Method, device and application for treating metals in wastewater

Abstract

This invention relates to a method for treating metals in wastewater, an apparatus for treating metals in wastewater, and the application of self-floating carriers in purifying and / or recovering metals from heavy metal wastewater. The method and apparatus for treating metals in wastewater utilize a self-floating carrier to induce a co-precipitation reaction between the metal, its ligand, and metal ions to form a self-floating sludge. The self-floating sludge comprises the self-floating carrier and metal deposits formed on the surface of the self-floating carrier, thereby enabling the cost-effective enrichment and recovery of metals from wastewater.

Description

Technical Field

[0001] This invention belongs to the field of water treatment, and particularly relates to a method for treating metals in wastewater (preferably including the recovery of metals from wastewater) and an apparatus for treating metals in wastewater (preferably the recovery of metals from wastewater). This invention also relates to the application of self-floating carriers in purifying heavy metal wastewater and / or recovering metals from heavy metal wastewater, wherein the self-floating carrier is selected from hollow glass microspheres. Background Technology

[0002] In the treatment of metal-containing wastewater (especially heavy metal wastewater), most processes purify the wastewater by adding alkaline reagents to precipitate metal ions (especially heavy metal ions) into insoluble metal hydroxide solids. The conversion of metal ions to solids is driven by the supersaturation of metal hydroxides in water. When metals co-precipitate with alkaline reagents, metal hydroxide particles are generated and aggregated through homogeneous nucleation; the higher the supersaturation, the faster the nucleation rate. However, the extremely low solubility constant of metal hydroxides results in extremely high supersaturation in water, leading to rapid nucleation of fine metal hydroxide solids but poor solid-liquid separation characteristics. Although supersaturation can be controlled by slowly adding alkaline reagents to increase the particle size of metal hydroxides, this process often takes several hours, resulting in a significant decrease in treatment efficiency. Therefore, industrial processes often employ coagulation to increase the particle size of metal hydroxides and accelerate the precipitation-solid-liquid separation process.

[0003] However, the loose flocs produced by traditional coagulation and sedimentation methods have a high water content, resulting in soft sludge that is not conducive to long-term preservation. Furthermore, the addition of commonly used iron and aluminum salt coagulants introduces metallic impurities (such as Fe) into the heavy metal sludge. 2+ Fe 3+ Al 3+ This reduces the purity and recyclability of the main metals in the sludge. Therefore, landfill has become the main treatment and disposal method for sludge containing heavy metals and coagulants, but it also leads to environmental pollution to the surrounding soil, water and vegetation.

[0004] Avoiding sludge landfill means seeking a cost-effective and sustainable approach in which the sludge, if its resource concentration is high enough, can be reused as a raw material in the metal refining / electroplating industry. Summary of the Invention

[0005] To address at least one of the aforementioned problems, the present invention provides a novel method for treating metals in wastewater (preferably including the recovery of metals from wastewater) and an apparatus for treating metals in wastewater (preferably the recovery of metals from wastewater). The present invention also relates to the application of self-floating carriers in purifying heavy metal wastewater and / or recovering metals from heavy metal wastewater.

[0006] Specifically, this invention provides:

[0007] 1. A method for treating metals in wastewater, comprising the following steps:

[0008] (S1) Mix the self-floating carrier and metal ligand with wastewater containing metal ions;

[0009] (S2) In the presence of the self-floating carrier, the metal ligand and metal ions react to form self-floating sludge, wherein the self-floating sludge comprises the self-floating carrier and metal deposits formed on the surface of the self-floating carrier; and

[0010] (S3) Collect the self-floating sludge.

[0011] 2. According to the method described in 1 above, the self-floating sludge spontaneously accumulates on the top of the wastewater and separates from the wastewater, and the method further includes the following steps:

[0012] (S4) The collected self-floating sludge is centrifuged to separate the self-floating carrier in the upper part, the water separated from the sludge is retained in the middle part, and the metal deposits are deposited in the lower part.

[0013] 3. The method according to 1 or 2 above, further comprising:

[0014] (S5) Recover elemental metals from the metal deposit.

[0015] 4. According to the method described in step 3 above, step (S5) includes dissolving the metal deposit with acid to obtain a metal solution, and reducing the metal solution by an electrochemical method to obtain elemental metal.

[0016] 5. According to the method described in step 3 above, step (S5) includes calcining and reducing the metal deposit to obtain elemental metal.

[0017] 6. The method according to any one of 2 to 5 above further includes the following steps:

[0018] (S6) Recover the self-floating carrier and return to step (S1).

[0019] 7. The method according to any one of 1 to 6 above, wherein the method does not include the step of adding a coagulant.

[0020] 8. According to any one of 1 to 7 above, the density of the self-floating carrier is 0.1-0.7 g / cm³. 3 ,

[0021] Optionally, the diameter of the self-floating carrier is 1-5000 μm, preferably 10-1000 μm.

[0022] Optionally, the self-floating carrier comprises at least one of hollow glass microspheres, foam, and plastic microspheres.

[0023] 9. The method according to any one of 1 to 8 above, wherein the metal ions in the wastewater are selected from at least one of copper ions, nickel ions, zinc ions, chromium ions, and any combination thereof.

[0024] 10. The method according to any one of 1 to 9 above, wherein the wastewater originates from at least one of wastewater from electroplating, mining wastewater, leather tanning wastewater, battery wastewater, and papermaking wastewater; and

[0025] Optionally, the wastewater contains 10-2000 mg / L, preferably 50-500 mg / L, of metal ions.

[0026] 11. Based on the method described in 4 or 5 above,

[0027] The amount of acid is sufficient to make the pH of the metal solution < 3, and the electrochemical reduction conditions include: using a ruthenium-iridium titanium plate as the anode and the corresponding metal plate as the cathode, with a voltage of 1-20 V and a current of 0.2-10 A; and

[0028] The calcination temperature is 800-1500℃, the reducing atmosphere contains hydrogen or carbon monoxide, and the reducing agent is carbon or aluminum.

[0029] 12. The method according to any one of 1 to 11 above, wherein the density of the self-floating carrier is lower than the density of the wastewater, and the densities of the self-floating carrier, the metal deposit, and the wastewater are all different.

[0030] 13. According to any one of 1 to 12 above, step (S2) includes causing the self-floating support to participate in the co-precipitation reaction of metal ions and metal ligands, resulting in the formation of metal deposits adhering to the surface of the self-floating support under the action of heterogeneous nucleation.

[0031] 14. The method according to any one of 1 to 13 above, wherein the self-floating carrier is selected from at least one of hollow glass microspheres, foam, and plastic microspheres.

[0032] Optionally, the metal ligand is selected from either a base or a sulfide ion.

[0033] 15. An apparatus for treating metals in wastewater, comprising:

[0034] The first container is used to hold the metallic ligands and the self-floating carrier.

[0035] The second container is used to hold wastewater containing metal ions.

[0036] The first conduit is used to mix metal ligands, a self-floating carrier, and wastewater containing metal ions; and

[0037] A solid-liquid separation reactor is used to receive a mixture of metal ligands, a self-floating carrier, and wastewater containing metal ions, and to react the self-floating carrier, the metal ligands, and the metal ions to form self-floating sludge, wherein the self-floating sludge comprises the self-floating carrier and metal deposits formed on the surface of the self-floating carrier.

[0038] 16. The apparatus according to 15 above further includes a centrifuge for centrifuging the collected self-floating sludge, such that the self-floating carrier is separated in the upper part, water separated from the sludge is retained in the middle part, and metal deposits are deposited in the lower part, wherein the inlet of the centrifuge is connected to the upper outlet of the solid-liquid separation reactor.

[0039] 17. The apparatus according to 16 above further includes a recovery device for recovering elemental metal from the metal deposit, wherein the inlet of the recovery device is connected to the lower outlet of the centrifuge.

[0040] 18. The apparatus according to 16 or 17 above further includes a second conduit connected to the upper part of the centrifuge and used to return the self-floating carrier to the first container or the solid-liquid separation reactor.

[0041] 19. The apparatus according to any one of 15 to 18 above, wherein the first conduit is connected to the upper inlet of the solid-liquid separation reactor.

[0042] 20. The apparatus according to 17 above, wherein the recovery apparatus comprises at least one of an electrochemical reactor, a calciner, and a reduction reactor.

[0043] 21. Application of self-floating carriers in the purification of heavy metal wastewater and / or the recovery of metals from heavy metal wastewater, wherein the self-floating carrier is selected from hollow glass microspheres.

[0044] The present invention has the following advantages:

[0045] Compared with the prior art, the method and apparatus for treating metals in wastewater of the present invention produce less sludge, have better dewatering performance, and the self-floating carrier (e.g., low-density hollow glass microspheres) used can be reused.

[0046] In the method and apparatus of the present invention, the generated sludge has the characteristic of low density and can spontaneously float to the surface and separate from the water under the action of buoyancy.

[0047] The method, apparatus, and system of the present invention do not require the addition of coagulants, which significantly reduces the cost of adding chemicals while increasing the dewatering performance and recyclability of sludge.

[0048] The process of this invention is simple, energy-efficient, occupies a small area, has high processing efficiency, good results, and the carrier used is recyclable.

[0049] The method, apparatus, and system of the present invention can meet the continuous inflow and outflow water requirements and have a wider range of applications under continuous flow conditions. Brief description of the attached figures

[0050] Figure 1 This is a schematic diagram of the process and apparatus for a method of treating wastewater and recovering metals according to an embodiment of the present invention.

[0051] Figure 2 The changes in residual metal concentration in the effluent over time are shown for (a) Examples 1, 2, and Comparative Examples 1 and 2, (b) Examples 3, 4, and Comparative Examples 3 and 4, (c) Examples 5, 6, and Comparative Examples 5 and 6, and (d) Examples 7, 8, and Comparative Examples 7 and 8, under conditions of continuous influent and effluent.

[0052] Figure 3 SEM images and photographs of self-floating metal hydroxide-HGM sludge produced by the processes of Examples 9, 10, 11, and 12 are shown, wherein the HGM dosage is constant at 1 mg / mL, and the OH... - The amount is proportional to the positive charge of the metal ions.

[0053] Figure 4 The diagram shows (a) a self-floating device corresponding to an embodiment of the present invention and (b) a precipitation device (b) as a comparative example, wherein [HGM]0 = 1 mg / mL, [Cu 2+ ]0 = [Ni 2+ ]0 = [Zn 2+ ]0= [Cr 3+ ]0 = 50 or 200 mg / L, temperature = 293 K, processing capacity is 9.7 L / h; OH - The amount of [something] and the positive charge of the metal ions are random. Detailed Implementation

[0054] The following definitions are used to understand this invention and to establish the claims.

[0055] Unless otherwise specified, the singular form of "a" in this invention also includes the plural meaning.

[0056] The term "self-floating carrier" in the specification and claims refers to a carrier material with a density lower than water, thus enabling it to float spontaneously in water; preferably, it is an inert material. Preferably, the density of the self-floating carrier is 0.1-0.7 g / cm³. 3 The diameter of the self-floating carrier is 1-5000 μm, preferably 10-1000 μm. The self-floating carrier may contain at least one of hollow glass microspheres, foam, and plastic microspheres.

[0057] In this invention, the self-floating carrier can participate in the co-precipitation reaction of metal ions and ligands in wastewater, resulting in the formation of metal deposits that adhere to the surface of the self-floating carrier under the action of heterogeneous nucleation. The sludge formed spontaneously completes separation and enrichment in the water, thereby purifying metal-containing wastewater and recovering metal resources therein.

[0058] In this paper, "heterogeneous nucleation" refers to the process by which substances dissolved in water spontaneously adhere to the surface of a carrier and form a large amount of solid precipitate during a phase transformation from liquid to solid. In this invention, it refers to the process by which dissolved metal ions, when transformed into solid metal hydroxides, spontaneously adhere to a self-floating carrier and rapidly grow and transform.

[0059] In this paper, "sludge" refers to a loose, mud-like substance formed after a co-precipitation reaction between a self-floating carrier, ligands, and metal ions in wastewater. The sludge formed by this invention is characterized by low density (i.e., lower than the density of water) and can spontaneously float to the surface and separate from the water under buoyancy.

[0060] Unless otherwise specified, the technical and scientific terms used in this invention have the same meanings as those generally accepted by those skilled in the art.

[0061] In this invention, "coagulant" refers to a substance that can bind and aggregate colloidal microparticles in water during the water treatment process. Coagulants are generally classified into two main categories: organic coagulants and inorganic coagulants. The coagulation process involves adding a chemical agent during water treatment to cause impurities to coagulate and flocculate. Commonly used coagulants include iron salts and aluminum salts. In this invention, it is preferable not to add and require no coagulant addition.

[0062] To better understand, and not be limited to, the contents of this invention, unless otherwise specified, all figures including quantities, percentages and proportions in this invention are approximations, obtained from experimental data based on the properties of the corresponding parameters and conventional principles for rounding significant figures.

[0063] To overcome the shortcomings of the prior art, one aspect of the present invention provides a method for treating metals in wastewater, comprising the following steps:

[0064] (S1) Mix the self-floating carrier and metal ligand with wastewater containing metal ions;

[0065] (S2) In the presence of the self-floating carrier, the metal ligand and metal ions react to form self-floating sludge, wherein the self-floating sludge comprises the self-floating carrier and metal deposits formed on the surface of the self-floating carrier; and

[0066] (S3) Collect the self-floating sludge.

[0067] In one embodiment, step (S2) includes engaging the self-floating support in a co-precipitation reaction of metal ions and metal ligands, resulting in the formation of a metal deposit that adheres to the surface of the self-floating support under heterogeneous nucleation.

[0068] In one embodiment, the self-floating sludge spontaneously accumulates on top of the wastewater and separates from the wastewater, and the method further includes the following steps:

[0069] (S4) The collected self-floating sludge is centrifuged to separate the self-floating carrier in the upper part, the water separated from the sludge is retained in the middle part, and the metal deposits are deposited in the lower part.

[0070] In one embodiment, the method of the present invention may further include:

[0071] (S5) Recover elemental metals from the metal deposit.

[0072] In a preferred embodiment, step (S5) may include dissolving the metal deposit with acid to obtain a metal solution, and reducing the metal solution electrochemically to obtain elemental metal. The amount of acid is such that the pH of the metal solution is <3, and the conditions for electrochemical reduction include using a ruthenium-iridium-titanium plate as the anode and the corresponding metal plate as the cathode, with a voltage of 1-20V and a current of 0.2-10A.

[0073] Preferably, step (S5) may include calcining and reducing the metal deposit to obtain elemental metal. The calcination temperature may be 800-1500°C, the reducing atmosphere may contain hydrogen or carbon monoxide, and the reducing agent may be carbon or aluminum.

[0074] In one embodiment, the method of the present invention further includes the following steps:

[0075] (S6) Recover the self-floating carrier and return to step (S1).

[0076] Preferably, the method of the present invention does not include the step of adding a coagulant, that is, no coagulant needs to be added. This significantly reduces the cost of reagent addition while increasing the dewatering performance and recyclability of the sludge.

[0077] In this invention, the density of the self-floating carrier is 0.1-0.7 g / cm³. 3 .

[0078] Optionally, the diameter of the self-floating carrier is 1-5000 μm, preferably 10-1000 μm.

[0079] Optionally, the self-floating carrier comprises at least one of hollow glass microspheres, foam, and plastic microspheres. Preferably, the self-floating carrier is low-density hollow glass microspheres, where low density refers to a density <1 g / cm³. 3 The preferred concentration is 0.1-0.7 g / cm³. 3 Hollow glass microspheres (HGM) are low-density materials at the micrometer scale, mainly composed of amorphous silicon dioxide. HGM typically has a wall thickness of 1-2 μm and an average particle size range of 10-250 μm.

[0080] In one embodiment, the metal ions in the wastewater are selected from at least one of copper ions, nickel ions, zinc ions, chromium ions, and any combination thereof.

[0081] In one implementation scheme, the wastewater may be derived from at least one of the following: wastewater from electroplating processes, mining wastewater, leather tanning wastewater, battery wastewater, and papermaking wastewater.

[0082] Optionally, the wastewater contains 10-2000 mg / L, preferably 50-500 mg / L, of metal ions.

[0083] In one embodiment, the density of the self-floating carrier is lower than the density of the wastewater, and the densities of the self-floating carrier, the metal deposit, and the wastewater are all different.

[0084] Preferably, the metal ligand is selected from at least one of alkali and sulfide ions.

[0085] Reference Figure 4(a) A second aspect of the present invention provides an apparatus 4 for treating metals in wastewater, comprising: a first container for containing a metal ligand 42 and a self-floating carrier 41; a second container for containing wastewater 43 containing metal ions; a first conduit for mixing the metal ligand, the self-floating carrier, and the wastewater containing metal ions; and a solid-liquid separation reactor for receiving the mixed metal ligand, the self-floating carrier, and the wastewater containing metal ions, and for reacting the self-floating carrier, the metal ligand, and the metal ions to form a self-floating sludge 45, wherein the self-floating sludge comprises the self-floating carrier and metal deposits formed on the surface of the self-floating carrier.

[0086] The first pipeline is preferably connected to the upper inlet of the solid-liquid separation reactor.

[0087] The solid-liquid separation reactor also includes an upper inlet for receiving a mixture of metal ligands, a self-floating carrier, and metal ion-containing wastewater 44, and a lower outlet for discharging the treated wastewater 47. The self-floating sludge 45 produced by the solid-liquid separation reactor is located at the top of the reactor and can be discharged from the top into a centrifuge. The separated wastewater 46 is located at the bottom, and the effluent 47 is discharged from the bottom.

[0088] Therefore, the apparatus of the present invention may further include a centrifuge for centrifuging the collected self-floating sludge, such that the self-floating carrier is separated in the upper part, the water separated from the sludge is retained in the middle part, and the metal deposits are deposited in the lower part, wherein the inlet of the centrifuge is connected to the upper outlet of the solid-liquid separation reactor.

[0089] The apparatus of the present invention may further include a recovery device for recovering elemental metals from the metal deposit, wherein the inlet of the recovery device is connected to the lower outlet of the centrifuge.

[0090] Preferably, the apparatus of the present invention further includes a second pipe connected to the upper part of the centrifuge and used to return the self-floating carrier to the first container or the solid-liquid separation reactor.

[0091] In one embodiment, the recovery device includes at least one of an electrochemical reactor, a calciner, and a reduction reactor.

[0092] A third aspect of the invention also provides the application of a self-floating carrier in the purification of heavy metal wastewater and / or the recovery of metals from heavy metal wastewater. The self-floating carrier may be selected from hollow glass microspheres.

[0093] The process and apparatus of the present invention will be further described below using hollow glass microspheres as a self-floating carrier and alkali as a metal ligand as an example, but the present invention is not limited to these examples.

[0094] Figure 1 This is a schematic diagram of a process and apparatus for treating wastewater and recovering metals according to an embodiment of the present invention (also known as the "Hi-Me" heavy metal wastewater treatment and recovery process). The method and apparatus have the functions of treating, separating and recovering heavy metals, including a solid-liquid separation reactor, a centrifugal separation device and a metal reduction device.

[0095] like Figure 1 As shown, hollow glass microspheres 11, alkali 12, and heavy metal wastewater 13 are mixed in a pipeline and fed into the solid-liquid separation reactor 15 from the top. The low-density hollow glass microspheres act as a self-floating carrier and participate in the co-precipitation reaction of heavy metal ions and alkali in the solid-liquid separation reactor. This results in the formation of metal hydroxides that adhere to the surface of the hollow glass microspheres through heterogeneous nucleation. The resulting self-floating sludge 14 spontaneously separates and accumulates in the water, thus purifying the heavy metal wastewater and recovering the metal resources within. When hollow glass microspheres participate in the co-precipitation reaction of metal ions and alkali, they act as nucleation centers, allowing solid metal hydroxides to form on the surface of the microspheres. The more regular arrangement of the metal hydroxides effectively reduces the sludge volume. Simultaneously, the hollow glass microspheres, as a carrier with self-floating capability, have a density lower than water, causing the sludge to spontaneously float and complete solid-liquid separation. Hollow glass microspheres possess stable chemical properties and are extremely difficult to react with acids. Therefore, the collected, self-floating sludge can be dissolved again with acid to precipitate a metal solution with extremely high concentrations, and the separated hollow glass microspheres can be reused. Thus, it is feasible to utilize reusable hollow glass microspheres to participate in heterogeneous nucleation of metal hydroxides to purify heavy metal wastewater and recover high-concentration metal solutions.

[0096] like Figure 1 As shown, the co-precipitation reaction of metal wastewater 13, alkali 12, and hollow glass microspheres 11, as well as the self-floating solid-liquid separation process, occurs in the solid-liquid separation reactor 15. Since the surface free energy barrier required for heterogeneous nucleation of metal hydroxide on the surface of hollow glass microspheres is much lower than that for homogeneous nucleation without hollow glass microspheres, solid metal hydroxide can spontaneously adhere to the surface of the hollow glass microspheres and rapidly form sludge with self-floating capability. The self-floating sludge collected from the top of the reactor then enters a centrifuge. Due to the significant density difference between the hollow glass microspheres, water, and metal hydroxide, the low-density hollow glass microspheres are separated at the top of the centrifuge tube and reused, the water separated from the sludge is retained in the middle of the centrifuge tube, and the high-density metal hydroxide is deposited at the bottom of the centrifuge tube for further recovery. The separated metal hydroxide can be dissolved again with acid to obtain a high-concentration metal solution, which can then be reduced to elemental metal through an electrochemical process (e.g., electroplating), or directly reduced and recovered through high-temperature calcination.

[0097] Figure 1 The process may include the following steps:

[0098] (1) Mix the heavy metal polluted wastewater 13, alkali 12 and hollow glass microsphere carrier 11 and pump them into the column solid-liquid separation reactor 15;

[0099] (2) The sludge 14 that has floated and accumulated at the top of the reactor is collected and sent to the centrifuge 19 for separation and dewatering, and the hollow glass microspheres 16 are recovered; the effluent from the centrifuge and the solid-liquid separation reactor 15 can be combined into the total effluent 18, and

[0100] (3) The separated metal hydroxide solid 21 is dissolved in acid 20 to obtain a high-concentration metal solution (the metal concentration can reach 10000-30000 mg / L, preferably 18000-22000 mg / L) and then electrochemically processed. Figure 1 Electroplating 22) is reduced to 24, or 24 is reduced by high-temperature calcination 23 to obtain elemental metal 25.

[0101] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to examples. It should be understood that the specific examples described herein are merely illustrative and not intended to limit the invention.

[0102] example

[0103] Example 1

[0104] Please see Figure 1 The "Hi-Me" heavy metal wastewater treatment and recycling process in Example 1 includes a mixing influent assembly, a solid-liquid separation reactor, and a metal recycling assembly connected in sequence.

[0105] In this embodiment, copper (Cu) containing metal ions is selected. 2+ The feasibility of using electroplating wastewater as a pollutant in the system was assessed. The columnar solid-liquid separation reactor used was 85 cm long and 4.4 cm in inner diameter. Copper (Cu) containing metal ions was mixed in the pipeline at a volume ratio of 1:1:1. 2+ Electroplating wastewater, HGM (model iM16K, purchased from 3M™, Minnesota, USA), and an alkaline solution (sodium hydroxide solution, dosage controlled to maintain pH 10-10.5) were continuously fed into and out of the reactor to obtain a mixture. This mixture was pumped into a solid-liquid separation reactor to initiate a co-precipitation reaction and complete self-floating solid-liquid separation. The hydraulic retention time (HRT) was approximately 8 minutes, and the total operating time was 40 minutes. The initial metal concentration in the influent to the solid-liquid separation reactor was 200 mg / L. Hydroxide (OH-) ions participated in the reaction. -The molar amount of HGM is the same as the molar amount of the positive charge of the metal ion. The HGM concentration is 1 mg / mL under all conditions. Before testing the heavy metal concentration, 15 mL of sample is mixed with 0.1 mL of 10% concentrated sulfuric acid to dissolve the metal hydroxide.

[0106] After treating 8 L of 200 mg / L heavy metal wastewater, the self-floating sludge enriched at the top of the solid-liquid separation reactor was washed with ultrapure water to remove any possible sodium. + SO4 2- and NO3 - Ions. The water content of the sludge was further reduced by filtration, and then dried at 323 K for 48 hours. The dried heavy metal sludge cake was dissolved in 80 mL of 5% concentrated sulfuric acid solution to recover the heavy metals.

[0107] Comparative Example 1

[0108] according to Figure 4 (b) shows the process and apparatus for processing copper (Cu) containing metal ions. 2+ Electroplating wastewater. Figure 4 In (b), container 42 contains alkali, and wastewater 43 containing metal ions is located in another container. The initial metal concentration in the wastewater is 200 mg / L. The alkali used is sodium hydroxide; its concentration is used to control the pH of the mixed solution to 10-10.5. Sludge 49 produced by the solid-liquid separation reactor is located in the lower part of the reactor and is discharged from the lower part 50. The separated wastewater 46 is located in the upper part.

[0109] Example 2

[0110] Wastewater treatment was carried out in accordance with the method of Example 1, except that the initial metal concentration of the wastewater entering the solid-liquid separation reactor was 50 mg / L.

[0111] Comparative Example 2

[0112] Wastewater treatment was basically carried out according to the method of Comparative Example 1, except that the initial metal concentration of the wastewater entering the solid-liquid separation reactor was 50 mg / L.

[0113] Example 3

[0114] The wastewater treatment was basically carried out according to the method in Example 1, except that the electroplating wastewater used contained metal ions Ni. 2+ Ni 2+ The concentration of the recovered solution is 19,645 mg / L to meet the requirements of industrial electroplating.

[0115] Comparative Example 3

[0116] The wastewater treatment was basically carried out according to the method in Comparative Example 1, the difference being that the electroplating wastewater used contained metal ions Ni.2+ .

[0117] Example 4

[0118] Wastewater treatment was carried out in accordance with the method of Example 3, except that the initial metal concentration of the wastewater entering the solid-liquid separation reactor was 50 mg / L.

[0119] Comparative Example 4

[0120] Wastewater treatment was basically carried out in accordance with the method of Comparative Example 3, except that the initial metal concentration of the wastewater entering the solid-liquid separation reactor was 50 mg / L.

[0121] Example 5

[0122] The wastewater treatment was basically carried out according to the method in Example 1, except that the electroplating wastewater used contained the metal ion Zn. 2+ Zn 2+ The concentration of the recovered solution is 19,696 mg / L to meet the requirements of industrial electroplating.

[0123] Comparative Example 5

[0124] The wastewater treatment method is basically the same as in Comparative Example 1, except that the electroplating wastewater used contains the metal ion Zn. 2+ .

[0125] Example 6

[0126] Wastewater treatment was carried out in accordance with the method of Example 5, except that the initial metal concentration of the wastewater entering the solid-liquid separation reactor was 50 mg / L.

[0127] Comparative Example 6

[0128] Wastewater treatment was basically carried out according to the method of Comparative Example 5, except that the initial metal concentration of the wastewater entering the solid-liquid separation reactor was 50 mg / L.

[0129] Example 7

[0130] The wastewater treatment was basically carried out according to the method in Example 1, except that the electroplating wastewater used contained the metal ion Cr. 3+ Cr 3+ The concentration of the recovered solution is 18,898 mg / L to meet the requirements of industrial electroplating.

[0131] Comparative Example 7

[0132] The wastewater treatment method is basically the same as in Comparative Example 1, except that the electroplating wastewater used contains the metal ion Cr. 3+ .

[0133] Example 8

[0134] Wastewater treatment was carried out in accordance with the method of Example 7, except that the initial metal concentration of the wastewater entering the solid-liquid separation reactor was 50 mg / L.

[0135] Comparative Example 8

[0136] Wastewater treatment was basically carried out in accordance with the method of Comparative Example 7, except that the initial metal concentration of the wastewater entering the solid-liquid separation reactor was 50 mg / L.

[0137] Examples 9-12

[0138] Wastewater treatment in Examples 9, 10, 11, and 12 was carried out according to the methods of Examples 1-4, with the difference being that the wastewater was mixed with alkali and HGM for 1 minute and then floated in a reactor for 5 minutes, wherein the dosage of HGM was kept constant at 1 mg / mL, and OH... - The amount is proportional to the positive charge of the metal ions. SEM images and photographs of the generated self-floating metal hydroxide-HGM sludge are shown below. Figure 3 As shown in (a)-(d).

[0139] Example 13

[0140] Example 13 was performed according to the method of Example 1, except that the sludge from the upper part of the reactor was introduced into… Figure 1 In the centrifuge apparatus shown, the metal deposit obtained from the bottom of the centrifuge is dried at 323 K for 48 hours. The dried metal deposit is dissolved in 80 mL of 5% concentrated sulfuric acid solution to obtain a high-concentration metal solution, copper (Cu). 2+ The concentration of the recovered solution is 16,186 mg / L to meet the requirements of industrial electroplating.

[0141] Example 14

[0142] Wastewater treatment was basically carried out according to the method in Example 1, except that the wastewater contained copper (Cu). 2+ , Nickel 2+ Zinc (Zn) 2+ and chromium Cr 3+ .

[0143] Test case

[0144] After diluting the hollow glass microspheres in Examples 1, 3, 5, and 7 by 100-fold dilution, a high-concentration metal solution of copper (Cu) was obtained by inductively coupled plasma optical emission spectrometry (ICP-OES). 2+ , Nickel 2+ Zinc (Zn) 2+ and chromium Cr3+ The concentrations of the recovered solutions were 19,115 mg / L, 19,645 mg / L, 19,696 mg / L and 18,898 mg / L, respectively, all of which met the requirements for industrial electroplating.

[0145] The changes in residual metal concentration in the effluent of Examples 1, 2, 1, 2, 3, 4, 3, 4, 5, 6, 7, 8, 7, and 8 over time were also tested using inductively coupled plasma optical emission spectrometry (ICP-OES). Figure 2 The test results are shown.

[0146] SEM images and photographs were also taken of the self-floating metal hydroxide-HGM (iM16K from 3M™) sludge produced by the processes of Examples 9, 10, 11, and 12. The samples were sputter-coated with gold for 2 min before SEM testing to ensure their conductivity, and the test voltage was 15 keV. Figure 3 SEM images and photographs of self-floating metal hydroxide-HGM sludge produced by the processes of Examples 9, 10, 11, and 12 are shown. These SEM images and photographs clearly demonstrate that the method of the present invention effectively separates the metal-containing sludge from the wastewater, with the sludge positioned at the top. Furthermore, the surface of the hollow glass microspheres is coated with metal hydroxide.

[0147] Through processing-separation-filtration-redissolution (i.e.) Figure 1 The processing performance and recycling performance of Examples 1, 3, 5, 7, and 14 within one cycle were tested using the processing flow method. Table 1 shows the test data for Examples 1, 3, 5, 7, and 14.

[0148] Table 1

[0149]

[0150] As can be seen, the method of the embodiments of the present invention has a high removal efficiency of heavy metals (more than 90%, preferably more than 95%), and has excellent processing capacity (more than 2.0 L / h, preferably more than 10 L / h) and a high metal recovery rate (more than 85%, preferably more than 90%). In addition, the HGM recovery rate can reach more than 85%, preferably more than 90%.

[0151] in conclusion

[0152] As can be seen from the above embodiments and comparative examples, the method and apparatus of the present invention have at least one of the following characteristics:

[0153] 1) Utilizing low-density hollow glass microspheres as a carrier and core to induce the formation of self-floating heavy metal sludge;

[0154] 2) The metal phase transformation caused by the co-precipitation reaction of the base ligand with the metal ion is a necessary step for its heterogeneous nucleation with the hollow glass microspheres.

[0155] 3) The ligands of the metal ions are not limited to bases, but can also be sulfide ions;

[0156] 4) Centrifugation can be used as a low-energy method to separate metals from the surface of hollow glass microspheres;

[0157] 5) Both hollow glass microspheres and metals can be recycled and recycled in this process;

[0158] 6) Metal recovery methods include, but are not limited to, acid redissolution and electrochemical / calcination reduction.

[0159] 7) Since the heterogeneous nucleation process does not significantly alter the physicochemical properties of the support, the self-floating support participating in heterogeneous nucleation has excellent recyclability, which further reduces processing costs.

[0160] 8) The coagulation-sedimentation method currently in common use is difficult to achieve resource recovery of metals in the treatment of heavy metal wastewater. The "Hi-Me" technology described in this invention has the characteristic of high-efficiency recovery of metal resources, which is a good supplement and improvement to the traditional treatment process.

[0161] It should be understood that the methods and apparatus of the present invention are not limited to the specific embodiments described above, but cover any and all embodiments implemented by the embodiments described herein within the general language range of the following claims, or terms otherwise shown in the drawings or described above, sufficient to enable those skilled in the art to prepare and use the claimed subject matter.

Claims

1. A method for treating metals in wastewater, characterized in that... Includes the following steps: (S1) Mix the self-floating carrier and metal ligand with wastewater containing metal ions; (S2) In the presence of the self-floating carrier, the metal ligand and metal ions react to form self-floating sludge, wherein the self-floating sludge comprises the self-floating carrier and metal deposits formed on the surface of the self-floating carrier; and (S3) Collect the self-floating sludge; The metal ligand is selected from either a base or a sulfide ion. The density of the self-floating carrier is 0.1-0.7 g / cm³. 3 , The density of the self-floating carrier is lower than that of the wastewater, and the densities of the self-floating carrier, the metal deposit, and the wastewater are all different.

2. The method according to claim 1, characterized in that... The self-floating sludge spontaneously accumulates on the top of the wastewater and separates from the wastewater, and the method further includes the following steps: (S4) The collected self-floating sludge is centrifuged to separate the self-floating carrier in the upper part, the water separated from the sludge is retained in the middle part, and the metal deposits are enriched in the lower part.

3. The method according to claim 1 or 2, characterized in that... The method further includes: (S5) Recover elemental metals from the metal deposit.

4. The method according to claim 3, characterized in that... Step (S5) includes dissolving the metal deposit with acid to obtain a metal solution, and reducing the metal solution by an electrochemical method to obtain elemental metal.

5. The method according to claim 3, characterized in that... Step (S5) includes calcining and reducing the metal deposit to obtain elemental metal.

6. The method according to claim 2, characterized in that... It also includes the following steps: (S6) Recover the self-floating carrier and return to step (S1).

7. The method according to claim 1, characterized in that... The method does not include the step of adding a coagulant.

8. The method according to claim 1, characterized in that... The diameter of the self-floating carrier is 1-5000 μm.

9. The method according to claim 8, characterized in that... The diameter of the self-floating carrier is 10-1000 μm.

10. The method according to claim 1, characterized in that... The metal ions in the wastewater are selected from at least one of copper ions, nickel ions, zinc ions, chromium ions, and any combination thereof.

11. The method according to claim 1, characterized in that... The wastewater comes from at least one of the following: wastewater from electroplating, mining, leather tanning, battery manufacturing, and papermaking.

12. The method according to claim 1, characterized in that... The wastewater contains 10-2000 mg / L of metal ions.

13. The method according to claim 12, characterized in that... The wastewater contains 50-500 mg / L of metal ions.

14. The method according to claim 4 or 5, characterized in that, The amount of acid is sufficient to make the pH of the metal solution <3, and the conditions for electrochemical reduction include: using a ruthenium-iridium titanium plate as the anode, a corresponding metal plate as the cathode, a voltage of 1-20V, and a current of 0.2-10A; and The calcination temperature is 800-1500℃, the reducing atmosphere contains hydrogen or carbon monoxide, and the reducing agent is carbon or aluminum.

15. The method according to claim 1, characterized in that... Step (S2) involves having the self-floating support participate in the co-precipitation reaction of metal ions and metal ligands, and the induced metal deposits attach to the surface of the self-floating support under the action of heterogeneous nucleation.

16. The method according to claim 1, characterized in that... The self-floating carrier is selected from at least one of hollow glass microspheres, foam, and plastic microspheres.

17. An apparatus for treating metals in wastewater according to the method of claim 1, characterized in that... include: The first container is used to hold the metallic ligands and the self-floating carrier. The second container is used to hold wastewater containing metal ions. The first conduit is used to mix metal ligands, a self-floating carrier, and wastewater containing metal ions; and A solid-liquid separation reactor is used to receive a mixture of metal ligands, a self-floating carrier, and wastewater containing metal ions, and to react the self-floating carrier, the metal ligands, and the metal ions to form self-floating sludge, wherein the self-floating sludge comprises the self-floating carrier and metal deposits formed on the surface of the self-floating carrier.

18. The apparatus according to claim 17, characterized in that... It also includes a centrifuge device for centrifuging the collected self-floating sludge, such that the self-floating carrier is separated in the upper part, the water separated from the sludge is retained in the middle part, and the metal deposits are enriched in the lower part, wherein the inlet of the centrifuge device is connected to the upper outlet of the solid-liquid separation reactor.

19. The apparatus according to claim 18, characterized in that... It also includes a recovery device for recovering elemental metals from the metal deposit, wherein the inlet of the recovery device is connected to the lower outlet of the centrifuge.

20. The apparatus according to claim 18 or 19, characterized in that... It also includes a second pipe connected to the upper part of the centrifuge and used to return the self-floating carrier to the first container or solid-liquid separation reactor.

21. The apparatus according to claim 17, characterized in that... The first pipeline is connected to the upper inlet of the solid-liquid separation reactor.

22. The apparatus according to claim 19, characterized in that... The recovery device includes at least one of an electrochemical reactor, a calciner, and a reduction reactor.

23. The application of the method according to any one of claims 1 to 16 or the apparatus according to any one of claims 17 to 22 in purifying heavy metal wastewater and / or recovering metals from heavy metal wastewater, wherein the self-floating carrier is selected from hollow glass microspheres.

Images