CN113549762B - Separation and extraction process of rare noble metals in electronic waste - Google Patents

Separation and extraction process of rare noble metals in electronic waste Download PDF

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CN113549762B
CN113549762B CN202110674871.1A CN202110674871A CN113549762B CN 113549762 B CN113549762 B CN 113549762B CN 202110674871 A CN202110674871 A CN 202110674871A CN 113549762 B CN113549762 B CN 113549762B
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chitosan
palladium
stirring
cellulose
platinum
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CN113549762A (en
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陈灿
曾露
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Suzhou Furong Environmental Protection Technology Co ltd
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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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F9/00—Making metallic powder or suspensions thereof
    • B22F9/02—Making metallic powder or suspensions thereof using physical processes
    • B22F9/04—Making metallic powder or suspensions thereof using physical processes starting from solid material, e.g. by crushing, grinding or milling
    • 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
    • C22B1/005—Preliminary treatment of scrap
    • 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
    • C22B11/046—Recovery of noble metals from waste materials from manufactured products, e.g. from printed circuit boards, from photographic films, paper or baths
    • 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
    • C22B11/06—Chloridising
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

Abstract

The invention discloses a separation and extraction process of rare noble metals in electronic wastes. The method specifically comprises the following steps: pretreatment; grinding and milling; acid leaching with hydrochloric acid; recovery of platinum; recovery of palladium; leaching with aqua regia; recovering gold; and (5) reduction. The beneficial effects are that: (1) Grinding and co-milling a potassium persulfate-sodium chloride mixture and metal powder to increase the leaching rate and recovery rate of palladium and platinum; (2) The continuous grading extraction process is adopted to successfully recycle 3 noble metals: preferentially precipitating platinum with 2-ethylhexyl amine, separating platinum from palladium, and increasing the purity of the recovered palladium; selectively recycling palladium by using chitosan-cellulose compound, shielding impurity metals and improving palladium purity; high purity gold is recovered rapidly and selectively with modified chitosan-cellulose complexes.

Description

Separation and extraction process of rare noble metals in electronic waste
Technical Field
The invention relates to the technical field of precious metal recovery, in particular to a separation and extraction process of rare precious metals in electronic wastes.
Background
In recent years, rapid expansion of the electronic product market has led to an increase in the demand for noble metals. Meanwhile, the faster changing speed of the electronic products leads to accumulation of electronic wastes, which causes environmental pollution. Therefore, the electronic waste is used as a new noble metal resource, the cyclic utilization of the noble metal resource is sequentially generated, and the environmental pollution is reduced to become a research hot spot.
Common chemical methods for recovering the olefinic noble metal from the electronic waste include pyrometallurgy and hydrometallurgy. Wherein, the pyrometallurgy is easy to produce more organic pollution gas due to the need of burning and smelting, thereby causing environmental pollution. Hydrometallurgy is carried out by dipping with acid liquor and alkali liquor, and finally obtaining high-purity alkene noble metal through extraction, replacement and other processes. At present, more researches are conducted on single noble metal recovery, and the process for classifying and purifying various noble metals is few. In addition, most of the prior art uses a solvent extraction process, so that the metal recovery rate is low, the requirement on a solvent extractant is high, and the solvent extractant cannot be reused; is easy to cause solvent pollution. In the process of extracting noble metals from the adsorbent, the adsorbent can be reused for multiple times, so that the cost and the solvent pollution are reduced. However, because the single selectivity of the adsorbent to similar metals is poor (such as separation of palladium and platinum), the purity of the extracted single noble metal is affected, and therefore, the design of a separation and extraction process for the rare noble metals in the electronic waste has important significance in the fractional extraction of three noble metals of platinum, palladium and gold.
Disclosure of Invention
The invention aims to provide a separation and extraction process of rare noble metals in electronic wastes, which aims to solve the problems in the background technology.
In order to solve the technical problems, the invention provides the following technical scheme:
a separation and extraction process of rare noble metals in electronic waste comprises the following steps:
s1: pretreatment: crushing and sieving the electronic waste, and sieving by a high-voltage electrostatic separator and a magnetic separator in sequence to obtain metal powder;
s2: grinding and milling: grinding and co-milling the metal powder and the potassium persulfate-sodium chloride mixture to obtain a metal concentrate;
s3: acid leaching with hydrochloric acid: immersing the metal enrichment in hydrochloric acid solution, immersing, and filtering to obtain metal liquid A and filter residues;
s4: recovery of platinum: adding 2-ethylhexyl amine into the metal liquid A, mixing and stirring, and centrifugally separating to obtain metal liquid B and platinum precipitate;
s5: recovery of palladium: adding the chitosan-cellulose compound into the metal liquid B, mixing and stirring, and filtering to obtain a palladium precipitate;
s6: acid leaching with aqua regia: placing the filter residue in the step S3 into aqua regia, soaking and filtering to obtain a metal liquid C;
s7: recovery of gold: adding the modified chitosan-cellulose compound into the metal liquid C, mixing and stirring, and filtering to obtain a gold precipitate;
s8: and (3) reduction: placing the platinum precipitate into perchloric acid solution for eluting, enriching and reducing to obtain a platinum simple substance; and respectively eluting the palladium precipitate and the gold precipitate in thiourea solution, and enriching and reducing to obtain elemental palladium and elemental gold.
More optimally, in the step S2, the mass ratio of the metal powder to the potassium persulfate-sodium chloride mixture is (1:1) - (1:3); the mass ratio of the potassium persulfate-sodium chloride mixture is (1:1) - (3:1); the grinding co-milling speed is 500-600 rpm, and the grinding time is 0.5-2 hours.
More preferably, in step S3, the pH of the hydrochloric acid solution=1 to 2; the solid-liquid ratio of the impregnation is (1:5) - (1:10); the dipping temperature is 25-40 ℃; the soaking time is 1-3 hours.
More optimally, in the step S4, the addition amount of the 2-ethylhexyl amine is 0.6-0.8 g/L; the stirring speed is 250-320 rmp, and the stirring time is 30-60 minutes.
More preferably, in the step S5, the adding amount of the chitosan-cellulose compound is 6-8 g/L; the stirring speed is 150-220 rpm, and the stirring temperature is 18-25 ℃; the stirring time is 3-5 hours.
More optimally, the preparation method of the chitosan-cellulose composite comprises the following steps: dissolving chitosan in 1-4% acetic acid solution to obtain solution A; dissolving dialdehyde carboxymethyl cellulose in deionized water to form a solution B with the concentration of 8-12 g/L; mixing the solution A and the solution B, setting the temperature to be 45-55 ℃ for reaction for 5-6 hours, adding acetone for precipitation, filtering, washing and drying to obtain a chitosan-cellulose compound; the cross-linking ratio of the chitosan to the dialdehyde carboxymethyl cellulose is (1:0.5) - (1:1).
More optimally, in the step S6, the solid-to-liquid ratio of the aqua regia acid leaching is (1:1) to (1:2); the dipping temperature is 70-80 ℃; the soaking time is 1-3 hours.
More preferably, in the step S7, the addition amount of the modified chitosan-cellulose compound is 6-10 g/L; the stirring speed is 250-320 rpm, and the stirring temperature is 18-20 ℃; the stirring time is 3-5 hours.
More optimally, the preparation method of the modified chitosan-cellulose compound comprises the following steps: placing the chitosan-cellulose composite in a sealed bag, purging with nitrogen for 3-5 minutes, and irradiating a sample with grafting measurement of 2-8 kGy by adopting a 1MeV electron accelerator; adding glycidyl methacrylate and a surfactant into a sealing belt, setting the temperature to be 50 ℃ and reacting for 2 hours in a water bath, washing and filtering to obtain an epoxidation compound; and adding the modified chitosan-cellulose composite into a DMF solution of L-cysteine, setting the temperature to be 70-90 ℃ and reacting for 20-28 hours, and carrying out low-temperature vacuum drying to obtain the modified chitosan-cellulose composite.
More optimally, in the step S8, the concentration of the perchloric acid is 1-1.2 mol/L; the concentration of the thiourea solution is 0.25-0.5 mol/L.
In the technical scheme, the electronic waste is crushed, partial organic matters are removed through a high-voltage electrostatic separator, and iron powder is removed through screening of a magnetic separator; then, the leaching rate and the recovery rate of palladium and platinum are increased by grinding and co-milling the metal powder; then leaching with hydrochloric acid to obtain a metal liquid A (containing Pt, pd, cu, zn and other light metals) and filter residues (containing Au); 2-ethylhexyl amine was used for selective precipitation of Pt; the chitosan-cellulose compound is used for selective adsorption of Pd, and finally, the chitosan-cellulose compound is respectively desorbed in a perchloric acid solution and a thiourea solution, and the elementary platinum and the elementary palladium are obtained through reduction; simultaneously, soaking the filter residue again with aqua regia; and leaching Au, selectively adsorbing by using a modified chitosan-cellulose complex, desorbing in a thiourea solution, and reducing to obtain elemental gold. Thus, noble metals Pt, pd and Au are separated and extracted. The method comprises the following steps:
(1) Grinding and milling: in the co-milling process, potassium persulfate in a mixture of potassium persulfate and sodium chloride is used as an oxidant, and sodium chloride is used as a ligand; during grinding and co-milling of potassium persulfate and palladium and platinum, crystal grains are thinned to generate lattice defects, so that the diffusion of the mixture and metal powder is increased, the potassium persulfate is converted into sulfate to play an oxidation role, and then stable chelate is formed with sodium chloride; meanwhile, metals such as copper and the like are added in the hydrochloric acid solution in the process, so that leaching of hetero ions is reduced in the aqua regia gold leaching process. In the process, only a very small amount of gold is likely to be dissolved, the gold is almost insoluble, and most gold is required to be dissolved in aqua regia.
(2) Acid leaching in a hydrochloric acid solution having a ph=1 to 2 to form (PdCl 4 ) 2− 、(PtCl 4 ) 2− To separate the two, it is preferable to precipitate the platinum ion using 2-ethylhexyl amine, since 2-ethylhexyl amine is a fatty platinum amine containing 8 carbon chains, less than 9 carbons, which can be combined with (PdCl 4 ) 2− Form a water-soluble ion pair, but (PdCl 4 ) 2− The solubility in hydrochloric acid solution was extremely high, and therefore, it was impossible to precipitate (PdCl 4 ) 2− But (PtCl) 4 ) 2− The ion pair formed therewith is insoluble in water and thus can form a selective precipitate. Thus, platinum is preferentially separated and extracted;
（3）the glutaraldehyde is replaced by the dialdehyde carboxymethyl cellulose to crosslink chitosan to form a compound, so that the stability of the chitosan-cellulose compound in acid liquor is improved; the dialdehyde carboxymethyl cellulose is protonated in a strong acid medium with pH=1-2 to generate positive charges, so that the dialdehyde carboxymethyl cellulose generates electrostatic repulsion with Cu, zn and other light metals in a cationic state, and the dialdehyde carboxymethyl cellulose is reacted with (PdCl) 4 ) 2− Electrostatic attraction is generated, and palladium is separated and extracted. In the process, the crosslinking ratio of two substances needs to be controlled, because when the dialdehyde carboxymethyl cellulose is too low, the crosslinking density is reduced, and the stability is reduced; while too high, free amino sites on chitosan are lowered, thereby affecting adsorption efficiency or adsorption amount.
(4) Gold is leached by aqua regia, the purity of the gold is increased after the aqua regia is immersed because Cu and Zn are removed in the hydrochloric acid leaching process, and of course, a small part of light metal residues are left due to centrifugal immersion during hydrochloric acid immersing and filtering, so that the gold is recovered at the pH value of 3-5. With increasing pH, hydroxyamino and other protonated species are available to AuCl 4− Form electrostatic attraction, but due to Cl − With AuCl 4− The competitive adsorption of the chitosan-cellulose composite reduces the adsorption of gold, so that the chitosan-cellulose composite is firstly subjected to radiation epoxidation, and then the L-cysteine is grafted through a ring-opening reaction, so that the modified chitosan-cellulose composite is obtained. The S, N atom in the L-cysteine is easy to form a lone electron and is extremely easy to form decoction with gold ions, so that the recovery rate and recovery rate of gold are increased, and gold is selectively recovered.
Compared with the prior art, the invention has the following beneficial effects: (1) Grinding and co-milling a potassium persulfate-sodium chloride mixture and metal powder to increase the leaching rate and recovery rate of palladium and platinum; (2) Extracting 3 noble metals by adopting a continuous-grading extraction process: preferentially precipitating platinum with 2-ethylhexyl amine, separating platinum from palladium, and increasing the purity of the recovered palladium; selectively recycling palladium by using chitosan-cellulose compound, shielding impurity metals and improving palladium purity; high purity gold is recovered rapidly and selectively with modified chitosan-cellulose complexes.
Detailed Description
The following description of the technical solutions in the embodiments of the present invention will be clear and complete, and it is obvious that the described embodiments are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Example 1:
s1: pretreatment: crushing and sieving the electronic waste, and sieving by a high-voltage electrostatic separator and a magnetic separator in sequence to obtain metal powder;
s2: grinding and milling: milling the metal powder and the potassium persulfate-sodium chloride mixture together, setting the milling speed to be 550rpm, and milling for 1 hour to obtain a metal concentrate;
s3: acid leaching with hydrochloric acid: immersing the metal enrichment in hydrochloric acid solution with pH=1.5, and setting the solid-to-liquid ratio to be 1:8; the dipping temperature is 30 ℃; the dipping time is 2 hours, and the metal liquid A and filter residues are obtained by filtering;
s4: recovery of platinum: adding 2-ethylhexyl amine into the molten metal A, mixing and stirring, setting the stirring speed to be 300rmp, stirring for 40 minutes, and centrifugally separating to obtain a molten metal B and a platinum precipitate;
s5: recovery of palladium: (1) preparation method of chitosan-cellulose complex: dissolving chitosan in 2% acetic acid solution to obtain solution A; dissolving dialdehyde carboxymethyl cellulose in deionized water to form 10g/L solution B; mixing the solution A and the solution B, setting the temperature to be 50 ℃ for reaction for 5.5 hours, adding acetone for precipitation, filtering, washing and drying to obtain a chitosan-cellulose compound; (2) Adding the chitosan-cellulose composite into the molten metal B, mixing and stirring, wherein the stirring speed is set to be 200rpm, and the stirring temperature is set to be 20 ℃; stirring for 4 hours, and filtering to obtain palladium precipitate;
s6: acid leaching with aqua regia: soaking the filter residue in the step S3 in aqua regia, and setting the solid-liquid ratio to be 1:1.5; the dipping temperature is 75 ℃; the dipping time is 2 hours, and the metal liquid C is obtained through filtration;
s7: recovery of gold: (1) The preparation method of the modified chitosan-cellulose composite comprises the following steps: placing the chitosan-cellulose composite in a sealed bag, purging with nitrogen for 4 minutes, and irradiating the sample with grafting measurement of 6kGy by using a 1MeV electron accelerator; adding glycidyl methacrylate and a surfactant into a sealing belt, setting the temperature to be 50 ℃ and reacting for 2 hours in a water bath, washing and filtering to obtain an epoxidation compound; adding the modified chitosan-cellulose composite into DMF solution of L-cysteine, setting the temperature to 80 ℃ for reaction for 24 hours, and carrying out low-temperature vacuum drying to obtain the modified chitosan-cellulose composite; (2) Adding the modified chitosan-cellulose composite into the molten metal C, mixing and stirring, wherein the stirring speed is set to be 300rpm, and the stirring temperature is set to be 19 ℃; stirring for 4 hours, and filtering to obtain gold precipitate;
s8: and (3) reduction: placing the platinum precipitate into 1.1mol/L perchloric acid solution for eluting, enriching and reducing to obtain a platinum simple substance; and respectively eluting the palladium precipitate and the gold precipitate in 0.3mol/L thiourea solution, and enriching and reducing to obtain elemental palladium and elemental gold.
According to the technical scheme, the mass ratio of the metal powder to the potassium persulfate-sodium chloride mixture is 1:2; the mass ratio of the potassium persulfate-sodium chloride mixture is 2:1; the addition amount of the 2-ethylhexyl amine is 0.8g/L; the addition amount of the chitosan-cellulose composite is 8g/L; the addition amount of the modified chitosan-cellulose composite is 10g/L; the cross-linking ratio of the chitosan to the dialdehyde carboxymethyl cellulose is 1:1.
Example 2:
s1: pretreatment: crushing and sieving the electronic waste, and sieving by a high-voltage electrostatic separator and a magnetic separator in sequence to obtain metal powder;
s2: grinding and milling: milling the metal powder and the potassium persulfate-sodium chloride mixture together, setting the milling speed to be 500rpm, and milling for 0.5 hour to obtain a metal concentrate;
s3: acid leaching with hydrochloric acid: immersing the metal enrichment in hydrochloric acid solution with pH=1, and setting the solid-to-liquid ratio to be 1:5; the dipping temperature is 25 ℃; the dipping time is 1 hour, and the metal liquid A and filter residues are obtained by filtering;
s4: recovery of platinum: adding 2-ethylhexyl amine into the molten metal A, mixing and stirring, setting the stirring speed to be 250rmp, stirring for 30 minutes, and centrifugally separating to obtain a molten metal B and a platinum precipitate;
s5: recovery of palladium: (1) preparation method of chitosan-cellulose complex: dissolving chitosan in 1% acetic acid solution to obtain solution A; dissolving dialdehyde carboxymethyl cellulose in deionized water to form 8g/L solution B; mixing the solution A and the solution B, setting the temperature to be 45 ℃ for reaction for 5 hours, adding acetone for precipitation, filtering, washing and drying to obtain a chitosan-cellulose compound; (2) Adding the chitosan-cellulose composite into the molten metal B, mixing and stirring, wherein the stirring speed is set to be 150rpm, and the stirring temperature is set to be 18 ℃; stirring for 3 hours, and filtering to obtain palladium precipitate;
s6: acid leaching with aqua regia: soaking the filter residue in the step S3 in aqua regia, and setting the solid-liquid ratio to be 1:1; the dipping temperature is 70 ℃; the dipping time is 1 hour, and the metal liquid C is obtained by filtering;
s7: recovery of gold: (1) The preparation method of the modified chitosan-cellulose composite comprises the following steps: placing the chitosan-cellulose composite in a sealed bag, purging with nitrogen for 3 minutes, and irradiating the sample with grafting measurement of 2kGy by using a 1MeV electron accelerator; adding glycidyl methacrylate and a surfactant into a sealing belt, setting the temperature to be 50 ℃ and reacting for 2 hours in a water bath, washing and filtering to obtain an epoxidation compound; adding the modified chitosan-cellulose composite into DMF solution of L-cysteine, setting the temperature to be 70 ℃ for reaction for 20 hours, and carrying out low-temperature vacuum drying to obtain the modified chitosan-cellulose composite; (2) Adding the modified chitosan-cellulose composite into the molten metal C, mixing and stirring, wherein the stirring speed is set to be 250rpm, and the stirring temperature is set to be 18 ℃; stirring for 3 hours, and filtering to obtain gold precipitate;
s8: and (3) reduction: placing the platinum precipitate into 1mol/L perchloric acid solution for eluting, enriching and reducing to obtain a platinum simple substance; and respectively eluting the palladium precipitate and the gold precipitate in 0.25mol/L thiourea solution, and enriching and reducing to obtain elemental palladium and elemental gold.
According to the technical scheme, the mass ratio of the metal powder to the potassium persulfate-sodium chloride mixture is 1:1; the mass ratio of the potassium persulfate-sodium chloride mixture is 1:1; the addition amount of the 2-ethylhexyl amine is 0.7g/L; the addition amount of the chitosan-cellulose composite is 7g/L; the addition amount of the modified chitosan-cellulose compound is 8g/L; the cross-linking ratio of the chitosan to the dialdehyde carboxymethyl cellulose is 1:0.8.
Example 3:
s1: pretreatment: crushing and sieving the electronic waste, and sieving by a high-voltage electrostatic separator and a magnetic separator in sequence to obtain metal powder;
s2: grinding and milling: milling the metal powder and the potassium persulfate-sodium chloride mixture together, setting the milling speed to be 600rpm, and milling for 2 hours to obtain a metal concentrate;
s3: acid leaching with hydrochloric acid: immersing the metal enrichment in hydrochloric acid solution with pH=2, and setting the solid-to-liquid ratio to be 1:10; the dipping temperature is 40 ℃; the dipping time is 3 hours, and the metal liquid A and filter residues are obtained by filtering;
s4: recovery of platinum: adding 2-ethylhexyl amine into the molten metal A, mixing and stirring, setting the stirring speed to be 320rmp, stirring for 60 minutes, and centrifugally separating to obtain molten metal B and a platinum precipitate;
s5: recovery of palladium: (1) preparation method of chitosan-cellulose complex: dissolving chitosan in 4% acetic acid solution to obtain solution A; dissolving dialdehyde carboxymethyl cellulose in deionized water to form a solution B with the concentration of 12 g/L; mixing the solution A and the solution B, setting the temperature to 55 ℃ for reaction for 6 hours, adding acetone for precipitation, filtering, washing and drying to obtain a chitosan-cellulose compound; (2) Adding the chitosan-cellulose composite into the molten metal B, mixing and stirring, wherein the stirring speed is 220rpm, and the stirring temperature is 25 ℃; stirring for 5 hours, and filtering to obtain palladium precipitate;
s6: acid leaching with aqua regia: soaking the filter residue in the step S3 in aqua regia, and setting the solid-liquid ratio to be 1:2; the dipping temperature is 80 ℃; the dipping time is 1-3 hours, and the metal liquid C is obtained through filtration;
s7: recovery of gold: (1) The preparation method of the modified chitosan-cellulose composite comprises the following steps: placing the chitosan-cellulose composite in a sealed bag, purging with nitrogen for 5 minutes, and irradiating the sample with grafting measurement of 8kGy by using a 1MeV electron accelerator; adding glycidyl methacrylate and a surfactant into a sealing belt, setting the temperature to be 50 ℃ and reacting for 2 hours in a water bath, washing and filtering to obtain an epoxidation compound; adding the modified chitosan-cellulose composite into DMF solution of L-cysteine, setting the temperature to 90 ℃ for reaction for 28 hours, and carrying out low-temperature vacuum drying to obtain the modified chitosan-cellulose composite; (2) Adding the modified chitosan-cellulose composite into the molten metal C, mixing and stirring, wherein the stirring speed is set to 320rpm, and the stirring temperature is 18-20 ℃; stirring for 5 hours, and filtering to obtain gold precipitate;
s8: and (3) reduction: placing the platinum precipitate into 1.2mol/L perchloric acid solution for eluting, enriching and reducing to obtain a platinum simple substance; and respectively eluting the palladium precipitate and the gold precipitate in 0.5mol/L thiourea solution, and enriching and reducing to obtain elemental palladium and elemental gold.
According to the technical scheme, the mass ratio of the metal powder to the potassium persulfate-sodium chloride mixture is 1:3; the mass ratio of the potassium persulfate-sodium chloride mixture is 3:1; the addition amount of the 2-ethylhexyl amine is 0.8g/L; the addition amount of the chitosan-cellulose composite is 8g/L; the addition amount of the modified chitosan-cellulose composite is 10g/L; the cross-linking ratio of the chitosan to the dialdehyde carboxymethyl cellulose is 1:1.
Example 4: the grinding co-milling process was subtracted, and the rest was the same as in example 1;
example 5: the mass ratio of the potassium persulfate-sodium chloride mixture was 1:0.5, and the rest was the same as in example 1;
example 6: setting the crosslinking ratio of chitosan and dialdehyde carboxymethyl cellulose to be 1:2 in the step S5, and the rest is the same as in the example 1;
example 7: the modified chitosan-cellulose composite in step S7 was not modified, and the chitosan-cellulose composite was directly used instead, and the rest was the same as in example 1;
experiment: crushing electronic waste into powder smaller than 2mm, and then performing the separation and extraction process in the embodiment 1-2; and the recovery rate and the metal purity of the noble metal are detected, and the obtained results are shown in the following table:
Figure DEST_PATH_IMAGE002
conclusion: from the results of examples 1 to 3, it can be seen that: the process successfully separates three metals of platinum, palladium and gold from electronic wastes, and the purity of the metals is higher. However, it can be seen that Pt recovery has a large gap, because: in the grinding co-milling process, the mixing ratio of two substances in the potassium persulfate-sodium chloride mixture is different, and the Pt recovery rate and the ratio are in a proportional relation, so that the purity of the recovered Au can be influenced, and the purity of the recovered Au can be influenced due to the fact that the rest Pt is leached when the subsequent aqua regia is leached. This can be seen from the data of example 5. However, when the ratio is not less than 1:1, there is no great influence on Pd recovery, and when it is less than 1:0.5, palladium leaching is affected.
Comparing example 4 with example 1, it can be found that: the subtraction of the milling co-milling step has a greater impact on the leaching rates of platinum and palladium. The reason is that: potassium persulfate in the mixture of potassium persulfate and sodium chloride is used as an oxidant, and sodium chloride is used as a ligand; in the grinding and co-milling process of potassium persulfate and palladium and platinum, crystal grains are refined, crystal lattice defects are generated, the diffusion of the mixture and metal powder is increased, so that the potassium persulfate is converted into sulfate to play a role in oxidization, and then stable chelate is formed with halogen, so that the potassium persulfate is more easily dissolved and separated out in hydrochloric acid, and the leaching rate is increased. The leaching is incomplete in the hydrochloric acid leaching process, so that the rest part is leached in the aqua regia leaching process, and the recovery of gold is influenced.
Comparing example 6 with example 1, it can be found that: pd recovery was reduced because: when the cross-linking ratio of the cross-linked dialdehyde carboxymethyl cellulose is too high, free amino sites on chitosan are reduced, thereby affecting adsorption efficiency or adsorption amount. Comparing example 7 with example 1, it can be found that: the recovery rate and purity of gold are reduced because: but due to Cl − With AuCl 4− The competitive adsorption of (C) reduces the adsorption of gold, but is prone to forming a lone electron due to S, N atoms in L-cysteineThe electrons are extremely easy to form boiling with gold ions, so that the gold recovery rate is increased, and the gold is selectively recovered.
Finally, it should be noted that: the foregoing description is only a preferred embodiment of the present invention, and the present invention is not limited thereto, but it is to be understood that modifications and equivalents of some of the technical features described in the foregoing embodiments may be made by those skilled in the art, although the present invention has been described in detail with reference to the foregoing embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (7)

1. A separation and extraction process of rare noble metals in electronic waste is characterized in that: the method comprises the following steps:
s1: pretreatment: crushing and sieving the electronic waste, and sieving by a high-voltage electrostatic separator and a magnetic separator in sequence to obtain metal powder;
s2: grinding and milling: grinding and co-milling the metal powder and the potassium persulfate-sodium chloride mixture to obtain a metal concentrate;
s3: acid leaching with hydrochloric acid: immersing the metal enrichment in hydrochloric acid solution, immersing, and filtering to obtain metal liquid A and filter residues;
s4: recovery of platinum: adding 2-ethylhexyl amine into the metal liquid A, mixing and stirring, and centrifugally separating to obtain metal liquid B and platinum precipitate;
s5: recovery of palladium: adding the chitosan-cellulose compound into the metal liquid B, mixing and stirring, and filtering to obtain a palladium precipitate;
s6: acid leaching with aqua regia: placing the filter residue in the step S3 into aqua regia, soaking and filtering to obtain a metal liquid C;
s7: recovery of gold: adding the modified chitosan-cellulose compound into the metal liquid C, mixing and stirring, and filtering to obtain a gold precipitate;
s8: and (3) reduction: placing the platinum precipitate into perchloric acid solution for eluting, enriching and reducing to obtain a platinum simple substance; respectively eluting the palladium precipitate and the gold precipitate in thiourea solution, and enriching and reducing to obtain elemental palladium and elemental gold;
in the step S2, the mass ratio of the metal powder to the potassium persulfate-sodium chloride mixture is (1:1) - (1:3); the mass ratio of the potassium persulfate-sodium chloride mixture is (1:1) - (3:1); the grinding rate of the grinding co-milling is 500-600 rpm, and the grinding time is 0.5-2 hours;
the preparation method of the modified chitosan-cellulose composite comprises the following steps: placing the chitosan-cellulose composite in a sealed bag, purging with nitrogen for 3-5 minutes, and irradiating the sample with grafting measurement of 2-8 kGy by adopting an electron accelerator of 1 MeV; adding glycidyl methacrylate and a surfactant into a sealing belt, setting the temperature to be 50 ℃ and reacting for 2 hours in a water bath, washing and filtering to obtain an epoxidation compound; adding the modified chitosan-cellulose composite into DMF solution of L-cysteine, setting the temperature to be 70-90 ℃ for reaction for 20-28 hours, and carrying out low-temperature vacuum drying to obtain the modified chitosan-cellulose composite;
the preparation method of the chitosan-cellulose composite comprises the following steps: dissolving chitosan in 1-4% acetic acid solution to obtain solution A; dissolving dialdehyde carboxymethyl cellulose in deionized water to form a solution B with the concentration of 8-12 g/L; mixing the solution A and the solution B, setting the temperature to be 45-55 ℃ for reaction for 5-6 hours, adding acetone for precipitation, filtering, washing and drying to obtain a chitosan-cellulose compound; the cross-linking ratio of the chitosan to the dialdehyde carboxymethyl cellulose is (1:0.5) - (1:1).
2. The process for separating and extracting rare noble metals from electronic waste according to claim 1, wherein the process comprises the following steps: in step S3, the pH of the hydrochloric acid solution=1 to 2; the solid-liquid ratio of the impregnation is (1:5) - (1:10); the dipping temperature is 25-40 ℃; the soaking time is 1-3 hours.
3. The process for separating and extracting rare noble metals from electronic waste according to claim 1, wherein the process comprises the following steps: in the step S4, the addition amount of the 2-ethylhexyl amine is 0.6-0.8 g/L; the stirring speed is 250-320 rmp, and the stirring time is 30-60 minutes.
4. The process for separating and extracting rare noble metals from electronic waste according to claim 1, wherein the process comprises the following steps: in the step S5, the adding amount of the chitosan-cellulose compound is 6-8 g/L; stirring speed is 150-220 rpm, and stirring temperature is 18-25 ℃; the stirring time is 3-5 hours.
5. The process for separating and extracting rare noble metals from electronic waste according to claim 1, wherein the process comprises the following steps: in the step S6, the solid-to-liquid ratio of the aqua regia acid leaching is (1:1) - (1:2); the dipping temperature is 70-80 ℃; the soaking time is 1-3 hours.
6. The process for separating and extracting rare noble metals from electronic waste according to claim 1, wherein the process comprises the following steps: in the step S7, the addition amount of the modified chitosan-cellulose compound is 6-10 g/L; the stirring speed is 250-320 rpm, and the stirring temperature is 18-20 ℃; the stirring time is 3-5 hours.
7. The process for separating and extracting rare noble metals from electronic waste according to claim 1, wherein the process comprises the following steps: in the step S8, the concentration of the perchloric acid is 1-1.2 mol/L; the concentration of the thiourea solution is 0.25-0.5 mol/L.
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