The preparation method of high-purity magnesium oxide powder
Technical field
The present invention relates to a kind of preparation method of high-purity magnesium oxide powder, the inventive method cost is low, belongs to the hydrometallurgy field.The powder that utilizes the present invention to prepare can be used for preparing and be used for the MgO optical filming material of PDP (plasma panel) with the medium layer film.
Background technology
The preparation method of MgO is a lot of at present, and high-purity MgO is also had related preparation research, but is not reported with carrying out the separation of specific impurities ionic to PDP.Domestic present high-purity MgO seldom obtains, and does not more realize mass production production.External to the preparation of PDP with the MgO Coating Materials, carried out relevant control of purity research, but with MgCl
2For the relevant purification techniques of raw material is not seen open report.PDP mainly is metallic impurity ion Ca, Si, Fe, Al with responsive impurity in the MgO material.The existence of metals ion cause the MgO film light see through poor, secondary electron yield is low, has a strong impact on MgO depositing of thin film and growth, therefore must realize separation to these several foreign ions.
Summary of the invention
The object of the present invention is to provide a kind of preparation method of high-purity magnesium oxide powder.
For realizing above-mentioned purpose, the present invention takes following technical scheme:
Scheme one:
A kind of preparation method of high-purity magnesium oxide powder may further comprise the steps:
(1) with deionized water dissolved chlorine magnesium, the preparation magnesium chloride solution;
(2) calculate the initial deposition pH value of each foreign ion, confirm Fe, Al, Si contamination precipitation pH scope, in the magnesium chloride solution of step (1) gained, add alkaline reagents; Regulate the pH value, make Fe, Al, Si contamination precipitation, filter; Remove Fe, Al, Si impurity, it is for use to filtrate;
(3) calculate the initial deposition pH value of Mg, confirm the deposition pH scope of Mg, in the filtrating that obtains, add alkaline reagents, Mg is precipitated, filtering separation obtains filter cake;
(4) filter cake that obtains is kept 120 ℃ of constant temperature in baking oven, oven dry obtains Mg (OH)
2
(5) with Mg (OH)
2Put into chamber type electric resistance furnace, 920 ℃ of calcining at constant temperature 3 hours, fragmentation, screening obtains the MgO powder.
Scheme two:
A kind of preparation method of high-purity magnesium oxide powder may further comprise the steps:
(1) with deionized water dissolved chlorine magnesium, the preparation magnesium chloride solution;
(2) calculate the initial deposition pH value of each foreign ion, confirm Fe, Al, Si contamination precipitation pH scope, in the magnesium chloride solution of step (1) gained, add alkaline reagents; Regulate the pH value, make Fe, Al, Si contamination precipitation, filter; Remove Fe, Al, Si impurity, it is for use to filtrate;
(3) in the filtrating that step (2) obtains, add ammonium oxalate solution, wherein the mol ratio of ammonium oxalate and magnesium chloride is 1: 9~11, and sedimentation and filtration is removed Ca impurity, and it is for use to filtrate;
(4) calculate the initial deposition pH value of Mg, confirm the deposition pH scope of Mg, in the filtrating that obtains, add alkaline reagents, Mg is precipitated, filtering separation obtains filter cake;
(5) filter cake that obtains is kept 120 ℃ of constant temperature in baking oven, oven dry obtains Mg (OH)
2
(6) with Mg (OH)
2Put into chamber type electric resistance furnace, 920 ℃ of calcining at constant temperature 3 hours, fragmentation, screening obtains the MgO powder.
A kind of optimized technical scheme is characterized in that: the sedimentation and filtration described in the said step (3) refilters after 24 hours for leaving standstill.
A kind of optimized technical scheme is characterized in that: the concentration of the described ammonium oxalate solution of step (3) is 0.1~2mol/L.
A kind of optimized technical scheme is characterized in that: the concentration of the described magnesium chloride solution of step (1) is 2~3mol/L.
A kind of optimized technical scheme is characterized in that: being filtered into described in the said step (2) left standstill after 24 hours and refiltered.
A kind of optimized technical scheme is characterized in that: described alkaline reagents is ammoniacal liquor or volatile salt.
The present invention prepares the high-purity magnesium oxide powder through step-by-step precipitation method, and the main raw material of use is: magnesium chloride, ammoniacal liquor, volatile salt and deionized water.Preparation technology of the present invention comprises: preparation of raw material, neutralization precipitation technology and fractional precipitation impurity separating technology.
Preparing method's of the present invention characteristics: according to dissolving-equilibrium principle, to MgCl
2In the major metal foreign ion that contains carry out the distribution precipitate and separate;
The solubility product Ksp data of table 1, various materials
Molecular formula |
Mg(OH)
2 |
Ca(OH)
2 |
Al(OH)
3 |
Fe(OH)
2 |
xSiO
2·yH
2O
|
Solubility product Ksp |
1.8×10
-11 |
5.5×10
-6 |
1.3×10
-33 |
8.0×10
-16 |
10
-25~10
-30 |
Visible by table 1, the solubility product data differences of these oxyhydroxide is very big, therefore regulates MgCl
2The pH value of solution can be so that the existence of these foreign ions changes.According to the principle of fractional precipitation, the pH value of control different step can realize special metal ionic precipitate and separate.
Ca in raw material
2+When content is higher, Ca
2+Initial deposition pH value reduce, might cause Ca in the finished product
2+Content higher.Therefore, before the deposition beginning, be necessary earlier Ca
2+Get rid of.As shown in table 2, be the solubility product Ksp data of oxalate, therefore, can utilize CaC
2O
4The characteristics that solubility product is little are with Ca
2+Precipitate and separate in advance.
The solubility product Ksp data of table 2 oxalate
Molecular formula |
MgC
2O
4 |
CaC
2O
4 |
Solubility product Ksp |
8.57×10
-5 |
2.57×10
-9 |
The invention has the advantages that:
1, with respect to other purifying technique, the method that the present invention adopts is simple, is easy to mass production production, and cost is low;
2, the MgO powder of preparation, its metallic impurity ion satisfies the requirement of PDP medium layer to the MgO material purity, can be used for preparing the MgO optical filming material.
Through embodiment the present invention is further specified below, but and do not mean that restriction protection domain of the present invention.
Embodiment
Embodiment 1
Take by weighing a certain amount of commercially available MgCl
26H
2The O raw material, the magnesium chloride solution 5L of preparation 2mol/L through using its major impurity ion content of aes determination is: [Ca
2+]=0.006mol/l, [Fe
2+]=0.002mol/l, [Al
3+]=0.1mol/l, [Si
4+]=0.1mol/l.
According to the dissolution equilibrium principle, utilize the solubility product data computation major impurity ion and the initial deposition of the Mg ionic pH value of different ions oxyhydroxide.Through calculating the initial deposition of each ionic pH value such as table 3.
Table 3, the initial deposition of each ion pH value
Ion |
Initial deposition pH value |
Mg
2+ |
8.5 |
Ca
2+ |
12.5 |
Fe
2+ |
7.8 |
Al
3+ |
3.4 |
Si
4+ |
6.7~8 |
Toward MgCl
2Add NH in the solution
3H
2O, pH value to 7.8~8.3 of regulator solution can be known by table 2, Fe, Al, Si foreign ion precipitate; Fully stir, treat the pH value stabilization of solution after, filter, it is for use to filtrate; Filter cake is analyzed Si, Fe, Al foreign matter content in this slag specimen, result such as table 3 through drying and calcining with atomic emission spectrometry.
In filtrating, add NH
3H
2O carries out neutralization precipitation, under fully stirring, controls its pH value between 9~11.5, when the pH value of solution value surpasses 11.5, stops to add NH
3H
2O, deposition stops; Can know by table 2, at this moment Ca
2+Can not precipitate.
Filter, get filter cake, filter cake is put into baking oven keep 120 ℃ of freeze-day with constant temperature, oven dry obtains Mg (OH)
2
With Mg (OH)
2Put into chamber type electric resistance furnace, in 920 ℃ of following calcining at constant temperature 3 hours, fragmentation, screening obtains the MgO powder, with atomic emission spectrometry the major impurity content of prepared MgO powder is analyzed result such as table 4.
Table 4, impurity ion content
Foreign ion |
Si |
Fe |
Al |
Ca |
MgO powder (ppm) |
20 |
8 |
32 |
20 |
The isolating slag specimen of fractional precipitation (weight %) |
~1% |
~0.1% |
~0.1% |
>1% |
Can find out that the Si in the MgO powder, Fe, Al, Ca impurity are effectively separated.
Embodiment 2
Take by weighing a certain amount of commercially available MgCl
26H
2The O raw material through measuring its major impurity ion content is: [Ca
2+]=0.01mol/l, [Fe
2+]=0.0026mol/l, [Al
3+]=0.15mol/l, [Si
4+]=0.1mol/l.Magnesium chloride solution 10L with deionized water preparation 3mol/L is divided into 2 parts with solution;
According to the dissolution equilibrium principle, utilize the solubility product data computation major impurity ion and the initial deposition of the Mg ionic pH value of different ions oxyhydroxide.Through calculating the initial deposition of each ionic pH value such as table 5.
Table 5, the initial deposition of each ion pH value
Ion |
Initial deposition pH value |
Mg
2+ |
8.4 |
Ca
2+ |
12.4 |
Fe
2+ |
7.7 |
Al
3+ |
3.3 |
Si
4+ |
6.7~8 |
In first part, add ammoniacal liquor, pH is between 8~8.5 in adjustment, stirs, and Fe, Al, Si foreign ion precipitate, and leave standstill 24 hours after-filtration, and it is for use to filtrate; With 1.4L deionized water dissolving 200g ammonium oxalate, get the 1mol/L ammonium oxalate solution, this ammonium oxalate solution is added in the filtrating (mol ratio of ammonium oxalate and magnesium chloride is 1: 15), fully stir, place 24 hours after-filtration, remove the Ca ion, it is for use to filtrate; In filtrating, add ammoniacal liquor, control pH value is carried out neutralization precipitation between 12.5~13; Washing, filtration; Filter cake is put into baking oven keep 120 ℃ of freeze-day with constant temperature, oven dry obtains Mg (OH)
2With Mg (OH)
2Put into chamber type electric resistance furnace, in 920 ℃ of following calcining at constant temperature 3 hours, fragmentation, 1. screening obtains the MgO powder, adopts atomic emission spectrometry that prepared MgO powder is carried out purity check, result such as table 5.
Contrast experiment: in second part, directly add the ammoniacal liquor neutralization precipitation, fully stir, after the pH value of solution value reaches 13.0, stop to add.Washing, filtration; Filter cake is put into baking oven keep 120 ℃ of freeze-day with constant temperature, oven dry obtains Mg (OH)
2With Mg (OH)
2Put into chamber type electric resistance furnace, in 920 ℃ of following calcining at constant temperature 3 hours, fragmentation, 2. screening obtains the MgO powder, adopts atomic emission spectrometry that prepared MgO powder is carried out purity check, result such as table 6.
Table 6, MgO powder purity
Foreign matter content (ppm) |
Si |
Fe |
Al |
?Ca |
The MgO powder 1. |
20 |
8 |
32 |
?20 |
The MgO powder 2. |
2000 |
150 |
450 |
?>10000 |
Can find out that Si, Fe, Al, the Ca impurity of MgO powder in is 1. effectively separated.
Embodiment 3
Adopt the raw material that uses among the embodiment 2, the magnesium chloride solution 10L with deionized water preparation 3mol/L is divided into 2 parts with solution.
In first part, add ammoniacal liquor, pH is between 8~8.5 in adjustment, stirs, and leaves standstill 24 hours after-filtration, removes Fe, Al, Si ion, and it is for use to filtrate; With 300ml deionized water dissolving 40g ammonium oxalate, be mixed with the ammonium oxalate solution of 1mol/l, this ammonium oxalate solution is added in the filtrating (mol ratio of ammonium oxalate and magnesium chloride is 1: 100), fully stir, leave standstill 24 hours after-filtration; Be adjusted to sal volatile with ammoniacal liquor and bicarbonate of ammonia, according to CO
3 2-Excessive 5%~30%, add in the filtrating, neutralization precipitation, control pH value is between 10~11.5; Washing, filtration are put into baking oven with filter cake and are kept 120 ℃ of freeze-day with constant temperature, and oven dry obtains magnesiumcarbonate MgCO
3Powder; With MgCO
3Put into chamber type electric resistance furnace, in 920 ℃ of following calcining at constant temperature 3 hours, fragmentation, 1. screening obtains the MgO powder, adopts atomic emission spectrometry that prepared MgO powder is carried out purity check, result such as table 7.
The contrast experiment: be adjusted to sal volatile with ammoniacal liquor and bicarbonate of ammonia, directly add second part of magnesium chloride solution and carry out neutralization precipitation, control pH value is between 10~11.5; Washing, filtration are put into baking oven with filter cake and are kept 120 ℃ of freeze-day with constant temperature, and oven dry obtains MgCO
3With MgCO
3Put into chamber type electric resistance furnace, in 920 ℃ of following calcining at constant temperature 3 hours, fragmentation, 2. screening obtains the MgO powder, adopts atomic emission spectrometry that prepared MgO powder is carried out purity check, result such as table 7.
Can find out that the impurity of MgO powder in is 1. effectively separated, with former examples relatively, Ca content is lower in the final powder product, but Fe, Al content are high slightly.
Impurity analysis is following:
Table 7, MgO powder purity
Foreign matter content (ppm) |
Si |
Fe |
Al |
?Ca |
The MgO powder 1. |
20 |
25 |
65 |
?10 |
The MgO powder 2. |
3000 |
160 |
660 |
?>10000 |
To the requirement of PDP, adopt the high-purity MgO powder of the present invention's preparation according to Japanese Tateho company, Korea S's Mitsubishi,, can satisfy the requirement of PDP screen MgO medium layer because Si in the powder, Fe, Al, four kinds of foreign matter contents of Ca are lower with the MgO Coating Materials.