KR960003802B1 - Method of preparing cerium oxide hydrate powder - Google Patents

Abstract

This relates to manufacturing method of cerium hydroxide. The method comprises :1)leaching cerium ore with nitric acid; 2)adding phosphoric acid to the leached solution; 3)forming LnPO4 by heating at 200-850 deg.C for 1-3 hrs.; 4)mixing LnPO4 and caustic soda and fritting at 300-400 deg.C; and 5)washing it with water. Phosphoric acid is such as NaH2PO4, Na3PO4 and H3PO4.

Description

Process for preparing cerium hydride powder

1 is a manufacturing process diagram of the present invention.

2 is an X-RD graph according to the heating temperature.

3 is a SEM photograph of cerium hydride powder.

The present invention relates to a method for producing cerium hydride (CeO ₂ · nH ₂ O) powder, and more specifically, to a phosphate solution of nitric acid leaching solution of cerium (Ce) concentrate, phosphate rare earth (LnPO ₄ : Ln is a generic term for rare earth) The present invention relates to a method for producing cerium hydride powder having high quality and fine particle size distribution of cerium without any refining process or pulverization process by mixing and calibrating it with caustic soda.

The cerium hydride powder made by the present invention has a small and uniform particle as the main component of cerium, and may be used as an abrasive, a ceramic raw material, or the like for a TV cathode ray tube and a stove through separate heat treatment as necessary.

In general, the preparation of rare earth metal powder by alkali frit uses monazite, a phosphate mineral, which is described in (9th Intermaionil Mineral Processing Cong. Proc., Praha. Czec. 1970. YSKim & APProsser). It has been reported, and there is a Japanese Patent Publication No. 29-8157 as a patent.

According to the above technique, the monazite is pulverized to about 200 mesh, mixed with caustic soda (NaOH) solution, heated at about 150 ° C. for 5 hours, washed with warm water, and an extraction residue is obtained. The extracted residue is dissolved in hydrochloric acid to precipitate the rare earth hydroxide and dry to obtain the rare earth hydroxide having a cerium oxide content of about 80%.

Further, according to Japanese Patent Application Laid-Open No. 62-60833, after grinding the rare earth ore in the presence of caustic soda, the ground ore is mixed with an aqueous solution of caustic soda and heated at 130 to 180 DEG C for 1 to 10 hours, washed with water and washed Obtain the earth hydroxide.

However, the rare earth oxide obtained by alkali-refining monazite by these prior arts contains a large amount of thorium (Th), a radioactive substance harmful to the human body as shown in the following table, and is used as a high-grade abrasive or ceramic raw material due to its low level of cerium. There is a disadvantage to this.

TABLE 1

Accordingly, the present invention has been made to solve the above-mentioned problems, leachate of cerium (Ce) concentrate in the market cheaply using nitric acid and phosphate ash by adding a solution containing phosphoric acid (PO ₄ ) ions to this leaching solution The purpose of the present invention is to provide a cerium hydroxide powder having no thorium (Th), high quality of cerium, and a fine particle size without a separate cerium (Ce) refining process or a pulverization process.

Hereinafter, the present invention will be described in detail.

The present invention is cerium (Ce) of the concentrate nitric acid (HNO ₃₎ in the leaching to process by heating the resulting precipitate was added to the phosphoric acid solution in the step of the immersion liquid to obtain the leachate to obtain a phosphoric acid rare earth (LnPO ₄₎ and the phosphate hoeto (LnPO ₄ ) Is mixed with caustic soda, and the product obtained by fritting at 300 to 400 ° C. is washed with water, thereby obtaining a powder having a high quality of cerium.

This is shown in FIG.

According to the present invention, first, cerium oxide, which is cerium oxide, is leached with nitric acid, and then separated into a residue and a leaching liquid by a conventional solid-liquid separation method.

When the phosphate solution is added to the equivalent ratio (1 to 3 times) while stirring the leachate at room temperature, LnPO ₄ is reacted by the following reaction. A precipitate of nH ₂ O can be obtained.

Ln (NO ₃ ) ₃ + Na ₃ PO ₄ = LnPO ₄ nH ₂ O + ₃ NaNO ₃

Here, the phosphate solution refers to a solution containing phosphate ions (PO ₄ ) capable of binding to GML earth elements. The phosphate solution used in the present invention was used by dissolving sodium phosphate (Na ₃ PO ₄ ) in water. Na ₂ HPO ₄ , NaH ₂ PO ₄ , H ₃ PO ₄ and the like can be selected from among phosphates which are easily soluble in water.

In addition, various types of phosphates that can be combined with cerium to form phosphates can be used without limitation.

LnPO ₄ by conventional solid-liquid separation A precipitate in the form of nH ₂ O is separated from the solution, and then the precipitate is heated at a temperature in the range of 200 to 800 ° C., preferably at 400 to 500 ° C. for 1 to 2 hours to remove the crystallized water, thereby obtaining LnPO ₄ powder. .

In order to effectively carry out the alkaline frit process, it must have the same crystallinity as that of natural monazite.

2nd degree LnPO ₄ The X-RD graph according to the heating temperature of nH ₂ O is shown, which is heated in the temperature range of 200 to 850 ° C. of which b is in good agreement with the standard X-PD peak of LnPO ₄ .

The LnPO ₄ powder obtained as described above was mixed with caustic soda powder in a weight ratio of about 1: 1 using a ball mill or pulverizer, and then the mixture was placed in an iron container and fritted at 320 to 400 ° C. to induce the following reaction. do.

LnPO ₄ +3 NaOH = Ln (OH) ₃ + Na ₃ PO ₄

CePO ₄ +3 NaOH = CeO ₂ nH ₂ O + Na ₃ PO ₄

The fritted mass is easily loosened in water, so caustic soda and sodium phosphate mixed in the mass can be removed by washing with water.

After washing with water, drying may be carried out according to a conventional drying method as necessary. The powder thus obtained has the advantage that the quality of cerium oxide is high (90 to 95%) and has a fine and uniform particle size of 1 mu m or less.

Since the cerium oxide prepared by the above-described prior art is coarse in particles, fine powder is obtained through mechanical grinding in order to use it as an abrasive or ceramic raw material. Thus, the obtained particles are inert and unstable in surface. The powder produced by the invention has a stable structure surface through chemical treatment, which is advantageous when used as an abrasive or a ceramic raw material.

The present invention will be described in more detail with reference to the following examples.

EXAMPLE

1Kg of cerium concentrate having the composition shown in Table 1 was placed in a glass reactor containing 10N nitric acid (1.5 times the reaction equivalent ratio) and stirred for 3 hours.

Since the reaction time may vary depending on the particle size of the concentrate, the present invention is not limited to the composition of Table 1.

[Table 1] Composition of cerium concentrate

68.61% of Ln ₂ O _{3 is} 62.93% of CeO _{2 and} 5.68% of other rare earth oxides (mainly La, Nd, Pt). (62.93 + 5.68 = 68.61%)

The reaction slurry obtained after stirring was separated by solid-liquid separation using a vacuum filter to obtain a leachate. The leachate was added to a glass reactor, and 5 mol (M) phosphoric acid solution was slowly added to 1.5 times the reaction equivalent ratio.

After stirring for about 1 hour, the resulting slurry was solid-liquid separated in the same manner to obtain a solid powder, which was heated at 450 ° C. for 1 hour.

The rare earth phosphate powder and caustic soda were obtained in a ball mill container with a weight ratio of 1: 1, mixed for 5 minutes, and the mixture was placed in an iron container and heated at 350 ° C. for 30 minutes. After heating, washing with water was performed two to three times using about 1 liter of water per 100 grams of the reaction product.

As a result, the obtained powder is dried in an oven, and the analysis results are shown in Table 2. Therefore, it can be seen that the quality of cerium oxide was improved from about 60% to more than 90% without a separate cerium refining process.

3 is an SEM photograph (x 30000 times) for this powder, all of which are 1 탆 or less.

[Table 2] Composition of cerium hydride powder

94.54% Ln ₂ O ₃ is 92.4% CeO ₂ and 2.14% other rare earth oxides.

Claims (5)

A process of leaching cerium (Ce) concentrate with nitric acid (HNO ₃ ) to obtain a leachate, a process of adding phosphate solution to the leachate and heating to obtain rare phosphate (LnPO ₄ ), and mixing rare phosphate with caustic soda Method for producing a cerium hydride powder characterized in that the step of (Fritting) and washing with water. The method of claim 1, wherein the phosphoric acid solution is selected from NaH ₂ PO ₄ , Na ₃ PO ₄ , H ₃ PO ₄ . The method for producing cerium hydride powder according to claim 1, wherein the cerium oxide powder is obtained by heating at a temperature of 200 to 850 캜 for 1 hour to 3 hours to obtain rare earth phosphate (LnPO ₄ ). The method for producing cerium hydride powder according to claim 1 or 2, wherein the amount of the phosphoric acid solution added is 1 to 3 times by weight. The method of producing cerium hydride powder according to claim 1, characterized in that fritting at a temperature of 300 to 400 ° C.