CN112209468A - Method and device for collecting metal by using modified graphene - Google Patents
Method and device for collecting metal by using modified graphene Download PDFInfo
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- CN112209468A CN112209468A CN201910624334.9A CN201910624334A CN112209468A CN 112209468 A CN112209468 A CN 112209468A CN 201910624334 A CN201910624334 A CN 201910624334A CN 112209468 A CN112209468 A CN 112209468A
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/28—Treatment of water, waste water, or sewage by sorption
- C02F1/283—Treatment of water, waste water, or sewage by sorption using coal, charred products, or inorganic mixtures containing them
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
- C02F2101/20—Heavy metals or heavy metal compounds
Abstract
The invention relates to the field of application of graphene materials, in particular to a method and a device for collecting metal by using modified graphene. A method for collecting metal using modified graphene, comprising: (a) preparing modified graphene; (b) setting a filtering and adsorbing layer: the filtering and adsorbing layer comprises modified graphene; (c) inputting wastewater: the wastewater passes through a filtering and adsorbing layer; (d) filtering and adsorbing: sulfur of the modified graphene of the filtering and adsorbing layer adsorbs metals in the wastewater, and liquid molecules and impurities in the wastewater are discharged out of the filtering and adsorbing layer through pores of the modified graphene; and (e) separating the metals: heating the filtering and adsorbing layer with the metal to 350-550 ℃ to boil and volatilize the modified graphene in the filtering and adsorbing layer and leave the metal. The invention further comprises a device for collecting metal by using the modified graphene; by the method and the device, the metal in the wastewater can be effectively adsorbed and recovered.
Description
Technical Field
The invention relates to the field of application of graphene materials, in particular to a method and a device for collecting metal by using modified graphene.
Background
With the development and progress of industrial production, mining and scientific research, a large amount of metals and compounds thereof are discharged into water, wherein the metals and compounds thereof contain various high-concentration toxic heavy metals such As Fe, Cu, Zn, Pb, As, Co, Ni, Cd, Mn, Bi, Hg, Cr, Ti, Au, Ag, U and the like, and even contain radioactive elements, the metals such As Au, Ag, Pt, Pd, Al and the like which can be reused in industry are not lacked. The waste water can cause serious pollution to surrounding water bodies, soil and ecological environment, and metal contained in the waste water is difficult to biodegrade and can be accumulated and transferred after entering the environment or an ecological system, so that the waste water is harmful to human health.
At present, the treatment method of the metal wastewater mainly adopts an adsorption method, and the adsorption method has the advantages of simple operation, excellent effect, higher economic benefit and the like. The most studied adsorbents are mainly: organic adsorbents such as polyethylene, resins, lignin, etc.; inorganic adsorbents such as carbon materials such as activated carbon and carbon nanotubes, iron oxide, fly ash, bentonite, etc.
The organic adsorbent still has the problems of low adsorption efficiency, poor thermal stability, low pollution resistance, short service life and the like. Compared with the inorganic adsorbent, the inorganic adsorbent has the advantages of high adsorption efficiency, acid and alkali resistance, radiation resistance, high temperature resistance, good chemical stability, long service life and the like, and shows good application prospect in wastewater treatment.
Graphene (Graphene) is a novel two-dimensional carbon material consisting of sp carbon atoms2The hybrid orbitals form a hexagonal planar structure with a honeycomb lattice and have a very large specific surface area (2630 m)2(iv)/g); the surface of the material has a large amount of oxygen-containing functional groups, and the material has the characteristics of large adsorption capacity, quick adsorption and the like. However, graphene materials are prone to agglomeration, and functional groups for surface reaction are reduced, so that the adsorption effect and the adsorption selectivity are poor, and the graphene materials are not easy to separate from a solution after being used.
Accordingly, the present inventors have observed the above problems and have made the present invention in view of the fact that there is room for improvement in the conventional methods for treating and recovering metals from wastewater.
Disclosure of Invention
The main object of the present invention is to provide a method and an apparatus for collecting metals using modified graphene, which can efficiently and stably continuously filter and adsorb metals in wastewater using modified graphene in simple steps and structural arrangements.
To achieve the above object, the present invention provides a method for collecting metal by using modified graphene, comprising the steps of: (a) preparing modified graphene: adding graphene and a sulfur-nitrogen compound into water to form a mixture, heating the mixture to 80-100 ℃, refluxing and stirring, then carrying out solid-liquid separation on the mixture, storing a solid part as the modified graphene, wherein the surface of the modified graphene comprises at least one amino group and at least one sulfur; (b) setting a filtering and adsorbing layer: the filtering and adsorbing layer comprises the modified graphene; (c) inputting wastewater: the wastewater passes through the filtering and adsorbing layer; (d) filtering and adsorbing: the sulfur of the modified graphene in the filtering and adsorbing layer adsorbs metals in the wastewater, and liquid molecules and impurities in the wastewater are discharged out of the filtering and adsorbing layer through the pores of the modified graphene; and (e) separating the metals: heating the filtering and adsorbing layer adsorbed with the metal to 350-550 ℃ to boil and volatilize the modified graphene in the filtering and adsorbing layer and leave the metal; wherein, in the step (a), the weight ratio of the graphene to the sulfur-nitrogen compound is 1:2 to 1: 150.
Preferably, in the step (a), the weight ratio of the graphene to the water is between 1:1000 and 1: 1000000.
Preferably, in the step (a), the solid content of the modified graphene is 80 wt% or more.
Preferably, in step (a), the sulfur nitrogen compound is selected from one or a combination of thiourea, thioacetamide, L-cysteine-S-2-thiophene and ammonium dithiocarbamate.
Preferably, in step (a), the refluxing time is 1-8 hours, and the stirring time is 6-12 hours.
Preferably, in step (b), the filtering and adsorbing layer further comprises carbon nanotubes.
Preferably, the weight ratio of the carbon nanotubes to the modified graphene is 1:1 to 10: 1.
Preferably, in the step (c), the weight ratio of the filtration and adsorption layer to the wastewater is 1:15 to 1: 50.
The invention provides a device for collecting metal by using modified graphene, which comprises: a device body, the device body is provided with from top to bottom: the water inlet unit is provided with a water inlet for inputting waste water; the filtering and adsorbing unit is provided with a filtering and adsorbing layer, the filtering and adsorbing layer comprises modified graphene, and the surface of the modified graphene comprises at least one amino and at least one sulfur; the water outlet unit is provided with a water outlet for discharging the treated liquid; the pressure sensing unit is connected with the device body so as to sense the pressure in the device body and display the sensed pressure on a display unit; and the pressure adjusting unit is connected with the device body so as to adjust the pressure in the device body.
Preferably, the apparatus further comprises: and the heating unit is connected with the filtering and adsorbing unit so as to heat the filtering and adsorbing layer and the substances adsorbed by the filtering and adsorbing layer.
The method and the device for collecting metal by using the modified graphene have the advantages of simple process steps, simple equipment, low cost, easy control of reaction process and the like, and are suitable for industrial large-scale production.
Drawings
Fig. 1 is a block flow diagram of a method for collecting metal using modified graphene according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of modified graphene according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of the adsorption of a filtering adsorbent layer according to an embodiment of the present invention;
FIG. 4 is a schematic view of the adsorption of a filtration adsorbent layer according to another embodiment of the present invention;
fig. 5 is a schematic view of an apparatus for collecting metal using modified graphene according to an embodiment of the present invention;
fig. 6 is a schematic view of an apparatus for collecting metal using modified graphene according to another embodiment of the present invention.
Detailed Description
Fig. 1 is a block flow diagram of a method for collecting metal using modified graphene according to an embodiment of the present invention, which discloses a method for collecting metal using modified graphene, comprising the steps of:
(a) preparing a modified graphene (10): adding graphene and a sulfur-nitrogen compound into water to form a mixture, heating the mixture to 80-100 ℃, refluxing and stirring, then carrying out solid-liquid separation on the mixture, storing a solid part as the modified graphene (10), wherein the surface of the modified graphene (10) comprises at least one amino group and at least one sulfur. Therefore, the modified graphene (10) prepared by the method has the advantages of large specific surface area of common graphene, large adsorption capacity and high adsorption speed; meanwhile, the surface of the modified graphene (10) has functional groups which are easy to perform ion exchange with metal ions, so that the adsorption effect is improved, and the defect that common graphene is easy to agglomerate is overcome.
Fig. 2 is a schematic structural diagram of the modified graphene (10) according to an embodiment of the present invention. As shown in fig. 2, the surface of the modified graphene (10) includes at least one amino group (-N) and at least one sulfur (-S); in this example, sulfur is attached to the surface of the modified graphene (10) through an amino group. However, the present invention is not limited thereto as long as the surface of the modified graphene (10) includes an amino group and sulfur.
The graphene may be in the form of a powder or slurry. In a preferred embodiment, in step (a), the graphene powder or slurry used has a particle size of 1-40 μm, more preferably 10-25 μm; the S-N compound (SN compound) is a compound consisting of sulfur and nitrogen, preferably one or a combination of thiourea, thioacetamide, L-cysteine-S-2-thiophene and ammonium dithiocarbamate; the weight ratio of the graphene to the sulfur-nitrogen compound is preferably between 1:2 and 1: 150. The weight ratio of the graphene to the water is between 1:1000 and 1: 1000000; preferably, the refluxing time is 1-8 hours, and the stirring time is 6-12 hours; the solid-liquid separation is performed by at least one of centrifugal separation and water washing filtration, and at least 80 wt% or more of the modified graphene (10) obtained after the solid-liquid separation is solid.
In addition, in the step (a), a trace amount of oxidant can be optionally added into water, and then the graphene and the sulfur-nitrogen compound are added into the water containing the oxidant, so as to increase the defects of the graphene and increase the grafting rate. The oxidant is at least one of sulfuric acid, nitric acid, phosphoric acid, potassium permanganate and sodium nitrate or the combination thereof, and the weight ratio of the oxidant to water is 1-10: 10000.
(b) Setting a filtering and adsorbing layer: the filtration adsorption layer comprises the modified graphene (10). The filtering and adsorbing layer is one or more layers of the modified graphene (10), and pores and channels are formed among the modified graphene (10) and are used for liquid molecules to pass through.
(c) Inputting wastewater: and inputting waste water from one side of the filtering and adsorbing layer, and enabling the waste water to pass through the filtering and adsorbing layer. Preferably, the weight ratio of the filtering and adsorbing layer to the wastewater input once is 1:15 to 1:50, so as to avoid that the filtering channels formed between the modified graphene (10) in the filtering and adsorbing layer are compressed due to the overlarge gravity of the wastewater input.
(d) Filtering and adsorbing: the sulfur of the modified graphene (10) in the filtering and adsorbing layer adsorbs metals in the wastewater, and liquid molecules and impurities in the wastewater are discharged out of the filtering and adsorbing layer through the pores of the modified graphene (10). As shown in fig. 3, the modified graphene (10) of the filtration and adsorption layer adsorbs the metal M through sulfur on the surface thereof.
(e) Separating metals: heating the filtering and adsorbing layer with the metal to 350-550 ℃ to boil and volatilize the modified graphene (10) in the filtering and adsorbing layer and leave the metal.
Generally, elements such as C, S, N are vaporized at 200 ℃ and 500 ℃ and metals are vaporized at 600 ℃ or higher, for example, Fe has a boiling point of 2750 ℃, Na at 798 ℃, Ti at 2640 ℃, Mn at 1962 ℃, Co at 2870 ℃, Cu at 2595 ℃, Ag at 1750 ℃, Sn at 2270 ℃, W at 5927 ℃ and Au at 2807 ℃. Therefore, at a standard atmospheric pressure of 1atm, when the filtering and adsorbing layer is heated to 500 ℃, the main constituent molecules C, S, N of the modified graphene (10) have all left the system due to combustion vaporization, so that the filtering and adsorbing layer only leaves the metal with a higher boiling point.
In the step (e), the pressure of the heating reaction may be appropriately increased, thereby reducing the heating temperature required to vaporize the modified graphene 10.
In another embodiment, the filtering and adsorbing layer further includes carbon nanotubes (20) in addition to the modified graphene (10). The weight ratio of the carbon nanotubes (20) to the modified graphene (10) is preferably 1-10: 1.
The carbon nanotube (20) is a long column-shaped one-dimensional conductive material, and is a tubular structure wound by graphene. The carbon nanotubes (20) having a tubular structure have high crystallinity, high electrical conductivity, high thermal conductivity, and high mechanical strength, but do not have a metal-adsorbing effect. Since the modified graphene (10) is generally sheet-shaped, when the modified graphene (10) is further used with the carbon nanotubes (20), the tubular carbon nanotubes (20) can support the filtering channels between the sheet-shaped modified graphene (10) to prevent the sheet-shaped modified graphene (10) from stacking each other to block the filtering channels; therefore, a large area of filtering channel/space is provided, so that the wastewater can more efficiently flow through the filtering and adsorbing layer, and the adsorption chance is increased.
Fig. 4 is a schematic view of adsorption of the filtration adsorbent layer according to another embodiment of the present invention. As shown in fig. 4, the tubular carbon nanotubes (20) support filtering channels (as indicated by the dashed arrows in fig. 4) between the multiple layers of modified graphene 10, so that the modified graphene (10) has more area to open contact with wastewater input from one side of the filtering and adsorbing layer (the wastewater input direction is indicated by the solid block arrows in the figure) to adsorb metal M.
To further illustrate the technical solution of the present invention, the technical effect of the modified graphene 10 prepared by the present invention is described below by using a preferred embodiment of step (a) of the present invention.
Example 1
(a) Adding 1mg of graphene powder with a particle size of about 20 μm and 2mg of thiourea into 1000ml of water to form a mixture; (b) putting the mixture into a reaction furnace, heating to 80-100 ℃, and refluxing for 3-6 hours at constant temperature; (c) stirring the mixture for about 10 hours to uniformly mix the mixture and cooling the mixture to room temperature; and (d) performing solid-liquid separation on the mixture by centrifugal separation and water washing filtration, and storing a solid part as modified graphene (10), wherein the solid content of the modified graphene (10) is 98.8 wt%. In this example, no oxidizing agent was added to reduce the generation of mixed acid waste liquid.
Example 2
Example 2 was prepared in the same procedure as example 1 except that in example 2, the weight ratio of the graphene powder to the sulfur nitrogen compound was 1: 100. That is, in the step (a), 1mg of graphene powder having a particle size of about 20 μm is mixed with 100mg of thiourea and added to 1000ml of water to form a mixture.
Example 3
(a) Adding 1mg of graphene slurry with the particle size of 1-40 mu m and 100mg of L-cysteine-S-2-thiophene into 1000ml of water to form a mixture, and adding 1ml of sulfuric acid; (b) putting the mixture into a reaction furnace, heating to 80-100 ℃, and refluxing for 4-6 hours at constant temperature; (c) stirring the mixture for about 12 hours to mix the mixture evenly and cooling the mixture to room temperature; and (d) subjecting the mixture to solid-liquid separation by centrifugal separation and water washing filtration, and storing a solid portion as the modified graphene (10), the modified graphene (10) having a solid content of about 95 wt%.
This modified graphene (10) prepared in example 2 is exemplified below, and the following comparative examples are added: (1) unmodified graphene, (2) carbon nanotubes 20(CNT), (3) modified graphene (10) and CNT (weight ratio 1:1) were tested for the metal adsorption capacity of the modified graphene (10) of the present invention.
The testing steps basically comprise: firstly, laying and covering the modified graphene (10) to be tested and each comparative example on a filter screen to be used as a filter layer; about 50ppm of gold (Au) containing solution (original solution to be filtered) is filtered through the filter layer; the filtered clear solution (relative to the original solution) was then removed and the gold (Au) content of the filtered clear solution was measured. Table 1 shows the results of tests performed using 10ml of the modified graphene 10 prepared in example 2 of the present invention and each comparative example as a filter layer in combination with 20ml of a gold-containing solution. The Au content of the filtered solution was measured at two wavelengths, 267.595nm and 242.795nm, respectively, as shown in Table 1.
TABLE 1
The original solution contained 49.72ppm Au when tested at 267.595 nm. After filtration through the unmodified graphene, 48.50ppm of Au remained in the solution, indicating that most of Au remained in the solution and was not adsorbed by the filter layer made of the unmodified graphene, so the unmodified graphene did not have the ability to adsorb Au (or other metals). However, after filtration through the modified graphene (10) of inventive example 2, only 0.50ppm of Au remained in the solution, indicating that 49.22ppm (about 99.0%) of Au had been adsorbed by the filter layer composed of the modified graphene (10) of inventive example 2, and the adsorption effect was excellent.
Meanwhile, in the test using carbon nanotubes 20 (CNTs) composed of carbon molecules as a comparative example, 48.56ppm of Au was still present in the solution after filtration through the CNTs, indicating that most of Au was still remained in the solution, indicating that the CNTs themselves did not have the effect of adsorbing Au. However, after filtering through the modified graphene (10) of example 2 of the present invention and the filter layer composed of CNTs, the solution only has 0.44ppm of Au left, which is slightly better than the result (0.50ppm) of the filter layer composed of the modified graphene (10) of example 2 of the present invention, and shows that when the modified graphene (10) is further used with CNTs prepared in example 2, the tubular CNTs themselves have no effect of absorbing Au, but can support the filter channels between the sheet-shaped modified graphene (10) to prevent the sheet-shaped modified graphene (10) from stacking each other; thereby, the modified graphene (10) has an increased chance of adsorbing Au.
Similarly, when tested at 242.795nm, 49.72ppm of Au remained in solution after filtering through the CNT, again indicating that the CNT itself did not have the effect of adsorbing Au. After filtration through the modified graphene (10) of example 2 of the present invention and the filter layer formed by adding CNT, the solution only has 0.70ppm of Au left, which is slightly better than the result (0.71ppm) of the filter layer formed by only the modified graphene (10) of example 2 of the present invention, and shows that when the modified graphene (10) prepared in example 2 is further used with CNT, the tubular CNT itself has no effect of absorbing Au, but the modified graphene (10) in sheet form can be prevented from stacking each other, so as to increase the chance of absorbing Au by the modified graphene (10).
Both the results measured at both wavelengths 267.595nm and 242.795nm show that the modified graphene (10) prepared according to step (a) of the present invention has a significant gold (Au) adsorption capacity; when the modified graphene (10) is used in combination with CNTs, the adsorption capacity can be further improved.
Although the above example 2 of the step (a) is merely taken as an example, the examples 1, 3 and other examples of the step (a) of the present invention have similar effects, and the description thereof is not repeated here.
In addition, the modified graphene (10) prepared in step (a) of the present invention has a good effect on gold (Au), and also has an adsorption effect on aluminum (Al), nickel (Ni), and cobalt (Co). Particularly, the effect is most excellent for palladium (Pd). The following test was conducted using 50g of the modified graphene (10) prepared according to step (a) example 1 as an example, and tables 2 and 3 show the adsorption effect of the modified graphene 10 on aluminum (Al) and palladium (Pd), respectively.
TABLE 2
| Solution (L) | The original solution | 0.2 | 0.3 | 0.4 |
| Time (min) | 1 | 1 | 1 | 1 |
| Al | 26270ppm | 422ppm | 13000ppm | 22790ppm |
As shown in Table 2, the original solution contained 26270ppm Al. When 0.2L (200ml) of the original solution was filtered through 50g of the modified graphene (10) of example 1 for 1 minute, 422ppm of Al remained in the solution, and 84% of Al was adsorbed by the modified graphene (10), resulting in excellent adsorption effect. However, when the filtered solution was increased to 0.3L, the residual Al content of the solution after 1 minute of filtration was increased to 13000ppm, indicating that 50g of the modified graphene (10) of example 1 had gradually saturated the adsorption effect. When the amount of the filtered solution was increased to 0.4L, Al remaining in the solution after 1 minute of filtration was increased to 22790ppm, indicating that 50g of the modified graphene (10) of example 1 had gradually reached saturation in adsorption effect.
TABLE 3
The modified graphene (10) of example 1, also tested at 50g in table 3, was filtered using a raw solution containing 250ppm of palladium (Pd). When 0.1L of the original solution was filtered through 50g of the modified graphene (10) of example 1 for 1 minute, (n.d) remaining Pd was not detected in the solution, indicating that almost all Pd was adsorbed by the modified graphene (10). Moreover, even if the filtration capacity of the original solution is increased to 1.5L, the modified graphene (10) does not reach saturation, and thus it is considered that the modified graphene (10) prepared in step (a) of the present invention has a particularly excellent effect on Pd.
In addition, the invention also provides a device for collecting metal by using the modified graphene. Fig. 5 is a schematic view of an apparatus for collecting metal using modified graphene according to an embodiment of the present invention, including:
a device body (100), in the embodiment, the device body (100) is a cylindrical body as an example, but the invention is not limited thereto. The device body (100) is provided with from top to bottom:
a water inlet unit (50), wherein the water inlet unit (50) is provided with a water inlet (52) for inputting waste water.
The filtering and adsorbing unit (60) is provided with a filtering and adsorbing layer (62), the filtering and adsorbing layer (62) comprises modified graphene (10), and the surface of the modified graphene (10) comprises at least one amino and at least one sulfur. The modified graphene (10) is substantially prepared through the step (a) in the method for collecting metal by using modified graphene.
Preferably, the filtering and adsorbing unit (60) further comprises a supporting structure 64 for supporting the filtering and adsorbing layer (62) inside the device body (100); the support structure (64) is, for example, but not limited to, a filter screen or a support frame with through holes.
And the water outlet unit (70), the water outlet unit (70) is provided with a water outlet (72) for discharging the treated liquid.
This utilize modified graphene to collect device of metal still includes:
a pressure sensing unit (200), the pressure sensing unit (200) being connected to the device body (100) to sense the pressure inside the device body (100) and display the sensed pressure on a display unit (300). In this embodiment, the pressure sensing unit (200) is a pressure sensor, and the display unit (300) is a pressure gauge; the invention is not so limited.
A pressure adjusting unit (400), the pressure adjusting unit (400) being connected to the apparatus body (100) to adjust the pressure inside the apparatus body (100). In the present embodiment, the pressure adjustment unit (400) is a pressure pump, but the present invention is not limited thereto.
Specifically, the device is used as follows:
wastewater enters the device body (100) from the water inlet (52) of the water inlet unit (50) and flows through the filtering and adsorbing layer (62) from one side of the filtering and adsorbing layer (62) of the filtering and adsorbing unit (60); when the wastewater passes through the filtering and adsorbing layer (62), the sulfur of the modified graphene (10) of the filtering and adsorbing layer (62) adsorbs metals in the wastewater, and liquid molecules and impurities in the wastewater are discharged to the other side of the filtering and adsorbing layer (62) through the pores of the modified graphene (10); the filtered waste water is discharged to the outside of the device through the water outlet (72) of the water outlet unit (70).
In the filtering process, the pressure sensing unit (200) senses the pressure inside the device body (100) and displays the sensed pressure on the display unit (300) so that an operator can observe the pressure inside the device, thereby adjusting the volume of the wastewater entering from the water inlet (52) and avoiding high-pressure danger caused by instant input of a large amount of liquid inside the device body (100).
The pressure adjusting unit (400) is communicated with the device body (100), when the internal pressure of the device body (100) is overhigh, partial gas in the device body (100) can be pumped out to the outside by the pressure adjusting unit (400), so that the internal pressure of the device body (100) is reduced; when the internal pressure of the device body (100) is low, the pressure adjusting unit (400) can provide pressure from the outside to the inside of the device body (100) so as to apply pressure to the wastewater inside the device body (100) and force the wastewater to flow through the filtering and adsorbing layer (62) in an accelerated way, thereby improving the efficiency of adsorption and filtration.
Fig. 6 is a schematic view of an apparatus for collecting metal using modified graphene according to another embodiment of the present invention. In the embodiment, the device body (100) is exemplified by a curved tube, but the invention is not limited thereto. The device for collecting metal by using modified graphene further comprises: a heating unit (500), the heating unit (500) is connected to the filtering and adsorbing unit (60) to heat the filtering and adsorbing layer (62) and the substances adsorbed by the filtering and adsorbing layer. In this embodiment, the heating unit (500) is disposed outside the apparatus body (100) around the filtering and adsorbing unit (600) so that the filtering and adsorbing layer (62) can be directly heated and separated from the metal in the apparatus body (100) without taking out the filtering and adsorbing layer (62) after the wastewater passes through the filtering and adsorbing unit (60). however, the present invention is not limited thereto, and the heating unit 500 may be disposed at a distance from the apparatus body (100) and connected to the filtering and adsorbing unit (60) through a transport unit, not shown, or the like.
Specifically, the heating unit (500) can be heated to at least 350-550 ℃ to boil and volatilize the modified graphene (10) in the filtering and adsorbing layer (62), thereby leaving the metal M in the device body (100). After the modified graphene (10) is volatilized by combustion, the operator resets a new filtration and adsorption layer (62) and continues the wastewater filtration treatment by the apparatus.
It should be noted that, in the embodiment of fig. 5 or fig. 6, the modified graphene (10) may be selected as the filtering and adsorbing layer (62), or the modified graphene (10) and the carbon nanotubes (20) may be selected as the filtering and adsorbing layer (62).
The features of the invention and their expected effects are further set forth below:
according to the method for collecting metal by using modified graphene, disclosed by the invention, the step (a) is to carry out reaction in a water phase, other gas sources (such as inert gas or nitrogen) or strong acid (such as sulfuric acid) are not required to be used for carrying out reaction, and the method is almost non-corrosive to equipment, so that graphene can be safely modified by using easily-stored raw materials and simple steps and equipment, has the advantages of simple process, low cost, easiness in control of a reaction process and the like, and is suitable for industrial large-scale production.
The modified graphene (10) prepared in the step (a) of the invention has an adsorption effect on metals such as gold, aluminum, nickel, cobalt, palladium and the like, can be used in the waste liquid recovery industry to adsorb metals, particularly precious metals, in various waste liquids for recycling, and achieves an environmental protection effect. Also, after the metal is adsorbed, the modified graphene (10) can be easily separated from the adsorbed metal to obtain the metal alone for reuse.
The device for collecting metal by using modified graphene can adsorb metal in wastewater by simple equipment, and can easily separate metal from the filtering and adsorbing layer (62) by using the heating unit (500).
However, the foregoing is only a preferred and enabling embodiment of the present invention. Features of the embodiments may be used in combination with each other instead of or in addition to each other, unless otherwise apparent. Furthermore, all structural changes that are equivalent to those in the specification and claims of the present invention are intended to be included in the scope of the present invention.
The reference numerals are explained below:
10 modifying graphene;
20 carbon nanotubes;
100 a device body;
50 a water inlet unit;
52 a water inlet;
60 a filtration and adsorption unit;
62 filtering the adsorption layer;
64 a support structure;
70, a water outlet unit;
72 water outlet;
200 a pressure sensing unit;
300 a display unit;
400 a pressure adjusting unit;
500 a heating unit;
m metal.
Claims (10)
1. A method for collecting metal by using modified graphene is characterized by comprising the following steps:
(a) preparing modified graphene: adding graphene and a sulfur-nitrogen compound into water to form a mixture, heating the mixture to 80-100 ℃, refluxing and stirring, then carrying out solid-liquid separation on the mixture, storing a solid part as modified graphene, wherein the surface of the modified graphene comprises at least one amino group and at least one sulfur;
(b) setting a filtering and adsorbing layer: the filtration adsorbent layer comprises the modified graphene;
(c) inputting wastewater: the wastewater passes through the filtering and adsorbing layer;
(d) filtering and adsorbing: the sulfur of the modified graphene in the filtering and adsorbing layer adsorbs metals in the wastewater, and liquid molecules and impurities in the wastewater are discharged out of the filtering and adsorbing layer through the pores of the modified graphene; and
(e) separating metals: heating the filtering and adsorbing layer adsorbed with the metal to 350-550 ℃ to boil and volatilize the modified graphene in the filtering and adsorbing layer and leave the metal;
wherein, in the step (a), the weight ratio of the graphene to the sulfur-nitrogen compound is 1:2 to 1: 150.
2. The method of claim 1, wherein in step (a), the weight ratio of the graphene to the water is between 1:1000 and 1: 1000000.
3. The method for collecting a metal using modified graphene according to claim 1, wherein the solid content of the modified graphene in step (a) is 80 wt% or more.
4. The method for collecting metals by using modified graphene according to claim 1, wherein in the step (a), the sulfur-nitrogen compound is one or a combination of thiourea, thioacetamide, L-cysteine-S-2-thiophene and ammonium dithiocarbamate.
5. The method for collecting a metal using modified graphene according to claim 1, wherein in the step (a), the time for refluxing is 1 to 8 hours, and the time for stirring is 6 to 12 hours.
6. The method according to claim 1, wherein in step (b), the filtering and adsorbing layer further comprises carbon nanotubes.
7. The method of claim 6, wherein the weight ratio of the carbon nanotubes to the modified graphene is 1:1 to 10: 1.
8. The method for collecting metals by using modified graphene according to claim 1, wherein in the step (c), the weight ratio of the filtration and adsorption layer to the wastewater is 1:15 to 1: 50.
9. An apparatus for collecting a metal using modified graphene, comprising:
a device body, the device body is provided with from top to bottom:
the water inlet unit is provided with a water inlet for inputting waste water;
the filtering and adsorbing unit is provided with a filtering and adsorbing layer, the filtering and adsorbing layer comprises modified graphene, and the surface of the modified graphene comprises at least one amino and at least one sulfur; and
the water outlet unit is provided with a water outlet for discharging the treated liquid;
the pressure sensing unit is connected with the device body so as to sense the pressure inside the device body and display the sensed pressure on a display unit; and
and the pressure adjusting unit is connected with the device body so as to adjust the pressure inside the device body.
10. The apparatus according to claim 9, further comprising:
and the heating unit is connected with the filtering and adsorbing unit so as to heat the filtering and adsorbing layer and the substances adsorbed by the filtering and adsorbing layer.
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