CN113106254B - Method for extracting nano noble metal and fine iron powder from municipal sludge - Google Patents
Method for extracting nano noble metal and fine iron powder from municipal sludge Download PDFInfo
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- CN113106254B CN113106254B CN202110312018.5A CN202110312018A CN113106254B CN 113106254 B CN113106254 B CN 113106254B CN 202110312018 A CN202110312018 A CN 202110312018A CN 113106254 B CN113106254 B CN 113106254B
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B7/00—Working up raw materials other than ores, e.g. scrap, to produce non-ferrous metals and compounds thereof; Methods of a general interest or applied to the winning of more than two metals
- C22B7/006—Wet processes
- C22B7/007—Wet processes by acid leaching
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B1/00—Preliminary treatment of ores or scrap
- C22B1/02—Roasting processes
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B11/00—Obtaining noble metals
- C22B11/04—Obtaining noble metals by wet processes
- C22B11/042—Recovery of noble metals from waste materials
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- Y02P10/20—Recycling
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Abstract
The invention discloses a method for extracting nano noble metals (mainly Au and Pt) and fine iron powder from municipal sludge. The method specifically comprises the following steps: (1) roasting the dewatered sludge under nitrogen, and magnetically separating to extract iron concentrate powder; (2) impregnating the non-magnetic product with hydrochloric acid/nitric acid solution, burying residues or making building materials, and adjusting pH of leachate to 6-8 with NaOH; (3) the leachate was then mixed with ethanol: mixing n-hexane according to a volume ratio of 1:1:2, adding a proper amount of sodium oleate, refluxing for 2 hours at 65-75 ℃, carrying out oil phase rotary evaporation to recover n-hexane, and using residues for metallurgy; (4) adding 0.1-10 parts by weight of oleylamine into the aqueous phase solution, mixing the oleylamine with n-hexane according to the volume ratio of 1:1, reacting at the temperature of 180-220 ℃ for 2-12h, cooling and centrifuging to obtain the noble metal nano particles. The invention realizes the comprehensive utilization of the municipal sludge as resources and can obtain two high value-added products of the iron concentrate and the noble metal nano particles.
Description
Technical Field
The invention relates to the field of solid waste recycling, in particular to a method for extracting nano noble metals (mainly Au and Pt) and fine iron powder from municipal sludge.
Background
With the development of industrial production and the continuous increase of urban population, the generation amount of urban sewage is increasing.
Municipal sewage comprises industrial and municipal sewage, the water quality is complex, the produced sludge contains various metals (As, Zn, Ni, Cd, Cr, Cu, Pb, Fe, Ag, Au, Pt) and nutrient components (organic matters, nitrogen, phosphorus, potassium and the like), and if the municipal sludge containing various metals and nutrient components cannot be used well, the problems of secondary pollution of land and the like are caused, and valuable metals in the sludge are lost. In addition, 30% to 50% of the annual operating costs of sewage treatment plants are used for sludge treatment, so that efficient treatment of municipal sludge and cost reduction have become a concern and a focus of research of experts in the related industry.
The urban sludge is treated according to the principles of resource utilization, reduction, harmlessness and stabilization internationally. The current municipal sludge treatment modes mainly comprise sanitary landfill, land utilization and incineration, and although the methods relieve the treatment pressure of the municipal sludge, the methods also cause the problems of secondary pollution of the land and the like and cause the loss of some valuable metals in the sludge.
Because a polyferric flocculant is generally used in the process of urban sewage sedimentation, a large amount of iron elements (up to 783.4-3096.0 mg.kg) are contained in the sludge-1Dry weight) as can be recovered, additional benefits can be generated from municipal sludge treatment. However, there are few reports on the extraction of Fe from sludge.
Noble metals such as Au and Pt have high conductivity and corrosion resistance, and cannot be replaced by common metals in the field of electronic product manufacturing. The limited supply of noble metals in nature and the continuous increase of the demand of the electronic industry have led organizations such as the european union to mark noble metals such as Au and Pt as important resources.
Although municipal sludge contains a small amount of precious metal elements such as Au, Pt, Pd, etc., the recovery of precious metals from municipal sludge becomes a challenging research topic with a wide commercial prospect due to the low concentration.
The municipal sludge is derived from the metabolism and biosynthesis of microorganisms, and researches show that the utilization of the microorganisms for consuming the nutrient components in the municipal sludge in an aerobic or anaerobic mode is one of the ways for efficiently treating the municipal sludge and recycling the municipal sludge while enriching the metal elements.
Scientists find that the urban sludge is decomposed by using the microbial bacteria, and find that extracellular polymers of the bacteria can be combined by metal ions through net supplement, adsorption, coagulation and the like, so that the effect of effective precipitation is achieved. Scientists also found brown algae to have a high adsorption of au (iii) at room temperature at pH 7 (DOI:10.1016/j. jhazmat.2008.11.064).
The modified Escherichia coli for scientific and household use can recover Pt in laboratory wastewater, and the maximum adsorption amount of Pt can reach 108.8 mg/g-1(DOI:10.1016/j. biortech.2009.09.056). This means that the precious metal content of the sludge treated by the microorganisms can reach the precious metal ore content level. However, there are currently few reports on the applications associated with the extraction of precious metals from sludge.
Phase transfer is a method for large-scale extraction of metal ions from aqueous phase by usingThe surfactant is complexed with metal ions in the water phase at the interface of the oil phase/the water phase, the complex ions after complexation move from the water phase to the oil phase, and then the water phase is removed through liquid separation to obtain the purified metal/surfactant complex. And since common metal ions are usually in the form of hydrated cations M (H)2O)n +xThe noble metal is usually present in the form of a complex anion [ AuCl ]4]-、[PtCl4]-There is, therefore, a higher selectivity of separation can be achieved by batch-wise extraction of the ordinary metal elements and the noble metal elements in the aqueous phase using the anionic surfactant and the cationic surfactant, respectively.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a method for extracting nano noble metal and fine iron powder from municipal sludge.
The invention is realized by the following technical scheme:
(1) roasting and magnetic separation: roasting 100 weight parts of dewatered municipal sludge in the nitrogen or argon atmosphere at the roasting temperature of 500-800 ℃, and converting the iron-containing component in the municipal sludge into Fe3O4And (3) an isomagnetic component. And (3) carrying out magnetic separation on the product of the roasting of the municipal sludge, wherein the magnetic component is iron concentrate powder with industrial use value.
(2) Acid liquor immersion washing: mixing 100 parts by weight of hydrochloric acid/nitric acid solution with 40 parts by weight of non-magnetic product obtained by roasting municipal sludge, and leaching for 2 hours under heating/ultrasonic conditions. The mixture after the soaking is centrifuged, and the insoluble residue obtained after the centrifugation can be used as a common building material or buried. The leachate obtained after centrifugation is properly concentrated and the pH is adjusted to 6-8 by sodium hydroxide (or potassium hydroxide).
(3) Sodium oleate extracts common metals: mixing 100 weight parts of concentrated neutral leaching solution and 0.1-10 weight parts of sodium oleate, and stirring for 0.5h to fully complex the sodium oleate with transition metal cations in the water phase. Adding a proper amount of ethanol and normal hexane into the leaching solution to ensure that the leaching solution: ethanol: the volume ratio of n-hexane is 1:1:2, and the two-phase system is stirred and refluxed for 2 hours at the temperature of 65-75 ℃. And standing the solution for layering after stirring and refluxing are finished, wherein the upper oil phase is n-hexane containing transition metal oleate, and the lower water phase is a water/ethanol/noble metal ion mixed solution. After the liquid separation operation, the upper oil phase recovers n-hexane through rotary evaporation, and the residual solid is a metal salt/sodium oleate complex which can be used as a raw material in the metallurgical industry.
(4) Extracting noble metals from oleylamine: mixing the aqueous phase solution obtained after the liquid separation with n-hexane of equal volume, adding 0.1-10 parts by weight of oleylamine, and carrying out solvothermal reaction at 180-220 ℃ for 2-12 hours. And after the reaction is finished, cooling and carrying out liquid separation treatment, adding a proper amount of ethanol (1/3-1/2 of the volume of the n-hexane) into the n-hexane solution, centrifuging to obtain the noble metal nanoparticles, and adding the noble metal nanoparticles into the n-hexane for dispersion and storage to obtain the monodisperse noble metal nanoparticles.
Compared with the prior art, the invention has the following advantages and effects:
the invention realizes the comprehensive utilization of the municipal sludge as resources, carries out process adjustment according to different compositions of the municipal sludge, further obtains two main products of the iron concentrate and the noble metal nano particles, and takes the byproduct residue as a building material or a metallurgical raw material.
The process for extracting the iron concentrate powder and the noble metal nano particles from the municipal sludge provided by the invention not only reduces the operation cost of a municipal sewage treatment plant, but also improves the resource utilization rate of metal elements in the municipal sludge. And the whole process does not produce excrement harmful to the environment, thereby meeting the requirements of environmental protection and long-term sustainability and providing a scheme with economic benefit for municipal sludge treatment.
The method can extract fine iron powder and noble metal nanoparticles from municipal sludge by roasting, magnetic separation and surfactant extraction. The method can efficiently treat the municipal sludge, and can obtain iron concentrate powder and noble metal nanoparticles with commercial values, thereby providing a green, environment-friendly, sustainable and high-benefit scheme for the recycling comprehensive utilization of the municipal sludge.
The method is mainly characterized in that a scheme for treating the municipal sludge is optimized by adjusting factors such as the addition amount of the municipal sludge, the roasting temperature, the roasting time, the roasting atmosphere, the ratio and the addition amount of acid, the final pH value of a leachate, the addition amount of sodium oleate, the reaction time of sodium oleate and transition metal, the addition amount of oleylamine, the reaction time of oleylamine and noble metal ions, the reaction temperature, the volume ratio of the leachate/ethanol/normal hexane and the like, and iron fine powder and noble metal nano particles with industrial use values are obtained.
Drawings
FIG. 1 is a schematic view of the process flow of extracting nano noble metal and fine iron powder from municipal sludge.
Fig. 2 is an XRD pattern of the fine iron powder obtained in example 1 of the present invention.
FIG. 3 is an SEM photograph of a metal salt obtained in example 2 of the present invention.
FIG. 4 is an SEM picture of sodium oleate obtained in example 2 of the present invention.
Fig. 5 is a TEM image of the monodisperse noble metal nanoparticles obtained in example 3 of the present invention.
Detailed Description
The present invention will be described in further detail with reference to specific examples.
Example 1:
roasting 100 parts by weight of dewatered municipal sludge at 800 ℃ in argon atmosphere, and carrying out magnetic separation on the roasted product to obtain a magnetic component, namely iron fine powder with industrial use value, wherein an XRD (X-ray diffraction) pattern of the iron fine powder is shown in figure 2.
Taking 50 parts by weight of the rest nonmagnetic components to dissolve in 100 parts by weight of the following components in a volume ratio of 1:1 in hydrochloric acid/nitric acid solution and leaching for 2h under heating/ultrasonic conditions. The leached mixture is centrifuged and the insoluble residue obtained after centrifugation is treated as a common building material.
The leachate obtained after centrifugation is concentrated and the pH is adjusted to 6.5 with sodium hydroxide.
Taking 100 parts by weight of leachate with pH value of 6.5, adding 10 parts by weight of sodium oleate, stirring for 0.5h, and adding appropriate amount of ethanol and n-hexane to make the leachate: ethanol: the volume ratio of normal hexane is 1:1:2, and the two-phase system is stirred and refluxed for 2 hours at the temperature of 70 ℃.
After stirring and refluxing, standing and layering the solution, removing the n-hexane phase on the upper layer through liquid separation operation, recovering the n-hexane through rotary evaporation, and obtaining the residual solid which is a complex of other metal salts/sodium oleate; the lower water phase is a water/ethanol/noble metal ion mixed solution, the mixed solution is supplemented with n-hexane with the same volume, 10 parts by weight of oleylamine is added, and the solvent thermal reaction is carried out for 4 hours at 180 ℃.
And after the reaction is finished and cooled, removing the water phase through liquid separation, adding a proper amount of ethanol into the n-hexane solution (the volume ratio of the ethanol to the n-hexane is 1:2), centrifuging to obtain the noble metal nanoparticles, and adding the noble metal nanoparticles into the n-hexane for dispersion and storage to obtain the monodisperse noble metal nanoparticles.
Example 2:
roasting 100 parts by weight of dewatered municipal sludge at 700 ℃ in nitrogen atmosphere, and carrying out magnetic separation on the roasted product to obtain a magnetic component, namely the iron concentrate powder with industrial use value.
Taking 50 parts by weight of the rest nonmagnetic components to dissolve in 50 parts by weight of the following components in a volume ratio of 3: 1 in hydrochloric acid/nitric acid solution and leached for 0.5h under heating/ultrasonic conditions.
The leached mixture is centrifuged and the insoluble residue obtained after centrifugation is treated as a common building material. The leachate obtained after centrifugation is concentrated and the pH is adjusted to 7 with sodium hydroxide.
Taking 100 parts by weight of leachate with pH value of 7, adding 10 parts by weight of sodium oleate, stirring for 0.5h, and adding appropriate amount of ethanol and n-hexane to ensure that the leachate: ethanol: the volume ratio of n-hexane is 1:2:3, and the two-phase system is stirred and refluxed for 2 hours at the temperature of 70 ℃.
After stirring and refluxing, standing and layering the solution, removing the n-hexane phase on the upper layer through liquid separation operation, recovering n-hexane through rotary evaporation, wherein the residual solid is a complex of other metal salts/sodium oleate, and the morphology of the complex is shown in a figure (3); the lower water phase is a water/ethanol/noble metal ion mixed solution, the mixed solution is supplemented with n-hexane with the same volume, 10 parts by weight of oleylamine is added, and the solvent thermal reaction is carried out for 4 hours at the temperature of 200 ℃.
And after the reaction is finished and cooled, removing the water phase through liquid separation, adding a proper amount of ethanol into the n-hexane solution (the volume ratio of the ethanol to the n-hexane is 1:3), centrifuging to obtain the noble metal nanoparticles, and adding the noble metal nanoparticles into the n-hexane for dispersion and storage to obtain the monodisperse noble metal nanoparticles.
Example 3:
roasting 100 parts by weight of dewatered municipal sludge at 750 ℃ in a nitrogen atmosphere, and carrying out magnetic separation on a roasted product to obtain a magnetic component, namely the iron concentrate powder with industrial use value.
Taking 50 parts by weight of the rest nonmagnetic components to dissolve in 100 parts by weight of the following components in a volume ratio of 3: 1 in hydrochloric acid/nitric acid solution and leaching for 1h under heating/ultrasonic conditions.
The leached mixture is centrifuged and the insoluble residue obtained after centrifugation is treated as a common building material. The leachate obtained after centrifugation is concentrated and the pH value is adjusted to 8 by sodium hydroxide.
Taking 100 parts by weight of leachate with pH value of 8, adding 5 parts by weight of sodium oleate, stirring for 2 hours, and adding appropriate amount of ethanol and n-hexane to ensure that the leachate: ethanol: the volume ratio of n-hexane is 2:1:3, and the two-phase system is stirred and refluxed for 3 hours at the temperature of 70 ℃.
After stirring and refluxing, standing and layering the solution, removing the n-hexane phase on the upper layer through liquid separation operation, recovering the n-hexane through rotary evaporation, and obtaining the residual solid which is a complex of other metal salts/sodium oleate; the lower water phase is a water/ethanol/noble metal ion mixed solution, the mixed solution is supplemented with n-hexane with the same volume, 20 parts by weight of oleylamine is added, and the solvent thermal reaction is carried out for 8 hours at the temperature of 200 ℃.
After the reaction is finished and cooled, removing the water phase through a liquid separation operation, adding a proper amount of ethanol into the n-hexane solution (the volume ratio of the ethanol to the n-hexane is 1:2), centrifuging to obtain the noble metal nanoparticles, and adding the noble metal nanoparticles into the n-hexane for dispersion and storage to obtain the monodisperse noble metal nanoparticles (the morphology of which is shown in figure 5).
As described above, the present invention can be preferably realized.
The embodiments of the present invention are not limited to the above-described embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and they are included in the scope of the present invention.
Claims (2)
1. A method for extracting nano noble metal and fine iron powder from municipal sludge is characterized by comprising the following steps:
step one, roasting and magnetic separation:
roasting 100 weight parts of dewatered municipal sludge in protective atmosphere and in argon or nitrogen atmosphere for 0.5-5h at 500-800 ℃ to convert the iron-containing component in the municipal sludge into Fe3O4A magnetic component; carrying out magnetic separation on the product of the roasting of the municipal sludge to obtain a magnetic component, namely iron concentrate powder;
step two, acid liquor immersion washing:
mixing 100 parts by weight of mixed solution of hydrochloric acid and nitric acid with 40 parts by weight of non-magnetic product obtained after roasting municipal sludge, and leaching for 2 hours under heating/ultrasonic conditions; centrifuging the mixture after soaking, wherein insoluble residues obtained after centrifugation can be used as building materials or buried; concentrating the leachate obtained after centrifugation, and adjusting the pH value to 6-8 by using sodium hydroxide or potassium hydroxide;
step three, extracting transition metal cations by sodium oleate:
mixing 100 parts by weight of the concentrated leaching solution with 0.1-10 parts by weight of sodium oleate, and stirring for 0.5h to fully complex the sodium oleate with transition metal cations in a water phase; adding ethanol and n-hexane into the leachate obtained in the second step, wherein the volume ratio of the leachate to the ethanol to the n-hexane is 1:1:2, and the two-phase system is stirred and refluxed for 0.5 to 4 hours at the temperature of 65 to 75 ℃; after stirring and refluxing, standing and layering the solution, wherein the upper oil phase is n-hexane containing transition metal oleate, and the lower water phase is a mixed solution of water, ethanol and noble metal ions; after the liquid separation operation, recovering n-hexane from the upper oil phase through rotary evaporation, wherein the residual solid is a metal salt and a sodium oleate complex compound and can be used as a raw material in the metallurgical industry;
step four, extracting noble metal anions by using oleylamine:
mixing the aqueous phase solution obtained after the third liquid separation step with n-hexane with the same volume, adding 0.1-10 parts by weight of oleylamine, and carrying out solvothermal reaction at the temperature of 180-220 ℃ for 2-12 hours; after the reaction is finished, cooling and carrying out liquid separation treatment, adding ethanol into the n-hexane solution, wherein the amount of the ethanol is 1/3-1/2 of the volume of the n-hexane, centrifuging to obtain noble metal nanoparticles, and adding the noble metal nanoparticles into the n-hexane for dispersion and storage to obtain monodisperse noble metal nanoparticles, wherein the noble metal nanoparticles mainly comprise Au and Pt and can be used in a catalyst;
the process for extracting the iron concentrate and the noble metal nanoparticles from the municipal sludge not only reduces the operation cost of a municipal sewage treatment plant, but also improves the resource utilization rate of metal elements in the municipal sludge, and the whole process does not produce excrement harmful to the environment, thereby meeting the requirements of environmental protection and long-term sustainability.
2. The method for extracting nano precious metals and fine iron powder from municipal sludge according to claim 1, wherein the method comprises the following steps: and step two, the volume ratio of the nitric acid to the hydrochloric acid in the mixed solution of the hydrochloric acid and the nitric acid is 1: 1-5.
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