by-products are also obtained, such as SiO2, Fe2O3, Al2O3, NiO and MnO.

Dunitas are natural magnesium silicates. They belong to the group of ultramafic rocks whose petrological classification is made of hazburgites and dunites, partially serpentinized, which are available in large numbers in various locations worldwide. The typical composition of this type of rock is 32-36% MgO, 38-40% SiO2, 7-9% Fe2O3 and 2-4% Al2O3 and its degree of serpentinization varies between 15% and 75%. Due to the degree of serpentinization, the dunitas are easily soluble in acidic medium.

This procedure prevents the formation of silica gels and also operates continuously. In this way, the process has considerable energy savings over the more conventional methods of generating MgO from MgCl2 brines.

Therefore, in a first aspect, the present invention relates to the process for obtaining magnesium oxide and hydroxide of a purity of at least 97% from dunites, characterized in that it comprises the following steps:

a) grind the dunita,

b) treat the dunite obtained in the previous stage with at least one acid, c) extract the insoluble product formed in the previous stage, d) neutralize the brine obtained in the previous stage with at least one base, e) extract the precipitate obtained in the previous stage, f) thermally decompose the brine obtained in the previous stage, g) hydrolyze the product obtained in the previous stage.

In a preferred embodiment, the dunite obtained in step a) has a particle size of 10 to 500 microns, more preferably 50 to 200 microns.

One of the advantages of the process of the present invention is that the dunitas do not need to be calcined previously, they only need to be ground, which means an energy saving compared to the procedures that are currently used.

In a preferred embodiment the acid from step b) is selected from the list comprising HCl, H2SO4 and HNO3.

Preferably, this acid has been obtained in step f).

Preferably, the acid of step b) is in a concentration of between 10 and 30% by weight. More preferably, in a concentration of between 15 and 25% by weight.

In another preferred embodiment, the product in step b) is at a pH between 0 and 2.

Preferably, step b) is carried out at a temperature between 20 and 200 ° C. More preferably, at a temperature between 50 and 150 ° C.

In another preferred embodiment, step b) lasts between 5 and 150 minutes. More preferably, step b) lasts between 10 and 100 minutes.

Due to the geological characteristics of the dunite, short times are necessary for most of the soluble components of the dunite to pass to the brine and the formation of silica gel is avoided, which is an advantage over other procedures that They require average times of at least one or two hours.

In addition, the solution of dunite in acid is an exothermic process that provides a large part of the heat required to heat and maintain the mixture at that temperature, which saves energy.

In another embodiment, the extraction of step c) is selected from the list of extraction methods comprising settling, filtration, screening, flotation and crystallization. Preferably, the insoluble product formed in step b) is removed by vacuum filtration.

Preferably, the extraction of step c) is carried out in at least 10 minutes.

As a gelatinous cake is not obtained at this stage, the filtration process is rapid and the amount of soluble magnesium retained in the filtration cake is practically negligible.

The filtration cake obtained has a SiO2 content of around 80% which makes it a product of commercial interest per se, for example as a raw material for obtaining other products with high added value such as sodium silicate .

In a preferred embodiment, the base of step d) is selected from the list comprising MgO, NaOH, crude dunite and calcined dunite.

Preferably, the base of step d) has been obtained in step f).

The use of MgO obtained in step f) is preferable since it allows the formation of an additional amount of MgCl2 and prevents the introduction of impurities into the process. It also increases the performance and efficiency of the process.

In another preferred embodiment, step d) is carried out in the presence of an oxidizing agent. More preferably, the oxidizing agent of step d) is selected from the list comprising chlorine, hydrogen peroxide, oxygen and air.

The presence of oxidizing agents, for example, helps to transform Fe + 2 into Fe + 3 and Mn + 2 into Mn + 4 simultaneously, thus forming easily removable Fe and Mn precipitates.

In another preferred embodiment, the pH in step d) is maintained between the values of 1 to 8. More preferably between the values of 4 to 7.

Preferably step d) is performed at a temperature between 20 and 200 ° C. More preferably, at a temperature between 30 and 150 ° C.

In another preferred embodiment, step d) is carried out in 5 to 120 minutes. More preferably in 10 to 60 minutes.

In a preferred embodiment, the extraction of step e) is selected from the list of extraction methods comprising settling, filtration, screening, flotation and crystallization. More preferably the extraction of step e) is a vacuum filtration.

Preferably step e) is carried out in at least 10 minutes.

The filtration process is fast and valuable metal by-products are obtained, such as Fe2O3, Al2O3, NiO and MnO.

In a preferred embodiment, step f) is carried out at a temperature between 200 and 3000 ° C. More preferably at a temperature between 300 and 2500 ° C.

In another preferred embodiment, step f) is carried out in 5 to 150 minutes. More preferably in 45 to 90 minutes.

In this stage f) a large part of the acid used in stage b) and the base used in stage d) are recovered.

The hot mixture of HCl and H2O gases generated during decomposition is recycled through the system, where it is used in the indicated concentration.

In a preferred embodiment, step g) is carried out at a temperature between 20 and 300 ° C. More preferably at a temperature between 30 and 250 ° C.

Preferably, step g) is carried out in 5 to 240 minutes. More preferably in 20 to 90 minutes.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1: Flow diagram of the process of obtaining high purity magnesium oxide and hydroxide a from dunita FIG. 2: Flow chart of the process carried out in example 1. FIG. 3: Flow chart of the process carried out in example 2. FIG. 4: Flow chart of the process carried out in example 3.

EXAMPLE

Figure 1 presents the flow chart of the process for obtaining high purity magnesium oxide from dunites.

Example 1, schematized in Figure 2.

10 g of raw ground dunite below 100 microns, containing 36.01% MgO, 40.66% SiO2, 8.86% Fe2O3 and 2.60% Al2O3, were dissolved in 44 ml of 20% hydrochloric acid, for a period of 30 minutes at temperature of 85ºC with continuous agitation, reaching a pH close to zero. After this period of time, 6.1 g insoluble product composed of 80% SiO2 was recovered by vacuum filtration. The filtration process lasted 10 minutes. The resulting MgCl2 acid brine was maintained at a temperature around 65 ° C, and mixed with 2.2 g of MgO (97% MgO) as a base and with 0.5 ml of 17% H2O2 as oxidizing agent. The pH value increased to approximately 5.5 and the precipitation was completed after 30 minutes. The precipitated material was separated by vacuum filtration to obtain 1.2 g of by-product. This material contained 0.47 g Fe2O3, 0.07 g Al2O3 and 0.33 g of calcination loss. Finally, the pure MgCl2 brine was subjected to a thermal decomposition process at a temperature of 600 ° C resulting in the formation of 5.0g of MgO of 97% purity, and the recovery of 33 ml of 20% HCl.

Example 2, schematized in Figure 3.

10 g of a raw ground serpentine below 100 microns (32.22% MgO, 41.09% SiO2, 7.19% Fe2O3 and 3.73% Al2O3) were treated similarly to Example 1, with 40 ml of 20% HCl. The amount of SiO2 recovered was 5.5 g, lower than the amount obtained in the previous Example, which is in accordance with the higher degree of serpentinization of the starting material. The acidic brine was mixed with

2.5 g of MgO of 97% purity and the temperature of the mixture was maintained at 65 ° C. The pH value increased rapidly to approximately 5.5 and the precipitation was completed after 30 minutes. The precipitated material was removed by vacuum filtration, resulting in a filter cake in an amount of 2.7 g. The remaining pure brine was subjected to a thermal decomposition process resulting in the formation of 4.6 g of MgO of 97% purity, and the recovery of 65% of 20% HCl.

Example 3, schematized in Figure 4.

10 g of crude olivine (<100 microns) with a composition of 46.75% MgO, 41.54% SiO2, 8.86% Fe2O3 and 0.66% Al2O3 were treated similarly to Example 1. After adding 59 ml of 20% HCl, they were obtained

7.5 g of an insoluble gelatinous residue and difficult to wash. In this case, the filtration process took 40 minutes. Only 70% of MgO passed into acidic brine, as expected, according to the lower degree of olivine alteration with respect to dunite or serpentine. The acidic brine was mixed with 2.5 g of 97% MgO for 30 minutes at 65 ° C. The precipitated material was removed by vacuum filtration, resulting in a filter cake in the amount of 1.0 g. The remaining pure brine was subjected to a thermal decomposition process resulting in the formation of 4.6 g of MgO of 97% purity, and the recovery of 20 ml of 20% HCl.

Example 4

5 g of the highly reactive MgO and with a purity of 97 %% MgO, were reacted with 30 ml of water, for a period of 60 minutes at a temperature of 100-120 ° C, with continuous stirring. After this period of time, 6.7 g of Mg (OH) 2 of 97% purity were recovered by vacuum filtration.

Claims (37)

one.

Process for obtaining magnesium oxide and hydroxide of a purity of at least 97% from dunites, which comprises the following steps:

a) grind the dunita, b) treat the dunite obtained in the previous stage with at least one acid, c) extract the insoluble product formed in the previous stage, d) neutralize the brine obtained in the previous stage with at least one base, e) extract the precipitate obtained in the previous stage, f) thermally decompose the brine obtained in the previous stage, g) hydrolyze the product obtained in the previous stage.

2.

Method according to the preceding claim, wherein the dunite obtained in step a) has a particle size of 10 to 500 microns.

3.

Method according to the preceding claim, wherein the dunite obtained in step a) has a particle size of 50 to 200 microns.

Four.

Process according to any of the preceding claims, wherein the acid of step b) is selected from the list comprising HCl, H2SO4 and HNO3.

5.

Process according to any of the preceding claims, wherein the acid of step b) has been obtained in step f).

6.

Process according to any of the preceding claims, wherein the acid of step b) is in a concentration of between 10 and 30% by weight.

7.

Process according to the preceding claim, wherein the acid of step b) is in a concentration of between 15 and 25% by weight.

8.

Process according to any of the preceding claims, wherein the product in step b) is at a pH between 0 and 2.

9.

Process according to any of the preceding claims, wherein step b) is carried out at a temperature between 20 and 200 ° C.

10.

Method according to the preceding claim, wherein step b) is carried out at a temperature between 50 and 150 ° C.

eleven.

Method according to any of the preceding claims, wherein step b) lasts between 5 and 150 minutes.

12.

Method according to the preceding claim, wherein step b) lasts between 10 and 100 minutes.

13.

Method according to any of the preceding claims, wherein the extraction of step c) is selected from the list of extraction methods comprising decantation, filtration, screening, flotation and crystallization.

14.

Method according to the preceding claim, wherein the extraction of step c) is a vacuum filtration.

fifteen.

Method according to any of the preceding claims, wherein the extraction of step c) is carried out in at least 10 minutes.

16.

Process according to any of the preceding claims, wherein the base of step d) is selected from the list comprising MgO, NaOH, crude dunite and calcined dunite.

17.

Method according to any of the preceding claims, wherein the basis of step d) has been obtained in step f).

18.

Process according to any of the preceding claims, wherein step b) is carried out in the presence of an oxidizing agent.

19.

Process according to the preceding claim, wherein the oxidizing agent of step d) is selected from the list comprising chlorine, hydrogen peroxide, oxygen and air.

twenty.

Method according to any of the preceding claims, wherein the pH in step d) is maintained between the values of 1 to 8.

twenty-one.

Method according to the preceding claim, wherein the pH in step d) is maintained between the values of 4 to 7.

22

Process according to any of the preceding claims, wherein step d) is carried out at a temperature between 20 and 200 ° C.

2. 3.

Process according to the preceding claim, wherein step d) is carried out at a temperature between 30 and 150 ° C.

24.

Method according to any of the preceding claims, wherein step d) is carried out in 5 to 120 minutes.

25.

Method according to the preceding claim, wherein step d) is carried out in 10 to 60 minutes.

26.

Method, according to any of the preceding claims, wherein the extraction of step e) is selected from the list of extraction methods comprising decantation, filtration, screening, flotation and crystallization.

27.

Method according to the preceding claim, wherein step e) is a vacuum filtration.

28.

Method according to any of the preceding claims, wherein step e) is carried out in at least 10 minutes.

29.

Process according to any of the preceding claims, wherein step f) is carried out at a temperature between 200 and 3000 ° C.

30

Process according to the preceding claim, wherein step f) is carried out at a temperature between 300 and 2500 ° C.

31.

Method according to any of the preceding claims, wherein step f) is carried out in 5 to 150 minutes.

32

Method according to the preceding claim, wherein step f) is carried out in 45 to 90 minutes.

33.

Process according to any of the preceding claims, wherein step g) is carried out at a temperature between 20 and 300 ° C.

3. 4.

Process according to the preceding claim, wherein step g) is carried out at a temperature between 30 and 250 ° C.

35

Method according to any of the preceding claims, wherein step g) is carried out in 5 to 240 minutes.

36.

Method according to the preceding claim, wherein step g) is carried out in 20 to 90 minutes.

FIG. 1 FIG. 2 FIG. 3. FIG. Four. SPANISH OFFICE OF THE PATENTS AND BRAND Application no .: 201231488 SPAIN Date of submission of the application: 26.09.2012 Priority Date: REPORT ON THE STATE OF THE TECHNIQUE 51 Int. Cl.: C01F5 / 02 (2006.01) C01F5 / 14 (2006.01) RELEVANT DOCUMENTS

Category

56 Documents cited Claims Affected

X

US 7329396 B2 (HARRIS et al.) 12.02.2008, 1-36

column 9, line 24 - column 16, line 28; Figure 1.

TO

WO 2005098062 A1 (HOVHANNISYAN) 20.10.2005, 1-36

page 5, line 10 - page 6, line 12.

TO

US 7749476 B2 (CONSTANTZ et al.) 06.07.2010, 1-36

column 18, line 14 - column 19, line 33.

Category of the documents cited X: of particular relevance Y: of particular relevance combined with other / s of the same category A: reflects the state of the art O: refers to unwritten disclosure P: published between the priority date and the date of priority submission of the application E: previous document, but published after the date of submission of the application

This report has been prepared • for all claims • for claims no:

Date of realization of the report 13.09.2013

Examiner A. Rúa Aguete Page 1/4

REPORT OF THE STATE OF THE TECHNIQUE Application number: 201231488 Minimum documentation searched (classification system followed by classification symbols) C01F Electronic databases consulted during the search (name of the database and, if possible, terms of search used) INVENES, EPODOC State of the Art Report Page 2/4  WRITTEN OPINION Application number: 201231488 Date of Completion of Written Opinion: 13.09.2013 Statement

Novelty (Art. 6.1 LP 11/1986)

Claims Claims 1-36 IF NOT

Inventive activity (Art. 8.1 LP11 / 1986)

Claims Claims 1-36 IF NOT

The application is considered to comply with the industrial application requirement. This requirement was evaluated during the formal and technical examination phase of the application (Article 31.2 Law 11/1986).  Opinion Base.- This opinion has been made on the basis of the patent application as published. State of the Art Report Page 3/4  WRITTEN OPINION Application number: 201231488  1. Documents considered.- The documents belonging to the state of the art taken into consideration for the realization of this opinion are listed below.

Document

Publication or Identification Number publication date

D01

US 7329396 B2 (HARRIS et al.) 12.02.2008

 2. Statement motivated according to articles 29.6 and 29.7 of the Regulations for the execution of Law 11/1986, of March 20, on Patents on novelty and inventive activity; quotes and explanations in support of this statement The object of the invention is a process for obtaining magnesium oxide and hydroxide of a purity of at least 97% comprising the steps of grinding the dunite, treatment with an acid, extraction of the insoluble product formed in the previous stage, neutralize the brine obtained with a base, extract the precipitate obtained, thermally decompose the brine obtained and hydrolyze the product obtained. Document D1 discloses a process for obtaining magnesium oxide from dunites or other types of ultramaphic rocks, which includes the steps of grinding the mineral, leaching with hydrochloric acid at a temperature of about 100 ° C and with a pH of the leaching included between 0.7 and 2.5, solid-liquid separation that can be of the vacuum filtration type, addition of an oxidizing agent of the Cl2 or H2O2 type and pH adjustment by the addition of recovered MgO, solid-liquid separation in one or two stages and pyrohydrolysis to obtain magnesium oxide of very high purity, obtaining streams of MgO and HCl that are recycled in the process. (See figure 1). Therefore, the invention as set forth in claims 1 to 36 of the application is not new. (Art. 6 LP). State of the Art Report Page 4/4