JPS5867836A - Decomposition of bastnaesite ore - Google Patents

Abstract

PURPOSE:To recover F and rare earth elements, by a method wherein bastnaesite ore is roasted in the presence of moisture to gasify CO2 and F as hydride from fluorinated carbonate and, while the formed gaseous products are scrubbed with an aqueous alkali medium, a caustic alkali liquid is added to the roasted ore to extract the same with a mineral acid under heating. CONSTITUTION:When bastnaesite ore is heated to 400 deg.C or more in the presence of moisture, CO2 and F are gasified as a hydride from fluorinated carbonate by hydrothermal reaction. When said gas components are surubbed with an aqueous KOH or NaOH solution, F is fixed as CaF2 and recovered as a water insoluble precipitate. On the other hand, a conc. caustic alkali aqueous solution is added to the roasted ore to be heated to 120 deg.C or more and said roasted ore is subsequently extracted with warm water to elute phosphorus. In addition, when the residue is extracted with a mineral acid, especially, conc. hydrochloric acid, 90% or more of rare earth elements are recovered as rare earth metal chlorides solution.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a non-polluting process for extracting rare earth elements from bastnaesite ore.

Bastnaesite is a fluorinated carbonate (RF COs), which in concentrate contains up to 70% of rare earths, and further contains about 100% to 100% of fluorine.

There is also bastnasite ore that is produced containing monazite, and monazite is generally (Ce).

La ty t Th) f'o, it is a phosphate mineral and therefore contains phosphorus.

Therefore, bastnaesite ore contains fluorine, phosphorus, etc., and these must be treated completely and without pollution.

Conventionally, bastnaesite ore is treated by roasting with sulfuric acid, i.e., by sulfuric roasting, to treat it with white smoke at around 200°C to remove fluorine in the form of hydrogen fluoride gas. Gas (SOS) is generated, and a new incidental treatment process is required for gas treatment, which is not only economically disadvantageous, but also poses pollution problems such as the difficulty of complete treatment, making it difficult to adopt it on an industrial scale. The current situation is that it is difficult.

On the other hand, there is a method using an alkaline aqueous solution, but in pastonesite ore containing monazite in addition to fluorine, fluorine and phosphorus are present in the alkaline aqueous solution, making subsequent liquid treatment difficult.

Alternatively, a method of directly using hydrochloric acid or nitric acid may be considered, but this is difficult to adopt due to problems with the materials used for chlorine gas or fluorine gas, gas processing, and cost.

The present inventors gasified carbon dioxide and fluorine by roasting bastnaesite ore and monazite-containing bastnasite ore in the presence of moisture, completely recovered fluorine by scrubbing with an aqueous alkaline medium, On the other hand, roasted products are decomposed with a caustic alkaline aqueous solution to fix the phosphorus in the alkaline aqueous solution, and the resulting hydroxylated tongue is extracted by adding mineral acid to solve the pollution problem, which has been difficult until now. We have discovered a new method for decomposing bastnaesite ore, which was thought to be a mineral.

That is, in the present invention, bastnaesite ore (including cases containing monazite) is roasted in the presence of moisture, but the carbonic acid in bastnaesite releases carbon dioxide at temperatures above 00°C. It decomposes into RFO with the following composition.

RFCO, −+RFO+COs −−−−−−−−−
(1) An example of thermal decomposition of bastnaesite was analyzed using differential thermal analysis (DTA).
) curve and thermogravimetric change (TGA) curve are shown in FIG.

If you gradually increase the temperature shown on the lower axis from Figure 1, it will be about ttoo.
℃ (at point m> the TGA curve shows a rapid weight loss,
The DTA curve also shows endotherm.

The weight loss value in this case is about 7.2%, but if the sample consists entirely of bastnaesite, the RFCO when using the average atomic weight of the rare earth element/≠0.

The calculated weight loss rate when changing from to RFO is 20°5%.
It is. At ≠oo°C, the composition becomes RFO, and the F volatilization rate at this time is 10 to /j%. Therefore, to decompose bastnaesite by roasting, the minimum is t.
A temperature of ioo°C or higher is required.

Next, when roasted in the presence of moisture, fluorine reacts with water as follows, gasifies and decomposes as hydrogen fluoride gas.

RFO+H20→几、03+、2HF ・ ・ ・
・ ・ ・ ・(2) This moisture can be obtained by pre-impregnating bastnaesite ore with a moisture content of 30% or more, or preferably by directly introducing steam with an absolute humidity of 109/- or more into a roasting furnace.
This is achieved by continuously blowing at a flow rate of 2 to 3 t/min or more.

Figure 2 shows the fluorine removal rate as a result of changes in temperature and absolute humidity when steam is directly blown into the roasting furnace.

As shown in FIG. 2, as the temperature gradually rises above ttoo DEG C. for decarbonation and as the absolute humidity becomes 109/- or more, the defluorination rate approaches 100%. Preferably, by continuously blowing 2 to 3 tons/ml of water into water at a temperature of 100°C and an absolute humidity of 301/n/m and roasting for 3 hours, a fluorination removal rate of more than 1% is shown. It is not limited to the value. In addition, excessive moisture is undesirable as it causes energy loss, and if the temperature exceeds 7000°C, bastnaesite tends to solidify, which affects post-processing.
It is necessary to keep the temperature within ±IOθ℃.

Next, as shown in equation (2) of L, the hydrothermal decomposition is performed to produce oxides that do not contain fluorocarbonic acid and hydrogen fluoride gas, but the obtained carbon dioxide and hydrogen fluoride gas are Scrub with something.

As the alkali metal hydroxide, an aqueous solution of sodium hydroxide or potassium hydroxide, a suspension of calcium hydroxide, or a mixture thereof is used, and by scrubbing with these, it can be fixed as Car, and a water-insoluble precipitate can be formed. It can be recovered as

Decarboxylation of bastnaesite in this way.

Almost 100% defluorination is possible, resulting in an oxide on the tongue. Furthermore, if bastnaesite contains monazite, phosphorus oxides will also be present, requiring extensive dephosphorization. The present invention further performs this dephosphorization,
The present invention provides a method for decomposing bastnaesite that can be recovered on the tongue with high yield.

That is, a concentrated aqueous caustic alkali solution is added to the roasted rare earth oxide obtained, and the mixture is heated to 720°C or higher to cause a reaction. By hot water extraction, phosphorus is fixed in the solution as phosphorus soda and recovered. The hydroxylated tongue is recovered by leaching at 70°C or higher using mineral acid.

The caustic alkali aqueous solution to be reacted with the roasted rare earth oxide is preferably a caustic soda solution with a concentration of jOW/V% or higher, and the temperature is 1.
A higher temperature of 20°C or higher is preferable.

Next, extract the tongue using dry water, separate the generated hydroxylated tongue and fix phosphorus as a solution of sodium phosphate. By humidifying and leaching it, more than 0% of the tongue can be recovered as a chloride offshore solution.

There is also a method of adding dilute acid to dissolve everything other than cerium on the tongue, but the leaching rate is poor and complete separation is difficult, and it is necessary to further separate cerium and phosphorus, so this is a good method. It can not be said.

The method of the present invention has the advantage that by roasting bastnaesite, the elution of iron contained in bastnaesite can be prevented as much as possible, and furthermore, iron can be removed by adjusting the pH of the offshore chloride solution. Become.

The first use on the tongue made from Bast and Nesite is as an abrasive, but since abrasives are extremely averse to fluorine, phosphorus, iron, etc. in oxides on the tongue, they must be completely removed during the process. Therefore, it is advantageous to have as high a purity as possible in the solvent extraction process for separating single substances on the tongue. However, as described above, the present invention sequentially separates fluorine, phosphorus, iron, etc. from bastnaesite, and improves the purity. It is an economical and non-polluting decomposition method to obtain a high chloride offshore solution.

The present invention will be further explained by examples.

Example Bastnasite/θOy- having the composition shown in Table 1 was placed in a combustion boat and roasted at 100°C for 2 hours. At that time, water fish and air with an absolute humidity of 30 f/n/ are directly blown into the furnace at a flow rate of 2 to Jt/min, and the gas is delivered to the outlet of the furnace in the form of KOH and C.
It was absorbed into a washing bottle containing a mixture of a(OH)2. The composition of the obtained roasted oxide is shown in Table 2.

Next, twice the amount of concentrated caustic soda solution was added to 5 y of this roasted oxide and reacted at 30±10° C. for 7 hours, followed by extraction with warm water and filtration.

Furthermore, after adding concentrated hydrochloric acid to the precipitate and leaching it at lr0℃ for 7 hours,
Table 3 shows the analysis values of the P solution when over-cleaning was carried out.

Table ′ (Unit: %)
2 Table (Unit: %) 3rd
Table (unit?/1)

[Brief explanation of the drawings] Figure 1 is a graph of the relationship between the differential thermal curve and thermogravimetric change curve in the thermal decomposition of bastnaesite, and Figure 2 is a graph of the relationship between the differential thermal curve and thermogravimetric change curve in the thermal decomposition of bastnaesite. FIG. 3 is a graph showing the relationship between temperature, moisture content, and baking time, and is a process diagram of the present invention. Patent Applicant Dowa Mining Co., Ltd. Figure 1 Temperature ('C) Figure 2 Heating Temperature (0C) Figure 8 □Anoni]] Kakudo Ralo □Kenji]] Liquid 178- Recari; Acid

Claims (2)

[Claims] (1) Bastnasite ore is roasted in the presence of moisture to gasify carbon dioxide and fluorine from fluorinated carbonates as hydrides, and the gaseous body is scrubbed with an aqueous alkaline medium. How to decompose site ore. (2) Bastnaesite ore is roasted in the presence of moisture to gasify carbon dioxide and fluorine from the fluorinated carbonates as hydrides, and the gaseous body is scrubbed with an aqueous alkaline medium, and the above-mentioned mortarized material is treated with caustic A method for decomposing bastnaesite ore, which is characterized by adding mineral acid to the hydroxylated tongue produced after adding an alkaline solution and heating it to extract the tongue.