TWI496616B - Catalyst for heavy metal recovery and methods of production and use the same - Google Patents

Description

Heavy metal recovery agent and its manufacturing and using method

The present invention relates to a heavy metal recovery agent and a method of making and using the same, which can be used to recover metal ions in a solution.

In recent years, despite the rapid development of the industry, the resulting pollution of heavy metal wastewater has become increasingly serious. Its main sources are printed circuit board industry, leather industry, metal surface treatment industry, steel rolling industry, electronics industry and electroplating industry. The waste sludge produced by these industries is mainly composed of copper, lead, zinc and nickel.

Heavy metal wastewater not only causes serious damage to the human body, but also destroys the environment in which humans live. Therefore, how to effectively remove excessive heavy metals in wastewater has become a problem faced by most industrial countries in the world.

In order to make sustainable use of resources and reduce the production of hazardous waste, develop the dissolution and recovery technology of heavy metals in waste, reduce the toxicity of sludge waste, recover valuable metals, reduce environmental load, and promote the sustainable reuse of resources. Issues that must be addressed. At present, there are many methods for treating heavy metal wastewater, including chemical precipitation, ion exchange and biological treatment. Among them, the ion exchange resin method is the basic process for treating heavy metal wastewater at present, and can be used for recovering heavy metals, removing impurities in the plating solution, improving the life of the plating solution, and also treating the heavy metal wastewater at the end of the tube.

The principle of the ion exchange resin method is to use a functional group on the surface of the ion exchange resin material to exchange metal ions having the same electric charge as the functional groups in the solution to remove harmful substances in the solution. The ion exchange resin method has the advantages of high mass transfer rate, high selectivity, and the waste liquid after the reaction can be recycled, and the equipment and operation are simple.

However, most of the reactive functional groups of the ion exchange resin material are located inside the resin, so that there are certain obstacles when the heavy metal ions are exchanged with the functional groups inside the resin, and the effect of the ion exchange resin after the surface functional groups are reacted. Will also decrease. Since the surface reaction position is not much, it is usually necessary to use a large amount of ion exchange resin material to achieve a certain effect.

In the article on pages 257-263 of Hazardous Material, Vol. 158, reveals the use of chromium oxide copper (CuCrO ₂ ) to treat heavy metal ions in solution, including nickel, copper, zinc, cadmium, mercury and silver under certain conditions. Ions, etc., have reducing power. However, the chromium oxide copper prepared by the invention does not have a pore structure, and the recovered heavy metal can only be deposited on the surface. Further, when the recovered heavy metal is separated from the solution, it is easy to peel off the heavy metal which has been recovered from the surface and remain in the solution.

Therefore, a heavy metal reducing agent having a porous structure is developed, and when recovering the reduced metal, heavy metals can be firmly caught to enhance the heavy metal recovery ability, which is a problem to be solved by the present invention.

In view of the above problems, the present invention provides a heavy metal recovery agent comprising an oxide powder having a porous network structure as a catalyst for reducing heavy metals, having an oxide powder surface area of at least more than 10 m ² /g and an oxide of cuprous iron ore. Type, spinel type or a mixture thereof, represented by the general formula AxByOz, wherein A represents a group selected from the group consisting of silver (Ag), copper (Cu), palladium (Pd), platinum (Pt), and any combination thereof. One of them, B is selected from the group consisting of aluminum (Al), strontium (Sc), chromium (Cr), yttrium (Y), iron (Fe), indium (In), gallium (Ga), cobalt (Co), and manganese. One of a group consisting of (Mn), rhodium (Rh), nickel (Ni), lanthanum (La), yttrium (Nd), yttrium (Sm), lanthanum (Eu), titanium (Ti), and any combination thereof .

Another object of the present invention is to provide a method for producing a heavy metal recovery agent having a porous network structure, the heavy metal recovery agent comprising an oxide powder, which may be a cuprite type, a spinel type or a mixture thereof, and a general formula AxByOz The method comprises the steps of: providing a metal salt or an organometallic compound containing A ions and B ions, respectively, and mixing them as a metal precursor; dissolving the metal precursor in a solvent to form a metal precursor solution; The fuel is mixed into the metal precursor solution, wherein the fuel is selected from the group consisting of an amino acid fuel, oxalic acid or borane; the excess water in the metal precursor solution is evaporated to form a colloid; and the colloid is heated to about 150 to 250 ° C to make the colloid A self-ignition reaction is generated, and after the reaction is completed, an oxide AxByOz powder is obtained.

It is still another object of the present invention to provide a method for recovering heavy metals comprising: providing an oxide powder having a porous network structure as a catalyst for reducing heavy metals, having a surface area of at least greater than 10 m ² /g, and an oxide of red copper Iron ore type, spinel type or a mixture thereof, represented by the general formula AxByOz; the oxide powder is put into a solution containing heavy metal ions; the solution is irradiated with a light source to generate an electron-hole pair to reduce the oxide powder to reduce Heavy metal ions in solution. The reduced heavy metal is trapped in the porous network of oxide powder; finally, the oxide powder is separated from the solution by centrifugation to recover heavy metals.

Wherein, when the oxide powder is provided, the energy gap width (Eg) of the oxide powder is further adjusted to select the heavy metal ions to be recovered. Moreover, the photon energy (hv) emitted by the light source used to illuminate the solution must be greater than the energy gap width (Eg) of the oxide.

The heavy metal recovery agent provided by the present invention has a porous network structure and has a large surface area, and therefore, the reaction position with heavy metal ions can be relatively increased. In addition, after the reduction of heavy metal ions, they will be firmly anchored by the network structure, and it is not easy to return to the solution to form pollution. In addition, the equipment cost required for its production method and method of use is very low, and it is suitable for a large number of applications in the industry.

In order to make the above objects, features and advantages of the present invention more comprehensible, the following is a detailed description of the heavy metal recovery agent according to the present invention, its manufacturing and use method, and the accompanying drawings. as follows.

The cuprous iron oxide type oxide has been found to have a wide energy gap and p type conductivity, and has a photocatalytic effect. In the present invention, such an oxide powder is used as a main catalyst for a heavy metal recovery agent to reduce heavy metals. Taking the cuprous iron oxide type copper oxide CuCrO ₂ as an example, an electron-hole pair is generated after the light is irradiated, and the Cu ⁺ ion in the hole and the lattice forms Cu ²⁺ , and the electron and the heavy metal ion M in the solution ²⁺ (M = nickel, copper, gold, cadmium, zinc) acts to reduce to metal M.

Please refer to FIG. 1 , which is a scanning electron micrograph of a copper-copper iron oxide type oxide (CuCrO ₂ ) powder according to an embodiment of the present invention. As can be seen from the figure, the heavy metal recovery agent provided by the present invention has a porous network structure of oxide powder 10 contained in its composition. Further, the oxide powder 10 of the embodiment of the present invention has a surface area of at least more than 10 m ² /g and a crystal grain size of less than 100 nm.

The oxide of the present invention is a cuprite type represented by the formula AxByOz, but a spinel type oxide or a mixed oxide of the two may also be used. Wherein A represents a group selected from the group consisting of silver (Ag), copper (Cu), palladium (Pd), platinum (Pt), and any combination thereof.

The B system is selected from the group consisting of aluminum (Al), strontium (Sc), chromium (Cr), yttrium (Y), iron (Fe), indium (In), gallium (Ga), cobalt (Co), manganese (Mn), One of a group consisting of rhodium (Rh), nickel (Ni), lanthanum (La), yttrium (Nd), yttrium (Sm), lanthanum (Eu), titanium (Ti), and any combination thereof.

In another embodiment, the B metal ion of the oxide powder AxByOz is doped with divalent ions. In a preferred embodiment, A is copper (Cu) and B is selected from the group consisting of aluminum (Al), chromium (Cr), gallium (Ga), iron (Fe), and manganese (Mn).

The invention also provides a method of using a heavy metal recovery agent, please refer to the flow chart shown in FIG. First, it is necessary to provide an oxide powder having a porous network structure as described above, as in step S200.

For the same oxide, not every heavy metal ion can be reduced when reducing heavy metal ions, only when the reduction potential energy (E _red ) of the heavy metal ions falls within the oxide gap width (Eg). Heavy metal ions are easily reduced to metal.

Therefore, the energy gap width (Eg) of the oxide powder AxByOz can be adjusted to select a heavy metal ion to be recovered. For example, A selects copper, and when B selects Al, the energy gap width (E _g ) is about 3.4 eV; while A selects copper, and when B selects Cr, the energy gap width is about 1.28 eV. In addition, it is also possible to change the energy gap width (Eg) by doping other metals.

Next, the oxide powder is introduced into a solution containing heavy metal ions, as by step S205. Before the photoreduction, the pH of the solution can be selectively adjusted to ensure that the reduced heavy metal is not reoxidized to an ionic state, so that the reduction effect is optimized, as in step S206. In a preferred embodiment of the invention, the pH is about 7 to 12, but not limited thereto, and the reduction of heavy metals can also be carried out in an acidic solution.

Next, the solution is irradiated with a light source to cause the oxide powder to generate an electron-hole pair to reduce heavy metal ions in the solution, as by step S210. In the embodiment of the present invention, the illumination source is selected from a conventional light source such as a power saving bulb, an LED lamp, a pulsed laser, a flash lamp, a xenon lamp, a mercury lamp, a halogen lamp, or the like, and is not particularly limited. The irradiation time is adjusted according to the heavy metal recovery agent and the heavy metal ion content in the wastewater, and it is preferably at least 15 minutes or more.

It should be noted that because the oxide powder is a semiconductor, the photon energy (hv) emitted by the light source must be greater than the energy gap width of the oxide powder to allow the electron to transition from the valance band to the conduction band. Generate an electron-hole pair.

Finally, as long as the heavy metal oxide powder is separated from the solution by centrifugation, the heavy metal can be recovered, as in step 215.

The present invention, and experimentally tested the effect of heavy metal recovery agents. First, 0.5 g of copper chrome oxide (CuCrO ₂ ) powder and 1.68 ml (0.85 mM) of tetrachloroauric acid were added and stirred in 25 ml and 75 ml of deionized water, respectively.

Next, the stirred chromium oxide copper (CuCrO ₂ ) aqueous solution was poured into a tetrachloroauric acid solution, and the pH was adjusted. The prepared solution was placed on a stirrer and stirred, and a light-saving bulb was used as a light source. After irradiating for 30 minutes, the solution was centrifuged, decanted, and the solid powder was placed in an oven to be dried.

Fig. 3 is a scanning electron micrograph of a cuprite-type oxide (CuCrO ₂ ) powder prepared according to an embodiment of the present invention after reduction of heavy metals. As can be seen from the figure, a plurality of reduced gold particles 11, i.e., fine white particles in the figure, are dispersed in the oxide 10. Also, the gold particles 11 are apparently coated in the network structure of the oxide 10. This proves that the heavy metal recovery agent of the present invention can not only reduce the metal ions in the solution, but also the heavy metals which have been reduced on the oxide powder are not easily peeled off, and are returned to the solution again.

The invention also provides a method for preparing such an oxide powder having a porous network structure, please refer to the flow chart of FIG. Including: providing a metal salt or an organometallic compound containing A ions and B ions, respectively, as a metal precursor of the catalyst of the present invention, as in step S400.

In a preferred embodiment, the selection of the metal salt can reduce cost and can be one of a group of metal halides, nitrates, acetates, oxalates, sulfates, carbonates, organic acid salts, and any combination thereof. Among them, nitrate or acetate is preferred because it is relatively low in cost. In the examples of the present invention, nitrate is used.

Next, the metal precursor is uniformly dissolved in a solvent to form a metal precursor solution, as by step S405. The solvent is not particularly limited as long as it can uniformly dissolve the metal salt of the precursor or the organometallic compound, and it is preferred that no precipitate be produced. Can be selected from water, alcohols (such as: methanol, ethanol, propanol, isopropanol, ethylene glycol, etc.), or ethers (such as: methyl ethyl ether, ethylene glycol methyl ether, ethylene glycol butyl ether, etc.) One of the groups consisting of any combination thereof.

Next, the fuel is added to the aforementioned metal precursor solution and uniformly mixed, as by step S410. The fuel may be selected from the group consisting of glycine, sarcosine, pyridine, aniline, oxalic acid, hydrazine, and borane. Since the amino acid fuel has a carboxyl group and an amine group and is capable of coordinating with a metal cation to form a stable colloid, in the preferred embodiment of the present invention, an amino acid fuel such as glycine or myoamine is used. Acid, pyridine, aniline, hydrazine, and the like. The amount of fuel used is in the range of about 0.5 to 3 times the molar ratio of total metal ions. Among them, it is preferably 1 to 2 times, more preferably 1.3 to 1.7 times, because in this range, the step of heat treatment after the combustion reaction can be omitted.

After uniformly mixing with the fuel, the metal precursor solution can be placed in an oven to evaporate excess water in the metal precursor solution to dry to a certain extent to form a colloid (which does not need to be completely dried), as in step S415.

Finally, the colloid is placed in an oven or a heating plate to heat it, so that the colloid reaches its spontaneous combustion reaction point, and after the reaction is completed, the product is collected for heat treatment, as in step S420. Among them, the temperature at which the spontaneous combustion reaction occurs is about 150 to 250 °C. The oxide powder prepared in the examples of the present invention has an average particle diameter of about 10 to 300 nm.

After the end of the autoignition reaction, the product after the reaction can be purified to reduce impurities, such as: pickling by filtration. However, the purification step is not limited thereto, and a purification method known to those skilled in the art for filtering impurities may be used, as in step S425.

It is also possible to carry out a dispersion step to increase the dispersion of the cuprite type oxide powder, for example, adding a dispersant or surface modification, as by step S426.

A separate separation step may be selectively performed to reduce the range of the particle size distribution of the powder, as by step S427.

Further, in the oxide powder of the present invention, it was found by X-ray analysis that it had a crystal phase of cuprite ore, and the crystal grain size was in the range of 5 to 50 nm. Among them, the so-called crystal grain size is analyzed by X-ray, and the half-height width (β) of the main peak (Miller index h=0, k=0, l=6) is D=λ/βcosθ according to the Scherrer formula ( D: crystal grain size, λ: X-ray wavelength ( ), θ is the diffraction angle).

In the embodiment of the present invention, after 100 ml of a 1.0 M copper nitrate solution and 100 ml of a 1.0 M chromium nitrate solution are sufficiently dissolved, glycine acid is added as a fuel and a chelating agent with respect to 1.5 times the total metal ion molar amount. When it is completely dissolved, it is placed in an oven to remove excess water and dried to form a colloid. Finally, it was placed on a hot plate to bring the colloid to its self-ignition reaction point, the reaction temperature was about 175 ° C, and the product was collected for analysis after the reaction was completed.

The inventors measured the surface area of the CuCrO ₂ powder by a specific surface area measuring instrument (BET: micromeritics, model: Gemini V) with a nitrogen adsorption curve of about 30.4 m ² /g. On the other hand, in the X-ray analysis, in addition to confirming that the crystal phase of the CuCrO ₂ powder was indeed a cuprite structure, the crystal grain size of the CuCrO ₂ powder was calculated to be about 11 nm. Further, CuFeO ₂ and CuAlO _{2 were} prepared in the same manner, and the crystal grain size and surface area were about 10 to 15 nm and 30 to 35 m ² /g, respectively.

In summary, the heavy metal recovery agent of the present invention can be used to recover heavy metal ions in the waste liquid, thereby reducing its impact on human health and environmental and ecological pollution. It has the following advantages:

(1) With a porous network structure, the surface area available for reaction with heavy metal ions is greatly increased. And after the heavy metal ions are reduced, they are firmly trapped in the network structure, rather than being deposited only on the surface, reducing the chance of metal ions coming off the catalyst.

(2) The use and manufacturing method is simple, and it does not require expensive equipment, which can reduce costs and facilitate market development.

The present invention has been described above by way of a preferred example, but it is not intended to limit the spirit of the invention and the inventive subject matter. Those who are familiar with the technology can easily understand and utilize other components or methods to produce the same effect. Modifications made without departing from the spirit and scope of the invention are intended to be included within the scope of the appended claims.

S200, S201, S205, S206, S210, S215. . . Method of use

S400, S405, S410, S415, S420, S425~S427. . Manufacturing method flow step

10. . . Oxide

11. . . Gold particles

1 shows a scanning electron micrograph of a copper ferrous oxide type oxide (CuCrO ₂ ) powder according to an embodiment of the present invention;

2 is a flow chart showing a method of using a heavy metal recovery agent according to an embodiment of the present invention;

3 is a scanning electron micrograph showing the reduction of heavy metals of the cuprous iron oxide type oxide (CuCrO ₂ ) powder prepared in the embodiment of the present invention;

4 is a flow chart showing a method of manufacturing a metal recycling agent according to an embodiment of the present invention.

10. . . Oxide

11. . . Gold particles

Claims (3)

A method for recovering heavy metals, comprising: providing an oxide powder having a porous network structure as a catalyst for reducing heavy metal ions, the oxide powder having a surface area of at least greater than 10 m ² /g, and the oxide being represented by the general formula AxByOz, Among them, the A system is copper (Cu), and the aluminum (Al), chromium (Cr), gallium (Ga), iron (Fe), manganese (Mn) is selected according to the position of the reduction potential energy of the heavy metal ions to be reduced. Is the B in the oxide formula AxByOz such that the reduction site energy of the heavy metal ion to be reduced falls within the energy gap of the oxide; the oxide powder is put into a solution containing heavy metal ions; Irradiating the solution to cause the oxide powder to generate an electron-hole pair to reduce the heavy metal ions in the solution, and the reduced heavy metal is captured in the porous network structure of the oxide powder; The separation technique separates the oxide powder from the solution to recover heavy metals. The method of claim 1, further comprising doping the A and B atoms to change the x, y, z values to adjust the AxByOz to a predetermined energy gap range. The method of claim 1, wherein the photon energy (hv) emitted by the light source for illuminating the solution is greater than the energy gap width (Eg) of the oxide.