阅读说明：本技术 盐湖碳酸锂生产中排放的含硼废水生产高纯度硼砂的方法 (Method for producing high-purity borax from boron-containing wastewater discharged in production of lithium carbonate in salt lake ) 是由 朱红卫 马存彪 王守恒 张青山 张学鹏 吕春英 于 2021-01-29 设计创作，主要内容包括：本发明提供了一种盐湖碳酸锂生产中排放的含硼废水生产高纯度硼砂的方法,包括以下步骤：S1：一级纳滤系统过滤；S2：MVR蒸发浓缩；S3：二级纳滤系统过滤；S4：反渗透膜系统过滤；S5：MVR蒸发浓缩；S6：加入硫酸、碳酸钠；S7：三级纳滤系统过滤；S8：干燥和包装；步骤S1之前还包括如下步骤：将含硼卤水送入离子交换树脂中处理,得到含锂元素和硼元素的卤水；步骤S2和步骤S3之间还包括如下步骤：利用表面涂覆硼的纳滤膜对步骤S2得到的浓缩液进行分离。本发明将含硼卤水中的锂元素分离后,依次通过二级纳滤系统过滤、反渗透膜系统过滤、MVR蒸发浓缩、加入硫酸、碳酸钠和三级纳滤系统过滤,能够生产高纯度的硼砂,回收大量淡水,提高了盐湖资源的利用率。(The invention provides a method for producing high-purity borax from boron-containing wastewater discharged in the production of lithium carbonate in a salt lake, which comprises the following steps: s1: filtering by a primary nanofiltration system; s2: MVR evaporation concentration; s3: filtering by a secondary nanofiltration system; s4: filtering by a reverse osmosis membrane system; s5: MVR evaporation concentration; s6: adding sulfuric acid and sodium carbonate; s7: filtering by a three-stage nanofiltration system; s8: drying and packaging; step S1 is preceded by the following steps: sending the boron-containing brine into ion exchange resin for treatment to obtain brine containing lithium elements and boron elements; the following steps are also included between step S2 and step S3: and (4) separating the concentrated solution obtained in the step (S2) by using a nanofiltration membrane coated with boron on the surface. According to the invention, after lithium in the boron-containing brine is separated, the boron-containing brine is filtered by the secondary nanofiltration system, the reverse osmosis membrane system, the MVR evaporation and concentration, the sulfuric acid and the sodium carbonate are added, and the tertiary nanofiltration system is used for filtering, so that high-purity borax can be produced, a large amount of fresh water can be recovered, and the utilization rate of salt lake resources is improved.)

1. The method for producing high-purity borax from boron-containing wastewater discharged in the production of lithium carbonate in salt lake comprises the following steps: s1: filtering by a primary nanofiltration system; s2: MVR evaporation concentration; s3: filtering by a secondary nanofiltration system; s4: filtering by a reverse osmosis membrane system; s5: MVR evaporation concentration; s6: adding sulfuric acid and sodium carbonate; s7: filtering by a three-stage nanofiltration system; s8: drying and packaging; the method is characterized by further comprising the following steps before the step S1: sending the boron-containing brine into ion exchange resin for treatment to obtain brine containing lithium elements and boron elements;

the following steps are also included between step S2 and step S3: and (4) separating the concentrated solution obtained in the step (S2) by using a nanofiltration membrane coated with boron on the surface.

2. The method for producing high-purity borax from boron-containing wastewater discharged in the production of lithium carbonate in salt lake according to claim 1, wherein the step S1 is specifically as follows: heating the lithium-element-containing brine separated from the ion exchange resin to 50-70 ℃, and then sending the lithium-element-containing brine into a primary nanofiltration system for filtering to obtain boron-rich lithium-poor brine A and boron-poor lithium-rich brine B.

3. The method for producing high-purity borax from boron-containing wastewater discharged in the production of lithium carbonate in salt lake according to claim 2, wherein in step S1, the pressure difference between two sides of the nanofiltration membrane in the primary nanofiltration system is 50-200 bar.

4. The method for producing high-purity borax from boron-containing wastewater discharged in the production of lithium carbonate in salt lake according to claim 2, wherein the step S2 is specifically as follows: and carrying out MVR evaporation concentration on the boron-poor lithium-rich brine B to obtain a concentrated solution.

5. The method for producing high-purity borax by using boron-containing wastewater discharged in the production of salt lake lithium carbonate according to claim 4, wherein the concentrated solution obtained in the step S2 is filtered by a nanofiltration membrane with a boron-coated surface to obtain boron-rich lithium-poor brine C and boron-poor lithium-rich brine D.

6. The method for producing high-purity borax from boron-containing wastewater discharged in the production of lithium carbonate in salt lake according to claim 5, wherein the step S3 is specifically as follows: and (4) feeding the boron-rich lithium-poor brine C and the boron-rich lithium-poor brine A obtained in the step (S1) into a secondary nanofiltration system for filtration to obtain boron-rich brine D and fresh water, wherein the pressure difference between two sides of a nanofiltration membrane in the secondary nanofiltration system is 50-200 bar.

7. The method for producing high-purity borax from boron-containing wastewater discharged in the production of lithium carbonate in salt lake according to claim 6, wherein the step S4 is specifically as follows: and (4) sending the boron-rich brine D obtained in the step (S3) into a reverse osmosis membrane system, applying pressure on two sides of a reverse osmosis membrane, and obtaining the boron-rich brine E and fresh water, wherein the pressure difference is 50-100 bar.

8. The method for producing high-purity borax from boron-containing wastewater discharged in the production of lithium carbonate in salt lake according to claim 7, wherein the step S5 is specifically as follows: and (4) carrying out MVR evaporation concentration on the boron-rich brine E obtained in the step (S4) to obtain boron-rich brine F and fresh water.

9. The method for producing high-purity borax from boron-containing wastewater discharged in the production of lithium carbonate in salt lake according to claim 8, wherein the step S6 is specifically as follows: adding sulfuric acid into the boron-rich brine F, adjusting the pH of the solution to 4-6.5, heating to 80-120 ℃, adding sodium carbonate, adjusting the pH of the solution to 8-10, and reacting for 0.5-6h to obtain a borax solution.

10. The method for producing high-purity borax from boron-containing wastewater discharged from the production of salt lake lithium carbonate as claimed in claim 1, wherein in step S7, the pressure difference between two sides of the nanofiltration membrane in the three-stage nanofiltration system is 50-200 bar.

Technical Field

The invention discloses a method for producing high-purity borax from boron-containing wastewater discharged in the production of lithium carbonate in a salt lake, and belongs to the technical field of development and comprehensive utilization of salt lake brine resources.

Background

Boron is an element which is widely distributed and is one of the most important elements in the earth crust, China is one of the countries with rich boron resources in the world, B₂O₃The geological reserve is in the fifth place of the world. In recent years, with rapid development of economy, demand for boron products in various fields is increasing, and development and utilization of boron resources are greatly advanced. The product containing boron is widely applied to the fields of chemical industry, metallurgy, military industry, machinery, medicine and the like, and borax (Na)₂B₄O₇·10H₂O) is increasingly taking an important position in all industries.

The boron ion content in the Carlo salt lake brine is about 30-300ppm, and the development difficulty is large due to too low concentration, so that the development and utilization of boron resources in the Carlo salt lake region are not realized. With the gradual maturity of the process for developing and utilizing the salt lake resources, the separation technology for each ion in the old brine is gradually improved, the ions such as lithium, boron and the like can be extracted from the old brine, the separation is realized by adopting the nanofiltration membrane separation technology, and the salt lake resources are further developed and utilized.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide a method for producing high-purity borax from boron-containing wastewater discharged in the production of lithium carbonate in a salt lake, so as to solve the problems in the background technology.

In order to achieve the aim, the invention provides a method for producing high-purity borax from boron-containing wastewater of a salt lake, which comprises the following steps: s1: filtering by a primary nanofiltration system; s2: MVR evaporation concentration; s3: filtering by a secondary nanofiltration system; s4: filtering by a reverse osmosis membrane system; s5: MVR evaporation concentration; s6: adding sulfuric acid and sodium carbonate; s7: filtering by a three-stage nanofiltration system; s8: drying and packaging; step S1 is preceded by the following steps: sending the boron-containing brine into ion exchange resin for treatment to obtain brine containing lithium elements and boron elements;

the following steps are also included between step S2 and step S3: and (4) separating the concentrated solution obtained in the step (S2) by using a nanofiltration membrane coated with boron on the surface.

By adopting the scheme, the boron concentration in the boron-containing brine to be treated is lower, the effect is not good by directly utilizing the primary nanofiltration system for filtering, the boron-containing brine is treated by ion exchange resin, can separate lithium element and boron element from low-concentration boron-containing brine to obtain high-concentration boron-containing brine, then a primary nanofiltration system is used for filtration, the primary separation of boron and lithium is realized, the separation effect of boron and lithium is further improved through MVR evaporation concentration and nanofiltration membrane treatment with boron coated on the surface, partial impurity ions are removed through secondary nanofiltration system filtration, reverse osmosis membrane system filtration and MVR evaporation concentration, thereby being beneficial to the subsequent production of high-purity borax, recycling the fresh water generated in the processes of filtering of the secondary nanofiltration system, filtering of the reverse osmosis membrane system and MVR evaporation concentration, and improving the utilization rate of salt lake resources.

Preferably, step S1 specifically includes: heating the lithium-element-containing brine separated from the ion exchange resin to 50-70 ℃, and then sending the lithium-element-containing brine into a primary nanofiltration system for filtering to obtain boron-rich lithium-poor brine A and boron-poor lithium-rich brine B.

By adopting the scheme, the filtering efficiency can be improved.

Preferably, in step S1, the pressure difference between the two sides of the nanofiltration membrane in the primary nanofiltration system is 50-200 bar.

Preferably, step S2 specifically includes: and carrying out MVR evaporation concentration on the boron-poor lithium-rich brine B to obtain a concentrated solution.

Preferably, the concentrated solution obtained in step S2 is filtered by a nanofiltration membrane coated with boron on the surface to obtain boron-rich lithium-poor brine C and boron-poor lithium-rich brine D.

By adopting the scheme, after the surface of the nanofiltration membrane is coated with boron, lithium and boron can be effectively separated, the subsequent recovery of the boron is facilitated, and the lithium carbonate can be produced by adding sodium carbonate into the boron-poor and lithium-rich brine D.

Preferably, step S3 specifically includes: and (4) feeding the boron-rich lithium-poor brine C and the boron-rich lithium-poor brine A obtained in the step (S1) into a secondary nanofiltration system for filtration to obtain boron-rich brine D and fresh water, wherein the pressure difference between two sides of a nanofiltration membrane in the secondary nanofiltration system is 50-200 bar.

Preferably, step S4 specifically includes: and (4) sending the boron-rich brine D obtained in the step (S3) into a reverse osmosis membrane system, applying pressure on two sides of a reverse osmosis membrane, and obtaining the boron-rich brine E and fresh water, wherein the pressure difference is 50-100 bar.

Preferably, step S5 specifically includes: and (4) carrying out MVR evaporation concentration on the boron-rich brine E obtained in the step (S4) to obtain boron-rich brine F and fresh water.

Preferably, step S6 specifically includes: adding sulfuric acid into the boron-rich brine F, adjusting the pH of the solution to 4-6.5, heating to 80-120 ℃, adding sodium carbonate, adjusting the pH of the solution to 8-10, and reacting for 0.5-6h to obtain a borax solution.

By adopting the scheme, the boron-rich brine F is added with sulfuric acid to adjust the pH value of the solution, then sodium carbonate is added, and the purity of the borax produced after separation by the three-stage nanofiltration system is higher.

Preferably, in step S7, the pressure difference between the two sides of the nanofiltration membrane in the three-stage nanofiltration system is 50-200 bar.

Compared with the prior art, the invention has the following beneficial effects:

(1) the boron-containing brine is sent into the ion exchange resin for treatment before the filtration of the primary nanofiltration system, lithium and boron can be separated from the low-concentration boron-containing brine to obtain the high-concentration boron-containing brine, and then the primary nanofiltration system is used for filtration, so that the primary separation of the boron and the lithium is realized, and the recovery rate of the boron and the purity of the recovered borax are improved.

(2) And a nanofiltration membrane with the surface coated with boron is used between the MVR evaporation concentration step and the secondary nanofiltration system filtration step to separate concentrated solution obtained by MVR evaporation concentration, so that the separation effect of boron and lithium is further improved, and the recovery rate of boron and the purity of recovered borax are further improved.

(3) After the lithium element in the boron-containing brine is separated, the boron-containing brine is filtered by a secondary nanofiltration system, a reverse osmosis membrane system, MVR evaporation concentration, sulfuric acid, sodium carbonate and a tertiary nanofiltration system in sequence, so that high-purity borax can be produced, a large amount of fresh water can be recovered, and the utilization rate of salt lake resources is improved.

Drawings

FIG. 1 is a process flow for producing high-purity borax from boron-containing wastewater discharged in the production of lithium carbonate in a salt lake.

Detailed Description

In order to make the technical means, the creation characteristics, the achievement purposes and the effects of the invention easy to understand, the invention is further described with the specific embodiments.

Example 1

The method for producing high-purity borax from boron-containing wastewater discharged in the production of lithium carbonate in salt lake comprises the following steps:

sending the boron-containing brine into ion exchange resin for treatment to obtain brine containing lithium elements and boron elements;

s1: the first-stage nanofiltration system filters

Heating the lithium element-containing brine obtained by separating the ion exchange resin to 50 ℃, and then sending the lithium element-containing brine into a primary nanofiltration system for filtering to obtain boron-rich lithium-poor brine A and boron-poor lithium-rich brine B, wherein the pressure difference between two sides of a nanofiltration membrane in the primary nanofiltration system is 50 bar;

s2: MVR evaporative concentration

Carrying out MVR evaporation concentration on the boron-poor lithium-rich brine B to obtain a concentrated solution;

filtering the concentrated solution by a nanofiltration membrane with the surface coated with boron to obtain boron-rich lithium-poor brine C and boron-poor lithium-rich brine D;

s3: the second stage nanofiltration system filters

Feeding the boron-rich lithium-poor brine C and the boron-rich lithium-poor brine A obtained in the step S1 into a secondary nanofiltration system for filtration to obtain boron-rich brine D and fresh water, wherein the pressure difference between two sides of a nanofiltration membrane in the secondary nanofiltration system is 50 bar;

s4: reverse osmosis membrane system filtration

Feeding the boron-rich brine D obtained in the step S3 into a reverse osmosis membrane system, applying pressure on two sides of a reverse osmosis membrane, and obtaining boron-rich brine E and fresh water, wherein the pressure difference is 50 bar;

s5: MVR evaporative concentration

Carrying out MVR evaporation concentration on the boron-rich brine E obtained in the step S4 to obtain boron-rich brine F and fresh water;

s6: adding sulfuric acid and sodium carbonate

Adding sulfuric acid into the boron-rich brine F, adjusting the pH of the solution to 4, heating to 80 ℃, adding sodium carbonate, adjusting the pH of the solution to 8, and fully reacting for 0.5h to obtain a borax solution;

s7: filtering of three-stage nanofiltration system

The pressure difference between two sides of the nanofiltration membrane in the three-stage nanofiltration system is 50 bar;

s8: and (6) drying and packaging.

Example 2

The method for producing high-purity borax from boron-containing wastewater discharged in the production of lithium carbonate in salt lake comprises the following steps:

in step S1, the temperature of the brine fed into the primary nanofiltration system is 70 ℃, and the pressure difference between two sides of the nanofiltration membrane in the primary nanofiltration system is 200 bar;

in step S3, the pressure difference between the two sides of the nanofiltration membrane in the secondary nanofiltration system is 200 bar;

in step S4, the pressure difference across the reverse osmosis membrane is 100 bar;

in step S6, adding sulfuric acid into the boron-rich brine F, adjusting the pH of the solution to 6.5, heating to 120 ℃, adding sodium carbonate, adjusting the pH of the solution to 10, and reacting for 6 hours to obtain a borax solution;

in step S7, the pressure difference between the two sides of the nanofiltration membrane in the three-stage nanofiltration system is 200 bar;

except for the above experimental parameters, other experimental parameters and experimental procedures were the same as in example 1.

Example 3

The method for producing high-purity borax from boron-containing wastewater discharged in the production of lithium carbonate in salt lake comprises the following steps:

in step S1, the temperature of the brine fed into the primary nanofiltration system is 55 ℃, and the pressure difference between two sides of the nanofiltration membrane in the primary nanofiltration system is 80 bar;

in step S3, the pressure difference between the two sides of the nanofiltration membrane in the secondary nanofiltration system is 80 bar;

in step S4, the differential pressure across the reverse osmosis membrane is 60 bar;

in step S6, adding sulfuric acid into the boron-rich brine F, adjusting the pH of the solution to 4.5, heating to 90 ℃, adding sodium carbonate, adjusting the pH of the solution to 9, and reacting for 2 hours to obtain a borax solution;

in step S7, the pressure difference between the two sides of the nanofiltration membrane in the three-stage nanofiltration system is 80 bar;

except for the above experimental parameters, other experimental parameters and experimental procedures were the same as in example 1.

Example 4

The method for producing high-purity borax from boron-containing wastewater discharged in the production of lithium carbonate in salt lake comprises the following steps:

in step S1, the temperature of the brine fed into the primary nanofiltration system is 65 ℃, and the pressure difference between two sides of the nanofiltration membrane in the primary nanofiltration system is 120 bar;

in step S3, the pressure difference between the two sides of the nanofiltration membrane in the secondary nanofiltration system is 120 bar;

in step S4, the differential pressure across the reverse osmosis membrane is 80 bar;

in the step S6, adding sulfuric acid into the boron-rich brine F, adjusting the pH of the solution to 6, heating to 110 ℃, adding sodium carbonate, adjusting the pH of the solution to 9, and reacting for 4 hours to obtain a borax solution;

in step S7, the pressure difference between the two sides of the nanofiltration membrane in the three-stage nanofiltration system is 120 bar;

except for the above experimental parameters, other experimental parameters and experimental procedures were the same as in example 1.

Example 5

The method for producing high-purity borax from boron-containing wastewater discharged in the production of lithium carbonate in salt lake comprises the following steps:

in step S1, the temperature of the brine fed into the primary nanofiltration system is 70 ℃, and the pressure difference between two sides of the nanofiltration membrane in the primary nanofiltration system is 160 bar;

in step S3, the pressure difference between the two sides of the nanofiltration membrane in the secondary nanofiltration system is 160 bar;

in step S4, the differential pressure across the reverse osmosis membrane is 50 bar;

in step S6, adding sulfuric acid into the boron-rich brine F, adjusting the pH of the solution to 6.5, heating to 80 ℃, adding sodium carbonate, adjusting the pH of the solution to 9, and reacting for 4 hours to obtain a borax solution;

in step S7, the pressure difference between the two sides of the nanofiltration membrane in the three-stage nanofiltration system is 160 bar;

except for the above experimental parameters, other experimental parameters and experimental procedures were the same as in example 1.

Test example 1 Effect of different test parameters on test results

Comparative examples 1 to 5: in the comparative experiments corresponding to examples 1 to 5, the experimental steps were identical to those of the corresponding examples except that the concentrated solution obtained in step S2 was separated between step S2 and step S3 without using a nanofiltration membrane coated with boron on the surface, and the specific experimental results are detailed in table 1.

Comparative examples 6 to 10: comparative experiments corresponding to examples 1-5 were carried out in exactly the same manner as the corresponding examples except that the boron-containing brine was not treated with ion exchange resin prior to step S1, and the results are detailed in table 1.

TABLE 1 recovery of boron and composition of recovered borax

As can be seen from table 1, the recovery rate of boron element in examples 1 to 5 is greater than 80%, and the purity of the recovered borax is higher than 95%, which indicates that the present invention can effectively recover boron element in boron-containing brine, and the purity of the recovered borax is higher, compared with examples 1 to 5, the recovery rate of boron element in comparative examples 1 to 5 is between 70% and 74%, and the purity of the recovered borax is between 87% and 90%, which indicates that the concentrated solution obtained in step S2 is separated by using a nanofiltration membrane with a boron coated surface between step S2 and step S3, and the recovery rate of boron element and the purity of the recovered borax can be improved.

The recovery rate of the boron element in the comparative examples 6 to 10 is between 52 percent and 54 percent, the purity of the recovered borax is between 60 percent and 62 percent, and the recovery rate of the boron element and the purity of the recovered borax in the comparative examples 6 to 10 are far lower than those in the examples 1 to 5, which shows that the boron-containing brine is sent into ion exchange resin for treatment before the step S1, and the recovery rate of the boron element and the purity of the recovered borax can be obviously improved.

While there have been shown and described what are at present considered the fundamental principles and essential features of the invention and its advantages, it will be apparent to those skilled in the art that the invention is not limited to the details of the foregoing exemplary embodiments, but is capable of other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.