CN113371780A - Treatment method of wastewater containing low-concentration perfluorooctanoic acid - Google Patents
Treatment method of wastewater containing low-concentration perfluorooctanoic acid Download PDFInfo
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- CN113371780A CN113371780A CN202110654819.XA CN202110654819A CN113371780A CN 113371780 A CN113371780 A CN 113371780A CN 202110654819 A CN202110654819 A CN 202110654819A CN 113371780 A CN113371780 A CN 113371780A
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- SNGREZUHAYWORS-UHFFFAOYSA-N perfluorooctanoic acid Chemical compound OC(=O)C(F)(F)C(F)(F)C(F)(F)C(F)(F)C(F)(F)C(F)(F)C(F)(F)F SNGREZUHAYWORS-UHFFFAOYSA-N 0.000 title claims abstract description 87
- 239000002351 wastewater Substances 0.000 title claims abstract description 58
- 238000000034 method Methods 0.000 title claims abstract description 36
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 111
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims abstract description 70
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 claims abstract description 54
- 238000001179 sorption measurement Methods 0.000 claims abstract description 49
- 239000007788 liquid Substances 0.000 claims abstract description 48
- 238000011069 regeneration method Methods 0.000 claims abstract description 46
- 230000008929 regeneration Effects 0.000 claims abstract description 45
- 239000002699 waste material Substances 0.000 claims abstract description 41
- 239000011780 sodium chloride Substances 0.000 claims abstract description 27
- 239000012452 mother liquor Substances 0.000 claims abstract description 11
- 238000007254 oxidation reaction Methods 0.000 claims abstract description 11
- 238000001704 evaporation Methods 0.000 claims abstract description 10
- 230000008020 evaporation Effects 0.000 claims abstract description 10
- 230000003647 oxidation Effects 0.000 claims abstract description 9
- 239000003814 drug Substances 0.000 claims abstract description 8
- 229920006395 saturated elastomer Polymers 0.000 claims abstract description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 5
- 238000007599 discharging Methods 0.000 claims abstract description 4
- 230000001590 oxidative effect Effects 0.000 claims abstract description 3
- 238000005086 pumping Methods 0.000 claims abstract 2
- 239000000126 substance Substances 0.000 claims description 11
- 238000005868 electrolysis reaction Methods 0.000 claims description 10
- 229910052799 carbon Inorganic materials 0.000 claims description 8
- 150000003839 salts Chemical class 0.000 claims description 8
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 claims description 6
- -1 fluoride ions Chemical class 0.000 claims description 5
- 229910003460 diamond Inorganic materials 0.000 claims description 3
- 239000010432 diamond Substances 0.000 claims description 3
- 229910000831 Steel Inorganic materials 0.000 claims description 2
- 238000010790 dilution Methods 0.000 claims description 2
- 239000012895 dilution Substances 0.000 claims description 2
- 239000008187 granular material Substances 0.000 claims description 2
- 230000014759 maintenance of location Effects 0.000 claims description 2
- 230000035484 reaction time Effects 0.000 claims description 2
- 239000010959 steel Substances 0.000 claims description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 claims 1
- 230000001174 ascending effect Effects 0.000 claims 1
- 239000002245 particle Substances 0.000 claims 1
- 239000013043 chemical agent Substances 0.000 description 8
- 230000000694 effects Effects 0.000 description 8
- 229910052751 metal Inorganic materials 0.000 description 8
- 239000002184 metal Substances 0.000 description 8
- 238000011160 research Methods 0.000 description 5
- 230000015556 catabolic process Effects 0.000 description 4
- 238000006731 degradation reaction Methods 0.000 description 4
- 238000003795 desorption Methods 0.000 description 3
- 229910017053 inorganic salt Inorganic materials 0.000 description 3
- 238000010525 oxidative degradation reaction Methods 0.000 description 3
- 238000004064 recycling Methods 0.000 description 3
- 239000011347 resin Substances 0.000 description 3
- 229920005989 resin Polymers 0.000 description 3
- 238000004065 wastewater treatment Methods 0.000 description 3
- YOALFLHFSFEMLP-UHFFFAOYSA-N azane;2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-pentadecafluorooctanoic acid Chemical compound [NH4+].[O-]C(=O)C(F)(F)C(F)(F)C(F)(F)C(F)(F)C(F)(F)C(F)(F)C(F)(F)F YOALFLHFSFEMLP-UHFFFAOYSA-N 0.000 description 2
- 125000004122 cyclic group Chemical group 0.000 description 2
- 238000006056 electrooxidation reaction Methods 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 239000012528 membrane Substances 0.000 description 2
- 239000003960 organic solvent Substances 0.000 description 2
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- 238000000926 separation method Methods 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- SNGREZUHAYWORS-UHFFFAOYSA-M 2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-pentadecafluorooctanoate Chemical compound [O-]C(=O)C(F)(F)C(F)(F)C(F)(F)C(F)(F)C(F)(F)C(F)(F)C(F)(F)F SNGREZUHAYWORS-UHFFFAOYSA-M 0.000 description 1
- 206010007269 Carcinogenicity Diseases 0.000 description 1
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 1
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 1
- 241000282414 Homo sapiens Species 0.000 description 1
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 230000007670 carcinogenicity Effects 0.000 description 1
- 231100000260 carcinogenicity Toxicity 0.000 description 1
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- 230000007547 defect Effects 0.000 description 1
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- 238000005265 energy consumption Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000008394 flocculating agent Substances 0.000 description 1
- 229910052731 fluorine Inorganic materials 0.000 description 1
- 239000011737 fluorine Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 229910000040 hydrogen fluoride Inorganic materials 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000001728 nano-filtration Methods 0.000 description 1
- 230000001376 precipitating effect Effects 0.000 description 1
- 239000012716 precipitator Substances 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 229910052938 sodium sulfate Inorganic materials 0.000 description 1
- 235000011152 sodium sulphate Nutrition 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/28—Treatment of water, waste water, or sewage by sorption
- C02F1/283—Treatment of water, waste water, or sewage by sorption using coal, charred products, or inorganic mixtures containing them
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
- B01J20/30—Processes for preparing, regenerating, or reactivating
- B01J20/34—Regenerating or reactivating
- B01J20/3416—Regenerating or reactivating of sorbents or filter aids comprising free carbon, e.g. activated carbon
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
- B01J20/30—Processes for preparing, regenerating, or reactivating
- B01J20/34—Regenerating or reactivating
- B01J20/345—Regenerating or reactivating using a particular desorbing compound or mixture
- B01J20/3475—Regenerating or reactivating using a particular desorbing compound or mixture in the liquid phase
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/02—Treatment of water, waste water, or sewage by heating
- C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
- C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
- C02F1/467—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis by electrochemical disinfection; by electrooxydation or by electroreduction
- C02F1/4672—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis by electrochemical disinfection; by electrooxydation or by electroreduction by electrooxydation
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/30—Organic compounds
- C02F2101/34—Organic compounds containing oxygen
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/30—Organic compounds
- C02F2101/36—Organic compounds containing halogen
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2303/00—Specific treatment goals
- C02F2303/16—Regeneration of sorbents, filters
Abstract
The invention discloses a method for treating low-concentration perfluoro caprylic acid-containing wastewater, which comprises the following steps: the wastewater containing low-concentration perfluorooctanoic acid passes through activated carbon adsorption equipment; the wastewater reaching the standard after passing through the activated carbon adsorption equipment can be directly discharged or subjected to next treatment, and the activated carbon with saturated adsorption is transferred to activated carbon regeneration equipment and regenerated by combining ethanol and sodium chloride medicaments; transferring the regenerated activated carbon to the activated carbon adsorption equipment for continuous adsorption; pumping the regenerated waste liquid into evaporation equipment from a waste liquid collecting tank through a lifting pump, wherein the main purpose is to recover the ethanol through evaporation, so that the ethanol is reused, and discharging the residual mother liquid into a mother liquid collecting device; after evaporation, the mother liquor is pumped from the mother liquor collection device into an electrolytic oxidation device through a water pump, and the device mainly has the function of oxidizing perfluorooctanoic acid in the mother liquor. The invention can realize the standard discharge of the waste water containing the perfluorooctanoic acid and the harmless treatment of the regenerated waste liquid.
Description
Technical Field
The invention relates to the technical field of wastewater treatment, in particular to a method for treating low-concentration perfluorooctanoic acid-containing wastewater.
Background
Perfluoro-compounds are mainly artificially synthesized compounds with very stable structural properties and special physicochemical properties such as hydrophobicity and oleophobicity, and are currently one of the important raw materials in industry. It is difficult to degrade in the natural environment due to its stable structural properties. Research shows that the perfluoro-substances can be accumulated in organisms and have certain carcinogenicity on human beings. In recent years, with the increase of detected perfluorinated substances in environmental water bodies, the wastewater containing the perfluorinated substances has more and more attention to the standard discharge of the wastewater.
Perfluorooctanoic acid is widely used in industry as one of typical perfluoro-type substances. The existing perfluorooctanoic acid wastewater treatment method mainly comprises physical and chemical modes, such as membrane separation and recycling, resin adsorption, activated carbon powder adsorption, metal salt precipitation and recycling and the like. These methods have respective advantages under specific conditions, but in the low-concentration waste water of the perfluorooctanoic acid (the concentration of the perfluorooctanoic acid is less than 30mg/L), the methods of membrane separation and metal salt precipitation recovery are not economically and technically feasible. For example, in CN101928078B, two-stage nanofiltration is used to concentrate low-concentration perfluorooctanoic acid wastewater to a concentration of 5-30 wt% of perfluorooctanoic acid, and then the perfluorooctanoic acid is recycled. If the wastewater with the concentration of the perfluorooctanoic acid of about 30mg/L is concentrated until the concentration of the perfluorooctanoic acid reaches 5 wt%, the concentration multiple reaches 1666.67 times, and the high multiple has great technical difficulty; in CN100420666C, divalent metal salt is used as a precipitator, trivalent metal salt is used as a flocculating agent to treat wastewater containing ammonium perfluorooctanoate, the addition amount of the divalent metal salt is required to be 0.1-0.2% of the weight of mother liquor, the addition amount of the trivalent metal salt is required to be 0.05-0.1% of the weight of the mother liquor, the addition amount of the metal salt required for precipitating and separating the ammonium perfluorooctanoate is large, and a large amount of metal salt ions added can cause secondary pollution, so that the method is not suitable for wastewater with low concentration of the perfluorooctanoate (<30 mg/L).
Researches show that the adsorption of the activated carbon and the resin is an effective mode for treating the waste water containing low-concentration perfluorooctanoic acid, and the method has the advantages of high adsorption efficiency, simplicity, convenience, reusability and the like. However, the resin adsorption is greatly affected by competitive ions, the concentration of the regenerated consumed chemical is high, the amount of the consumed chemical is large, and the treatment of the regenerated waste liquid is difficult. Therefore, in summary, the activated carbon adsorption is more suitable for treating the wastewater containing low-concentration perfluorooctanoic acid.
The core problem of applying the activated carbon to the treatment of the wastewater containing low-concentration perfluorooctanoic acid is how to realize the recycling of the activated carbon, namely the regeneration of the activated carbon. The existing regeneration modes of the activated carbon include high-temperature regeneration and chemical agent regeneration. At present, the regeneration mode which is applied more in engineering is mainly high-temperature regeneration, and only a few researches relate to the mode of using chemical agents to regenerate the activated carbon. High-temperature regeneration energy consumption is large, operation cost is high, one-time investment cost is high, a fluorine-containing substance can form a hydrogen fluoride substance which is easy to corrode equipment after being heated, the equipment is difficult to maintain, and the equipment replacement frequency is high, so that the method is not an ideal regeneration method; at present, the engineering application of the mode of regenerating by using chemical agents is less, and especially reports on the regeneration of the activated carbon adsorbing the perfluorooctanoic acid are more rare. Some researchers use the medicine combination of organic solvent ethanol and inorganic salt sodium chloride to regenerate the activated carbon adsorbing the perfluorooctanoic acid, and the effect is obvious. However, no mention is made at present on how to dispose the regenerated waste liquid containing a large amount of perfluorooctanoic acid and ethanol, which is an organic solvent.
Therefore, the technical personnel in the field expand the treatment of the regenerated waste liquid containing a large amount of perfluorooctanoic acid, ethanol and sodium chloride after the regeneration of the active carbon chemical agent, and further perfect the whole process flow of the adsorption, regeneration and regeneration of the active carbon in the treatment of the waste water containing low-concentration perfluorooctanoic acid.
Disclosure of Invention
In view of the above defects in the prior art, the technical problem to be solved by the present invention is to provide a method for treating low-concentration perfluorooctanoic acid-containing wastewater (the concentration of perfluorooctanoic acid is less than 30mg/L), which comprises activated carbon adsorption, chemical agent regeneration of adsorption saturated activated carbon, and oxidation treatment of regenerated waste liquid, and finally achieves the purpose of up-to-standard discharge of perfluorooctanoic acid-containing wastewater and harmless treatment of regenerated waste liquid.
In order to achieve the aim, the invention provides a method for treating low-concentration perfluorooctanoic acid-containing wastewater, which comprises the following steps:
(1) the wastewater containing low-concentration perfluorooctanoic acid passes through activated carbon adsorption equipment;
(2) the wastewater reaching the standard after passing through the activated carbon adsorption equipment can be directly discharged or subjected to next treatment, and the activated carbon with saturated adsorption is transferred to activated carbon regeneration equipment and regenerated by combining ethanol and sodium chloride medicaments;
(3) transferring the regenerated active carbon to the active carbon adsorption equipment for continuous adsorption, discharging regenerated waste liquid formed after regeneration to a waste liquid collecting tank, wherein the regenerated waste liquid mainly contains higher-concentration perfluorooctanoic acid, ethanol with the concentration of about 47.5 wt% and sodium chloride with the concentration of about 1.5 wt%;
(4) the regeneration waste liquid is firstly pumped into evaporation equipment from the waste liquid collecting tank through a lifting pump, the ethanol is recovered through evaporation, the ethanol is reused, the residual mother liquid is discharged into a mother liquid collecting device, and the mother liquid mainly contains perfluorooctanoic acid with a certain concentration, ethanol with a concentration of about 5-8 wt% and sodium chloride with a concentration of about 1.5 wt%. The concentration of the perfluorooctanoic acid with a certain concentration is consistent with that of the perfluorooctanoic acid in the step (3), namely the perfluorooctanoic acid is not evaporated out along with ethanol in the evaporation process;
(5) after evaporation, the mother liquor is pumped from the mother liquor collection device into an electrolytic oxidation device through a water pump, and the device mainly has the function of oxidizing perfluorooctanoic acid in the mother liquor.
Furthermore, the activated carbon is selected from granules, and the grain size is 0.8-1.3 mm.
Furthermore, the rising flow rate of the low-concentration perfluoro caprylic acid-containing wastewater in the activated carbon adsorption equipment is less than or equal to 10m/h, and the retention time of the low-concentration perfluoro caprylic acid-containing wastewater in the activated carbon adsorption equipment is required to be more than or equal to 30 min.
Further, in the ethanol and sodium chloride medicament combination, the concentration of sodium chloride is 1-5 wt%, the concentration of ethanol is more than or equal to 95 wt%, and the ethanol and the sodium chloride are added according to the volume ratio of 1:1 during regeneration.
Further, the regeneration time in the step (2) is 1-3 h, and the regeneration temperature is controlled to be 35-45 ℃.
Furthermore, the electrolytic oxidation device comprises a cathode and an anode, wherein the cathode plate is made of 316L steel, the anode plate is made of boron-doped diamond, the distance between the electrode plates is required to be 0.5-1 cm, and the oxidation reaction time is 1-5 h.
Further, the power supply uses a direct current power supply, and the current density is controlled to be 100-300 mA/cm2。
Furthermore, sulfate needs to be added in the electrolytic process of the regenerated waste liquid to improve the electrolytic oxidation efficiency of the perfluorooctanoic acid, and the mass concentration ratio of the added sulfate to the perfluorooctanoic acid in the regenerated waste liquid is 0.5-1: 1.
Further, the regeneration waste liquid in the step (3) contains perfluorooctanoic acid, sodium chloride and ethanol.
Furthermore, the waste water after electrolysis in the step (5) mainly contains fluorinion, inorganic salt and organic matters with good biodegradability, the part of waste water can enter a front end biochemical system of the waste water again, the organic matters are removed through biochemical action, and meanwhile, because the regenerated waste liquid is less, the fluorinion and the chloridion can reach the standard and be discharged through the dilution of the front end to the waste water.
Experimental research shows that in the process of regenerating the activated carbon by using ethanol and sodium chloride, the regeneration effect can be greatly improved by controlling the temperature to be 35-45 ℃ and the temperature to be significantly influenced;
meanwhile, researches also find that the effect of electro-oxidative degradation of perfluorooctanoic acid by using the sodium chloride regeneration waste liquid is poor, the degradation rate is only about 30%, and the efficiency of electro-oxidative degradation of perfluoro can be greatly improved to 90-95% by adding a certain amount of sulfate ions into the regeneration waste liquid.
The invention provides a method for treating low-concentration perfluoro caprylic acid-containing wastewater, which comprises a complete set of processes of activated carbon adsorption enrichment, chemical agent regeneration of saturated activated carbon and final treatment of regenerated waste liquid, and has feasible technology and industrial application.
The conception, the specific structure and the technical effects of the present invention will be further described with reference to the accompanying drawings to fully understand the objects, the features and the effects of the present invention.
Drawings
FIG. 1 is a process flow chart of a method for treating waste water containing low concentration perfluorooctanoic acid according to a preferred embodiment of the present invention.
Detailed Description
The technical contents of the preferred embodiments of the present invention will be more clearly and easily understood by referring to the drawings attached to the specification. The present invention may be embodied in many different forms of embodiments and the scope of the invention is not limited to the embodiments set forth herein.
Example 1
Adsorption and regeneration of active carbon to perfluorooctanoic acid wastewater
The perfluoro caprylic acid contained in the wastewater discharged by a certain factory has the concentration of about 20-30 mg/L, and after the perfluoro caprylic acid is adsorbed by active carbon, the concentration of the effluent perfluoro caprylic acid is less than 10mg/L, so that the discharge requirement is met;
in order to verify the regeneration effect of ethanol and sodium chloride on saturated activated carbon after adsorption of perfluorooctanoic acid, taking 25ml of the activated carbon with saturated adsorption, adding 50ml of a medicament combination of 95 wt% of ethanol and 3 wt% of sodium chloride, wherein the volume ratio of the ethanol to the sodium chloride is 1:1, heating the activated carbon in a water bath to 40 ℃, and detecting that the concentration of the perfluorooctanoic acid in a regeneration liquid is 8465mg/L when the regeneration time is 1h, and converting the concentration into 16.93mg/ml of the amount of the activated carbon desorbed perfluorooctanoic acid per ml;
in order to verify the adsorption effect of the regenerated activated carbon on the wastewater containing the perfluorooctanoic acid, 25mL of the regenerated and desorbed activated carbon is placed in a small adsorption device, 25L of the wastewater containing the perfluorooctanoic acid is used for cyclic adsorption, the concentration of the perfluorooctanoic acid in the wastewater before adsorption is 28.34mg/L, the concentration of the perfluorooctanoic acid in the wastewater after 24 hours of cyclic adsorption is 11.08mg/L, the adsorption amount is 431.5mg, the adsorption amount is converted into 17.26mg/mL of the activated carbon per mL, and the adsorption amount basically corresponds to the desorption amount of 16.93mg/mL of the activated carbon during the first regeneration;
in order to verify the repeatability of the combined medicament of ethanol and sodium chloride on the regeneration effect of the activated carbon saturated by the adsorbed perfluorooctanoic acid, the 25mL of activated carbon is continuously subjected to 3 times of adsorption and desorption tests, the obtained data are shown in Table 1, and the data in Table 1 show that the combined medicament of ethanol and sodium chloride has repeatability on the regeneration of the activated carbon saturated by the adsorbed perfluorooctanoic acid.
TABLE 1 desorption amount for regeneration and adsorption amount after regeneration of activated carbon
Example 2
Electrooxidation treatment of regenerated waste liquid
Putting a certain amount of the regenerated waste liquid into an electrolysis device for electrolysis, and controlling the current density to be 150mA/cm2The initial concentration of the perfluorooctanoic acid in the regeneration waste liquid is 4356.23mg/L, the concentration of the ethanol is about 5 wt%, the concentration of the sodium chloride is about 1.5 wt%, after 3 hours of electrolysis, the concentration of the perfluorooctanoic acid in the regeneration waste liquid is 3005.80mg/L, and the degradation rate is about 31%;
putting a certain amount of the regenerated waste liquid into an electrolysis device, adding sulfate radicals with the same concentration as that of the perfluorooctanoic acid, performing electrolysis, controlling the current density to be 150mA/cm2, controlling the initial concentration of the perfluorooctanoic acid in the regenerated waste liquid to be 4356.23mg/L, the concentration of ethanol to be about 5 wt% and the concentration of sodium chloride to be about 1.5 wt%, and after 3 hours of electrolysis, controlling the concentration of the perfluorooctanoic acid in the regenerated waste liquid to be 335.43mg/L and the degradation rate to be 92.3%;
through comparison of the two groups of experiments, it can be seen that the degradation efficiency of the perfluorooctanoic acid can be greatly improved by adding another inorganic salt sulfate ion, such as sodium sulfate, into the regenerated waste liquid, which provides a feasible technical scheme for engineering application of the whole process flow from adsorption and regeneration to treatment of the regenerated waste liquid in the activated carbon adsorption perfluorooctanoic acid wastewater treatment process, and a specific process flow diagram of the treatment method of the low-concentration perfluorooctanoic acid-containing wastewater is shown in fig. 1.
In conclusion, the invention discloses a method for treating wastewater containing low-concentration perfluorooctanoic acid, which comprises the steps of activated carbon adsorption, regeneration of adsorption saturated activated carbon chemical agents and oxidative degradation treatment of regenerated waste liquor containing high-concentration perfluorooctanoic acid. The waste water containing low-concentration perfluorooctanoic acid is absorbed by an activated carbon absorption system, and the effluent can be directly discharged up to the standard or recycled; the activated carbon with saturated adsorption is regenerated by using chemical agents of sodium chloride and ethanol, and the regenerated activated carbon is returned to the activated carbon adsorption system again for adsorption, so that the repeated utilization is realized; regenerated waste liquid contains a large amount of perfluoro caprylic acid, sodium chloride and ethanol, ethanol is separated and recycled through a distillation mode, the rest solution containing the perfluoro caprylic acid, the sodium chloride and a small amount of ethanol is subjected to electrolytic oxidation through an electrolytic bath consisting of a diamond electrode, sulfate radicals are added in the electrolytic process to improve the electrooxidation efficiency of the perfluoro caprylic acid, the regenerated waste liquid after electrolysis can enter a biochemical treatment system to be treated, and the up-to-standard discharge of the waste water containing the perfluoro caprylic acid and the harmless treatment of the regenerated waste liquid are realized.
The foregoing detailed description of the preferred embodiments of the invention has been presented. It should be understood that numerous modifications and variations could be devised by those skilled in the art in light of the present teachings without departing from the inventive concepts. Therefore, the technical solutions available to those skilled in the art through logic analysis, reasoning and limited experiments based on the prior art according to the concept of the present invention should be within the scope of protection defined by the claims.
Claims (10)
1. A method for treating wastewater containing low-concentration perfluorooctanoic acid is characterized by comprising the following steps:
(1) the wastewater containing low-concentration perfluorooctanoic acid passes through activated carbon adsorption equipment;
(2) the wastewater reaching the standard after passing through the activated carbon adsorption equipment can be directly discharged or subjected to next treatment, and the activated carbon with saturated adsorption is transferred to activated carbon regeneration equipment and regenerated by combining ethanol and sodium chloride medicaments;
(3) transferring the regenerated active carbon to the active carbon adsorption equipment for continuous adsorption, and discharging regenerated waste liquid formed after regeneration to a waste liquid collecting tank;
(4) pumping the regenerated waste liquid into evaporation equipment from the waste liquid collecting tank through a lifting pump, wherein the main purpose is to recover the ethanol through evaporation, so that the ethanol can be reused, and discharging the residual mother liquid into a mother liquid collecting device;
(5) after evaporation, the mother liquor is pumped from the mother liquor collection device into an electrolytic oxidation device through a water pump, and the device mainly has the function of oxidizing perfluorooctanoic acid in the mother liquor.
2. The method for treating wastewater containing low-concentration perfluorooctanoic acid according to claim 1, wherein the activated carbon is in the form of granules having a particle size of 0.8 to 1.3 mm.
3. The method for treating the wastewater containing the low-concentration perfluoro caprylic acid according to claim 1, wherein the ascending flow velocity of the wastewater containing the low-concentration perfluoro caprylic acid in the activated carbon adsorption equipment is less than or equal to 10m/h, and the retention time of the wastewater containing the low-concentration perfluoro caprylic acid in the activated carbon adsorption equipment is required to be more than or equal to 30 min.
4. The method for treating wastewater containing low-concentration perfluorooctanoic acid according to claim 1, wherein the concentration of sodium chloride in the combination of "ethanol + sodium chloride" is 1 wt% to 5 wt%, the concentration of ethanol is not less than 95 wt%, and the ethanol and the sodium chloride are added in a volume ratio of 1:1 during regeneration.
5. The method for treating wastewater containing low-concentration perfluorooctanoic acid according to claim 1, wherein the regeneration time in the step (2) is 1 to 3 hours, and the regeneration temperature is controlled to 35 to 45 ℃.
6. The method for treating wastewater containing low-concentration perfluorooctanoic acid according to claim 1, wherein the electrolytic oxidation apparatus comprises a cathode and an anode, the cathode is made of 316L steel, the anode is made of boron-doped diamond, the distance between the electrode plates is 0.5 to 1cm, and the oxidation reaction time is 1 to 5 hours.
7. The method for treating wastewater containing low-concentration perfluorooctanoic acid according to claim 6, wherein a DC power source is used as a power source, and the current density is controlled to be 100 to 300mA/cm2。
8. The method for treating the low-concentration perfluoro caprylic acid-containing wastewater as claimed in claim 1, wherein sulfate needs to be added in the regeneration waste liquid electrolysis process to improve the electrolytic oxidation efficiency of the perfluoro caprylic acid, and the mass concentration ratio of the added sulfate to the perfluoro caprylic acid in the regeneration waste liquid is 0.5-1: 1.
9. The method according to claim 1, wherein the regeneration waste liquid in step (3) contains the perfluorooctanoic acid, the sodium chloride and the ethanol.
10. The method for treating wastewater containing low concentration perfluorooctanoic acid according to claim 1, wherein the wastewater after the electrolysis in the step (5) mainly contains fluoride ions, inorganic salts, and organic substances with good biodegradability, and the wastewater can be fed back to a front end biochemical system of the wastewater to remove the organic substances through biochemical action, and the fluoride ions and chloride ions can be discharged up to the standard through the dilution of the wastewater by the front end due to less regenerated waste liquid.
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