Method for recovering high-purity sodium bromide from bromine-containing crude salt

A method for recovering high-purity sodium bromide from bromine-containing crude salt, comprising steps are as follows:

• (1) immersion and filtration:
• immersing bromine-containing crude salt in tap water and filtering the tap water with the immersed bromine-containing crude salt to obtain an immersion solution and an immersion residue, wherein a ratio of volume of tap water to mass of the bromine-containing crude salt is 3:1-5:1 L/kg, the bromine-containing crude salt is immersed for 10-20 minutes under 25-35° C. to obtain the immersion solution and the immersion residue, in which the mass ratio of bromine-containing crude salt is 5-25%;
• (2) acidification and oxidation:
• performing an acidification and oxidation reaction by acidifying the immersion solution obtained in step (1) with 36% concentrated hydrochloric acid, and then adding sodium chlorate to the immersion solution while stirring the immersion solution, wherein a pH of the immersion solution is maintained at 0-1 with the concentrated hydrochloric acid to obtain an acidification oxidation solution and acidification oxidation gas, an amount of the added concentrated hydrochloric acid is 0.4-0.8 L/L of the immersion solution, an amount of the added sodium chlorate is 10-20 g/L of the immersion solution, a time of the acidification and oxidation reaction is 30-60 min, and a temperature of the acidification and oxidation is 25-35° C.;
• (3) multi-stage extraction:
• subjecting the acidification oxidation solution obtained in step (2) to a multi-stage extraction with carbon tetrachloride, wherein a volume ratio of the carbon tetrachloride to the acidification oxidation solution is 1.5:1-2.5:1, and a number of extraction stages in the multi-stage extraction is 2-5 with 2-8 min extraction time and a temperature of the multi-stage extraction is 25-35° C., wherein an extract solution and a raffinate obtained as a result of the multi-stage extraction, and wherein the raffinate is evaporated and crystallized to obtain crude sodium bromide for centralized treatment;
• (4) cooperative back extraction:
• performing a cooperative back extraction reaction by adding a back extractor to the extract solution obtained in step (3) while stirring the extract solution, and when a pH of the extract solution reaches 6-7, stopping adding the back extractor, and continuing the cooperative back extraction reaction for 5-10 minutes at 25-35° C. to obtain an organic phase and a back extraction solution;
• and
• (5) evaporative crystallization:
• subjecting the back extraction solution obtained in step (4) to evaporative crystallization to obtain sodium bromide, wherein a temperature of the evaporative crystallization is 110° C.-140° C.