A method for wet extraction of mercury sulfide based on composite leaching and adsorption of modified resin

Abstract

The present application belongs to the technical field of metallurgical engineering, and mainly relates to a method for wet mercury extraction from cinnabar based on composite leaching and modified resin adsorption. The method comprises the following steps: adding cinnabar concentrate into dilute sulfuric acid, filtering the impurity-removed cinnabar after stirring and reaction; mixing the impurity-removed cinnabar with a composite leaching solution, and stirring and leaching to obtain a mercury-containing complex solution; the composite leaching solution is a mixed solution of a complexing agent and ferric sulfate; after the mercury-containing complex solution is adsorbed by a modified thiourea type chelating resin, a mercury-containing desorption solution is obtained by desorption, and the mercury-containing desorption solution is subjected to electrolytic deposition to obtain metallic mercury. The method realizes efficient extraction of cinnabar reselected and flotation concentrate, recycling of waste water and harmless utilization of solid waste, and has significant advantages in leaching efficiency, environmental protection and raw material adaptability, and has broad industrial application prospects.

Description

Technical Field

[0001] This invention relates to the interdisciplinary fields of metallurgical engineering, mineral processing and environmental engineering, and mainly to a method for wet mercury extraction from mercury sulfide based on composite leaching and modified resin adsorption. Background Technology

[0002] Mercury, a common metal, has a wide range of applications, such as the extraction of non-ferrous metals and its use in the electrical and instrument industries, chemical industries, and pharmaceutical industries. Elemental mercury is mainly derived from the smelting of mercury sulfide ores; currently, there are two processes for smelting mercury sulfide ores: pyrometallurgical and hydrometallurgical processes.

[0003] Pyrometallurgical mercury refining includes processes such as roasting or distillation of ore or concentrate, dust removal and condensation of mercury-containing flue gas, mercury soot treatment, and crude mercury purification. However, this process generates large amounts of mercury-containing waste gas and SO2, severely polluting the environment, and is energy-intensive and faces significant environmental pressure. Hydrometallurgical mercury refining includes processes such as ore leaching, leachate purification, and electrolysis or displacement. Hydrometallurgical processes have two major bottlenecks: firstly, the complexation system is singular, mainly using a sodium thiosulfate leaching system, which cannot effectively suppress Hg in the leachate. 2+ Re-precipitation limits the leaching rate; secondly, recycling and circulation are disconnected, with solid waste (leaching tailings) emissions ≥ 0.15 t / t of ore and wastewater recycling rate < 60%, making it difficult to achieve large-scale environmentally friendly production.

[0004] To overcome these challenges, it is urgent to develop a highly efficient, closed-loop, wet mercury extraction process using mercury sulfide. Summary of the Invention

[0005] To overcome the technical problems of mercury extraction from existing mercury sulfide ores, this invention provides a highly efficient complexing and closed-loop recycling wet mercury extraction process from mercury sulfide ores, achieving efficient mercury extraction and harmless recycling of wastewater and tailings. This solves the problems of low leaching rate, low wastewater recycling rate, and difficult tailings treatment in existing wet mercury extraction processes.

[0006] This invention provides a method for wet mercury extraction from mercury sulfide based on composite leaching and modified resin adsorption, the method comprising the following steps: S1. Add mercuric sulfide concentrate to dilute sulfuric acid, stir and react, then filter to obtain purified mercuric sulfide. S2. Mix the purified mercuric sulfide with the composite leaching solution and stir to leach to obtain a mercury-containing complex solution; the composite leaching solution is a mixed solution of complexing agent and ferric sulfate; S3. The mercury-containing complex solution is adsorbed by a modified thiourea chelating resin, then desorbed to obtain a mercury-containing desorbed solution, and the mercury-containing desorbed solution is electrolytically deposited to obtain metallic mercury.

[0007] As an optional implementation, in step S1, the concentration of dilute sulfuric acid is 0.4~0.6 mol / L, the liquid-to-solid ratio is 1g:3.5~4.5mL, and the stirring time is 25~35 min.

[0008] As an optional implementation, the complexing agent in the composite leachate includes sodium thiosulfate and citric acid, wherein the concentration of sodium thiosulfate is 0.6~1.0 mol / L, the concentration of citric acid is 0.2~0.4 mol / L, the concentration of ferric sulfate is 0.04~0.06 mol / L, and the solid-liquid ratio of the depurified mercuric sulfide and the composite leachate is 1g:5.5~6.5mL.

[0009] As an optional implementation, in step S2, the stirring leaching temperature is 50~80 ℃, the solution pH is 4~6, the stirring speed is 300~500 rpm, and the stirring time is 100~140 min.

[0010] As an optional implementation, in step S3, the modified thiourea chelating resin is prepared by reacting D401 macroporous resin with 1.0-1.2 mol / L thiourea solution at 45-55°C for 3-4 h; adding aminotrimethylenephosphonic acid and continuing the reaction at a constant temperature for 1-2 h.

[0011] As an optional implementation, in step S3, the flow rate of the mercury-containing complex solution during the adsorption process is 1.5~4 BV / h; the desorption process is carried out using a mixed solution of hydrochloric acid and thiourea, and the flow rate is controlled at 2~4 BV / h.

[0012] As an optional implementation, in step S3, the cathode in the electrolytic deposition is a titanium-palladium coated electrode, the anode is a high-purity graphite electrode, and the electrolysis conditions are a current density of 180~220 A / m², a temperature of 35~45 ℃, and a time of 60~80 min.

[0013] As an optional implementation, step S2 further includes a secondary leaching, comprising: The leaching residue obtained in step S2 is mixed with the composite leaching solution, and a sodium thiosulfate-citric acid mixture is added. The molar ratio of sodium thiosulfate to citric acid in the mixture is 2.0~3.0:1, and the leaching time is 60~70 min.

[0014] As an optional implementation, the method further includes: The filtrate filtered in step S1 is neutralized with lime and filtered again, and the filtrate is returned to S1. The wastewater adsorbed by the modified resin in step S3 is returned to step S2 after aeration oxidation, supplementation with ferric sulfate and complexing agent.

[0015] As an optional implementation, the aeration intensity of the aeration oxidation is 0.5~0.8 m³ / (m²·h).

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) This invention employs a combination of methods, including composite leaching, modified resin adsorption, and electrolytic deposition, to extract mercury. First, a ternary composite leaching system composed of ferric sulfate, sodium thiosulfate, and citric acid is used. Compared to the traditional single sodium thiosulfate system, this system increases the leaching rate by 8-10% and effectively inhibits HgS redeposition. The leaching solution contains [Hg(C6H5O7)(S2O3)] 3- The proportion reached over 92%; among them, the synergistic leaching principle of the ternary composite leaching system is as follows: ① Sodium thiosulfate as the main complexing agent: reacts with HgS to produce Hg 2+ [Hg(S2O3)2] is formed. 3- Complexes disrupt the dissolution equilibrium of HgS, thereby achieving Hg 2+ Released from the mineral lattice; ② Citric acid, an auxiliary complexing agent: reacts with Hg via the carboxyl group. 2+ Coordination occurs, forming a more stable [Hg(C6H5O7)(S2O3)] 3- Ternary complexes significantly reduce Hg 2+ Activity, inhibiting HgS redeposition; ③ Oxidizing agent ferric sulfate: Fe 3+ S in HgS can be oxidized 2- The presence of elemental S further promotes the dissolution of HgS, and the resulting Fe... 2+ It can be regenerated into Fe through subsequent aeration and oxidation. 3+ The resin can be recycled. Secondly, the modified thiourea resin uses aminotrimethylenephosphonic acid (ATMP) to crosslink and modify the thiourea chelating resin. The thiourea loading reaches 1.5~1.6 mmol / g, and the adsorption rate reaches 99.2%, which is more than 7% higher than the unmodified resin. Moreover, the adsorption rate is still above 97% after 80 cycles of recycling.

[0017] (2) The present invention also adopts a closed-loop recycling system throughout the entire process. By treating the filtrate, waste liquid, leaching residue and other materials in each step through appropriate methods and returning them to each step or building materials, the wastewater recycling rate of more than 92% is achieved, and the solid waste is rendered harmless and recycled. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 The process flow diagram of the wet mercury extraction method based on composite leaching and modified resin adsorption provided in the embodiments of the present invention is shown. Detailed Implementation

[0020] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0021] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0022] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0023] like Figure 1 As shown, this invention provides a method for wet mercury extraction from mercury sulfide based on composite leaching and modified resin adsorption, comprising the following steps: S1. Pretreatment Process: This invention uses mercuric sulfide concentrate and mercuric sulfide flotation concentrate as raw materials. It should be understood that, in order to improve the leaching effect, the mercuric sulfide concentrate is dried, crushed, and sieved before wet leaching to remove excess water, ensuring that the crushed material can fully contact the reagent. The crushed and sieved mercuric sulfide concentrate is added to dilute sulfuric acid with a concentration of 0.4~0.6mol / L, with a solid-liquid ratio of 1g:3.5~4.5mL, and stirred at room temperature for 25~35 min. Soluble impurities are removed by filtration to obtain purified mercuric sulfide (also known as purified cinnabar) and filtrate. The filtrate is neutralized with lime and then filtered again before being added to the pretreatment process.

[0024] S2. Composite Leaching Process: Prepare a composite leaching solution with the following concentrations of raw materials: sodium thiosulfate (main complexing agent) at 0.6–1.0 mol / L, citric acid (auxiliary complexing agent) at 0.2–0.4 mol / L, and ferric sulfate (oxidant) at 0.04–0.06 mol / L. Mix the purified mercuric sulfide and the composite leaching solution at a solid-liquid ratio of 1 g: 5.5–6.5 mL. Leach at a temperature of 50–80 °C, a pH of 4–6, and a stirring rate of 300–500 rpm for 100–140 min. After leaching, filter to obtain a mercury-containing complex solution and leaching tailings. To improve leaching, the leaching tailings can be subjected to a secondary leaching process. The leaching tailings are mixed with a composite leachate, and a sodium thiosulfate-citric acid mixture is added, wherein the molar ratio of sodium thiosulfate to citric acid in the mixture is 2.0~3.0:1, and the leaching time is 60~70 minutes. The tailings are obtained by filtration again. After neutralization with lime, the tailings are ball-milled and can be used as a building additive.

[0025] S3. Mercury Recovery: Preparation of Modified Resin: D401 macroporous resin was reacted with 1.0-1.2 mol / L thiourea solution at 45-55℃ for 3-4 h; aminotrimethylenephosphonic acid was added, and the reaction was continued at a constant temperature for 1-2 h to obtain modified thiourea chelating resin; the mercury-containing complex solution was passed through the modified thiourea chelating resin at a flow rate of 1.5-4 BV / h. After adsorption, a mixture of 0.2 mol / L hydrochloric acid and 0.02 mol / L thiourea was introduced into the saturated resin column, and the flow rate was controlled at 2-4 BV / h to desorb mercury-containing desorbate. The desorbate was transferred to an electrolytic cell. The cathode in the electrolytic deposition was a titanium-palladium coated electrode, and the anode was a high-purity graphite electrode. 0.5 mol / L sulfuric acid was added to adjust the conductivity to 10 mS / cm. Electrolysis was carried out at a current density of 180-220 A / m² and a temperature of 35-45℃ for 60-80 min to obtain metallic mercury. In this process, the wastewater after resin adsorption is aerated and oxidized, and supplemented with ferric sulfate and complexing agent as part of the composite leaching agent and returned to step S2.

[0026] The embodiments of this application will be described in detail below. These embodiments are implemented based on the technical solution of this application, and detailed implementation methods and specific operation processes are given. However, the protection scope of this application is not limited to the following embodiments.

[0027] The raw material compositions of the high-grade mercuric sulfide concentrate (gravity separation product of a certain cinnabar mine) and the low-grade mercuric sulfide flotation concentrate (flotation product of the above concentrate) used in the various embodiments and comparative examples of the present invention are shown in Table 1.

[0028] Table 1 Experimental materials and component content Example 1: S1. Pretreatment of gravity concentrate: 3000g of mercuric sulfide gravity concentrate was added to a stirred tank, and 12L of 0.5mol / L dilute sulfuric acid was added at a liquid-to-solid ratio of 4:1. The mixture was stirred at room temperature for 30min, aerated to remove H2S, and filtered to obtain purified mercuric sulfide. The pretreatment filtrate was neutralized to pH 7.5 with lime, filtered to remove CaSO4 precipitate, and the neutralized filtrate was reused in the S1 pretreatment process, with a reuse rate of 94.7%.

[0029] S2. Mercury Leaching: Removed mercuric sulfide was added to a double-chamber reactor, and a composite leaching solution (21.6 L: 0.8 mol / L sodium thiosulfate + 0.3 mol / L citric acid + 0.05 mol / L ferric sulfate) was added at a solid-liquid ratio of 1 g: 6 mL. The temperature was controlled at 60℃, pH 5, and stirring speed at 300 rpm for 120 min, yielding a mercury-containing complex solution and leaching tailings. Testing of the mercury-containing complex solution showed a single-pass leaching rate of 96.5%. The leaching tailings were mixed with lime neutralization residue at a ratio of 1:0.4 and ball-milled to 200 mesh to obtain a building material additive. Testing showed a 7-day compressive strength of 16.2 MPa and a mercury leaching toxicity of 0.04 mg / L, achieving both harmless treatment and resource utilization of solid waste.

[0030] S3. Mercury Recovery: Modification Process: D401 resin (50L resin loading) was reacted with 1.2 mol / L thiourea solution at 50℃ for 3.5 h. 2.5% (by weight) of ATMP crosslinking agent was added, and the reaction continued for another 1.5 h, resulting in a thiourea loading of 1.6 mmol / g. The mercury-containing complex solution was passed through the modified resin at a flow rate of 2.0 BV / h. After adsorption, a sample was taken, and the mercury concentration in the post-adsorption solution was approximately 0.87 g / L, with an adsorption rate of 99.2%. Then, a mixture of 0.2 mol / L hydrochloric acid and 0.02 mol / L thiourea was introduced into the saturated resin column for desorption at a controlled flow rate of 3.0 BV / h. The combined desorption results showed a mercury concentration of approximately 640.3 g / L, with a desorption rate of 98.5%. The desorbed solution was transferred to an electrolytic cell, and 0.5 mol / L sulfuric acid was added to adjust the conductivity to 10 mS / cm. The desorbed solution was electrolyzed at a current density of 200 A / m² and 40℃ for 60 min, yielding 2329 g of metallic mercury with a purity of 99.99%, representing a total recovery rate of 94.9%. After resin adsorption, the wastewater was aerated for oxidation at an aeration intensity of 0.7 m³ / min. 3 / (m 2 ·h), after oxidizing for 2h, Fe 2+ Oxidation rate 98.5%. After adding 10% of the consumed ferric sulfate and sodium thiosulfate-citric acid mixture to the oxidized wastewater, it is reused in S2.

[0031] Example 2 S1. Pretreatment of Flotation Concentrate: 3000g of flotation concentrate was added to a stirred tank, and 13.5L of 0.6mol / L dilute sulfuric acid was added at a liquid-to-solid ratio of 4.5:1. The mixture was stirred at room temperature for 35 minutes, aerated to remove H2S, and filtered to obtain purified mercuric sulfide. The pretreatment filtrate was neutralized to pH 7.5 with lime, filtered to remove CaSO4 precipitate, and the neutralized filtrate was reused in the S1 pretreatment process, with a reuse rate of 93%.

[0032] S2. Leaching: The purified mercuric sulfide was added to a double-chamber reactor, and a composite leaching solution (21.6 L: 1.0 mol / L sodium thiosulfate + 0.4 mol / L citric acid + 0.06 mol / L ferric sulfate) was added at a solid-liquid ratio of 1 g: 6 mL. Leaching was carried out at 80℃, pH 6, and a stirring rate of 500 rpm for 100 min, yielding a mercury-containing complex solution and leaching tailings. Samples were taken to determine the mercury concentration in the leaching solution, and the single-pass leaching rate was calculated to be 93.3%.

[0033] S2' Secondary Leaching: After the first leaching of S2, the leachate is not discharged. 20% of the volume of a ligand mixture (4.32 L) is added to the reactor. The mixture consists of sodium thiosulfate and citric acid, with a molar ratio of 2.5:1 and concentrations of 1.0 mol / L and 0.4 mol / L, respectively. The temperature is maintained at 80℃, pH 6, and stirring speed at 500 rpm for 60 minutes. After leaching, a sample is taken to test the total mercury concentration in the leachate, and the total leaching rate is calculated to be 97.1%. The tailings after leaching are mixed with lime neutralization residue at a ratio of 1:0.4 and ball-milled to 200 mesh to obtain a building material additive. Tests show that its 7-day compressive strength is 17.5 MPa and its mercury leaching toxicity is 0.03 mg / L, achieving the harmless treatment and resource utilization of solid waste.

[0034] S3. Mercury Recovery: Modification Process: D401 resin (50L resin loading) was reacted with 1.2 mol / L thiourea solution at 50℃ for 3.5 h. 2.5% (by weight) of ATMP crosslinking agent was added, and the reaction continued for another 1.5 h, resulting in a thiourea loading of 1.6 mmol / g. The mercury-containing complex solution was passed through the modified resin at a flow rate of 2.0 BV / h. After adsorption, a sample was taken, and the mercury concentration in the post-adsorption solution was ≤0.39 g / L, with an adsorption rate of 99.3%. Then, a mixture of 0.2 mol / L hydrochloric acid and 0.02 mol / L thiourea was introduced into the saturated resin column for desorption at a controlled flow rate of 3.0 BV / h. The combined mercury concentration was approximately 447.6 g / L, with a desorption rate of 98.5%. The desorbed solution was transferred to an electrolytic cell, and 0.5 mol / L sulfuric acid was added to adjust the conductivity to 10 mS / cm. The desorbed solution was electrolyzed at a current density of 200 A / m² and 40℃ for 60 min, yielding 720 g of metallic mercury with a purity of 99.99%, representing a total recovery rate of 94.5%. After resin adsorption, the wastewater was aerated for oxidation at an aeration intensity of 0.7 m³ / min. 3 / (m 2·h), after oxidizing for 2h, Fe 2+ Oxidation rate: 98.8%. After adding 10% of the consumed ferric sulfate and sodium thiosulfate-citric acid mixture to the oxidized wastewater, it was reused in S2, with a reuse rate of 93%.

[0035] Example 3 S1. Pretreatment of gravity concentrate: 3000g of mercuric sulfide gravity concentrate was added to a stirred tank, and 10.5L of 0.4mol / L dilute sulfuric acid was added at a liquid-to-solid ratio of 3.5:1. The mixture was stirred at room temperature for 25min, aerated to remove H2S, and filtered to obtain purified mercuric sulfide. The pretreatment filtrate was neutralized to pH 7.5 with lime, filtered to remove CaSO4 precipitate, and the neutralized filtrate was reused in the S1 pretreatment process with a reuse rate of 95.0%.

[0036] S2. Mercury Leaching: Depurified mercuric sulfide was added to a double-chamber reactor, and a composite leaching solution (21.6 L: 0.6 mol / L sodium thiosulfate + 0.2 mol / L citric acid + 0.04 mol / L ferric sulfate) was added at a solid-liquid ratio of 1 g: 6 mL. The temperature was controlled at 50℃, pH 4, and stirring speed at 300 rpm for 140 min, yielding a mercury-containing complex solution and leaching tailings. Testing of the mercury-containing complex solution showed a single-pass leaching rate of 93.5%. The leaching tailings were mixed with lime neutralization residue at a ratio of 1:0.5 and ball-milled to 200 mesh to obtain a building material additive. Testing showed its 7-day compressive strength was 15.8 MPa, and its mercury leaching toxicity was 0.045 mg / L. This achieves the harmless treatment and resource utilization of solid waste.

[0037] S3. Mercury Recovery: Modification Process: D401 resin (50L resin loading) was reacted with 1.0 mol / L thiourea solution at 50℃ for 3 h. 2.0% (by weight) of ATMP crosslinking agent was added, and the reaction continued for 1.5 h, resulting in a thiourea loading of 1.5 mmol / g. The mercury-containing complex solution was passed through the modified resin at a flow rate of 2.0 BV / h. After adsorption, a sample was taken, and the mercury concentration in the post-adsorption solution was ≤1.03 g / L, with an adsorption rate of 99.0%. Then, a mixture of 0.2 mol / L hydrochloric acid and 0.02 mol / L sodium thiosulfate was introduced into the saturated resin column for desorption at a controlled flow rate of 3.0 BV / h. The combined desorption results showed a mercury concentration of approximately 632.1 g / L, with a desorption rate of 98.5%. The desorbed solution was transferred to an electrolytic cell, and 0.5 mol / L sulfuric acid was added to adjust the conductivity to 9 mS / cm. The desorbed solution was electrolyzed at a current density of 200 A / m² and 35 °C for 70 min, yielding 2236 g of metallic mercury with a purity of 99.99%, representing a total recovery rate of 91.1%. After resin adsorption, the wastewater was aerated for oxidation at an aeration intensity of 0.6 m³ / min. 3 / (m 2 ·h), after oxidation for 2.5h, Fe 2+The oxidation rate was 97.8%. After adding 10% of the consumed ferric sulfate and sodium thiosulfate-citric acid mixture to the oxidized wastewater, it was reused in S2, with a reuse rate of 92.0%.

[0038] Comparative Example 1 S1. Pretreatment of gravity concentrate: 3000g of mercuric sulfide gravity concentrate was added to a stirred tank, and 12L of 0.5mol / L dilute sulfuric acid was added at a liquid-to-solid ratio of 4:1. The mixture was stirred at room temperature for 30min, aerated to remove H2S, and filtered to obtain purified mercuric sulfide. The pretreatment filtrate was neutralized to pH 7.5 with lime, filtered to remove CaSO4 precipitate, and the neutralized filtrate was reused in the S1 pretreatment process, with a reuse rate of 93.9%.

[0039] S2. Mercury Leaching: Removed mercuric sulfide was added to a double-chamber reactor, and 21.6 L of 1 mol / L sodium thiosulfate leaching solution was added at a solid-liquid ratio of 1 g: 6 mL. The temperature was controlled at 60℃, pH 5, and stirring speed at 300 rpm for 120 min, yielding a mercury-containing complex solution and leaching tailings. Testing of the mercury-containing complex solution showed a single-pass leaching rate of 87.2%. The leaching tailings were mixed with lime neutralization residue at a ratio of 1:0.4 and ball-milled to 200 mesh to obtain a building material additive. Testing showed a 7-day compressive strength of 16.0 MPa and a mercury leaching toxicity of 0.05 mg / L, achieving the harmless treatment and resource utilization of solid waste.

[0040] S3. Mercury Recovery: Modification Process: D401 resin (50L resin loading) was reacted with 1.2 mol / L thiourea solution at 50℃ for 3.5 h. 2.5% (by weight) of ATMP crosslinking agent was added, and the reaction continued for another 1.5 h, resulting in a thiourea loading of 1.6 mmol / g. The mercury-containing complex solution was passed through the modified resin at a flow rate of 2.0 BV / h. After adsorption, a sample was taken, and the mercury concentration in the post-adsorption solution was ≤1.96 g / L, with an adsorption rate of 98.0%. Then, a mixture of 0.2 mol / L hydrochloric acid and 0.02 mol / L thiourea was introduced into the saturated resin column for desorption at a controlled flow rate of 3.0 BV / h. The combined mercury concentration was approximately 551.2 g / L, with a desorption rate of 98.5%. The desorbed solution was transferred to an electrolytic cell, and 0.5 mol / L sulfuric acid was added to adjust the conductivity to 10 mS / cm. The desorbed solution was electrolyzed at a current density of 200 A / m² and 40℃ for 60 min, yielding 2084 g of metallic mercury with a purity of 99.98%, representing a total recovery rate of 84.9%. After resin adsorption, the wastewater was aerated for oxidation at an aeration intensity of 0.7 m³ / min. 3 / (m 2 ·h), after oxidizing for 2h, Fe 2+ Oxidation rate: 95.0%. After adding 10% of the consumed ferric sulfate and sodium thiosulfate-citric acid mixture to the oxidized wastewater, it was reused to S2, with a reuse rate of 92.1%.

[0041] Comparative Example 2 S1. Pretreatment of gravity concentrate: 3000g of mercuric sulfide gravity concentrate was added to a stirred tank, and 12L of 0.5mol / L dilute sulfuric acid was added at a liquid-to-solid ratio of 4:1. The mixture was stirred at room temperature for 30min, aerated to remove H2S, and filtered to obtain purified mercuric sulfide. The pretreatment filtrate was neutralized to pH 7.5 with lime, filtered to remove CaSO4 precipitate, and the neutralized filtrate was reused in the S1 pretreatment process, with a reuse rate of 94.3%.

[0042] S2. Mercury Leaching: Depurified mercuric sulfide was added to a double-chamber reactor, and 21.6 L of a composite leaching solution (0.8 mol / L sodium thiosulfate + 0.3 mol / L citric acid + 0.05 mol / L ferric sulfate) was added at a solid-liquid ratio of 1 g: 6 mL. The temperature was controlled at 60℃, pH 5, and stirring speed at 300 rpm for 120 min, yielding a mercury-containing complex solution and leaching tailings. Testing of the mercury-containing complex solution showed a single-pass leaching rate of 95.3%. The leaching tailings were mixed with lime neutralization residue at a ratio of 1:0.4 and ball-milled to 200 mesh to obtain a building material additive. Testing showed a 7-day compressive strength of 16.2 MPa and a mercury leaching toxicity of 0.04 mg / L, achieving both harmless treatment and resource utilization of solid waste.

[0043] S3. Mercury Recovery: The mercury-containing complex solution was passed through a modified resin at a flow rate of 2.0 BV / h. Unmodified D401 resin (without thiourea treatment, without ATMP crosslinking, and a resin packing volume of 50 L) was used. After adsorption, the mercury concentration in the post-adsorption liquid was measured to be ≤8.32 g / L, and the adsorption rate was calculated to be 86.5%. Then, a mixture of 0.2 mol / L hydrochloric acid and 0.02 mol / L thiourea was introduced into the saturated resin column for desorption at a controlled flow rate of 3.0 BV / h. The combined mercury concentration was measured to be approximately 598.4 g / L, with a desorption rate of 98.5%. The desorbed solution was transferred to an electrolytic cell, and 0.5 mol / L sulfuric acid was added to adjust the conductivity to 10 mS / cm. The desorbed solution was electrolyzed at a current density of 200 A / m² and 40 °C for 60 min, yielding 2010 g of metallic mercury with a purity of 99.99%, representing a total recovery rate of 81.9%. After resin adsorption, the wastewater was aerated for oxidation at an aeration intensity of 0.7 m³ / min. 3 / (m 2 ·h), after oxidizing for 2h, Fe 2+ The oxidation rate was 98.5%. After adding 10% of the consumed ferric sulfate and sodium thiosulfate-citric acid mixture to the oxidized wastewater, it was reused in S2, with a reuse rate of 92.0%.

[0044] Comparative Example 3 S1. Pretreatment of gravity concentrate: Take 3000g of mercuric sulfide gravity concentrate and put it into a stirring tank. Add 12L of 0.5mol / L dilute sulfuric acid at a liquid-solid ratio of 4:1. Stir at room temperature for 30min, aerate to remove H2S, and filter to obtain purified mercuric sulfide.

[0045] S2. Mercury Leaching: Removed mercuric sulfide was added to a double-chamber reactor, and 21.6 L of a composite leaching solution (0.8 mol / L sodium thiosulfate + 0.3 mol / L citric acid + 0.05 mol / L ferric sulfate) was added at a liquid-to-solid ratio of 6:1. The temperature was controlled at 60℃, pH 5, and stirring speed at 300 rpm for leaching for 120 min, yielding a mercury-containing complex solution and leaching tailings. Measurements of the mercury-containing complex solution showed a single-pass leaching rate of 96.4%.

[0046] S3. Mercury Recovery: Modification Process: D401 resin (50L resin loading) was reacted with 1.2 mol / L thiourea solution at 50℃ for 3.5 h. 2.5% (by weight) of ATMP crosslinking agent was added, and the reaction continued for another 1.5 h, resulting in a thiourea loading of 1.6 mmol / g. The mercury-containing complex solution was passed through the modified resin at a flow rate of 2.0 BV / h. After adsorption, a sample was taken, and the mercury concentration in the post-adsorption solution was ≤0.87 g / L, with an adsorption rate of 99.2%. Then, a mixture of 0.2 mol / L hydrochloric acid and 0.02 mol / L thiourea was introduced into the saturated resin column for desorption at a controlled flow rate of 3.0 BV / h. The combined mercury concentration was approximately 640.3 g / L, with a desorption rate of 98.5%. The desorption solution was transferred to an electrolytic cell, and 0.5 mol / L sulfuric acid was added to adjust the conductivity to 10 mS / cm. The desorption solution was electrolyzed at a current density of 200 A / m² and 40 °C for 60 min to obtain 2312 g of metallic mercury with a purity of 99.98% and a total recovery rate of 94.2%.

[0047] The specific experimental data statistics of the above embodiments and comparative examples are shown in Table 2.

[0048] Table 2 Comparison of key indicator data in Examples 1-3 and Comparative Examples 1-3 From the table above, we can deduce that: In Examples 1-3, the process of the present invention achieves high levels of extraction efficiency, resource recycling rate, and environmental friendliness for mercury sulfide, and exhibits excellent raw material adaptability. For high-grade mercury sulfide gravity concentrate (HgS content 95.0%) and low-grade mercury sulfide flotation concentrate (HgS content 29.5%), the total leaching rate is consistently between 93.5% and 97.1%. Example 2, through a combination of "primary leaching + secondary ligand addition leaching," achieves a total leaching rate of 97.1% for the low-grade flotation concentrate, effectively solving the industry problem of insufficient leaching of low-grade raw materials. Under a standard concentration composite leaching system, the total mercury recovery rate in Examples 1 and 2 reaches 94.5% to 94.9%, with a product purity of 99.99%, meeting the application requirements for industrial-grade high-purity mercury.

[0049] From the perspective of environmental protection and resource recycling, the process achieves significant breakthroughs through a closed-loop design: wastewater recycling rate ≥92% (92.0% in Example 1 and 93.0% in Example 2), and the unit mine wastewater discharge is only 0.97~1.05 m³ / t, far lower than traditional wet processes. After ball milling a mixture of leaching tailings and lime neutralization slag at a ratio of 1:0.3~0.5, it can be used as an additive for building materials (7-day compressive strength 15.8~17.5 MPa), and the mercury leaching toxicity of the tailings is ≤0.045 mg / L, achieving zero discharge and harmless resource utilization of solid waste.

[0050] In contrast, the treatment results of ratios 1-3 were significantly worse, revealing obvious deficiencies in traditional processes or the lack of core technologies: Comparative Example 1 used a single sodium thiosulfate leaching solution without citric acid-assisted complexation and ferric sulfate oxidation. Although other steps were the same as in Example 1, the total leaching rate was only 87.2%, 9.3% lower than in Example 1, and the total mercury recovery rate was only 84.9%, 10% lower than in Example 1. Furthermore, due to the presence of Hg in the leaching solution... 2+ It is prone to redeposition, which leads to increased raw material loss in subsequent electrolysis stages.

[0051] Comparative Example 2 used unmodified D401 thiourea resin, and the resin's adsorption rate for mercury was only 86.5%, which was 12.7% lower than the 99.2% in Example 1, directly resulting in a decrease in the total recovery rate of metallic mercury to 81.9%. At the same time, the unmodified resin had poor stability during recycling, making it difficult to meet the requirements of long-term industrial operation, highlighting the core role of ATMP-modified thiourea chelating resin in enhancing adsorption performance.

[0052] Comparative Example 3 lacked a complete closed-loop recycling process: the pretreatment filtrate and post-adsorption wastewater were directly discharged, and the leaching tailings were landfilled as hazardous waste. Although the total mercury leaching rate (96.4%) and total recovery rate (94.2%) were comparable to Example 1, the wastewater recycling rate was 0, the wastewater discharge per unit mine reached 9.7 m³ / t, and 0.18 t / t of hazardous tailings were generated, resulting in both resource waste and environmental safety hazards. This further proves that closed-loop recycling is a necessary condition for the process to achieve both environmental friendliness and economic efficiency.

[0053] In summary, this invention, through the systematic combination of a "ternary composite leaching system," "ATMP-modified thiourea chelating resin," and "closed-loop recycling treatment," successfully achieves efficient extraction of mercury sulfide gravity separation and flotation concentrate, resource recycling of wastewater, and harmless utilization of solid waste. Compared to the high pollution and high energy consumption of traditional pyrometallurgical processes and the low leaching and low recycling rates of hydrometallurgical processes, this invention has significant advantages in leaching efficiency, environmental friendliness, and raw material adaptability. It provides a feasible technical solution for the large-scale treatment of mercury sulfide gravity separation and flotation concentrate, as well as the resource utilization of wastewater and solid waste, demonstrating broad prospects for industrial application.

[0054] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method for wet mercury extraction from mercury sulfide based on composite leaching and modified resin adsorption, characterized in that, The method includes the following steps: S1. Add mercuric sulfide concentrate to dilute sulfuric acid, stir and react, then filter to obtain purified mercuric sulfide. S2. The purified mercuric sulfide and the composite leaching solution are mixed and stirred to obtain a mercury-containing complex solution; the composite leaching solution is a mixed solution of a complexing agent and ferric sulfate; the complexing agent includes sodium thiosulfate and citric acid; S3. The mercury-containing complex solution is adsorbed by a modified thiourea chelating resin, and then desorbed to obtain a mercury-containing desorbed solution. The mercury-containing desorbed solution is then electrolytically deposited to obtain metallic mercury. The modified thiourea chelating resin is prepared by reacting D401 macroporous resin with a 1.0-1.2 mol / L thiourea solution at 45-55℃ for 3-4 h; adding aminotrimethylenephosphonic acid and continuing the reaction at a constant temperature for 1-2 h.

2. The method for wet mercury extraction from mercury sulfide based on composite leaching and modified resin adsorption according to claim 1, characterized in that, In step S1, the concentration of dilute sulfuric acid is 0.4~0.6 mol / L, the liquid-to-solid ratio is 1g:3.5~4.5mL, and the stirring time is 25~35 min.

3. The method for wet mercury extraction from mercury sulfide based on composite leaching and modified resin adsorption according to claim 1, characterized in that, In the composite leachate, the concentration of sodium thiosulfate is 0.6~1.0 mol / L, the concentration of citric acid is 0.2~0.4 mol / L, the concentration of ferric sulfate is 0.04~0.06 mol / L, and the solid-liquid ratio of the purified mercuric sulfide to the composite leachate is 1g:5.5~6.5mL.

4. The method for wet mercury extraction from mercury sulfide based on composite leaching and modified resin adsorption according to claim 1, characterized in that, In step S2, the stirring leaching temperature is 50~80 ℃, the solution pH is 4~6, the stirring speed is 300~500 rpm, and the stirring time is 100~140 min.

5. The method for wet mercury extraction from mercury sulfide based on composite leaching and modified resin adsorption according to claim 1, characterized in that, In step S3, the flow rate of the mercury-containing complex solution during adsorption is 1.5~4 BV / h; the desorption process uses a mixed solution of hydrochloric acid and thiourea for desorption, and the flow rate is controlled at 2~4 BV / h.

6. The method for wet mercury extraction from mercury sulfide based on composite leaching and modified resin adsorption according to claim 1, characterized in that, In step S3, the cathode in the electrolytic deposition is a titanium-palladium coated electrode, the anode is a high-purity graphite electrode, and the electrolysis conditions are a current density of 180~220 A / m², a temperature of 35~45 ℃, and a time of 60~80 min.

7. The method for wet mercury extraction from mercury sulfide based on composite leaching and modified resin adsorption according to claim 1, characterized in that, Step S2 further includes a secondary leaching, comprising: The leaching residue obtained in step S2 is mixed with the composite leaching solution, and a sodium thiosulfate-citric acid mixture is added. The molar ratio of sodium thiosulfate to citric acid in the mixture is 2.0~3.0:1, and the leaching time is 60~70 min.

8. The method for wet mercury extraction from mercury sulfide based on composite leaching and modified resin adsorption according to claim 1, characterized in that, The method further includes: The filtrate filtered in step S1 is neutralized with lime and filtered again, and the filtrate is returned to S1. The wastewater adsorbed by the modified resin in step S3 is returned to step S2 after aeration oxidation, supplementation with ferric sulfate and complexing agent. The leaching residue from step S2 is neutralized with lime, then ball-milled and used as an additive in building materials.

9. The method for wet mercury extraction from mercury sulfide based on composite leaching and modified resin adsorption according to claim 8, characterized in that, The aeration intensity of the aeration oxidation is 0.5~0.8 m³ / (m²·h).

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