Process for the recycling of chlorine from a chlorine-containing wastewater

Abstract

The application belongs to the technical field of wastewater treatment, and discloses a circulating dechlorination process of chlorine-containing wastewater. The circulating dechlorination process of chlorine-containing wastewater is simple to operate, and only two steps are needed to obtain clean water meeting the standard, greatly simplifying the processing steps. The circulating dechlorination process of chlorine-containing wastewater finally obtains clean water and sodium chloride, and the sodium chloride can be sold as a chemical product, without generating other pollutants and causing environmental pollution. The final ion removal rate of the circulating dechlorination process of chlorine-containing wastewater can reach more than 97%, the removal rate is high, and the treatment effect is excellent. The circulating dechlorination process of chlorine-containing wastewater can realize the treatment of high-concentration chlorine-containing wastewater, and the chloride ion adsorbent can be reused after activation. After multiple cycle treatments, the removal rate of chloride ions still reaches more than 96.5%, and the stability is high.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wastewater treatment, and particularly relates to a circulating dechlorination process for chlorinated wastewater. BACKGROUND

[0002] With the development of industry, agriculture, medical treatment, life and other aspects, the problem of wastewater pollution is becoming increasingly serious. A large amount of chlorides are contained in wastewater, and if the wastewater is directly discharged or discharged without treatment into natural water bodies, it will have adverse effects on the ecological environment and human health. High-concentration chloride ions in wastewater have great harm, and if high-concentration chlorinated wastewater is directly discharged into rivers, it will cause water quality deterioration, fishery production and aquaculture reduction, and also cause damage to freshwater resources. Chloride ions can also corrode metal pipes such as steel, reduce the durability of the pipes, and shorten the service life. High concentration of chloride ions in water can also harm humans and animals.

[0003] At present, the main methods for treating chlorinated wastewater include adsorption, chemical precipitation, electrochemical technology, ion exchange and filter membrane separation. The adsorption effect of the adsorbent used in the adsorption method for treating chlorinated wastewater is poor, and the number of adsorption needs to be increased, which greatly increases the workload. Moreover, the existing adsorbent has poor stability and short service life. The chemical precipitation method has the problems of low removal rate and large amount of reagent addition, and is simple to operate and has large treatment capacity. Moreover, the chemical precipitation method finally produces a large amount of sludge, which needs to be treated, increasing the workload and energy consumption. The electrochemical technology has the problems of small treatment capacity and the production of chlorine gas, which needs to be treated. The ion exchange method and the filter membrane separation method are not suitable for high-concentration chlorinated wastewater, and the service life of the membrane used in the filter membrane separation method is short and is easily affected by the external environment.

[0004] At the same time, in the current methods for treating chlorinated wastewater, the reagents used cannot be recycled, which easily causes waste of resources and also produces by-products that affect the environment. Therefore, there is an urgent need in the field to develop a circulating dechlorination process for chlorinated wastewater, which has excellent dechlorination effect, is simple to operate, has large treatment capacity, can treat high-concentration chlorinated wastewater, and does not produce pollutants. SUMMARY

[0005] The present application provides a circulating dechlorination process for chlorinated wastewater to solve the problems of poor dechlorination effect, complex operation, production of other pollutants and inability to meet the treatment of high-concentration chlorinated wastewater in the existing process for treating chlorinated wastewater.

[0006] In order to achieve the above-mentioned purpose, the present application adopts the following technical scheme:

[0007] The present application provides a circulating dechlorination process for chlorinated wastewater, which comprises the following steps:

[0008] (1) passing the chlorine-containing wastewater and the chlorine ion adsorbent into the first treatment tank through the chlorine-containing wastewater storage tank and the chlorine ion adsorbent storage tank to mix, to obtain the first treatment wastewater and the first treatment chlorine ion adsorbent;

[0009] (2) passing the first treatment chlorine ion adsorbent and the sodium carbonate solution into the first recovery tank to mix and then calcining, to obtain the first recovery chlorine ion adsorbent; passing the first treatment wastewater and the first recovery chlorine ion adsorbent into the second treatment tank to mix, to obtain the clean water and the second treatment chlorine ion adsorbent;

[0010] (3) passing the second treatment chlorine ion adsorbent and the sodium carbonate solution into the second recovery tank to mix and then calcining, to obtain the second recovery chlorine ion adsorbent; returning the second recovery chlorine ion adsorbent to the chlorine ion adsorbent storage tank to recycle;

[0011] The preparation of the chlorine ion adsorbent comprises the following mass fractions of raw materials: 40-60 parts of the modified zinc-aluminum-magnesium hydrotalcite and 10-25 parts of the biomass.

[0012] As preferred, the preparation of the modified zinc-aluminum-magnesium hydrotalcite comprises the following steps:

[0013] a. mixing the zinc salt, the aluminum salt, the magnesium salt and water to obtain a first solution; mixing the sodium hydroxide solution, the sodium carbonate and water to obtain a second solution; dropping the first solution into the second solution, and performing crystallization treatment after the dropping is completed, to obtain the zinc-aluminum-magnesium hydrotalcite;

[0014] b. mixing the zinc-aluminum-magnesium hydrotalcite and the isocyanate and then performing heat treatment, to obtain the modified zinc-aluminum-magnesium hydrotalcite.

[0015] As preferred, in the first solution of the step a, the zinc salt is zinc chloride and / or zinc nitrate; the aluminum salt is one or more of aluminum chloride, aluminum nitrate and aluminum sulfate; the magnesium salt is magnesium chloride and / or magnesium nitrate; the molar ratio of the zinc salt, the aluminum salt and the magnesium salt is 1-3:1-2:1; the molar volume ratio of the magnesium salt and water is 0.01 mol:30-50 mL; in the second solution of the step a, the molar volume ratio of the sodium hydroxide solution, the sodium carbonate and water is 10-30 mL:0.01-0.03 mol:20-30 mL; in the step a, the molar ratio of the magnesium salt and the sodium carbonate is 1:1-3.

[0016] As preferred, in the step a, the dropping temperature is 30-40℃, and the dropping completion time is 1.5-2.5 h; the crystallization treatment temperature is 80-90℃, and the crystallization treatment time is 8-10 h.

[0017] As preferred, in the step b, the isocyanate is one or more of toluene diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, diphenylmethane diisocyanate and isophorone diisocyanate; the mass ratio of the zinc-aluminum-magnesium hydrotalcite-like compound and the isocyanate is 1-3:5-8; the heat treatment is carried out under a protective atmosphere, the temperature of the heat treatment is 70-80℃, and the time of the heat treatment is 5-8h.

[0018] As preferred, the preparation of the chloride ion adsorbent comprises the following steps:

[0019] The modified zinc-aluminum-magnesium hydrotalcite-like compound and the biomass are calcined to obtain the chloride ion adsorbent.

[0020] As preferred, the biomass is one or more of straw, rice husk and peanut shell; the temperature of the calcination is 500-600℃, the heating rate of the calcination is 2-5℃ / min, and the holding time of the calcination is 1-3h.

[0021] As preferred, the solid-liquid ratio in the first treatment tank and the second treatment tank is independently 0.1-0.25g:1L.

[0022] As preferred, in the steps (2) and (3), the concentration of the sodium carbonate solution is independently 0.05-0.1mol / L; the temperature of the calcination is 500-600℃, and the time of the calcination is 4-6h.

[0023] As preferred, in the first recovery tank and the second recovery tank, sodium chloride and clean water are independently obtained after mixing, and the sodium chloride is sold as a chemical product.

[0024] From the above technical solution, compared with the prior art, the present application has the following advantages:

[0025] (1) The circulating dechlorination process of the chloride-containing wastewater of the present application is simple in operation, and only two steps are needed to obtain clean water meeting the standard, greatly simplifying the processing steps; the circulating dechlorination process of the chloride-containing wastewater finally obtains clean water and sodium chloride, and the sodium chloride can be sold as a chemical product, without generating other pollutants, and without causing pollution to the environment; the final ion removal rate of the circulating dechlorination process of the chloride-containing wastewater can reach more than 97%, with high removal rate and excellent treatment effect; the circulating dechlorination process of the chloride-containing wastewater can realize the treatment of high-concentration chloride-containing wastewater, and the chloride ion adsorbent can be reused after activation, and the removal rate of chloride ions still reaches more than 96.5% after multiple cycle treatments, with high stability;

[0026] (2) The chloride ion adsorbent used in the application comprises modified zinc-aluminum-magnesium hydrotalcite and biomass. The modified zinc-aluminum-magnesium hydrotalcite contains abundant isocyanate groups on the surface after modification by isocyanate. The biomass contains a large number of active groups such as hydroxyl groups, carboxyl groups, amino groups and mercaptan groups on the surface. The isocyanate groups can combine with hydrogen groups and carboxyl groups, thereby improving the composite strength of the biomass and the modified zinc-aluminum-magnesium hydrotalcite. The modified zinc-aluminum-magnesium hydrotalcite and the biomass can significantly improve the adsorption of chloride ions and the removal rate of chloride ions by virtue of their unique structures and the active groups contained therein. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed in the following embodiment or prior art description will be briefly introduced. Obviously, the drawings in the following description are only embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative effort on the basis of the provided drawings.

[0028] Figure 1 Flow chart of the circulating dechlorination process of the chlorinated wastewater. DETAILED DESCRIPTION

[0029] The present application provides a circulating dechlorination process of chlorinated wastewater, comprising the following steps:

[0030] (1) The chlorinated wastewater and the chloride ion adsorbent are mixed in the first-stage treatment tank through the chlorinated wastewater storage tank and the chloride ion adsorbent storage tank, to obtain first-stage treated wastewater and first-stage treated chloride ion adsorbent;

[0031] (2) The first-stage treated chloride ion adsorbent and the sodium carbonate solution are mixed in the first-stage recovery tank and then calcined, to obtain first-stage recovered chloride ion adsorbent; the first-stage treated wastewater and the first-stage recovered chloride ion adsorbent are mixed in the second-stage treatment tank, to obtain clean water and second-stage treated chloride ion adsorbent;

[0032] (3) The second-stage treated chloride ion adsorbent and the sodium carbonate solution are mixed in the second-stage recovery tank and then calcined, to obtain second-stage recovered chloride ion adsorbent; the second-stage recovered chloride ion adsorbent is returned to the chloride ion adsorbent storage tank for circulation;

[0033] The preparation of the chloride ion adsorbent comprises the following raw materials in mass fraction: 40-60 parts of modified zinc-aluminum-magnesium hydrotalcite and 10-25 parts of biomass.

[0034] In the chloride ion adsorbent described in the present application, the amount of the modified zinc-aluminum-magnesium hydrotalcite is preferably 45-55 parts, and further preferably 46-50 parts; the amount of the biomass is preferably 15-20 parts, and further preferably 16-18 parts.

[0035] In the present application, the preparation of the modified zinc-aluminum-magnesium hydrotalcite-like compound comprises the following steps:

[0036] a. mixing zinc salt, aluminum salt, magnesium salt and water to obtain a first solution; mixing sodium hydroxide solution, sodium carbonate and water to obtain a second solution; adding the first solution into the second solution dropwise, and then performing crystallization treatment to obtain a zinc-aluminum-magnesium hydrotalcite-like compound;

[0037] b. mixing the zinc-aluminum-magnesium hydrotalcite-like compound and isocyanate, and then performing heat treatment to obtain a modified zinc-aluminum-magnesium hydrotalcite-like compound.

[0038] In the first solution of step a, the zinc salt is zinc chloride and / or zinc nitrate; the aluminum salt is one or more of aluminum chloride, aluminum nitrate and aluminum sulfate; the magnesium salt is magnesium chloride and / or magnesium nitrate; the molar ratio of the zinc salt, the aluminum salt and the magnesium salt is preferably 1-3:1-2:1, and further preferably 1.5-2:1.2-1.5:1; the molar volume ratio of the magnesium salt and water is preferably 0.01 mol:30-50 mL, and further preferably 0.01 mol:40-45 mL; in the second solution of step a, the mass fraction of the sodium hydroxide solution is preferably 30-60%, and further preferably 40-50%; the molar volume ratio of the sodium hydroxide solution, the sodium carbonate and water is preferably 10-30 mL:0.01-0.03 mol:20-30 mL, and further preferably 20-25 mL:0.02 mol:22-25 mL; the molar ratio of the magnesium salt and the sodium carbonate is preferably 1:1-3, and further preferably 1:2-2.5.

[0039] In step a, the temperature of the dropwise addition is preferably 30-40℃, and further preferably 32-35℃; the time for the completion of the dropwise addition is preferably 1.5-2.5 h, and further preferably 120-130 min; the temperature of the crystallization treatment is preferably 80-90℃, and further preferably 82-85℃; the time of the crystallization treatment is preferably 8-10 h, and further preferably 8.5-9 h.

[0040] In step a, the specific steps of adding the first solution into the second solution are as follows: stirring the second solution, and adding the first solution dropwise into the stirred second solution; the stirring speed is preferably 200-400 r / min, and further preferably 300-350 r / min.

[0041] In step a, after the crystallization treatment, the obtained product is sequentially subjected to suction filtration, washing and drying; the reagent used for washing is water; the temperature of the drying is preferably 60-70℃, and further preferably 62-65℃; the time of the drying is preferably 8-10 h, and further preferably 9-9.5 h.

[0042] In step b of the present application, the isocyanate is one or more of toluene diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, diphenylmethane diisocyanate and isophorone diisocyanate; the mass ratio of the zinc-aluminum-magnesium hydrotalcite-like compound and the isocyanate is preferably 1-3:5-8, further preferably 2-2.5:6-7; the heat treatment is carried out under a protective atmosphere, the protective atmosphere being helium; the temperature of the heat treatment is preferably 70-80℃, further preferably 75-78℃; the time of the heat treatment is preferably 5-8h, further preferably 6-7h.

[0043] In the present application, the preparation of the chloride ion adsorbent comprises the following steps:

[0044] The modified zinc-aluminum-magnesium hydrotalcite-like compound and the biomass are calcined to obtain the chloride ion adsorbent.

[0045] In the present application, the biomass is one or more of straw, rice husk and peanut shell; when the biomass is straw, the diameter of the biomass is preferably 4-6mm, further preferably 5mm; the length of the biomass is preferably 10-15mm, further preferably 12-14mm; when the biomass is rice husk and peanut shell, the particle size of the biomass is preferably 100-300 mesh, further preferably 150-200 mesh; the particle size of the modified zinc-aluminum-magnesium hydrotalcite-like compound is preferably 200-400 mesh, further preferably 300-350 mesh.

[0046] In the present application, the temperature of the calcination is preferably 500-600℃, further preferably 550-580℃; the heating rate of the calcination is preferably 2-5℃ / min, further preferably 3-4℃ / min; the holding time of the calcination is preferably 1-3h, further preferably 2-2.5h.

[0047] In the present application, the particle size of the chloride ion adsorbent is preferably 200-400 mesh, further preferably 300-350 mesh.

[0048] In the present application, the solid-liquid ratio in the primary treatment tank and the secondary treatment tank is independently preferably 0.1-0.25g:1L, further preferably 0.2-0.23g:1L.

[0049] In steps (2) and (3) of the present application, the concentration of the sodium carbonate solution is independently preferably 0.05-0.1mol / L, further preferably 0.06-0.08mol / L; the temperature of the calcination is preferably 500-600℃, further preferably 550-580℃; the time of the calcination is preferably 4-6h, further preferably 5-5.5h.

[0050] In the primary recovery tank and the secondary recovery tank of the application, sodium chloride and clean water are obtained independently after mixing, and the sodium chloride is sold as a chemical product.

[0051] The technical solutions provided by the application are described in detail below in combination with examples, but they should not be understood as limiting the protection scope of the application.

[0052] Example 1

[0053] Preparation of the chloride ion adsorbent:

[0054] (1) 0.06 mol of zinc chloride, 0.02 mol of aluminum nitrate, 0.02 mol of magnesium chloride and 60 mL of distilled water were mixed to obtain a first solution; 30 mL of a sodium hydroxide solution (mass fraction of 40%), 0.01 mol of sodium carbonate and 25 mL of water were mixed to obtain a second solution; the second solution was stirred at a temperature of 30℃ and a stirring speed of 300 r / min, and the first solution was added dropwise into the second solution, and the dropwise addition was completed in 2 h; the obtained product was subjected to crystallization treatment at 90℃ for 8 h; the obtained product was subjected to suction filtration, washed with boiling distilled water and dried at 60℃ for 8 h, and then crushed and sieved to obtain zinc-aluminum-magnesium-like hydrotalcite with a particle size of 500 mesh; 30 g of the zinc-aluminum-magnesium-like hydrotalcite and 80 g of toluene diisocyanate were mixed, and then subjected to heat treatment under the protection of helium at 80℃ for 8 h, and then crushed and sieved to obtain modified zinc-aluminum-magnesium-like hydrotalcite with a particle size of 300 mesh;

[0055] (2) 55 g of the modified zinc-aluminum-magnesium-like hydrotalcite and 15 g of wheat straw (diameter of 5 mm and length of 12.5 mm) were mixed and placed in a reaction kettle, and then heated to 550℃ at a heating rate of 5℃ / min and kept for 3 h, and then crushed and sieved to obtain chloride ion adsorbent with a particle size of 350 mesh.

[0056] Example 2

[0057] Preparation of the chloride ion adsorbent:

[0058] (1) mixed 0.08 mol of zinc chloride, 0.08 mol of aluminum chloride, 0.04 mol of magnesium chloride and 120 mL of distilled water to obtain a first solution; mixed 40 mL of a sodium hydroxide solution (40% by mass), 0.04 mol of sodium carbonate and 80 mL of water to obtain a second solution; stirred the second solution at a temperature of 30°C and a stirring speed of 300 r / min, and added the first solution dropwise into the second solution, which was completed in 2.5 h; crystallized the obtained product at 85°C for 8 h; performed suction filtration on the obtained product, washed with boiling distilled water, dried at 60°C for 8 h, and pulverized and sieved to obtain zinc-aluminum-magnesium-like hydrotalcite with a particle size of 450 mesh; mixed 40 g of the zinc-aluminum-magnesium-like hydrotalcite with 100 g of diphenylmethane diisocyanate, and performed heat treatment under helium protection at 80°C for 7 h, and pulverized and sieved to obtain modified zinc-aluminum-magnesium-like hydrotalcite with a particle size of 300 mesh;

[0059] (2) mixed 50 g of the modified zinc-aluminum-magnesium-like hydrotalcite with 15 g of corn stalks (4 mm in diameter and 10 mm in length) in a reaction kettle, heated to 580°C at a temperature increasing rate of 4°C / min, and maintained at the temperature for 2 h, and pulverized and sieved to obtain a chlorine ion adsorbent with a particle size of 300 mesh.

[0060] Example 3

[0061] Preparation of a chlorine ion adsorbent:

[0062] (1) mixed 0.04 mol of zinc nitrate, 0.04 mol of aluminum chloride, 0.04 mol of magnesium chloride and 120 mL of distilled water to obtain a first solution; mixed 80 mL of a sodium hydroxide solution (40% by mass), 0.04 mol of sodium carbonate and 80 mL of water to obtain a second solution; stirred the second solution at a temperature of 32°C and a stirring speed of 300 r / min, and added the first solution dropwise into the second solution, which was completed in 1.5 h; crystallized the obtained product at 85°C for 8.5 h; performed suction filtration on the obtained product, washed with boiling distilled water, dried at 60°C for 8 h, and pulverized and sieved to obtain zinc-aluminum-magnesium-like hydrotalcite with a particle size of 400 mesh; mixed 60 g of the zinc-aluminum-magnesium-like hydrotalcite with 100 g of hexamethylene diisocyanate, and performed heat treatment under helium protection at 80°C for 7 h, and pulverized and sieved to obtain modified zinc-aluminum-magnesium-like hydrotalcite with a particle size of 300 mesh;

[0063] (2) mixed 55 g of the modified zinc-aluminum-magnesium-like hydrotalcite with 18 g of rice husks (200 mesh in particle size) in a reaction kettle, heated to 600°C at a temperature increasing rate of 3°C / min, and maintained at the temperature for 2.5 h, and pulverized and sieved to obtain a chlorine ion adsorbent with a particle size of 300 mesh.

[0064] Example 4

[0065] The chlorine-containing wastewater was taken from a power plant in Jinan city, and the concentration of chloride ion was 10896 mg / L after detection;

[0066] (1) The chlorine-containing wastewater and the chloride ion adsorbent obtained in Example 1 were mixed by passing them into the first treatment tank through the chlorine-containing wastewater storage tank and the chloride ion adsorbent storage tank (controlling the solid-liquid ratio to be 0.1 g: 1 L), and then separated to obtain the first treatment wastewater and the first treatment chloride ion adsorbent;

[0067] (2) The first treatment chloride ion adsorbent and the 0.05 mol / L sodium carbonate solution were mixed by passing them into the first recovery tank (the sodium carbonate solution immersed the first treatment chloride ion adsorbent), and then the solid-liquid separation was carried out after standing; the solid was calcined at 500℃ for 5h to obtain the first recovered chloride ion adsorbent; the liquid was distilled to obtain sodium chloride and clean water;

[0068] (3) The first treatment wastewater and the first recovered chloride ion adsorbent were mixed by passing them into the second treatment tank (controlling the solid-liquid ratio to be 0.2 g: 1 L), and then separated to obtain clean water and the second treatment chloride ion adsorbent;

[0069] (4) The second treatment chloride ion adsorbent and the 0.06 mol / L sodium carbonate solution were mixed by passing them into the second recovery tank (the sodium carbonate solution immersed the second treatment chloride ion adsorbent), and then the solid-liquid separation was carried out after standing; the solid was calcined at 500℃ for 6h to obtain the second recovered chloride ion adsorbent; the liquid was distilled to obtain sodium chloride and clean water; the second recovered chloride ion adsorbent was returned to the chloride ion adsorbent storage tank for recycling.

[0070] Detection of chloride ion removal rate:

[0071] The clean water obtained above was mixed and then tested for chloride ion content. The removal rate of chloride ion by the method described in this example was 97.2% after detection.

[0072] Stability detection:

[0073] The second recovered chloride ion adsorbent was returned to the chloride ion adsorbent storage tank, steps (1)-(4) were repeated 5 times, and the chloride ion content of the clean water obtained was detected respectively. The removal rates of chloride ion in the first, second, third, fourth and fifth times were 97.2%, 97.1%, 97.1%, 96.8% and 96.5% respectively after detection.

[0074] Example 5

[0075] The chlorine-containing wastewater was taken from a chemical plant in Jinan city, and the concentration of chloride ion was 35687 mg / L after detection;

[0076] (1) the chlorine-containing wastewater and the chlorine ion adsorbent obtained in Example 2 were mixed by passing them into a first treatment tank through a chlorine-containing wastewater storage tank and a chlorine ion adsorbent storage tank (controlling the solid-liquid ratio to be 0.2 g: 1 L), and then separated by standing;

[0077] (2) the first treatment chlorine ion adsorbent and a 0.05 mol / L sodium carbonate solution were mixed by passing them into a first recovery tank (the sodium carbonate solution immersed the first treatment chlorine ion adsorbent), and then separated by standing and solid-liquid separation; the solid was calcined at 550℃ for 5 h to obtain a first recovered chlorine ion adsorbent; the liquid was distilled to obtain sodium chloride and clean water;

[0078] (3) the first treatment wastewater and the first recovered chlorine ion adsorbent were mixed by passing them into a second treatment tank (controlling the solid-liquid ratio to be 0.23 g: 1 L), and then separated by standing to obtain clean water and a second treatment chlorine ion adsorbent;

[0079] (4) the second treatment chlorine ion adsorbent and a 0.05 mol / L sodium carbonate solution were mixed by passing them into a second recovery tank (the sodium carbonate solution immersed the second treatment chlorine ion adsorbent), and then separated by standing and solid-liquid separation; the solid was calcined at 550℃ for 6 h to obtain a second recovered chlorine ion adsorbent; the liquid was distilled to obtain sodium chloride and clean water; the second recovered chlorine ion adsorbent was returned to the chlorine ion adsorbent storage tank for recycling.

[0080] Detection of chlorine ion removal rate:

[0081] The clean water obtained above was mixed and then tested for chlorine ion content. It was detected that the removal rate of chlorine ion by the method described in the present embodiment was 97%.

[0082] Detection of stability:

[0083] The second recovered chlorine ion adsorbent was returned to the chlorine ion adsorbent storage tank, steps (1)-(4) were repeated for 5 times, and the chlorine ion content of the clean water obtained was detected respectively. It was detected that the removal rates of chlorine ion in the first time, the second time, the third time, the fourth time and the fifth time were 97%, 97%, 96.9%, 96.8% and 96.6% respectively.

[0084] Example 6

[0085] Chlorine-containing wastewater generated by a research institute in Jinan was taken, and it was detected that the chlorine ion concentration was 8941 mg / L;

[0086] (1) the chlorine-containing wastewater and the chlorine ion adsorbent obtained in Example 3 were mixed by passing them into a first treatment tank through a chlorine-containing wastewater storage tank and a chlorine ion adsorbent storage tank (controlling the solid-liquid ratio to be 0.23 g: 1 L), and then separated by standing;

[0087] (2) the primary treated chloride ion adsorbent and 0.05 mol / L sodium carbonate solution are mixed in a primary recovery tank (the sodium carbonate solution immerses the primary treated chloride ion adsorbent), and then solid-liquid separation is carried out after standing; the solid is calcined at 600℃ for 5h to obtain a primary recovered chloride ion adsorbent; the liquid is distilled to obtain sodium chloride and clean water;

[0088] (3) the primary treated wastewater and the primary recovered chloride ion adsorbent are mixed in a secondary treatment tank (the solid-liquid ratio is controlled to be 0.25g:1L), and then clean water and secondary treated chloride ion adsorbent are obtained after standing and separation;

[0089] (4) the secondary treated chloride ion adsorbent and 0.05 mol / L sodium carbonate solution are mixed in a secondary recovery tank (the sodium carbonate solution immerses the secondary treated chloride ion adsorbent), and then solid-liquid separation is carried out after standing; the solid is calcined at 500℃ for 5.5h to obtain a secondary recovered chloride ion adsorbent; the liquid is distilled to obtain sodium chloride and clean water; the secondary recovered chloride ion adsorbent is returned to the chloride ion adsorbent storage tank for recycling.

[0090] Detection of chloride ion removal rate:

[0091] The clean water obtained above is mixed and then tested for chloride ion content. The detection shows that the removal rate of chloride ion by the method described in the embodiment is 98.1%.

[0092] Detection of stability:

[0093] The secondary recovered chloride ion adsorbent is returned to the chloride ion adsorbent storage tank, and steps (1) to (4) are repeated for 5 times, and the chloride ion content of the clean water obtained is detected. The detection shows that the removal rates of chloride ion in the first time, the second time, the third time, the fourth time and the fifth time are 98.1%, 98.1%, 97.8%, 97.6% and 97.6%, respectively.

[0094] The above only describes the preferred embodiments of the present application, and it should be noted that those skilled in the art can make several improvements and refinements without departing from the principles of the present application, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A process for the cyclic dechlorination of chlorinated wastewater, characterized in that, The method comprises the following steps: (1) passing the chlorine-containing wastewater in a chlorine-containing wastewater storage tank and the chlorine ion adsorbent in a chlorine ion adsorbent storage tank into a first-stage treatment tank to mix, to obtain first-stage treatment wastewater and first-stage treatment chlorine ion adsorbent; (2) passing the first-stage treatment chlorine ion adsorbent and a sodium carbonate solution into a first-stage recovery tank to mix, then performing solid-liquid separation, calcining the solid, to obtain first-stage recovered chlorine ion adsorbent; passing the first-stage treatment wastewater and the first-stage recovered chlorine ion adsorbent into a second-stage treatment tank to mix, to obtain clean water and second-stage treatment chlorine ion adsorbent; (3) passing the second-stage treatment chlorine ion adsorbent and a sodium carbonate solution into a second-stage recovery tank to mix, then performing solid-liquid separation, calcining the solid, to obtain second-stage recovered chlorine ion adsorbent; returning the second-stage recovered chlorine ion adsorbent to the chlorine ion adsorbent storage tank to recycle; The preparation of the chlorine ion adsorbent comprises the following raw materials in mass fraction: 40-60 parts of modified zinc-aluminum-magnesium hydrotalcite and 10-25 parts of biomass; The preparation of the modified zinc-aluminum-magnesium hydrotalcite comprises the following steps: a. mixing zinc salt, aluminum salt, magnesium salt and water to obtain a first solution; mixing sodium hydroxide solution, sodium carbonate and water to obtain a second solution; dropping the first solution into the second solution, and performing crystallization treatment after dropping is completed, to obtain zinc-aluminum-magnesium hydrotalcite; b. mixing the zinc-aluminum-magnesium hydrotalcite and isocyanate, and then performing heat treatment, to obtain modified zinc-aluminum-magnesium hydrotalcite; In step b, the isocyanate is one or more of toluene diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, diphenylmethane diisocyanate and isophorone diisocyanate; the mass ratio of the zinc-aluminum-magnesium hydrotalcite and the isocyanate is 1-3:5-8; the heat treatment is performed in a protective atmosphere, the temperature of the heat treatment is 70-80℃, and the time of the heat treatment is 5-8h; The preparation of the chlorine ion adsorbent comprises the following steps: roasting the modified zinc-aluminum-magnesium hydrotalcite and the biomass, to obtain the chlorine ion adsorbent.

2. The process for the dechlorination of chlorinated wastewater according to claim 1, wherein In the first solution of step a, the zinc salt is zinc chloride and / or zinc nitrate; the aluminum salt is one or more of aluminum chloride, aluminum nitrate and aluminum sulfate; the magnesium salt is magnesium chloride and / or magnesium nitrate; the molar ratio of the zinc salt, the aluminum salt and the magnesium salt is 1-3:1-2:1; the molar volume ratio of the magnesium salt and water is 0.01 mol:30-50mL; in the second solution of step a, the molar volume ratio of the sodium hydroxide solution, the sodium carbonate and water is 10-30mL:0.01-0.03mol:20-30mL; in step a, the molar ratio of the magnesium salt and the sodium carbonate is 1:1-3.

3. The process for the dechlorination of chlorinated wastewater according to claim 2, wherein In step a, the dropping temperature is 30-40℃, the time of completing dropping is 1.5-2.5h; the crystallization treatment temperature is 80-90℃, and the crystallization treatment time is 8-10h.

4. The process for the dechlorination of chlorinated wastewater according to claim 3, wherein The biomass is one or more of straw, rice husk and peanut shell; the roasting temperature is 500-600℃, the heating rate of roasting is 2-5℃ / min, and the holding time of roasting is 1-3h.

5. The process for the dechlorination of chlorinated wastewater according to claim 1, wherein The solid-liquid ratio in the first and second treatment tanks is independently 0.1-0.25 g:1 L.

6. The process for the dechlorination of chlorinated wastewater according to claim 1, wherein In the steps (2) and (3), the concentration of the sodium carbonate solution is independently 0.05-0.1 mol / L; the calcination temperature is 500-600 ℃, and the calcination time is 4-6 h.

7. The process for the dechlorination of chlorinated wastewater according to claim 6, wherein The liquid separated from the solid in the steps (2) and (3) is distilled to obtain sodium chloride and clean water, and the sodium chloride is sold as a chemical product.

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