A method for recycling waste spark plugs

Abstract

The present invention discloses a method for recycling waste spark plugs, comprising the following steps: disassembling waste spark plugs to obtain a central electrode, side electrodes, and an electrodeless spark plug; ultrasonically cleaning and crushing the central electrode and side electrodes in sequence to obtain electrode powder; adding an inorganic salt and an oxidant to the electrode powder for calcination; leaching the calcined electrode powder with a leaching solution to obtain a leachate and a leaching residue; extracting the leachate with an oxime extractant to obtain a copper-loaded organic phase and a primary raffinate, and back-extracting the copper-loaded organic phase to obtain a copper concentrate; precipitating the primary raffinate with phosphate to obtain iron phosphate and a supernatant; extracting the supernatant with a neutral phosphorus extractant to obtain a platinum-loaded organic phase and a secondary raffinate, and back-extracting the platinum-loaded organic phase to obtain a platinum concentrate; extracting the secondary raffinate with an acidic phosphoric acid extractant to obtain a nickel-loaded organic phase, and back-extracting the nickel-loaded organic phase to obtain a nickel concentrate. The present invention is applicable to the recovery of both precious metal-containing spark plugs and copper-nickel electrode spark plugs.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal recovery, and in particular relates to a method for recycling waste spark plugs. Background Art

[0002] Spark plugs are the ignition tools used in gasoline-powered vehicles and are primarily categorized as automotive and motorcycle spark plugs. Spark plugs are classified by electrode material into three types: nickel alloy, silver alloy, and platinum alloy. Ordinary copper-core spark plugs have a service life of 30,000 kilometers, while precious metal spark plugs (platinum and iridium) have a service life of 60,000 to 90,000 kilometers. Spark plugs must be replaced after exceeding their mileage. With the increasing number of gasoline-powered vehicles in my country, the number of scrapped spark plugs has increased dramatically. Spark plugs primarily consist of an outer gasket, inner sealing ring, insulator, terminal screw, center electrode, side electrode, and metal housing. These components contain metals such as alumina, stainless steel, copper, nickel, gold, platinum, and iridium, making them highly recyclable.

[0003] The existing spark plug recycling methods mainly include the following methods:

[0004] 1) CN201210519892.7 reports a refurbishment process involving cleaning, stripping, and electroplating old spark plugs. While the resulting appearance is indistinguishable from new, its ignition performance remains unchanged. Refurbished spark plugs could potentially be resold as new, disrupting the spark plug recycling market.

[0005] 2) CN101282024A discloses a process for refurbishing old spark plugs. This involves gradually separating the components of a used spark plug by removing the sealing ring, heating and flattening the expansion band, and then heating the screw and insulator. The electrodes are then repaired by removing the ablated portion, stretching it, and adjusting the electrode gap. Finally, each component of the spark plug is reassembled to complete the refurbishment. However, whether the performance of spark plugs refurbished in this way is comparable to that of new ones remains debatable. Furthermore, the applicant states that spark plugs can be refurbished a maximum of two times, which implies that they will inevitably become obsolete after use.

[0006] 3) CN112210671A discloses a precious metal recovery device for waste spark plugs. This device can separate the precious metal electrode and metal shell of the spark plug through a platinum recovery device, but there is no subsequent treatment for the separated components. It can only serve as a primary separation device.

[0007] 4) CN202110832888.5 discloses a process for recovering precious metals from spark plugs, which recovers Pt and Ir from spark plugs through pickling, silver smelting, acid melting, and hydrazine hydrate reduction. This recovery process is not only lengthy and reagent-intensive, but also produces a large amount of acidic waste liquid containing copper, nickel, and iron. Furthermore, this technology only recovers precious metals, and lacks specific recovery measures for the mainstream copper-nickel spark plugs on the market.

[0008] In summary, the existing technology for recycling used spark plugs still needs to be improved, and there is an urgent need to develop a spark plug recycling technology with high resource utilization, wide adaptability and clean process. Summary of the Invention

[0009] In view of the above shortcomings of the existing technology, the purpose of the present invention is to provide a method for recycling waste spark plugs. By co-smelting the central electrode and the side electrode and extracting them in sequence, the copper, iron, nickel and other metals in the waste spark plugs can be recovered while enriching precious metals such as platinum and iridium.

[0010] To achieve the above object, the present invention is implemented through the following technical solutions:

[0011] A method for recycling waste spark plugs comprises the following steps:

[0012] (1) Disassemble the waste spark plug to obtain the central electrode, side electrode and electrodeless spark plug;

[0013] (2) ultrasonically cleaning the central electrode and the side electrodes, and then crushing the ultrasonically cleaned central electrode and the side electrodes to obtain electrode powder;

[0014] (3) adding an inorganic salt and an oxidant to the electrode powder and then performing a calcination treatment;

[0015] (4) using a leaching solution to leach the calcined electrode powder to obtain a leaching solution and a leaching residue;

[0016] (5) extracting the leachate with an oxime extractant to obtain a copper-loaded organic phase and a primary raffinate, and then back-extracting the copper-loaded organic phase to obtain a copper concentrate;

[0017] (6) using phosphate to precipitate the primary raffinate to obtain an iron phosphate precipitate and a supernatant;

[0018] (7) extracting the supernatant with a neutral phosphorus extractant to obtain a platinum-loaded organic phase and a secondary raffinate, and then back-extracting the platinum-loaded organic phase to obtain a platinum concentrate;

[0019] (8) extracting the secondary raffinate with an acidic phosphoric acid extractant to obtain a nickel-loaded organic phase, and then back-extracting the nickel-loaded organic phase to obtain a nickel concentrate.

[0020] Furthermore, the washing liquid for ultrasonic cleaning in step (2) comprises an organic solvent and water; and the particle size of the electrode powder obtained by the crushing process is less than 75 μm.

[0021] Furthermore, in step (3), the inorganic salt includes one or more of sodium chloride, ammonium chloride, calcium chloride, ammonium sulfate, potassium sulfate, potassium bisulfate, ammonium nitrate, calcium nitrate, and sodium nitrate, and the amount of the inorganic salt is 1 to 25 times the mass of the electrode powder; the oxidant includes one or more of sodium hypochlorite, sodium percarbonate, sodium perborate, and potassium perborate; and the amount of the oxidant is 0.5 to 10 times the mass of the electrode powder.

[0022] Furthermore, the leaching solution in step (4) is hydrochloric acid with a concentration of 0 to 3 mol / L; the liquid-solid ratio of the leaching solution to the calcined electrode powder is 3:1 to 30:1, the leaching temperature is 20 to 100° C., and the leaching time is 10 to 300 min.

[0023] Furthermore, in step (5), the leachate is extracted with a mixture of an oxime extractant and a diluent; and the copper-loaded organic phase is back-extracted with a sulfuric acid solution, wherein the concentration of the sulfuric acid solution is 80 to 500 g / L.

[0024] Furthermore, in step (6), the concentration of phosphate is 0.001-2 mol / L, the feeding rate is 1-10 mL / min, and the end point of the precipitation reaction is controlled at pH 1.5-5.

[0025] Furthermore, in step (7), the supernatant is extracted with a mixture of a neutral phosphorus extractant, a diluent and a modifier, wherein the content of the neutral phosphorus extractant is 30-50 wt%, the content of the diluent is 0-20 wt%, and the content of the modifier is 20-50 wt%; and the platinum-loaded organic phase is back-extracted with a sodium hydroxide solution having a concentration of 0.1-2.5 mol / L.

[0026] Furthermore, before extracting the supernatant in step (7), hydrochloric acid is added to the supernatant to adjust the concentration of hydrochloric acid in the supernatant to 0.1-6 mol / L; after obtaining the platinum concentrate, hydrazine hydrate is used for reduction to obtain sponge platinum.

[0027] Furthermore, in step (8), the secondary raffinate is extracted with a mixture of an acidic phosphoric acid extractant, a diluent and a modifier, wherein the content of the acidic phosphoric acid extractant is 30-50 wt%, the content of the diluent is 50-60 wt%, and the content of the modifier is 0-10 wt%.

[0028] Furthermore, before extracting the secondary raffinate in step (8), the step further includes saponifying the acidic phosphoric acid extractant; and back-extracting the nickel-loaded organic phase using a sulfuric acid solution with a concentration of 90 to 300 g / L.

[0029] Furthermore, the waste spark plug resource recovery method provided by the present invention further includes obtaining iridium powder from the leached slag obtained in the washing step (4); and crushing, screening, and magnetically separating the electrodeless spark plugs in step (1) to obtain scrap steel and ceramic powder.

[0030] The beneficial effects of the present invention are:

[0031] 1) The present invention provides a method for recycling waste spark plugs. First, the waste spark plugs are disassembled. The separated central and side electrodes are smelted together to convert metals other than Ir (Cu, Fe, Ni, etc.) into corresponding salts. Iridium is then obtained after acid leaching. The leachate is then sequentially extracted using an oxime extractant to extract copper, a phosphate precipitate to extract iron, a neutral phosphorus extractant to extract platinum, and an acidic phosphoric acid extractant to extract nickel. This achieves the recovery of copper, iron, and nickel from waste circuit boards while enriching the precious metals platinum and iridium in the spent three-way catalyst. This method is applicable not only to the recovery of spark plugs containing precious metals, but also to the recovery of conventional copper-nickel electrode spark plugs.

[0032] 2) The method provided by the present invention generates less acid and alkali waste liquid during the recycling process, has a high degree of resource utilization for spark plugs, and the purity and added value of the recycled raw materials are relatively high. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings of the embodiments are briefly introduced below.

[0034] Figure 1 This is a flow chart of a waste spark plug resource recovery method according to the present invention. DETAILED DESCRIPTION

[0035] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0036] See also Figure 1 The waste spark plug resource recovery method provided by the present invention comprises the following steps:

[0037] (1) Dismantling the waste spark plugs mechanically and manually to obtain the central electrode, side electrode, and electrodeless spark plugs; the manual dismantling equipment is a grinding wheel cutter;

[0038] (2) Using an organic solvent (including but not limited to one or more of ethanol, DMF, DMSO, and acetone) and water as a washing liquid, the central electrode and the side electrodes are ultrasonically cleaned, and the liquid-to-solid ratio of the washing is 1:1 to 20:1, and the preferred liquid-to-solid ratio is 3:1 to 5:1; the ultrasonic frequency of the washing is 20 to 120 kHz, and preferably 28 to 68 kHz; the ultrasonic time is 1 to 30 minutes, and preferably 3 to 5 minutes; then, using common industrial fine crushing equipment, such as a jaw crusher, a cone crusher, or a ball mill, the central electrode and the side electrodes after ultrasonic cleaning are crushed to obtain electrode powder with a particle size of less than 75 μm, and preferably less than 37.4 μm.

[0039] (3) Adding inorganic salts and oxidants to the electrode powder for roasting treatment; the inorganic salts include one or more of sodium chloride, ammonium chloride, calcium chloride, ammonium sulfate, potassium sulfate, potassium hydrogen sulfate, ammonium nitrate, calcium nitrate, and sodium nitrate, and the amount of the inorganic salt is 1 to 25 times the mass of the electrode powder, preferably 3 to 10 times; the oxidant includes one or more of sodium hypochlorite, sodium percarbonate, sodium perborate, and potassium perborate, and the amount of the oxidant is 0.5 to 10 times the mass of the electrode powder, preferably 1 to 5 times. The metals (Cu, Fe, Ni) other than Ir are converted into corresponding sulfates, chlorides, or nitrates by inorganic salt oxidation roasting to facilitate subsequent acid leaching extraction. The roasting atmosphere includes at least one of air, oxygen, ozone, and chlorine. The roasting temperature is 200 to 1300°C, preferably 300 to 850°C; the roasting time is 30 to 600 minutes, preferably 60 to 300 minutes.

[0040] (4) using hydrochloric acid as a leaching solution to leach the calcined electrode powder to obtain a leachate and a leaching residue; wherein the concentration of the hydrochloric acid is 0.05 to 3 mol / L, preferably 0.05 to 0.1 mol / L; the liquid-solid ratio of the leaching is 3:1 to 30:1, preferably 5:1 to 10:1; the leaching time is 10 to 300 min, preferably 60 to 120 min; the leaching temperature is 20 to 100° C., preferably 50 to 60° C.; and the stirring speed during the leaching process is 300 to 1000 rpm, preferably 400 to 600 rpm.

[0041] (5) Extracting the leachate with an oxime extractant to obtain a copper-loaded organic phase and a primary raffinate. The oxime extractant is a commercial oxime extractant, including but not limited to 984H、Lix 984N、 One or more of 5640H, ACORGAM5640, AD 100, and N 902. Specifically, a container (separating funnel, centrifuge tube, plastic bottle) containing the organic phase and the aqueous phase is placed in an air (water) bath shaker for extraction reaction. The extraction phase ratio is 1:10 to 10:1, preferably 1:4 to 3:1; the extraction temperature is 10 to 50°C, preferably 20 to 40°C; the extraction shaker speed is 100 to 800 rpm, preferably 300 to 450 rpm; the extraction time is 1 to 30 minutes, preferably 3 to 5 minutes; and the number of extraction stages is 1 to 10, preferably 1 to 3. The pH of the solution after extraction equilibrium is then adjusted to 0.5 to 6, preferably 0.75 to 1.2, by adding acid or base.

[0042] Then, the copper-loaded organic phase is washed with dilute hydrochloric acid, dilute sulfuric acid or dilute nitric acid with a pH of 0 to 3, preferably 0 to 1.5; the washing phase ratio (volume ratio of organic phase to aqueous phase) is 1:10 to 10:1, preferably 3:1 to 5:1; the washing temperature is 10 to 50°C, preferably 20 to 40°C; the washing shaking speed is 100 to 800 rpm, preferably 300 to 450 rpm; the washing time is 1 to 60 min, preferably 5 to 10 min, and the washing stage is 1 to 10, preferably 1 to 3. Subsequently, the copper-loaded organic phase is stripped with a sulfuric acid solution with a concentration of 80 to 500 g / L, preferably 120 to 280 g / L, as a stripping agent to obtain high-purity copper sulfate. The stripping ratio is 1:10 to 10:1, preferably 1:1.5 to 1.5:1; the stripping oscillation speed is 100 to 800 rpm, preferably 300 to 450 rpm; the stripping temperature is 10 to 100° C., preferably 20 to 40° C.; the stripping time is 1 to 120 min, preferably 5 to 15 min; the stripping stage is 1 to 5, preferably 1 to 3.

[0043] (6) Utilize the primary raffinate obtained in the phosphate precipitation step (5) including but not limited to sodium phosphate, potassium phosphate or ammonium phosphate. The phosphate is used in the form of a solution, and the feeding method is positive addition; preferably, a sodium phosphate solution with a concentration of 0.001 to 2 mol / L, preferably 0.05 to 1.5 mol / L, is used, and the feeding rate is 1 to 10 mL / min, preferably 2 to 5 mL / min. The rotation speed for the precipitation reaction is 300 to 480 rpm, preferably 400 to 480 rpm; the end point of the precipitation reaction is controlled at a pH of 1.5 to 5, preferably 2.7 to 3.2; after the precipitation reaction is completed, the solution is kept warm and aged to obtain an iron phosphate precipitate and a supernatant. The reaction temperature, the holding temperature after stopping the feeding, and the aging temperature of the above-mentioned precipitation reaction are 20 to 100°C, wherein the reaction temperature and the holding temperature after stopping the feeding are preferably 50 to 80°C. Furthermore, the heat preservation time is 3 to 10 hours, preferably 4 to 6 hours; the aging time is 6 to 20 hours, preferably 8 to 12 hours.

[0044] (7) The supernatant is extracted with a neutral phosphorus extractant to obtain a platinum-loaded organic phase and a secondary raffinate.

[0045] The extraction of Pt by neutral phosphorus extractants needs to be carried out under acidic conditions, and the extraction equation is as follows:

[0046]

[0047] Adjusting the aqueous phase to acidic is beneficial for the extraction reaction to proceed in the forward direction. Therefore, before extraction, hydrochloric acid is added to the supernatant obtained in step (6) to adjust the hydrochloric acid concentration in the supernatant to 0.1 to 6 mol / L, preferably 0.1 to 1 mol / L, and then extraction is performed. The neutral phosphorus extractant is at least one of TOPO, TRPO, and C923. The phase ratio during extraction is 1:1 to 1:20, preferably 1:5 to 1:15; the extraction stirring speed is 300 to 600 rpm, preferably 300 to 450 rpm; the extraction time is 1 to 120 min, preferably 1 to 15 min; and the number of extraction stages is 1 to 2.

[0048] After the extraction is completed, the platinum-loaded organic phase is washed with a hydrochloric acid aqueous solution with an acidity of 1 to 2; the washing phase ratio is 10:1 to 5:1, the number of washing stages is 1 to 2, the washing time is 1 to 3 minutes, the washing temperature is room temperature, and the washing stirring speed is 300 to 450 rpm. The washed platinum-loaded organic phase is then stripped using a NaOH solution with a concentration of 0.1 to 2.5 mol / L as a stripping agent, the stripping phase ratio is 10:1 to 5:1, the stripping temperature is 25 to 40 minutes, the stripping time is 10 to 30 minutes, the stripping stirring speed is 450 to 500 rpm, and the number of stripping stages is 1 to 2, to obtain a platinum stripping solution.

[0049] Adding 10-80 wt% hydrazine hydrate to the platinum strip solution for a reduction reaction to obtain sponge platinum. The amount of hydrazine hydrate used is 2-5 times the molar equivalent of Pt in the aqueous phase, the reduction time is 3-10 minutes, the reduction temperature is room temperature, and the reduction stirring speed is 200-300 rpm.

[0050] (8) extracting the secondary raffinate obtained in step (7) with an acidic phosphoric acid extractant to obtain a nickel-loaded organic phase.

[0051] The acidic phosphoric acid extractant of the present invention is preferably P204, whose molecular formula can be abbreviated as HA. It usually exists in the organic phase in the form of a dimer (HA)2. The hydrogen bond dimer of P204 can be broken by saponification with an alkali. The saponification reaction is as follows:

[0052] (HA) 2(org) +OH - (aq) →A- (org) +HA (org) +H2O

[0053] In addition, the nickel extraction reaction of P204 is an acid-releasing process:

[0054]

[0055] Saponification can also neutralize H in HA in advance + , reducing the acidity change of the aqueous phase during the extraction process and making the reaction proceed in the forward direction. Therefore, the present invention first uses a saponification base such as sodium hydroxide, potassium hydroxide, ammonia water or calcium hydroxide and an acidic phosphoric acid extractant to carry out a saponification reaction. The saponification base is added in a manner including directly adding a solid or adding an alkali solution; the saponification degree is 10% to 80%, preferably 30% to 60%; and the pH value of the secondary raffinate obtained in step (7) is adjusted to 0.5 to 7, preferably 3 to 7 using an alkali solution or concentrated ammonia water; and then extraction is carried out. The ratio used in the extraction is 1:10 to 10:1, preferably 1:3 to 3:1; the extraction temperature is 10 to 80°C, preferably 20 to 40°C; the extraction time is 5 to 30 minutes, preferably 10 to 30 minutes; the extraction shaking speed is 100 to 800 rpm, preferably 300 to 450 rpm.

[0056] After extraction, the nickel-loaded organic phase is stripped using a 90-300 g / L sulfuric acid solution as a stripping agent to obtain nickel sulfate, which is used to prepare a high-nickel ternary precursor or nickel sulfate crystals. The stripping ratio is 2:1-6:1, the stripping temperature is 25-40 minutes, the stripping time is 10-30 minutes, and the stripping stirring speed is 450-500 rpm.

[0057] (9) The leached residue obtained in step (4) is washed with pure water to obtain iridium powder.

[0058] (10) Using a jaw crusher or a double-roll crusher, a common crushing equipment in the industry, the electrodeless spark plug in step (1) is crushed to a particle size of less than 5 mm. The material that does not meet the particle size requirement is returned to the device for further crushing. The crushed material is then subjected to vibration separation and magnetic separation in turn to obtain scrap steel and ceramic powder.

[0059] In the present invention, since the extractant used has a high viscosity and high water solubility, phase separation is slow when used alone, and the phase separation entrainment loss is large. In addition, the loss of the extractant in the aqueous phase is large and it is easy to emulsify. The diluent can reduce the viscosity of the extractant, improve the phase separation ability, reduce the loss of the extractant in the extraction process, and reduce the time required for extraction equilibrium; the modifier can improve the solubility of the extractant in the organic phase and prevent the emulsification of the organic phase in the extraction process. Therefore, preferably, the present invention can also add a diluent or a modifier to the extractant during the extraction. For example, in step (5), a mixture of 10 to 30 wt% of an oxime extractant and 70 to 90 wt% of a diluent is used to extract the leachate to obtain a copper-loaded organic phase and a primary raffinate. In step (7), the supernatant is extracted with a mixture of a neutral phosphorus extractant, a diluent and a modifier, wherein the content of the neutral phosphorus extractant is 30-50 wt%, the content of the diluent is 0-20 wt%, and the content of the modifier is 20-50 wt%. In step (8), the secondary raffinate is extracted with a mixture of an acidic phosphoric acid extractant, a diluent and a modifier, wherein the content of the acidic phosphoric acid extractant is 30-50 wt%, the content of the diluent is 50-60 wt%, and the content of the modifier is 0-10 wt%.

[0060] The diluent may be 260# sulfonated kerosene, and the modifier may be one or more of n-octanol, isooctyl alcohol, and TBP.

[0061] This invention combines extraction and stripping methods based on the properties of various metals, selecting appropriate extractants to recover the various components in spent spark plugs. This maximizes the value of the spent spark plugs while reducing recycling costs and reducing waste emissions. The following examples provide a detailed implementation process.

[0062] Example 1

[0063] A method for recycling waste spark plugs comprises the following steps:

[0064] (1) The central electrode and ground electrode of 258 kg of used spark plugs were manually cut off using an angle grinder to obtain 7.2 kg of central electrode and side electrode, and 250.8 kg of electrodeless spark plugs. The central electrode and side electrode were immersed in 30 L of 60 wt% alcohol and ultrasonically cleaned at 40 kHz for 5 minutes to obtain oil-free central electrode and side electrode. The oil-free central electrode and side electrode were first crushed using a jaw crusher for 30 minutes, then ball milled using a ball mill for 30 minutes, and then sieved using a 400 mesh standard test sieve to obtain electrode powder with a particle size of less than 75 μm.

[0065] (2) 600 g of electrode powder, 3000 g of ammonium chloride, and 1800 g of sodium percarbonate were mixed and placed in an atmosphere tube furnace and calcined at 350°C in an ozone atmosphere for 3 h. The calcined electrode powder was added to 3600 mL of 0.1 mol / L dilute hydrochloric acid and leached for 2 h at a stirring speed of 600 rpm and a leaching temperature of 60°C. The solid-liquid separation yielded a leachate and a leach residue. The concentrations of Fe, Cu, Ni, Pt, and Ir in the leachate were 48.69 g / L, 65.42 g / L, 60.09 g / L, 338 mg / L, and <0.02 mg / L, respectively, with corresponding leaching rates of ~100%, ~100%, ~100%, 99.9%, and ~0%, respectively. The leach residue was washed with pure water and dried to obtain 0.54 g of Ir powder, the purity of which was greater than 99% as measured by EDS.

[0066] (3) The leachate obtained in step (2) is first subjected to a three-stage extraction using 30wt% of an oxime extractant ACORGA M5640 + 70wt% of 260# sulfonated kerosene at a ratio of 2:1 to obtain a copper-loaded organic phase and a primary raffinate; the extraction time is 3min, the temperature is room temperature, and the shaking speed is 400rpm. The pH of the solution after the extraction equilibrium is adjusted to 1.06 by adding alkali solution. The copper-loaded organic phase is then washed in a single stage using dilute sulfuric acid with a pH of 1 at a ratio of 10:1, the washing time is 10min, the temperature is room temperature, and the shaking speed is 400rpm. Thereafter, a three-stage stripping is performed using sulfuric acid with a concentration of 180g / L at a ratio of 3:2, the stripping time is 10min, the temperature is room temperature, and the shaking speed is 400rpm to obtain a copper sulfate solution.

[0067] After testing, the extraction rates of Cu, Fe, Ni and Pt in the leachate were 99.9%, 0.31%, 0.02% and 0.14% respectively. After washing and stripping of the copper-loaded organic phase, the copper recovery rate was 98.6%, and the iron content in the stripping solution (copper sulfate solution) was less than 50 mg / L.

[0068] (4) The primary raffinate obtained in step (3) was added to a 20 L reactor, the temperature in the reactor was raised to 80° C. by hydrothermal heating, the stirring speed was adjusted to 480 rpm, and then 0.3 mol / L sodium phosphate solution was pumped in at a rate of 10 mL / min. When the pH of the reaction system reached 2.92, the feeding was stopped. After keeping the temperature at 80° C. for 4 h, the slurry was transferred to a water bucket and aged for 12 h. A filter cake and a supernatant were obtained by suction filtration. The filter cake was washed and dried to obtain an iron phosphate product, the main component of which was FePO4·2H2O (purity>99.5%), the impurity Ni content was 0.05%, the impurity copper content was 0.0001%, and the impurity Pt content was 0.00001%.

[0069] (5) The supernatant obtained after precipitation in step (4) was acidified with concentrated hydrochloric acid to a hydrochloric acid concentration of 1 mol / L, and then extracted with 30 wt% TOPO + 50 wt% TBP + 20 wt% 260# sulfonated kerosene at a ratio of 1:10 at a shaking speed of 350 rpm for 10 minutes to obtain a secondary raffinate and a Pt-loaded organic phase. Subsequently, the Pt-loaded organic phase was washed with dilute hydrochloric acid of pH = 1 at a ratio of 10:1 at a shaking speed of 350 rpm for 1 minute. Finally, the washed Pt-loaded organic phase was stripped with 2.5 mol / L sodium hydroxide solution at a shaking speed of 350 rpm at a ratio of 5:1 at room temperature for 30 minutes to obtain a platinum strip solution. After testing, the concentrations of Pt, Fe, and Ni in the strip solution were 5.87 g / L, 68 mg / L, and 3 mg / L, respectively, and the Pt recovery rate was >99%.

[0070] The platinum stripping solution was added to a beaker, stirred at 300 rpm, and then hydrazine hydrate (4.5 times the molar equivalent of Pt) was added using a constant pressure dropping funnel. Stirring was continued at room temperature for 10 minutes. The solution was filtered and washed using a sand core filter to obtain sponge platinum. Testing showed that the sponge platinum had a purity greater than 99.2%, and the Pt content in the stripping solution was less than 0.02 mg / L.

[0071] (6) solid sodium hydroxide is first added to 40 wt% P204+10 wt% isooctyl alcohol+50 wt% 260# sulfonated kerosene for saponification, and after determining the saponification degree by titration, alkali solution or concentrated hydrochloric acid is added to adjust the saponification degree to 60%. The pH value of the secondary raffinate in step (5) is adjusted to 5 using alkali solution or concentrated ammonia water; the saponified organic phase is then mixed with the secondary raffinate at a shaking speed of 400 rpm, and extracted at a ratio of 1:10 for 15 minutes at room temperature to obtain a nickel-loaded organic phase and a tertiary raffinate; the nickel-loaded organic phase is back-extracted at room temperature using 280 g / L H2SO4 solution at a ratio of 5:1 at a stirring speed of 450 rpm for 10 minutes to obtain a nickel sulfate solution.

[0072] After testing, the nickel content in the three extraction residues was 15 mg / L, the nickel ion concentration in the stripping solution (nickel sulfate solution) was 160.3 g / L, and the nickel recovery rate of the entire concentration process was >99.99%. The obtained nickel sulfate solution can be used to prepare high-nickel ternary precursors or nickel sulfate crystals.

[0073] (7) Using a jaw crusher, the electrodeless spark plug obtained by splitting in step (1) is crushed until a crushed material with a particle size of less than 5 mm is obtained. After vibration sorting, the crushed material is conveyed to a magnetic separation device via a conveyor belt for magnetic separation to achieve separation of ceramics and metals, thereby obtaining scrap steel and ceramic powder.

[0074] It should be noted that the above embodiments all belong to the same inventive concept, and the description of each embodiment has its own focus. For any details not described in individual embodiments, reference may be made to the description in other embodiments.

[0075] The above-described embodiments merely illustrate the implementation methods of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make various modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A method for recycling waste spark plugs, characterized in that: The following steps are involved: (1) Disassemble the used spark plugs to obtain the central electrode, side electrode and electrodeless spark plugs; (2) ultrasonically cleaning and crushing the central electrode and the side electrode in sequence to obtain electrode powder; (3) adding an inorganic salt and an oxidant to the electrode powder and performing a calcination treatment; (4) using a leaching solution to leach the calcined electrode powder to obtain a leaching solution and a leaching residue; (5) extracting the leachate with an oxime extractant to obtain a copper-loaded organic phase and a primary raffinate, and then back-extracting the copper-loaded organic phase to obtain a copper concentrate; (6) precipitating the primary raffinate with phosphate to obtain a ferric phosphate precipitate and a supernatant; (7) extracting the supernatant with a neutral phosphorus extractant to obtain a platinum-loaded organic phase and a secondary raffinate, and then back-extracting the platinum-loaded organic phase to obtain a platinum concentrate; (8) extracting the secondary raffinate with an acidic phosphoric acid extractant to obtain a nickel-loaded organic phase, and then back-extracting the nickel-loaded organic phase to obtain a nickel concentrate; The inorganic salt in step (3) includes one or more of sodium chloride, ammonium chloride, calcium chloride, ammonium sulfate, potassium sulfate, potassium bisulfate, ammonium nitrate, calcium nitrate, and sodium nitrate, and the amount of the inorganic salt is 1 to 25 times the mass of the electrode powder; the oxidant includes one or more of sodium hypochlorite, sodium percarbonate, sodium perborate, and potassium perborate; the amount of the oxidant is 0.5 to 10 times the mass of the electrode powder; The extracting solution in step (4) is hydrochloric acid with a concentration of 0 to 3 mol / L; the liquid-solid ratio of the extracting is 3:1 to 30:1, the extracting temperature is 20 to 100°C, and the extracting time is 10 to 300 min; The Ir concentration in the leachate in step (4) is < 0.02 mg / L; the leaching residue is washed with pure water and dried to obtain Ir powder, the purity of which is measured to be greater than 99%.

2. The method for recycling waste spark plugs according to claim 1, wherein: The washing liquid for ultrasonic cleaning in step (2) contains an organic solvent; and the particle size of the electrode powder obtained by the crushing process is less than 75 μm.

3. The method for recycling waste spark plugs according to claim 1, wherein: In step (5), the leachate is extracted with a mixture of an oxime extractant and a diluent; and the copper-loaded organic phase is back-extracted with a sulfuric acid solution, wherein the concentration of the sulfuric acid solution is 80 to 500 g / L.

4. The method for recycling waste spark plugs according to claim 1, wherein: The concentration of the phosphate in step (6) is 0.001-2 mol / L, the feeding rate is 1-10 mL / min, and the end point of the precipitation reaction is controlled at pH 1.5-5.

5. The method for recycling waste spark plugs according to claim 1, wherein: In step (7), the supernatant is extracted with a mixture of a neutral phosphorus extractant, a diluent and a modifier, wherein the content of the neutral phosphorus extractant in the mixture is 30 to 50 wt%, the content of the diluent is 0 to 20 wt%, and the content of the modifier is 20 to 50 wt%. The platinum-loaded organic phase is back-extracted with a sodium hydroxide solution having a concentration of 0.1 to 2.5 mol / L.

6. The method for recycling waste spark plugs according to claim 1, wherein: Step (7) further includes: adding hydrochloric acid to the supernatant to adjust the concentration of hydrochloric acid in the supernatant to 0.1-6 mol / L before extracting the supernatant; and reducing the platinum concentrate with hydrazine hydrate to obtain sponge platinum.

7. The method for recycling waste spark plugs according to claim 1, wherein: Before extracting the secondary raffinate in step (8), the step also includes saponifying the acidic phosphoric acid extractant; and back-extracting the nickel-loaded organic phase using a sulfuric acid solution with a concentration of 90 to 300 g / L.

8. The method for recycling waste spark plugs according to claim 1, characterized in that: The electrodeless spark plug in step (1) is crushed, screened, and magnetically separated to obtain scrap steel and ceramic powder.

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