A method for efficiently extracting bromine from bromine-containing wastewater

Abstract

This invention belongs to the field of wastewater treatment technology, specifically relating to a method for efficiently extracting bromine from bromine-containing wastewater. The method is achieved through the following steps: 1) pH adjustment; 2) acidification; 3) oxidation: The acidified mother liquor is heated, and after heating, hydrogen peroxide is added for oxidation. Distillation is performed simultaneously with the reaction, and bromine vapor is condensed and collected. The mixture is separated into layers in a collector: the lower layer contains bromine, and the upper layer contains bromine water. The bromine is discharged and collected, while the bromine water is recycled. The treatment method provided by this invention solves the problem of low bromine yield. This method can achieve a bromide ion conversion rate of over 99% and a bromine yield of over 98%. The treatment process provided by this invention is simple and offers a good approach for subsequent efficient bromine extraction.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to a method for efficiently extracting bromine from bromine-containing wastewater. Background Technology

[0002] Currently, there are two main pathways for the resource recovery and utilization of bromine in bromine-containing wastewater. One is to use physical methods, such as evaporation, crystallization, and purification, to separate and recover bromine in the form of salt. The other method is to use chemical oxidation processes to oxidize bromide ions into elemental bromine, and then separate and recover the more valuable elemental bromine.

[0003] The physical method for recovering sodium bromide is a complicated process with high overall recovery costs, making it uncompetitive.

[0004] Chemical oxidation processes mainly include chlorine oxidation, hydrogen peroxide oxidation, and electrochemical oxidation. Chlorine oxidation is a gas-liquid reaction, which presents mass transfer issues, and the storage and use of chlorine require compatible equipment and warehouses. The bromine obtained from chlorine oxidation is crude bromine, requiring further purification. Hydrogen peroxide oxidation has strict experimental conditions, requires large amounts of reagents, has high input costs, and generates a significant amount of waste salt. Electrochemical oxidation is energy-intensive. Furthermore, the bromine recovery rate is low when using hydrogen peroxide oxidation for bromine extraction.

[0005] Chinese patent applications CN116161622A and CN115974304A, among others, disclose technologies for the resource-based recovery of bromine from bromine-containing wastewater, primarily treating carnallite mother liquor and bromine-containing wastewater containing photoinitiators. The commonly used method is oxidation, primarily employing chlorine and hydrogen peroxide as oxidants. However, existing technologies using hydrogen peroxide oxidation to convert bromide ions in bromine-containing wastewater into bromine for recovery only achieve a bromine recovery rate of around 80%, a persistent challenge in the industry. Summary of the Invention

[0006] To address the technical challenges of low bromine recovery rates in existing technologies, this invention provides a method for efficiently extracting bromine from bromine-containing wastewater. This method is based on the resource utilization approach of waste treatment, optimizes the process, and overcomes the bottleneck of hydrogen peroxide oxidation technology, thereby increasing the bromine recovery rate to 98-99%.

[0007] This invention addresses the problem of bromine extraction from bromine-containing wastewater, and for the first time proposes a method for efficient and high-yield bromine extraction from bromine-containing wastewater. The specific technical solution is as follows:

[0008] This invention provides a method for efficiently extracting bromine from bromine-containing wastewater, comprising the following steps:

[0009] 1) Adjust pH: Use liquid alkali to adjust the pH of the bromine-containing wastewater;

[0010] 2) Acidification: Adjust the pH of the effluent by adding acid to acidify it, and obtain acidified mother liquor;

[0011] 3) Oxidation: The acidified mother liquor is heated, and hydrogen peroxide is added after the heating is completed to carry out oxidation. Distillation is carried out during the reaction. Bromine vapor is condensed and collected. The layers are separated in the collector: bromine in the lower layer and bromine water in the upper layer. Bromine is discharged and collected, and bromine water is refluxed and reused.

[0012] Furthermore, in step 1), the sodium bromide content in the bromine-containing wastewater is 5%-47%; and the pH is adjusted to 6-9.

[0013] Furthermore, in step 2), the acid may be sulfuric acid, hydrochloric acid, or phosphoric acid; preferably, the concentration of the sulfuric acid is 70-98%.

[0014] Furthermore, in step 2), acid is added to acidify the hydrogen ion to bromide ion molar ratio to 5-7:1.

[0015] Furthermore, in step 3), the acidified mother liquor is heated to 80℃-110℃; the mass fraction of the hydrogen peroxide is 20%-27%.

[0016] Furthermore, in step 3), the molar ratio of bromide ions to hydrogen peroxide is 1:0.75-1.

[0017] Furthermore, in step 3), the temperature conditions for the reaction are: boiling state, 80℃-110℃.

[0018] Furthermore, in step 3), the reaction time is 1-2 hours, and after the reaction is completed, the mixture is kept at a boiling state for 1-2 hours.

[0019] The processing method provided by this invention involves slowly adding acid dropwise to the pH-adjusting effluent during the acidification process, while continuously stirring.

[0020] The beneficial effects of this invention are as follows:

[0021] (1) The processing method provided by the present invention solves the problem of low bromine yield. This method can achieve a bromide ion conversion rate of over 99% and a bromine yield of over 98%.

[0022] (2) The processing method provided by the present invention is simple and provides a good idea for the subsequent efficient extraction of bromine. Detailed Implementation

[0023] The technical solution of the present invention will be further explained and described below through specific embodiments.

[0024] Example 1

[0025] 1) Take 600g of the bromine-containing wastewater, with a bromide ion content of 20.7% and a pH of 7;

[0026] 2) Add 390g of 98% sulfuric acid to the wastewater and slowly add it dropwise into the bottom liquid of the evaporation to acidify it. Adding sulfuric acid will cause the temperature to rise.

[0027] 3) After acidification, the mother liquor is heated. When the wastewater temperature reaches 110℃, 211g of hydrogen peroxide with a mass fraction of 25% is added to react. The reaction is carried out while distilling. After reacting for 1 hour, the mixture is kept at a boiling state for 1 hour.

[0028] After the reaction was terminated, bromine was released from the lower layer in the collector, bromine water was released from the upper layer, and the bromine extraction solution was contained in the reaction flask. 124g of bromine was collected, with a bromine content of 99.9%, a bromide ion conversion rate of 99.8%, and a bromine yield of 99.59%.

[0029] Example 2

[0030] 1) Take 485g of the bromine-containing wastewater, with a bromide ion content of 20.7% and a pH of 7;

[0031] 2) Add 320g of 98% sulfuric acid to the wastewater and slowly add it dropwise into the bottom liquid of the evaporation to acidify it. Adding sulfuric acid will cause the temperature to rise.

[0032] 3) After acidification, the mother liquor is heated. When the wastewater temperature reaches 110℃, 367g of hydrogen peroxide with a mass fraction of 25% is added to react. The reaction is carried out while distilling. After reacting for 1 hour, the mixture is kept at a boiling state for 1 hour.

[0033] After the reaction was terminated, bromine was released from the lower layer in the collector, bromine water was released from the upper layer, and the bromine extraction solution was contained in the reaction flask. The collected bromine weighed 97.8g, the bromine content was 99.9%, the bromide ion conversion rate was 98%, and the bromine yield was 97.8%.

[0034] Example 3

[0035] 1) Take 601g of the bromine-containing wastewater, with a bromide ion content of 20.7% and a pH of 7;

[0036] 2) Add 390g of 98% sulfuric acid to the wastewater and slowly add it dropwise into the bottom liquid of the evaporation to acidify it. Adding sulfuric acid will cause the temperature to rise.

[0037] 3) After acidification, the mother liquor is heated. When the wastewater temperature reaches 110℃, 117g of hydrogen peroxide with a mass fraction of 25% is added to react. The reaction is carried out while distilling. After reacting for 1 hour, the mixture is kept at a boiling state for 1 hour.

[0038] After the reaction was terminated, bromine was released from the lower layer in the collector, bromine water was released from the upper layer, and the bromine extraction solution was contained in the reaction flask. 118g of bromine was collected, with a bromine content of 99.9%, a bromide ion conversion rate of 99.1%, and a bromine yield of 98.4%.

[0039] Comparative Example 1

[0040] 1) Take 450.6g of the bromine-containing wastewater, with a bromide ion content of 21.7% and a pH of 7;

[0041] 2) Add 250g of 98% sulfuric acid to the bromine-containing wastewater and slowly add it dropwise into the bottom liquid of the evaporation to acidify it. Adding sulfuric acid will cause the temperature to rise.

[0042] 3) After acidification, the mother liquor is heated. When the wastewater temperature reaches 90℃, 332g of hydrogen peroxide with a mass fraction of 20% is added to react. The reaction is carried out while distilling. After reacting for 1 hour, the mixture is kept at a boiling state for 1 hour.

[0043] After the reaction was terminated, bromine was released from the lower layer in the collector, bromine water was released from the upper layer, and the bottom bromine extract was contained in the reaction flask. The collected bromine was weighed and found to be 77.7 g, with a bromine content of 99.9% and a bromine yield of 79%.

[0044] Comparing Comparative Example 1 with the Example, the amount of sulfuric acid added was changed. Insufficient sulfuric acid added resulted in a lower bromine yield.

[0045] Comparative Example 2

[0046] 1) Take 600g of the bromine-containing wastewater, with a bromide ion content of 20.7% and a pH of 7;

[0047] 2) Add 390g of 98% sulfuric acid to the wastewater and slowly add it dropwise into the bottom liquid of the evaporation to acidify it. Adding sulfuric acid will cause the temperature to rise.

[0048] 3) After acidification, hydrogen peroxide was added dropwise to the mother liquor. The mass of the hydrogen peroxide was 211g, and the mass fraction was 25%.

[0049] After hydrogen peroxide is added, the temperature is raised, and the wastewater temperature is kept at 110°C.

[0050] After the reaction was terminated, bromine was released from the lower layer in the collector, bromine water was released from the upper layer, and the bromine extraction solution was contained in the reaction flask. 100.6g of bromine was collected, with a bromine content of 99.9%, a bromide ion conversion rate of 85%, and a bromine yield of 81%.

[0051] Comparative Example 2 was used to compare with Example 1. The same amount of drug was added, but the difference was that Example 1 used a method of reacting and distilling at the same time, while Comparative Example 2 used a method of reacting first and then distilling. When comparing the two methods, the bromide ion conversion rate and bromine yield were lower in the method of reacting first and then distilling.

Claims

1. A method for efficiently extracting bromine from bromine-containing wastewater, characterized in that, Includes the following steps: 1) Adjust pH: Use liquid alkali to adjust the pH of the bromine-containing wastewater to 6-9; 2) Acidification: Adjust the pH of the effluent by adding acid to acidify it, and obtain acidified mother liquor; 3) Oxidation: The acidified mother liquor is heated. After the heating is completed, hydrogen peroxide is added to carry out oxidation. Distillation is carried out during the reaction. Bromine vapor is condensed and collected. The layers are separated in the collector: bromine in the lower layer and bromine water in the upper layer. Bromine is discharged and collected, and bromine water is refluxed and reused. In step 2), acid is added to acidify the hydrogen ion to bromide ion molar ratio to 5-7:1; In step 3), the temperature conditions for the reaction are: boiling state, 80℃-110℃; In step 3), the reaction time is 1-2 hours, and after the reaction is completed, the mixture is kept at a boiling state for 1-2 hours.

2. The method according to claim 1, characterized in that, The sodium bromide content in the bromine-containing wastewater is 5%-47%.

3. The method according to claim 1, characterized in that, In step 2), the acid is selected from sulfuric acid, hydrochloric acid, or phosphoric acid; the mass concentration of the sulfuric acid is 70-98%.

4. The method according to claim 1, characterized in that, In step 3), the acidified mother liquor is heated to 80℃-110℃; the mass fraction of the hydrogen peroxide is 20%-27%.

5. The method according to claim 1 or 4, characterized in that, In step 3), the molar ratio of bromide ions to hydrogen peroxide is 1:0.75-1.