CN117776467A - Electrochemical reaction device and method for recycling phosphorus in sludge - Google Patents
Electrochemical reaction device and method for recycling phosphorus in sludge Download PDFInfo
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- CN117776467A CN117776467A CN202311809230.8A CN202311809230A CN117776467A CN 117776467 A CN117776467 A CN 117776467A CN 202311809230 A CN202311809230 A CN 202311809230A CN 117776467 A CN117776467 A CN 117776467A
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- 239000010802 sludge Substances 0.000 title claims abstract description 76
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 title claims abstract description 33
- 229910052698 phosphorus Inorganic materials 0.000 title claims abstract description 33
- 239000011574 phosphorus Substances 0.000 title claims abstract description 33
- 238000000034 method Methods 0.000 title claims abstract description 30
- 238000003487 electrochemical reaction Methods 0.000 title claims abstract description 16
- 238000004064 recycling Methods 0.000 title claims abstract description 9
- 238000011084 recovery Methods 0.000 claims description 98
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 32
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 claims description 31
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 claims description 20
- 229910052984 zinc sulfide Inorganic materials 0.000 claims description 17
- 229910052757 nitrogen Inorganic materials 0.000 claims description 16
- 235000003891 ferrous sulphate Nutrition 0.000 claims description 15
- 239000011790 ferrous sulphate Substances 0.000 claims description 15
- 229910000359 iron(II) sulfate Inorganic materials 0.000 claims description 15
- 238000002386 leaching Methods 0.000 claims description 12
- 239000003011 anion exchange membrane Substances 0.000 claims description 9
- 239000007788 liquid Substances 0.000 claims description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 8
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 7
- 238000001914 filtration Methods 0.000 claims description 7
- 239000011268 mixed slurry Substances 0.000 claims description 7
- 229910052760 oxygen Inorganic materials 0.000 claims description 7
- 239000001301 oxygen Substances 0.000 claims description 7
- 238000003756 stirring Methods 0.000 claims description 7
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 claims description 6
- 238000011065 in-situ storage Methods 0.000 claims description 6
- 239000012528 membrane Substances 0.000 claims description 6
- 238000002425 crystallisation Methods 0.000 claims description 5
- 230000005684 electric field Effects 0.000 claims description 5
- 230000009471 action Effects 0.000 claims description 4
- 238000005341 cation exchange Methods 0.000 claims description 4
- 230000008025 crystallization Effects 0.000 claims description 4
- 239000008151 electrolyte solution Substances 0.000 claims description 4
- 239000007787 solid Substances 0.000 claims description 4
- 238000005868 electrolysis reaction Methods 0.000 claims description 3
- 238000005086 pumping Methods 0.000 claims description 3
- 230000001360 synchronised effect Effects 0.000 claims description 3
- 230000007613 environmental effect Effects 0.000 claims description 2
- 125000002887 hydroxy group Chemical group [H]O* 0.000 claims description 2
- RUTXIHLAWFEWGM-UHFFFAOYSA-H iron(3+) sulfate Chemical compound [Fe+3].[Fe+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O RUTXIHLAWFEWGM-UHFFFAOYSA-H 0.000 claims description 2
- 229910000360 iron(III) sulfate Inorganic materials 0.000 claims description 2
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 claims 3
- 230000008901 benefit Effects 0.000 abstract description 4
- 230000008569 process Effects 0.000 abstract description 3
- 239000002699 waste material Substances 0.000 abstract description 3
- 239000010865 sewage Substances 0.000 abstract description 2
- 238000009270 solid waste treatment Methods 0.000 abstract 1
- SURQXAFEQWPFPV-UHFFFAOYSA-L iron(2+) sulfate heptahydrate Chemical compound O.O.O.O.O.O.O.[Fe+2].[O-]S([O-])(=O)=O SURQXAFEQWPFPV-UHFFFAOYSA-L 0.000 description 17
- 239000000047 product Substances 0.000 description 6
- 239000000243 solution Substances 0.000 description 6
- 239000000126 substance Substances 0.000 description 6
- 229910019142 PO4 Inorganic materials 0.000 description 5
- 239000010452 phosphate Substances 0.000 description 5
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 4
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 4
- HJPBEXZMTWFZHY-UHFFFAOYSA-N [Ti].[Ru].[Ir] Chemical compound [Ti].[Ru].[Ir] HJPBEXZMTWFZHY-UHFFFAOYSA-N 0.000 description 4
- 238000005265 energy consumption Methods 0.000 description 4
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 3
- 239000003513 alkali Substances 0.000 description 3
- 238000002848 electrochemical method Methods 0.000 description 3
- 229940085991 phosphate ion Drugs 0.000 description 3
- 235000002639 sodium chloride Nutrition 0.000 description 3
- ILRRQNADMUWWFW-UHFFFAOYSA-K aluminium phosphate Chemical compound O1[Al]2OP1(=O)O2 ILRRQNADMUWWFW-UHFFFAOYSA-K 0.000 description 2
- 239000002585 base Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 239000004566 building material Substances 0.000 description 2
- 238000012512 characterization method Methods 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- YADSGOSSYOOKMP-UHFFFAOYSA-N dioxolead Chemical compound O=[Pb]=O YADSGOSSYOOKMP-UHFFFAOYSA-N 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000007772 electrode material Substances 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000007654 immersion Methods 0.000 description 2
- 229910052742 iron Inorganic materials 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 239000011780 sodium chloride Substances 0.000 description 2
- VWDWKYIASSYTQR-UHFFFAOYSA-N sodium nitrate Chemical compound [Na+].[O-][N+]([O-])=O VWDWKYIASSYTQR-UHFFFAOYSA-N 0.000 description 2
- 239000010936 titanium Substances 0.000 description 2
- 229910052719 titanium Inorganic materials 0.000 description 2
- 239000005955 Ferric phosphate Substances 0.000 description 1
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 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
- 238000002441 X-ray diffraction Methods 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 238000005273 aeration Methods 0.000 description 1
- AZDRQVAHHNSJOQ-UHFFFAOYSA-N alumane Chemical class [AlH3] AZDRQVAHHNSJOQ-UHFFFAOYSA-N 0.000 description 1
- CKMXBZGNNVIXHC-UHFFFAOYSA-L ammonium magnesium phosphate hexahydrate Chemical compound [NH4+].O.O.O.O.O.O.[Mg+2].[O-]P([O-])([O-])=O CKMXBZGNNVIXHC-UHFFFAOYSA-L 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 159000000007 calcium salts Chemical class 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000003814 drug Substances 0.000 description 1
- 238000000724 energy-dispersive X-ray spectrum Methods 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 238000012851 eutrophication Methods 0.000 description 1
- 229940032958 ferric phosphate Drugs 0.000 description 1
- 229910001385 heavy metal Inorganic materials 0.000 description 1
- AEIXRCIKZIZYPM-UHFFFAOYSA-M hydroxy(oxo)iron Chemical compound [O][Fe]O AEIXRCIKZIZYPM-UHFFFAOYSA-M 0.000 description 1
- 239000003014 ion exchange membrane Substances 0.000 description 1
- WBJZTOZJJYAKHQ-UHFFFAOYSA-K iron(3+) phosphate Chemical compound [Fe+3].[O-]P([O-])([O-])=O WBJZTOZJJYAKHQ-UHFFFAOYSA-K 0.000 description 1
- 229910000399 iron(III) phosphate Inorganic materials 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- 239000002686 phosphate fertilizer Substances 0.000 description 1
- 239000002367 phosphate rock Substances 0.000 description 1
- 230000010287 polarization Effects 0.000 description 1
- OTYBMLCTZGSZBG-UHFFFAOYSA-L potassium sulfate Chemical compound [K+].[K+].[O-]S([O-])(=O)=O OTYBMLCTZGSZBG-UHFFFAOYSA-L 0.000 description 1
- 229910052939 potassium sulfate Inorganic materials 0.000 description 1
- 235000011151 potassium sulphates Nutrition 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 239000010801 sewage sludge Substances 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 239000004317 sodium nitrate Substances 0.000 description 1
- 235000010344 sodium nitrate Nutrition 0.000 description 1
- 229910052938 sodium sulfate Inorganic materials 0.000 description 1
- 235000011152 sodium sulphate Nutrition 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 229910052567 struvite Inorganic materials 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 239000013589 supplement Substances 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
Landscapes
- Manufacture And Refinement Of Metals (AREA)
Abstract
The invention belongs to the field of solid waste treatment, and provides an electrochemical reaction device and method for recycling phosphorus in sludge. The process equipment provided by the invention has the advantages of simple structure and strong operability, is suitable for waste sludge reduction and resource treatment of various sewage treatment plants, and can realize intelligent automation and large-scale application.
Description
Technical Field
The invention belongs to the technical field of recovery of phosphorus in polyaluminium chloride sludge, and particularly relates to an electrochemical reaction device and method for recovering phosphorus in sludge at a high value in situ.
Background
High grade phosphate rock reserves in the world are currently being consumed in large quantities, and excessive discharge of phosphorus in water bodies causes eutrophication, which causes serious resource shortage and environmental pollution problems. At present, a physical and chemical method such as adding polyaluminium chloride and the like is widely adopted in all places to strengthen the phosphorus-containing sewage treatment technology, so that a large amount of phosphorus-rich sludge to be treated urgently is generated. The phosphorus-containing sludge is used as sustainable resource supplement of high-grade phosphate ores, and has great unique advantages. Compared with waste activated sludge, the waste activated sludge contains fewer organic elements and simpler chemical components, and is more beneficial to recycling compared with sewage sludge ash due to lower metal content, so that a high-purity product is produced. The recovery of phosphorus from polyaluminum chloride sludge has significant benefits in terms of controlling phosphorus pollution and resource economy.
The current phosphorus-containing sludge treatment method mainly comprises a sludge landfill method, a sludge incineration method, a building material method, a wet chemical method, an electrochemical method and the like. The energy required by sludge landfill, incineration and building material formation is less, the flow is simple, but a large amount of resources such as phosphorus in the sludge are not fully recycled, and the sludge with high heavy metal content such as polyaluminium chloride and the like can cause secondary harm to the environment. Ferric phosphate, struvite, wurtzite and the like generated by chemical crystallization are recognized as resources with high recovery value in sludge, but a wet chemical method needs to add precipitants such as calcium salt, aluminum salt, ferric salt and the like, and meanwhile, a large amount of acid and alkali are added to ensure a proper pH environment, so that the process is complex and the cost is high.
The invention utilizes an electrochemical method to treat the phosphorus-containing sludge, realizes the efficient leaching of phosphorus and synchronous recovery of the crystalline wustite through cathode water electrolysis in-situ alkali production, and has low energy consumption and good effect.
Disclosure of Invention
Aiming at the technical requirements of phosphorus recovery in sludge, the invention provides an electrochemical method which does not need acid-base agents, has simple operation equipment and obvious economic benefit and is used for phosphorus recovery of polyaluminium chloride sludge in order to overcome the defects of high cost, complex agent transportation and flow and the like in the existing sludge recycling treatment technology.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
the invention provides an electrochemical reaction device and a method for simultaneously leaching, crystallizing and recycling phosphorus in sludge, wherein the technical principle is as shown in figure 1: the three-chamber electrochemical system for directly releasing phosphate ions at the cathode is provided by organically combining the cathode function of an electrochemical reaction device, the property of an ion exchange membrane, the leaching of aluminum phosphate and a crystallization mechanism of wustite, and the resource recovery of leached phosphorus is carried out by using a crystallization method. After application of an external electric field, the cathode is used to electrolyze aqueous hydroxyl radicals to create a strongly alkaline environment. On one hand, aluminum phosphate in the sludge releases phosphate ions in an alkaline environment and migrates into a recovery chamber under the action of an electric field; on the other hand, phosphate ions react with ferrous sulfate under the condition of the partial neutrality of the recovery chamber to generate blue iron ore, thereby realizing the high-value recovery of phosphorus in the sludge.
The invention firstly provides an electrochemical reaction device for recycling phosphorus in sludge, which comprises a sludge tank, a nitrogen bottle, a direct current power supply and an electrolytic cell; the electrolytic cell is sequentially provided with an anode chamber, a recovery chamber and a cathode chamber; an anode and a cathode are inserted into the anode chamber and the cathode chamber, respectively.
Further, the direct current power supply is connected with an anode and a cathode in the electrolytic cell through a lead to supply power for the electrochemical reaction device, and the voltage and the current intensity can be adjusted.
Further, the discharge port of the sludge tank is connected to the water inlet of the electrolytic cell at the bottom of the cathode chamber through a sludge pump, and the sludge inlet amount can be adjusted according to requirements.
Further, mechanical agitators are respectively arranged in the sludge tank, the recovery chamber and the cathode chamber, and the immersion depth and the rotating speed of the mechanical agitators are adjustable.
Further, the nitrogen cylinder is connected to the recovery chamber, and the recovery chamber is continuously aerated by controlling the flow rate of nitrogen.
Further, the cathode chamber and the recovery chamber are partitioned by an anion exchange membrane, the recovery chamber and the anode chamber are partitioned by a cation exchange membrane, and the membranes are fixed by two gaskets.
Further, the cathode and anode electrode materials include, but are not limited to, titanium mesh, titanium ruthenium iridium electrode, lead dioxide electrode, and the like. The morphology of the electrode material includes, but is not limited to, mesh, sheet, vertical column, etc. Vertical columns include, but are not limited to, cylinders, square columns, triangular columns, and the like. Preferably, the anode is a titanium ruthenium iridium electrode, the cathode is a titanium electrode, and the electrode is immersed in the chamber.
The invention further provides a method for recycling phosphorus in sludge, which comprises the following steps: the polyaluminium chloride sludge to be treated in the sludge tank is pumped into a cathode chamber, cathode electrolysis water generates hydroxyl to increase the environmental alkalinity of the cathode chamber, phosphate ions are leached out from the polyaluminium chloride sludge, the phosphate ions are moved to a recovery chamber through an anion exchange membrane under the electric drive, and ferric sulfate in the recovery chamber is crystallized in situ under the anoxic condition to generate the wustite, so that the synchronous leaching, recovery and crystallization of phosphorus in the sludge are finally realized. The method specifically comprises the following steps:
step 1, electrolyte solution is added into an anode chamber, a cathode chamber and a recovery chamber, and ferrous sulfate is added into the recovery chamber; pumping the polyaluminium chloride sludge to be treated, which is filled in a sludge tank, into a cathode chamber, and starting a stirrer to stir the mixed slurry in the cathode chamber uniformly;
step 2, turning on a direct current power supply to adjust the current density to 5-40mA/cm 2 The method comprises the steps of carrying out a first treatment on the surface of the Under the action of an electric field, phosphate ions leached from the mixed slurry in the cathode chamber enter a recovery chamber through an anion exchange membrane;
and step 3, aerating the recovery chamber through a nitrogen bottle, stirring the feed liquid in the recovery chamber, crystallizing phosphate ions and ferrous sulfate in the recovery chamber to form wurtzite, and filtering and collecting the wurtzite after operation is finished.
Further, in step 1, the electrolyte solution has a conductivity of 5000-15000 μS.cm, including but not limited to aqueous solutions of sodium sulfate, potassium sulfate, sodium nitrate, sodium chloride, and the like.
Further, in the step 1, the molar ratio of the ferrous sulfate to the phosphate ions to be recovered in the recovery chamber is 1.5-1.8: 1.
further, P in the polyaluminum chloride sludge to be treated 2 O 5 The mass percentage is more than or equal to 10 percent.
Further, the operation time of one period is controlled to be 2-10 h, and the liquid-solid ratio of the cathode chamber in one period is controlled to be 50mL: 1-10 g. After one cycle is completed, the wustite is recovered, and the solution in the cathode chamber of the previous cycle does not need to be replaced, so that a certain amount of sludge can be continuously pumped into the cathode chamber through the sludge pump.
Further, in the step 3, aeration is carried out until the dissolved oxygen content in the recovery chamber is not more than 1mg/L.
Further, the stirring rate of the stirrer in each chamber is 500 to 1800rpm.
Further, the polyaluminium chloride sludge to be treated is screened and separated to a particle size not more than 200 meshes, and then is put into a sludge tank.
The beneficial effects of the invention are as follows:
1. the method can realize acid-base free medicament addition through electrochemical in-situ alkali generation, and synchronously leach, recover and crystallize polyaluminium chloride (PAC) sludge, wherein the chemical investment is almost zero, and the recovery rate of phosphorus in the sludge can reach more than 65.6 percent.
2. The method of the invention uses ferrous sulfate as an iron source, and is low in cost and easy to obtain.
3. The invention can control the recovery efficiency and the recovery rate of phosphorus by controlling the current density and the liquid-solid ratio.
4. The invention can adopt long-term operation and recycle the cathode leaching liquid, so that the leaching and recovery time is further shortened.
5. The lepidocrocite formed by the method is easy to recycle, can be used as a phosphate fertilizer production raw material, can also be used as a lithium battery synthesis raw material or a collection product, and has high economic value.
Drawings
Fig. 1 is a technical schematic diagram of the present invention.
FIG. 2 is a schematic view of an electrochemical reaction apparatus for recovering phosphorus from sludge according to the present invention, wherein reference numerals are used for the purpose of: 1, a sludge tank; 2, a sludge pump; 3 an anion exchange membrane; 4 cation exchange membrane; 5 nitrogen cylinders; a recovery chamber; 7, a mechanical stirrer; 8 cathode; 9, anode; 10 wires; 11 direct current power supply; 12 anode chamber; 13 cathode chamber; 14 electrolytic cell water inlet.
Fig. 3 is a characterization result of the recovery of the obtained wurtzite in example 5, wherein: (a) SEM and EDS results for the recovered product; (B) EDS spectrum for recovered product; (C) is the XRD pattern of the recovered product; (D) XPS image of recovered product.
Detailed Description
For a further understanding of the present invention, the present invention will be described with reference to specific examples, and the scope of the present invention is not limited by the following examples.
The electrochemical reaction apparatus used in the following examples is shown in FIG. 2: comprises a sludge tank 1, a nitrogen bottle 5, a direct current power supply 11 and an electrolytic cell. The electrolytic cell is provided with an anode chamber 12, a recovery chamber 6 and a cathode chamber 13 in this order. Anode 9 and cathode 8 are inserted into anode chamber 12 and cathode chamber 13, respectively; the direct current power supply 11 is connected with the anode 9 and the cathode 8 in the electrolytic cell 15 through the lead 10 to supply power for the electrochemical reaction device, and the voltage and the current intensity can be adjusted. The discharge port of the sludge tank 1 is connected to the electrolytic cell water inlet 14 at the bottom of the cathode chamber 13 through the sludge pump 2, and the sludge feeding amount can be adjusted according to the requirements. The sludge tank 1, the recovery chamber 6 and the cathode chamber 13 are respectively provided with a mechanical stirrer 7, and the immersion depth and the rotating speed of the mechanical stirrer are adjustable; the nitrogen cylinder 5 is connected to the recovery chamber 5, and the recovery chamber is continuously aerated by controlling the flow rate of nitrogen. The cathode chamber and the recovery chamber are partitioned by an anion exchange membrane 3, the recovery chamber and the anode chamber are partitioned by a cation exchange membrane 4, and the membranes are fixed by two gaskets.
The following examples are presented to demonstrate the recovery of phosphate ions by electrochemical reactions using ferrous sulfate added to the recovery chamber after the run was completed. In actual operation, ferrous sulfate can be added into the recovery chamber first, so that the wustite is generated in situ in the operation process, concentration polarization effect can be reduced, and the recovery rate of phosphorus is further increased.
In the following examples, phosphate ions (PO 4 3- ) The leaching rate and recovery rate of (a) can be calculated by referring to formulas (1) and (2):
wherein: c (C) r,t (mg L -1 ) Is the concentration of phosphate ions in the cathode chamber; c (C) l,t (mg L -1 ) Is the sum of the phosphate ion concentration in the cathode chamber and the recovery chamber; v (V) r,t (L) is the volume of the recovery solution in the recovery chamber for a specified time (hour), V l,t And V is equal to r,t Equal; m is the initial phosphate ion mass of PAC sludge pumped into the cathode chamber.
Equation (3) can be used to calculate the unit energy consumption (SEC) associated with the recovery of element P in kWh kg -1 P。
Wherein M is the molecular weight of P (0.031 kg mol -1 )。E t Is the energy provided by the external power source at a specified time t.
Example 1
In the embodiment, the anode adopts a ruthenium iridium titanium electrode, the cathode adopts a titanium electrode, and the polyaluminum chloride sludge (the initial phosphate ion concentration is 248 mg/L) is treated according to the following steps:
50mL of 3g L was added to each of the anode chamber, the cathode chamber and the recovery chamber -1 Is a NaCl solution; the stirrer of each chamber was turned on at a stirring speed of 500rpm. The liquid-solid ratio in the 5h operation period is 50mL:1g, pumping the polyaluminium chloride sludge to be treated, which is filled in a sludge tank, into a cathode chamber, uniformly stirring the mixed slurry in the cathode chamber, and measuring the pH value of the mixed slurry to be 6.5-7.5.
Turning on DC power supply to regulate current density to 30mA/cm 2 The method comprises the steps of carrying out a first treatment on the surface of the Under the action of an electric field, phosphate ions leached from the mixed slurry in the cathode chamber enter a recovery chamber through an anion exchange membrane; the operation was continued for 5 hours, the phosphate concentration in the samples of the cathode chamber and the recovery chamber was measured, the removal results are shown in Table 1, the leaching rate of phosphate ions was 78.5%, the recovery rate was 65.6%, and the unit energy consumption for recovering phosphorus was 214.44kWh kg -1 P。
Table 1: results of the electrochemical treatment of example 1
After the operation is finished, 0.035g of ferrous sulfate heptahydrate is added into the recovery chamber, the recovery chamber is aerated by a nitrogen bottle, so that the content of dissolved oxygen in the recovery chamber is not more than 1mg/L, the feed liquid in the recovery chamber is stirred, phosphate ions and ferrous sulfate are crystallized in the recovery chamber to form the wurtzite, and the wurtzite is collected by filtration.
Example 2
This example was conducted in the same manner as in example 1 except that the polyaluminum chloride sludge was treated with a current density of 5mA/cm 2 . The operation was continued for 5 hours, the removal results are shown in Table 2, the leaching rate of phosphate is 75.7%, the recovery rate is 20.6%, and the unit energy consumption for recovering phosphorus (P) is 81.01kWh kg -1 P。
Table 2: results of the electrochemical treatment of example 2
After the operation is finished, 0.011g of ferrous sulfate heptahydrate is added into the recovery chamber, the recovery chamber is aerated through a nitrogen bottle, so that the content of dissolved oxygen in the recovery chamber is not more than 1mg/L, the feed liquid in the recovery chamber is stirred, phosphate ions and ferrous sulfate are crystallized in the recovery chamber to form wurtzite, and the wurtzite is collected by filtration.
Example 3
This example treated polyaluminum chloride sludge in the same manner as in example 1 except that the anode was a ruthenium iridium titanium electrode and the cathode was a stainless steel electrode. The operation was continued for 5 hours, and the removal results are shown in Table 3, with a phosphate leaching rate of 83.9% and a recovery rate of 68.7%.
Table 3: results of the electrochemical treatment of example 3
After the operation is finished, 0.035g of ferrous sulfate heptahydrate is added into the recovery chamber, the recovery chamber is aerated by a nitrogen bottle, so that the content of dissolved oxygen in the recovery chamber is not more than 1mg/L, the feed liquid in the recovery chamber is stirred, phosphate ions and ferrous sulfate are crystallized in the recovery chamber to form the wurtzite, and the wurtzite is collected by filtration.
Example 4
In this example, polyaluminum chloride sludge was treated in the same manner as in example 1 except that 50mL of 3.64g L was added to each of the anode chamber, the cathode chamber and the recovery chamber -1 Na of (2) 2 SO 4 A solution. The operation was continued for 5 hours, and the removal results are shown in Table 4, with 84.4% phosphate leaching rate and 50.1% recovery rate.
Table 4: results of the electrochemical treatment of example 4
After the operation is finished, 0.026g of ferrous sulfate heptahydrate is added into the recovery chamber, the recovery chamber is aerated through a nitrogen bottle, so that the content of dissolved oxygen in the recovery chamber is not more than 1mg/L, the feed liquid in the recovery chamber is stirred, phosphate ions and ferrous sulfate are crystallized in the recovery chamber to form the wurtzite, and the wurtzite is collected by filtration.
Example 5
In this example, the periodic operation was adopted, and according to the conditions of example 1, 2 hours was taken as a recovery period, and after each period was completed, the solution in the cathode chamber of the previous period was not replaced, and a certain amount of sludge was continuously pumped into the cathode chamber by the sludge pump. A total of 5 cycles (10 hours) were run. Table 5 shows the results after five cycles of processing.
After five cycles of treatment, 0.254g of ferrous sulfate heptahydrate is added into the recovery chamber, the recovery chamber is aerated through a nitrogen bottle, so that the content of dissolved oxygen in the recovery chamber is not more than 1mg/L, the feed liquid in the recovery chamber is stirred, phosphate ions and ferrous sulfate are crystallized in the recovery chamber to form wurtzite, and the wurtzite is collected by filtration. FIG. 3 is a characterization result of the obtained wurtzite after five cycles of operation, the purity of which is not less than 98%.
Table 5: results of the electrochemical treatment of example 5
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.
Claims (9)
1. An electrochemical reaction device for recycling phosphorus in sludge, which is characterized in that: comprises a sludge tank (1), a nitrogen cylinder (5), a direct current power supply (11) and an electrolytic cell; an anode chamber (12), a recovery chamber (6) and a cathode chamber (13) are sequentially arranged in the electrolytic cell; an anode (9) and a cathode (8) are respectively inserted into the anode chamber (12) and the cathode chamber (13); the direct current power supply (11) is connected with an anode (9) and a cathode (8) in the electrolytic cell through a lead (10) to supply power for the electrochemical reaction device; the discharge port of the sludge tank (1) is connected to an electrolytic cell water inlet (14) at the bottom of the cathode chamber (13) through a sludge pump (2); mechanical agitators (7) are respectively arranged in the sludge tank (1), the recovery chamber (6) and the cathode chamber (13); the nitrogen cylinder (5) is connected to the recovery chamber (6).
2. The electrochemical reaction apparatus for recovering phosphorus from sludge as claimed in claim 1, wherein: the cathode chamber and the recovery chamber are partitioned by an anion exchange membrane (3), and the recovery chamber and the anode chamber are partitioned by a cation exchange membrane (4).
3. A method for recovering phosphorus from sludge by using the electrochemical reaction apparatus as claimed in any one of claims 1 to 2, characterized in that: the polyaluminium chloride sludge to be treated in the sludge tank is pumped into a cathode chamber, cathode electrolysis water generates hydroxyl to increase the environmental alkalinity of the cathode chamber, phosphate ions are leached out from the polyaluminium chloride sludge, the phosphate ions are moved to a recovery chamber through an anion exchange membrane under the electric drive, and ferric sulfate in the recovery chamber is crystallized in situ under the anoxic condition to generate the wustite, so that the synchronous leaching, recovery and crystallization of phosphorus in the sludge are finally realized.
4. A method according to claim 3, comprising the steps of:
step 1, electrolyte solution is added into an anode chamber, a cathode chamber and a recovery chamber, and ferrous sulfate is added into the recovery chamber; pumping the polyaluminium chloride sludge to be treated, which is filled in a sludge tank, into a cathode chamber, and starting a stirrer to stir the mixed slurry in the cathode chamber uniformly;
step 2, turning on a direct current power supply to adjust the current density to 5-40mA/cm 2 The method comprises the steps of carrying out a first treatment on the surface of the Under the action of an electric field, phosphate ions leached from the mixed slurry in the cathode chamber enter a recovery chamber through an anion exchange membrane;
and step 3, aerating the recovery chamber through a nitrogen bottle, stirring the feed liquid in the recovery chamber, crystallizing phosphate ions and ferrous sulfate in the recovery chamber to form wurtzite, and filtering and collecting the wurtzite after operation is finished.
5. The method according to claim 4, wherein: in step 1, the electrolyte solution has a conductivity of 5000-15000 μS.cm.
6. The method according to claim 4, wherein: in the step 1, the molar ratio of the ferrous sulfate to the phosphate ions to be recovered in the recovery chamber is 1.5-1.8: 1.
7. the method according to claim 4, wherein: p in the polyaluminum chloride sludge to be treated 2 O 5 The mass percentage is more than or equal to 10 percent.
8. The method according to claim 4, wherein: the operation time of one period is controlled to be 2-10 h, and the liquid-solid ratio of the cathode chamber in one period is controlled to be 50mL: 1-10 g.
9. The method according to claim 4, wherein: in the step 3, the dissolved oxygen content of the recovery chamber is not more than 1mg/L.
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