For the preparation of nano bismuth oxide, the main methods include plasma method, melt spray oxidation method, chemical vapor condensation method, sol-gel method, chemical precipitation method, etc. Each method has its own characteristics. The plasma method has the advantage of short process, but requires special equipment, one-time investment, high cost; Melt spray oxidation process is short, but there are some problems such as incomplete bismuth oxidation, short nozzle life, dangerous operating environment, etc. Chemical vapor condensation method has high requirements on equipment material and limited industrial development. Superfine bismuth oxide powder prepared by sol-gel method has the advantages of good chemical uniformity, high purity, fine particles, and can contain insoluble components or unprecipitated components. However, it has some disadvantages such as poor sinterability and large shrinkage during drying. Chemical precipitation method using chemical methods, the preparation of ultra-fine bismuth oxide powder with a relatively simple device, uniform particle size distribution, powder active good superiority, but the chemical precipitation preparation bismuth oxide powder are metal bismuth ingot as raw material, its use of nitric acid solution to produce nitric oxide gas causes serious pollution to the environment, the cost is higher also. The purpose of the invention is to overcome the technical difficulties in the routine method, and provide a method for the production of nano bismuth oxide with bismuth oxychloride concentrate as raw material, simple production process, low cost, environmental protection standards, high product activity and average particle size is less than 0.010μm.
The specific process is to use hydrochloric acid to leach bismuth oxychloride concentrate and remove impurity. Impurities were removed by hydrolysis of immersion solution. The bismuth oxychloride was converted into Bi2O3 by sodium hydroxide solution for impurity removal. Use nitric acid to dissolve Bi2O3 to remove impurity; The bismuth nitrate solution was precipitated by sodium hydroxide solution. The produced bismuth oxide is washed with deionizing active water, filtered and dried in a vacuum drying oven to obtain nano bismuth oxide products.
The main chemical reactions that occur are (1)(2)(3)(4)
(5) The preparation of nano-sized bismuth oxide by this method has the characteristics of short process, low cost and environmental friendliness; Because the raw material is bismuth concentrate and the reagent is cheap hydrochloric acid, the production cost is 20-30% lower than that of conventional chemical precipitation method. Environmental protection standards, no conventional chemical precipitation produced by the nitrogen oxide gas pollution to the environment; With the addition of a small amount of dispersant, bismuth nitrate and sodium hydroxide were used to produce nano-bismuth oxide products in one step, and the preparation, forging, firing and ball milling processes of precursor system were omitted. 1. 100g BiOCL concentrate (containing 60% BiOCL) was leached and filtered at the temperature of 80℃, time of 1h, liquid-solid ratio of 2∶1, acid consumption of 1.75 times the theoretical amount. BiOCL was hydrolyzed at the volume ratio of water to BICL3 solution of about 10∶1, temperature of 95℃. Bi2O3 was obtained at the temperature of 95℃, liquid-solid ratio of 5∶1, time of 2 hours, and NaOH solution concentration of 5%. The obtained Bi2O3 was dissolved in nitric acid at about 40℃, and the bismuth concentration was controlled at 300g/ L, and the free nitric acid concentration was 80g/ L. At the same time, DBS disdistant was added. The concentration was maintained at 0.1M, and the total volume of the solution was 200 mL. Dissolve 110g 95% NaOH in 100mL deionized water, and set aside.
Under the stirring condition of 90℃, NaOH solution was quickly added to Bi(NO3)3 solution. After constant stirring for 2h, it was filtered and washed with deionized water until the NO3- root was qualified. After that, the nano bismuth oxide product was dried in a drying oven at about 60℃.
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