A calcium aluminum-based bimetallic oxide dechlorinating agent and its preparation method and application

Abstract

The present invention relates to a calcium aluminum-based bimetallic oxide dechlorinator and a preparation method and application thereof. The dechlorinator is prepared by the following preparation method: (1) adding nitric acid to an aluminum source, reacting under light-proof conditions, then adding a calcium source and hydrogen peroxide, and then drying, grinding and screening to obtain a precursor; (2) calcining the obtained precursor, and then grinding and screening to obtain a target product. The dechlorinator is used to remove chloride ions. The specific process includes: weighing the dechlorinator and adding a Cl-containing ‑ Compared with the prior art, the calcium aluminum-based bimetallic oxide dechlorinator of the present invention has a higher ability to remove chloride ions, and the dechlorinator has a larger temperature and pH range of use.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater treatment and relates to a calcium-aluminum-based bimetallic oxide dechlorinator and a preparation method and application thereof. Background Art

[0002] Every year, coal chemical industry, flue gas desulfurization, petroleum industry, thermal power and other industries produce a large amount of chlorine-containing wastewater. The discharge of such wastewater creates a highly chlorinated environment, leading to corrosion of industrial equipment and harm to building materials. - ) is considered to be one of the main drivers of pollution and environmental damage. It not only poses a threat to factory water reuse, but also pollutes soil and surface water. In addition, due to its high mobility, artificially produced Cl- will interfere with the biogeochemical cycle of chlorine in natural ecosystems. In order to control the damage to the environment caused by chlorine-containing wastewater, many provinces and cities in my country have introduced different emission standards. Taking industrial wastewater as an example, the Shanghai Comprehensive Wastewater Discharge Standard (DB31 / 199-2018) clearly states that the limit on chloride emissions from saponin industries is 200-300 mg / L; the Liaoning Province Comprehensive Wastewater Discharge Standard (DB21 / 1627-2008) shows that chloride (as Cl - The maximum concentration allowed for direct discharge is 400 mg / L, and the maximum concentration requirement for discharge into a sewage treatment plant is reduced to 1000 mg / L.

[0003] Cl in existing technology - The removal methods mainly include solvent extraction, membrane separation, electrochemical method, adsorption, evaporation crystallization, ion exchange and chemical precipitation. - There are many ways to remove Cl, but most of them have bottlenecks in the industrial application of technology. Membrane separation and evaporation crystallization processes have been applied in engineering, but there are problems such as complex process flow and high difficulty in operation and management; adsorption and solvent extraction methods have problems such as adsorbent regeneration and extractant stripping, which can easily cause Cl - Secondary enrichment of , thus generating new pollution; electrochemical removal of Cl - The process requires an external power supply, which has the disadvantages of high energy consumption, expensive electrodes and frequent equipment maintenance. In addition, the gases such as Cl2 and H2 produced by this method have certain safety hazards and require extremely high engineering safety facilities. The ion exchange method has a simple process and low investment cost, but it has problems such as easy saturation of the exchange medium, resulting in frequent clarification and regeneration. In contrast, the chemical precipitation method for treating high-salinity wastewater has a simple process flow and is environmentally friendly, and has been widely used. However, the existing chemical precipitation method mostly uses a mixture of multiple reagents and is greatly affected by the pH value of the aqueous solution and the ambient temperature, so the Cl - The removal capacity is low. Summary of the invention

[0004] The purpose of the present invention is to provide a calcium aluminum-based bimetallic oxide dechlorinating agent and its preparation method and application, so as to overcome the problem that the chemical precipitation method for treating high-salt wastewater in the prior art is greatly affected by the pH value of the aqueous solution or the ambient temperature, or the Cl - The present invention prepares a calcium aluminum-based bimetallic oxide dechlorinator for removing chloride in water. - The preparation method of the dechlorinator is simple and environmentally friendly, and has a large temperature and pH range of use. - Has excellent removal performance.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] One of the technical solutions of the present invention provides a method for preparing a calcium-aluminum-based bimetallic oxide dechlorinator, comprising the following steps:

[0007] (1) adding nitric acid to an aluminum source and reacting the mixture in a dark environment, then adding a calcium source and hydrogen peroxide, and drying, grinding and screening the mixture to obtain a precursor;

[0008] (2) The obtained precursor is calcined and then ground and sieved to obtain the desired product.

[0009] Furthermore, in step (1), the aluminum source includes aluminum oxide, aluminum hydroxide or pseudo-boehmite.

[0010] Furthermore, in step (1), the calcium source includes calcium carbonate, calcium oxide or calcium hydroxide.

[0011] Furthermore, in step (1), the concentration of nitric acid is 0.1 to 10 mol / L.

[0012] Furthermore, in step (1), the concentration of the hydrogen peroxide solution is 10 wt % to 50 wt %.

[0013] Furthermore, in step (1), the molar ratio of nitric acid to aluminum is (0.5-5):1, the molar ratio of calcium in the calcium source to hydrogen peroxide in hydrogen peroxide is (0.5-5):1, and the molar ratio of calcium to aluminum in the calcium source and aluminum source is (1-5):1.

[0014] Furthermore, in step (1), the reaction is carried out in the dark for 0.5 to 5 hours.

[0015] Furthermore, in step (1), the drying temperature is 20 to 150°C.

[0016] Furthermore, in step (1), the ground product is sieved using a 100-mesh sieve to obtain the precursor.

[0017] Furthermore, in step (2), calcination is carried out in an air atmosphere, the calcination temperature is 600-1200° C., the calcination constant temperature time is 0.5-4 h, and the calcination heating rate is 1-10° C. / min.

[0018] Furthermore, in step (2), the ground product is sieved using a 100-mesh sieve to obtain the target product.

[0019] The second technical solution of the present invention provides a calcium-aluminum-based bimetallic oxide dechlorinator, which is prepared by the above-mentioned preparation method.

[0020] The third technical solution of the present invention provides an application of a calcium-aluminum-based bimetallic oxide dechlorinator, which is used to remove chloride ions. The specific process includes:

[0021] Weigh the dechlorination agent and add Cl - The reaction is carried out in the wastewater.

[0022] Furthermore, the reaction time is 3 to 12 hours.

[0023] Furthermore, the reaction temperature is 10-65°C.

[0024] Furthermore, Cl - The pH of the wastewater is 3-11.

[0025] Furthermore, Cl - Wastewater contains Ca 2+ Mg 2+ Or Na + . Contains Cl - The presence of some cations in wastewater has an important effect on the removal of Cl - There are some positive effects, such as Ca 2+ Mg 2+ and Na + etc., and the order of the favorable effects of the above cations is Ca 2+ >Mg 2 + >Na + .

[0026] The present invention uses the prepared calcium aluminum-based bimetallic oxide to remove chloride ions from wastewater. The specific operation process can be carried out according to the following steps: accurately weigh a certain mass of dechlorinating agent, add a Cl - Wastewater (the pH of the solution is between 3 and 11) is placed in an environment of 10 to 65°C for 3 to 12 hours. After the reaction is completed, the liquid is measured using the method shown in GB / T15453-2008 for residual Cl in the wastewater. - concentration.

[0027] The dechlorinator of the present invention is prepared from a calcium-containing compound and an aluminum-containing compound. The Ca-O bond and the Al-O bond are broken and reorganized to form Ca-O-Al during the nitric acid soaking and roasting treatment stages. The dechlorinator has a solid worm-like structure and is effective for Cl - The removal rate is high and the pH application range is wide.

[0028] The dechlorinator of the present invention has a wide pH applicable range, shows excellent chloride ion removal performance, and has the advantages of simple preparation process, environmental protection, etc., and has broad application prospects in the field of water treatment technology.

[0029] In the preparation process of the calcium aluminum-based bimetallic oxide dechlorinator of the present invention, the presence of nitric acid and hydrogen peroxide can promote the breaking of the valence bond in the aluminum source in preparation for the subsequent full reaction with the calcium source. Since concentrated nitric acid is easily decomposed by light, the reaction needs to be carried out under light-proof conditions in the early stage. The mixture after the reaction of the calcium source and the aluminum source is dried to obtain a calcium aluminum-based bimetallic hydroxide, which is a precursor. The powdered sample is subsequently obtained by grinding and screening to ensure that a purer bimetallic oxide is formed during the roasting process. High temperature can promote the release of a large amount of non-metallic elements such as C, N, H in the precursor in the form of gaseous oxides, thereby realizing the transformation of layered bimetallic hydroxides to bimetallic oxides. Finally, the calcined bimetallic oxide is screened and ground again to increase the contact area between the dechlorinator and the solution during the reaction process, thereby improving the dechlorination capacity.

[0030] Based on a large number of experimental investigations, the present invention determines the range of the concentration of nitric acid and hydrogen peroxide, the time of light-proof reaction, etc. in the preparation of calcium-aluminum-based bimetallic oxide dechlorinators. Beyond this range, the dechlorination efficiency of the dechlorinator will decrease. In addition, the ratio of the addition amount of each raw material (such as the calcium-aluminum molar ratio) and the roasting temperature have a significant effect on the crystal structure, material type, purity, etc. of the prepared product, and thus affect the dechlorination ability of the dechlorinator. The importance of this will be demonstrated by examples later.

[0031] Compared with the prior art, the present invention has the following advantages:

[0032] (1) The calcium-aluminum-based bimetallic oxide dechlorinator of the present invention is prepared by an acid leaching and roasting synthesis method. Compared with the prior art, the preparation method of the present invention is simpler and the conditions are easy to control. No organic solvent is required under the preparation conditions involved in this method, which reduces toxicity. In addition, this method does not require the protection of an inert gas, which simplifies the equipment conditions and processes. The calcium-aluminum molar ratio, the concentration of nitric acid, the concentration of hydrogen peroxide, the molar ratio of aluminum to nitric acid, the molar ratio of calcium to hydrogen peroxide, the roasting temperature range, etc. involved in the preparation are all wide, and the conditions are easy to control. Due to the above preparation advantages, the calcium-aluminum-based bimetallic oxide dechlorinator can be mass-produced by the acid leaching and roasting method.

[0033] (2) The calcium aluminum-based bimetallic oxide dechlorinator of the present invention has a high ability to remove chloride ions, and the dechlorination process has strong adaptability to reaction conditions. - The average efficiency is about 160g / mg. Secondly, the dechlorination agent reacts at an ambient temperature of 10 to 65°C, and the dechlorination efficiency only differs by about 5%. Therefore, the reaction can be carried out at room temperature without heating or cooling, which is economical. In addition, by changing the pH value of the water sample, the removal ability of calcium-aluminum-based bimetallic oxides on the target substance at different pH values ​​was studied. The results showed that when the pH value was between 3 and 11, the removal rate of calcium-aluminum-based bimetallic oxides on chloride ions did not change much, indicating that the dechlorination agent of the present invention is suitable for weakly acidic, neutral and alkaline Cl - Efficient removal.

[0034] (3) Different from common dechlorination methods such as ultra-high lime aluminum method, the calcium aluminum-based bimetallic oxide of the present invention is effective in removing Cl - At the same time, it can also meet the removal of calcium and magnesium, and due to its unique dechlorination mechanism, the presence of calcium and magnesium ions can further improve the removal of Cl - The removal efficiency increased from 73% to 96.5% and 96% respectively. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a diagram showing the effect of cation type on the chlorine removal capacity of the chlorine removal agent in Example 4.

[0036] Figure 2 This is the XRD spectrum of the dechlorination agent after the reaction in Example 4.

[0037] Figure 3 The XRD spectra of the products prepared in Examples 5-8 and Comparative Examples 1-2 are shown.

[0038] Figure 4 The Cl of the products prepared in Examples 5-8 and Comparative Examples 1-2 - Removal rate.

[0039] Figure 5 This is a graph showing the chlorine removal capacity of the chlorine removal agent of Example 6 in different pH values ​​and in different solutions.

[0040] Figure 6 This is the SEM image of the dechlorination agent of Example 1.

[0041] Figure 7 The chlorine removal efficiency and adsorption capacity of the chlorine removal agent in Example 9 at different reaction temperatures.

[0042] Figure 8(a) The removal rate of the dechlorinator in different cationic solutions of Example 10; (b) The calcium ion concentration in the CaCl2 solution; (c) The calcium ion concentration in the NaCl solution; (d) The calcium and magnesium ion concentrations in the MgCl2 solution. DETAILED DESCRIPTION

[0043] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0044] In the following examples, unless otherwise specified, raw materials or processing techniques are conventional commercially available raw materials or conventional processing techniques in the art.

[0045] Example 1

[0046] A method for preparing a calcium-aluminum-based bimetallic oxide dechlorinator with Al(OH)3 as an aluminum source, CaCO3 as a calcium source, Ca / Al of 1:1 (molar ratio) and a calcination temperature of 800°C, the specific steps are as follows:

[0047] Accurately weigh 15.6g Al(OH)3, pour in 10mL 2mol / L nitric acid solution, stir evenly, and place in the dark for 4h, which is called solution A; accurately weigh 20.018g CaCO3, add solution A in small amounts several times to form mixture B; use a measuring cylinder to measure 10mL 30wt% hydrogen peroxide, add small amounts several times to mixture B, and stir evenly with a glass rod to form mixture C; place the prepared mixture C in an oven at 105℃ and dry for 8h to form mixture D; place the dried mixture D in an agate mortar and grind it, and pass the ground particles through a 100-mesh sieve; the sieved mixture D is placed in a muffle furnace for roasting, and the temperature is increased to 800℃ at a heating rate of 5℃ / min and kept constant for 2h to synthesize product E; product E is ground and sieved again (100 mesh) to form a calcium-aluminum-based bimetallic oxide dechlorinator. Figure 6 As shown, this is the SEM picture of the dechlorination agent. It can be seen that the dechlorination agent has a solid worm-like structure.

[0048] Example 2

[0049] Accurately weigh 2 g of the dechlorinating agent prepared in Example 1, add 50 mL of 7090 mg / L Cl-containing - The mixture was placed in a 25°C constant temperature incubator and shaken for 12 hours. After the reaction was completed, the mixture was filtered through a 0.45 μm cellulose acetate membrane to separate the solid and liquid. The liquid was determined by the method shown in GB / T 15453-2008 for the Cl content. - Cl in water -The residual concentration is 80%.

[0050] Example 3

[0051] A method for preparing a calcium-aluminum-based bimetallic oxide dechlorinator with α-Al2O3 as an aluminum source, CaO as a calcium source, Ca / Al being 2 (molar ratio) and a calcination temperature of 900°C, the specific steps are as follows:

[0052] Accurately weigh 5.098g of α-Al2O3, pour in 20mL of 5mol / L nitric acid solution, stir evenly, and place in the dark for 5h, which is called solution A; accurately weigh 11.216g of CaO, add solution A in small amounts several times to form mixture B; use a measuring cylinder to measure 10mL of 30wt% hydrogen peroxide, add mixture B in small amounts several times, and stir evenly with a glass rod to form mixture C; place the prepared mixture C in an oven at 105°C and dry for 8h to form mixture D; place the dried mixture D in an agate mortar and grind it, and pass the ground particles through a 100-mesh sieve; the sieved mixture D is placed in a muffle furnace for roasting treatment, and the temperature is increased to 900°C at a heating rate of 1°C / min and kept constant for 2h to synthesize product E; product E is ground and sieved again (100 mesh) to form a calcium-aluminum-based bimetallic oxide dechlorinator.

[0053] Example 4

[0054] The material prepared in Example 3 was used to remove Cl from water according to the method of Example 2. - , the difference is that the raw materials for chlorine-containing water are NaCl, CaCl2 and MgCl2 respectively. Figure 1 As shown in the figure, the dechlorinating agent has a great influence on the Cl - The removal rate of chlorine removal agent in MgCl2 solution is the highest, which is 87.50%. - The removal rate of chlorine removal agent in NaCl solution was 82.00%. - The removal rate of is the lowest, which is 57.29%.

[0055] The product after reaction was dried and then characterized by XRD. Figure 2 As shown. Figure 2 It can be seen that the test shows that after the reaction, the calcium-aluminum-based bimetallic oxide dechlorinator gradually turns into Freund's salt (Ca2Al(OH)6Cl·2H2O), proving that Cl - The transition from liquid phase to solid phase has been successful.

[0056] Example 5

[0057] A method for preparing a calcium-aluminum-based bimetallic oxide dechlorinator with γ-Al2O3 as an aluminum source, CaO as a calcium source, Ca / Al of 1.5 (molar ratio) and a calcination temperature of 600°C, the specific steps are as follows:

[0058] Accurately weigh 5.098g of γ-Al2O3, pour in 10mL of 5mol / L nitric acid solution, stir evenly, and place in the dark for 5h, which is called solution A; accurately weigh 8.412g of CaO, add solution A in small amounts several times to form mixture B; use a measuring cylinder to measure 15mL of 30wt% hydrogen peroxide, add mixture B in small amounts several times, and stir evenly with a glass rod to form mixture C; place the prepared mixture C in an oven at 60°C and dry for 12h to form mixture D; place the dried mixture D in an agate mortar and grind it, and pass the ground particles through a 100-mesh sieve; the sieved mixture D is placed in a muffle furnace for roasting treatment, and the temperature is increased to 600°C at a heating rate of 10°C / min and kept constant for 1h to synthesize product E; product E is ground and sieved again (100 mesh) to form a calcium-aluminum-based bimetallic oxide dechlorinator.

[0059] Example 6

[0060] A method for preparing a calcium-aluminum-based bimetallic oxide dechlorinator with γ-Al2O3 as an aluminum source, CaO as a calcium source, Ca / Al of 1.5 (molar ratio) and a calcination temperature of 700°C, the specific steps are as follows:

[0061] Accurately weigh 5.098g of γ-Al2O3, pour in 10mL of 5mol / L nitric acid solution, stir evenly, and place in the dark for 5h, which is called solution A; accurately weigh 8.412g of CaO, add solution A in small amounts several times to form mixture B; use a measuring cylinder to measure 15mL of 30wt% hydrogen peroxide, add mixture B in small amounts several times, and stir evenly with a glass rod to form mixture C; place the prepared mixture C in an oven at 60°C and dry for 12h to form mixture D; place the dried mixture D in an agate mortar and grind it, and pass the ground particles through a 100-mesh sieve; the sieved mixture D is placed in a muffle furnace for roasting treatment, and the temperature is increased to 700°C at a heating rate of 10°C / min and kept constant for 1h to synthesize product E; product E is ground and sieved again (100 mesh) to form a calcium-aluminum-based bimetallic oxide dechlorinator.

[0062] Example 7

[0063] A method for preparing a calcium-aluminum-based bimetallic oxide dechlorinator with γ-Al2O3 as an aluminum source, CaO as a calcium source, Ca / Al of 1.5 (molar ratio) and a calcination temperature of 900°C, the specific steps are as follows:

[0064] Accurately weigh 5.098g of γ-Al2O3, pour in 10mL of 5mol / L nitric acid solution, stir evenly, and place in the dark for 5h, which is called solution A; accurately weigh 8.412g of CaO, add solution A in small amounts several times to form mixture B; use a measuring cylinder to measure 15mL of 30wt% hydrogen peroxide, add mixture B in small amounts several times, and stir evenly with a glass rod to form mixture C; place the prepared mixture C in an oven at 60°C and dry for 12h to form mixture D; place the dried mixture D in an agate mortar and grind it, and pass the ground particles through a 100-mesh sieve; the sieved mixture D is placed in a muffle furnace for roasting treatment, and the temperature is increased to 900°C at a heating rate of 10°C / min and kept constant for 1h to synthesize product E; product E is ground and sieved again (100 mesh) to form a calcium-aluminum-based bimetallic oxide dechlorinator.

[0065] Example 8

[0066] A method for preparing a calcium-aluminum-based bimetallic oxide dechlorinator with γ-Al2O3 as an aluminum source, CaO as a calcium source, Ca / Al of 1.5 (molar ratio) and a calcination temperature of 1200° C., the specific steps are as follows:

[0067] Accurately weigh 5.098g of γ-Al2O3, pour in 10mL of 5mol / L nitric acid solution, stir evenly, and place in the dark for 5h, which is called solution A; accurately weigh 8.412g of CaO, add solution A in small amounts several times to form mixture B; use a measuring cylinder to measure 15mL of 30wt% hydrogen peroxide, add mixture B in small amounts several times, and stir evenly with a glass rod to form mixture C; place the prepared mixture C in an oven at 60°C and dry for 12h to form mixture D; place the dried mixture D in an agate mortar and grind it, and pass the ground particles through a 100-mesh sieve; the sieved mixture D is placed in a muffle furnace for roasting treatment, and the temperature is raised to 1200°C at a heating rate of 10°C / min and kept constant for 1h to synthesize product E; product E is ground and sieved again (100 mesh) to form a calcium-aluminum-based bimetallic oxide dechlorinator.

[0068] Comparative Example 1

[0069] Compared with Example 5, most of the above are the same, except that the calcination temperature is changed to 500°C to prepare a dechlorinating agent. Dechlorination was carried out according to the method shown in Example 2. The results are shown in the attached figure. Figure 4 As shown, Cl - The removal rate is less than 30%, which is less than that of the calcium aluminum-based bimetallic oxide dechlorinator prepared in Example 5. This proves that it is difficult to prepare a dechlorinator with good performance at a calcination temperature below 600°C.

[0070] Comparative Example 2

[0071] Compared with Example 8, most of the above are the same, except that the calcination temperature is changed to 1300°C, and the dechlorination agent is prepared. Dechlorination is carried out according to the method shown in Example 2. The results are shown in the attached figure. Figure 4 As shown, Cl - The removal rate is 75%, which is less than the calcium aluminum-based bimetallic oxide dechlorinator (95%) prepared in Example 8. This shows that too high a roasting temperature not only consumes a lot of energy, but also has a negative impact on the dechlorination ability of the dechlorinator.

[0072] The products prepared in Examples 5-8 and Comparative Examples 1-2 were characterized by XRD. The results are shown in the attached figure. Figure 3 As shown, it shows that the prepared material is a calcium aluminum-based bimetallic oxide. Figure 3 It can be seen that when the calcination temperature is too low, it is difficult to form a bimetallic oxide, and when the calcination temperature is too high, the main components of the formed calcium aluminum-based bimetallic oxide change. The calcium aluminum-based bimetallic oxide dechlorinator prepared by Examples 5-8 and Comparative Examples 1-2 of the present invention is used to dechlorinate according to the method shown in Example 2, and the optimal calcination temperature of 600-1200°C is determined by its dechlorination effect and XRD characterization.

[0073] The dechlorinating agent prepared in Example 6 was used to remove Cl in water according to the method of Example 2. - , the difference is that the pH values ​​of the sample solutions were adjusted to 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 and 14 respectively. Figure 5 As shown in the figure, when the solution pH value is 3-10, the effect on the removal of chlorine by calcium-aluminum-based bimetallic oxide is small. When the pH value is greater than 10, the Cl in NaCl solution and MgCl2 - The removal rate of Cl in CaCl2 began to decrease. - The removal rate began to increase suddenly until pH>12 and then began to decrease.

[0074] Example 9

[0075] The material prepared in Example 6 was used to remove Cl- from water in the same manner as in Example 2, except that the chlorine-containing water was a CaCl2 solution and the reaction temperatures were 10°C, 25°C, 45°C and 65°C, respectively. Figure 7 As shown, the chloride ion removal rates are 88.82%, 92.44%, 90.16% and 88.83% respectively, and the adsorption capacity of the dechlorinating agent for chloride ions is 158.65g / mg, 163.70g / mg, 160.88g / mg and 157.77g / mg respectively. Under different reaction temperature conditions, the dechlorination performance of the dechlorinating agent is relatively stable.

[0076] Example 10

[0077] The material prepared in Example 6 was used to remove Cl- from water in the same manner as in Example 2, except that the dosage was 4 g and the chlorine-containing water was NaCl, CaCl2, and MgCl2 solution, respectively. Figure 8 As shown in a, the removal rate of Cl- by the dechlorinator in CaCl2 solution is the highest, which is 96.5%, followed by MgCl2 solution, which is 96%; the removal rate in NaCl solution is 73%. Figure 8 b is the Ca content in the CaCl2 solution when the dechlorination reaction occurs 2+ Concentration, attached Figure 8 c is the Ca content in the NaCl solution when the dechlorination reaction occurs 2+ Concentration, attached Figure 8 d is the Ca content in the MgCl2 solution when the dechlorination reaction occurs. 2+ Mg 2+ In the salt solution, Ca and Al contained in the dechlorinator will dissolve quickly, and the Ca 2+ 、Al(OH)4 - As the reaction proceeds, Ca 2+ With Al(OH)4 - Combine to form a positively charged layer, attracting Cl-. When the solution itself contains Ca 2+ When Mg 2+ When present, Mg 2+ Will occupy Ca first 2+ vacancy, making Ca 2+ Large amount of dissolution helps to remove Cl - In addition, due to Na + It is a soluble salt and cannot occupy Ca 2+ Vacancies promote its dissolution, and it cannot react with Al(OH)4 - The phase interaction forms a layer, so the Cl in the NaCl solution - The degree of removal is relatively low.

[0078] Comparative Example 3:

[0079] Compared with Example 6, most of the above are the same, except that no calcium source is added, and a dechlorinating agent is prepared. Dechlorination is carried out according to the method shown in Example 2, Cl - The removal rate is 0, which proves that calcium is indispensable in the preparation of dechlorinators.

[0080] Comparative Example 4:

[0081] Compared with Example 6, most of the above are the same, except that no aluminum source is added, and a dechlorination agent is prepared. Dechlorination is carried out according to the method shown in Example 2, Cl - The removal rate is 0, which proves that aluminum is indispensable in the preparation of dechlorination agent.

[0082] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for preparing a calcium-aluminum-based bimetallic oxide dechlorinating agent, characterized in that: The following steps are involved: (1) Take an aluminum source and add nitric acid, react for 0.5 to 5 hours in a dark environment, then add a calcium source and hydrogen peroxide, and then dry, grind and sieve to obtain a precursor; (2) calcining the obtained precursor, and then grinding and screening to obtain the target product; In step (1), the concentration of the nitric acid is 0.1 to 10 mol / L, and the concentration of the hydrogen peroxide is 10wt% to 50wt%; In step (1), the molar ratio of nitric acid to aluminum is (0.5 to 5):1, the molar ratio of calcium in the calcium source to hydrogen peroxide in hydrogen peroxide is (0.5 to 5):1, and the molar ratio of calcium to aluminum in the calcium source and aluminum source is (1 to 5):1; In step (2), calcination is carried out in an air atmosphere, the calcination temperature is 600 to 1200°C, the calcination constant temperature time is 0.5 to 4 h, and the calcination heating rate is 1 to 10°C / min; The chlorine remover has a solid worm-like structure.

2. The method for preparing a calcium aluminum-based bimetallic oxide dechlorinating agent according to claim 1, characterized in that: In step (1), the aluminum source includes aluminum oxide, aluminum hydroxide or pseudo-boehmite; In step (1), the calcium source includes calcium carbonate, calcium oxide or calcium hydroxide.

3. The method for preparing a calcium aluminum-based bimetallic oxide dechlorinating agent according to claim 1, characterized in that: In step (1), the drying temperature is 20 to 150°C; In step (1), the ground product is sieved using a 100-mesh sieve to obtain the precursor.

4. The method for preparing a calcium aluminum-based bimetallic oxide dechlorinating agent according to claim 1, characterized in that: In step (2), the ground product is sieved using a 100-mesh sieve to obtain the target product.

5. A calcium-aluminum-based bimetallic oxide dechlorinator, characterized in that: The dechlorinating agent is prepared by the preparation method according to any one of claims 1 to 4.

6. The use of a calcium aluminum-based bimetallic oxide dechlorinating agent as claimed in claim 5, characterized in that: The dechlorinator is used to remove chloride ions. The specific process includes: Weigh the dechlorination agent and add Cl - The reaction is carried out in the wastewater.

7. The use of a calcium aluminum-based bimetallic oxide dechlorinating agent according to claim 6, characterized in that: The reaction time is 3 to 12 hours; The reaction temperature is 10~65℃; Contains Cl - The pH of wastewater is 3 to 11; Contains Cl - Wastewater contains Ca 2+ Mg 2+ Or Na + .

Images