Method for preparing rare earth fluoride by taking rare earth oxide as raw material

Abstract

The invention relates to a method for preparing rare earth fluoride by taking rare earth oxide as a raw material, which comprises the steps of: (1) mixing the rare earth oxide with water, and adding concentrated hydrochloric acid into the mixture to generate rare earth chloride solution; (2) increasing the temperature of the rare earth chloride solution to be between 70 and 90 DEG C, adding a precipitator into the rare earth chloride solution, and performing thermal insulation for 10 to 30 minutes; (3) adding hydrofluoric acid into a reaction liquid, and performing a fluoridation reaction for 5 to 30 minutes at a temperature of between 70 and 90 DEG C until the reaction is complete; and (4) obtaining the rare earth fluoride by a precipitate generated by the reaction through washing, settlement, filtration and drying. The method ensures that the formed rare earth fluoride has large particles and is easy to filter, wash and precipitate after the precipitator, namely propane diacid is added, and effectively overcomes the disadvantages that the rare earth fluoride is easy for penetration filtration and is difficult to precipitate in the prior art; a fluorination endpoint determination method is adopted, which avoids the various problems caused by adding excessive hydrofluoric acid; and at the same time, mother solution containing hydrochloric acid can be circularly used, which has less discharge of waste liquid and is favorable for environmental protection.

Description

technical field [0001] The invention relates to a preparation method of rare earth fluorides, in particular to a method for preparing rare earth fluorides by using rare earth oxides as raw materials. Background technique [0002] my country is rich in rare earth resources, and various rare earth products are widely used in many industries. Among them, rare earth fluorides are important raw materials and electrolytes for the production of rare earth metals by metallothermic reduction, and are also additives for steel and nonferrous metals. They are also used in special optical fibers, lasers, etc. It is also widely used in new functional materials such as materials, and is also used as an additive for ceramics and glass. [0003] The preparation of rare earth fluorides is divided into dry process and wet process. The dry process is a gas-solid phase fluorination reaction between hydrogen fluoride gas and rare earth oxides at high temperature to directly generate solid rare ear...

AI Technical Summary

Problems solved by technology

But its biggest problem is that the rare earth fluoride particles generally generated are extremely fine, suspended in the whole solution in a colloidal state, and it is difficult to settle, which brings great trouble to the later treatment. Sometimes after a wash, the settling time reaches 24 hours, and the product is in the It is easy to penetrate the filter during filtration or centrifugation, which not only increases the difficulty of operation, prolongs the production cycle, causes waste of resources, but also has a low recovery rate of finished products, such as less than 90%.

[0006] 1. A large amount of acidic or alkaline by-products are continuously produced. If they are recycled, the input of materials and man-hours will be increased. If they are discharged randomly, they will inevitably cause environmental pollution. Product oxalic acid, hydrochloric acid, sulfuric acid and nitric acid, and produce a large amount of waste ammonia water in the preparation method that Chinese patent CN00124203.2 discloses

[0007] 2. Because the end point of the fluorination reaction cannot be controlled in time and the fluorination reaction must be complete, the input of hydrofluoric acid is generally increased during production, which will not only cause waste of materials, but also result in the fluorine-containing after the fluorination reaction If the mother liquor is discharged, it will pollute the environment. If it is recycled, the hydrofluoric acid remaining in the mother liquor has already reacted with some rare earth compounds in the next feeding, and it is likely to form a colloidal substance that is difficult to settle, as disclosed in Chinese patent CN200510088956.2 The maximum amount of hydrofluoric acid added in the method is 120% of the theoretical amount