A process for the two-phase oxidation transfer of rhodium from a rhodium-containing organic waste solution to an aqueous phase

Abstract

This invention relates to a method for the two-phase oxidation and transfer of rhodium to an aqueous phase in rhodium-containing organic wastewater, belonging to the field of precious metal recycling and metallurgical technology. The invention employs a two-phase oxidation-transfer system. A chlorine-containing aqueous phase is added to an in-situ activated chlorine electrolysis unit for in-situ electrolysis to generate an activated chlorine aqueous phase. Carbon monoxide and the activated chlorine aqueous phase are then introduced into a two-phase contact unit to thoroughly mix and contact the pretreated rhodium-containing organic wastewater, sequentially undergoing a multi-stage oxidation-transfer reaction to obtain an oxidation-transfer reaction mixture. This reaction mixture is then introduced into a phase separation unit and separated by gravity into a lower rhodium-containing aqueous phase and an upper organic phase. The upper organic phase, depending on its rhodium content, returns to the first-stage mixing unit or the organic phase collection unit via a three-way pipe I. The lower rhodium-containing aqueous phase flows into the in-situ activated chlorine electrolysis unit via a three-way pipe II or, as a rhodium-rich aqueous phase, flows into the aqueous product collection unit via a three-way pipe II. This invention obtains a stable and treatable rhodium-rich aqueous phase while retaining a reusable organic phase.

Description

Technical Field

[0001] This invention relates to a method for the two-phase oxidation and transfer of rhodium from rhodium-containing organic waste liquid to the aqueous phase, belonging to the field of precious metal recycling metallurgy technology. Background Technology

[0002] Rhodium-containing organic waste catalysts mainly originate from homogeneous systems such as olefin carbonylation synthesis, alkylation / carbonylation, and selective hydrogenation. Typical examples include the reaction mother liquor, washing liquid, and concentrated tar residue of "Rh-phosphine (e.g., triphenylphosphine)-carbonyl" complexes in solvents such as aromatics / alkanes / ketones. Besides Rh complexes, these waste liquids often contain phosphine / phosphine oxides (e.g., PPh3, TPPO), unreacted substrates, byproduct aldehydes / alcohols / acids, small amounts of polymers, and trace amounts of inorganic salts. Physically, they exhibit high viscosity, easy emulsification, and large fluctuations in composition. Rhodium, as a rare and precious metal, is scarce, expensive, and its supply chain is sensitive to fluctuations, making its economic and strategic value significant. Simultaneously, organic components such as phosphine / phosphine oxides also have recycling value. Indiscriminate incineration or landfilling not only results in huge losses of rhodium and organic ligands but also creates an environmental burden of volatile organic compounds, chlorinated and phosphorus-containing organic compounds, and acidic tail gases. Therefore, establishing a scalable, controllable, and inherently safe recycling process for such complex organic systems is of direct significance for enterprises to reduce costs and increase efficiency, achieve closed-loop recycling of precious metals, and comply with environmental regulations.

[0003] Existing recovery technologies can be broadly classified into three categories: The first is the "external strong oxidant-aqueous phase transfer-precipitation / reduction" route, which involves adding active chlorine or peroxidation systems (such as Cl2, hypochlorite, chlorate, hydrogen peroxide, etc.) to the organic-aqueous two-phase system to increase the valence state of Rh and convert it into an aqueous phase, followed by enrichment using precipitation, reduction, or ion exchange resins; The second is the "physical separation-thermal treatment-acid dissolution" route, which involves recovering solvents and low-boiling organics through multi-stage distillation, incinerating or high-temperature fluxing the concentrated residue into oxides, and then dissolving and reducing them using a strong acid / chlorination system; The third is the "membrane / extraction / adsorption combined process," which utilizes ceramic ultrafiltration or organic solvent nanofiltration to remove large molecular weight tar, combined with extraction and resin adsorption to achieve Rh enrichment. These routes can achieve rhodium recovery to some extent in experiments or engineering, but they generally suffer from the following problems: organic phase side reactions (chlorination, condensation) under strong oxidizing conditions easily lead to emulsification and tar formation; incineration / high-temperature ashing and multi-stage distillation have high energy consumption; Rh(0) black colloids or insoluble oxides are easily generated at the two-phase interface, resulting in transfer / filtration losses; and a large amount of salt-containing mother liquor and solid waste are generated during the repeated precipitation-reduction cycle. In summary, existing technologies either rely on external strong oxidants or high-temperature heat treatment and multiple chemical cycles, which cannot meet the requirements of rapid and clear phase separation, suppression of colloid formation, and continuous operation with low salt load. Summary of the Invention

[0004] To address the problems of existing technologies that rely on external strong oxidants or high-temperature heat treatment and multiple chemical cycles for rhodium recovery from rhodium-containing organic waste, this invention proposes a two-phase oxidation method for transferring rhodium from rhodium-containing organic waste to the aqueous phase. In this invention, an active chlorination organic phase is formed in situ in the aqueous phase using chloride ions as the source, and carbon monoxide is used to inhibit the formation of Rh(0) colloidal / rhodium oxide secondary phase during oxidation, thus synergistically achieving selective rhodium transfer to the aqueous phase. This invention obtains a stable and treatable rhodium-rich aqueous phase, leaving sufficient selection space for subsequent conventional wet processes, while retaining the reusable organic phase.

[0005] A method for two-phase oxidation transfer of rhodium from rhodium-containing organic waste liquid to the aqueous phase is disclosed. The method employs a two-phase oxidation transfer system comprising a two-phase contact unit and an in-situ active chlorine electrolysis unit. The two-phase contact unit includes a mixing unit, a phase separation unit, an organic phase collection unit, and an aqueous phase product collection unit. The mixing unit has 1 to 4 stages of series mixing. The inlet of the mixing unit is the first-stage mixing unit. The outlet of the mixing unit is connected to the inlet of the phase separation unit. The organic phase outlet of the phase separation unit is connected to the inlet of the first-stage mixing unit and the organic phase collection unit via a three-way pipe I. The inlet of the first-stage mixing unit is connected to the outlet of the in-situ active chlorine electrolysis unit. The aqueous phase outlet of the phase separation unit is connected to the inlet of the aqueous phase product collection unit and the in-situ active chlorine electrolysis unit via a three-way pipe II.

[0006] The specific steps of the method are as follows:

[0007] (1) The rhodium-containing organic waste liquid is subjected to solid-liquid separation to remove solid impurities, then centrifuged and allowed to stand to remove the aqueous phase, and then diluted with a diluent to obtain the pretreated rhodium-containing organic waste liquid;

[0008] (2) Prepare a chlorine-containing aqueous phase, wherein the chlorine-containing aqueous phase contains hydrochloric acid and soluble chloride;

[0009] (3) The pretreated rhodium-containing organic waste liquid is placed in the first mixing unit of the two-phase contact unit. The chlorine-containing aqueous phase is added to the in-situ active chlorine electrolysis unit to generate an active chlorine aqueous phase. Carbon monoxide and the active chlorine aqueous phase are introduced into the mixing unit of the two-phase contact unit and fully mixed with the pretreated rhodium-containing organic waste liquid to carry out multi-stage oxidation-transfer reaction in sequence so that rhodium is oxidized and transferred to the aqueous phase to obtain an oxidation-transfer reaction mixture. The oxidation-transfer reaction mixture is introduced into the phase separation unit and separated by gravity into a lower rhodium-containing aqueous phase and an upper organic phase.

[0010] (4) When the rhodium content in the upper organic phase is greater than 0.005 g / L, the upper organic phase returns to the first-stage mixing unit through the three-way pipe I, and the lower rhodium-containing aqueous phase flows into the in-situ active chlorine electrolysis unit through the three-way pipe II to generate an active chlorine aqueous phase, which then flows into the first-stage mixing unit to achieve chlorine-containing aqueous phase circulation; when the rhodium content in the upper organic phase is less than or equal to 0.005 g / L, the upper organic phase flows into the organic phase collection unit as a rhodium-poor organic phase through the three-way pipe I; when the rhodium content in the lower rhodium-containing aqueous phase is not less than 2 g / L, the lower rhodium-containing aqueous phase flows into the aqueous phase product collection unit as a rhodium-rich aqueous phase through the three-way pipe II.

[0011] Preferably, the mixing unit is a multi-stage stirred tank or a multi-stage static mixer arranged in series, and the phase separation unit is a gravity settling device; the in-situ active chlorine electrolysis unit is a flow-through anode-cathode structure electrochemical workstation, with the anode being Ti / RuO2 or Ti / IrO2, the cathode being Ti, stainless steel or graphite, the reference electrode being Ag / AgCl, and the electrode spacing being 0.5~3 mm.

[0012] Preferably, the diluent in step (1) is one or more of isooctane, toluene, methyl isobutyl ketone, and ethyl acetate.

[0013] Preferably, the rhodium content in the rhodium-containing organic waste liquid pretreated in step (1) is 100-3000 mg / L.

[0014] Preferably, the chloride in step (2) is one or more of NaCl, KCl, LiCl, MgCl2, CaCl2, and NH4Cl.

[0015] More preferably, in step (2), the concentration of hydrochloric acid in the chlorinated aqueous phase is 4~8 mol / L, and the concentration of soluble chloride is 0.5~2.0 mol / L.

[0016] Preferably, using Ag / AgCl as the reference electrode, the redox potential of the in-situ electrolysis in step (3) is 600~950mV, the aqueous phase linear velocity is 0.1~1.0m / s, and the current density is 30~200 mA / cm². 2 The effective chlorine concentration in the aqueous phase, calculated as Cl2, is 0.5–3 mmol / L, and the ratio of free chloride ions to hydrogen ions is 0.1–1.0:1. Anodizing reduces the Cl2 concentration in the aqueous phase. - It is converted to Cl2(aq) and then reacts in acidic, high-Cl environments. - With water and Cl under ion concentration environment - The equilibrium produces Cl2(aq), HClO, and Cl3. - The specific reaction formula is:

[0017] Anode: 2Cl - →Cl2(aq)+2e- ;

[0018] Balance 1: ;

[0019] Balance 2: ;

[0020] Rh transfer:

[0021] [RhL n ]^{z +}+6Cl - +O x →[RhCl6]^{3 -}+L ox (L is the ligand, Ox is the active chlorine).

[0022] Preferably, in step (3), the volume ratio of the active chlorine aqueous phase to the pretreated rhodium-containing organic waste liquid is 1:1~5, the oxidation-transfer reaction temperature is 35~80℃, and the single-stage oxidation-transfer reaction time is 5~15 min.

[0023] Preferably, the partial pressure of carbon monoxide gas in step (3) is 0.3~2.0 bar.

[0024] The rhodium content in the upper organic phase and the lower rhodium-containing aqueous phase in step (4) can be determined by ICP-OES, ICP-MS or atomic absorption spectrometry.

[0025] The preferred method for determining the Rh content of the upper organic phase is as follows: Take 1-10 mL of the upper organic phase sample after phase separation, add aqua regia or hydrochloric acid-hydrogen peroxide digestion system, and heat the organic phase to fully decompose and transfer rhodium into the aqueous phase. After cooling, make up the volume and determine the Rh concentration using ICP-OES, ICP-MS or atomic absorption spectrometry.

[0026] The preferred method for determining the Rh content in the lower layer of rhodium-containing aqueous phase is as follows: Take the sample of the lower layer aqueous phase after phase separation, dilute and adjust the volume, and directly determine the Rh concentration using ICP-OES, ICP-MS or atomic absorption spectrometry. The above determination results are used as the basis for the flow control of the three-way tube I and the three-way tube II, respectively.

[0027] The principle of this invention for the two-phase oxidation and transfer of rhodium from rhodium-containing organic waste liquid to the aqueous phase is as follows: using chloride ions in the aqueous phase as the chlorine source, active chlorine (Cl2(aq), HClO, Cl3) is generated in situ via electrochemical oxidation. - The soluble species form is used to obtain an active chlorine aqueous phase. In this two-phase system, the rhodium-containing organic phase comes into contact with the active chlorine aqueous phase. The active chlorine in the aqueous phase is gently oxidized and cleaved at the liquid-liquid interface, causing Rh to change from an organic complexed state to an aqueously soluble [RhCl6]. 3-Meanwhile, a specific partial pressure of CO is provided in the contact domain to inhibit the formation of Rh(0) colloid and rhodium oxide secondary phase. Within the controlled acidity, chloride ion activity and ORP range, Rh selectively migrates into the aqueous phase, the system rapidly separates into layers, and a rhodium-rich aqueous phase is obtained.

[0028] The beneficial effects of this invention are:

[0029] (1) This invention utilizes in-situ active chlorine in the aqueous phase in synergy with CO to achieve rapid and selective transfer of Rh from the organic phase to the aqueous phase under controlled acid, chlorine, and ORP conditions;

[0030] (2) The inherent safety and controllability of the process of this invention are enhanced: the active chlorine is not stored or transported over long distances in the form of exogenous chemicals, but originates from the chloride ions of the system itself, and uses ORP / available chlorine as an online signal, which makes it easy to achieve closed-loop control;

[0031] (3) This invention is selective and scale-up friendly, with rapid interfacial reaction, mild system emulsification, and short phase separation time, which significantly inhibits black colloids and insoluble phases; the transfer rate of Rh to the aqueous phase is high (≥95%), the organic phase and phosphine can be reused, the salt load and secondary pollution are reduced, and it has the replicability and continuous operation of cascade systems.

[0032] (4) The method of the present invention achieves economic and environmental synergy: This method can obtain a stable and treatable rhodium-rich aqueous phase, leaving enough room for subsequent use of conventional wet processes, while retaining the reuse potential of the organic phase; while achieving high recovery, high stability and low overall cost, it significantly reduces the intensity of hazardous sources and the risk of secondary pollution. Attached Figure Description

[0033] Figure 1 This is a process flow diagram of the present invention;

[0034] Figure 2 This is a schematic diagram of the structure of a two-phase oxidation transfer system. Detailed Implementation

[0035] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the content described.

[0036] Example 1: A method for the two-phase oxidation and transfer of rhodium from rhodium-containing organic wastewater to the aqueous phase (see...) Figure 1The present invention employs a two-phase oxidation transfer system, which includes a two-phase contact unit and an in-situ active chlorine electrolysis unit. The two-phase contact unit includes a mixing unit, a phase separation unit, an organic phase collection unit, and an aqueous phase product collection unit. The mixing unit has two series mixing stages. The inlet of the mixing unit is the first stage mixing unit. The outlet of the mixing unit is connected to the inlet of the phase separation unit. The organic phase outlet of the phase separation unit is connected to the inlet of the first stage mixing unit and the organic phase collection unit through a three-way pipe I. The inlet of the first stage mixing unit is connected to the outlet of the in-situ active chlorine electrolysis unit. The aqueous phase outlet of the phase separation unit is connected to the inlet of the aqueous phase product collection unit and the in-situ active chlorine electrolysis unit through a three-way pipe II.

[0037] The mixing unit is a two-stage stirred tank connected in series, and the phase separation unit is a gravity settler; the in-situ active chlorine electrolysis unit is a flow-through anode-cathode structure electrochemical workstation, with Ti / RuO2 as the anode, Ti as the cathode, Ag / AgCl as the reference electrode, and an electrode spacing of 1.0 mm.

[0038] The specific steps of the method are as follows:

[0039] (1) The rhodium-containing organic waste liquid is subjected to solid-liquid separation to remove solid impurities, then centrifuged and allowed to stand to remove the aqueous phase, and then diluted with a diluent (isooctane) to obtain the pretreated rhodium-containing organic waste liquid; the rhodium content in the pretreated rhodium-containing organic waste liquid is 512 mg / L;

[0040] (2) Prepare a chlorine-containing aqueous phase, wherein the chlorine-containing aqueous phase contains 6.0 mol / L hydrochloric acid and 1.0 mol / L soluble chloride (NaCl);

[0041] (3) The pretreated rhodium-containing organic waste liquid is placed in the first stage mixing unit of the two-phase contact unit, and the chlorine-containing aqueous phase is added to the in-situ active chlorine electrolysis unit for in-situ electrolysis to generate an active chlorine aqueous phase; with Ag / AgCl as the reference electrode, the redox potential of the in-situ electrolysis is 900mV, the aqueous phase linear velocity is 0.5m / s, and the current density is 120mA / cm. 2 The effective chlorine concentration in the aqueous phase, calculated as Cl2, was 1.5 mmol / L, and the ratio of free chloride ions to hydrogen ions was 0.17:1. Anodizing reduced the Cl2 concentration in the aqueous phase... - It is converted to Cl2(aq) and then reacts in acidic, high-Cl environments. - With water and Cl under ion concentration environment - The equilibrium produces Cl2(aq), HClO, and Cl3. - ;

[0042] Carbon monoxide (partial pressure 0.8 bar) and activated chlorine aqueous phase are introduced into the mixing unit of the two-phase contact unit and thoroughly mixed with the pretreated rhodium-containing organic waste liquid to carry out a multi-stage oxidation-transfer reaction to oxidize and transfer rhodium to the aqueous phase, resulting in an oxidation-transfer reaction mixture. The oxidation-transfer reaction mixture is then introduced into the phase separation unit and separated by gravity (standing for 8 min) to form a lower rhodium-containing aqueous phase and an upper organic phase. The volume ratio of the activated chlorine aqueous phase to the pretreated rhodium-containing organic waste liquid is 1:2, the oxidation-transfer reaction temperature is 50°C, and the single-stage oxidation-transfer reaction time is 10 min.

[0043] (4) When the rhodium content in the upper organic phase is greater than 0.005 g / L, the upper organic phase returns to the first-stage mixing unit through the three-way pipe I, and the lower rhodium-containing aqueous phase flows into the in-situ active chlorine electrolysis unit through the three-way pipe II to generate an active chlorine aqueous phase, which then flows into the first-stage mixing unit to achieve chlorine-containing aqueous phase circulation; when the rhodium content in the upper organic phase is less than or equal to 0.005 g / L, the upper organic phase, as a rhodium-poor organic phase, flows into the organic phase collection unit through the three-way pipe I; when the rhodium content in the lower rhodium-containing aqueous phase is not less than 2 g / L, the lower rhodium-containing aqueous phase flows into the organic phase collection unit as a rhodium-rich aqueous phase. The product flows into the aqueous phase collection unit through three-way pipe II. Phase separation analysis shows that the Rh concentration in the upper organic phase is approximately 0.0128 g / L, which is greater than 0.005 g / L. Therefore, the upper organic phase returns to the first-stage mixing unit for continued circulation through three-way pipe I. The Rh concentration in the lower rhodium-containing aqueous phase is approximately 0.998 g / L, which is less than 2 g / L. Therefore, the lower rhodium-containing aqueous phase flows into the in-situ active chlorine electrolysis unit through three-way pipe II for continued enrichment. In this embodiment, no visible black colloids were found in the lower rhodium-containing aqueous phase, and the rhodium transfer rate to the aqueous phase during a single two-phase oxidation transfer process was 97.5%.

[0044] Comparative Example 1: The difference between this comparative example and Example 1 is that carbon monoxide is not passed in step (3), the oxidation-transfer reaction mixture is passed into the phase separation unit and separated by gravity (the settling time is 25 min), and the number of times the rhodium in the rhodium-containing organic waste liquid is oxidized and transferred to the aqueous phase is the same.

[0045] Fine black colloids were visible in the rhodium-rich aqueous phase of this comparative example, and the rhodium transfer rate to the aqueous phase was 82%. This comparative example lacked the CO-co-oxidation-transfer process, which significantly reduced selectivity and slowed down phase separation.

[0046] Comparative Example 2: The difference between this comparative example and Example 1 is that: in the oxidation-transfer reaction process, sodium hypochlorite solution is directly added dropwise to the mixing unit; and this comparative example does not have an in-situ active chlorine electrolysis unit. The oxidation-transfer reaction mixture is passed into the phase separation unit and separated by gravity (standing for 40 min) into a lower rhodium-containing aqueous phase and an upper organic phase. The upper organic phase is returned to the mixing unit, and the lower rhodium-containing aqueous phase flows back to the mixing unit; the number of times rhodium in the rhodium-containing organic waste liquid is oxidized and transferred to the aqueous phase is the same in this comparative example.

[0047] In this comparative example, the organic phase showed a deeper color and significant emulsification, with only 76% rhodium transfer to the aqueous phase, indicating that the addition of an external oxidant in situ is not conducive to selectivity and continuity.

[0048] Example 2: A method for the two-phase oxidation and transfer of rhodium from rhodium-containing organic wastewater to the aqueous phase (see...) Figure 1 The present invention employs a two-phase oxidation transfer system, which includes a two-phase contact unit and an in-situ active chlorine electrolysis unit. The two-phase contact unit includes a mixing unit, a phase separation unit, an organic phase collection unit, and an aqueous phase product collection unit. The mixing unit has two series mixing stages. The inlet of the mixing unit is the first stage mixing unit. The outlet of the mixing unit is connected to the inlet of the phase separation unit. The organic phase outlet of the phase separation unit is connected to the inlet of the first stage mixing unit and the organic phase collection unit through a three-way pipe I. The inlet of the first stage mixing unit is connected to the outlet of the in-situ active chlorine electrolysis unit. The aqueous phase outlet of the phase separation unit is connected to the inlet of the aqueous phase product collection unit and the in-situ active chlorine electrolysis unit through a three-way pipe II.

[0049] The mixing unit is a four-stage stirred tank connected in series, and the phase separation unit is a gravity settler; the in-situ active chlorine electrolysis unit is a flow-through anode-cathode structure electrochemical workstation, with Ti / RuO2 as the anode, Ti as the cathode, Ag / AgCl as the reference electrode, and an electrode spacing of 1.5 mm.

[0050] The specific steps of the method are as follows:

[0051] (1) The rhodium-containing organic waste liquid is subjected to solid-liquid separation to remove solid impurities, then centrifuged and allowed to stand to remove the aqueous phase, and then diluted with a diluent (a mixed organic solvent of toluene, methyl isobutyl ketone and ethyl acetate in a volume ratio of 1:1:1) to obtain the pretreated rhodium-containing organic waste liquid; the rhodium content in the pretreated rhodium-containing organic waste liquid is 2967 mg / L;

[0052] (2) Prepare a chlorine-containing aqueous phase, wherein the chlorine-containing aqueous phase contains 8.0 mol / L hydrochloric acid and 1.0 mol / L soluble chloride (KCl);

[0053] (3) The pretreated rhodium-containing organic waste liquid is placed in the first stage mixing unit of the two-phase contact unit, and the chlorine-containing aqueous phase is added to the in-situ active chlorine electrolysis unit for in-situ electrolysis to generate an active chlorine aqueous phase; with Ag / AgCl as the reference electrode, the redox potential of the in-situ electrolysis is 950mV, the aqueous phase linear velocity is 0.8m / s, and the current density is 180mA / cm. 2 The effective chlorine concentration in the aqueous phase, calculated as Cl2, was 3.0 mmol / L, and the ratio of free chloride ions to hydrogen ions was 0.25:1. Anodizing reduced the Cl2 concentration in the aqueous phase... - It is converted to Cl2(aq) and then reacts in acidic, high-Cl environments.- With water and Cl under ion concentration environment - The equilibrium produces Cl2(aq), HClO, and Cl3. - ;

[0054] Carbon monoxide (partial pressure 2.0 bar) and activated chlorine aqueous phase are introduced into the mixing unit of the two-phase contact unit and thoroughly mixed with the pretreated rhodium-containing organic waste liquid to carry out a multi-stage oxidation-transfer reaction to oxidize and transfer rhodium to the aqueous phase, resulting in an oxidation-transfer reaction mixture. The oxidation-transfer reaction mixture is then introduced into the phase separation unit and separated by gravity (standing for 10 min) to form a lower rhodium-containing aqueous phase and an upper organic phase. The volume ratio of the activated chlorine aqueous phase to the pretreated rhodium-containing organic waste liquid is 1:1, the oxidation-transfer reaction temperature is 80℃, and the single-stage oxidation-transfer reaction time is 15 min.

[0055] (4) When the rhodium content in the upper organic phase is greater than 0.005 g / L, the upper organic phase returns to the first-stage mixing unit through the three-way pipe I, and the lower rhodium-containing aqueous phase flows into the in-situ active chlorine electrolysis unit through the three-way pipe II to generate an active chlorine aqueous phase, which then flows into the first-stage mixing unit to achieve chlorine-containing aqueous phase circulation; when the rhodium content in the upper organic phase is less than or equal to 0.005 g / L, the upper organic phase, as a rhodium-poor organic phase, flows into the organic phase collection unit through the three-way pipe I; when the rhodium content in the lower rhodium-containing aqueous phase is not less than 2 g / L, the lower rhodium-containing aqueous phase... The rhodium-rich aqueous phase flows into the aqueous product collection unit through three-way pipe II. Phase separation analysis shows that the Rh concentration in the upper organic phase is approximately 0.0178 g / L, which is greater than 0.005 g / L. Therefore, the upper organic phase returns to the first-stage mixing unit for continued circulation through three-way pipe I. The Rh concentration in the lower rhodium-containing aqueous phase is approximately 2.95 g / L, which is above 2 g / L. Therefore, the lower rhodium-containing aqueous phase, as the rhodium-rich aqueous phase, flows into the aqueous product collection unit through three-way pipe II. In this embodiment, the rhodium-rich aqueous phase contains no visible black colloids, and the rhodium transfer rate to the aqueous phase is 99.4%.

[0056] Example 3: A method for the two-phase oxidation and transfer of rhodium from rhodium-containing organic wastewater to the aqueous phase (see Example 3). Figure 1 The present invention employs a two-phase oxidation transfer system, which includes a two-phase contact unit and an in-situ active chlorine electrolysis unit. The two-phase contact unit includes a mixing unit, a phase separation unit, an organic phase collection unit, and an aqueous phase product collection unit. The mixing unit has two series mixing stages. The inlet of the mixing unit is the first stage mixing unit. The outlet of the mixing unit is connected to the inlet of the phase separation unit. The organic phase outlet of the phase separation unit is connected to the inlet of the first stage mixing unit and the organic phase collection unit through a three-way pipe I. The inlet of the first stage mixing unit is connected to the outlet of the in-situ active chlorine electrolysis unit. The aqueous phase outlet of the phase separation unit is connected to the inlet of the aqueous phase product collection unit and the in-situ active chlorine electrolysis unit through a three-way pipe II.

[0057] The mixing unit is a single-stage stirred tank, and the phase separation unit is a gravity settler; the in-situ active chlorine electrolysis unit is a flow-through anode-cathode structure electrochemical workstation, with Ti / RuO2 as the anode, Ti as the cathode, Ag / AgCl as the reference electrode, and an electrode spacing of 0.8 mm.

[0058] The specific steps of the method are as follows:

[0059] (1) The rhodium-containing organic waste liquid is subjected to solid-liquid separation to remove solid impurities, then centrifuged and allowed to stand to remove the aqueous phase, and then diluted with a diluent (toluene) to obtain the pretreated rhodium-containing organic waste liquid; the rhodium content in the pretreated rhodium-containing organic waste liquid is 132 mg / L;

[0060] (2) Prepare a chlorine-containing aqueous phase, wherein the chlorine-containing aqueous phase contains 4.0 mol / L hydrochloric acid and 0.5 mol / L soluble chloride (LiCl);

[0061] (3) The pretreated rhodium-containing organic waste liquid is placed in the mixing unit of the two-phase contact unit, and the chlorine-containing aqueous phase is added to the in-situ active chlorine electrolysis unit for in-situ electrolysis to generate an active chlorine aqueous phase; with Ag / AgCl as the reference electrode, the redox potential of the in-situ electrolysis is 600mV, the aqueous phase linear velocity is 0.2m / s, and the current density is 50mA / cm. 2 The effective chlorine concentration in the aqueous phase, calculated as Cl2, is 0.5 mmol / L, and the ratio of free chloride ions to hydrogen ions is 0.1:1. Anodizing reduces the Cl2 concentration in the aqueous phase. - It is converted to Cl2(aq) and then reacts in acidic, high-Cl environments. - With water and Cl under ion concentration environment - The equilibrium produces Cl2(aq), HClO, and Cl3. - ;

[0062] Carbon monoxide (partial pressure 0.3 bar) and activated chlorine aqueous phase are introduced into the mixing unit of the two-phase contact unit and thoroughly mixed with the pretreated rhodium-containing organic waste liquid to carry out a multi-stage oxidation-transfer reaction to oxidize and transfer rhodium to the aqueous phase, resulting in an oxidation-transfer reaction mixture. The oxidation-transfer reaction mixture is then introduced into the phase separation unit and separated by gravity (standing for 2 minutes) to form a lower rhodium-containing aqueous phase and an upper organic phase. The volume ratio of the activated chlorine aqueous phase to the pretreated rhodium-containing organic waste liquid is 1:5, the oxidation-transfer reaction temperature is 35°C, and the single-stage oxidation-transfer reaction time is 5 minutes.

[0063] (4) When the rhodium content in the upper organic phase is greater than 0.005 g / L, the upper organic phase returns to the first-stage mixing unit through the three-way pipe I, and the lower rhodium-containing aqueous phase flows into the in-situ active chlorine electrolysis unit through the three-way pipe II to generate an active chlorine aqueous phase, which then flows into the first-stage mixing unit to achieve chlorine-containing aqueous phase circulation; when the rhodium content in the upper organic phase is less than or equal to 0.005 g / L, the upper organic phase flows into the organic phase collection unit as a rhodium-poor organic phase through the three-way pipe I; when the rhodium content in the lower rhodium-containing aqueous phase is not less than 2 g / L, the lower rhodium-containing aqueous phase flows into the aqueous phase product collection unit as a rhodium-rich aqueous phase through the three-way pipe II.

[0064] Phase separation analysis showed that the Rh concentration in the upper organic phase was approximately 0.0065 g / L, which is greater than 0.005 g / L. Therefore, the upper organic phase was returned to the first-stage mixing unit for continued circulation through the three-way pipe I. The Rh concentration in the lower rhodium-containing aqueous phase was approximately 0.627 g / L, which is less than 2 g / L. Therefore, the lower rhodium-containing aqueous phase flowed into the in-situ active chlorine electrolysis unit for continued circulation and enrichment through the three-way pipe II. In this embodiment, there was no visible black colloid in the lower rhodium-containing aqueous phase, and the rhodium transfer rate to the aqueous phase during a single two-phase oxidation transfer process was 95.1%.

[0065] The specific embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for the two-phase oxidation and transfer of rhodium from rhodium-containing organic wastewater to the aqueous phase, characterized in that, A two-phase oxidation transfer system is adopted, which includes a two-phase contact unit and an in-situ active chlorine electrolysis unit. The two-phase contact unit includes a mixing unit, a phase separation unit, an organic phase collection unit, and an aqueous phase product collection unit. The mixing unit has 1 to 4 mixing stages in series. The inlet of the mixing unit is the first stage mixing unit. The outlet of the mixing unit is connected to the inlet of the phase separation unit. The organic phase outlet of the phase separation unit is connected to the inlet of the first stage mixing unit and the organic phase collection unit through a three-way pipe I. The inlet of the first stage mixing unit is connected to the outlet of the in-situ active chlorine electrolysis unit. The aqueous phase outlet of the phase separation unit is connected to the inlet of the aqueous phase product collection unit and the in-situ active chlorine electrolysis unit through a three-way pipe II. The specific steps are as follows: (1) The rhodium-containing organic waste liquid is subjected to solid-liquid separation to remove solid impurities, then centrifuged and allowed to stand to remove the aqueous phase, and then diluted with a diluent to obtain the pretreated rhodium-containing organic waste liquid; (2) Prepare a chlorine-containing aqueous phase, wherein the chlorine-containing aqueous phase contains hydrochloric acid and soluble chloride; (3) The pretreated rhodium-containing organic waste liquid is placed in the first mixing unit of the two-phase contact unit. The chlorine-containing aqueous phase is added to the in-situ active chlorine electrolysis unit to generate an active chlorine aqueous phase. Carbon monoxide and the active chlorine aqueous phase are introduced into the mixing unit of the two-phase contact unit and fully mixed with the pretreated rhodium-containing organic waste liquid to carry out multi-stage oxidation-transfer reaction in sequence so that rhodium is oxidized and transferred to the aqueous phase to obtain an oxidation-transfer reaction mixture. The oxidation-transfer reaction mixture is introduced into the phase separation unit and separated by gravity into a lower rhodium-containing aqueous phase and an upper organic phase. (4) When the rhodium content in the upper organic phase is greater than 0.005 g / L, the upper organic phase returns to the first-stage mixing unit through the three-way pipe I, and the lower rhodium-containing aqueous phase flows into the in-situ active chlorine electrolysis unit through the three-way pipe II to generate an active chlorine aqueous phase, which then flows into the first-stage mixing unit to achieve chlorine-containing aqueous phase circulation; when the rhodium content in the upper organic phase is less than or equal to 0.005 g / L, the upper organic phase flows into the organic phase collection unit as a rhodium-poor organic phase through the three-way pipe I; when the rhodium content in the lower rhodium-containing aqueous phase is not less than 2 g / L, the lower rhodium-containing aqueous phase flows into the aqueous phase product collection unit as a rhodium-rich aqueous phase through the three-way pipe II.

2. The method for transferring rhodium from rhodium-containing organic waste liquid to the aqueous phase via two-phase oxidation according to claim 1, characterized in that: Step (1) The diluent is one or more of isooctane, toluene, methyl isobutyl ketone, and ethyl acetate.

3. The method for transferring rhodium from rhodium-containing organic wastewater to the aqueous phase via two-phase oxidation according to claim 1, characterized in that: Step (1) Pre-treat the rhodium-containing organic waste liquid with a rhodium content of 100~3000 mg / L.

4. The method for transferring rhodium from rhodium-containing organic wastewater to the aqueous phase via two-phase oxidation according to claim 1, characterized in that: In step (2), the concentration of hydrochloric acid in the chlorine-containing aqueous phase is 4~8 mol / L, and the concentration of soluble chloride is 0.5~2.0 mol / L.

5. The method for transferring rhodium from rhodium-containing organic waste liquid to the aqueous phase according to claim 4, characterized in that: Step (2) The chloride is one or more of NaCl, KCl, LiCl, MgCl2, CaCl2, and NH4Cl.

6. The method for transferring rhodium from rhodium-containing organic waste liquid to the aqueous phase via two-phase oxidation according to claim 1, characterized in that: Using Ag / AgCl as the reference electrode, the redox potential of the in-situ electrolysis in step (3) is 600~950mV, the effective chlorine in the active chlorine aqueous phase is 0.5~3mmol / L based on Cl2, and the concentration ratio of free chloride ions to hydrogen ions is 0.1~1.0:

1.

7. The method for transferring rhodium from rhodium-containing organic waste liquid to the aqueous phase via two-phase oxidation according to claim 1, characterized in that: In step (3), the volume ratio of the active chlorine aqueous phase to the pretreated rhodium-containing organic waste liquid is 1:1~5, the oxidation-transfer reaction temperature is 35~80℃, and the single-stage oxidation-transfer reaction time is 5~15 min.

8. The method for transferring rhodium from rhodium-containing organic waste liquid to the aqueous phase via two-phase oxidation according to claim 1, characterized in that: Step (3) The partial pressure of carbon monoxide gas is 0.3~2.0 bar.

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