A high-efficiency recovery process based on lead refining caustic sludge

Abstract

The present application relates to the technical field of alkali residue recovery, and particularly relates to a high-efficiency recovery process based on lead refining alkali residue. The process comprises the following steps: leaching the lead refining alkali residue; flocculating the lead residue and preparing a lead mixed solution; preparing a water gel for adsorbing lead; and recovering the lead by using the water gel for adsorbing lead. The present application uses the water gel prepared by coconut shell, cucurbituril and sodium alginate for adsorbing lead ions. The porous framework of coconut shell wood fiber forms three-dimensional through channels, and the rich groups on the surface of the coconut shell wood fiber provide physical adsorption sites. The sodium alginate forms a stable chelate with Pb 2+ by means of lone pair electrons, and the hydrophobic cavity of cucurbituril is embedded in the micropore edge of the wood fiber by means of van der Waals force, and the diameter of the hydrated ion of Pb 2+ is matched, so that Pb 2+ is preferentially hydrated to enter. The water gel and the lead ions selectively capture each other, so that the competition of interference ions such as calcium and magnesium is effectively inhibited, the lead content in the lead mixed solution in the early stage is increased, and a foundation is laid for subsequent lead recovery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of alkali residue recovery, and particularly relates to a high-efficiency recovery process based on lead refining alkali residue. BACKGROUND

[0002] The lead refining alkali residue is a high-risk solid waste produced in the process of lead electrolytic refining. In the molten state of crude lead, sodium hydroxide is added and air is blown in to make tin, antimony, arsenic and other impurities oxidize to form sodium salt, forming a low-melting-point dross. The dross layer is separated by mechanical scraping, and the lead refining alkali residue is obtained after cooling and solidification. Therefore, the lead refining alkali residue has a high lead content and also contains tin, zinc, silicon and other impurities.

[0003] The existing technology generally uses acid leaching method to recover the lead refining alkali residue. The acid leaching method uses simple equipment and has lower energy consumption than high-pressure or electrolysis process. However, a large amount of calcium, iron, zinc and other ions are co-dissolved while the lead is dissolved, resulting in heavy burden of subsequent purification. In addition, the strong acid environment destroys the structure of the adsorption material, making it difficult to realize resource recycling. Another recovery method is to directly recover lead single element by electrolysis. The electrolysis method can selectively precipitate metal elements in the alkali residue by adjusting the current / voltage to control the oxidation-reduction intensity, without using a large amount of chemical reagent. However, the electrolysis method relies on continuous direct current power supply, and the power consumption accounts for a high cost. In addition, the electrolysis method also needs noble metal electrodes or proton exchange membranes, which is costly. Therefore, based on the characteristics of the lead refining alkali residue and the defects of the existing technology, the present application provides a new lead recovery process with high selectivity, low energy consumption and recyclability, to realize the resource utilization and harmless disposal of lead in the alkali residue, and to solve the problems existing in the above-mentioned prior art. SUMMARY

[0004] In view of the deficiencies of the prior art, the purpose of the present application is to provide a high-efficiency recovery process based on lead refining alkali residue.

[0005] A high-efficiency recovery process based on lead refining alkali residue, comprising the following steps:

[0006] S1: leaching the lead refining alkali residue

[0007] The lead refining alkali residue is soaked in a NaOH solution. After the reaction is completed, solid particles are filtered out using a 100-mesh stainless steel screen, and solid-liquid separation is performed, to obtain leaching residue and leaching solution;

[0008] S2: flocculating the lead residue and preparing a lead mixed solution

[0009] The mercapto lignin powder is dissolved in deionized water to prepare a mercapto lignin solution. The mercapto lignin solution is stirred and activated, and then added to the leaching solution. The mixture is stirred, and a polyacrylamide solution is added. The mixture is stirred and centrifuged to obtain lead residue. The lead residue and the leaching residue are combined to obtain treated lead residue. The treated lead residue is immersed in a hydrochloric acid solution, and a magnesium chloride solution is added to obtain a lead mixed solution.

[0010] S3: preparing lead adsorbed hydrogel

[0011] The coconut shell is dried, crushed, sieved, soaked in hydrochloric acid, washed and dried to obtain coconut shell powder. The coconut shell powder is dispersed in pre-cooled liquid, centrifuged, and the supernatant is separated to obtain a coconut shell lignin fiber solution. The coconut shell lignin fiber solution, sodium alginate and cucurbiture solution are mixed and stirred uniformly. APS initiator and MBA crosslinking agent are added to obtain a gel to obtain a lead adsorbed hydrogel.

[0012] S4: recycling lead by using the lead adsorbed hydrogel

[0013] The lead adsorbed hydrogel is immersed in a lead mixed solution for adsorption to obtain a saturated adsorption hydrogel. The saturated adsorption hydrogel is loaded into an acid-resistant glass column, and nitric acid solution is pumped in for desorption. NaOH solution and sodium carbonate solution are added to the desorption liquid, stirred until white precipitate is formed, centrifuged, and the precipitate is separated. The filter cake is washed with deionized water until it is neutral, dried, calcined, and the recycling of lead is completed to obtain PbCO3 crude product.

[0014] Further, step S1 leaches the lead refining alkali residue, including the following steps:

[0015] The lead refining alkali residue is soaked in a NaOH solution with a concentration of 100-105 g / L, the solid-liquid ratio is 1 g:(3-5) mL, the temperature is 60-65℃, and the leaching time is 1.5-2 h. After the reaction is completed, the solid particles are filtered out using a 100 mesh stainless steel screen. The sieved slurry is subjected to solid-liquid separation using a suction filter bottle to obtain leaching residue and leaching liquid.

[0016] Further, step S2 flocculates the lead residue and prepares a lead mixed solution, including the following steps:

[0017] The mercapto lignin powder is dissolved in deionized water to prepare a mercapto lignin solution with a concentration of 1-2 wt%. The stirring speed is 200-300 rpm, and the activation time is 30-35 min. The mercapto lignin solution is added to the leaching liquid at a dosage of 0.5-1.5 g / L. The stirring speed is 300-400 rpm, and the stirring time is 10-15 min. A polyacrylamide solution with a mass fraction of 5-10% in the system is then added, and the stirring speed is 50-100 rpm, and the stirring time is 5-10 min. The system is then allowed to stand for 20-30 min, and the lead residue is obtained by centrifugal separation. The lead residue and the leaching residue are combined to obtain treated lead residue.

[0018] The treated lead residue is immersed in a hydrochloric acid solution with a concentration of 2-4 mol / L, and the liquid-solid ratio is 1 g:(4-6) mL. The temperature is 85-90℃, and the leaching time is 3-4 h. A magnesium chloride solution with a mass fraction of 15-20% in the system is then added, and the pH value is controlled at 1.5-2 to obtain a lead mixed solution.

[0019] Further, step S3 prepares a lead adsorbed hydrogel, including the following steps:

[0020] The coconut shell is dried, crushed, and sieved through an 80-mesh screen. The obtained powder is soaked in hydrochloric acid for 24-25 h, washed with deionized water, and dried to obtain coconut shell powder. The coconut shell powder is dispersed in a pre-cooling liquid cooled to 0-2℃, and centrifuged at a speed of 8000-8100 rpm for 10-15 min. The supernatant is separated to obtain a coconut shell lignin fiber solution.

[0021] The coconut shell lignin fiber solution, sodium alginate, and cucurbituril solution are mixed in a volume ratio of (2-2.5):1:1, stirred uniformly, and then 0.25-0.5 mol% of APS initiator and 1.5-2 mol% of MBA crosslinking agent are added. After stirring for 10-15 min, the mixture is transferred to a reactor, which is sealed and uniformly heated in a water bath at 70-75℃ for 3-3.5 h to complete the gelation process, thereby obtaining a lead-adsorbed hydrogel.

[0022] Further, the step S4 recovers lead by using the lead-adsorbed hydrogel, including the following steps:

[0023] The lead-adsorbed hydrogel is immersed in a lead mixed solution at a solid-liquid ratio of 1g:(20-25)mL, and simultaneously oscillated in a 50-60 rpm shaker for 3-4 h to obtain a saturated hydrogel.

[0024] The saturated hydrogel is loaded into an acid-resistant glass column, and a 0.8-1 mol / L nitric acid solution is pumped into the column at a flow rate of 2-3 BV / h, with the temperature controlled at 25-30℃, and the desorption is continued for 2-3 h. NaOH solution is slowly added to the desorption solution to adjust the pH to 8.5-9, and then sodium carbonate solution is added. After stirring, white precipitate is generated. The precipitate is separated by centrifugation at a speed of 3000-3100 rpm for 10-15 min. The filter cake is washed with deionized water until neutral, and then dried to obtain a PbCO3 crude product. The PbCO3 is placed in a muffle furnace and calcined at 600-650℃ for 2-2.5 h to complete the recovery of lead.

[0025] Further, the content of the mercapto group in the mercaptolignin is 2-3 mmol / g.

[0026] Further, the concentration of the magnesium chloride solution is 5-6 mol / L.

[0027] Further, the pre-cooling liquid is prepared by mixing NaOH, urea, and water in a mass ratio of 7:(12-13):(80-85).

[0028] Further, the packing density of the saturated hydrogel is 0.4-0.6 g / mL.

[0029] Compared with the prior art, the present application has at least the following beneficial effects:

[0030] 1. The application prepares the hydrogel for adsorbing lead ions by using coconut shell, cucurbituril and sodium alginate, the porous framework of coconut shell lignocellulose forms three-dimensional through pores, the rich groups on the surface provide physical adsorption sites, accelerate the diffusion of Pb 2+ and improve the water holding capacity of the gel, after the carboxyl group on the sodium alginate is ionized in the solution, a stable five-membered ring chelate is formed through the lone pair of electrons and Pb 2+ , the hydrophobic cavity of cucurbituril is embedded into the micropore edge of lignocellulose through van der Waals force, and the diameter of the hydrated ion of Pb 2+ is highly matched, which preferentially allows hydrated Pb 2+ to enter, while blocking larger hydrated calcium ions, the hydrogel and lead ions are selectively captured by host-guest interaction, thereby effectively inhibiting the competition of calcium, magnesium and other interfering ions, and improving the saturated adsorption capacity of the hydrogel to lead, thereby increasing the lead content in the early lead mixed solution, laying a foundation for subsequent lead recovery.

[0031] 2. The application combines complex mercaptolignin with polyacrylamide to flocculate lead residue, which significantly improves the lead recovery efficiency, the high-density mercapto group in mercaptolignin preferentially forms a stable complex with Pb 2+ in an alkaline leaching solution, realizing molecular-level selective capture of lead ions and effectively avoiding the competitive adsorption of coexisting ions such as calcium and zinc, efficiently enriching lead, while the long-chain molecules of polyacrylamide play a bridging role, promoting the rapid aggregation and growth of micrometer-sized lead-mercapto complex particles, overcoming the bottleneck of difficult settling of colloidal lead residue in traditional precipitation method, thereby improving the lead precipitation rate and flocculation settling speed, increasing the lead content in the lead residue, greatly reducing the subsequent acid leaching burden, avoiding the introduction of interfering ions such as iron and aluminum, and improving the purity of subsequent lead carbonate precipitate.

[0032] 3. The application uses hydrogel to adsorb lead, and then uses dilute nitric acid to dynamically desorb, the desorption liquid is adjusted by pH to convert Pb 2+ into Pb(OH)2 colloid, and then sodium carbonate is added to generate PbCO3 precipitate, which efficiently desorbs lead ions by ion exchange, while avoiding the use of strong acid in traditional leaching method to damage the glycosidic bond and crosslinking network of the hydrogel, so that the hydrogel material has the ability of repeated use, and the use of traditional strong acid leaching method will result in the one-time scrap of the adsorbent, and the lead concentration in the desorption liquid obtained by first adsorbing and then desorbing is high, so that electrolysis is not needed to consume additional power and resources to selectively extract lead with high purity, and only simple and fast leaching is needed to obtain lead-containing precipitate, the obtained lead precipitate has high purity, and lead oxide product can be directly obtained by calcination, the recovery rate is higher, the economic benefit is good, the process is more resource-saving and more environmentally friendly. BRIEF DESCRIPTION OF DRAWINGS

[0033] The accompanying drawings, which are incorporated herein and constitute part of the specification, illustrate embodiments of the present disclosure and, together with the description, further serve to explain the principles of the present disclosure and to enable a person skilled in the relevant art to implement and use the present disclosure.

[0034] Figure 1 A high-efficiency recovery process flowchart based on lead refining alkali slag adopted by the embodiments of the present application. DETAILED DESCRIPTION

[0035] A high-efficiency recovery process based on lead refining alkali slag provided by the present application is described in detail below in combination with the drawings and specific embodiments. It is noted here that, in order to make the embodiments more detailed, the following embodiments are the best, preferred embodiments, and other alternative ways can also be adopted by those skilled in the art to implement them; and the drawings are only used to more specifically describe the embodiments and are not intended to specifically limit the present application.

[0036] Embodiment 1:

[0037] A high-efficiency recovery process based on lead refining alkali slag, as shown in Figure 1 , includes the following steps:

[0038] S1: leaching of lead refining alkali slag

[0039] 1 kg of lead refining alkali slag was soaked in a NaOH solution with a concentration of 100 g / L, the solid-liquid ratio was 1 g:3 mL, the temperature was 60℃, and the leaching time was 1.5 h. After the reaction was completed, the solid particles were filtered out using a 100-mesh stainless steel screen, and the sieved slurry was subjected to solid-liquid separation using a suction filter bottle to obtain leaching residue and leaching liquor;

[0040] S2: flocculation of lead slag and preparation of lead mixed liquor

[0041] The mercapto lignin powder was dissolved in deionized water to prepare a mercapto lignin solution with a concentration of 1 wt%, the mercapto content in the mercapto lignin was 2 mmol / g, the stirring speed was 200 rpm, and the activation time was 30 min. The mercapto lignin solution was added to the leaching liquor at a dosage of 0.5 g / L, stirred at 300 rpm for 10 min, and then a polyacrylamide solution with a mass fraction of 5% in the system was added, stirred at 50 rpm for 5 min, and then left to stand for 20 min. The lead slag was obtained by centrifugal separation, and the treated lead slag and the leaching residue were combined to obtain treated lead slag.

[0042] The treated lead slag was immersed in a hydrochloric acid solution with a concentration of 2 mol / L, the liquid-solid ratio was 1 g:4 mL, the temperature was 85℃, and the leaching time was 3 h. Then, a magnesium chloride solution with a concentration of 5 mol / L was added to the system at a mass fraction of 15%, and the pH value was controlled at 1.5 to obtain the lead mixed liquor.

[0043] S3: preparation of lead-absorbed hydrogel

[0044] After drying, the coconut shells are crushed and passed through an 80-mesh sieve. The resulting powder is soaked in hydrochloric acid for 24 hours, then washed and dried with deionized water to obtain coconut shell powder. The coconut shell powder is dispersed in a pre-cooled liquid pre-cooled to 0°C and centrifuged at 8000 rpm for 10 minutes. The supernatant is then separated to obtain a coconut shell wood fiber solution.

[0045] Coconut shell wood fiber solution, sodium alginate and cucurbituril solution were mixed and stirred evenly in a volume ratio of 2:1:1. 0.25 mol% APS initiator and 1.5 mol% MBA crosslinking agent were added. After stirring for 10 min, the mixture was transferred to a reactor. The reactor was sealed and heated uniformly in a water bath at 70 °C for 3 h to complete the gelation process and obtain a lead-adsorbed hydrogel.

[0046] S4: Lead recovery using lead-adsorbing hydrogels

[0047] The hydrogel that adsorbed lead was immersed in a lead mixture at a solid-liquid ratio of 1 g: 20 mL, and simultaneously shaken on a shaker at 50 rpm for 3 h to obtain a hydrogel that was saturated with adsorption.

[0048] The adsorption-saturated hydrogel was packed into an acid-resistant glass column with a packing density of 0.4 g / mL. A 0.8 mol / L nitric acid solution was pumped in at a flow rate of 2 BV / h, and the temperature was controlled at 25℃. Desorption was continued for 2 h. NaOH solution was slowly added to the eluent to adjust the pH to 8.5, followed by the addition of sodium carbonate solution. The mixture was stirred until a white precipitate was formed. The precipitate was separated by centrifugation at 3000 rpm for 10 min. The filter cake was washed with deionized water until neutral and dried to obtain crude PbCO3. The PbCO3 was then placed in a muffle furnace and calcined at 600℃ for 2 h to complete the lead recovery.

[0049] The precooling liquid is prepared by mixing NaOH, urea and water in a mass ratio of 7:12:80.

[0050] Example 2:

[0051] A high-efficiency recovery process based on lead refining alkali residue, such as... Figure 1 As shown, it includes the following steps:

[0052] S1: Leaching of lead refining alkali residue

[0053] 1 kg of lead refining alkali residue was soaked in a NaOH solution with a concentration of 105 g / L, the solid-liquid ratio was 1 g: 5 mL, the temperature was 60 ℃, and the leaching time was 1.5 h. After the reaction was completed, the solid particles were filtered out using a 100-mesh stainless steel sieve. The slurry after sieving was separated into solid and liquid by vacuum filtration flask to obtain leaching residue and leaching liquid.

[0054] S2: Flocculating lead residue and preparing lead mixed solution

[0055] The thiol group lignin powder was dissolved in deionized water to prepare a thiol group lignin solution with a concentration of 2wt%. The thiol group content of the thiol group lignin was 3mmol / g. The stirring speed was 200rpm. The thiol group lignin was activated for 30min. The thiol group lignin was added to the leaching solution at a dosage of 1.5g / L. The stirring speed was 300rpm. The thiol group lignin was stirred for 10min. A polyacrylamide solution with a mass fraction of 5% in the system was added. The stirring speed was 50rpm. The polyacrylamide solution was stirred for 5min. The system was allowed to stand for 20min. The lead residue was obtained by centrifugal separation. The lead residue and the leaching residue were combined to obtain treated lead residue.

[0056] The treated lead residue was immersed in a hydrochloric acid solution with a concentration of 2mol / L. The liquid-solid ratio was 1g:6mL. The temperature was 85℃. The immersion time was 3h. A magnesium chloride solution with a concentration of 6mol / L was added to the system at a mass fraction of 20%. The pH value was controlled at 1.5. The lead mixed solution was obtained.

[0057] S3: Preparing water gel for adsorbing lead

[0058] The coconut shell was dried, crushed, and sieved through an 80-mesh sieve. The obtained powder was soaked in hydrochloric acid for 24h. The powder was washed with deionized water and dried to obtain coconut shell powder. The coconut shell powder was dispersed in a pre-cooled liquid pre-cooled to 0℃. The stirring speed was 8000rpm. The coconut shell powder was centrifuged for 10min. The supernatant was separated to obtain a coconut shell lignin fiber solution.

[0059] The coconut shell lignin fiber solution, sodium alginate, and cucurbiture solution were mixed at a volume ratio of 2.5:1:1. The mixture was stirred uniformly. 0.5mol% of APS initiator and 2mol% of MBA crosslinking agent were added. The mixture was stirred for 10min and then transferred to a reactor. The reactor was sealed and heated uniformly in a water bath at 70℃ for 3h to complete the gelation process. The water gel for adsorbing lead was obtained.

[0060] S4: Recycling lead by using the water gel for adsorbing lead

[0061] The water gel for adsorbing lead was immersed in the lead mixed solution. The solid-liquid ratio was 1g:25mL. The water gel was shaken on a 50rpm shaker for 3h. The water gel saturated with lead was obtained.

[0062] The water gel saturated with lead was loaded into an acid-resistant glass column. The packing density of the water gel saturated with lead was 0.6g / mL. A nitric acid solution with a concentration of 1mol / L was pumped into the glass column at a flow rate of 2BV / h. The temperature was controlled at 25℃. The desorption was performed for 2h. NaOH solution was slowly added to the desorption solution to adjust the pH value to 8.5. Subsequently, sodium carbonate solution was added. The mixture was stirred until white precipitate was formed. The precipitate was separated by centrifugation at a speed of 3000rpm for 10min. The filter cake was washed with deionized water until neutral. The PbCO3 crude product was obtained after drying. The PbCO3 was placed in a muffle furnace. The temperature was increased to 600℃. The PbCO3 was calcined for 2h. The recycling of lead was completed.

[0063] The pre-cooling liquid is prepared by mixing NaOH, urea and water in a mass ratio of 7:13:85.

[0064] Example 3

[0065] A high-efficiency recovery process based on lead refining alkali slag, as shown in Figure 1 The process comprises the following steps:

[0066] S1: leaching of lead refining alkali slag

[0067] 1 kg of lead refining alkali slag was soaked in a NaOH solution with a concentration of 100 g / L, the solid-liquid ratio was 1 g:3 mL, the temperature was 65℃, and the leaching time was 2 h. After the reaction, the solid particles were filtered out using a 100-mesh stainless steel screen. The slurry after sieving was subjected to solid-liquid separation using a suction filter bottle, and the leaching residue and leaching liquid were obtained.

[0068] S2: flocculation of lead slag and preparation of lead mixed solution

[0069] The mercapto lignin powder was dissolved in deionized water to prepare a mercapto lignin solution with a concentration of 1 wt%. The mercapto content of the mercapto lignin was 2 mmol / g. The stirring speed was 300 rpm, and the activation time was 35 min. The mercapto lignin solution was added to the leaching liquid at a dosage of 0.5 g / L. The stirring speed was 400 rpm, and the stirring time was 15 min. Then, a polyacrylamide solution with a mass fraction of 5% in the system was added, and the stirring speed was 100 rpm for 10 min. The mixture was then allowed to stand for 30 min, and the lead slag was obtained by centrifugal separation. The lead slag and the leaching residue were combined to obtain treated lead slag.

[0070] The treated lead slag was immersed in a hydrochloric acid solution with a concentration of 4 mol / L. The liquid-solid ratio was 1 g:4 mL, the temperature was 90℃, and the leaching time was 4 h. Then, a magnesium chloride solution with a concentration of 5 mol / L was added to the system at a mass fraction of 15%, and the pH value was controlled at 2 to obtain the lead mixed solution.

[0071] S3: preparation of lead-absorbed hydrogel

[0072] The coconut shell was dried, crushed, and sieved through an 80-mesh screen. The obtained powder was soaked in hydrochloric acid for 25 h, washed with deionized water, and dried to obtain coconut shell powder. The coconut shell powder was dispersed in a pre-cooling liquid cooled to 2℃, and centrifuged at a speed of 8100 rpm for 15 min. The supernatant was separated to obtain a coconut shell lignin fiber solution.

[0073] The coconut shell lignin fiber solution, sodium alginate, and cucurbiture solution were mixed in a volume ratio of 2.5:1:1 and stirred uniformly. Then, 0.5 mol% of APS initiator and 2 mol% of MBA crosslinking agent were added. After stirring for 15 min, the mixture was transferred to a reactor, which was sealed and heated uniformly in a water bath at 75℃ for 3.5 h to complete the gelation process, and the lead-absorbed hydrogel was obtained.

[0074] S4: Recycling lead by using lead-adsorbed hydrogel

[0075] The lead-adsorbed hydrogel was immersed in a lead mixed solution with a solid-liquid ratio of 1 g:20 mL, and shaken at 60 rpm for 4 h to obtain a saturated lead-adsorbed hydrogel;

[0076] The saturated lead-adsorbed hydrogel was loaded into an acid-resistant glass column, and the packing density of the saturated lead-adsorbed hydrogel was 0.4 g / mL. A 0.8 mol / L nitric acid solution was pumped into the column at a flow rate of 3 BV / h, and the temperature was controlled at 30°C for 2 h. NaOH solution was slowly added to the desorption solution to adjust the pH to 9, and then sodium carbonate solution was added. After stirring, white precipitate was generated. The precipitate was separated by centrifugation at 3100 rpm for 15 min. The filter cake was washed with deionized water until it was neutral. After drying, a crude PbCO3 product was obtained. The PbCO3 was placed in a muffle furnace and calcined at 650°C for 2.5 h to complete the recycling of lead.

[0077] The pre-cooling solution was prepared by mixing NaOH, urea and water in a mass ratio of 7:12:80.

[0078] Comparative Example 1:

[0079] Comparative Example 1 is different from Example 1 in that no thiol lignin powder is added in step S2, and the remaining steps remain unchanged, which is denoted as Comparative Example 1.

[0080] Comparative Example 2:

[0081] Comparative Example 2 is different from Example 1 in that no polyacrylamide is added in step S2, and the remaining steps remain unchanged, which is denoted as Comparative Example 2.

[0082] Comparative Example 3:

[0083] Comparative Example 3 is different from Example 1 in that no cucurbituril solution is added in step S3, and the remaining steps remain unchanged, which is denoted as Comparative Example 3.

[0084] Comparative Example 4:

[0085] Comparative Example 4 is different from Example 1 in that no sodium alginate is added in step S3, and the remaining steps remain unchanged, which is denoted as Comparative Example 4.

[0086] Comparative Example 5:

[0087] Compared with Example 1, the difference of Comparative Example 5 is that the lead refining alkaline residue is leached by leaching method, specifically: "1 kg of lead refining alkaline residue is leached with 15% hydrochloric acid, and hydrogen peroxide is added, the liquid-solid ratio is 5:1, the temperature is 60°C, the reaction time is 1.5 h, the pH value is 1.5, the stirring speed is 200 rpm, and the leaching residue is separated by filtration and converted into a precipitate with a sodium carbonate solution", which is recorded as Comparative Example 5.

[0088] Comparative Example 6:

[0089] Compared with Example 1, the difference of Comparative Example 6 is that the lead in the lead refining alkaline residue is recovered by electrolysis method, specifically: "1 kg of lead refining alkaline residue is electrolyzed, and the lead component is converted into Na2[Pb(OH)4] in the electrolysis, the temperature is 105°C; the electrolyte enters the cation exchange membrane electrolytic cell, and the metal lead is generated in the cathode chamber, and the byproduct oxygen and NaOH are generated in the anode chamber; 2

[0090] Cathode reaction: Pb(OH)4 2- + 2e - → Pb + 4OH -

[0091] Anode reaction: 4OH - → O2↑ + 2H2O + 4e -

[0092] Lead is obtained in the cathode", which is recorded as Comparative Example 6.

[0093] The lead content in the lead mixed solution obtained in step S2 of Examples 1-3 and Comparative Examples 1-2 is detected, as shown in Table 1;

[0094] The extraction rate and purity of PbCO3 obtained in step S4 of Examples 1-3 and Comparative Examples 3-4 are detected, as shown in Tables 2 and 3, respectively;

[0095] The content of lead element in the lead refining alkaline residue of Examples 1-3 and Comparative Examples 5-6 is detected, the purity and weight of the finally obtained lead carbonate are detected, and the lead recovery rate is calculated, the Pb content in PbCO3 is recorded as 77.6%, the mass of the lead refining alkaline residue is 1 kg, and the results are shown in Table 4.

[0096] In Examples 1-3 and Comparative Example 5, the lead element recovery rate (%) = (purity of lead carbonate * mass of lead carbonate * 77.6%) / (content of lead element in lead refining alkaline residue * mass of lead refining alkaline residue);

[0097] ​In Comparative Example 6, the lead element recovery rate (%) = mass of elemental lead / (content of lead element in lead refining alkali residue * mass of lead refining alkali residue). The lead refining alkali residue used in the above examples and comparative examples is the same batch, and each group is repeated for 3 times, and the average value is taken.

[0098] Table 1

[0099]

[0100] Table 2

[0101]

[0102] Table 3

[0103]

[0104] Table 4

[0105]

[0106] As can be seen from Table 1, the lead content of the mercapto-lignin in Comparative Example 1 and the polyacrylamide in Comparative Example 2 dropped from more than 98 mg / mL to below 88 mg / mL and below 90 mg / mL, respectively, indicating that the two components cooperatively complex and flocculate lead ions in step S2, and the absence of one will significantly reduce the capture efficiency.

[0107] As can be seen from Table 2 and Table 3, the PbCO3 extraction rate of the oxalic acid solution in Comparative Example 3 and the sodium alginate in Comparative Example 4 dropped from more than 95.7% to 82.3% and 84.1%, and the purity also dropped from more than 99% to below 96%, indicating that the two components in step S3 together with the lignin fibers of coconut shell play a role in selectively encapsulating, gel-fixing Pb 2+ and inhibiting the co-precipitation of impurities.

[0108] As can be seen from Table 4, the lead recovery rate of Examples 1-3 is stable at about 95.5%; while Comparative Example 5 using conventional 15% hydrochloric acid leaching has only 85.3%, and Comparative Example 6 using traditional electrolysis method also has only 92.7%. This shows that the recovery efficiency of the lead refining alkali residue in the "capture-precipitation-conversion" three-stage process is significantly better than the single wet process or electrolysis process.

[0109] The above examples are only illustrative of the principles and effects of the present application, and are not intended to limit the present application. Any person skilled in the art can modify or change the above examples without departing from the spirit and scope of the present application. Therefore, all equivalent modifications or changes made by those skilled in the art without departing from the spirit and technical idea disclosed by the present application should still be covered by the claims of the present application.

Claims

1. A highly efficient recovery process based on lead refining caustic slags, characterized in that, Comprising the following steps: S1: leaching of lead refining alkali residue The lead refining alkali residue is soaked in NaOH solution, and after the reaction is completed, solid particles are filtered out using a 100-mesh stainless steel screen, solid-liquid separation is performed, and leaching residue and leaching solution are obtained. S2: flocculation of lead residue and preparation of lead mixed solution The mercapto lignin powder is dissolved in deionized water to prepare a mercapto lignin solution, which is added to the leaching solution after stirring and activation, stirred, and then a polyacrylamide solution is added, stirred, and centrifuged to obtain lead residue. The lead residue and the leaching residue are combined to obtain treated lead residue, which is immersed in a hydrochloric acid solution, and a magnesium chloride solution is added to obtain a lead mixed solution. S3: preparation of lead-absorbing hydrogel The coconut shell is dried, crushed, sieved, soaked in hydrochloric acid, washed and dried to obtain coconut shell powder. The coconut shell powder is dispersed in a pre-cooled liquid, centrifuged, and the supernatant is separated to obtain a coconut shell lignin fiber solution. The coconut shell lignin fiber solution, sodium alginate, and cucurbiture solution are mixed and stirred uniformly, and APS initiator and MBA crosslinking agent are added to obtain lead-absorbing hydrogel. S4: recovery of lead using lead-absorbing hydrogel The lead-absorbing hydrogel is immersed in the lead mixed solution for adsorption to obtain saturated lead-absorbing hydrogel, which is loaded into an acid-resistant glass column, pumped into nitric acid solution for desorption, and NaOH solution and sodium carbonate solution are added to the desorption solution, stirred until white precipitate is formed, centrifuged to separate the precipitate, and the filter cake is washed with deionized water until it is neutral. After drying, PbCO3 crude product is obtained, which is calcined to complete the recovery of lead.

2. A process for efficient recovery of lead refining caustic sludge as claimed in claim 1 wherein, Step S1: leaching of lead refining alkali residue, comprising the following steps: The lead refining alkali residue is soaked in a NaOH solution with a concentration of 100-105 g / L, the solid-liquid ratio is 1 g:(3-5) mL, the temperature is 60-65℃, and the leaching time is 1.5-2 h. After the reaction is completed, solid particles are filtered out using a 100-mesh stainless steel screen, and the sieved slurry is subjected to solid-liquid separation using a suction filter bottle to obtain leaching residue and leaching solution.

3. A process for efficient recovery of lead refining caustic sludge as claimed in claim 2 wherein, Step S2: flocculation of lead residue and preparation of lead mixed solution, comprising the following steps: The mercapto lignin powder is dissolved in deionized water to prepare a mercapto lignin solution with a concentration of 1-2 wt%, the stirring speed is 200-300 rpm, and the activation time is 30-35 min. The mercapto lignin solution is added to the leaching solution at a dosage of 0.5-1.5 g / L, stirred at a speed of 300-400 rpm for 10-15 min, and then a polyacrylamide solution with a mass fraction of 5-10% in the system is added, stirred at a speed of 50-100 rpm for 5-10 min, and then allowed to stand for 20-30 min. The mixture is centrifuged to obtain lead residue, which is combined with the leaching residue to obtain treated lead residue. The treated lead residue is immersed in a hydrochloric acid solution with a concentration of 2-4 mol / L, the liquid-solid ratio is 1 g:(4-6) mL, the temperature is 85-90℃, and the leaching time is 3-4 h. Then, a magnesium chloride solution with a mass fraction of 15-20% in the system is added, and the pH value is controlled at 1.5-2 to obtain a lead mixed solution.

4. A process for efficient recovery of lead refining caustic sludge as claimed in claim 3 wherein, Step S3: preparation of lead-absorbing hydrogel, comprising the following steps: The coconut shell is dried, crushed, and sieved through an 80-mesh screen. The obtained powder is soaked in hydrochloric acid for 24-25 h, washed with deionized water, and dried to obtain coconut shell powder. The coconut shell powder is dispersed in a pre-cooling liquid cooled to 0-2℃, and centrifuged at a speed of 8000-8100 rpm for 10-15 min. The supernatant is separated to obtain a coconut shell lignin fiber solution. The coconut shell lignin fiber solution, sodium alginate, and cucurbituril solution are mixed at a volume ratio of (2-2.5):1:1, stirred uniformly, and then 0.25-0.5 mol% of APS initiator and 1.5-2 mol% of MBA crosslinking agent are added. After stirring for 10-15 min, the mixture is transferred to a reactor, which is sealed and heated uniformly in a water bath at 70-75℃ for 3-3.5 h to complete the gelation process, thereby obtaining a lead-adsorbed hydrogel.

5. A process for efficient recovery of lead refining caustic sludge as claimed in claim 4 wherein, Step S4 recovers lead using the lead-adsorbed hydrogel, including the following steps: The lead-adsorbed hydrogel is immersed in a lead mixed solution at a solid-liquid ratio of 1g:(20-25)mL, and simultaneously shaken at 50-60 rpm for 3-4 h to obtain a saturated lead-adsorbed hydrogel. The saturated lead-adsorbed hydrogel is loaded into an acid-resistant glass column, and a 0.8-1 mol / L nitric acid solution is pumped into the column at a flow rate of 2-3 BV / h, with the temperature controlled at 25-30℃ and the desorption process lasting for 2-3 h. NaOH solution is slowly added to the desorption solution to adjust the pH to 8.5-9, followed by the addition of sodium carbonate solution. After stirring, white precipitate is formed. The precipitate is separated by centrifugation at a speed of 3000-3100 rpm for 10-15 min. The filter cake is washed with deionized water until neutral, dried, and then calcined at 600-650℃ for 2-2.5 h to complete the recovery of lead.

6. A process for efficient recovery of lead refining caustic sludge as claimed in claim 3, wherein, The content of sulfhydryl groups in the mercaptolignin is 2-3 mmol / g.

7. A process for efficient recovery of lead refining caustic sludge as claimed in claim 3, wherein, The concentration of the magnesium chloride solution is 5-6 mol / L.

8. A process for efficient recovery of lead refining caustic sludge as claimed in claim 4 wherein, The pre-cooling liquid is prepared by mixing NaOH, urea, and water at a mass ratio of 7:(12-13):(80-85).

9. A process for efficient recovery of lead refining caustic sludge as claimed in claim 5 wherein, The packing density of the saturated lead-adsorbed hydrogel is 0.4-0.6 g / mL.

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