CN114573201B - Device for removing heavy metals in sludge through electric coupling graphene hydrogel in situ - Google Patents

Device for removing heavy metals in sludge through electric coupling graphene hydrogel in situ Download PDF

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CN114573201B
CN114573201B CN202210420955.7A CN202210420955A CN114573201B CN 114573201 B CN114573201 B CN 114573201B CN 202210420955 A CN202210420955 A CN 202210420955A CN 114573201 B CN114573201 B CN 114573201B
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sludge
graphene
graphene hydrogel
heavy metals
hydrogel
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CN114573201A (en
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王怡
刘淼
吴鹦骏
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Jilin University
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Jilin University
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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
    • C02F11/00—Treatment of sludge; Devices therefor
    • C02F11/006—Electrochemical treatment, e.g. electro-oxidation or electro-osmosis
    • 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
    • B01J13/00—Colloid chemistry, e.g. the production of colloidal materials or their solutions, not otherwise provided for; Making microcapsules or microballoons
    • B01J13/0052—Preparation of gels
    • B01J13/0056—Preparation of gels containing inorganic material and water
    • 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
    • B01J13/00—Colloid chemistry, e.g. the production of colloidal materials or their solutions, not otherwise provided for; Making microcapsules or microballoons
    • B01J13/0052—Preparation of gels
    • B01J13/0065—Preparation of gels containing an organic phase
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/15—Nano-sized carbon materials
    • C01B32/182—Graphene
    • C01B32/184—Preparation
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/15—Nano-sized carbon materials
    • C01B32/182—Graphene
    • C01B32/194—After-treatment
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F11/00—Treatment of sludge; Devices therefor
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W10/00—Technologies for wastewater treatment
    • Y02W10/10—Biological treatment of water, waste water, or sewage

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Inorganic Chemistry (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Hydrology & Water Resources (AREA)
  • Environmental & Geological Engineering (AREA)
  • Water Supply & Treatment (AREA)
  • Materials Engineering (AREA)
  • Nanotechnology (AREA)
  • Dispersion Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Electrochemistry (AREA)
  • Treatment Of Sludge (AREA)

Abstract

The invention discloses a device for removing sludge heavy metals in situ by electrically-coupled graphene hydrogel. The process for removing heavy metals in the sludge by the device comprises the following steps: step one, preparing graphene oxide; step two, preparing graphene hydrogel; step three, sludge pretreatment is carried out to obtain a sludge sample with the water content of 30% -50% and the pH value of less than 7; fixing a graphene hydrogel fixing device and preparing an electrolytic tank; and fifthly, electrifying for 5h under the condition that the potential gradient is 0.5-1.5V/cm. The beneficial effects are that: shortening the treatment time, increasing the conductivity efficiency, reducing the energy consumption and improving the effect of removing the heavy metals in the sludge.

Description

Device for removing heavy metals in sludge through electric coupling graphene hydrogel in situ
Technical Field
The invention relates to a device for removing heavy metals in sludge in situ by electrically coupling graphene hydrogel and a process for removing the heavy metals in the sludge in situ by using the device, in particular to graphene, a graphene hydrogel and a preparation method thereof.
Background
In recent years, with the increase of population, the improvement of living standard and the promotion of industrial development, the discharge amount of urban industrial wastewater and domestic sewage is greatly increased, and the discharge amount of sludge is also increased. At present, a large number of students throw into the treatment of urban and industrial wastewater at home and abroad, and compared with the research of sewage, the research of sludge is relatively less. For the problem of heavy metal pollution that can exist in both industrial sludge and domestic sewage sludge, because the treatment of sludge has more heavy metal species in the sludge, and the existence form of heavy metal in the sludge also has multiple existence forms, this can increase the degree of difficulty of handling heavy metal in the sludge, and improper treatment can cause secondary pollution to the environment. And the poor fluidity of the sludge causes the transportation and treatment of the sludge to be difficult and a great deal of resource consumption is caused. The treatment method of heavy metals in the sludge at the present stage comprises a chemical method, a biological treatment technology, a heat treatment technology and an electrodynamic remediation technology.
The heavy metals in the sludge are treated by a chemical method, and are usually converted into a soluble state by changing the pH value of the sludge or are converted into a complex form by adding a complexing agent, a chelating agent and a surfactant, and then are separated and removed from the sludge; the precondition of using a chemical method to treat the heavy metals in the sludge is ectopic repair, if the heavy metals in the sludge are repaired in situ, the dosage of chemical reagents can not be reasonably controlled, the sludge is secondary pollution, and the recycling of the sludge is not facilitated. The biological treatment technology mainly adopts specific biological metabolism to move, absorb and transform heavy metals in the sludge, and has the advantages of longer experimental period and too high requirement on the sludge per se although the biological treatment technology has higher environmental friendliness, and pretreatment is needed before treatment. The heat treatment technology is mainly used for removing heavy metals in the sludge by raising the temperature of the sludge and carrying out migration and conversion on a plurality of inorganic elements at 150-400 ℃, and the heat treatment technology not only consumes a large amount of resources, but also has the problem that the treated sludge is not suitable for secondary utilization.
The electrokinetic remediation treatment technology is that heavy metals in the sludge are migrated and converted in the sludge and removed from the sludge through electrokinetic effects such as electromigration, electroosmosis and electrophoresis under the action of an electric field, so that ex-situ treatment can be realized and in-situ treatment can be realized. However, the existing electrokinetic remediation technology still has the problems of long treatment period and large energy consumption, while the existing electrokinetic remediation technology is used in combination with various technologies, most of the electrokinetic remediation technology is used in combination with chemical reagents such as complexing agents, chelating agents and the like, and the migration effect and the complexing and fixing effect of heavy metals from sludge can be improved, but specific complexing agents or other chemical reagents are only associated with single metal ions or metal ions of a plurality of types, so that the problem of secondary pollution possibly caused in situ treatment of the heavy metals in the sludge still cannot be solved well. In addition, in the treatment process, at least three to four days are needed for treating the sludge to the agricultural standard, and even a plurality of weeks are needed for treatment, so that the problem of long treatment time and high treatment energy consumption caused by long treatment time are solved.
Disclosure of Invention
The invention aims to solve a plurality of problems existing in the treatment of the existing electrodynamic force repair technology and provides a device for removing heavy metals in sludge by using electrically coupled graphene hydrogel in situ.
The invention aims to provide a device for combining in-situ oxidation removal of heavy metals in sludge and adsorption of heavy metals in sludge by graphene hydrogel by electric restoration aiming at heavy metal sludge with complex components and low water content, and a method for removing heavy metals in sludge by using the device, and the device has the characteristics of environmental protection, low cost, short time and high efficiency.
The invention provides graphene and a preparation method of graphene hydrogel, which comprises the following steps:
step one, preparation of graphene and a solution thereof: adding graphite into a mixed solution of concentrated sulfuric acid and concentrated phosphoric acid, wherein the volume ratio of the sulfuric acid to the phosphoric acid solution is 9:1, the liquid-solid mass ratio of the mixed solution of the concentrated sulfuric acid and the concentrated sulfuric acid to the graphite is 110:1, carrying out ice bath for 30min at the temperature below 10 ℃, and stirring at the speed of 1000rmp/min-2000 rmp/min; adding potassium permanganate into the stirred liquid mixture after 30min, wherein the mass ratio of the solid to the liquid of the potassium permanganate to the graphite is 3:1, continuously stirring in the process, and continuously stirring for 1h at the stirring speed and at the stirring temperature after adding; after 1h, the mixed solution is heated to 50 ℃ and continuously stirred for reaction for 12h; adding a small amount of 3% hydrogen peroxide solution into the liquid mixture after the reaction is finished to make the solution golden yellow, slightly stirring, standing, centrifuging for 5min at a centrifugal speed of 10000rpm/min after the solution is stable, washing the lower precipitate for 3-5 times by using 1mol/L hydrochloric acid solution, and removing soluble divalent manganese ions; washing the lower layer precipitate with deionized water until the upper layer solution is neutral; and drying the precipitate to constant weight at 50 ℃, grinding, and sieving with a 100-mesh sieve to obtain graphene. And adding a certain amount of graphene into deionized water, wherein the concentration of the graphene solution is 0.5g/L.
Step two, preparing graphene hydrogel: adding acrylic acid, acrylamide, sodium hydroxide and N '-N-methylene bisacrylamide into the graphene solution in the first step, wherein the mass ratio of the graphene aqueous solution to the acrylic acid, the sodium hydroxide, the acrylamide and the N, N' -methylene bisacrylamide is 625:225:100:55:1, shaking and mixing the mixture into a uniform solution, placing the solution under the condition of 45 ℃, adding potassium persulfate, at the moment, shaking and dissolving the mixture before adding the mixture into the solution to the mass ratio of the potassium persulfate to be 300:1, heating the mixture to 50 ℃, carrying out polymerization reaction for 6 hours under the condition of 50 ℃, washing the surface of the obtained solid by deionized water, drying the solid to constant weight at the temperature of 50 ℃, grinding the solid, and sieving the solid through a 100-mesh sieve to obtain the graphene hydrogel.
The device for removing heavy metals in sludge by electrically coupling graphene hydrogel in situ comprises the following steps:
(1) Pretreatment of sludge: sieving the wet sludge sample with a 10-mesh sieve to remove large particles such as stones, pretreating with 3% sodium nitrate by mass fraction to obtain sludge with pH less than 7 and water content of 30% -50%, and storing for later use;
(2) Loading into an electrolytic cell: respectively fixing graphite electrodes between a cathode electrolytic cell and an anode electrolytic cell, wherein the cathode electrolytic cell and the anode electrolytic Chi Junyou are composed of graphite electrodes and porous separators; uniformly dispersing and fixing graphene hydrogel in the middle of a double-layer 800-mesh filter cloth, fixing the graphene hydrogel in the position contacted with a solution and the position contacted with the solution around the filter cloth by using an organic glass pressing plate to obtain a hydrogel fixing device, and fixing the hydrogel fixing device in an electrolytic tank, wherein the ratio of the hydrogel fixing device to the cathode electrolytic tank to the anode electrolytic tank is 1:1; placing the pretreated sludge between an anode electrolytic cell and a graphene hydrogel fixing device and uniformly pressing; injecting electrolyte between the cathode electrolytic cell and the graphene hydrogel fixing device, wherein the electrolyte is 3% sodium nitrate solution by mass fraction;
(3) And (3) electrifying: the current was applied for 5 hours at a potential gradient of 0.5V/cm to 1.5V/cm.
The invention couples the electric repair technology with the adsorption of graphene hydrogel. On one hand, the electric action in the electric repairing technology can strengthen the migration of ions; on the other hand, the graphene hydrogel can effectively intercept and absorb heavy metal ions in a migration route of heavy metal cations for strengthening migration between sludge and a cathode electrolytic cell.
The invention has the advantages that:
the invention is coupled by adopting the methods of electric repair and graphene hydrogel adsorption, and the significance of adopting the graphene hydrogel is as follows: 1. the acrylic acid acrylamide hydrogel has an adsorption effect on heavy metals, and the doped graphene in the acrylic acid acrylamide hydrogel can improve the repair effect of the hydrogel on heavy metals; 2. the graphene doped in the hydrogel can improve the conductivity of the hydrogel, so that the conductivity effect in the electrolytic cell is improved, the load of electric repair is reduced, and the migration effect of heavy metal ions is improved.
Not only solves the problem of difficult migration of heavy metal ions in sludge, but also improves the adsorption effect of graphene hydrogel, reduces the workload of an electric repair method, and improves the repair effect of heavy metals in sludge.
The invention does not need to add chelating agent, strong oxidant, surfactant and the like, and has the characteristics of green and environment protection.
Drawings
Fig. 1 is a schematic structural diagram of an apparatus for in-situ removal of sludge heavy metals by electrically coupled graphene hydrogel.
The labels in the above figures are as follows:
1. Ammeter 2, DC power supply 3, anode graphite plate 4, cathode graphite plate 5 and anode chamber
6. Cathode chamber 7, graphene hydrogel fixing device 8, electrolyte 9 and sludge
10. Porous separator 11, porous separator.
Detailed Description
The technical scheme of the invention is not limited to the following specific embodiments, and also includes any combination of the specific embodiments.
In the specific embodiment, the process of removing the heavy metal in the sludge in the device for removing the heavy metal in the sludge by electrically coupling the graphene hydrogel in situ is carried out according to the following steps:
Step one, graphene oxide solution preparation: preparing an ice water bath, and stirring the 200-mesh-sieved graphite powder in a mixed solution of concentrated sulfuric acid and concentrated phosphoric acid in the water bath at a speed of 1000rmp/min-2000rmp/min for 30min under the condition that the temperature is lower than 10 ℃ and the liquid-solid mass ratio of the mixed solution to the graphite powder is 110:1, wherein the volume ratio of the sulfuric acid to the phosphoric acid is 9:1; after stirring, adding potassium permanganate into the mixed liquid, wherein the mass ratio of the potassium permanganate solid to the graphite powder is 3:1, the fusion of the potassium permanganate solid and the liquid mixture is ensured as much as possible, and the system temperature is kept to be not more than 10 ℃ in the adding process; after the adding, adding a sealing treatment on the top of the container, and keeping the temperature and the stirring speed for continuously stirring for 1h; after the stirring for 1h is finished, heating the mixed solution to 50 ℃ and stirring for 12h at the stirring speed; dropwise adding 3% hydrogen peroxide solution into the fully reacted liquid mixture to enable the mixture to generate reaction bubbles and to be golden yellow, stopping dropwise adding and standing until the reaction bubbles and color change are not generated during dropwise adding again, and slightly stirring; after the liquid mixture is stable, centrifuging for 5min at a centrifugal speed of 10000rmp/min, removing the upper layer solution after centrifuging, reserving the lower layer sediment, carrying out washing on the lower layer sediment for 3-5 times by adding 1mol/L hydrochloric acid solution, and removing soluble divalent manganese ions; washing the lower precipitate by using deionized water after washing by hydrochloric acid until the centrifuged upper solution is neutral; drying the precipitate at 50 ℃ until the weight of the precipitate is constant, grinding, and sieving with a 100-mesh sieve to obtain graphene oxide powder; the graphene oxide powder was formulated as a 0.5g/L graphene oxide solution using deionized water, and the graphene oxide powder was completely dissolved using ultrasonic vibration.
Step two, graphene hydrogel is prepared by adding acrylic acid, acrylic acid amine, sodium hydroxide and N 'N-methylene bisacrylamide into a graphene solution prepared in advance, mixing the graphene aqueous solution, the acrylic acid, the sodium hydroxide, the acrylamide and the N, N' -methylene bisacrylamide into a uniform solution according to the mass ratio of 625:225:100:55:1, shaking the uniform solution, placing the mixed solution at 45 ℃ after the mixed solution reaches 45 ℃, adding potassium persulfate powder, adding the mixed solution and the potassium persulfate according to the mass ratio of 300:1, shaking the mixed solution until the mixed solution is completely dissolved, raising the system temperature to 50 ℃, and continuously performing polymerization reaction for 6h under the condition of 50 ℃; and (3) washing the surface of the obtained polymer with deionized water for 6 hours to remove the part of the surface of the polymer, which is not subjected to polymerization reaction, drying the polymer to constant weight at 50 ℃ after washing, grinding and sieving with a 100-mesh sieve to obtain graphene hydrogel powder.
Step three, sludge pretreatment: and (3) sieving the wet sludge sample to be treated through a 10-mesh sieve to remove larger particles such as stones, pretreating with a sodium nitrate solution with the mass fraction of 3% or a dilute nitric acid solution with the mass fraction of 5%, and stirring the wet sludge sample for 0.5h by a stirring paddle at the rotating speed of 150rmp/min to obtain a sludge sample with the water content of 30-50%, wherein the pH value of the sludge sample is less than 7.
Step four, configuring an electrolytic cell: as shown in fig. 1, graphite electrodes smoothed by sanding are fixed in the middle of the cathode electrolytic cell 6 and the anode electrolytic cell 5, respectively; uniformly dispersing and fixing graphene hydrogel in the middle of a double-layer 800-mesh filter cloth, and fixing the graphene hydrogel in a position contacted with a solution around the filter cloth by using an organic glass plate to obtain a graphene oxide hydrogel fixing device 7, and fixing the graphene oxide hydrogel fixing device in an electrolytic tank, wherein the distance ratio of the graphene oxide hydrogel fixing device to an anode electrolytic cell to a cathode electrolytic cell is 1:1; uniformly placing the pretreated sludge sample into a sludge pond S1 in the middle of a graphene oxide-free hydrogel fixing device of an anode electrolytic cell, and uniformly pressing; the sodium nitrate solution with the mass fraction of 3% is put into an electrolytic cell S2 between a cathode electrolytic cell 6 and a graphene oxide hydrogel home fixing device 7; the anode graphite plate 3 is electrified with the anodes of the ammeter 1 and the power supply 2, and the cathode graphite plate 4 is electrified with the cathodes of the power supply 2, so that the configuration of the electrolytic tank is completed.
Step five, electrifying: the current was applied to the substrate for 5 hours at a potential gradient of 0.5V/cm.
According to the method, the electric restoration and the graphene hydrogel adsorption are coupled, in the process of electrically restoring heavy metals, the ion reinforcement migration and the graphene hydrogel adsorption are coupled in the electric restoration, and as the migration effect of heavy metal ions is reinforced in the electric restoration process, the heavy metal ions in migration can be adsorbed by introducing the graphene hydrogel in the process of a metal ion migration path, and the heavy metals in sludge are removed under the actions of the electric restoration and the hydrogel adsorption. According to the method, heavy metal ions in sludge interstitial fluid are under the action of an electric field and a gravity field at the same time, newton mechanical stress analysis shows that the migration route of the heavy metal ions in the sludge is parabolic, so that along with the extension of electric repair time, the heavy metal ions in the sludge interstitial fluid can move to the middle lower part of a sludge tank and can gather below the junction of graphene hydrogel and the sludge tank, the concentration of the heavy metal ions in the sludge tank is far higher than that of the heavy metal ions in an electrolytic tank according to the diffusion principle, and the heavy metal ions in the sludge directionally move to the electrolytic tank. Under the action of electric field force and diffusion, migration of heavy metal ions in the sludge is promoted. The graphene hydrogel is introduced in the electric repairing process, so that heavy metal ions in migration can be adsorbed, the graphene is doped in the hydrogel, the adsorption performance of the hydrogel is improved, the conductivity of a system is increased, the load of electric repairing is reduced, the migration effect of the electric repairing is improved, and the migration effect of the heavy metal ions is improved.
In the second embodiment, the difference between the present embodiment and the first embodiment is that the potential gradient in the fifth step is 1V/cm. The other is the same as in the first embodiment.
In the second embodiment, the difference between the present embodiment and the first embodiment is that the potential gradient in the fifth step is 1.5V/cm. The other is the same as in the first embodiment.
Actual implementation one and data:
(1) Pretreatment of sludge: 400ml of large-particle factory sludge is removed, 5% of dilute nitric acid by mass fraction is added, and the mixture is stirred for 0.5h by a stirring paddle at the rotating speed of 150rmp/min to perform pretreatment, wherein the water content after treatment is 34%, and the initial pH value is 6.
(2) Fixing the graphene oxide hydrogel fixing device in an electrolytic tank, putting the sludge pretreated in the step (1) into a sludge chamber, adding 400ml of sodium nitrate with mass fraction of 3% into the electrolytic chamber, and uniformly pressing.
(3) And (3) electrifying: the current was applied for 5 hours under a potential gradient of 0.5V/cm.
Through analysis and test, the method provided by the invention has the advantages that the removal rate of heavy metal Cu in the sludge is 42%, the removal rate of Pb is 59%, and the removal rate of Cr is 39%, and the treated sludge meets the agricultural standards of sludge in China.
Actual implementation two and data:
(1) Pretreatment of sludge: 400ml of large-particle factory sludge is removed, 5% of dilute nitric acid by mass fraction is added, and the mixture is stirred for 0.5h by a stirring paddle at the rotating speed of 150rmp/min to perform pretreatment, wherein the water content after treatment is 37%, and the initial pH value is 6.
(2) Fixing the graphene oxide hydrogel fixing device in an electrolytic tank, putting the sludge pretreated in the step (1) into a sludge chamber, adding 400ml of sodium nitrate with mass fraction of 3% into the electrolytic chamber, and uniformly pressing.
(3) And (3) electrifying: the current was applied for 5 hours under a potential gradient of 1V/cm.
Through analysis and test, the method provided by the invention has the advantages that the removal rate of heavy metal Cu in the sludge is 48%, the removal rate of Pb is 67%, and the removal rate of Cr is 51%, and the treated sludge meets the agricultural standards of sludge in China.
Actual implementation three and data:
(1) Pretreatment of sludge: 400ml of large-particle factory sludge is removed, 5% of dilute nitric acid by mass fraction is added, and the mixture is stirred for 0.5h by a stirring paddle at the rotating speed of 150rmp/min to perform pretreatment, wherein the water content after treatment is 34%, and the initial pH value is 6.
(2) Fixing the graphene oxide hydrogel fixing device in an electrolytic tank, putting the sludge pretreated in the step (1) into a sludge chamber, adding 400ml of sodium nitrate with mass fraction of 3% into the electrolytic chamber, and uniformly pressing.
(3) And (3) electrifying: the current was applied for 5 hours under a potential gradient of 1.5V/cm.
Through analysis and test, the method provided by the invention has the advantages that the removal rate of heavy metal Cu in the sludge is 64%, the removal rate of Pb is 84%, and the removal rate of Cr is 55%, and the treated sludge meets the agricultural standards of sludge in China.

Claims (7)

1. The device comprises an electric system and a graphene hydrogel fixing device, wherein the electric system comprises a sludge tank, an electrolytic tank, a cathode electrolytic cell, an anode electrolytic cell and the graphene hydrogel fixing device, wherein the cathode electrolytic cell, the anode electrolytic cell and the graphene hydrogel fixing device are positioned at two ends of the electric system; the preparation method is characterized in that the preparation of the graphene hydrogel fixing device is carried out according to the following steps:
step one, graphene preparation: adding graphite into a mixed solution of concentrated sulfuric acid and concentrated phosphoric acid, wherein the volume ratio of the sulfuric acid to the phosphoric acid is 9:1, the liquid-solid mass ratio of the mixed solution of the concentrated sulfuric acid and the concentrated phosphoric acid to the graphite is 110:1, stirring and reacting for 30min at the speed of 1000rmp/min-2000rmp/min under the condition that the temperature is below 10 ℃, adding potassium permanganate into the mixed solution for stirring and reacting, the mass ratio of the potassium permanganate to the graphite is 3:1, continuously stirring for 1h at the stirring speed and the temperature, and stirring and reacting the mixed solution for 12h at the temperature of 50 ℃; adding deionized water and hydrogen peroxide into the mixed solution, slightly stirring uniformly, standing, centrifuging for 5min at a centrifugal speed of 10000rpm/min by using 1mol/L hydrochloric acid and deionized water, removing soluble divalent manganese ions, washing solid precipitate to be neutral in the upper layer solution, drying the solid precipitate at 50 ℃, grinding, and sieving with a 100-mesh sieve to obtain graphene;
Step two, preparing a graphene aqueous solution: adding graphene in the step one into deionized water, wherein the concentration of a graphene aqueous solution is 0.5g/L;
Step three, preparation of graphene hydrogel: adding acrylic acid, acrylamide, sodium hydroxide and N, N '-methylene bisacrylamide into the graphene aqueous solution in the second step, mixing the graphene aqueous solution with the acrylic acid, sodium hydroxide, acrylamide and N, N' -methylene bisacrylamide in a mass ratio of 625:225:100:55:1 to obtain a uniform solution, adding potassium persulfate at 45 ℃, adding the mass ratio of a liquid mixture to the potassium persulfate before adding to be 300:1, reacting for 6 hours at the temperature of 50 ℃, washing the obtained solid with deionized water, drying, grinding, and sieving with a 100-mesh sieve to obtain graphene hydrogel;
Step four, manufacturing a graphene hydrogel fixing device: uniformly dispersing and fixing graphene hydrogel in the middle of a double-layer 800-mesh filter cloth, fixing the graphene hydrogel with an organic glass pressing plate around the filter cloth at a position contacted with the solution to obtain a hydrogel fixing device, and combining the hydrogel fixing device with an electric system to form an electric coupling graphene hydrogel in-situ sludge heavy metal removing device.
2. The device for in-situ removal of sludge heavy metals by electrically coupled graphene hydrogel according to claim 1, wherein a cathode electrolytic cell, an anode electrolytic Chi Junyou graphite electrode and a porous separator in an electric system are formed.
3. The device for removing heavy metals from sludge in situ by electrically coupling graphene hydrogel according to claim 1 or 2, wherein the graphene hydrogel fixing device is positioned in the electrolytic cell at a distance ratio of 1:1 between the graphene hydrogel and the cathode electrolytic cell and between the graphene hydrogel and the anode electrolytic cell.
4. An apparatus for in situ removal of heavy metals from sludge using an electrically coupled graphene hydrogel according to any one of claims 1-3, wherein the process for removing heavy metals from sludge is characterized by comprising the steps of:
step one, sludge pretreatment: sieving the wet sludge sample with a 10-mesh sieve to remove large particles such as stones; pretreating with 3% sodium nitrate solution or 5% dilute nitric acid solution to make pH of sludge less than 7 and water content 30% -50%;
Step two, loading into an electrolytic tank: placing the pretreated sludge between an anode electrolytic cell and a graphene hydrogel fixing device, uniformly pressing, and injecting electrolyte between a cathode point electrolytic cell and the graphene hydrogel fixing device, wherein the electrolyte is sodium nitrate solution with the mass fraction of 3%;
step three, electrifying: the current was applied for 5 hours at a potential gradient of 0.5V/cm to 1.5V/cm.
5. The device for in-situ removal of heavy metals from sludge by electrically coupled graphene hydrogel as in claim 4, wherein the process for removing heavy metals from sludge is characterized by a potential gradient of 0.5V/cm when energized in step three.
6. The device for in-situ removal of heavy metals from sludge by electrically coupled graphene hydrogel as in claim 4, wherein the process for removing heavy metals from sludge is characterized by a potential gradient of 1V/cm when energized in step three.
7. The device for in-situ removal of heavy metals from sludge by electrically coupled graphene hydrogel as claimed in claim 4, wherein the process of removing heavy metals from sludge is characterized by a potential gradient of 1.5V/cm when energized in step three.
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Citations (5)

* Cited by examiner, † Cited by third party
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