Method for recovering sponge palladium from palladium-containing waste

Abstract

The invention relates to the technical field of rare and precious metal recovery, and discloses a method for recovering sponge palladium from palladium-containing waste. The method comprises the following steps: (1) in the presence of nano ozone bubbles, mixing the palladium-containing waste with hydrochloric acid to carry out oxidation leaching reaction to obtain palladium-containing leachate and leaching residues; the nanometer ozone bubbles are formed by treating ozone gas through a nanometer microbubble generator; (2) the palladium-containing leaching liquid is subjected to impurity removal treatment, and impurity-removed liquid is obtained; (3) introducing the impurity-removed liquid into palladium adsorption resin for adsorption treatment to obtain palladium-containing resin and exchange tail liquid; (4) introducing an eluent into the palladium-containing resin for desorption treatment to obtain a palladium desorption solution; and (5) mixing the palladium desorption solution with a reducing agent for reduction reaction to obtain sponge palladium. According to the method provided by the invention, the leaching efficiency of the palladium can be enhanced, the purity of the obtained sponge palladium is relatively high, and the method is simple to operate, energy-saving and environment-friendly.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of rare and precious metal recovery, and particularly relates to a method for recovering sponge palladium from palladium-containing waste. BACKGROUND

[0002] Palladium, as an important rare and precious metal, is widely used in various fields due to its excellent catalytic activity, electrical conductivity and corrosion resistance. Palladium concentrate, as the main raw material for extracting palladium, its traditional recovery process mainly includes chemical precipitation method, extraction method, resin adsorption method, etc.

[0003] In the existing palladium recovery process, the oxidation leaching link mainly depends on nitric acid, sodium chlorate, hydrochloric acid-hydrogen peroxide, aqua regia system, etc. For example, CN114350972A uses platinum-palladium concentrate chlorination leaching solution as raw material, which needs to be pretreated by oxalic acid to remove copper, TBP extraction to remove gold, etc. The process is long; CN115700286A uses waste Pd / Al2O3 catalyst as the object, and uses hydrochloric acid-nitric acid leaching, which has the risk of nitrogen oxide emission; CN117265280A uses aqua regia to dissolve palladium-containing filter core ash, which has strong corrosion and is easy to produce toxic gas; CN117551884A and CN119654427A use hydrochloric acid-hydrogen peroxide system for leaching, but the utilization rate of the oxidizing agent is low, and the leaching time is as long as 3-6h; CN119592803A needs to be combined with hydrogen reduction and dilute acid purification, which has high energy consumption and strict requirements for equipment sealing.

[0004] In addition, the use of the above-mentioned traditional oxidizing agent in the oxidation leaching link also has the problems of low oxidation efficiency, large consumption of oxidizing agent, easy production of toxic and harmful gas (such as chlorine, nitrogen oxide) or high-concentration acidic waste liquid, etc., which not only pollutes the environment, but also increases the cost of subsequent waste liquid treatment. Therefore, developing a sponge palladium recovery process with short process, high oxidation efficiency, environmental protection and suitable for high-impurity palladium concentrate has become a technical problem to be solved in the current rare and precious metal recovery field. SUMMARY

[0005] The purpose of the present application is to solve the problems of the prior art that the sponge palladium needs to be refined repeatedly to improve the purity in the palladium-containing waste recovery process, and the recovery rate of palladium is low, the process is complicated, the reagent consumption is large, and the environmental pollution is serious.

[0006] In order to achieve the above-mentioned purpose, the present application provides a method for recovering sponge palladium from palladium-containing waste, which comprises: (1) mixing the palladium-containing waste with hydrochloric acid in the presence of nano ozone bubbles to carry out oxidation leaching reaction, to obtain a palladium-containing leaching solution and a leaching residue; The nano-ozone bubbles are formed by treating ozone gas by a nano-micro bubble generator; the ozone gas is introduced at a flow rate of 0.8-1.2 L / min relative to 1 kg of the palladium-containing waste in terms of Pd element; the nano-ozone bubbles have an average diameter of 50-200 nm and a specific surface area of 1.4 x 10 4 -5.6 x 10 4 m 2 / g. (2) performing impurity removal treatment on the palladium-containing leaching solution to obtain an impurity-removed solution; (3) introducing the impurity-removed solution into a palladium adsorption resin to perform adsorption treatment, to obtain a palladium-containing resin and an exchange tail liquid; (4) introducing an eluent into the palladium-containing resin to perform desorption treatment, to obtain a palladium desorption solution; (5) mixing the palladium desorption solution with a reducing agent to perform reduction reaction, to obtain sponge palladium.

[0007] In some embodiments, in step (1), the amount of hydrochloric acid used is 5-8 L relative to 1 kg of the palladium-containing waste in terms of Pd element.

[0008] In some embodiments, in step (1), the conditions of the oxidative leaching reaction include: a temperature of 60-80 °C, a stirring rate of 300-600 rpm, and a time of 2-3 h.

[0009] In some embodiments, in step (2), the operation of the impurity removal treatment comprises: (S1) mixing the palladium-containing leaching solution with oxalic acid to perform precipitation reaction, to obtain a pretreated solution and copper-iron residue; (S2) performing flocculation sedimentation on the pretreated solution in the presence of polyacrylamide, to obtain the impurity-removed solution.

[0010] In some embodiments, in step (S1), the weight ratio of the palladium-containing waste to the oxalic acid used is 1:1.2-1.5.

[0011] In some embodiments, in step (S2), before performing the flocculation sedimentation, the pH value of the pretreated solution is adjusted to 1-2.

[0012] In some embodiments, in step (3), the palladium adsorption resin is a dibenzyl sulfoxide resin.

[0013] In some embodiments, in step (3), the impurity-removed solution is introduced at a flow rate of 1-2 BV / h.

[0014] In some embodiments, in step (4), the eluent is an acidified thiourea solution.

[0015] In some embodiments, in step (4), the flow rate of the eluent is 1-1.5 BV / h relative to 1 kg of the palladium-containing waste in terms of Pd element.

[0016] In some embodiments, in step (3), the adsorption treatment is performed at a temperature of 30-40℃, 2-4 times, and for 0.5-2 h.

[0017] In some embodiments, in step (4), the desorption treatment is performed at a temperature of 40-50℃, 2-3 times, and for 0.5-1.5 h.

[0018] In some embodiments, in step (5), the reducing agent is ascorbic acid.

[0019] In some embodiments, the weight ratio of the palladium-containing waste to the reducing agent is 1:2-3.

[0020] In some embodiments, in step (1), the method further comprises: washing the leaching residue with water, and combining the obtained washing solution with the palladium-containing leaching solution to perform the operation of step (2).

[0021] In some embodiments, in step (3), the method further comprises: recycling the exchange tail liquid to step (1) to participate in the oxidative leaching reaction.

[0022] By the above technical solution, the present application has at least the following advantages over the prior art: (1) The technical solution provided by the present application uses a nano microbubble generator to disperse ozone gas into nano bubbles with an average diameter of 50-200 nm, which has a large specific surface area, a specific surface area of 1.4 x 10 4 -5.6 x 10 4 m 2 / g, which is 100-1000 times that of traditional bubbles (without using a nano microbubble generator), has high mass transfer efficiency, and the utilization rate of ozone is increased to more than 90 wt%, which can quickly penetrate into the interior of palladium-containing waste particles, strengthen the oxidation of palladium and impurity metals by ozone, significantly shorten the leaching time by 40-50% compared with traditional nitric acid leaching, reduce the consumption of oxidizing agents, and the ozone consumption is only 60-70% of the traditional sodium chlorate consumption.

[0023] (2) The technical solution provided by the present application uses ozone gas as an oxidizing agent, and the oxidation products are mainly oxygen and water, which avoids the problem of generation of toxic gases such as nitrogen oxides and chlorine gas by traditional oxidizing agents (such as nitric acid and sodium chlorate); at the same time, no complex harmful impurities are generated after leaching, and the difficulty of subsequent waste liquid treatment is greatly reduced.

[0024] (3) In view of the defect that the inert oxide film formed by the elements in the high-impurity-content waste material affects the Pd oxidation rate, the technical scheme provided by the present application can effectively break the film and improve the oxidation power in the presence of nano ozone bubbles, thereby improving the purity of the sponge palladium obtained finally.

[0025] (4) The technical scheme provided by the present application realizes efficient utilization of reagents and water resources by circulating the exchange tail liquid to the corresponding process, reduces the production cost, and the solid waste such as leaching residue can also recover other valuable metals after simple treatment, thereby reducing solid waste discharge. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is a process flow chart of embodiment 4 of the present application. DETAILED DESCRIPTION

[0027] The endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The endpoints of the ranges and the values are approximate values and should be understood to include values approximately the same as the stated values. For ranges, the endpoints are included in the ranges, and the ranges are inclusive of the single values therein. For values, the value is inclusive of the single value.

[0028] In the present application, the palladium-containing waste material can be a palladium concentrate containing various impurities or a waste Pd / Al2O3 catalyst. In the palladium-containing waste material, the content of Pd is 0.05-70 wt%, the content of Cu is 0-5 wt%, the content of Fe is 0-15 wt%, and the content of Si is 0-20 wt%.

[0029] In the present application, the "BV / h" refers to the amount of liquid flowing through a unit volume of resin per unit time; and the specific surface area refers to the gas-liquid interface area corresponding to a unit mass of the nano ozone bubbles.

[0030] As described above, the present application provides a method for recovering sponge palladium from palladium-containing waste material, which comprises: (1) mixing the palladium-containing waste material with hydrochloric acid in the presence of nano ozone bubbles to perform an oxidation leaching reaction, to obtain a palladium-containing leaching liquid and a leaching residue; The nano ozone bubbles are formed by treating ozone gas by a nano micro-bubble generator; the amount of the ozone gas introduced is 0.8-1.2 L / min per 1 kg of the palladium-containing waste material in terms of Pd element; the average diameter of the nano ozone bubbles is 50-200 nm, and the specific surface area is 1.4×10 4 -5.6×10 4 m 2 / g; (2) subjecting the palladium-containing leaching solution to impurity removal treatment to obtain an impurity-removed solution; (3) passing the impurity-removed solution into a palladium adsorption resin to perform adsorption treatment, to obtain a palladium-containing resin and an exchange tail liquid; (4) passing an eluent into the palladium-containing resin to perform desorption treatment, to obtain a palladium desorption solution; (5) mixing the palladium desorption solution with a reducing agent to perform reduction reaction, to obtain sponge palladium.

[0031] In some embodiments, in step (1), the bubble concentration of the nano-ozone bubbles is 60-150 mg / L, and the Zeta potential is -40 mV to -20 mV.

[0032] In some embodiments, in step (1), the amount of hydrochloric acid used is 5-8 L relative to 1 kg of the palladium-containing waste in terms of Pd element.

[0033] In some embodiments, in step (1), the concentration of the hydrochloric acid is 5-7 mol / L.

[0034] In some embodiments, in step (1), the conditions of the oxidative leaching reaction include: a temperature of 60-80 ℃, a stirring rate of 300-600 rpm, and a time of 2-3 h.

[0035] In the present application, in step (1), the chemical reaction equation involved is shown in formula (I): Formula (I).

[0036] In some embodiments, in step (1), the substance participating in the oxidative leaching reaction also includes sodium tripolyphosphate; preferably, the weight ratio of the amount of the palladium-containing waste to the amount of the sodium tripolyphosphate is 1:0.0005-0.001.

[0037] In some embodiments, in step (1), the method further includes: subjecting the leaching residue to water washing, and combining the obtained water washing solution with the palladium-containing leaching solution to perform the operation of step (2).

[0038] In some embodiments, in step (2), the operation of the impurity removal treatment includes: (S1) mixing the palladium-containing leaching solution with oxalic acid to perform precipitation reaction, to obtain a pretreated solution and a copper-iron residue; (S2) subjecting the pretreated solution to flocculation sedimentation in the presence of polyacrylamide, to obtain an impurity-removed solution.

[0039] Optionally, in step (S1), the weight ratio of the amount of the palladium-containing waste to the amount of the oxalic acid is 1:1.2-1.5.

[0040] Optionally, in step (S1), the conditions of the precipitation reaction include: temperature of 50-60°C, time of 0.5-1.5h.

[0041] Optionally, in step (S2), before the flocculating sedimentation, the pH value of the pretreated solution is adjusted to 1-2.

[0042] Optionally, in step (S2), the polyacrylamide is in the form of a polyacrylamide solution, and the concentration of the polyacrylamide solution is 0.1-0.2g / L.

[0043] Optionally, in step (S2), the conditions of the flocculating sedimentation include: stirring rate of 150-300rpm, time of 10-40min.

[0044] In some embodiments, in step (3), the palladium adsorption resin is a dibenzyl sulfoxide resin.

[0045] Optionally, the average pore size of the palladium adsorption resin is 2-30nm, and the specific surface area is 100-150m 2 / g.

[0046] In some embodiments, in step (3), the flow rate of the impurity-removed solution is 1-2BV / h.

[0047] In some embodiments, in step (3), the conditions of the adsorption treatment include: temperature of 30-40°C, adsorption times of 2-4 times, time of 0.5-2h.

[0048] In some embodiments, in step (3), the method further comprises: circulating the exchange tail liquid to step (1) to participate in the oxidative leaching reaction.

[0049] In some embodiments, in step (4), the eluent is an acidified thiourea solution.

[0050] Optionally, the concentration of the acidified thiourea solution is 10-15wt%, and the pH value is 1-2.

[0051] Optionally, the acid liquid in the acidified thiourea solution is hydrochloric acid.

[0052] In some embodiments, in step (4), relative to 1kg of the palladium-containing waste in terms of Pd element, the flow rate of the eluent is 1-1.5BV / h.

[0053] In some embodiments, in step (4), the conditions of the desorption treatment include: temperature of 40-50°C, desorption times of 2-3 times, time of 0.5-1.5h.

[0054] In some embodiments, in step (5), the reducing agent is ascorbic acid.

[0055] In some embodiments, in step (5), the weight ratio of the palladium-containing waste to the reducing agent is 1:2-3.

[0056] Optionally, in step (5), the conditions of the reduction reaction include a temperature of 40-50°C and a time of 1-3h.

[0057] In the present application, the method further comprises post-treatment means known in the art such as filtration, washing and drying, and the like. For example, in step (4), the palladium-containing resin is repeatedly washed 2-3 times with 0.3-1.0 mol / L hydrochloric acid at a flow rate of 2-3 BV / h to wash off the soluble impurities adsorbed on the surface of the palladium-containing resin, and then the obtained product is passed into an eluent for desorption treatment to obtain the palladium desorption solution; in step (5), the product subjected to the reduction reaction is filtered to obtain a crude palladium precipitate and a reduction mother liquor, and then the crude palladium precipitate is repeatedly washed with deionized water until the washing liquid is neutral, and then vacuum dried at 80-100°C for 2-3h to obtain the sponge palladium, and the reduction mother liquor is concentrated by evaporation to recover thiourea for recycling. This will not be described here again, and those skilled in the art should not understand it as a limitation on the present application.

[0058] The present application will be described in detail below by way of examples. In the following examples, the reagents used are all ordinary commercially available products.

[0059] Palladium-containing waste (Pd-1): palladium concentrate from waste automobile catalyst waste; the content of Pd is 0.25wt%, the content of Cu is 0.18wt%, the content of Fe is 1.22wt%, and the content of Si is 0.06wt%.

[0060] Palladium-containing waste (Pd-2): waste Pd / Al2O3 catalyst from petroleum chemical catalyst waste; the content of Pd is 0.34wt%, and the content of Al2O3 is 98.8wt%.

[0061] Palladium-containing waste (Pd-3): high-impurity palladium concentrate from electronic waste; the content of Pd is 0.22wt%, the content of Cu is 0.2wt%, the content of Si is 0.08wt%, and the content of Bi is 0.06wt%.

[0062] Palladium-containing waste (Pd-4): palladium concentrate from pharmaceutical catalyst waste; the content of Pd is 3.72wt%, the content of Cu is 0.24wt%, the content of Fe is 0.74wt%, and the content of Si is 0.13wt%.

[0063] Dibenzyl sulfoxide resin: purchased from Shaanxi Laido Pharmaceutical Chemical Co., Ltd., with pore size of 2 nm-30 nm, specific surface area of 100-150 m 2 / g.

[0064] Nano microbubble generator: purchased from Jiangsu Enchain Environmental Technology Co., Ltd., model ELL-230, power 3500 W.

[0065] In the following examples, the test methods and calculation formulas involved include: Average diameter of nano-ozone bubbles and bubble concentration: NanoSight NS300 (Malvern Panalytical) was used for nanoparticle tracking analysis (NTA) determination to obtain the size / number weighted particle size distribution and number concentration of the bubbles, and the average diameter D was calculated based on the particle size distribution function n(D).

[0066] Zeta potential of nano-ozone bubbles: ZetaView PMX-x30 (Particle Metrix) instrument was used for determination to obtain.

[0067] Specific surface area of nano-ozone bubbles: based on the geometric characteristics of the bubbles and the physical properties of ozone, it is used to estimate the gas-liquid interface area corresponding to unit ozone mass. For approximately spherical bubbles, the volume and surface area are V=(4 / 3)πr 3 and A=4πr 2 ; Considering the relationship between the total interface area of the bubble population and the ozone gas mass, the specific surface area of unit ozone mass can be expressed as: Formula (II); In formula (II), is the ozone density (2.14×10 3 g·m -3 ), and D is the average diameter of nano-ozone bubbles.

[0068] Concentration of Pd in palladium-containing leaching solution: tested by ICP-OES (Perkin Elmer Avio 200) instrument.

[0069] Purity of sponge palladium: according to GB / T1420-2015, obtained by XRF spectrometer (Rigaku ZSX Primus II).

[0070] Palladium recovery rate (wt%) = (mass of recovered palladium / mass of palladium in palladium-containing waste) x 100%.

[0071] Preparation Example 1: Preparation of acidified thiourea solution-1 1400g of thiourea was dissolved in water, and the pH of the resulting thiourea solution was adjusted with hydrochloric acid to obtain acidified thiourea solution-1 with a concentration of 14wt% and a pH of 1.5.

[0072] Preparation Example 2: Preparation of acidified thiourea solution - 2 1500g of thiourea was dissolved in water, and the pH of the resulting thiourea solution was adjusted with hydrochloric acid to obtain an acidified thiourea solution-2 with a concentration of 15wt% and a pH of 1.

[0073] Preparation Example 3: Preparation of acidified thiourea solution - 3 1000g of thiourea was dissolved in water, and the pH of the resulting thiourea solution was adjusted with hydrochloric acid to obtain an acidified thiourea solution-3 with a concentration of 10wt% and a pH of 2.

[0074] Preparation Example 4: Preparation of acidified thiourea solution - 4 1200g of thiourea was dissolved in water, and the pH of the resulting thiourea solution was adjusted with hydrochloric acid to obtain an acidified thiourea solution-4 with a concentration of 12wt% and a pH of 1.5.

[0075] Example 1 (1) Oxidative leaching Ozone gas was introduced into a nano-microbubble generator to form nano-ozone bubbles. In the presence of these nano-ozone bubbles, 1 kg of palladium-containing waste (Pd-1) was mixed with hydrochloric acid (6 mol / L) and sodium tripolyphosphate in a reaction vessel for oxidative leaching. The mixture was filtered to obtain palladium-containing leachate and leaching residue. The concentration of Pd in ​​the palladium-containing leachate was measured to be 0.48 g / L. Specifically, the ozone gas injection rate is 1.2 L / min relative to 1 kg of palladium-containing waste (based on Pd element); the average diameter of the nano-ozone bubbles is 200 nm, and the specific surface area is 1.4 × 10⁻⁶. 4 m 2 / g; bubble concentration is 60mg / L, zeta potential is -40mV; The amount of hydrochloric acid used is 5L relative to 1kg of palladium-containing waste (calculated as Pd element). The weight ratio of palladium-containing waste to sodium tripolyphosphate is 1:0.001; The conditions for the oxidative leaching reaction were: temperature 80℃, stirring speed 600rpm, and time 2h.

[0076] (2) Impurity pretreatment The leaching residue was washed with water, and the resulting washing solution was combined with the palladium-containing leaching solution. Then, the palladium-containing leaching solution was mixed with oxalic acid to carry out a precipitation reaction (temperature 60℃, time 0.5h). The solution was filtered to obtain the pretreated liquid and copper-iron slag. The pH value of the pretreated solution is adjusted to 2 using NaOH, and then flocculation and sedimentation are performed in the presence of a polyacrylamide solution (concentration of 0.15 g / L) (stirring rate of 300 rpm, time of 10 min), and the solution after impurity removal is obtained by standing for 1 h to remove Si and Bi impurities; The weight ratio of the palladium-containing waste to oxalic acid is 1:1.2.

[0077] (3) Resin adsorption The solution after impurity removal is introduced into palladium adsorption resin (dibenzyl sulfide resin) for adsorption treatment to obtain palladium-containing resin and exchange tail liquid, and then the exchange tail liquid is recycled to step (1) to participate in the oxidation leaching reaction, and the palladium adsorption rate is tested to be 99.5 wt%; The adsorption treatment conditions are as follows: temperature of 30°C, adsorption times of 4, and time of 0.5 h; The flow rate of the solution after impurity removal is 1.5 BV / h.

[0078] (4) Washing and desorption Then, the palladium-containing resin is washed twice with 0.5 mol / L hydrochloric acid at a flow rate of 2 BV / h to wash off the soluble impurities adsorbed on the surface of the palladium-containing resin, and then the obtained product is introduced into eluent (acidified thiourea solution-1) for desorption treatment to obtain palladium desorption liquid, and the desorption rate is tested to be 99.6 wt%; The flow rate of the eluent is 1.5 BV / h; The desorption treatment conditions are as follows: temperature of 45°C, desorption times of 2, and time of 0.5 h.

[0079] (5) Reduction and drying The palladium desorption liquid is mixed with a reducing agent (ascorbic acid) for reduction reaction (temperature of 45°C, time of 2 h), the product of the reduction reaction is filtered to obtain crude palladium precipitate and reduction mother liquor, then the crude palladium precipitate is repeatedly washed with deionized water until the washing liquid is neutral, and then vacuum drying is performed at 100°C for 2.6 h to obtain sponge palladium 2.47 g, and the above-mentioned reduction mother liquor is evaporated and concentrated to recover thiourea for recycling; The weight ratio of the palladium-containing waste to the reducing agent is 1:2.5.

[0080] Example 2 (1) Oxidation leaching Ozone gas is introduced into a nano microbubble generator to form nano ozone bubbles, and 80 kg of palladium-containing waste (Pd-2) is placed in the nano ozone bubbles and subjected to roasting at 650°C for 2 h. The product obtained by the roasting is cooled, and then mixed with hydrochloric acid (concentration of 7 mol / L) and sodium tripolyphosphate in a reaction kettle to perform an oxidative leaching reaction, and a leaching residue and a Pd-containing leaching solution are obtained by filtration, and the concentration of Pd in the Pd-containing leaching solution is tested to be 0.48 g / L; The amount of ozone gas introduced is 1.1 L / min with respect to 1 kg of Pd-containing waste in terms of Pd element; the average diameter of the nano ozone bubbles is 50 nm, the specific surface area is 5.6 x 10 4 m 2 / g, the bubble concentration is 150 mg / L, and the Zeta potential is -20 mV; The amount of hydrochloric acid used is 6 L with respect to 1 kg of Pd-containing waste in terms of Pd element; The weight ratio of the amount of Pd-containing waste to sodium tripolyphosphate is 1:0.0006; The conditions of the oxidative leaching reaction are: the temperature is 75°C, the stirring rate is 300 rpm, and the time is 3 h.

[0081] (2) Impurity pretreatment The leaching residue is washed with water, and the obtained washing solution is combined with the Pd-containing leaching solution, and then the Pd-containing leaching solution is mixed with oxalic acid to perform a precipitation reaction (temperature of 50°C, time of 1 h), and a pretreated solution and a copper-iron residue are obtained by filtration; The pH value of the pretreated solution is adjusted to 2 using NaOH, and then flocculation sedimentation is performed in the presence of a polyacrylamide solution (concentration of 0.1 g / L) (stirring rate of 150 rpm, time of 40 min), and the solution is left to stand for 1 h to remove Si and Bi impurities, and a solution after impurity removal is obtained; The weight ratio of the amount of Pd-containing waste to oxalic acid is 1:1.5.

[0082] (3) Resin adsorption The solution after impurity removal is introduced into a palladium adsorption resin (dibenzyl sulfide resin) to perform adsorption treatment, and a Pd-containing resin and an exchange tail liquid are obtained, and then the exchange tail liquid is recycled to step (1) to participate in the oxidative leaching reaction, and the Pd adsorption rate is tested to be 99.3 wt%; The conditions of the adsorption treatment are: the temperature is 40°C, the adsorption times are 2, and the time is 2 h; The flow rate of the introduction of the solution after impurity removal is 1.0 BV / h.

[0083] (4) Washing and desorption Then the Pd-containing resin is washed 3 times using 0.8 mol / L of hydrochloric acid at a flow rate of 3 BV / h to wash away the soluble impurities adsorbed on the surface of the Pd-containing resin, and then the obtained product is introduced into an eluent (acidified thiourea solution-2) to perform desorption treatment, and a Pd desorption solution is obtained, and the desorption rate is tested to be 99.3 wt%; The flow rate of the eluent is 1 BV / h. The desorption treatment is performed at a temperature of 50℃ for 3 times and 1.5h.

[0084] (5) Reduction and drying The palladium desorption solution is mixed with a reducing agent (ascorbic acid) to perform a reduction reaction (at a temperature of 45℃ for 2h), the product of the reduction reaction is filtered to obtain a crude palladium precipitate and a reduction mother liquor, then the crude palladium precipitate is repeatedly washed with deionized water until the washing liquid is neutral, and then vacuum dried at 90℃ for 2h to obtain sponge palladium 267.92g, and the reduction mother liquor is concentrated by evaporation to recover thiourea for recycling; The weight ratio of the palladium-containing waste to the reducing agent is 1:3.

[0085] Example 3 (1) Oxidative leaching Ozone gas is introduced into a nano microbubble generator to form nano ozone bubbles, and 10kg of palladium-containing waste (Pd-3) is mixed with hydrochloric acid (concentration of 5mol / L) and sodium tripolyphosphate in a reaction kettle in the presence of the nano ozone bubbles to perform an oxidative leaching reaction, and a palladium-containing leaching solution and a leaching residue are obtained by filtration. The concentration of Pd in the palladium-containing leaching solution is 0.43g / L. The amount of ozone gas introduced is 0.8L / min for 1kg of palladium-containing waste in terms of Pd element; the average diameter of the nano ozone bubbles is 150nm, the specific surface area is 1.9×10 4 m 2 / g, the bubble concentration is 120mg / L, and the Zeta potential is -32mV; The amount of hydrochloric acid is 5L for 1kg of palladium-containing waste in terms of Pd element; The weight ratio of the palladium-containing waste to sodium tripolyphosphate is 1:0.005; The oxidative leaching reaction is performed at a temperature of 60℃, a stirring rate of 350rpm, and for 3h.

[0086] (2) Impurity pretreatment The leaching residue is washed with water, and the obtained washing liquid is combined with the palladium-containing leaching solution, and then the palladium-containing leaching solution is mixed with oxalic acid to perform a precipitation reaction (at a temperature of 50℃ for 1.5h), and a pretreated liquid and a copper-iron residue are obtained by filtration; The pH value of the pretreated liquid is adjusted to 1 using NaOH, and then flocculation and sedimentation are performed in the presence of a polyacrylamide solution (concentration of 0.2g / L) (stirring rate of 250rpm, time of 20min), and the solution is left to stand for 1h to remove Si and Bi impurities, and a de-impurity solution is obtained; The weight ratio of the palladium-containing waste to oxalic acid is 1:1.3.

[0087] (3) Resin adsorption The impurity-removed solution is introduced into palladium adsorption resin (dibenzyl sulfide resin) for adsorption treatment to obtain palladium-containing resin and exchange tail liquid, and then the exchange tail liquid is recycled to step (1) to participate in the oxidation leaching reaction. The palladium adsorption rate is 99.2wt% by testing. The adsorption treatment conditions are as follows: the temperature is 32°C, the adsorption times are 3, and the time is 1h. The flow rate of the introduction of the impurity-removed solution is 2.0BV / h.

[0088] (4) Washing and desorption Then the palladium-containing resin is washed twice with 0.4mol / L hydrochloric acid at a flow rate of 2BV / h to wash off the soluble impurities adsorbed on the surface of the palladium-containing resin, and then the obtained product is introduced into eluent (acidified thiourea solution-3) for desorption treatment to obtain palladium desorption liquid. The desorption rate is 99.4wt% by testing. The flow rate of the introduction of the eluent is 1.2BV / h. The desorption treatment conditions are as follows: the temperature is 42°C, the desorption times are 2, and the time is 1h.

[0089] (5) Reduction and drying The palladium desorption liquid is mixed with a reducing agent (ascorbic acid) for reduction reaction (temperature is 50°C, time is 2h), the product of the reduction reaction is filtered to obtain crude palladium precipitate and reduction mother liquor, then the crude palladium precipitate is repeatedly washed with deionized water until the washing liquid is neutral, and then vacuum drying is performed at 80°C for 3h to obtain sponge palladium 21.69g, and the above-mentioned reduction mother liquor is evaporated and concentrated to recover thiourea for recycling. The weight ratio of the palladium-containing waste to the reducing agent is 1:2.

[0090] Example 4 (1) Oxidation leaching Ozone gas is introduced into a nano microbubble generator to form nano ozone bubbles, and 1kg of palladium-containing waste (Pd-4) is mixed with hydrochloric acid (concentration is 6mol / L) and sodium tripolyphosphate in a reaction kettle in the presence of the nano ozone bubbles for oxidation leaching reaction. The palladium-containing leaching liquid and leaching residue are obtained by filtration, and the concentration of Pd in the palladium-containing leaching liquid is 0.54g / L by testing. The introduction amount of ozone gas is 1.0L / min relative to 1kg of palladium-containing waste in terms of Pd element; the average diameter of the nano ozone bubbles is 100nm, and the specific surface area is 2.8×10 4 m 2The bubble concentration was 95 mg / L, and the Zeta potential was -28 mV. The amount of hydrochloric acid was 6 L relative to 1 kg of the palladium-containing waste in terms of Pd element; The amount of sodium tripolyphosphate was 0.0005 times the weight of the palladium-containing waste; The conditions of the oxidative leaching reaction were as follows: a temperature of 70°C, a stirring rate of 500 rpm, and a time of 2.5 h.

[0091] (2) Impurity pretreatment The leaching residue was washed with water, and the obtained washing liquid was combined with the palladium-containing leaching liquid, and then mixed with oxalic acid to perform a precipitation reaction (a temperature of 55°C and a time of 1 h), and the pretreated liquid and copper-iron residue were obtained by filtration; The pH value of the pretreated liquid was adjusted to 1.5 using NaOH, and then flocculation sedimentation was performed in the presence of a polyacrylamide solution (a concentration of 0.15 g / L) (a stirring rate of 200 rpm and a time of 30 min), and the liquid after impurity removal was obtained by standing for 1 h to remove Si and Bi impurities; The amount of oxalic acid was 1.4 times the weight of the palladium-containing waste.

[0092] (3) Resin adsorption The liquid after impurity removal was introduced into a palladium adsorption resin (dibenzyl sulfoxide resin) to perform adsorption treatment, and a palladium-containing resin and an exchange tail liquid were obtained, and then the exchange tail liquid was recycled to step (1) to participate in the oxidative leaching reaction, and the palladium adsorption rate was 99.8 wt% obtained by testing; The conditions of the adsorption treatment were as follows: a temperature of 35°C, an adsorption number of 3 times, and a time of 1.2 h; The introduction flow rate of the liquid after impurity removal was 1.2 BV / h.

[0093] (4) Washing and desorption Then, the palladium-containing resin was washed 3 times using 0.5 mol / L hydrochloric acid at a flow rate of 3 BV / h to wash away the soluble impurities adsorbed on the surface of the palladium-containing resin, and then the obtained product was introduced into an eluent (acidified thiourea solution-4) to perform desorption treatment, and a palladium desorption liquid was obtained, and the desorption rate was 99.7 wt% obtained by testing; The introduction flow rate of the eluent was 1-1.5 BV / h; The conditions of the desorption treatment were as follows: a temperature of 45°C, a desorption number of 3 times, and a time of 1 h.

[0094] (5) Reduction and drying The palladium desorption solution is mixed with a reducing agent (ascorbic acid) to perform a reduction reaction (temperature 45℃, time 2h), the product of the reduction reaction is filtered to obtain a crude palladium precipitate and a reduction mother liquor, then the crude palladium precipitate is repeatedly washed with deionized water until the washing liquid is neutral, and then vacuum dried at 100℃ for 2.5h to obtain sponge palladium 36.90g, and the reduction mother liquor is concentrated by evaporation to recover thiourea for recycling; The weight ratio of the palladium-containing waste to the reducing agent is 1:2.4.

[0095] The process flow chart of the method of this example is shown in Figure 1 .

[0096] Example 5 The method is performed in a similar manner to Example 4, except that in step (4), the flow rate of the eluent is adjusted to 2.5BV / h while keeping the amount of palladium-containing waste unchanged; The rest are the same, and sponge palladium 34.62g is obtained.

[0097] Comparative Example 1 The method is performed in a similar manner to Example 4, except that the nano microbubble generator is not used, and ozone gas is directly introduced, that is, 1kg of palladium-containing waste (Pd-4) is mixed with hydrochloric acid (concentration 6mol / L) in the presence of ozone gas in a reaction kettle to perform an oxidative leaching reaction; The amount of ozone gas introduced is 1.0L / min relative to 1kg of palladium-containing waste in terms of Pd element; The rest are the same, and sponge palladium 27.75g is obtained.

[0098] Comparative Example 2 The method is performed in a similar manner to Example 4, except that the ozone is replaced by oxygen; that is, oxygen gas is introduced into a nano microbubble generator to form nano oxygen gas bubbles, and 1kg of palladium-containing waste (Pd-4) is mixed with hydrochloric acid (concentration 6mol / L) in the presence of the nano oxygen gas bubbles in a reaction kettle to perform an oxidative leaching reaction; The amount of oxygen gas introduced is 1.0L / min relative to 1kg of palladium-containing waste in terms of Pd element, so that the average diameter of the nano oxygen gas bubbles is 100nm, the bubble concentration is 72mg / L, and the Zeta potential is -32mV; The rest are the same, and sponge palladium 33.96g is obtained.

[0099] Comparative Example 3 The method is performed in a similar manner to Example 4, except that the ozone is replaced by oxygen, and the nano microbubble generator is not used, and oxygen gas is directly introduced; The amount of oxygen gas introduced is 1.0 L / min with respect to 1 kg of the palladium-containing waste material in terms of Pd element; The rest is the same, and sponge palladium 4.54 g is obtained.

[0100] Comparative Example 4 The method is similar to that of Example 4, except that the amount of palladium-containing waste material is kept unchanged, and the amount of ozone gas introduced is adjusted to 2.5 L / min, so that the average diameter of the nano-ozone bubbles is 400 nm, the specific surface area is 7.0 x 10 3 m 2 / g, the bubble concentration is 30 mg / L, and the Zeta potential is -10 mV; The rest is the same, and sponge palladium 2.79 g is obtained.

[0101] Test Example The purity and the recovery rate of palladium of the sponge palladium obtained in each of the above examples are tested, and the results are shown in Table 1.

[0102] Table 1

[0103] The results show that, compared with Example 4, the recovery rate of palladium in Comparative Example 1 is 24.8wt% lower, indicating that the nano-microbubble ozone can improve the reaction efficiency of oxygen and palladium and improve the dissolution efficiency of palladium; the recovery rate of palladium in Comparative Example 2 is 7.9wt% lower than that of the method of Example 4, indicating that the nano-microbubble ozone has a better dissolution effect on palladium than the nano-microbubble oxygen; the recovery rate of palladium in Comparative Example 3 is 86.6wt% lower than that of Comparative Example 2, indicating that the nano-microbubble oxygen can greatly improve the dissolution efficiency of oxygen on palladium.

[0104] Compared with Example 4, the amount of ozone gas introduced in Comparative Example 4 is too large, which leads to rapid coalescence of the bubbles, the size of the nano-ozone bubbles is significantly increased, the specific surface area is significantly reduced, the mass transfer efficiency and the oxidation leaching rate are obviously decreased, and the recovery rate of palladium and the purity of sponge palladium are both significantly reduced.

[0105] Therefore, from the above results, it can be seen that the method for recovering sponge palladium from palladium-containing waste material provided by the present application can strengthen the leaching efficiency of palladium by adopting nano-ozone bubbles and the synergistic effect of oxidation leaching reaction, impurity removal treatment, adsorption treatment, desorption treatment and reduction reaction, and the purity of the obtained sponge palladium is high, and the method is simple in operation, energy-saving and environmentally friendly.

[0106] In addition, the method is not limited to the dissolution refining recovery of palladium, but can also be used for the dissolution refining recovery of other precious metals such as gold, platinum, rhodium, ruthenium, iridium, gallium and indium, etc., and has a wide application prospect.

[0107] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including that each technical feature is combined in any other suitable manner. These simple modifications and combinations should also be considered as disclosed by the present application and fall within the protection scope of the present application.

Claims

1. A process for the recovery of sponge palladium from palladium-containing waste material, characterized in that, The method comprises: (1) mixing the palladium-containing waste with hydrochloric acid in the presence of nano-ozone bubbles to perform an oxidative leaching reaction, to obtain a palladium-containing leaching solution and a leaching residue; The nano-ozone bubbles are formed by treating ozone gas with a nano-microbubble generator; the ozone gas is introduced at a rate of 0.8-1.2 L / min relative to 1 kg of the palladium-containing waste material in terms of Pd element; the average diameter of the nano-ozone bubbles is 50-200 nm, and the specific surface area is 1.4×10 4 -5.6×10 4 m 2 / g. (2) performing impurity removal treatment on the palladium-containing leaching solution to obtain a post-impurity removal solution; (3) passing the post-impurity removal solution into a palladium adsorption resin to perform adsorption treatment, to obtain a palladium-containing resin and an exchange tail liquid; (4) passing the palladium-containing resin into an eluent to perform desorption treatment, to obtain a palladium desorption solution; (5) mixing the palladium desorption solution with a reducing agent to perform a reduction reaction, to obtain sponge palladium.

2. The method of claim 1, wherein, In step (1), the amount of hydrochloric acid used is 5-8 L relative to 1 kg of the palladium-containing waste in terms of Pd element.

3. The method of claim 1, wherein, In step (1), the conditions of the oxidative leaching reaction include: a temperature of 60-80 ℃, a stirring rate of 300-600 rpm, and a time of 2-3 h.

4. The method of any of claims 1-3, wherein, In step (2), the operation of the impurity removal treatment comprises: (S1) mixing the palladium-containing leaching solution with oxalic acid to perform a precipitation reaction, to obtain a pretreated solution and a copper-iron residue; (S2) performing flocculation sedimentation on the pretreated solution in the presence of polyacrylamide, to obtain a post-impurity removal solution.

5. The method of claim 4, wherein, In step (S1), the weight ratio of the amount of the palladium-containing waste to the amount of the oxalic acid is 1:1.2-1.5; And / or, in step (S2), the pH value of the pretreated solution is adjusted to 1-2 before the flocculation sedimentation is performed.

6. The method of any of claims 1-3, wherein, In step (3), the palladium adsorption resin is a dibenzyl sulfoxide resin; And / or, in step (3), the flow rate at which the post-impurity removal solution is passed in is 1-2 BV / h.

7. The method of any of claims 1-3, wherein, In step (4), the eluent is an acidified thiourea solution; And / or, in step (4), the flow rate at which the eluent is passed in is 1-1.5 BV / h relative to 1 kg of the palladium-containing waste in terms of Pd element.

8. The method of any one of claims 1-3, wherein, In step (3), the conditions of the adsorption treatment include: a temperature of 30-40 ℃, an adsorption number of 2-4 times, and a time of 0.5-2 h; And / or, in step (4), the conditions of the desorption treatment include: a temperature of 40-50 ℃, a desorption number of 2-3 times, and a time of 0.5-1.5 h.

9. The method of any of claims 1-3, wherein, In step (5), the reducing agent is ascorbic acid; And / or, the weight ratio of the amount of the palladium-containing waste to the amount of the reducing agent is 1:2-3.

10. The method of any one of claims 1-3, wherein, In step (1), the method further comprises: performing water washing on the leaching residue, and combining the obtained water washing solution with the palladium-containing leaching solution to perform the operation of step (2); And / or, in step (3), the method further comprises: recycling the exchange tail liquid to step (1) to participate in the oxidative leaching reaction.

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