Purification method of perchlorate wastewater

Abstract

The invention discloses a method for purifying perchlorate wastewater, which comprises adding a ferrous agent to high-concentration perchlorate wastewater, then adding a reducing agent to carry out stirring reaction, adjusting the pH value to 1-4 after the reaction to continue the reaction, obtaining a reduced liquid, adjusting the pH value of the reduced liquid to 6-10, filtering, obtaining a first filtrate and a first filter residue, filtering low-concentration perchlorate wastewater to obtain a second filtrate and a second filter residue, mixing the first filtrate and the second filtrate, adsorbing with an ion exchange resin, obtaining a treated liquid, wherein the concentration of perchlorate in the treated liquid is less than 0.07 mg / L, and the purification treatment is completed. The method of the invention can treat a wide range of perchlorate concentrations, has a good treatment effect, can stably meet the standards at a low cost, has no secondary pollution, is simple to regenerate the resin, and can realize the recycling of the agent.

Description

Technical Field

[0001] The invention relates to the field of perchlorate wastewater treatment, and in particular to a method for purifying perchlorate wastewater. Background Art

[0002] Perchlorate is a new type of trace pollutant with high stability, water solubility and oxidizability. It can disrupt the normal metabolism of the human body and affect normal human growth and development. On March 15, 2022, the State Administration for Market Regulation and the National Standardization Administration jointly approved the release of GB 5749-2022 "Sanitary Standards for Drinking Water", which will be implemented from April 1, 2023. According to the extended indicators and limit requirements for drinking water quality in the standard, perchlorate is ≤0.07mg / L. At present, the main technologies used for the removal and pollution remediation of perchlorate at home and abroad are: anion exchange and adsorbent adsorption, chemical reduction, biochemical method, membrane separation technology, etc. For the existing treatment technologies of perchlorate, membrane separation and ion exchange methods are feasible, but the disadvantages are difficult regeneration, relatively high equipment costs, high treatment costs, and difficulty in treating perchlorate concentrated water. The chemical reduction method has a slow reaction speed, harsh reaction conditions and too high a cost. The biochemical method has a low treatment cost and has a good development prospect, but it is difficult to screen strains, the effect is unstable, the treatment speed is slow, and it occupies a large area. Therefore, it is urgent to solve the above technical problems, especially for high-concentration perchlorate wastewater, and study how to achieve the standards stably and at low cost. Summary of the invention

[0003] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a perchlorate wastewater purification method which has a wide applicable concentration, good treatment effect, can stably meet the standards at low cost and has no secondary pollution.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions.

[0005] A method for purifying perchlorate wastewater comprises the following steps:

[0006] (1) adding ferrous agent to high-concentration perchlorate wastewater, wherein the concentration of perchlorate in the high-concentration perchlorate wastewater is 300 mg / L to 2000 mg / L, then adding a reducing agent, stirring for reaction, adjusting the pH value to 1 to 4, continuing the reaction, and obtaining a reduced liquid after the reaction is completed;

[0007] (2) adjusting the pH value of the reduced solution to 6 to 10, filtering to obtain a first filtrate and a first filter residue; filtering the low-concentration perchlorate wastewater, wherein the concentration of perchlorate in the low-concentration perchlorate wastewater is 0.1 mg / L to 100 mg / L, to obtain a second filtrate and a second filter residue;

[0008] (3) The first filtrate and the second filtrate are mixed and adsorbed with an ion exchange resin to obtain a treated liquid, wherein the concentration of perchlorate in the treated liquid is less than 0.07 mg / L, thereby completing the purification treatment.

[0009] In the above-mentioned method for purifying perchlorate wastewater, preferably, in step (1), the ferrous agent is ferrous chloride and / or ferrous sulfate, and the amount of the ferrous agent added to the high-concentration perchlorate wastewater is 0.05 mol / L to 0.5 mol / L.

[0010] In the above-mentioned method for purifying perchlorate wastewater, preferably, in step (1), the reducing agent is one of hydrazine hydrate, potassium borohydride, sodium borohydride and aluminum powder; when the reducing agent is hydrazine hydrate, the stirring reaction is controlled at a pH value of 7 to 11 and a temperature of 40° C. to 95° C.; when the reducing agent is potassium borohydride or sodium borohydride, the stirring reaction is controlled at a pH value of 4 to 11; when the reducing agent is aluminum powder, the stirring reaction is controlled at a pH value of 4 to 7; the molar amount of the reducing agent is 5 to 30 times the molar amount of perchlorate in the high-concentration perchlorate wastewater.

[0011] In the above-mentioned method for purifying perchlorate wastewater, preferably, in step (1), the process of adding the reducing agent until the reaction is completed is repeated 1 to 5 times, and after the last reaction is completed, the pH is adjusted to 6 to 10.

[0012] In the above-mentioned method for purifying perchlorate wastewater, preferably, in step (1), the stirring reaction time is 1 hour to 6 hours, and the continued reaction time is 1 hour to 6 hours.

[0013] In the above-mentioned method for purifying perchlorate wastewater, preferably, in step (3), the ion exchange resin is an anion exchange resin, and the anion exchange resin includes a quaternary ammonium anion exchange resin, and the adsorption rate is 5BV / h to 20BV / h.

[0014] In the above-mentioned method for purifying perchlorate wastewater, preferably, in step (3), after the ion exchange resin is saturated with adsorption, it is eluted and regenerated with an eluent to obtain an eluted liquid, and the eluted liquid is returned to the high-concentration perchlorate wastewater reagent reduction process in step (1) for treatment.

[0015] In the above-mentioned method for purifying perchlorate wastewater, preferably, in step (3), the eluent is a mixed solution of 0.1mol / L to 1.5mol / L hydrochloric acid and 0.2mol / L to 5mol / L chloride salt or 2mol / L to 8mol / L hydrochloric acid; the chloride salt is one or more of sodium chloride, potassium chloride, ferrous chloride, ferric chloride, aluminum chloride and calcium chloride; after the elution regeneration, the ion exchange resin is washed with water and liquid alkali to a pH value of 6 to 10 and then recycled.

[0016] In the above-mentioned method for purifying perchlorate wastewater, preferably, in step (2), the first filter residue is dissolved with acid and then reused as a ferrous agent or used as an eluent, and the second filter residue is sent for external disposal; in step (3), the treated liquid effluent is discharged.

[0017] In perchlorate, the valence state of chlorine is +7.

[0018] Compared with the prior art, the advantages of the present invention are:

[0019] The method of the present invention can treat a wide range of perchlorate concentrations, and can particularly effectively treat high-concentration perchlorate wastewater with good treatment effects. The present invention can stabilize the perchlorate concentration in the wastewater to below 0.07 mg / L, and no high-concentration perchlorate concentrate is produced, thereby avoiding secondary pollution and secondary treatment. The resin used in the present invention is easy to regenerate, and the reagents are all conventional reagents, and the reagents can also be recycled. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a process flow chart of the method for purifying perchlorate wastewater in Example 1 of the present invention. DETAILED DESCRIPTION

[0021] The present invention is further described below in conjunction with the accompanying drawings and specific preferred embodiments, but the protection scope of the present invention is not limited thereby. The materials and instruments used in the following embodiments are all commercially available.

[0022] Example 1

[0023] The workshop production wastewater and circulating pool water of a certain fireworks company have the following composition as shown in Table 1.

[0024] Table 1 Raw water composition (mg / L, pH dimensionless)

[0025]

[0026] A method for purifying perchlorate wastewater of the present invention, as follows Figure 1 As shown, the following steps are included:

[0027] (1) Reagent reduction

[0028] (1.1) Take 2L of high-concentration perchlorate wastewater (workshop production wastewater, 1087mg / L is equivalent to 0.01mol / L), add 0.3mol of ferrous sulfate, and mix and dissolve;

[0029] (1.2) Slowly add 0.2 mol of hydrazine hydrate within 2 hours, control the temperature to 80°C, control the pH to 8.5-9.0, and stir to react. After reacting for 1 hour, add dilute sulfuric acid to adjust the pH to 2.5-3.0, stir and react for 2 hours to obtain the first reduced solution;

[0030] (1.3) Slowly add 0.12 mol of hydrazine hydrate to the first reduced solution within 2 hours, control the temperature to 80°C, control the pH to 8.5-9.0, react for 1 hour, adjust the pH to 2.5-3.0 with dilute sulfuric acid, stir and react for 2 hours to obtain the second reduced solution;

[0031] (1.4) Slowly add 0.06 mol of hydrazine hydrate to the second reduction solution within 2 hours, control the temperature to 80°C, control the pH to 8.5-9.0, react for 1 hour, adjust the pH to 2.5-3.0 with dilute sulfuric acid, stir and react for 2 hours to obtain the third reduction solution.

[0032] After testing, the composition of the liquid after the above three reductions is shown in Table 2 below.

[0033] Table 2 Result data table of the solution after three reductions in Example 1 (mg / L)

[0034]

[0035] (2) Filtering

[0036] The pH value of the liquid after the third reduction is adjusted to 9.5 with lime milk solution, and filtered with a 1 μm filter membrane to obtain the first filtrate and the first filter residue. The first filter residue can be used as ferrous sulfate in the reagent reduction process, or the first filter residue can be used in the resin elution process as the eluent.

[0037] The low-concentration perchlorate wastewater (circulating pool water) is filtered with a 1μm filter membrane to obtain a second filtrate and a second filter residue. The second filter residue is sent out for disposal.

[0038] (3) Resin adsorption

[0039] After mixing 10L of the second filtrate and 1L of the first filtrate, 11L of mixed adsorption stock solution was obtained. The 11L mixed adsorption stock solution was passed through a glass sand core adsorption column at a rate of 10BV / h, and the glass sand core adsorption column was loaded with 20g of macroporous quaternary ammonium anion exchange resin to obtain a treated liquid after adsorption. The perchlorate concentration in the treated liquid was 0.015mg / L after sampling and analysis.

[0040] In this embodiment, the first filter residue obtained in the filtering process is dissolved with dilute hydrochloric acid, filtered, and hydrochloric acid and ferrous chloride are added to the filtrate to prepare a mixed solution containing 0.5 mol / L hydrochloric acid and 1 mol / L ferrous chloride as an eluent. 300 mL of the eluent is passed through the glass sand core adsorption column after adsorption at a speed of 20 mL / h to obtain an eluted liquid. The perchlorate concentration in the eluted liquid after sampling and analysis is 682 mg / L, and the elution rate is 98.4%.

[0041] Example 2

[0042] A method for purifying perchlorate wastewater of the present invention is basically the same as that of Example 1, except that 6 mol / L hydrochloric acid is used as an eluent instead of a mixed solution containing 0.5 mol / L hydrochloric acid and 1 mol / L ferrous chloride, and the elution rate is 97.7%.

[0043] Comparative Example 1

[0044] The process is basically the same as Example 1, except that ferrous sulfate is not added in step (1.1) of Example 1, and the rest is completed as in Example 1. After testing, the composition of the liquid after three reductions is shown in Table 3 below.

[0045] Table 3 Comparative Example 1 Result Data Table of the Solution after Three Reductions (mg / L)

[0046]

[0047] Comparative Example 2

[0048] The process is basically the same as Example 1, except that hydrazine hydrate is not added in step (1.2) to step (1.4) in Example 1, and the rest is completed as in Example 1. After testing, the composition of the liquid after three reductions is shown in Table 4 below.

[0049] Table 4 Comparative Example 2 Result Data Table of the Solution after Three Reductions (mg / L)

[0050]

[0051] The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as above in the preferred embodiment, it is not used to limit the present invention. Any technician familiar with the art can make many possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention, still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for purifying perchlorate wastewater, It is characterized in that The following steps are involved: (1) adding a ferrous agent to high-concentration perchlorate wastewater, wherein the concentration of perchlorate in the high-concentration perchlorate wastewater is 300 mg / L to 2000 mg / L, and the amount of the ferrous agent added to the high-concentration perchlorate wastewater is 0.05 mol / L to 0.5 mol / L, then adding a reducing agent, stirring for reaction, adjusting the pH value to 1 to 4, continuing the reaction, and obtaining a reduced liquid after the reaction is completed; The reducing agent is one of hydrazine hydrate, potassium borohydride, sodium borohydride and aluminum powder; when the reducing agent is hydrazine hydrate, the stirring reaction is controlled at a pH value of 7 to 11 and a temperature of 40° C. to 95° C.; when the reducing agent is potassium borohydride or sodium borohydride, the stirring reaction is controlled at a pH value of 4 to 11; when the reducing agent is aluminum powder, the stirring reaction is controlled at a pH value of 4 to 7; (2) adjusting the pH value of the reduced solution to 6 to 10, filtering to obtain a first filtrate and a first filter residue; filtering the low-concentration perchlorate wastewater, wherein the concentration of perchlorate in the low-concentration perchlorate wastewater is 0.1 mg / L to 100 mg / L, to obtain a second filtrate and a second filter residue; (3) The first filtrate and the second filtrate are mixed and adsorbed with an ion exchange resin to obtain a treated liquid, wherein the concentration of perchlorate in the treated liquid is less than 0.07 mg / L, thereby completing the purification treatment.

2. The method for purifying perchlorate wastewater according to claim 1, It is characterized in that In step (1), the ferrous agent is ferrous chloride and / or ferrous sulfate.

3. The method for purifying perchlorate wastewater according to claim 1, It is characterized in that In step (1), the molar amount of the reducing agent is 5 to 30 times the molar amount of perchlorate in the high-concentration perchlorate wastewater.

4. The method for purifying perchlorate wastewater according to claim 1, It is characterized in that In step (1), the process of adding the reducing agent until the reaction is completed is repeated 1 to 5 times. After the last reaction is completed, the pH of the obtained reduced solution is adjusted to 6 to 10.

5. The method for purifying perchlorate wastewater according to any one of claims 1 to 4, It is characterized in that In step (1), the stirring reaction time is 1 h to 6 h, and the continued reaction time is 1 h to 6 h.

6. The method for purifying perchlorate wastewater according to any one of claims 1 to 4, It is characterized in that In step (3), the ion exchange resin is an anion exchange resin, and the anion exchange resin includes a quaternary ammonium anion exchange resin, and the adsorption rate is 5 BV / h to 20 BV / h.

7. The method for purifying perchlorate wastewater according to any one of claims 1 to 4, It is characterized in that In step (3), after the ion exchange resin is saturated with adsorption, it is eluted and regenerated with an eluent to obtain an eluted liquid, which is returned to the reagent reduction process of the high-concentration perchlorate wastewater in step (1) for treatment.

8. The method for purifying perchlorate wastewater according to claim 7, It is characterized in that In step (3), the eluent is a mixed solution of 0.1mol / L to 1.5mol / L hydrochloric acid and 0.2mol / L to 5mol / L chloride salt or 2mol / L to 8mol / L hydrochloric acid; the chloride salt is one or more of sodium chloride, potassium chloride, ferrous chloride, ferric chloride, aluminum chloride and calcium chloride; after the elution regeneration, the ion exchange resin is washed with water and liquid alkali to a pH value of 6 to 10 and then recycled.

9. The method for purifying perchlorate wastewater according to claim 7, It is characterized in that In step (2), the first filter residue is dissolved with acid and reused as ferrous reagent or used as eluent, and the second filter residue is sent for external disposal; in step (3), the treated liquid is discharged.

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