Method and device for treating heavy metals in wastewater in a wet process for treating waste photovoltaic modules

Abstract

The application provides a waste water heavy metal treatment method and device in a waste photovoltaic module wet treatment process, and the method comprises the following steps: 1) determining the content of total metal ions in waste water; placing the waste water in a reaction container provided with electromagnets at the bottom, and closing the starting switch of the electromagnets; 2) adjusting the temperature of the waste water to 50-60 DEG C, adding two kinds of iron salts, trivalent iron salt and divalent iron salt, into the waste water, the adding ratio is that the mass ratio of the trivalent iron salt and the divalent iron salt is 1:1, the mass ratio of the divalent iron ion and the total heavy metal ion is 7:1-8:1, and the pH value is adjusted to 7-8, mechanical stirring is carried out in the process of adding the iron salts, the rotating speed is 150-200 r / min, the reaction time is 10-15 min, and the reaction is carried out; 3) after the reaction is completed, the electromagnets arranged at the bottom of the reaction container are started, and rapid solid-liquid separation is carried out by using the magnetism of the ferrite. The application provides an environmental and economic technical scheme for waste photovoltaic industry waste resource.

Description

Technical Field

[0001] This invention belongs to the field of environmental science and technology, and particularly relates to the field of wastewater treatment containing heavy metals. Specifically, it relates to a method and apparatus for treating heavy metals in wastewater during the wet treatment of waste photovoltaic modules. Background Technology

[0002] Photovoltaic (PV) technology is a green and renewable energy technology that directly converts solar energy into electricity without producing greenhouse gases. The heavy metal ions in the wet process wastewater from decommissioned photovoltaic modules mainly contain copper, lead, tin, aluminum, and silver, and their concentration ranges are generally relatively fixed. Depending on the type of metal ions in the waste photovoltaic modules, the types and concentration ranges of various metals produced during the wet treatment process are generally: copper 100-200 mg / L, tin 20-40 mg / L, lead 20-30 mg / L, aluminum 10-30 mg / L, and silver 2-10 mg / L. Currently, there are no publicly available wastewater treatment technologies specifically targeting heavy metals in the wet process wastewater from decommissioned photovoltaic modules. Existing wastewater treatment processes target different types and concentrations of metal ions than those described in this invention. Therefore, existing methods either cannot efficiently remove heavy metals from the wet process wastewater from decommissioned photovoltaic modules, or are too costly and complex for large-scale industrial processing. Summary of the Invention

[0003] The purpose of this invention is to address the above-mentioned technical problems by proposing a method and apparatus for treating heavy metals in wastewater from the wet processing of waste photovoltaic modules. This objective is achieved through the following technical solution:

[0004] A method for treating heavy metals in wastewater during the wet processing of waste photovoltaic modules includes the following steps:

[0005] Step 1: Detect the total metal ion content in the wastewater to be tested; place the wastewater to be tested in a reaction vessel with an electromagnet at the bottom, and turn off the electromagnet's start switch;

[0006] Step 2: Adjust the wastewater temperature to 50-60℃, then add ferric salts (Fe3+ and ferrous) to the wastewater in a ratio of 1:1 (Fe3+ to ferrous) and 7:1-8:1 (ferrous ions to total heavy metal ions). Adjust the pH to 7-8. During the addition of the iron salts, mechanically stir at 150-200 rpm for 10-15 minutes. The ferric salt is either ferric chloride or ferric sulfate, and the ferrous salt is either ferrous chloride or ferrous sulfate.

[0007] Step 3: After the reaction is complete, activate the electromagnet located at the bottom of the reaction vessel. The electromagnetic attraction force per unit precipitate is 2 × 10⁻⁶. 5 ~5×10 5N / kg, utilizing the magnetic properties of ferrite for rapid solid-liquid separation, with a precipitation time of 2–5 min.

[0008] The types and concentration ranges of metals in the wastewater are as follows: copper: 100-200 mg / L, tin: 20-40 mg / L, lead: 20-30 mg / L, aluminum: 10-30 mg / L, and silver: 2-10 mg / L.

[0009] Further optimization involves step two, where the molar ratio of ferrous ions to total heavy metal ions is 7.5:1.

[0010] Further optimization involves adjusting the pH to 7.5 in step two.

[0011] Further optimization involves adjusting the wastewater temperature to 55℃ in step two.

[0012] Further optimization involves setting the sedimentation time to 2.5 minutes in step three.

[0013] The treatment apparatus used in the wet treatment process of waste photovoltaic modules for heavy metals in wastewater includes:

[0014] Reaction vessel: It is equipped with a water inlet, a chemical dosing port, a sensor port, a water outlet at the bottom, and a sludge discharge port at the bottom;

[0015] Dosing device: connected to the dosing port of the reaction vessel; includes a dosing tank, a dosing pump, and an inlet pipe;

[0016] Water inlet device: connected to the water inlet of the reaction vessel; including a water inlet pipe and a flow meter connected to the water inlet pipe.

[0017] Sensor: Connected to the sensor port of the reaction vessel, used to measure pH and temperature;

[0018] Electromagnetic coil: Located at the bottom of the reaction vessel;

[0019] Mechanical stirring device: installed inside the reaction vessel;

[0020] Heating device: installed on the wall of the reaction vessel or inside the reaction vessel.

[0021] Control panel: Electrically connected to the flow meter, sensor, solenoid coil switch, dosing pump switch, heating device switch, and mechanical stirring device switch, used to display online monitoring data of flow rate, pH and temperature, and control the start and stop of the dosing pump, the start and stop of the solenoid coil, stirring time and temperature adjustment.

[0022] Further optimization involves the following dosing device: it includes three dosing tanks: a ferric salt dosing tank, a ferrous salt dosing tank, and a sodium hydroxide dosing tank. Each dosing tank is connected to a dosing pump, and the input lines of all the dosing pumps converge into a main inlet pipe, which is connected to the dosing port of the reaction vessel.

[0023] Furthermore, the reaction vessel is divided into upper and lower parts, with the upper part being cylindrical and the lower part being conical, and the electromagnetic coil is installed in the conical part.

[0024] The principle of this invention is that, under weakly alkaline conditions, in the first stage reaction, due to the high absolute value of the Gibbs free energy in formula (1), some of the ferrous ions in ferrous sulfate will spontaneously participate in the oxidation reaction at a higher temperature, while the other part, along with the ferric ions in ferric iron, will be hydrolyzed into iron hydroxide (formula (2)). At a reaction temperature of 55°C, Fe(OH)2 and Fe(OH)3 react rapidly to generate Fe3O4 (formula (3)), Cu 2+ In this process, Fe is replaced. 2+ The position forms CuFe2O4 (Formula (4)), thus realizing the Cu in the waste liquid. 2+ The removal of.

[0025] 4Fe 2+ +8OH - +2H₂O+O₂→4Fe(OH)₃ (1)

[0026] Fe 2+ +2H₂O→Fe(OH)₂+2H + (2)

[0027] 3Fe 3+ +3H₂O→Fe(OH)₃+3H +

[0028] 2Fe(OH)3+Fe(OH)2→Fe3O4+4H2O (3)

[0029] (1-x)Fe 2+ +2Fe 3+ +xCu 2+ +8OH - →Cu x Fe 3-x O4↓+4H2O (4)

[0030] Al 3+ Pb 2+ In the first stage, it reacts with OH - The reactions in formulas (5) to (6) occur to form the corresponding hydroxides; due to Sn 2+ Extremely unstable, Sn with a lower electrode potential is easily oxidized by a higher potential.2+ It will be Fe 3+ Oxidation of O2 to Sn 4+ Subsequently, a hydrolysis reaction occurs (Equation (7)), while a small amount of Ag... + After the addition of ferric chloride, the reaction proceeds rapidly with the reaction formula (8) to precipitate the hydroxide. Due to the short reaction time in the first stage, the hydroxide crystallization is poor, and most of the precipitate is amorphous hydroxide, while the heavy metal ion content in the waste liquid still decreases rapidly.

[0031] Al 3+ +3OH - →Al(OH)3 (5)

[0032] Pb 2+ +OH - →Pb(OH)2 (6)

[0033] 2Sn 2+ +H + +O2→2Sn 4+ +2H2O

[0034] Sn 4+ +4H₂O→Sn(OH)₄+4H + (7)

[0035] Ag + +Cl - →AgCl↓ (8)

[0036]

[0037] As the reaction time increased, the compounds in the waste liquid underwent a second-stage reaction. During this process, the generated Fe3O4 and CuFe2O4 particles continued to age and grow, forming nanopillars with rough surfaces and spinel multiphase structures. These nanopillars interconnected, creating tiny pores that firmly encapsulated AgCl, Al(OH)3, Pb(OH)2, and SnO2, achieving stable solidification of heavy metal ions in the waste liquid. The strong magnetism exhibited by the precipitate provided a feasible path for subsequent simple magnetic separation.

[0038] Beneficial effects of this invention:

[0039] This invention utilizes a multi-metal ion coordination-coprecipitation coupling mechanism to transform copper in wastewater into a nanoscale composite ferrite functional material (nano CuFe2O4) with spinel-type crystals, and Pb... 2+ Cu 2+ Sn 2+Other metals can be incorporated into the crystal lattice and encapsulated. This material exhibits good magnetic properties, enabling efficient solid-liquid separation through an external magnetic field, significantly reducing settling time. Furthermore, its lattice solid solution characteristics suggest potential applications in electromagnetic wave absorption, catalyst support, and material adsorption.

[0040] This invention utilizes heavy metals in wastewater from the wet processing of waste photovoltaic modules. After adding iron salts to generate a precipitate, the supernatant contains residues of heavy metal ions, in addition to the original heavy metal ions. The residual iron in the supernatant is also considered. Leaching toxicity tests are conducted on the precipitate according to standards. The pH is adjusted to a neutral to slightly alkaline state, eliminating the need for air stirring. Temperature control reduces energy consumption. The formation of ferrite precipitate reduces the leaching toxicity of the precipitate (below 1%), thus lowering the risk. Electromagnets are used to accelerate the separation of the precipitate, leveraging the magnetic properties of the generated ferrite material.

[0041] This invention breaks through the limitations of traditional end-of-pipe treatment and forms a technical path of pollutant reduction and functional material regeneration, providing a technical solution with environmental and economic benefits for the resource utilization of waste photovoltaic industry.

[0042] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0043] Figure 1 Analysis of the effects of different parameters on metal precipitation and leaching toxicity in the ferrite method of this invention;

[0044] Figure 2 This invention illustrates the changes in the main phases of the precipitate under the same temperature using XRD.

[0045] Figure 3 These are the magnetization curves at different reaction temperatures of this invention;

[0046] Figure 4 This is the magnetic precipitation process of the present invention;

[0047] Figure 5 The nitrogen adsorption-desorption isotherm and pore size distribution diagram of the precipitate of this invention are shown below.

[0048] Figure 6 This is a schematic diagram of the treatment device structure for the wastewater heavy metal treatment method in the wet treatment process of waste photovoltaic modules according to the present invention.

[0049] Figure label:

[0050] 1. Reaction vessel; 2. Dosing device; 3. Water inlet device; 4. Sensor; 5. Electromagnetic coil; 6. Mechanical stirring device; 11. Water inlet; 12. Dosing port; 13. Sensor port; 14. Water outlet at the bottom; 15. Sludge discharge port at the bottom; 16. Sludge pump; 21. Ferric salt dosing tank; 22. Ferric salt dosing tank; 23. Sodium hydroxide dosing tank; 24. Dosing pump; 31. Flow meter. Detailed Implementation

[0051] Example 1

[0052] A method for treating heavy metals in wastewater from the wet processing of waste photovoltaic modules, wherein the types and concentration ranges of metals in the wastewater are: copper: 100-200 mg / L, tin: 20-40 mg / L, lead: 20-30 mg / L, aluminum: 10-30 mg / L, and silver: 2-10 mg / L. The method includes the following steps:

[0053] Step 1: Check the total metal ion content (n(Me)) in the wastewater to be tested; place the wastewater to be tested in a reaction vessel with an electromagnet at the bottom; and turn off the electromagnet's start switch;

[0054] Step 2: Adjust the wastewater temperature to 55℃, and add ferric chloride and ferrous sulfate to the wastewater at a ratio of 1:1 (ferric salt to ferrous salt) and 7.5:1 (ferrous ion to total heavy metal ion). Adjust the pH to 7.5. During the addition of the ferric salts, mechanical stirring is carried out at 200 r / min for 10 min at a reaction temperature of 55℃.

[0055] Step 3: After the reaction is complete, start the reaction vessel. An electromagnet is installed at the bottom of the vessel; the electromagnetic attraction range per unit precipitate is 2 × 10⁻⁶. 5 ~5×10 5 N / kg, utilizing the magnetic properties of ferrite for rapid solid-liquid separation, with a precipitation time of 2.5 min.

[0056] Example 2

[0057] The difference between this embodiment and Embodiment 1 is that:

[0058] Step 2: The molar ratio of ferrous ions to total heavy metal ions is 8:1.

[0059] Example 3

[0060] The difference between this embodiment and Embodiment 1 is that:

[0061] Step 2: Adjust the pH to 7.

[0062] Example 4

[0063] The difference between this embodiment and Embodiment 1 is that:

[0064] Step 2: Adjust the pH to 8.

[0065] Example 5

[0066] The difference between this embodiment and Embodiment 1 is that:

[0067] Step 2: Reaction temperature 50℃.

[0068] Example 6

[0069] The difference between this embodiment and Embodiment 1 is that:

[0070] Step 2: Reaction temperature 60℃.

[0071] Example 7

[0072] The difference between this embodiment and Embodiment 1 is that:

[0073] Step 2: Reaction time 15 min.

[0074] Example 8

[0075] The difference between this embodiment and Embodiment 1 is that:

[0076] The ferric salt mentioned is ferric sulfate.

[0077] Comparative Example 1

[0078] The difference between this embodiment and Embodiment 1 is that:

[0079] Step 2: The molar ratio of ferrous ions to total heavy metal ions is 3.5:1.

[0080] Comparative Example 2

[0081] The difference between this embodiment and Embodiment 1 is that:

[0082] Step 2: The molar ratio of ferrous ions to total heavy metal ions is 5:1.

[0083] Comparative Example 3

[0084] The difference between this embodiment and Embodiment 1 is that:

[0085] Step 2: The molar ratio of ferrous ions to total heavy metal ions is 10:1.

[0086] Comparative Example 4

[0087] The difference between this embodiment and Embodiment 1 is that:

[0088] Step 2: Add the ferric salt in a ratio of 2:1 (molar ratio of ferric salt to ferrous salt).

[0089] Comparative Example 5

[0090] The difference between this embodiment and Embodiment 1 is that:

[0091] Step 2: Add the ferric salt in a ratio of 3:1 (3 parts ferric salt to ferrous salt).

[0092] Comparative Example 6

[0093] The difference between this embodiment and Embodiment 1 is that:

[0094] Step 2: Adjust the pH to 6.

[0095] Comparative Example 7

[0096] The difference between this embodiment and Embodiment 1 is that:

[0097] Step 2: Adjust the pH to 10.

[0098] Comparative Example 8

[0099] The difference between this embodiment and Embodiment 1 is that:

[0100] Step 2: Adjust the pH to 12.

[0101] Comparative Example 9

[0102] The difference between this embodiment and Embodiment 1 is that:

[0103] Step 2: Reaction time 1 min.

[0104] Comparative Example 10

[0105] The difference between this embodiment and Embodiment 1 is that:

[0106] Step 2: Reaction time 8 minutes.

[0107] Comparative Example 11

[0108] The difference between this embodiment and Embodiment 1 is that:

[0109] Step 2: Reaction time 20 min.

[0110] Comparative Example 12

[0111] The difference between this embodiment and Embodiment 1 is that:

[0112] Step 2: Reaction temperature 25℃.

[0113] Comparative Example 13

[0114] The difference between this embodiment and Embodiment 1 is that:

[0115] Step 2: Reaction temperature 45℃.

[0116] Comparative Example 14

[0117] The difference between this embodiment and Embodiment 1 is that:

[0118] Step 2: Reaction temperature 65℃.

[0119] Comparative Example 15

[0120] The difference between this embodiment and Embodiment 1 is that:

[0121] In step two, the rotation speed is 300 r / min

[0122] Too high a speed will break up the sediment, resulting in poor sedimentation.

[0123] Comparative Example 16

[0124] The difference between this embodiment and Embodiment 1 is that:

[0125] In step two, first add iron salt and adjust the pH, then raise the temperature to 55℃ after 2 minutes.

[0126] It affects the formation of the ferrite precipitate magnetic phase, thus affecting the magnetic separation effect.

[0127] The results of ferrite treatment of heavy metal ions in wastewater under different parameter conditions in the above embodiments and comparative examples are as follows: Figure 1 As shown.

[0128] like Figure 1 As shown in (a), the total precipitation rate of heavy metals gradually increases with increasing pH. When the pH reaches 7, the total precipitation efficiency of metal ions gradually stabilizes at around 99%. Therefore, a pH of 7-8 is chosen. In the comparative example, when the pH is below 7, such as pH=6, the measurement results are significantly lower than those at pH=7. However, when the pH is above 8, the precipitation effect does not change significantly. From a practical point of view, it is unnecessary to add too much alkali solution, which would make the solution too alkaline.

[0129] Figure 1 (b) Precipitation efficiency of heavy metal ions at different dosages. Vertically, the total precipitation efficiency remained high throughout the range of ferric and ferrous salt ratios from 1:1 to 3:1. Horizontally, the total precipitation efficiency of heavy metal ions was high when the ratio of ferrous ions to total heavy metal ions was from 3.5:1 to 10:1, and the molar ratio of ferrous ions to total heavy metal ions was 3-4, regardless of the ratio of ferric and ferrous ions. 3+ with Fe 2+Insufficient quantity; at this stage, the neutralization method is used as the main precipitation mechanism to remove heavy metal ions. However, after leaching toxicity testing, the heavy metals are leached out again, resulting in high leaching toxicity, so this section is abandoned. The final ferrite method of this invention has a leaching toxicity of less than 1%, with low environmental risk. When the molar ratio of ferrous ions to total heavy metal ions is 5, and the ratio of ferric salt to ferrous salt is 1:1, the total precipitation efficiency of metal ions is less than 80%, at which point Fe... 2+ A hydrolysis reaction occurs, forming tiny Fe(OH)3 colloids that encapsulate part of the Cu. 2+ This prevents it from reacting with OH in the waste liquid. - Contact precipitation leads to a decrease in the overall metal precipitation efficiency. When the molar ratio of ferrous ions to total heavy metal ions is greater than 7.5:1, the overall metal precipitation efficiency exceeds 98%. Further increases in Fe... 2+ At certain concentrations, the effect did not change significantly.

[0130] Figure 1 (c) This shows the effect of hydrothermal reaction time on the total precipitation efficiency of various heavy metal ions in the waste liquid. It can be seen that the total precipitation efficiency reaches 98.54% after 1 min of reaction. As the reaction continues, the precipitation efficiency slowly increases to about 99% and remains stable. The precipitation efficiency is 99.02% after 10 min. After 15 min, the effect is not obvious.

[0131] Figure 1 (d) shows the reaction conditions at different temperatures. This technique fully considers the stability of the generated ferrite precipitate and tests the leaching toxicity of the precipitate at different temperatures. When the temperature is 25℃, the leaching toxicity of the precipitate is as high as 43.12%, and the total metal ion precipitation efficiency is 98.5%. At 55℃, the leaching toxicity of the precipitate decreases to 0.61%, and the total precipitation efficiency increases to 98.81%. Further increasing the temperature to 65℃ shows no significant change.

[0132] According to the research of this invention, the phase composition of ferrite precipitates undergoes significant changes at different temperatures, see... Figure 2 . Figure 2 (a) indicates that as the temperature increases, the peak intensity of the non-magnetic iron phase FeOOH decreases, while the peak intensity of the magnetic phases CuFe2O4 and Fe3O4 increases, indicating that the formation of spinel structures in ferrite materials and copper ferrite materials gradually increases. Figure 2 (b) shows the XRD spectrum of the precipitate under optimal conditions at 55℃, with the main peak positions corresponding to Fe3O4 and CuFe2O4.

[0133] like Figure 3As shown, the S-shaped magnetization curve indicates that the material is superparamagnetic. As the temperature increases, the saturation magnetization increases rapidly, reaching its maximum at 55℃, indicating an increase in the content and purity of the magnetic material. This proves that the precipitate can be separated magnetically.

[0134] Figure 4 To facilitate the magnetic attraction of ferrite precipitation, an electromagnetic coil is installed at the bottom of the beaker. After the reaction is complete, the coil is de-energized, and by adjusting the current, the precipitate can settle rapidly within 2.5 minutes, significantly improving the efficiency compared to natural sedimentation. The precipitate is relatively compact and does not easily disperse when shaken, which is beneficial for the discharge of the supernatant. Figure 4 From left to right, the images show the magnetic separation states of the precipitate at different times. At 0 min, the solution is black and turbid. After 45 seconds of turning on the electromagnetic coil, a noticeable precipitate is visible at the bottom, and the solution color is darker. After 1.5 min, the precipitate layer thins, and the solution color lightens. After 2.5 min, the precipitate layer thickness no longer changes, and the solution eventually becomes clear and transparent.

[0135] Figure 5 The table shows the nitrogen adsorption-desorption isotherms and pore size distribution of the precipitate. Based on the curve shape, the adsorption isotherms of the precipitate belong to type IV isotherm configuration, indicating that the precipitate is a nanoscale mesoporous material. The pores in this type of hysteresis loop reactive material include planar slit structures, cracks, and wedge-shaped structures. According to the pore size distribution curve, the average pore size of the BJH adsorption in the precipitate is 13.15 nm (Table 1), with very few micropores and macropores, proving that only mesoporous structures exist in the precipitate. Furthermore, 75.411 nm... 2 / g has a relatively moderate BET surface area and 0.2479cm² 3 The pore volume of / g indicates that there are a large number of accessible pore channels inside the precipitate, which is conducive to the transport of matter and can be used for the adsorption of small and medium molecular pollutants, showing potential as an adsorption material.

[0136] Table 1. Morphological properties of precipitates under optimal experimental conditions.

[0137]

[0138] Example 8

[0139] The treatment apparatus for the wastewater heavy metal resource recovery method in the wet treatment process of waste photovoltaic modules described in Example 1 includes:

[0140] Reaction vessel 1: It is equipped with a water inlet 11, a chemical dosing port 12, a sensor port 13, a water outlet 14 at the bottom, and a sludge discharge port 15 at the bottom; the sludge discharge port 15 is connected to a sludge pump 16 through a pipeline;

[0141] Dosing device 2: connected to the dosing port 12 of reaction vessel 1; includes a dosing tank, a dosing pump and an inlet pipe; includes three dosing tanks, namely ferric salt dosing tank 21, ferrous salt dosing tank 22 and sodium hydroxide dosing tank 23, each dosing tank is connected to a dosing pump 24, and the input pipes of each dosing pump 24 converge into a general inlet pipe, which is connected to the dosing port 12 of reaction vessel 1;

[0142] Water inlet device 3: connected to the water inlet 11 of the reaction vessel 1; including a water inlet pipe and a flow meter 31 connected to the water inlet pipe. Sensor 4: connected to the sensor port 13 of the reaction vessel 1, used to measure pH and temperature.

[0143] Electromagnetic coil 5: Located at the bottom of reaction vessel 1; reaction vessel 1 consists of two parts, the upper part is cylindrical and the lower part is conical, and the electromagnetic coil 5 is installed in the conical part;

[0144] Mechanical stirring device 6: installed inside reaction vessel 1;

[0145] Heating device: installed on the wall or inside the reaction vessel.

[0146] Control panel 7: Electrically connected to the switches of flow meter 31, sensor 4, electromagnetic coil 5, dosing pump, heating device, and mechanical stirring device 6, used to display data of online monitoring of flow rate, pH and temperature, and to control the start and stop of the dosing pump, the start and stop of the electromagnetic coil 5, stirring time and temperature adjustment.

[0147] The wastewater from the wet treatment process of waste photovoltaic modules is recycled using the treatment device described in this embodiment. The specific operation is as follows:

[0148] Step 1: Check the total metal ion content in the wastewater to be tested; place the wastewater to be tested in reaction vessel 1; and turn off the start switch of electromagnetic coil 5;

[0149] Step 2: Adjust the temperature inside reaction vessel 1 to 55℃. Add reagents according to the reading of the inlet flow meter 31 and the heavy metal concentration tested in the previous step. Add ferric salt and ferrous salt to the wastewater in a ratio of 1:1 and 7.5:1. Simultaneously, quickly add sodium hydroxide to adjust the pH while stirring. Stop adding reagents when the pH reaches 7-8 as indicated by the sensor.

[0150] Step 3: After the reaction is complete, turn on the switch of the bottom electromagnetic coil 5. The electromagnetic attraction range per unit precipitate is 2×10. 5 ~5×10 5N / kg, utilizing the magnetic properties of ferrite for rapid solid-liquid separation, with a sedimentation time of 5 minutes. After 5 minutes, the outlet 14 is opened to drain the water. After drainage, the switch of the electromagnetic coil is turned off, and the bottom sludge pump 16 is turned on to pump out the bottom ferrite sediment through the bottom sludge discharge port 15, thus achieving solid-liquid separation.

[0151] The above embodiments are only a partial embodiment of the present invention and do not cover all of the present invention. Based on the above embodiments and the accompanying drawings, those skilled in the art can obtain more implementation methods without creative effort. Therefore, all implementation methods obtained without creative effort should be included within the protection scope of the present invention.

Claims

1. A method for treating heavy metals in wastewater from the wet processing of waste photovoltaic modules, wherein the types and concentration ranges of metals in the wastewater are: copper: 100-200 mg / L, tin: 20-40 mg / L, lead: 20-30 mg / L, aluminum: 10-30 mg / L, silver: 2-10 mg / L, characterized in that: Includes the following steps: Step 1: Check the total metal ion content (nMe) in the wastewater to be tested; place the wastewater to be tested in a reaction vessel with an electromagnet at the bottom; and turn off the electromagnet's start switch; Step 2: Adjust the wastewater temperature to 55℃, and add ferric chloride and ferrous sulfate to the wastewater at a ratio of 1:1 (ferric salt to ferrous salt) and 7.5:1 (ferrous ion to total heavy metal ion). Adjust the pH to 7.

5. During the addition of the ferric salts, mechanical stirring is carried out at 200 r / min for 10 min at a reaction temperature of 55℃. Step 3: After the reaction is complete, start the reaction vessel. An electromagnet is installed at the bottom of the vessel; the electromagnetic attraction range per unit precipitate is 2 × 10⁻⁶. 5 ~5×10 5 N / kg, utilizing the magnetic properties of ferrite for rapid solid-liquid separation, with a precipitation time of 2.5 min.

Images