A method for purifying and recovering platinum

Abstract

The application relates to the technical field of platinum recovery, and particularly discloses a method for purifying and recovering platinum. The method for purifying and recovering platinum comprises the following steps: extracting chloroplatinate ions from a liquid to be purified by using an organic extractant, the liquid to be purified being an aqueous solution in which platinum exists in the form of chloroplatinate ions, and separating an organic phase; the organic extractant is obtained by dispersing 2-(thiophenylmethyl) diethyl phosphonate in methyltrioctylammonium chloride; reacting the chloroplatinate ions in the organic phase with an aqueous reagent, separating the organic phase and the aqueous phase, back-extracting platinum into the aqueous phase, and separating the aqueous phase; adding a reagent to the aqueous phase to convert the platinum into a precipitate; separating the precipitate, and calcining to obtain elemental platinum. The methyltrioctylammonium chloride and 2-(thiophenylmethyl) diethyl phosphonate synergistically extract the chloroplatinate ions with high selectivity, have extremely high extraction capacity, reduce the amount of the organic extractant, and reduce the pressure of subsequent treatment of the organic extractant.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of platinum recovery, and discloses a method for purifying and recovering platinum. BACKGROUND

[0002] Platinum is a noble metal known for its chemical properties and wide range of applications. Platinum scrap recovery is of great significance for reducing resource waste and environmental protection. The application range of platinum scrap recovery includes the automotive industry, electronic waste, medical equipment, and the chemical industry. When recovering platinum scrap, sustainability and environmental protection must be considered, and appropriate safety measures and waste disposal methods must be taken to prevent harm to the environment.

[0003] Common methods for platinum scrap recovery include ion exchange, chemical precipitation, and extraction.

[0004] The ion exchange method first converts metallic platinum into chloroplatinate ions [PtCl6] 2- form, and then platinum is selectively adsorbed by a fixed bed ion exchange column filled with resin, and most of the impurity metals directly flow out. Then, a specific eluent (such as an acidic solution of thiourea, a solution of perchloric acid, or a strong oxidizing agent solution) is used to elute platinum from the resin, obtaining a high-concentration platinum eluent. The eluent is further treated (such as reduction, precipitation) to obtain pure platinum products. This method is simple to operate and environmentally friendly. The resin has good enrichment ability for platinum in dilute solution. However, resin adsorption is a solid-liquid diffusion process, and the mass transfer rate is usually slow. For high-concentration platinum feed liquid, the resin will quickly saturate, and frequent regeneration is required, which is cumbersome to handle. In addition, due to the strong binding force of the resin to platinum, the resin is easily damaged after elution, affecting the purity of the platinum eluent for the next elution.

[0005] The chemical precipitation method first dissolves the recovery waste with aqua regia for pretreatment, so that the metallic platinum is converted into chloroplatinate ions [PtCl6] 2- form. NH4Cl is directly added to the solution to precipitate platinum in the form of (NH4)2PtCl6, and the calcined precipitate is obtained. The platinum prepared by chemical precipitation contains a large amount of other types of metal impurities, and repeated multiple dissolution and precipitation are required to prepare the synthetic product.

[0006] In order to reduce the impurity content of the recovered platinum, an extraction method uses N-methylaminosulfonic acid and di(2-ethylhexyl) phosphate to form an organic extraction phase to extract a platinum-containing liquid, then uses an aqueous thiourea solution to back-extract the platinum, uses ammonium chloride to precipitate the platinum, and performs calcination to obtain the platinum. The extraction method leaves most of the impurity metals in the solvent through extraction and back-extraction, thereby improving the purity of the recovered platinum. However, a small part of the impurity metals is still mixed with the platinum after one extraction and back-extraction, and the purity and recovery rate of the recovered platinum still have room for improvement. In addition, the extraction capacity of the currently used organic extraction phase is small, and the use amount of the organic extraction phase is large, which brings great pressure to the subsequent treatment of the organic extraction phase. SUMMARY

[0007] In view of the problems existing in the above-mentioned purification and recovery method of platinum, the present application proposes an extraction method that uses an organic solvent with large extraction capacity to purify and recover platinum. The technical solution is as follows.

[0008] A method for purifying and recovering platinum, comprising:

[0009] firstly, using an organic extractant to extract chloroplatinate ions from a liquid to be purified, the liquid to be purified being an aqueous solution in which platinum exists in the form of chloroplatinate ions, and after separation, an organic phase is separated out; the organic extractant is obtained by dispersing diethyl 2-(thiophenylmethyl) phosphonate in methyltrioctylammonium chloride;

[0010] reacting an aqueous reagent with the chloroplatinate ions in the organic phase to separate into an organic phase and an aqueous phase, so that the platinum in the organic phase enters the aqueous phase through one back-extraction, and the aqueous phase is separated out;

[0011] adding a reaction agent to the aqueous phase to convert the platinum into a precipitate;

[0012] separating out the precipitate, and calcining the precipitate to obtain elemental platinum.

[0013] By using the above technical solution, the methyltrioctylammonium chloride has a hydrophobic long-chain quaternary ammonium cation group, which attracts the negatively charged chloroplatinate ions [PtCl6] 2- through electrostatic interaction at the water / organic phase interface, the diethyl 2-(thiophenylmethyl) phosphonate has a phosphonic acid group and a thiophene group, which coordinates with the platinum center through the dipole electrostaticity of the phosphonic acid group and the thiophene group and the activation of the quaternary ammonium cation group, forming a hydrophobic complex, and the two synergistically adsorb the negatively charged chloroplatinate ions [PtCl6] 2- , and the [PtCl6] 2- is selectively extracted into the organic phase, and the [PtCl6] 2-The organic phase is absorbed from the water phase, and the amount of other metal ions absorbed into the organic phase is small. The organic extractant obtained by dispersing 2-(thiophenyl) diethyl phosphonate in methyltrioctylammonium chloride has a larger extraction capacity and higher selectivity for platinum than the current N-methylaminosulfonic acid and di(2-ethylhexyl) phosphate organic extraction phase. Only one extraction and stripping are required, the purity of the recovered platinum is higher, reaching more than 99.95wt%, the amount of organic extractant is reduced, and the pressure of subsequent purification and recovery of the organic extractant is reduced.

[0014] It should be noted that the liquid to be purified is an aqueous solution in which platinum exists in the form of chloroplatinate ions. The source of the aqueous solution can be a solution containing platinum obtained by dissolving spent automobile exhaust catalysts, petroleum chemical catalysts, electronic waste (such as circuit boards and chips), and waste medical devices in aqua regia, as well as a solution containing platinum obtained by preliminary separation during the smelting process of platinum group metal mines. The platinum in these solutions has a divalent state and a tetravalent state. Chlorine gas is introduced to oxidize all the divalent platinum to tetravalent platinum. Then, concentrated hydrochloric acid is slowly added to the oxidized solution to make the pH of the solution less than 1 and the concentration of uncoordinated free chloride ions more than 3 mol / L. As a result, more than 99.9% of the platinum in the solution exists in the form of chloroplatinate ions, i.e., the aqueous solution in which platinum exists in the form of chloroplatinate ions is obtained. The concentration of uncoordinated free chloride ions can be measured by inserting a chloride ion selective electrode into the solution to be measured and directly reading the concentration value displayed by the instrument. The platinum element and other impurity metal elements in the liquid to be purified are simultaneously tested using an inductively coupled plasma optical emission spectrometer (ICP-OES).

[0015] A preferred scheme of the method for purifying and recovering platinum is to adjust the concentration of platinum in the liquid to be purified to 30g / L~40g / L.

[0016] By using the above technical scheme, for a solution with a platinum concentration outside the range of 30g / L~40g / L, the platinum concentration in the solution is adjusted to be within the range of 30g / L~40g / L by concentration or dilution. The organic extractant of the present application has a very high solubility for platinum within this concentration range, and can selectively extract platinum compounds from the water phase, while leaving most of the other metal ions in the water phase. If the platinum concentration is too high, more other metal impurities will be extracted. If the platinum concentration is too low, the reduction in the amount of organic extractant will be significantly smaller than the reduction in the platinum concentration, thereby significantly reducing the production efficiency.

[0017] A preferred scheme of the method for purifying and recovering platinum is that the mass ratio of the methyltrioctylammonium chloride and the diethyl 2-(thiophenylmethyl) phosphonate in the organic extractant is 10: (3-5). The volume ratio of the organic extractant and the liquid to be purified is (1-1.5): 1.

[0018] By using the above technical scheme, the load capacity of the methyltrioctylammonium chloride and the diethyl 2-(thiophenylmethyl) phosphonate in the above ratio for the chloroplatinate is large, so that the amount of the organic extractant to be put in is small, and the difficulty of subsequent treatment of the organic extractant is reduced.

[0019] A preferred scheme of the method for purifying and recovering platinum is that the aqueous reagent includes thiocyanic acid and hydrochloric acid. In the aqueous reagent, the concentration of the thiocyanic acid is 70 g / L-90 g / L, and the pH is 0-1. The volume ratio of the aqueous reagent and the liquid to be purified is (1-1.5): 1.

[0020] By using the above technical scheme, thiocyanic acid SC (NH2) 2 (hereinafter referred to as Tu) is a strong complexing agent, which can compete with platinum from the stable [PtCl6] 2- to form a cationic complex [Pt (Tu) 4] 2+ , and the chemical reaction formula is [PtCl6] 2- (organic phase) + 4Tu (aqueous phase)→ [Pt (Tu) 4] 2+ (aqueous phase) + 6Cl - The newly generated cationic complex [Pt (Tu) 4] 2+ is highly hydrophilic and can easily transfer (stripping) from the organic phase to the acidic aqueous phase containing thiocyanic acid. Excess thiocyanic acid will completely react with [PtCl6] 2- to form [Pt (Tu) 4] 2+ , so as to realize the separation of platinum and the organic extractant. In the acidic environment with a pH of 0-1, platinum will not hydrolyze to form platinum hydroxide precipitate.

[0021] A preferred scheme of the method for purifying and recovering platinum is that the temperature of the aqueous reagent and the chloroplatinate ion in the organic phase after mixing is 20°C-40°C.

[0022] By using the above technical scheme, at the lower temperature, the reaction of [PtCl6] 2- to form [Pt (Tu) 4] 2+ moves to the right until the reaction is complete, and [Pt (Tu) 4] 2+ can stably exist in the aqueous phase.

[0023] A preferred solution of the method for purifying and recycling platinum is that the reaction agent is an ammonium chloride solution with a concentration of 300 g / L to 370 g / L. The volume ratio of the reaction agent to the liquid to be purified is (0.1-0.2):1.

[0024] By using the above technical solution, the ammonium chloride solution is close to a saturated state, and the excess ammonium chloride will make [Pt(Tu)4] 2+ completely react to form an ammonium chloroplatinate (NH4)2PtCl6 yellow precipitate.

[0025] A preferred solution of the method for purifying and recycling platinum is that, after adding the reaction agent to the aqueous phase, the pH of the aqueous phase is maintained at 0-1, and the reaction is completed at 80-90°C.

[0026] By using the above technical solution, at 80-90°C, [Pt(Tu)4] 2+ is unstable and is easily attacked by chloride ions and ammonium groups to form an ammonium chloroplatinate (NH4)2PtCl6 yellow precipitate. Too high a pH may cause other metal impurities to co-precipitate or form a colloid; too low a pH may slightly increase the solubility of ammonium chloroplatinate, causing loss of platinum.

[0027] A preferred solution of the method for purifying and recycling platinum is that the calcination process includes: heating to 200-250°C to volatilize the water adsorbed in the precipitate; heating to 350-450°C to decompose the precipitate to form ammonium chloride and chlorine gas; heating to 520-600°C to volatilize the ammonium chloride; and cooling to obtain sponge platinum in an inert atmosphere.

[0028] By using the above technical solution, high-purity platinum is obtained. Before calcination, the precipitate can also be washed with a saturated ammonium chloride solution, and the solubility of the precipitate ammonium chloroplatinate in the washing liquid is low due to the common ion effect, thereby reducing the loss of the precipitate in the washing process. Washing can effectively remove the impurities (such as Cu 2+ , Ni 2+ , Zn 2+ chlorides, and residual iridium complexes) adsorbed on the surface of the precipitate, thereby improving the purity of the platinum product.

[0029] In summary, the method for purifying and recycling platinum has the following beneficial effects: in the first step of extraction, the chloroplatinate ions [PtCl6] 2- in the aqueous phase are transferred to the organic phase, and the methyltrioctylammonium chloride and 2-(thiophenylmethyl) phosphonic acid diethyl ester cooperatively adsorb the chloroplatinate ions [PtCl6] 2- with high selectivity, and the [PtCl6] 2-The water phase is absorbed into the organic phase, and the amount of other metal ions absorbed into the organic phase is small, the other metal impurities in the water phase are removed, the platinum is preliminarily purified, and the amount of methyltrioctylammonium chloride and diethyl 2-(thiophenyl) phosphonate is small, reducing the subsequent processing trouble of methyltrioctylammonium chloride and diethyl 2-(thiophenyl) phosphonate; in the second step of stripping, the chloroplatinate ions [PtCl6] 2- are transferred to the water phase to be converted into tetra thiourea platinum ions [Pt(Tu)4] 2+ , realizing the separation of platinum from the organic phase and deep purification, and creating conditions for the next step of precipitation reaction, and obtaining a pure platinum-containing stripping solution; in the third step of precipitation, the tetra thiourea platinum ions [Pt(Tu)4] 2+ in the water phase react with ammonium chloride to generate ammonium chloroplatinate (NH4)2PtCl6 precipitate, and the precipitate is calcined to obtain high-purity and stable platinum product. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 Reference is made to the flow of Example 1. DETAILED DESCRIPTION

[0031] The initial solution used in the following examples and comparative examples is an aqueous solution with pH = 0.5, and the platinum in the initial solution is in the form of chloroplatinate ions [PtCl6] 2- , and the content of each metal element in the initial solution is as follows: platinum 17.8 g / L, palladium 0.5 g / L, iridium 1.4 g / L, iron 8.0 g / L, copper 5.3 g / L, nickel 2.2 g / L, zinc 4.9 g / L, and lead 1.6 g / L.

[0032] Example 1, a method for purifying and recovering platinum, reference Figure 1 , comprising the following steps.

[0033] S1, concentrating the initial solution to obtain a liquid to be purified, so that the concentration of platinum in the liquid to be purified is 35.6 g / L.

[0034] S2, dispersing diethyl 2-(thiophenyl) phosphonate in methyltrioctylammonium chloride, the mass ratio of methyltrioctylammonium chloride to diethyl 2-(thiophenyl) phosphonate is 10:4, to obtain an organic extractant. The organic extractant and the liquid to be purified are mixed in a volume ratio of 1.2:1, so that the chloroplatinate ions [PtCl6] 2- are extracted from the liquid to be purified into the organic extractant, and the water phase and the organic phase are separated, and the chloroplatinate ions [PtCl6] 2- enter the organic phase, and then the organic phase of this step is separated out.

[0035] S3, configure a thiourea aqueous solution, and adjust the pH of the aqueous solution to 0.5 with hydrochloric acid, and the final concentration of thiourea SC(NH2)2 (hereinafter referred to as Tu) is 80 g / L, thereby obtaining an aqueous reagent. The aqueous reagent is used to extract chloroplatinate ions [PtCl6] 2- from the organic phase obtained in step S2, and the specific adding method is that the aqueous reagent is added into the organic phase obtained in step S2 according to the volume ratio of the aqueous reagent to the liquid to be purified being 1.2:1, and the mixture is fully mixed, and the temperature of the mixture of the aqueous reagent and the organic phase is 30°C, so that the chloroplatinate ions [PtCl6] 2- react with thiourea to generate tetrathiotetrachloroplatinate ions [Pt(Tu)4] 2+ After the water phase and the organic phase are separated, the tetrathiotetrachloroplatinate ions [Pt(Tu)4] 2+ enter the water phase, and the water phase of this step is separated.

[0036] S4, configure an ammonium chloride solution with a concentration of 330 g / L, which is a reaction agent. The reaction agent is added into the water phase obtained in step S3 according to the volume ratio of the reaction agent to the liquid to be purified being 0.15:1, the pH of the water phase is maintained at 0.5, and the water phase is heated to 85°C for 0.5 hours, so that the ammonium chloride combines with the tetrathiotetrachloroplatinate ions to completely react and generate a precipitate of ammonium chloroplatinate (NH4)2PtCl6.

[0037] S5, the precipitate of step S4 is separated, the precipitate is washed with saturated ammonium chloride solution for 3 times, the volume ratio of the saturated ammonium chloride solution used for each washing to the liquid to be purified is 1:10, and the precipitate is calcined. The calcination process is as follows: the temperature is raised to 220°C and maintained for 0.5 hours to volatilize the water adsorbed in the precipitate; the temperature is raised to 400°C and maintained for 1 hour to decompose the precipitate to generate ammonium chloride and chlorine gas; the temperature is raised to 560°C and maintained for 0.5 hours to volatilize the ammonium chloride; and the temperature is cooled to room temperature in a nitrogen atmosphere to obtain sponge platinum, which is the platinum element.

[0038] Example 2, a method for purifying and recovering platinum, comprising the following steps.

[0039] S1, the initial liquid is concentrated to obtain a liquid to be purified, so that the concentration of platinum in the liquid to be purified is 30.26 g / L.

[0040] S2, 2-(thiophenyl) diethyl phosphonate is dispersed in methyltrioctylammonium chloride, and the mass ratio of the methyltrioctylammonium chloride to the 2-(thiophenyl) diethyl phosphonate is 10:3, thereby obtaining an organic extractant. The organic extractant and the liquid to be purified are fully mixed according to the volume ratio of 1:1, so that the chloroplatinate ions [PtCl6] 2- are extracted from the liquid to be purified into the organic extractant, and the water phase and the organic phase are separated, and the chloroplatinate ions [PtCl6]2- into the organic phase, and then the organic phase of this step is separated.

[0041] S3, a thiourea aqueous solution is configured, and the pH of the aqueous solution is adjusted to 0 with hydrochloric acid, and the final concentration of thiourea SC(NH2)2 (hereinafter referred to as Tu) is 70 g / L, thereby obtaining an aqueous reagent. The aqueous reagent is used to extract the chloroplatinate ion [PtCl6] in the organic phase obtained in step S2 out, and the volume ratio of the aqueous reagent to the liquid to be purified is 1.5:1. 2- The temperature of the mixture of the aqueous reagent and the organic phase is 20°C, and the chloroplatinate ion [PtCl6] in the organic phase obtained in step S2 reacts with the thiourea to form a tetrathiotetrachloroplatinate ion [Pt(Tu)4]. 2- 2+ After the water phase and the organic phase are separated, the tetrathiotetrachloroplatinate ion [Pt(Tu)4] enters the water phase, and the water phase of this step is separated. 2+

[0042] S4, an ammonium chloride solution with a concentration of 300 g / L is configured as a reagent. The reagent is added to the water phase obtained in step S3, and the volume ratio of the reagent to the liquid to be purified is 0.1:1. The pH of the water phase is maintained at 0, and the water phase is heated to 80°C for 0.5 hours. The ammonium chloride combines with the tetrathiotetrachloroplatinate ion to completely react and form a precipitate of ammonium chloroplatinate (NH4)2PtCl6.

[0043] S5, the precipitate obtained in step S4 is separated and washed with saturated ammonium chloride solution for 3 times. The volume ratio of the saturated ammonium chloride solution used for each washing to the liquid to be purified is 1:10. The precipitate is calcined. The calcination process is as follows: the temperature is raised to 200°C and maintained for 0.5 hours to volatilize the water adsorbed in the precipitate; the temperature is raised to 350°C and maintained for 1 hour to decompose the precipitate to form ammonium chloride and chlorine gas; the temperature is raised to 520°C and maintained for 0.5 hours to volatilize the ammonium chloride; and the temperature is cooled to room temperature in a nitrogen atmosphere to obtain sponge platinum, which is the platinum element.

[0044] Example 3, a method for purifying and recovering platinum, comprising the following steps.

[0045] S1, the initial liquid is concentrated to obtain a liquid to be purified, so that the concentration of platinum in the liquid to be purified is 39.16 g / L.

[0046] S2, 2-(thiophenyl) diethyl phosphonate is dispersed in methyltrioctylammonium chloride, and the mass ratio of methyltrioctylammonium chloride to 2-(thiophenyl) diethyl phosphonate is 10:5, to obtain an organic extractant. The organic extractant and the liquid to be purified are mixed at a volume ratio of 1.5:1, so that the chloroplatinate ion [PtCl6]​​2- extracting from the liquid to be purified into the organic extractant, separating into an aqueous phase and an organic phase, chloroplatinate ions [PtCl6] 2- into the organic phase, and then separating the organic phase of this step.

[0047] S3, a thiourea aqueous solution is configured, and the pH of the aqueous solution is adjusted to 1 with hydrochloric acid, and the final concentration of thiourea SC(NH2)2 (hereinafter referred to as Tu) is 90 g / L, so as to obtain an aqueous reagent. The chloroplatinate ions [PtCl6] 2- are stripped out by using the aqueous reagent, and the aqueous reagent is added to the organic phase obtained in step S2 according to a volume ratio of the aqueous reagent to the liquid to be purified of 1:1, and the mixture is fully mixed. The temperature of the mixture of the aqueous reagent and the organic phase is 40℃, so that the chloroplatinate ions [PtCl6] 2- react with thiourea to generate tetrathiotetrachloroplatinate ions [Pt(Tu)4] 2+ After separating into an aqueous phase and an organic phase, the tetrathiotetrachloroplatinate ions [Pt(Tu)4] 2+ enter the aqueous phase, and the aqueous phase of this step is separated.

[0048] S4, an ammonium chloride solution with a concentration of 370 g / L is configured as a reagent. The reagent is added to the aqueous phase obtained in step S3 according to a volume ratio of the reagent to the liquid to be purified of 0.2:1, the pH of the aqueous phase is maintained at 1, and the aqueous phase is heated to 90℃ for 0.5 hours. The ammonium chloride combines with the tetrathiotetrachloroplatinate ions to completely react and generate a precipitate of ammonium chloroplatinate (NH4)2PtCl6.

[0049] S5, the precipitate of step S4 is separated, the precipitate is washed with saturated ammonium chloride solution for 3 times, the volume ratio of the saturated ammonium chloride solution used for each washing to the liquid to be purified is 1:10, and the precipitate is calcined. The calcination process is as follows: the temperature is raised to 250℃ and maintained for 0.5 hours to volatilize the water adsorbed in the precipitate; the temperature is raised to 450℃ and maintained for 1 hour to decompose the precipitate to generate ammonium chloride and chlorine gas; the temperature is raised to 600℃ and maintained for 0.5 hours to volatilize the ammonium chloride; and the temperature is cooled to room temperature in a nitrogen atmosphere to obtain sponge platinum, which is the platinum element.

[0050] Comparative Example 1

[0051] This comparative example discloses a method for purifying and recovering platinum. Compared with Example 1, the initial liquid is not concentrated, and the initial liquid is directly used as the liquid to be purified. The platinum concentration of this comparative example is 1 / 2 of the platinum concentration of Example 1, and the amount of organic extractant is correspondingly reduced by half. The method for purifying and recovering platinum of this comparative example is as follows.

[0052] A method for purifying and recovering platinum, comprising the following steps.

[0053] S1, the initial solution is directly used as the liquid to be purified, and the platinum concentration is 17.8 g / L.

[0054] S2, 2-(thiophenyl) diethyl phosphonate is dispersed in methyltrioctylammonium chloride, and the mass ratio of methyltrioctylammonium chloride to 2-(thiophenyl) diethyl phosphonate is 10:4, to obtain an organic extractant. The organic extractant and the liquid to be purified are mixed at a volume ratio of 0.6:1, so that the chloroplatinate ion [PtCl6] 2- is extracted from the liquid to be purified into the organic extractant, and is separated into an aqueous phase and an organic phase. 2- enters the organic phase, and the organic phase of this step is separated out.

[0055] S3, an aqueous thiourea solution is prepared, and the pH of the aqueous solution is adjusted to 0.5 with hydrochloric acid, and the final concentration of thiourea SC(NH2)2 (hereinafter referred to as Tu) is 80 g / L, to obtain an aqueous reagent. The chloroplatinate ion [PtCl6] 2- in the organic phase obtained in step S2 is back-extracted with the aqueous reagent, and the volume ratio of the aqueous reagent to the liquid to be purified is 1.2:1, so that the aqueous reagent is added to the organic phase obtained in step S2, and the mixture is mixed thoroughly, and the temperature of the mixture of the aqueous reagent and the organic phase is 30°C, so that the chloroplatinate ion [PtCl6] 2- reacts with thiourea to form a tetrathiotetrachloroplatinate ion [Pt(Tu)4] 2+ After being separated into an aqueous phase and an organic phase, the tetrathiotetrachloroplatinate ion [Pt(Tu)4] 2+ enters the aqueous phase, and the aqueous phase of this step is separated out.

[0056] S4, an ammonium chloride solution with a concentration of 330 g / L is prepared, to obtain a reagent. The reagent is added to the aqueous phase obtained in step S3, and the volume ratio of the reagent to the liquid to be purified is 0.15:1, so that the reagent is added to the aqueous phase obtained in step S3, and the pH of the aqueous phase is maintained at 0.5, and the aqueous phase is heated to 85°C and reacted for 0.5 hours, so that the ammonium chloride combines with the tetrathiotetrachloroplatinate ion to completely react and form a precipitate of ammonium chloroplatinate (NH4)2PtCl6.

[0057] S5, the precipitate obtained in step S4 is separated out, and the precipitate is washed with saturated ammonium chloride solution for 3 times, and the volume ratio of the saturated ammonium chloride solution to the liquid to be purified is 1:10 for each washing, and the precipitate is calcined. The calcination process is as follows: the temperature is raised to 220°C and maintained for 0.5 hours, so that the water adsorbed in the precipitate is volatilized; the temperature is raised to 400°C and maintained for 1 hour, so that the precipitate is decomposed to form ammonium chloride and chlorine gas; the temperature is raised to 560°C and maintained for 0.5 hours, so that the ammonium chloride is volatilized; the temperature is cooled to room temperature in a nitrogen atmosphere, to obtain sponge platinum, which is the platinum element.

[0058] Comparative Example 2

[0059] The comparative example discloses a method for purifying and recovering platinum. Compared with Example 1, the initial solution is concentrated to a platinum concentration of 71.2 g / L, i.e. the platinum concentration of the comparative example is twice that of Example 1, and the amount of organic extractant, aqueous reagent and reaction agent is increased by one time. The method for purifying and recovering platinum in the comparative example is as follows.

[0060] A method for purifying and recovering platinum, comprising the following steps.

[0061] S1, the initial solution is directly used as the liquid to be purified, and the platinum concentration is 71.2 g / L.

[0062] S2, 2-(thiophenylmethyl) diethyl phosphonate is dispersed in methyltrioctylammonium chloride, and the mass ratio of methyltrioctylammonium chloride to 2-(thiophenylmethyl) diethyl phosphonate is 10:4, to obtain an organic extractant. The organic extractant and the liquid to be purified are mixed in a volume ratio of 2.4:1, so that the chloroplatinic acid ion [PtCl6] 2- is extracted from the liquid to be purified into the organic extractant, and is separated into an aqueous phase and an organic phase. 2- enters the organic phase, and the organic phase of this step is separated out.

[0063] S3, an aqueous thiourea solution is prepared, and the pH of the aqueous solution is adjusted to 0.5 with hydrochloric acid, and the final concentration of thiourea SC(NH2)2 (hereinafter referred to as Tu) is 80 g / L, i.e. an aqueous reagent is obtained. The chloroplatinic acid ion [PtCl6] 2- in the organic phase obtained in step S2 is stripped out using the aqueous reagent, and the aqueous reagent is added to the organic phase obtained in step S2 in a volume ratio of 2.4:1, and the mixture is mixed thoroughly. The temperature of the mixture of the aqueous reagent and the organic phase is 30°C, so that the chloroplatinic acid ion [PtCl6] 2- reacts with thiourea to form a tetrathiotetrachloroplatinum ion [Pt(Tu)4] 2+ After being separated into an aqueous phase and an organic phase, the tetrathiotetrachloroplatinum ion [Pt(Tu)4] 2+ enters the aqueous phase, and the aqueous phase of this step is separated out.

[0064] S4, ammonium chloride solution with concentration of 330 g / L is prepared as the reagent. The reagent is added into the aqueous phase obtained in step S3, the volume ratio of the reagent to the liquid to be purified is 0.3:1, the pH of the aqueous phase is maintained at 0.5, and the aqueous phase is heated to 85℃ for 0.5 hour. Ammonium chloride combines with platinum tetra thiourea ion to form (NH4)2PtCl6.

[0065] S5, the precipitate obtained in step S4 is separated, the precipitate is washed with saturated ammonium chloride solution for 3 times, the volume ratio of the saturated ammonium chloride solution to the liquid to be purified is 1:10, and the precipitate is calcined. The calcination process is as follows: the temperature is raised to 220℃ and maintained for 0.5 hour to volatilize the water adsorbed in the precipitate; the temperature is raised to 400℃ and maintained for 1 hour to decompose the precipitate to form ammonium chloride and chlorine; the temperature is raised to 560℃ and maintained for 0.5 hour to volatilize the ammonium chloride; and the temperature is cooled to room temperature in nitrogen atmosphere to obtain sponge platinum, which is the platinum element.

[0066] Comparative Example 3

[0067] The comparative example discloses a method for purifying and recovering platinum, and the only difference from example 1 is that the organic extractant is replaced by pure methyltrioctylammonium chloride, and the amount of the organic extractant remains unchanged, and sponge platinum is finally prepared.

[0068] Comparative Example 4

[0069] The comparative example discloses a method for purifying and recovering platinum, and the only difference from example 1 is that the organic extractant is pure 2-(thiophenyl) diethyl phosphonate, and the amount of the organic extractant remains unchanged, and sponge platinum is finally prepared.

[0070] Comparative Example 5

[0071] The comparative example discloses a method for purifying and recovering platinum, and the only difference from example 1 is that methyltrioctylammonium chloride is replaced by methyltrioctylammonium chloride, and the amount of the organic extractant remains unchanged, and sponge platinum is finally prepared.

[0072] Comparative Example 6

[0073] The comparative example discloses a method for purifying and recovering platinum, and the only difference from example 1 is that 2-(thiophenyl) diethyl phosphonate is replaced by triphenyl phosphite, and the amount of the organic extractant remains unchanged, and sponge platinum is finally prepared.

[0074] Comparative Example 7

[0075] The comparative example discloses a method for purifying and recovering platinum, and the only difference from example 1 is that methyltrioctylammonium chloride is replaced by N-methyl sulfamic acid, and the amount of the organic extractant remains unchanged, and sponge platinum is finally prepared.

[0076] Comparative Example 8

[0077] This comparative example discloses a method for purifying and recovering platinum, the only difference compared with Example 1 is that 2-(thiophenylmethyl) diethyl phosphonate is replaced by bis(2-ethylhexyl) phosphate, the amount of organic extractant is unchanged, and sponge platinum is finally prepared.

[0078] Comparative Example 9

[0079] This comparative example discloses a method for purifying and recovering platinum, the only difference compared with Example 1 is that methyltrioctylammonium chloride is replaced by N-methylsulfamic acid, and 2-(thiophenylmethyl) diethyl phosphonate is replaced by bis(2-ethylhexyl) phosphate, the amount of organic extractant is unchanged, and sponge platinum is finally prepared.

[0080] The above examples and comparative examples all undergo one extraction and stripping, and sponge platinum is finally prepared.

[0081] Test Example 1

[0082] The sponge platinum prepared in Examples 1-3 and Comparative Examples 1-9 above is respectively detected for purity by an inductively coupled plasma optical emission spectrometer (ICP-OES), and the detection method is as follows.

[0083] About 0.1 g of sponge platinum sample is accurately weighed and placed in a beaker. 1 mL of aqua regia is used for dissolution until it is clear. The dissolved solution is repeatedly added with hydrochloric acid to remove nitrogen oxide smoke until no brown nitrogen oxide smoke is generated, and finally platinum is converted into stable chloroplatinic acid. The solution is transferred to a volumetric flask and diluted with dilute hydrochloric acid to obtain a test solution.

[0084] A series of standard solutions of palladium, iridium, iron, copper, nickel, and zinc impurity elements at different concentrations are prepared, and the signal intensity of each impurity element at different concentrations is detected by ICP-OES to automatically generate a standard curve of each impurity element. The concentration of each impurity element in the test solution is determined by ICP-OES, and ICP-OES automatically substitutes the signal intensity of each impurity element in the test solution into the corresponding standard curve to calculate the concentration of the impurity in the test solution, so that the mass percentage of each impurity element in the sponge platinum can be calculated. Platinum purity = 100% - ∑ mass percentage of each impurity element.

[0085] The sponge platinum prepared in Examples 1-3 and Comparative Examples 1-9 above is respectively tested for recovery rate.

[0086] Full-process platinum recovery rate = mass of platinum in the test solution / mass of pure platinum in sponge platinum × 100%.

[0087] The purity and recovery rate of the sponge platinum prepared in Examples 1-3 and Comparative Examples 1-9 above are as shown in Table 1 below.

[0088] Table 1 Product purity and recovery rate statistics of recovered platinum

[0089] Sample Recovery (%) Purity (wt%) Example 1 99.75 99.96 Example 2 99.73 99.95 Example 3 99.76 99.95 Comparative Example 1 99.04 99.94 Comparative Example 2 99.71 98.82 Comparative Example 3 93.36 98.50 Comparative Example 4 94.48 98.76 Comparative Example 5 97.05 98.61 Comparative Example 6 96.27 98.34 Comparative Example 7 98.53 97.90 Comparative Example 8 98.75 98.28 Comparative Example 9 98.42 97.13

[0090] The results of Table 1 show that the purity of the products of Examples 1-3 is as high as 99.95wt%-99.96wt%, and the recovery rate is as high as 99.73%-99.76%, which shows that the method for purifying and recovering platinum in the present application has achieved remarkable results with a mass ratio of methyltrioctylammonium chloride to diethyl 2-(thiophenyl)phosphonate of 10:(3-5) in the mixed organic extractant, and through one extraction and stripping with a small amount of organic extractant, thereby reducing the pressure of subsequent treatment of the organic extractant.

[0091] Comparative Example 1 shows that, compared with Example 1, the amount of organic extractant is halved when the concentration of raw platinum is halved, the amount of aqueous reagent and its thiourea concentration remain unchanged, the amount of reaction agent and its ammonium chloride concentration remain unchanged, but the product recovery rate decreases while the product purity remains unchanged, which shows that the amount of organic extractant cannot be reduced by the same degree as the concentration of raw platinum, and the amount of organic extractant is too small compared with the amount of liquid to be purified, which reduces the product recovery rate even if the platinum concentration of the liquid to be purified is low. Therefore, the parameters of Examples 1-3 have higher extraction efficiency and higher economic benefits.

[0092] Comparative Example 2 shows that, compared with Example 1, the amount of organic extractant is doubled when the concentration of raw platinum is doubled, the amount of aqueous reagent is doubled, and the amount of reaction agent is doubled, but the purity of the product decreases while the recovery rate remains basically unchanged, mainly because the organic extractant easily extracts other impurity metal ions under high concentration of platinum, which reduces the purity of the product.

[0093] Comparative Examples 3-9 show that, compared with Example 1, the formula of the organic extractant is changed, and the purity and recovery rate of the product decrease to different degrees, which shows that the organic extractant mixed with methyltrioctylammonium chloride and diethyl 2-(thiophenyl)phosphonate in a mass ratio of 10:(3-5) in the present application has high extraction efficiency for chloroplatinate and high selectivity for chloroplatinate. For example, the extraction active group quaternary ammonium group of Examples 1-3 has higher selectivity for platinum than the secondary amine N-methyl amino sulfonic acid of Comparative Example 7, the extraction active group thiophene phosphonic acid group of Examples 1-3 has higher selectivity for platinum than the di(2-ethylhexyl)phosphate of Comparative Example 8, and the extraction active group quaternary ammonium group combined with the thiophene phosphonic acid group of Examples 1-3 has higher selectivity for platinum than the N-methyl amino sulfonic acid combined with the N-methyl amino sulfonic acid N-methyl amino sulfonic acid of Comparative Example 9, and thus has higher purity and recovery rate.

[0094] The application can efficiently and selectively extract platinum from a platinum-containing solution containing many impurity metals, and the organic extractant has a large extraction capacity for chloroplatinate, so that the amount of the organic extractant is small, the pressure of recovery or disposal of the organic extractant is reduced, and high economic benefits are obtained.

Claims

1. A method for purifying and recovering platinum, characterized in that, include: The platinum concentration in the solution to be purified was adjusted to 30 g / L~40 g / L. First, an organic extractant was used to extract chloroplatinate ions from the solution in a single step. The solution to be purified was an aqueous solution in which platinum exists as chloroplatinate ions. After separation, the organic phase was separated. The organic extractant was obtained by dispersing diethyl 2-(thiophenemethyl)phosphonate in methyltrioctylammonium chloride. The organic phase is separated into an organic phase and an aqueous phase by reacting with an aqueous reagent. Platinum in the organic phase is then back-extracted into the aqueous phase, thus separating the aqueous phase. Adding a reactant to the aqueous phase converts platinum into a precipitate; The precipitate was separated and calcined to obtain elemental platinum; In the organic extractant, the mass ratio of methyltrioctylammonium chloride to diethyl 2-(thiophenemethyl)phosphonate is 10:(3~5); the volume ratio of the organic extractant to the liquid to be purified is (1~1.5):

1.

2. The method for purifying and recovering platinum according to claim 1, characterized in that, The aqueous reagent includes thiourea and hydrochloric acid; in the aqueous reagent, the concentration of thiourea is 70 g / L to 90 g / L, and the pH is 0 to 1; the volume ratio of the aqueous reagent to the solution to be purified is (1 to 1.5):

1.

3. A method for purifying and recovering platinum according to claim 1 or 2, characterized in that, The process involves reacting an aqueous reagent with chloroplatinate ions in the organic phase, wherein the temperature after mixing the aqueous reagent and the organic phase is 20°C to 40°C.

4. The method for purifying and recovering platinum according to claim 1, characterized in that, The reactant is an ammonium chloride solution with a concentration of 300 g / L to 370 g / L; the volume ratio of the reactant to the solution to be purified is (0.1 to 0.2):

1.

5. A method for purifying and recovering platinum according to claim 1 or 4, characterized in that, After adding the reactant to the aqueous phase, the pH of the aqueous phase is maintained at 0~1, and the reaction is completed at 80℃~90℃.

6. The method for purifying and recovering platinum according to claim 1, characterized in that, The calcination process includes: heating to 200℃~250℃ to volatilize the water adsorbed in the precipitate; heating to 350℃~450℃ to decompose the precipitate into ammonium chloride and chlorine gas; heating to 520℃~600℃ to volatilize the ammonium chloride; and cooling in an inert atmosphere to obtain sponge platinum.

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