Method for removing chloride ions based on calcium-aluminum bimetallic oxide

Abstract

The invention discloses a method for removing chloride ions based on calcium-aluminum bimetal oxide, and relates to the technical field of wastewater treatment. The calcium-aluminum bimetallic hydroxide is prepared by adopting a coprecipitation method, and then the calcium-aluminum bimetallic hydroxide is calcined to obtain the calcium-aluminum bimetallic oxide. The calcium-aluminum dechlorinating agent is formed by adopting a roasting reconstruction method, the obtained calcium-aluminum dechlorinating agent has the advantages of large specific surface area and high adsorption performance, has an excellent adsorption effect on high-concentration chloride ions in a water body, is simple in preparation method and low in cost, can be recycled, and has good industrial production and market application prospects.

Description

Technical Field

[0001] The invention relates to the technical field of wastewater treatment, and in particular to a method for removing chloride ions based on calcium aluminum bimetallic oxide. Background Art

[0002] With the rapid development of industrial economy, the high-salt wastewater discharged in production has gradually increased. If the high-salt wastewater is discharged directly without treatment, it will not only cause water pollution and soil pollution, but also waste resources. High-salt wastewater is wastewater with high salt content, and the total mass fraction of salt is more than 1% (measured in NaCl content).

[0003] The main sources of high-salt wastewater are: (1) industrial wastewater, wastewater generated by refining, printing and dyeing, pharmaceutical and modern coal chemical industries; wastewater from food industries such as pickled products and meat processing, and leachate from garbage; (2) seawater, cooling circulating water or drainage in the process of industrial water use in coastal cities; (3) saline domestic sewage, which is the use of seawater and other salty water for flushing roads, flushing toilets, fire fighting and other domestic miscellaneous water.

[0004] Chloride ions in high-salt wastewater can cause certain harm to the environment and organisms, which can be mainly summarized as follows: (1) Land salinization. Direct discharge of high-salt wastewater will cause salt to crystallize in the soil, causing soil compaction and reduced fertility, inhibiting crop growth. (2) Excessive chloride ion concentration will suppress and poison the growth and development of microorganisms. Salting out will greatly reduce the activity of dehydrogenases. The high osmotic pressure of high-salt wastewater will cause cell dehydration and reduce cell activity. This will lead to the inability of microorganisms in the activated sludge of the biological treatment tank to survive, reducing the sewage treatment effect. (3) High-salt wastewater entering the groundwater body will cause the hardness of the groundwater to increase. If consumed for a long time, it will cause tooth damage and even kidney stones. (4) Corrosion of pipelines will seriously affect the water transmission capacity of pipelines, increase the failure rate of pipelines, and shorten the service life of pipelines.

[0005] Chloride ion is one of the most common anions in high-salt wastewater, and the research on chloride ion treatment technology in wastewater is of great significance. In order to avoid the impact of chlorine-containing wastewater directly discharged into the receiving water body on the environment and the impact of transportation to the sewage treatment plant on subsequent biochemical treatment, thermal method, membrane method and precipitation method are currently mainly used to remove chloride ions in chlorine-containing wastewater. Among them, thermal method and membrane method are widely used in engineering. The thermal method heats the high-salt wastewater to be treated to achieve fresh water vaporization, and at the same time increases the salt concentration in the original wastewater to saturation to precipitate it. The membrane method concentrates the material through the selective permeability of the membrane to achieve desalination. However, both have the disadvantages of high investment and operating costs, large footprint, high energy consumption, and complex operation. The precipitation method uses chemical agents and chloride ions to generate precipitation to achieve desalination. Although it is low-cost and the agents are easy to obtain, it has the disadvantages of low agent utilization and residual Ca in the solution. 2+ 、Al 3+Too high a temperature may cause harm to subsequent processing. Summary of the invention

[0006] The purpose of the present invention is to provide a method for removing chloride ions based on calcium aluminum bimetallic oxide, so as to solve the problems existing in the above-mentioned prior art and achieve efficient removal of chloride ions.

[0007] To achieve the above object, the present invention provides the following solutions:

[0008] The present invention provides a method for preparing a calcium aluminum bimetallic oxide, comprising the following steps:

[0009] The calcium aluminum double metal hydroxide is prepared by a co-precipitation method, and then calcined to obtain the calcium aluminum double metal oxide.

[0010] As a further preferred embodiment of the present invention, the calcination treatment is carried out under a protective atmosphere; the temperature of the calcination treatment is 450-800° C., and the time of the calcination treatment is 2-4 hours.

[0011] As a further preferred embodiment of the present invention, when the coprecipitation method is used to prepare calcium aluminum double hydroxide, the aluminum source and the calcium source used are Al 3+ With Ca 2+ The molar ratio is 1:1 to 1:4.

[0012] As a further preferred embodiment of the present invention, in the coprecipitation preparation process, the reaction temperature is 40° C. and the pH is 9.0-11.0.

[0013] As a further preference of the present invention, the preparation method comprises the following steps:

[0014] Under a protective atmosphere, Ca 2+ 、Al 3+ The mixed metal solution is mixed with an alkaline solution, and co-precipitated under a constant pH condition of pH = 9.0 to 11.0, and the obtained precipitate is dried and ground to obtain the calcium aluminum bimetallic oxide; then the calcium aluminum bimetallic oxide is calcined to obtain the calcium aluminum bimetallic oxide.

[0015] As a further preference of the present invention, the drying temperature is 105° C.; more preferably, the drying time is 24 h.

[0016] The present invention also provides a calcium aluminum bimetallic oxide prepared by the above preparation method.

[0017] The present invention further provides the use of the above calcium aluminum bimetallic oxide in dechlorination of water bodies.

[0018] The microstructure of the calcium aluminum bimetallic oxide in the present invention is a loose porous small particle structure, which has a memory effect and has the characteristic of restoring a layered structure.

[0019] As a further preferred embodiment of the present invention, the water body is high-chloride water body.

[0020] As a further preferred embodiment of the present invention, the chloride ion concentration in the water body is 1000-10000 mg / L.

[0021] As a further preferred embodiment of the present invention, during the application process, the water temperature is controlled to be 25-40°C.

[0022] In the present invention, the more preferred preparation process of calcium aluminum bimetallic oxide is as follows:

[0023] 1) Prepare solution A and solution B respectively. Solution A is a mixed solution containing Al(NO3)3 and Ca(NO3)2, and solution B is a mixed solution containing NaNO3 and NaOH. 3+ With Ca 2+ The molar ratio is 1:1 to 1:4, and the total ion concentration is 1 mol / L; the NaOH concentration in solution B is 2 mol / L, and the NaNO3 concentration is 1 mol / L. Use a peristaltic pump to simultaneously add solution A and solution B to the ultrapure water preheated in a water bath at a speed of 5 to 30 rpm. The whole process is carried out under the condition of passing 80 to 180 sccm nitrogen, and the system temperature is controlled to be 40°C and the pH is 9.0 to 11.0. At the same time, a magnetic stirrer is used to continuously stir vigorously. The obtained precipitate is sealed with plastic wrap and aged in a water bath for 18 hours. Let it stand to room temperature, centrifuge and wash the precipitate 6 times, then filter it, place the filtrate in an oven at 105°C to dry for 24 hours, grind it, and obtain calcium aluminum double metal hydroxide.

[0024] 2) Calcium aluminum double hydroxide is placed in a tube furnace and calcined at 450-800°C for 2-4 hours at a heating rate of 10°C / min, and then cooled to room temperature to obtain a dechlorination agent whose main substance is calcium aluminum double metal oxide (LDO). During the calcination process, 80-180 sccm of nitrogen is introduced.

[0025] The prepared dechlorinating agent is added into chlorine-containing wastewater with a chloride ion concentration of 1000 to 10000 mg / L, and dechlorination is performed at 25 to 40° C. The preferred dechlorination time is 30 to 120 minutes.

[0026] During the preparation of the material of the present invention, the material can be regulated by changing the cation ratio and the calcination temperature and time.

[0027] The preparation method of the invention is simple and efficient, and the subsequent precipitate can be recycled through alkali washing and roasting, thus solving the problem that a large amount of sludge will be generated in the chemical precipitation method.

[0028] The present invention discloses the following technical effects:

[0029] The present invention adopts a roasting reconstruction method to form a calcium aluminum dechlorinator. The obtained calcium aluminum dechlorinator has the advantages of large specific surface area and high adsorption performance, and has excellent adsorption effect on high-concentration chloride ions in water. The preparation method is simple, the cost is low, and it can be recycled, so it has good industrial production and market application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0031] Figure 1 The scanning electron microscope images of Ca-Al-LDHs and Ca-Al-LDO prepared in Example 1 of the present invention; wherein (a) is Ca-Al-LDHs, and (b) is Ca-Al-LDO;

[0032] Figure 2 N2 adsorption-desorption isotherm and pore size distribution diagram of Ca-Al-LDO prepared in Example 1 of the present invention;

[0033] Figure 3 N2 adsorption-desorption isotherms and pore size distribution diagram of Ca-Al-LDHs prepared in Example 1 of the present invention;

[0034] Figure 4 This is the XRD pattern of Ca-Al-LDO prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0035] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0036] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0037] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0038] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0039] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0040] In order to avoid interference from other anions in complex water quality, in the following embodiments and comparative examples of the present invention, all high-chloride wastewaters used for dechlorination research were prepared with NaCl solutions having a chloride ion concentration of 6500 mg / L (NaCl mass fraction of 1.1%).

[0041] The self-prepared solutions of all the embodiments and comparative examples of the present invention are prepared using ultrapure water (resistivity of 18.25 MΩ).

[0042] Example 1

[0043] Preparation of calcium aluminum bimetallic oxide (Ca-Al-LDO):

[0044] (1) Prepare 100 mL of solution A and solution B respectively: Solution A is a mixed solution containing Al(NO3)3 and Ca(NO3)2, Al 3+ :Ca 2+ The molar ratio is 1:3, and the total metal concentration is 1 mol / L; solution B is a mixed solution of NaNO3 and NaOH, with NaNO3 being 1 mol / L and NaOH being 2 mol / L. A peristaltic pump is used to simultaneously drop solution A and solution B into ultrapure water preheated in a water bath at a speed of 10 rpm. The entire process is carried out under the condition of nitrogen gas, and the system temperature is controlled to be 40°C and the pH is 10. At the same time, a mechanical stirrer is used to continuously stir vigorously. The obtained precipitate is sealed with plastic wrap and aged in a water bath for 18 hours. After standing to room temperature, the precipitate is centrifuged and washed 6 times and then filtered. The filtrate is placed in an oven and dried at 105°C for 24 hours to obtain calcium aluminum double hydroxides (Ca-Al-LDHs).

[0045] (2) The ground Ca-Al-LDHs were placed in a tube furnace and calcined at 500 °C for 4 h at a heating rate of 10 °C / min. After the temperature naturally cooled to room temperature, calcium aluminum bimetallic oxide (Ca-Al-LDO) was obtained.

[0046] The prepared Ca-Al-LDO was used as a dechlorinating agent for dechlorination of water bodies: 1.2 g of Ca-Al-LDO was added into 10 mL of wastewater with a chloride ion concentration of 6500 mg / L and oscillated at 30°C for 90 minutes.

[0047] The results showed that the removal rate of chloride ions in wastewater by Ca-Al-LDO was as high as 91.3%.

[0048] The Ca-Al-LDHs and Ca-Al-LDO prepared in Example 1 were structurally characterized:

[0049] Scanning electron microscopy (SEM, Zeiss Merlin Compact, Germany) was used to obtain the microstructures of Ca-Al-LDHs and Ca-Al-LDO materials, such as Figure 1 As shown. Figure 1 It can be seen that after calcination, Ca-Al-LDHs forms a loose and porous small particle structure.

[0050] The specific surface area and pore size of Ca-Al-LDHs and Ca-Al-LDO materials were obtained by using a fully automatic specific surface and porosity analyzer BET (Micromeritics ASAP 2460, USA), as shown in Table 1. By comparison, it can be seen that after calcination, the specific surface area and pore volume of Ca-Al-LDO are significantly increased, and the adsorption performance is improved.

[0051] Table 1 BET specific surface area and pore size results of Ca-Al-LDHs and Ca-Al-LDO

[0052]

[0053] Figure 2 , Figure 3 They are the N2 adsorption-desorption isotherms and pore size distribution diagrams of Ca-Al-LDO and Ca-Al-LDHs materials. The adsorption isotherms show that the samples are typical IV isotherms with H3-type hysteresis curves, indicating that they are mesoporous materials.

[0054] The phase composition of Ca-Al-LDO was obtained by X-ray diffractometer (XRD, Rigaku Ultima IV, Japan). Figure 4The results show that Ca-Al-LDO contains typical Ca2Al2O5·6H2O peaks, matching the standard card JCPDS database No.12-0008.

[0055] Example 2

[0056] The precipitate obtained after the above wastewater was put into the wastewater, and then desorbed and shaken for 8 hours using 0.1 mg / L NaCO3 solution, and then filtered. The precipitate was centrifugally washed 6 times and then filtered. The filtrate was placed in an oven and dried at 105°C for 24 hours. After grinding, it was placed in a tube furnace and calcined at 500°C for 4 hours at a heating rate of 10°C / min. After naturally cooling to room temperature, the desorbed and calcined material was put into 10 mL of wastewater with a chloride ion concentration of 6500 mg / L, and shaken for 90 minutes at 30°C. The desorption-calcination-adsorption cycle was repeated, and the chloride ion removal rate results are shown in Table 2.

[0057] Table 2

[0058]

[0059] Comparative Example 1:

[0060] The Ca-Al-LDHs prepared in step (1) of Example 1 was used as a dechlorinating agent for dechlorinating water: 1.2 g of Ca-Al-LDHs was added to 10 mL of wastewater with a chloride ion concentration of 6500 mg / L and shaken at 30°C for 90 minutes.

[0061] The results showed that the removal rate of chloride ions in wastewater by Ca-Al-LDHs was 44.2%.

[0062] Comparative Example 2

[0063] The only difference from Example 1 is that the calcination temperature in step (2) is different:

[0064] (1) Prepare 100 mL of solution A and solution B respectively: Solution A is a mixed solution containing Al(NO3)3 and Ca(NO3)2, Al 3+ :Ca 2+The molar ratio is 1:3, and the total metal concentration is 1 mol / L; solution B is a mixed solution of NaNO3 and NaOH, with NaNO3 being 1 mol / L and NaOH being 2 mol / L. A peristaltic pump is used to simultaneously drop solution A and solution B into ultrapure water preheated in a water bath at a speed of 10 rpm. The entire process is carried out under the condition of nitrogen gas, and the system temperature is controlled to be 40°C and the pH is 10. At the same time, a mechanical stirrer is used to continuously stir vigorously. The obtained precipitate is sealed with plastic wrap and aged in a water bath for 18 hours. After standing to room temperature, the precipitate is centrifuged and washed 6 times and then filtered. The filtrate is placed in an oven and dried at 105°C for 24 hours to obtain calcium aluminum double hydroxides (Ca-Al-LDHs).

[0065] (2) The ground Ca-Al-LDHs were placed in a tube furnace and calcined at 200 °C for 4 h at a heating rate of 10 °C / min. After the temperature naturally cooled to room temperature, calcium aluminum bimetallic oxide (Ca-Al-LDO) was obtained.

[0066] The prepared Ca-Al-LDO was used as a dechlorinating agent for dechlorination of water bodies: 1.2 g of Ca-Al-LDO was added into 10 mL of wastewater with a chloride ion concentration of 6500 mg / L and oscillated at 30°C for 90 minutes.

[0067] The results showed that the removal rate of chloride ions in wastewater by Ca-Al-LDO was 56.8%.

[0068] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing calcium aluminum bimetallic oxide, characterized in that: The following steps are involved: The calcium aluminum double metal hydroxide is prepared by a co-precipitation method, and then calcined to obtain the calcium aluminum double metal oxide.

2. The preparation method according to claim 1, characterized in that: The calcination treatment is carried out under a protective atmosphere; the temperature of the calcination treatment is 450-800° C., and the time of the calcination treatment is 2-4 hours.

3. The preparation method according to claim 1, characterized in that: When the coprecipitation method is used to prepare calcium aluminum double hydroxide, the aluminum source and the calcium source used are Al 3+ With Ca 2+ The molar ratio is 1:1 to 1:

4.

4. The preparation method according to claim 1, characterized in that: During the coprecipitation preparation process, the reaction temperature is 40° C. and the pH is 9.0-11.

0.

5. The preparation method according to claim 1, characterized in that: The following steps are involved: Under a protective atmosphere, Ca 2+ 、Al 3+ The mixed metal solution is mixed with an alkaline solution, and co-precipitation is carried out under a constant pH condition of pH = 9.0 to 11.

0. The obtained precipitate is dried to obtain the calcium aluminum bimetallic oxide; then the calcium aluminum bimetallic oxide is calcined to obtain the calcium aluminum bimetallic oxide.

6. The calcium aluminum bimetallic oxide prepared by the preparation method according to any one of claims 1 to 5.

7. Use of the calcium aluminum bimetallic oxide as claimed in claim 6 in dechlorination of water bodies.

8. The use according to claim 7, characterized in that The chloride ion concentration in the water body is 1000-10000 mg / L.

9. The use according to claim 7, characterized in that During the application process, the water temperature is controlled at 25-40℃.

Images