1. Add a slight excess of bromine directly to a saturated solution of saturated sodium hydroxide to form a mixture of bromide and bromate:
The mixture at this time is evaporated to dryness, and the obtained solid residue is heated and mixed with carbon powder to reduce the bromate to bromide:
Finally, it is dissolved in water, filtered and crystallized, and dried at 110 to 130 ° C.
This method is a general method for the preparation of bromide by bromine, which is generally employed in the industry.
2. Neutralization method: using sodium bicarbonate as raw material: sodium hydrogencarbonate is dissolved in water, and then neutralized with 35%-40% hydrobromic acid to obtain a sodium bromide solution, concentrated and cooled to precipitate bromine dihydrate. Sodium. Filtration, dissolving the dihydrate with a small amount of water, and adding bromine water to the color of bromine just emerging. Heat, decolorize with aqueous hydrogen sulfide solution, and boil. The anhydrate crystals were precipitated at a high temperature, dried, transferred to a desiccator, and maintained at 110 for 1 hour. It is then cooled in a desiccator containing a calcium bromide desiccant to give anhydrous sodium bromide (reagent grade).
Reaction principle: HBr+NaHCO3→NaBr+CO2↑+H2O
40% liquid alkali is used as raw material: hydrobromic acid is placed in the reaction pot, and under constant stirring, 40% liquid alkali solution is slowly added, and neutralized to pH 7.5-8.0 to form a sodium bromide solution. The sodium bromide solution was centrifuged and filtered into a dilute sodium bromide solution storage tank. Then, it is concentrated in an evaporation tank, and the intermediate is fed 1-2 times. When the specific gravity is about 1.55°Be, it is centrifugally filtered and filtered into a concentrated sodium bromide storage tank. Then, it is pressed into a crystallizing tank, the crystals are cooled under stirring, and the crystals are centrifuged to obtain a finished product. The mother liquor is returned to the dilute sodium bromide solution storage tank.
Reaction principle: HBr+NaOH→NaBr+H2O
3. Urea reduction method: In the alkali tank, the soda ash is dissolved in hot water at a temperature of 50-60 ° C, and then urea is added to dissolve the 21 ° Be solution. Then transfer to the reduction reactor, slowly introduce bromine, control the reaction temperature of 75-85 ° C, until the pH reaches 6-7, the reaction end point is reached, stop bromine and stir to obtain sodium bromide solution.
The pH was adjusted to 2 with hydrobromic acid, and the pH was adjusted to 6-7 with urea and sodium hydroxide to remove the bromate. The solution was heated to boiling and a saturated solution of cesium bromide was added at pH 6-7 to remove the sulfate. If the cerium salt is excessive, it can be removed by adding dilute sulfuric acid. Add the activated carbon to the reaction material after the decontamination, and let it stand for 4-6 hours. After the solution is clarified, suction filtration, atmospheric pressure evaporation, intermediate feeding several times, and stopping the feeding 2 hours before the crystallization. Adjust the pH to 6-7 before 1 hour of crystallization. Separate and dry in a drum dryer to obtain sodium bromide.
Reaction principle: 3Br2+3Na2CO3+NH2CONH2=6NaBr+4CO2↑+N2↑+2H2O
Iron and bromine are directly reacted to form ferrous bromide and then azeotroped with sodium carbonate. The by-product is basic ferrous carbonate, which becomes a colloidal compound of ferrous and high iron after boiling, and the filtration is extremely slow. In order to avoid this disadvantage, it is preferable to add bromine twice, and finally the iron oxide is mainly obtained, so filtration and washing are easy, and the reaction is as follows:
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