The methods for synthesizing sodium iodide include iron filing reduction method, iron filing method, sodium sulfide method, neutralization method, and sodium hydrogencarbonate method [1-3]. These methods introduce new impurities (such as iron, sulfur, etc.) in the synthesis process, which is difficult to purify, and further purification will affect the yield. The sodium carbonate method [4] is also a relatively good synthesis method, but sodium carbonate is difficult to react with iodine at normal temperature and pressure. If sodium hydroxide is used instead of sodium carbonate, since sodium hydroxide has a strong basicity, it can rapidly react with iodine at normal temperature and pressure, thereby shortening the time required for the synthesis, and the yield is also high. Although sodium hydroxide will bring in certain impurities, the purity of the chemical reagent sodium iodide is not as high as that of high-purity sodium iodide. The synthesized sodium iodide can be completely purified by the chemical reagent sodium iodide. The technical indicators, so the use of sodium hydroxide and iodine to synthesize sodium iodide is a good way to synthesize chemical reagent sodium iodide.
Sodium iodide synthesis process
1. Feeding synthetic sodium iodide solution
Add 30 kg of pure water to the reactor, slowly add about 8.2 kg of NaOH (industrial grade, determined to be about 96.5%) with stirring, stir to completely dissolve NaOH, and pass cooling water to the interlayer of the reactor. Then slowly add 25 kg of chemically pure elemental iodine to carry out the reaction. The synthesis reaction releases a large amount of heat. The reaction process keeps the reaction temperature at 60-70 °C. This temperature can ensure the rapid progress of the reaction and minimize the iodine content. Sublimation, after adding iodine, the solution contains NaI, NaIO and NaIO3, and the solution is added with hydrazine hydrate (slightly excessive) to carry out the reaction, and the solution is slowly converted into a colorless liquid, at which time the pH of the solution is measured ≈6 This completes the synthesis of the sodium iodide solution.
2. Purification of sodium iodide solution
If the above-mentioned synthesized sodium iodide solution is directly subjected to a dehydration operation, the obtained sodium iodide crystal is somewhat yellowish, and the crystal is dissolved in water and has a lot of insoluble matter, so that a purification operation is required.
The industrial grade sodium hydroxide and chemical pure grade iodine raw materials used in the experiment have not many impurities such as sulfates and chlorides. The synthesized sodium iodide solution does not need to be purified by chemical methods, only the activated carbon needs to be added. Decolorize and absorb some mechanical impurities. The specific operation is: add 1 kg of activated carbon to the synthesized sodium iodide solution, keep the pH value of the solution ≈6, heat and boil for half an hour, then let it stand for 4 h and then filter. It can be seen that the purification process of the sodium iodide solution synthesized by the method is very simple.
3, dehydration
The purified sodium iodide solution can be immediately heated and concentrated, and then roasted to anhydrous to obtain a finished product of sodium iodide.
Yield
The yield of sodium iodide produced by this method is very high. The experiment puts 25 kg of iodine into the reaction, and the finished product of sodium iodide is 29.3 kg, and the yield is 117.2%, which is very close to the theoretical value of 118.1%.
product quality
The technical indicators required for the synthesis of sodium iodide synthesized in this experiment are the factory standards set by the factory. There are two grades, namely analytical pure and chemically pure, and the analytically pure indicators are higher than chemically pure. The sodium iodide synthesized according to the above method has very good quality and can basically meet the analytical pure requirements of various indexes.
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