CN117509842A - Method for synchronously recycling ammonia nitrogen and removing heavy metals through electrodialysis of wastewater - Google Patents
Method for synchronously recycling ammonia nitrogen and removing heavy metals through electrodialysis of wastewater Download PDFInfo
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- CN117509842A CN117509842A CN202210910689.6A CN202210910689A CN117509842A CN 117509842 A CN117509842 A CN 117509842A CN 202210910689 A CN202210910689 A CN 202210910689A CN 117509842 A CN117509842 A CN 117509842A
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- XKMRRTOUMJRJIA-UHFFFAOYSA-N ammonia nh3 Chemical compound N.N XKMRRTOUMJRJIA-UHFFFAOYSA-N 0.000 title claims abstract description 123
- 229910001385 heavy metal Inorganic materials 0.000 title claims abstract description 89
- 238000000909 electrodialysis Methods 0.000 title claims abstract description 88
- 239000002351 wastewater Substances 0.000 title claims abstract description 74
- 238000000034 method Methods 0.000 title claims abstract description 66
- 238000004064 recycling Methods 0.000 title claims abstract description 10
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 72
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims description 32
- 239000000243 solution Substances 0.000 claims description 27
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 22
- 239000004408 titanium dioxide Substances 0.000 claims description 16
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 15
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 claims description 15
- 239000002106 nanomesh Substances 0.000 claims description 15
- 239000006260 foam Substances 0.000 claims description 14
- 239000011572 manganese Substances 0.000 claims description 13
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 claims description 12
- 229910052748 manganese Inorganic materials 0.000 claims description 12
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 11
- 239000011259 mixed solution Substances 0.000 claims description 11
- 239000010936 titanium Substances 0.000 claims description 11
- 229910052719 titanium Inorganic materials 0.000 claims description 11
- 239000007864 aqueous solution Substances 0.000 claims description 10
- 239000003792 electrolyte Substances 0.000 claims description 8
- 229910021645 metal ion Inorganic materials 0.000 claims description 8
- 238000001035 drying Methods 0.000 claims description 7
- 230000007935 neutral effect Effects 0.000 claims description 7
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical group [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 claims description 6
- -1 ammonium ions Chemical class 0.000 claims description 6
- 238000001354 calcination Methods 0.000 claims description 6
- 239000012528 membrane Substances 0.000 claims description 6
- 238000002156 mixing Methods 0.000 claims description 6
- 238000002791 soaking Methods 0.000 claims description 6
- 229910052938 sodium sulfate Inorganic materials 0.000 claims description 6
- 235000011152 sodium sulphate Nutrition 0.000 claims description 6
- 238000005406 washing Methods 0.000 claims description 6
- 238000001027 hydrothermal synthesis Methods 0.000 claims description 5
- 235000006408 oxalic acid Nutrition 0.000 claims description 5
- 238000002360 preparation method Methods 0.000 claims description 5
- 230000035484 reaction time Effects 0.000 claims description 5
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 3
- 244000137852 Petrea volubilis Species 0.000 claims description 3
- 229910052799 carbon Inorganic materials 0.000 claims description 3
- 239000011261 inert gas Substances 0.000 claims description 3
- 239000011133 lead Substances 0.000 claims description 3
- 238000003756 stirring Methods 0.000 claims description 3
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 2
- 229910052793 cadmium Inorganic materials 0.000 claims description 2
- BDOSMKKIYDKNTQ-UHFFFAOYSA-N cadmium atom Chemical compound [Cd] BDOSMKKIYDKNTQ-UHFFFAOYSA-N 0.000 claims description 2
- 229910052804 chromium Inorganic materials 0.000 claims description 2
- 239000011651 chromium Substances 0.000 claims description 2
- 229910017052 cobalt Inorganic materials 0.000 claims description 2
- 239000010941 cobalt Substances 0.000 claims description 2
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims description 2
- 238000000227 grinding Methods 0.000 claims description 2
- 239000002904 solvent Substances 0.000 claims description 2
- 230000007613 environmental effect Effects 0.000 abstract description 6
- 239000003153 chemical reaction reagent Substances 0.000 abstract description 3
- 238000011084 recovery Methods 0.000 abstract description 3
- 239000002699 waste material Substances 0.000 abstract description 3
- 239000003337 fertilizer Substances 0.000 abstract description 2
- 230000000694 effects Effects 0.000 description 11
- 238000006243 chemical reaction Methods 0.000 description 10
- 238000005342 ion exchange Methods 0.000 description 7
- 239000002893 slag Substances 0.000 description 7
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 6
- 230000005684 electric field Effects 0.000 description 6
- 150000002500 ions Chemical class 0.000 description 6
- 230000008569 process Effects 0.000 description 6
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Substances [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 5
- 239000000126 substance Substances 0.000 description 5
- 238000002834 transmittance Methods 0.000 description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
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- 235000019441 ethanol Nutrition 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
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- 229910052759 nickel Inorganic materials 0.000 description 3
- 239000002244 precipitate Substances 0.000 description 3
- 241000195493 Cryptophyta Species 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 229910002651 NO3 Inorganic materials 0.000 description 2
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 2
- 230000003197 catalytic effect Effects 0.000 description 2
- 239000000356 contaminant Substances 0.000 description 2
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- 238000012851 eutrophication Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 description 2
- 229910052697 platinum Inorganic materials 0.000 description 2
- 231100000719 pollutant Toxicity 0.000 description 2
- 238000007086 side reaction Methods 0.000 description 2
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- 241000143060 Americamysis bahia Species 0.000 description 1
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- 241001465754 Metazoa Species 0.000 description 1
- IOVCWXUNBOPUCH-UHFFFAOYSA-M Nitrite anion Chemical compound [O-]N=O IOVCWXUNBOPUCH-UHFFFAOYSA-M 0.000 description 1
- 238000003723 Smelting Methods 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 150000001450 anions Chemical class 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 150000001768 cations Chemical class 0.000 description 1
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- 239000007857 degradation product Substances 0.000 description 1
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- 239000008367 deionised water Substances 0.000 description 1
- 229910021641 deionized water Inorganic materials 0.000 description 1
- 239000003651 drinking water Substances 0.000 description 1
- 235000020188 drinking water Nutrition 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
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- 230000036541 health Effects 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 229910017053 inorganic salt Inorganic materials 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 230000002427 irreversible effect Effects 0.000 description 1
- 210000004185 liver Anatomy 0.000 description 1
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Classifications
-
- 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
- C02F1/469—Treatment of water, waste water, or sewage by electrochemical methods by electrochemical separation, e.g. by electro-osmosis, electrodialysis, electrophoresis
- C02F1/4693—Treatment of water, waste water, or sewage by electrochemical methods by electrochemical separation, e.g. by electro-osmosis, electrodialysis, electrophoresis electrodialysis
-
- 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
- C02F2101/10—Inorganic compounds
- C02F2101/16—Nitrogen compounds, e.g. ammonia
-
- 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
- C02F2101/10—Inorganic compounds
- C02F2101/20—Heavy metals or heavy metal compounds
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
- C02F2103/10—Nature of the water, waste water, sewage or sludge to be treated from quarries or from mining activities
Abstract
The invention discloses a method for synchronously recycling ammonia nitrogen and removing heavy metals by electrodialysis of wastewater. The method can realize the recovery of high-concentration ammonia nitrogen while removing heavy metals in wastewater under the condition of no additional chemical reagent, and the recovered high-concentration ammonia nitrogen can be used as fertilizer, thereby achieving the purpose of waste utilization and conforming to the scientific concept of economy and environmental protection.
Description
Technical Field
The invention belongs to the technical field of ecological environment treatment, and particularly relates to a method for synchronously recycling ammonia nitrogen and removing heavy metals by utilizing electrodialysis.
Background
Ammonia nitrogen and heavy metal pollution in water resources are all major environmental problems to be solved urgently. Along with the exploitation and smelting process of metal, heavy metal migrates to the surrounding water and soil environment along with surface runoff in the form of simple substances or metal ions, so that large-area water and soil pollution is caused. It is self-evident that the harm of heavy metals is that after entering the human body, the heavy metals directly damage the liver and even affect the nervous system, causing irreversible damage. Thus, heavy metal concentrations have been severely limited in surface water environmental emission standards over the years. In addition, although ammonia nitrogen is a nutrient substance required by plants, no report on harm of ammonia nitrogen to human health in drinking water exists so far, but excessive ammonia nitrogen still has a great threat to aquatic organisms. It is well known that water body rich oxidation can cause algae to grow excessively, thereby depriving living space of other animals and plants; meanwhile, the algae toxins and ammonia nitrogen have certain biotoxicity to fishes and shrimps, and the eutrophication of the water body and the odor of the water body caused by the eutrophication of the water body also seriously affect the normal activities of human beings. Therefore, ammonia nitrogen and heavy metal pollution are important research directions in the current environmental field.
In the actual production process, water bodies in which two pollutants of ammonia nitrogen and heavy metals exist simultaneously are often produced, for example: manganese slag percolate, landfill percolate, biogas slurry and the like. Taking the manganese slag percolate as an example, as one of the indispensable raw materials in the iron and steel industry, the exploitation history of manganese ores is long and the demand is large, and the yield of Chinese manganese ores is kept to be the first worldwide before 2018. However, electrolytic manganese slag is not listed in the national hazardous waste directory as the most important pollutant in the manganese production process, and the manganese slag is stored by adopting a stacking method all the time, so that huge pressure is caused to a stacking space, and meanwhile, the ecological environment around a stacking field is seriously endangered. Particularly, after rain wash, a large amount of toxic and harmful substances such as ammonia nitrogen, heavy metal and the like in manganese slag enter surrounding surface water bodies along with surface runoff in the form of percolate or migrate to surrounding soil and even groundwater to cause large-area water and soil pollution.
For the treatment technology of ammonia nitrogen, the current common methods are biochemical method, catalytic oxidation method, ion exchange method and precipitation method. Biochemical methods, such as chinese patent document CN109354335a, disclose an optimized combination process for town domestic sewage treatment, which has the disadvantages of excessively long reaction time, incomplete degradation, nitrate as degradation product, and easy secondary pollution. Catalytic oxidation methods, such as CN112607924a, disclose a total nitrogen removal method for nitrogen-containing organic wastewater, which has shorter reaction time than biochemical methods, and can also thoroughly convert ammonia nitrogen into other nitrogen-containing substances, but nitrate and nitrite with stronger toxicity are easily produced in the reaction process, and more importantly, ammonia nitrogen belongs to inorganic salt nitrogen which can be directly absorbed by plants, and the purification value of ammonia nitrogen is greater than that of direct oxidation. The precipitation method has the advantages of simplest operation and fastest reaction, and can simultaneously precipitate heavy metals and recycle ammonia nitrogen, but a large amount of chemical reagents are needed in the reaction process, and the method does not meet the requirements of environmental protection. An ion exchange method and an adsorption method, such as CN105271468A, disclose an ion exchange device for removing ammonia nitrogen by an ion exchange method, which is a relatively mild and economical way for recovering ammonia nitrogen, is applicable to pure ammonia nitrogen wastewater or heavy metal wastewater, and is not applicable to mixed wastewater of ammonia nitrogen and heavy metal, because the pure ion exchange method cannot separate ammonia nitrogen and heavy metal at the same time; in addition, the driving force of ion exchange is generally a concentration difference, and if a high concentration of contaminants is treated, the effect is remarkable in the initial stage of the reaction, but as the reaction time goes on, the lower the concentration of contaminants, the more difficult the ion exchange is. Therefore, a method for synchronously removing heavy metals and recycling ammonia nitrogen in wastewater is urgently needed, and the method has very important significance for environmental pollution control and waste utilization.
Disclosure of Invention
The invention aims to solve the technical problem of overcoming the defects of the prior art and providing a method for synchronously recovering ammonia nitrogen and removing heavy metals by electrodialysis of wastewater, which can synchronously remove heavy metals in wastewater and recover ammonia nitrogen.
In order to solve the technical problems, the invention adopts the following technical scheme.
A method for synchronously recovering ammonia nitrogen and removing heavy metals by electrodialysis of wastewater comprises the following steps: preparing an electrodialysis system, wherein the electrodialysis system comprises an anode chamber provided with an anode and a cathode chamber provided with a cathode, a proton exchange membrane is arranged between the anode chamber and the cathode chamber, and the anode is a self-supporting titanium dioxide nano-mesh electrode; introducing wastewater containing ammonia nitrogen and heavy metal into an anode chamber of the electrodialysis system for electrodialysis treatment, enabling ammonium ions and metal ions to enter a cathode chamber through a proton exchange membrane, and reacting to remove the heavy metal and recycle the ammonia nitrogen; the preparation method of the self-supporting titanium dioxide nano-mesh electrode comprises the following steps: mixing a mixed solution of sodium hydroxide and titanium foam, wherein a solvent in the mixed solution of sodium hydroxide is water and alcohol, performing hydrothermal reaction at 100-200 ℃, washing, drying, and calcining at 400-600 ℃ to obtain the self-supporting titanium dioxide nano-mesh electrode.
In the method for synchronously recovering ammonia nitrogen and removing heavy metals by electrodialysis of wastewater, preferably, the initial pH value of the wastewater containing ammonia nitrogen and heavy metals is 3-12, the concentration of ammonia nitrogen in the wastewater containing ammonia nitrogen and heavy metals is 25-200 mgN/L, the concentration of heavy metals in the wastewater containing ammonia nitrogen and heavy metals is 0.5-3.0 mg/L, and the heavy metals in the wastewater containing ammonia nitrogen and heavy metals comprise at least one of cadmium, chromium, lead, cobalt and manganese.
According to the method for synchronously recycling ammonia nitrogen and removing heavy metals by electrodialysis of wastewater, preferably, the electrolyte in the electrodialysis system is sodium sulfate solution, and the initial concentration of the sodium sulfate solution is 50-100 mmol/L.
In the method for synchronously recovering ammonia nitrogen and removing heavy metals by electrodialysis of wastewater, preferably, the current density in the electrodialysis system is 2mA/cm 2 ～6mA/cm 2 。
In the method for synchronously recovering ammonia nitrogen and removing heavy metals by electrodialysis of wastewater, preferably, the foam titanium is pretreated before mixing: grinding foam titanium by using sand paper with 50-200 meshes, soaking in sodium hydroxide aqueous solution for 1-2 h, then soaking in boiled oxalic acid solution for 1-2 h, and washing with water to be neutral; the mass fraction of the sodium hydroxide aqueous solution is 1-10%, and the mass fraction of the oxalic acid solution is 1-10%.
In the method for synchronously recovering ammonia nitrogen and removing heavy metals by electrodialysis of wastewater, preferably, the hydrothermal reaction time is 10-20 h, the calcination time is 1-2 h, and the calcination atmosphere is inert gas.
According to the method for synchronously recycling ammonia nitrogen and removing heavy metals by electrodialysis of wastewater, preferably, the preparation method of the mixed solution of sodium hydroxide comprises the following steps of: mixing sodium hydroxide aqueous solution with ethanol, and stirring for 10-30 min to obtain a mixed solution of sodium hydroxide; the volume ratio of the sodium hydroxide aqueous solution to the ethanol is 1-10:1, and the concentration of the sodium hydroxide aqueous solution is 0.5 mol/L-5 mol/L.
In the method for synchronously recovering ammonia nitrogen and removing heavy metals by electrodialysis of wastewater, preferably, the drying temperature is 40-60 ℃, and the drying time is 8-16 h.
In the method for synchronously recovering ammonia nitrogen and removing heavy metals by electrodialysis of wastewater, preferably, the electrodialysis treatment is carried out under normal pressure, the temperature of the electrodialysis treatment is 10-40 ℃, and the electrodialysis treatment time is 8-12 h.
In the method for synchronously recovering ammonia nitrogen and removing heavy metals by electrodialysis of wastewater, preferably, the cathode is a carbon felt cathode, the distance between the cathode and the anode is 8 cm-12 cm, and the facing area of the cathode and the anode is 8cm 2 ～12cm 2 。
Compared with the prior art, the invention has the advantages that:
the invention provides a method for synchronously recycling ammonia nitrogen and removing heavy metals by electrodialysis of wastewater, which is characterized in that after the wastewater containing ammonia nitrogen and heavy metals is introduced into an anode chamber of an electrodialysis system, ammonia nitrogen and heavy metals in the wastewater are gradually transferred from the anode chamber to a cathode chamber under the pushing of electric field force, and water in the anode chamber can reach the standard and be discharged at the moment; meanwhile, as the pH value in the anode chamber is reduced and the pH value in the cathode chamber is increased due to the unavoidable electrolytic water reaction in the electrodialysis process, a natural high pH value environment is created for the cathode chamber, and thus heavy metals entering the cathode chamber are converted into precipitates and are separated from ammonia nitrogen. Compared with anodes such as Pt and BDD commonly used in the market at present, the self-supporting titanium dioxide nano-mesh electrode selected by the method can quickly and efficiently push ammonia nitrogen to transfer to a cathode chamber, and the ammonia nitrogen transmittance is remarkably improved, so that ammonia nitrogen is easier to recycle, and the self-supporting titanium dioxide nano-mesh electrode has the advantages of being good in stability, difficult to corrode, good in reusability and the like. The method can realize the high-efficiency removal of heavy metals in the wastewater and the recovery of high-concentration ammonia nitrogen without adding any chemical reagent, and the recovered high-concentration ammonia nitrogen can be used as fertilizer, thereby achieving the purpose of waste utilization and conforming to the scientific concept of economy and environmental protection.
Drawings
FIG. 1 is a schematic diagram of a method for synchronously recovering ammonia nitrogen and removing heavy metals by electrodialysis of wastewater in embodiment 1 of the invention.
FIG. 2 is a graph showing the effect of removing heavy metals in the electrodialysis treatment according to example 1 of the present invention.
FIG. 3 is a graph showing the permeation rate of ammonia nitrogen in wastewater at different initial electrolyte concentrations in example 2 of the present invention.
FIG. 4 is a graph showing the permeation rate of ammonia nitrogen in wastewater under different pH conditions in example 3 of the present invention.
FIG. 5 is a graph of the permeation rate of ammonia nitrogen in wastewater versus the initial ammonia nitrogen concentration in example 4 of the present invention.
FIG. 6 is a graph showing the permeation rate of ammonia nitrogen in wastewater at different current densities in example 5 of the present invention.
FIG. 7 is a graph showing the effect of removing heavy metals in the electrodialysis treatment according to example 6 of the present invention.
FIG. 8 is a graph showing the permeation rate of ammonia nitrogen in wastewater at different anodes in example 7 of the present invention.
Detailed Description
The invention is further described below in connection with the drawings and the specific preferred embodiments, but the scope of protection of the invention is not limited thereby. The materials and instruments used in the examples below are all commercially available.
Example 1:
the invention relates to a method for synchronously recycling ammonia nitrogen and removing heavy metals by electrodialysis of wastewater, which adopts an electrodialysis system to carry out electrodialysis treatment on wastewater containing ammonia nitrogen and heavy metals, and comprises the following steps:
(1) Establishment of electrodialysis system:
the electrodialysis system comprises an anode chamber provided with an anode and a cathode chamber provided with a cathode, a proton exchange membrane is arranged between the anode chamber and the cathode chamber, the anode is a self-supporting titanium dioxide nano-mesh electrode, the cathode is a carbon felt cathode, the distance between the cathode and the anode is 8cm, and the facing area is 10cm 2 The electrolyte is sodium sulfate solution, is arranged in the cathode chamber and the anode chamber, has initial concentration of 50mmol/L and current density of 5mA/cm 2 。
The preparation method of the self-supporting titanium dioxide nano-mesh electrode specifically comprises the following steps:
cutting the foam titanium into a rectangle with medium size, polishing by using 100-mesh sand paper, firstly soaking in 5wt% NaOH solution for 1h, then soaking in boiling 10wt% oxalic acid solution for 2h, then washing to be neutral by using deionized water, obtaining pretreated foam titanium, and storing in absolute ethyl alcohol for later use.
(1.2) adding absolute ethyl alcohol into the NaOH solution according to the volume ratio of the absolute ethyl alcohol to the NaOH solution of 1:8 and the concentration of the NaOH solution of 0.5mol/L, and stirring for 10min to uniformly mix the solution to obtain a mixed solution of sodium hydroxide.
And (1.3) pouring the mixed solution of sodium hydroxide obtained in the step (1.2) into a polytetrafluoroethylene reaction kettle liner, and putting the pretreated foam titanium obtained in the step (1.1) into the mixed solution to perform hydrothermal reaction, namely, preserving heat at 180 ℃ for 16 hours to obtain the titanium dioxide nano-mesh electrode.
(1.4) repeatedly washing the titanium dioxide nano-mesh electrode obtained in the step (1.3) with clean water until the eluent is neutral, drying at 40 ℃ for 10 hours, then placing into a tube furnace, and under the atmosphere of inert gas, performing treatment at 4 ℃ for min -1 Heating to 500 deg.C, constant preserving for 2 hr, and furnace-followingAnd cooling to room temperature, and taking out to obtain the self-supporting titanium dioxide nano-mesh electrode.
(2) Electrodialysis treatment:
and (3) introducing the wastewater containing ammonia nitrogen and heavy metals into an anode chamber of an electrodialysis system, and staying at 25 ℃ for 8 hours under normal pressure to discharge clean water reaching standards, wherein ammonium ions and metal ions enter a cathode chamber to realize precipitation removal of metals and ammonia nitrogen recovery. Then, the next batch of wastewater containing ammonia nitrogen and heavy metals is replaced and enters an anode chamber of an electrodialysis system for electrodialysis treatment, so that the process is repeated, and the solution in the cathode chamber is not replaced in the whole circulation process, so that the purpose of concentrating ammonia nitrogen is achieved.
In this example, the initial concentration of ammonia nitrogen in the wastewater containing ammonia nitrogen and heavy metals was 50mgN/L, cd, the initial concentration of ammonia nitrogen was 0.5mg/L, cr, the initial concentration of ammonia nitrogen was 0.5mg/L, pb, and the initial pH was 7.
FIG. 1 is a schematic diagram of a method for synchronously recovering ammonia nitrogen and removing heavy metals by electrodialysis of wastewater in embodiment 1 of the invention. As can be seen from fig. 1, under the action of electric field force, positively charged ammonium ions and metal ions permeate through the proton exchange membrane to enter the cathode chamber; and because of the inevitable side reaction of electrolyzed water in the electrodialysis process, the cathode chamber always presents an alkaline environment, and metal ions react with a large amount of hydroxide ions after entering the cathode chamber, so that precipitation is generated, ammonia nitrogen is recovered, and heavy metals are removed. Therefore, the effluent of the anode chamber can reach the discharge standard, and the ammonia nitrogen concentrated solution in the cathode chamber has almost no heavy metal.
FIG. 2 is a graph showing the effect of removing heavy metals in the electrodialysis treatment according to example 1 of the present invention. As can be seen from fig. 2, as the electrodialysis treatment proceeds, most of the heavy metal ions in the anode compartment can be transferred to the cathode compartment; meanwhile, excessive heavy metal ions cannot be detected after electrodialysis treatment for 8 hours, so that the heavy metal ions can be immediately converted into precipitates after entering the cathode chamber. Therefore, the ammonia nitrogen concentrated solution in the cathode chamber can be recycled with reliability.
Example 2:
the method for synchronously recovering ammonia nitrogen and removing heavy metals by electrodialysis of wastewater of the invention is used for examining the influence on electrodialysis treatment results under different initial electrolyte concentrations, and basically the same as the method of the embodiment 1 is different in that: the initial concentration of the sodium sulfate solution was 60mmol/L, 75mmol/L, 100mmol/L, respectively.
FIG. 3 is a graph showing the permeation rate of ammonia nitrogen in wastewater at different initial electrolyte concentrations in example 2 of the present invention. As can be seen from fig. 3, the ammonia nitrogen transmittance is obviously inversely related to the initial electrolyte concentration, and this is attributed to the pushing effect of the electric field force, specifically: with the increase of the electrolyte concentration, the number of charges in the electrodialysis treatment system is increased, namely the conductivity of the electrodialysis treatment system is increased, the resistance is reduced, the voltage is reduced, the action of the electric field force is weakened, and the electrodialysis rate of ammonia nitrogen is correspondingly reduced.
Example 3:
the method for synchronously recovering ammonia nitrogen and removing heavy metals by electrodialysis of wastewater of the invention is used for examining the influence on electrodialysis treatment results under different pH conditions, and basically the same as the method of the embodiment 1 is different in that: the initial pH values of the wastewater containing ammonia nitrogen and heavy metals are 3, 5 and 9 respectively.
FIG. 4 is a graph showing the permeation rate of ammonia nitrogen in wastewater under different pH conditions in example 3 of the present invention. As can be seen from fig. 4, the electrodialysis rate of ammonia nitrogen at different pH is not significantly changed, but the overall trend is slightly increased in neutral meta-acidic environment. From this, it is assumed that the pH of the anode chamber always drops below 2 due to the reaction of the electrolytic water side reaction, so that the effect of pH on electrodialysis is not great. However, too high or too low a pH will result in an increased concentration of ions in the solution and a reduced voltage, which will affect the electrodialysis rate and reduce its effectiveness compared to a neutral environment.
Example 4:
the method for synchronously recovering ammonia nitrogen and removing heavy metals by electrodialysis of wastewater provided by the invention is used for examining the influence of different initial ammonia nitrogen concentrations in wastewater containing ammonia nitrogen and heavy metals on electrodialysis treatment results, and basically the same as the method in example 1, and the difference is that: the initial concentration of ammonia nitrogen in the wastewater containing ammonia nitrogen and heavy metals is 25mgN/L, 100mgN/L and 200mgN/L respectively.
FIG. 5 is a graph of the permeation rate of ammonia nitrogen in wastewater versus the initial ammonia nitrogen concentration in example 4 of the present invention. As can be seen from fig. 5, the lower the initial ammonia nitrogen concentration, the higher the ammonia nitrogen transmittance. It can also be seen from the permeation rate curve that the lower the initial ammonia nitrogen concentration, the faster the permeation rate; meanwhile, the rate at the later stage of permeation is slightly reduced compared with the initial stage, which is probably because the concentration of ions in the system is increased due to anions and cations generated by electrolyzed water at the later stage of electrodialysis treatment, the voltage is reduced, and the electrodialysis rate is reduced, which is consistent with the principle that the transmittance is slightly higher in a neutral environment.
Example 5:
the method for synchronously recovering ammonia nitrogen and removing heavy metals by electrodialysis of wastewater of the invention is used for examining the influence on electrodialysis treatment results under different current densities, and basically the same as the method of the embodiment 1 is different in that: the current densities were 2mA/cm, respectively 2 、3mA/cm 2 、4mA/cm 2 、6mA/cm 2 。
And calculating the energy consumption under different current densities according to the formula, wherein the calculation formula is as follows:
FIG. 6 is a graph showing the permeation rate of ammonia nitrogen in wastewater at different current densities in example 5 of the present invention. As can be seen from fig. 6, the ammonia nitrogen transmittance is clearly positively correlated with the current density at the same initial ammonia nitrogen concentration and pH value, which further verifies the presumption of the electric field force pushing effect during the electrodialysis treatment. Along with the increase of the current density, the voltage in the system is enhanced, the action of the electric field force is enhanced, and the electrodialysis rate of ammonia nitrogen is also increased. In addition, the higher the current density, the higher the ammonia nitrogen permeability, but the greater the energy consumption per treatment of 1 kgN.
Example 6:
the method for synchronously recovering ammonia nitrogen and removing heavy metals by electrodialysis of wastewater of the invention is used for examining the influence on electrodialysis treatment results under complex water conditions, and basically the same as the method of the embodiment 1, and the difference is that: the wastewater containing ammonia nitrogen and heavy metals is replaced byAnd (5) manganese slag percolate. In the manganese slag percolate, the initial concentration of ammonia nitrogen (NH 3-N) is 70.25mgN/L and Mg 2+ 、Ca 2 + 、Mn 2+ 、Co 2+ 、Pb 2+ The initial concentrations were 17.1501mg/L, 0.6641mg/L, 44.4531mg/L, 0.04695mg/L and 0.089mg/L, respectively.
FIG. 7 is a graph showing the effect of removing heavy metals in the electrodialysis treatment according to example 6 of the present invention. As can be seen from FIG. 7, most ammonia nitrogen and metal ions in the anode chamber can be transferred to the cathode chamber along with the progress of the reaction, and the concentration of heavy metal ions in the effluent of the anode chamber after the reaction is finished is below the national standard concentration, so that the effluent can reach the standard. Meanwhile, the content of the excessive heavy metal is not detected in the solution in the cathode chamber after the reaction is finished, so that most of metal ions are converted into sediment after entering the cathode chamber, and the ammonia nitrogen concentrated solution in the cathode chamber can be used with confidence.
Example 7:
the method for synchronously recovering ammonia nitrogen and removing heavy metals by electrodialysis of wastewater of the invention, which is disclosed by the invention, examines the influence on the electrodialysis treatment effect when different electrode materials are used as anodes, and basically has the same method as that of the embodiment 1, and the difference is that: and a platinum electrode, BDD, foam nickel and foam titanium are respectively adopted to replace a self-supporting titanium dioxide nano-mesh electrode to serve as an anode.
FIG. 8 is a graph showing the permeation rate of ammonia nitrogen in wastewater at different anodes in example 7 of the present invention. As can be seen from FIG. 8, under the same wastewater condition, the self-supporting titanium dioxide nano-electrode of the invention has much higher electrodialysis efficiency than pure foam titanium, the ammonia nitrogen in the wastewater can reach 76% within 8 hours, and the current common platinum electrode and BDD electrode at home and abroad can only reach 58% and 63% respectively. While the foam nickel electrode can achieve the electrodialysis effect similar to that of the titanium dioxide nano-mesh, the foam nickel electrode is unstable and easy to corrode and cannot be reused.
The above description is only of the preferred embodiment of the present invention, and is not intended to limit the present invention in any way. While the invention has been described in terms of preferred embodiments, it is not intended to be limiting. Any person skilled in the art can make many possible variations and modifications to the technical solution of the present invention or equivalent embodiments using the method and technical solution disclosed above without departing from the spirit and technical solution of the present invention. Therefore, any simple modification, equivalent substitution, equivalent variation and modification of the above embodiments according to the technical substance of the present invention, which do not depart from the technical solution of the present invention, still fall within the scope of the technical solution of the present invention.
Claims (10)
1. The method for synchronously recovering ammonia nitrogen and removing heavy metals by electrodialysis of wastewater is characterized by comprising the following steps of: preparing an electrodialysis system, wherein the electrodialysis system comprises an anode chamber provided with an anode and a cathode chamber provided with a cathode, a proton exchange membrane is arranged between the anode chamber and the cathode chamber, and the anode is a self-supporting titanium dioxide nano-mesh electrode; introducing wastewater containing ammonia nitrogen and heavy metal into an anode chamber of the electrodialysis system for electrodialysis treatment, enabling ammonium ions and metal ions to enter a cathode chamber through a proton exchange membrane, and reacting to remove the heavy metal and recycle the ammonia nitrogen; the preparation method of the self-supporting titanium dioxide nano-mesh electrode comprises the following steps: mixing a mixed solution of sodium hydroxide and titanium foam, wherein a solvent in the mixed solution of sodium hydroxide is water and alcohol, performing hydrothermal reaction at 100-200 ℃, washing, drying, and calcining at 400-600 ℃ to obtain the self-supporting titanium dioxide nano-mesh electrode.
2. The method for synchronously recovering ammonia nitrogen and removing heavy metals by electrodialysis of wastewater according to claim 1, wherein the initial pH value of the wastewater containing ammonia nitrogen and heavy metals is 3-12, the concentration of ammonia nitrogen in the wastewater containing ammonia nitrogen and heavy metals is 25 mgN/L-200 mgN/L, the concentration of heavy metals in the wastewater containing ammonia nitrogen and heavy metals is 0.5 mg/L-3.0 mg/L, and the heavy metals in the wastewater containing ammonia nitrogen and heavy metals comprise at least one of cadmium, chromium, lead, cobalt and manganese.
3. The method for synchronously recycling ammonia nitrogen and removing heavy metals by electrodialysis of wastewater according to claim 1, wherein electrolyte in the electrodialysis system is sodium sulfate solution, and the initial concentration of the sodium sulfate solution is 50 mmol/L-100 mmol/L.
4. The method for synchronously recovering ammonia nitrogen and removing heavy metals by electrodialysis of wastewater according to claim 1, wherein the current density in the electrodialysis system is 2mA/cm 2 ～6mA/cm 2 。
5. The method for synchronously recovering ammonia nitrogen and removing heavy metals by electrodialysis of waste water according to claim 1, wherein the foam titanium is subjected to the following pretreatment before mixing: grinding foam titanium by using sand paper with 50-200 meshes, soaking in sodium hydroxide aqueous solution for 1-2 h, then soaking in boiled oxalic acid solution for 1-2 h, and washing with water to be neutral; the mass fraction of the sodium hydroxide aqueous solution is 1-10%, and the mass fraction of the oxalic acid solution is 1-10%.
6. The method for synchronously recovering ammonia nitrogen and removing heavy metals by electrodialysis of wastewater according to claim 1, wherein the hydrothermal reaction time is 10-20 h, the calcination time is 1-2 h, and the calcination atmosphere is inert gas.
7. The method for synchronously recovering ammonia nitrogen and removing heavy metals by electrodialysis of wastewater according to any one of claims 1 to 6, characterized in that the preparation method of the mixed solution of sodium hydroxide comprises the following steps: mixing sodium hydroxide aqueous solution with ethanol, and stirring for 10-30 min to obtain a mixed solution of sodium hydroxide; the volume ratio of the sodium hydroxide aqueous solution to the ethanol is 1-10:1, and the concentration of the sodium hydroxide aqueous solution is 0.5 mol/L-5 mol/L.
8. The method for synchronously recovering ammonia nitrogen and removing heavy metals by electrodialysis of wastewater according to any one of claims 1 to 6, wherein the drying temperature is 40 ℃ to 60 ℃ and the drying time is 8 hours to 16 hours.
9. The method for synchronously recovering ammonia nitrogen and removing heavy metals by electrodialysis of wastewater according to any one of claims 1 to 6, wherein the electrodialysis treatment is carried out under normal pressure, the temperature of the electrodialysis treatment is 10 ℃ to 40 ℃, and the time of the electrodialysis treatment is 8h to 12h.
10. The method for synchronously recovering ammonia nitrogen and removing heavy metals by electrodialysis of wastewater according to any one of claims 1 to 6, wherein the cathode is a carbon felt cathode, the distance between the cathode and the anode is 8 cm-12 cm, and the facing area of the cathode and the anode is 8cm 2 ～12cm 2 。
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