A method for improving the efficiency of zero-valent iron sheets in removing heavy metal ions from wastewater

Abstract

The present invention is a method for improving the efficiency of removing heavy metal ions from wastewater by zero-valent iron sheets, which comprises the following steps: 1) Select a cylindrical container capable of accommodating zero-valent iron sheets and wastewater; 2) Weld wires on both sides in the normal direction of the zero-valent iron sheets. When welding the wire on the side closer to the container wall, the oxide layer on the surface of the iron sheet should be ground off to ensure contact between the wire and Fe<supgt;0< / supgt; of the zero-valent iron sheet. Roll up the zero-valent iron sheet along the side with a length of L and place it in the cylindrical container, close to the container wall, and connect the wire to a DC regulated power supply to apply a DC voltage. Install a stirring device in the cylindrical container; and fill the cylindrical container with wastewater; 3) Turn on the DC regulated power supply connected to the wire, and at the same time use a reflecting device to reflect sunlight onto the part of the zero-valent iron sheet that extends out of the wastewater container and is close to the wall of the wastewater container. At this time, the heavy metal wastewater in the cylindrical container can be treated. The present invention combines sunlight illumination with a certain range of directional DC low voltage to improve the conductivity of the amorphous layer on the surface of the zero-valent iron sheet; combined with the effect of allowing electrons to preferentially emit from the side where the zero-valent iron contacts the heavy metal waste liquid, it improves the utilization rate of photo-generated electrons and the number of electrons participating in the redox reaction per unit time, thereby increasing the rate of removing heavy metals from wastewater by zero-valent iron sheets.

Description

Technical Field

[0001] The present invention relates to a method for improving the efficiency of removing heavy metal ions from wastewater, in particular to a method for improving the efficiency of removing heavy metal ions from wastewater by zero-valent iron sheets, and belongs to an innovative technology for improving the efficiency of removing heavy metal ions from wastewater by zero-valent iron sheets. Background Art

[0002] At present, with the development of industrial production, more and more heavy metal wastewater needs to be treated. Traditional technologies have high treatment costs, complex processes, and low treatment efficiencies, and are no longer capable of handling the heavy task of heavy metal treatment. The zero-valent iron treatment technology is the most promising technology to solve this problem, but there are still bottlenecks. As Figure 11 shown, due to the easy oxidation of the surface of zero-valent iron during storage, transportation, and application, there is an inorganic amorphous film. The electrons in this amorphous film are basically in a localized state, and the conduction basically relies on the assistance of phonons Leap type for conduction, so its conductivity is poor. This means that the number of electrons reaching the surface from the inside of the iron sheet to participate in the redox reaction per unit time is very low, resulting in the removal efficiency and cyclic performance not meeting the requirements of the rate and operating cost for large-scale applications. Summary of the Invention

[0003] The object of the present invention is to provide a method for improving the efficiency of removing heavy metal ions from wastewater in consideration of the above problems. The present invention improves the conductivity of the above amorphous inorganic film layer through sunlight illumination combined with applying a directional DC low voltage within a certain range; at the same time, enabling electrons to preferentially emit from the side where zero-valent iron contacts the heavy metal waste liquid, improving the utilization rate of photo-generated electrons and the number of electrons participating in the redox reaction per unit time, thereby further increasing the rate of removing heavy metals from wastewater by zero-valent iron sheets.

[0004] The technical solution of the present invention is as follows: The method for improving the efficiency of removing heavy metal ions from wastewater by zero-valent iron sheets of the present invention includes the following steps:

[0005] 1) Select a cylindrical container that can accommodate zero-valent iron sheets and wastewater;

[0006] 2) Weld wires on both sides in the normal direction of the zero-valent iron sheet. When welding the wire on the side close to the container wall, the oxide layer on the surface of the iron sheet should be ground off to ensure contact between the wire and the Fe of the zero-valent iron sheet 0 Contact, roll up the zero-valent iron sheet along the side with a length of L and place it in the cylindrical container, close to the container wall, and connect the wire to a DC regulated power supply to apply a DC voltage. Install a stirring device in the cylindrical container; and fill the cylindrical container with wastewater.

[0007] 3) Turn on the DC regulated power supply of the connecting wire, and at the same time use the reflecting device to reflect sunlight onto the part of the iron sheet that protrudes from the wastewater container. At this time, the heavy metal wastewater in the cylindrical container can be treated.

[0008] The present invention combines sunlight irradiation with a certain range of directional DC low voltage to increase the extended state of electrons in the amorphous inorganic thin film layer, thereby increasing the conductivity of the amorphous layer; combined with the effect of allowing electrons to preferentially emit from the side where zero-valent iron contacts the heavy metal waste liquid, the utilization rate of photo-generated electrons and the number of electrons participating in the redox reaction are increased, and further the rate of removing heavy metals from wastewater by zero-valent iron sheets is increased. The present invention is a convenient and practical method for improving the efficiency of removing heavy metal ions from wastewater. Brief Description of the Drawings

[0009] Figure 1 is the schematic diagram of the principle of the present invention;

[0010] Figure 2 is the schematic structural diagram of the zero-valent iron sheet of the present invention;

[0011] Figure 3 is the schematic structural diagram of the zero-valent iron sheet of the present invention placed in the wastewater container;

[0012] Figure 4 is the relationship curve graph of the removal rate R(t) and time t in Example 1 of the present invention (R(t)~t);

[0013] Figure 5 is the relationship curve graph of the removal rate R(t) and time t in Example 2 of the present invention (R(t)~t);

[0014] Figure 6 is the relationship curve graph of the removal rate R(t) and time t in Example 3 of the present invention (R(t)~t);

[0015] Figure 7 is the relationship curve graph of the removal rate R(t) and time t in Example 4 of the present invention (R(t)~t);

[0016] Figure 8 is the relationship curve graph of the removal rate R(t) and time t in Example 5 of the present invention (R(t)~t);

[0017] Figure 9 is the relationship curve graph of the removal rate R(t) and time t in Example 6 of the present invention (R(t)~t);

[0018] Figure 10 is the relationship curve graph of the removal rate R(t) and time t in Example 7 of the present invention (R(t)~t);

[0019] Figure 11 is the diagram of the composition structure of the existing zero-valent iron sheet. Detailed implementation manners

[0020] The schematic diagram of the present invention is as Figure 1 shown. The method for improving the efficiency of removing heavy metal ions from wastewater of the present invention includes the following steps:

[0021] 1) Select a cylindrical container 1 that can accommodate zero-valent iron sheets and wastewater;

[0022] 2) Weld wires on both sides of the zero-valent iron sheet 2 in the normal direction. When welding the wire on the side close to the container wall, the oxide layer on the surface of the iron sheet should be ground off to ensure contact between the wire and the Fe of the zero-valent iron sheet. Roll up the zero-valent iron sheet along the side with length L and place it in the cylindrical container 1, close to the container wall, and connect the wire to a DC regulated power supply to apply a DC voltage. Install a stirring device 3 in the cylindrical container; and fill the cylindrical container with wastewater; 0

[0023] 3) Turn on the DC regulated power supply connected to the wire, and at the same time use a reflection device 4 to reflect sunlight to the part of the iron sheet that protrudes from the wastewater container. At this time, the heavy metal wastewater in the cylindrical container can be treated.

[0024] For the welded wire, the oxide layer on the surface of the side of the iron sheet close to the container wall must be ground off and welded to the Fe 0 , and the side facing the wastewater is welded directly without grinding off the oxide film.

[0025] The thickness of the zero-valent iron sheet is 0.1 mm to 1 mm.

[0026] Figure 2 The shape of the zero-valent iron sheet is as Figure 2 shown. The shape of the zero-valent iron sheet is L-shaped, and the horizontal dimension L at the bottom of the L shape is the inner circumference of the cylindrical container.

[0027] The horizontal dimension at the top of the L shape is half of the inner circumference of the cylindrical container.

[0028] The vertical dimension of the L-shaped zero-valent iron sheet is W + x; where W is the height of the cylindrical container, and W + x is nearly 1.5 to 2.0 times the height of the cylindrical container.

[0029] The stirring device is a mechanical stirring rod. The reflection device is a mirror. As Figure 3 shown.

[0030] The positive pole of the DC regulated power supply is connected to the wire connected to the side of the iron sheet facing the wastewater, and the negative pole is connected to the wire connected to the side of the iron sheet close to the container wall. The voltage regulation range is 0.01 - 1 V.

[0031] The stirring rate range of the stirring is 100 - 500 rpm.

[0032] The concentration of heavy metal ions in the heavy metal wastewater in the cylindrical container is tested by an inductively coupled plasma optical emission spectrometer (ICP).

[0033] The method for improving the conductivity of the amorphous thin film layer on the surface of zero-valent iron and the removal rate of zero-valent iron sheets for heavy metals is applied to the treatment of heavy metal wastewater.

[0034] The principle of the present invention is as follows:[[]] Figure 1 As shown in the figure, when the iron sheet is irradiated by sunlight, photo-generated electrons and holes are generated. Under the action of the electrostatic field generated by the DC voltage, the electrons tend to move towards the interface in contact with the wastewater; correspondingly, the positive charges tend to move towards the Fe 0 core. There are three such effects:

[0035] 1) The photo-generated electrons have high energy and are easy to break through the localized states, improving their delocalized properties and becoming more extended states, thereby increasing the conductivity (the original conductivity is denoted as "σ", and the increased conductivity is denoted as "△σ");

[0036] 2) The number of photo-generated electrons is increased, so the number of electrons participating in the redox reaction per unit time is increased. The increased number of photo-generated electrons is denoted as "△n 光 ";

[0037] 3) The photo-generated electrons move directionally towards the interface in contact with the waste liquid under the action of the electrostatic field, and the photo-generated holes move directionally towards the Fe 0 core, attracting the core electrons to move towards the surface in contact with the waste liquid, increasing the probability of non-photo-generated electrons in the amorphous Fe 0 core moving towards the waste liquid as shown in the figure, thereby increasing the number of non-photo-generated electrons participating in the redox reaction per unit time (denoted as "△n Figure 2 "); 非光 ".

[0038] The above three effects (△σ, △n 光 , △n 非光 ) lead to an increase in the number of electrons participating in the redox reaction per unit time, thereby increasing the conductivity of the amorphous thin film layer of the zero-valent iron sheet and the removal rate of heavy metals in the wastewater.

[0039] Wastewater samples are collected regularly to monitor the change in the concentration of heavy metal ions in the wastewater being treated over time until the concentration of heavy metal ions contained therein reaches the discharge standard. The concentration of heavy metal ions in the taken heavy metal wastewater samples is tested by an inductively coupled plasma optical emission spectrometer (ICP).

[0040] The removal rate is calculated by the following formula: R(t) = (C0 - C t ) / C0 × 100%

[0041] where R(t) represents the removal rate after t hours from the start, C0 is the concentration of heavy metal ions in the wastewater at the start of the removal experiment, and C t is the concentration of heavy metal ions in the wastewater after t hours from the start of the removal.

[0042] The following examples use the following simulated wastewater as the removal object, measure the removal rate at each moment t during the removal process, and draw a relationship curve of the corresponding removal rate R(t) and time t (R(t)~t). Since the kinetic type of the removal process is not single and it is difficult to describe it with a pure first-order, second-order or higher-order kinetic model, the original meaning of the removal rate is used here as the removal rate: the slope k of the removal rate at the start time is used as the removal rate in this example. Therefore, the comparison of the removal rates is made using the slope k of the R(t)~t curve at t = 0. For the following heavy metal ions Cu 2+ , Te 4+ , Se 4+ , As 3+ , Bi 3 + , Pb 2+ in specific examples, the k values obtained from the R(t)~t curves are represented by k Cu , k Te , k Se , k As , k Bi , k Pb respectively.

[0043] The composition and concentration of the simulated wastewater are as follows:

[0044] Cu(NO3)2·3H2O, Cu 2+ : (2 g / L);

[0045] Arsenic standard solution 1000 μg / ml, As 3+ : (0.6 g / L)

[0046] Na2SeO3, Se 4+ : (0.1 g / L)

[0047] Na2TeO3, Te 4+ : (0.1 g / L)

[0048] Bi(NO3)3·5H2O, Bi 3+ : (0.03 g / L)

[0049] Pb(NO3)2, Pb 2+ : (0.5 g / L)

[0050] The respective concentrations of the ions shown above are based on 1000 times the discharge standard as the simulated wastewater concentration.

[0051] The specific embodiments of the present invention are as follows:

[0052] Example 1:

[0053] As Figure 3 shown, the transverse dimension L of the L-shaped zero-valent iron sheet (0.1 mm thick) is the inner circumference of the cylindrical wastewater bucket, and the longitudinal dimension W + x of the L-shaped zero-valent iron sheet is 1.5 times the cylindrical height W. Wires are welded on both sides in the normal direction of the zero-valent iron sheet to apply a DC voltage. The surface oxide layer must be ground off on the side of the iron sheet close to the container wall and welded to Fe 0 ; on the side facing the wastewater, it is directly welded without grinding off the oxide film. The zero-valent iron sheet is rolled up along the side with length L and placed in the simulated wastewater container. A mechanical stirrer is added to the simulated wastewater. The wire of the zero-valent iron sheet is connected to the DC regulated power supply. The positive pole of the voltage is connected to the wire on the side of the iron sheet facing the solution, and the negative pole is connected to the wire connected to the side of the iron sheet close to the container wall. At 1:00 pm on October 8, 2023 (the solar radiation measured by the optical power meter is 4589 megajoules per square meter), the wastewater bucket containing the zero-valent iron sheet and the heavy metal simulated wastewater is placed in the sun, and the part of the iron sheet protruding from the wastewater container is irradiated with sunlight. The DC regulated power supply is adjusted to 0.01 V, and the stirring rate of the mechanical stirring is adjusted to 100 rpm. At this time, the simulated heavy metal wastewater in the wastewater bucket can be treated.

[0054] Figure 4 is the R(t)~t relationship curve obtained in this embodiment. Figure 4 There is also the R(t)~t curve with mechanical stirring at a rate of 100 rpm and sunlight (100 rpm, 4489 megajoules per square meter) radiation but without applying a DC voltage for comparison. From Figure 4 it can be calculated that the k Cu 、k Te 、k Se 、k As 、k Bi 、k Pb values obtained after applying mechanical stirring at a rate of 100 rpm, sunlight (100 rpm, 4489 megajoules per square meter) radiation, and a voltage of 0.01 V are respectively: 0.366, 0.997, 0.947, 0.973, 0.112, 0.102; while the corresponding k Cu 、k Te 、k Se 、k As, k Bi , k Pb The values are respectively: 9.136, 11.172, 11.673, 11.802, 8.752, 0.851; The removal rates k Cu , k Te , k Se , k As , k Bi , k Pb after adding a voltage of 0.01V are increased by 24.966, 11.2, 12.322, 12.13, 78.29, 8.371 times respectively (the calculation process is not presented here).

[0055] Example 2:

[0056] As Figure 3 shown, the transverse dimension L of the L-shaped zero-valent iron sheet (0.5 mm thick) is the inner circumference of the cylindrical wastewater bucket, and the longitudinal dimension W + x of the L-shaped zero-valent iron sheet is twice the cylindrical height W. Wires are welded on both sides in the normal direction of the zero-valent iron sheet to apply a DC voltage. The surface oxide layer must be ground off on the side of the iron sheet close to the container wall and welded to Fe 0 ; on the side facing the wastewater, it is welded directly without grinding off the oxide film; the zero-valent iron sheet is rolled up along the side with length L and placed in the wastewater container. A mechanical stirrer is added to the simulated wastewater. The wire of the zero-valent iron sheet is connected to a DC regulated power supply. The positive pole of the voltage is connected to the wire on the side of the iron sheet facing the solution, and the negative pole is connected to the wire connected to the side of the iron sheet close to the container wall. At 1:00 pm on November 12, 2023, the wastewater bucket with the zero-valent iron sheet and the heavy metal simulation is placed in the sun, and the part of the iron sheet protruding from the wastewater container is irradiated with sunlight; the DC regulated power supply is adjusted to 0.01V, and the stirring rate of the mechanical stirring is adjusted to 500 rpm. At this time, the simulated heavy metal wastewater in the wastewater bucket can be treated.

[0057] Figure 5 is the relationship curve graph of the removal rate R(t) and time t obtained in this case (R(t)~t), in which the R(t)~t curve with only the measure of adding sunlight (4401 MJ / m²) under the same conditions, stirring at 100 rpm, and without adding a DC voltage is used for comparison. From Figure 5 it can be calculated that the k Cu , k Te , k Se , k As , k Bi , k PbThe values are respectively: 0.387, 0.979, 0.914, 0.499, 0.195, 0.169; and the corresponding k values of the R(t)~t curve under sunlight (4401 MJ / m²), 500 rpm stirring, and 0.01 V DC voltage Cu , k Te , k Se , k As , k Bi , k Pb The values are respectively: 17.117, 17.598, 18.012, 17.989, 14.527, 2.426; the removal rates k Cu , k Te , k Se , k As , k Bi , k Pb The latter values are respectively 41.652, 17.980, 19.714, 36.039, 74.579, 14.37 times higher than the former (the calculation process is not presented here).

[0058] Example 3:

[0059] As Figure 3 shown, select the horizontal dimension L of the L-shaped zero-valent iron sheet (0.6 mm thick) to be the inner circumference of the cylindrical wastewater bucket, and the longitudinal dimension W + x of the L-shaped zero-valent iron sheet to be 1.8 times the cylindrical height W. Weld wires on both sides in the normal direction of the zero-valent iron sheet to apply a DC voltage. The surface oxide layer on the side of the iron sheet close to the container wall must be ground off and welded to Fe 0 , and directly weld the side facing the wastewater without grinding off the oxide film; roll up the zero-valent iron sheet along the side with length L and place it in the wastewater container. Add a mechanical stirring rod to the simulated wastewater, connect the wire of the zero-valent iron sheet to a DC regulated power supply, connect the positive pole of the voltage to the wire on the side of the iron sheet facing the solution, and connect the negative pole to the wire connected to the side of the iron sheet close to the container wall. At 1 pm on December 3, 2023, place the wastewater bucket containing the zero-valent iron sheet and the simulated heavy metal wastewater in the sun, and irradiate the part of the iron sheet protruding from the wastewater container with sunlight; adjust the DC regulated power supply to 1 V and adjust the stirring rate of the mechanical stirring to 100 rpm. At this time, the simulated heavy metal wastewater in the wastewater bucket can be treated.

[0060] Figure 6 is the relationship curve graph of the removal rate R(t) and time t obtained in this case (R(t)~t), in which the R(t)~t curve without applying a DC voltage under only the same conditions of sunlight radiation (4461 MJ / m²) and stirring at a rate of 100 rpm is used for comparison. From Figure 6It can be calculated that the values of k, k, k, k, k, k obtained after loading solar radiation (4461 MJ / m²), stirring at a rate of 100 rpm but without applying voltage are 0.327, 1.028, 1.042, 0.863, 0.103, 0.14 respectively; while the values of k, k, k, k, k, k, k obtained after having solar radiation (4461 MJ / m²), stirring at a rate of 100 rpm and applying a voltage of 1V are 17.384, 20.063, 19.506, 19.024, 16.552, 3.126 respectively; the removal rates k, k, k, k, k, k calculated therefrom, the latter are 53.162, 19.512, 18.726, 22.046, 161.262, 22.274 times higher than the former respectively (the calculation process is not presented here). Cu k Te k Se k As k Bi k Pb The values are: 0.327, 1.028, 1.042, 0.863, 0.103, 0.14; while for k, k, k, k, k, k, k obtained with solar radiation (4461 MJ / m²), stirring at a rate of 100 rpm and a voltage of 1V Cu k Te k Se k As k Bi k Pb The values are: 17.384, 20.063, 19.506, 19.024, 16.552, 3.126; the removal rates k, k, k, k, k, k calculated therefrom Cu k Te k Se k As k Bi k Pb The latter are 53.162, 19.512, 18.726, 22.046, 161.262, 22.274 times higher than the former respectively (the calculation process is not presented here).

[0061] Example 4:

[0062] As Figure 3 shown, select the transverse dimension L of the L-shaped zero-valent iron sheet (0.7 mm thick) to be the inner circumference of the cylindrical wastewater tank, and the longitudinal dimension W + x of the L-shaped zero-valent iron sheet to be twice the cylindrical height W. Weld wires on both sides in the normal direction of the zero-valent iron sheet to apply a DC voltage. The surface oxide layer on the side of the iron sheet close to the container wall must be ground off and welded to Fe 0 ; directly weld the side facing the wastewater without grinding off the oxide film; roll up the zero-valent iron sheet along the side with length L and place it in the wastewater container. Add a mechanical stirrer to the simulated wastewater. Connect the wire of the zero-valent iron sheet to a DC regulated power supply. Connect the positive pole of the voltage to the wire on the side of the iron sheet facing the solution, and connect the negative pole to the wire connected to the side of the iron sheet close to the container wall. At 1:00 pm on December 18, 2023, place the wastewater tank containing the zero-valent iron sheet and the simulated heavy metal wastewater in the sun, and irradiate the part of the iron sheet protruding from the wastewater container with sunlight; adjust the DC regulated power supply to 1V and adjust the stirring rate of the mechanical stirrer to 500 rpm. At this time, the simulated heavy metal wastewater in the wastewater tank can be treated.

[0063] Figure 7It is the relationship curve graph of the removal rate R(t) and time t obtained in this case (R(t)~t), in which the R(t)~t curve with only sunlight (4438 MJ / m²) and stirring at a rate of 100 rpm added and no DC voltage is compared. From Figure 7 It can be clearly seen that after applying a voltage of 1V and increasing the stirring rate from 100 rpm to 500 rpm, the removal rate has been greatly improved. From Figure 7 It can be calculated that for the case with sunlight (4438 MJ / m²) and stirring at a rate of 100 rpm and no DC voltage applied, the values of k Cu 、k Te 、k Se 、k As 、k Bi 、k Pb are respectively: 0.411, 0.941, 0.925, 0.589, 0.071, 0.203; while for the R(t)~t curve with sunlight (4438 MJ / m²), stirring at a rate of 500 rpm, and a DC voltage of 1V, the corresponding values of k Cu 、k Te 、k Se 、k As 、k Bi 、k Pb are respectively: 18.123, 18.836, 19.607, 18.287, 17.374, 3.239; and the calculated removal rate values of k Cu 、k Te 、k Se 、k As 、k Bi 、k Pb of the latter are respectively 44.082, 20.02, 21.192, 31.06, 243.349, 15.918 times higher than those of the former (the calculation process is not presented here).

[0064] Example 5:

[0065] As Figure 3 shown, the selected horizontal dimension L of the L-shaped zero-valent iron sheet (0.3 mm thick) is the inner circumference of the cylindrical wastewater tank, and the longitudinal dimension W + x of the zero-valent L-shaped iron sheet is 1.9 times the cylindrical height W. Wires are welded on both sides in the normal direction of the zero-valent iron sheet to apply a DC voltage. The surface oxide layer must be ground off on the side of the iron sheet close to the container wall and welded to Fe 0On the side facing the wastewater, it is directly welded without grinding off the oxide film. The zero-valent iron sheets are rolled up along the side with a length of L and placed into the wastewater container. A mechanical stirrer is added to the simulated wastewater. The wire of the zero-valent iron sheets is connected to a DC regulated power supply. The positive pole of the voltage is connected to the wire on the side of the iron sheet facing the solution, and the negative pole is connected to the wire on the side of the iron sheet close to the container wall. At 1:00 p.m. on March 20, 2024, the wastewater bucket containing the zero-valent iron sheets and the simulated heavy metal wastewater is placed under the sun, and the part of the iron sheet protruding from the wastewater container is irradiated with sunlight. The DC regulated power supply is adjusted to 0.5V, and the stirring rate of the mechanical stirring is adjusted to 250 rpm. At this time, the simulated heavy metal wastewater in the wastewater bucket can be treated.

[0066] Figure 8 is the relationship curve graph of the removal rate R(t) and time t obtained in this case (R(t)~t), in which the R(t)~t curve with only sunlight (4455 MJ / m²) and stirring at a rate of 100 rpm added and no DC voltage is used as a comparison. From Figure 8 it can be clearly seen that after applying a voltage of 0.5V and increasing the stirring rate from 100 rpm to 250 rpm, the removal rate has been greatly improved. From Figure 8 it can be calculated that the k values obtained after adding sunlight (4455 MJ / m²) and stirring at a rate of 100 rpm and without applying a DC voltage in the above sense Cu 、k Te 、k Se 、k As 、k Bi 、k Pb are respectively: 5.282, 1.028, 0.971, 0.802, 0.43, 0.214; while the corresponding k values of the R(t)~t curve with sunlight (4455 MJ / m²), stirring at a rate of 250 rpm, and a voltage of 0.5V Cu 、k Te 、k Se 、k As 、k Bi 、k Pb are respectively: 19.374, 18.578, 18.988, 17.718, 15.917, 3.902; the calculated removal rate k values Cu 、k Te 、k Se 、k As 、k Bi 、k Pb of the latter are respectively 3.668, 18.068, 19.552, 22.104, 111.176, 18.271 times higher than those of the former (the calculation process is not presented here).

[0067] Example 6:

[0068] As Figure 3 shown, the selected horizontal dimension L of the L-shaped zero-valent iron sheet (0.1 mm thick) is the inner circumference of the cylindrical wastewater bucket, and the longitudinal dimension W + x of the L-shaped zero-valent iron sheet is twice the cylindrical height W. Wires are welded on both sides in the normal direction of the zero-valent iron sheet to apply a DC voltage. The surface oxide layer must be ground off on the side of the iron sheet close to the container wall and welded to Fe 0 ; on the side facing the wastewater, it is directly welded without grinding off the oxide film. The zero-valent iron sheet is rolled up along the side with length L and placed into the wastewater container. A mechanical stirrer is added to the simulated wastewater. The wires of the zero-valent iron sheet are connected to a DC regulated power supply. The positive pole of the voltage is connected to the wire on the side of the iron sheet facing the solution, and the negative pole is connected to the wire connected to the side of the iron sheet close to the container wall. At 1:00 pm on March 20, 2024, the wastewater bucket containing the zero-valent iron sheet and the simulated heavy metal wastewater is placed in a dark room. The DC regulated power supply is adjusted to 0.5 V, and the stirring rate of the mechanical stirring is adjusted to 250 rpm. At this time, the simulated heavy metal wastewater in the wastewater bucket can be treated.

[0069] Figure 9 is the relationship curve graph of the removal rate R(t) and time t obtained in this case (R(t)~t), in which only the measure of adding mechanical stirring (100 rpm) with a stirring rate of 100 rpm, the radiation of sunlight (4505 MJ / m², irradiating the part of the iron sheet extending out of the wastewater container with sunlight), and the R(t)~t curve without applying a DC voltage are used for comparison. From Figure 9 it can be seen that when the voltage is increased to 0.5 V and at the same time the stirring rate is adjusted from 100 rpm to 250 rpm, but the light radiation is removed, the removal efficiency is still greatly improved, but the improvement rate is a little smaller than that without removing the light radiation (comparison Figure 8 ). Therefore, it shows that light radiation can improve the removal rate, but the improvement amplitude is not large when applying a 0.5 V voltage. From Figure 9 it can be calculated that the k Cu , k Te , k Se , k As , k Bi , k Pb values of the R(t)~t curve with 100 rpm stirring, sunlight radiation (4505 MJ / m²), and without applying a voltage are respectively: 0.367, 0.959, 1.022, 0.659, 0.134, 0.253; while the corresponding k Cu , k Te , k Se , kAs and k Bi and k Pb The values are respectively: 16.6, 19.422, 20.741, 19.453, 15.985, 3.773; the removal rates k Cu and k Te and k Se and k As and k Bi and k Pb The latter values are respectively 45.247, 20.247, 20.287, 29.497, 119.04, 14.929 times higher than the former ones (the calculation process is not presented here).

[0070] Example 7:

[0071] As Figure 3 shown, select the transverse dimension L of the L-shaped zero-valent iron sheet (1 mm thick) to be the inner circumference of the cylindrical wastewater bucket, and the longitudinal dimension W + x of the zero-valent L-shaped iron sheet to be 1.5 times the cylindrical height W. Weld wires on both sides in the normal direction of the zero-valent iron sheet to apply a DC voltage. The surface oxide layer on the side of the iron sheet close to the container wall must be ground off and welded to Fe 0 ; directly weld the side facing the wastewater without grinding off the oxide film; roll up the zero-valent iron sheet along the side with length L and place it in the wastewater container. Add a mechanical stirring rod to the simulated wastewater, connect the wire of the zero-valent iron sheet to a DC regulated power supply, connect the positive pole of the voltage to the wire on the side of the iron sheet facing the solution, and connect the negative pole to the wire connected to the side of the iron sheet close to the container wall. At 1:00 pm on March 20, 2024, place the wastewater bucket containing the zero-valent iron sheet and the simulated heavy metal wastewater in a dark room; adjust the DC regulated power supply to 0 V and adjust the stirring rate of the mechanical stirring to 250 rpm. At this time, the simulated heavy metal wastewater in the wastewater bucket can be treated.

[0072] Figure 10 is the relationship curve graph of the removal rate R(t) and time t obtained in this case (R(t)~t), in which the R(t)~t curve with only the measure of adding mechanical stirring at a stirring rate of 100 rpm (100 rpm), with sunlight radiation (4467 megajoules per square meter) and without applying a DC voltage is used for comparison. From Figure 10 it can be seen that by removing sunlight radiation and adjusting the stirring rate from 100 rpm to 250 rpm, the removal efficiency is still greatly improved, but the improvement rate is a little smaller than that with a voltage of 0.5 V (comparison Figure 9 ). From Figure 10 it can be calculated that without voltage and light radiation, the corresponding k Cu and k Te and k Se and kAs , k Bi , k Pb The values are: 0.385, 0.977, 1.143, 1.124, 0.207, 0.124. After the stirring rate is increased by 2.5 times, the removal rates k Cu , k Te , k Se , k As , k Bi , k Pb The values are: 39.184, 29.925, 27.269, 3.479, 4.335, 0.28. The removal rates are increased by 101.715, 30.625, 23.858, 3.093, 20.893, 2.26 times respectively (the calculation process is not presented here).

Claims

1. A method for improving the efficiency of zero-valent iron flakes in removing heavy metal ions from wastewater, characterized in that It includes the following steps: 1) Select a cylindrical container that can accommodate zero-valent iron sheets and wastewater; 2) Weld wires on both sides in the normal direction of the zero-valent iron sheet. When welding the wire on the side closer to the container wall, grind off the oxide layer on the surface of the iron sheet to ensure contact between the wire and Fe of the zero-valent iron sheet. Roll up the zero-valent iron sheet along the side with length L and place it in a cylindrical container, closely attaching to the container wall. Connect the wire to a DC regulated power supply to apply a DC voltage, install a stirring device in the cylindrical container; and fill the cylindrical container with wastewater; 0 Contact, roll up the zero-valent iron sheet along the side with length L and place it in a cylindrical container, closely attaching to the container wall. Connect the wire to a DC regulated power supply to apply a DC voltage, install a stirring device in the cylindrical container; and fill the cylindrical container with wastewater; 3) Turn on the DC regulated power supply connected by wires, and at the same time use a reflection device to reflect sunlight onto the part of the iron sheet that extends out of the wastewater container. At this time, the heavy metal wastewater in the cylindrical container is treated; The positive pole of the voltage is connected to the wire on one side of the iron sheet facing the solution, and the negative pole is connected to the wire connected to the side of the iron sheet close to the container wall. The voltage adjustment range of the DC regulated power supply is 0.01 - 1V; The light irradiates from the solution side onto the part of the iron sheet that extends out of the wastewater container.

2. The method for improving the efficiency of removing heavy metal ions from wastewater by zero-valent iron flakes according to claim 1, characterized in that The thickness of the zero-valent iron sheet is 0.1 mm to 1 mm.

3. The method for improving the efficiency of removing heavy metal ions from wastewater by zero-valent iron sheets according to claim 1, wherein The shape of the zero-valent iron sheet is L-shaped, and the horizontal dimension L at the bottom of the L shape is the inner circumference of the cylindrical container.

4. The method for improving the efficiency of removing heavy metal ions in wastewater by zero-valent iron flakes according to claim 3, characterized in that The horizontal dimension at the top of the L shape is half of the inner circumference of the cylindrical container.

5. The method for improving the efficiency of zero-valent iron flakes in removing heavy metal ions from wastewater according to claim 3, characterized in that, The longitudinal dimension of the L-shaped zero-valent iron sheet is W + x; where W the height of the cylindrical container, and X is 0.5 to 1 times that of W.

6. The method for improving the efficiency of removing heavy metal ions in wastewater by zero-valent iron sheets according to claim 1, characterized in that, The stirring device is a mechanical stirring rod.

7. The method for improving the efficiency of zero-valent iron flakes in removing heavy metal ions from wastewater according to claim 1, characterized in that, The reflection device is a pot-shaped reflector.

8. The method for improving the efficiency of zero-valent iron flakes in removing heavy metal ions from wastewater according to any one of claims 1 to 7, characterized in that, The stirring rate range of the stirring is 100 - 500 rpm.

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