Method for purifying brackish water by modified aerogel

Abstract

This invention relates to the field of brackish water treatment technology, and provides a method for purifying brackish water using modified aerogels. The method includes: adding acid-modified aerogel to brackish water and stirring to form a first solid-liquid mixture; separating the first solid-liquid mixture to obtain pre-purified brackish water; adding alkali-modified aerogel to the pre-purified brackish water and stirring to form a second solid-liquid mixture; and separating the second solid-liquid mixture to complete the brine purification. This invention utilizes the high specific surface area and high porosity of modified aerogels to adsorb ions in brackish water. First, the acid-modified aerogel is ground into powder; then, the acid-modified aerogel powder is added to the brackish water to adsorb heavy metal ions such as lead, mercury, arsenic, and cadmium, as well as organic compounds such as benzene, phenol, ether, and naphthalene; after solid-liquid separation, alkali-modified aerogel is added to the brackish water to exchange ions such as sodium, potassium, calcium, magnesium, and barium; achieving graded removal of ions from the brackish water, and separating the aerogel by filtration.

Description

Technical Field

[0001] This invention relates to the field of brackish water treatment technology, and more particularly to a method for purifying brackish water using modified aerogels. Background Technology

[0002] Brackish water is mainly distributed in northern and eastern coastal areas. More than 38 million people in rural areas drink brackish water. The main characteristic of brackish water is its bitter taste, making it difficult to drink directly. Long-term consumption can lead to gastrointestinal disorders and weakened immunity. Existing methods for treating brackish water include distillation and electrodialysis. Electrodialysis uses an ion-exchange membrane under an electric field to separate anions and cations in the brine, thereby reducing the salt concentration in the desalination chamber to obtain fresh water. Electrodialysis is a membrane separation technology that requires strict water quality control and pretreatment of the raw water. Distillation is suitable for laboratory and small-scale brackish water treatment but cannot be used for large-scale brackish water desalination production. Summary of the Invention

[0003] The purpose of this invention is to solve at least one technical problem in the background art and to provide a method for purifying brackish water by modifying aerogel.

[0004] To achieve the above objectives, the present invention provides a method for purifying brackish water using modified aerogel, comprising:

[0005] Acid-modified aerogel was added to brackish water and stirred to form a first solid-liquid mixture;

[0006] The first solid-liquid mixture was subjected to solid-liquid separation to obtain pre-purified brackish water;

[0007] Add alkali-modified aerogel to the initially purified brackish water and stir to form a second solid-liquid mixture;

[0008] The second solid-liquid mixture is subjected to solid-liquid separation to complete the purification of brackish water.

[0009] According to one aspect of the present invention, the acid-modified aerogel is a plurality of particulate acid-modified aerogels with a particle size of less than 100 mesh.

[0010] According to one aspect of the invention, the volume ratio of the brackish water to the acid-modified aerogel is 1:150 to 1:250.

[0011] According to one aspect of the present invention, acid-modified aerogel is added to brackish water and stirred for 10-60 minutes at a stirring speed of 180-600 rpm.

[0012] According to one aspect of the present invention, acid-modified aerogel is added to brackish water and stirred for 30 minutes at a stirring speed of 300 rpm.

[0013] According to one aspect of the present invention, the alkali-modified aerogel is a plurality of particulate alkali-modified aerogels with a particle size of less than 100 mesh.

[0014] According to one aspect of the invention, the ratio of the brackish water to the alkali-modified aerogel is 1:150 to 1:250.

[0015] According to one aspect of the present invention, alkali-modified aerogel is added to brackish water and stirred for 10-60 minutes at a stirring speed of 180-600 rpm.

[0016] According to one aspect of the present invention, alkali-modified aerogel is added to brackish water and stirred for 30 minutes at a stirring speed of 300 rpm.

[0017] According to the present invention, the present invention utilizes the high specific surface area and high porosity of modified aerogel to adsorb ions in brackish water. First, acid-modified aerogel is ground into powder; then, the acid-modified aerogel powder is added to brackish water to adsorb heavy metal ions such as lead, mercury, arsenic, and cadmium, as well as organic compounds such as benzene, phenol, ether, and naphthalene; after solid-liquid separation, alkali-modified aerogel is added to the brackish water to exchange ions such as sodium, potassium, calcium, magnesium, and barium; thus, the ions in the brackish water are removed in stages, and the aerogel is separated by filtration.

[0018] According to the present invention, a method for adsorbing ions such as calcium, magnesium, barium, lead, mercury, arsenic, sulfate, and chloride, as well as organic matter in brackish water, using different modified aerogels is provided. For cations such as calcium, magnesium, and barium, alkali-modified silica aerogels with ion exchange functions can be selected; for anions such as lead, mercury, arsenic, sulfate, and chloride, acid-modified silica aerogels with anionic functional groups possessing adsorption capabilities can be selected. This method not only solves the problem of high-value utilization of heavy metal solidification but also achieves efficient utilization of brackish water resources through purification. Attached Figure Description

[0019] Figure 1 The flowchart schematically illustrates a method for purifying brackish water using modified aerogel according to one embodiment of the present invention. Detailed Implementation

[0020] The invention will now be discussed with reference to exemplary embodiments. It should be understood that the described embodiments are merely intended to enable those skilled in the art to better understand and thus implement the invention, and are not intended to imply any limitation on the scope of the invention.

[0021] As used herein, the term "comprising" and its variations are to be interpreted as open-ended terms meaning "including but not limited to". The term "based on" is to be interpreted as "at least partially based on". The terms "one embodiment" and "an embodiment" are to be interpreted as "at least one embodiment".

[0022] Figure 1 The flowchart schematically illustrates a method for purifying brackish water using modified aerogels according to one embodiment of the present invention. Figure 1 As shown, in this embodiment, the method for purifying brackish water using modified aerogel includes:

[0023] Acid-modified aerogel was added to brackish water and stirred to form a first solid-liquid mixture;

[0024] The first solid-liquid mixture was subjected to solid-liquid separation to obtain pre-purified brackish water;

[0025] Add alkali-modified aerogel to the initially purified brackish water and stir to form a second solid-liquid mixture;

[0026] The second solid-liquid mixture is subjected to solid-liquid separation to complete the purification of brackish water.

[0027] Among them, acid-modified aerogel is prepared by a one-step method, namely by adding hydrochloric acid to sodium silicate to form a sol-gel, and the resulting aerogel is acidic, i.e., acid-modified aerogel.

[0028] Alkali-modified aerogels are prepared by adding ammonia to silica gel. The aerogels are prepared under alkaline conditions with a pH > 8 and are modified with amino groups.

[0029] The difference between acid-modified aerogels and alkali-modified aerogels lies in the degree of hydrolysis and the more dispersed network of acid-modified aerogels, while the degree of condensation and the more polymerized network of alkali-modified aerogels.

[0030] According to one embodiment of the present invention, the acid-modified aerogel is a plurality of particulate acid-modified aerogels with a particle size of less than 100 mesh.

[0031] Furthermore, according to one embodiment of the present invention, the ratio of brackish water to acid-modified aerogel is 1:150-1:250.

[0032] Furthermore, according to one embodiment of the present invention, acid-modified aerogel is added to brackish water and stirred for 10-60 minutes at a stirring speed of 180-600 rpm.

[0033] Preferably, acid-modified aerogel is added to brackish water and stirred for 30 minutes at a stirring speed of 300 rpm.

[0034] Furthermore, according to one embodiment of the present invention, the alkali-modified aerogel is a plurality of particulate alkali-modified aerogels with a particle size of less than 100 mesh.

[0035] Furthermore, according to one embodiment of the present invention, the ratio of brackish water to alkali-modified aerogel is 1:150-1:250.

[0036] Furthermore, according to one embodiment of the present invention, after adding alkali-modified aerogel to brackish water, the mixture is stirred for 10-60 minutes at a stirring speed of 180-600 rpm.

[0037] Preferably, the alkaline-modified aerogel is added to the brackish water and stirred for 30 minutes at a stirring speed of 300 rpm.

[0038] According to the above-described scheme of the present invention, aerogel is a lightweight solid material with a nanoscale porous structure. It has excellent properties such as low density, high porosity, large specific surface area, and ultra-low thermal conductivity. The adsorption performance of aerogel is mainly achieved through physical adsorption and ion exchange, which can effectively desalinate brackish water.

[0039] This invention utilizes the high specific surface area and high porosity of further modified aerogels to adsorb ions from brackish water. First, acid-modified aerogels are ground into powder. Then, the acid-modified aerogel powder is added to brackish water to adsorb heavy metal ions such as lead, mercury, arsenic, and cadmium, as well as organic compounds such as benzene, phenol, ether, and naphthalene. After solid-liquid separation, alkali-modified aerogels are added to the brackish water to exchange ions such as sodium, potassium, calcium, magnesium, and barium. This achieves the staged removal of ions from the brackish water, followed by filtration to separate the aerogels.

[0040] According to the present invention, acid reacts with sodium silicate to form orthosilicic acid, which then undergoes condensation polymerization to form a gel. Hydroxyl groups are present on the silicate. The number of hydroxyl groups is reduced by condensation polymerization, but hydroxyl groups are still present at the edges of the three-dimensional structure.

[0041] Lead, mercury, arsenic, etc., are complexed through amino groups on the aerogel to form metal complexes, while anions are formed through physical adsorption.

[0042] The present invention will be described below with reference to specific embodiments and comparative examples:

[0043] Example 1

[0044] The method for purifying brackish water using modified aerogels includes the following steps:

[0045] S1: Grind the acid-modified aerogel to 100 mesh using a planetary ball mill;

[0046] S2: A measured amount of acid-modified aerogel ground in step S1 is fed into brackish water (with a dissolved solids content of 4000 mg / L) and stirred for 30 minutes at a stirring speed of 300 rpm.

[0047] S3: Place the solid-liquid mixture from step S2 into a ceramic disc centrifuge for filtration to obtain a solution and a solid phase;

[0048] S4: Grind the alkali-modified aerogel to 100 mesh using a grinding mill;

[0049] S5: A measured amount of alkali-modified aerogel, after being ground in step S4, is introduced into the brackish water after step S3 and stirred for 30 minutes at a stirring speed of 300 rpm.

[0050] S6: The solid-liquid mixture from step S5 is placed into a candle filter for filtration to obtain the solution and solid phase, thus completing the purification of brackish water.

[0051] Comparative Example 1

[0052] This comparative example includes the following steps:

[0053] S1: Grind the acid-modified aerogel to 100 mesh using a planetary ball mill;

[0054] S2: A measured amount of acid-modified aerogel ground in step S1 is fed into brackish water and stirred for 10 minutes at a stirring speed of 300 rpm.

[0055] S3: Place the solid-liquid mixture from step S2 into a ceramic disc centrifuge for filtration to obtain a solution and a solid phase;

[0056] S4: Grind the alkali-modified aerogel to 100 mesh using a grinding mill;

[0057] S5: A measured amount of alkali-modified aerogel, after being ground in step S4, is introduced into the brackish water after step S3 and stirred for 10 minutes at a stirring speed of 300 rpm.

[0058] S6: The solid-liquid mixture from step S5 is placed into a candle filter for filtration to obtain the solution and solid phase, thus completing the purification of brackish water.

[0059] Comparative Example 2

[0060] This comparative example includes the following steps:

[0061] S1: Grind the acid-modified aerogel to 100 mesh using a planetary ball mill;

[0062] S2: A measured amount of acid-modified aerogel ground in step S1 is fed into brackish water and stirred for 60 minutes at a stirring speed of 300 rpm.

[0063] S3: Place the solid-liquid mixture from step S2 into a ceramic disc centrifuge for filtration to obtain a solution and a solid phase;

[0064] S4: Grind the alkali-modified aerogel to 100 mesh using a grinding mill;

[0065] S5: A measured amount of alkali-modified aerogel, after being ground in step S4, is introduced into the brackish water after step S3 and stirred for 60 minutes at a stirring speed of 300 rpm.

[0066] S6: The solid-liquid mixture from step S5 is placed into a candle filter for filtration to obtain the solution and solid phase, thus completing the purification of brackish water.

[0067] The test results are shown in Table 1 below. Table 1 presents the test results for Example 1 and Comparative Examples 1 and 2 of this application:

[0068]

[0069]

[0070] Table 1

[0071] As shown in Table 1 above, when aerogel is soaked in brackish water for 10 minutes, it cannot completely remove metal ions such as calcium, magnesium, barium, lead, mercury, arsenic, and cadmium from the brackish water. When aerogel is soaked in brackish water for 30 minutes, it can basically completely remove metal ions such as calcium, magnesium, barium, lead, mercury, arsenic, and cadmium from the brackish water. When aerogel is soaked in brackish water for 60 minutes, it can basically completely remove metal ions such as calcium, magnesium, barium, lead, mercury, arsenic, and cadmium from the brackish water, with the same effect as soaking for 30 minutes. Therefore, soaking for 30 minutes has the best effect.

[0072] Adsorption Mechanism: Acid-modified aerogels are formed by sol-geling sodium silicate solution with hydrochloric acid. Sol-geling occurs under weakly acidic conditions, resulting in a high degree of hydrolysis and a well-developed three-dimensional network of dispersed pores. Therefore, the primary adsorption mechanism is physical adsorption. Organic matter enters the pores and is adsorbed into the pores through van der Waals forces between molecules. The physical adsorption capacity is far greater than that of substances like activated carbon. Surface hydroxyl groups can effectively adsorb ions such as calcium, magnesium, and barium.

[0073] Alkali-modified aerogels are produced by adding ammonia water droplets to silica gel to form a sol-gel in a weakly alkaline environment. The ammonia is then used for modification, allowing the aerogel to exchange with metal ions through coordination complexation, thereby chemically adsorbing heavy metal ions such as lead, mercury, arsenic, and cadmium.

[0074] Comparative Example 3

[0075] This comparative example includes the following steps:

[0076] S1: Grind the acid-modified aerogel to 100 mesh using a planetary ball mill;

[0077] S2: A measured amount of acid-modified aerogel ground in step S1 is fed into brackish water and stirred for 30 minutes at a stirring speed of 180 rpm.

[0078] S3: Place the solid-liquid mixture from step S2 into a ceramic disc centrifuge for filtration to obtain a solution and a solid phase;

[0079] S4: Grind the alkali-modified aerogel to 100 mesh using a grinding mill;

[0080] S5: A measured amount of alkali-modified aerogel, after being ground in step S4, is introduced into the brackish water after step S3 and stirred for 30 minutes at a stirring speed of 180 rpm.

[0081] S6: The solid-liquid mixture from step S5 is placed into a candle filter for filtration to obtain the solution and solid phase, thus completing the purification of brackish water.

[0082] Comparative Example 4

[0083] This comparative example includes the following steps:

[0084] S1: Grind the acid-modified aerogel to 100 mesh using a planetary ball mill;

[0085] S2: A measured amount of acid-modified aerogel ground in step S1 is fed into brackish water and stirred for 30 minutes at a stirring speed of 600 rpm.

[0086] S3: Place the solid-liquid mixture from step S2 into a ceramic disc centrifuge for filtration to obtain a solution and a solid phase;

[0087] S4: Grind the alkali-modified aerogel to 100 mesh using a grinding mill;

[0088] S5: A measured amount of acid-modified aerogel, after being ground in step S4, is introduced into the brackish water after step S3 and stirred for 30 minutes at a stirring speed of 600 rpm.

[0089] S6: The solid-liquid mixture from step S5 is placed into a candle filter for filtration to obtain the solution and solid phase, thus completing the purification of brackish water.

[0090] The test results are shown in Table 2 below. Table 2 presents the test results of Example 1 and Comparative Examples 3 and 4 of this application:

[0091]

[0092]

[0093] Table 2

[0094] As shown in Table 2 above, when the aerogel is immersed in brackish water and stirred at 180 rpm, the aerogel cannot be completely dispersed in the brackish water, resulting in incomplete removal of ions from the brackish water. At a stirring speed of 300 rpm, metal ions such as calcium, magnesium, barium, lead, mercury, arsenic, and cadmium are basically removed from the brackish water. At a stirring speed of 600 rpm, the removal effect is basically the same as at 300 rpm, but it is also prone to causing the brackish water to splash out of the brackish water tank; therefore, 300 rpm is chosen for energy conservation.

[0095] Adsorption Mechanism: Acid-modified aerogels are formed by sol-geling sodium silicate solution with hydrochloric acid. Sol-geling occurs under weakly acidic conditions, resulting in a high degree of hydrolysis and a well-developed three-dimensional network of dispersed pores. Therefore, the primary adsorption mechanism is physical adsorption. Organic matter enters the pores and is adsorbed into the pores through van der Waals forces between molecules. The physical adsorption capacity is far greater than that of substances like activated carbon. Surface hydroxyl groups can effectively adsorb ions such as calcium, magnesium, and barium.

[0096] Alkali-modified aerogels are produced by adding ammonia water droplets to silica gel to form a sol-gel in a weakly alkaline environment. The ammonia is then used for modification, allowing the aerogel to exchange with metal ions through coordination complexation, thereby chemically adsorbing heavy metal ions such as lead, mercury, arsenic, and cadmium.

[0097] According to the above-described scheme of the present invention, the present invention utilizes different modified aerogels to adsorb ions such as calcium, magnesium, barium, lead, mercury, arsenic, sulfate, and chloride in brackish water, as well as organic matter in brackish water. For cations such as calcium, magnesium, and barium, alkali-modified silica aerogels with ion exchange functions can be selected; for anions such as lead, mercury, arsenic, sulfate, and chloride, acid-modified silica aerogels with anionic functional groups that have adsorption functions can be selected. This scheme can not only solve the problem of high-value utilization of heavy metal solidification, but also achieve efficient utilization of brackish water resources through purification.

[0098] Finally, it should be noted that the above embodiments are merely preferred embodiments, and are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made to it in form and detail without departing from the scope defined by the claims of the present invention.

Claims

1. A method for purifying brackish water using modified aerogels, characterized in that, include: Acid-modified aerogel was added to brackish water and stirred to form a first solid-liquid mixture; The first solid-liquid mixture was subjected to solid-liquid separation to obtain pre-purified brackish water; Add alkali-modified aerogel to the initially purified brackish water and stir to form a second solid-liquid mixture; The second solid-liquid mixture is subjected to solid-liquid separation to complete the purification of brackish water; Add acid-modified aerogel to brackish water and stir and soak for 30 minutes at a stirring speed of 300 rpm. Add alkali-modified aerogel to brackish water and stir and soak for 30 minutes at a stirring speed of 300 rpm. The acid-modified aerogel is a number of particulate acid-modified aerogels with a particle size of less than 100 mesh. The alkali-modified aerogel is a number of granular alkali-modified aerogels with a particle size of less than 100 mesh. The acid-modified aerogel is prepared by adding hydrochloric acid to sodium silicate to form a sol-gel; the acid-modified aerogel adsorbs heavy metal ions including lead, mercury, arsenic and cadmium, as well as organic matter including benzene, phenol, ether and naphthalene in brackish water. The alkali-modified aerogel is prepared by adding ammonia water to silica gel; the alkali-modified aerogel exchanges sodium, potassium, calcium, magnesium and barium ions in brackish water to achieve graded removal of ions from brackish water.

2. The method for purifying brackish water using modified aerogel according to claim 1, characterized in that, The volume ratio of the brackish water to the acid-modified aerogel is 1:150-1:

250.

3. The method for purifying brackish water using modified aerogel according to claim 1, characterized in that, The ratio of the brackish water to the alkali-modified aerogel is 1:150-1:250.

Images