A method for recycling waste printed circuit boards

Abstract

The present application belongs to the field of resource recycling, and discloses a resource recycling method for waste circuit board ash burning, wherein a pH regulator is added to waste circuit board ash to be treated for air aeration oxidation reaction; first leaching reaction is carried out under ORP of 30mV-90mV to obtain first leaching liquid and first leaching residue; second leaching agent is added to the first leaching residue, second leaching reaction is carried out under pH of 2.0-4.0 to obtain second leaching liquid and second leaching residue; a reducing precipitation agent is added to the first leaching liquid for reducing precipitation reaction to obtain reducing precipitation residue and reducing precipitation filtrate. Through the synergistic process of "alkaline precipitation-acid leaching-reducing precipitation", the present application realizes efficient separation and solidification of bromine, deeply removes residual copper in the form of CuBr through the reducing precipitation step, effectively avoids the circulation and accumulation of bromine in the system, and meets the environmental protection discharge requirements.

Description

Technical Field

[0001] This invention belongs to the field of resource recycling and processing, and in particular relates to a method for the resource utilization of waste circuit board ash. Background Technology

[0002] With the rapid upgrading of electronic products, the amount of waste circuit boards generated has increased dramatically. These boards contain large amounts of valuable metals such as copper and zinc, as well as harmful elements such as bromine. Incinerating waste circuit boards produces ash containing high concentrations of heavy metals and bromides, which, if not properly disposed of, will cause serious environmental pollution. Therefore, developing efficient waste circuit board ash treatment technologies to achieve the recovery of valuable metals and the removal of harmful elements is of significant environmental and economic importance.

[0003] Currently, the main methods for treating waste circuit board ash include hydrometallurgy and pyrometallurgy. Patent application CN113528845A discloses a method for the complete resource recovery of waste circuit board smelting ash, employing a two-stage leaching process to treat the ash. Copper concentrate is obtained through Na2S precipitation, zinc concentrate is formed under weakly alkaline conditions, and bromine is recovered through chlorine oxidation and CCl4 extraction. Patent application CN112143899A discloses a method for recovering copper and enriching precious metals from waste circuit boards, including pre-leaching, reduction leaching, and electrowinning steps. Patent application CN108277357A relates to a method for separating and recovering silver and lead from dust collector ash in steel plant sintering mills, using ammonium carbonate as both a conversion agent and a leaching agent for metal separation. Patent application CN120843837A discloses a method for recovering precious metals from waste circuit boards using a bromine-based leaching agent system, employing a stable bromine-based strong oxidant, sodium bromide, and sodium iodide as the leaching agent system. Patent application CN105648225A discloses a method for separating amphoteric metals from waste circuit boards, using a stepped alkaline dissolution process to achieve selective metal separation. However, these existing treatment methods still have many shortcomings: firstly, the bromine removal efficiency is generally low, making it difficult to meet environmental emission requirements; secondly, the consumption of acid and alkali reagents during the process is high, increasing treatment costs; and thirdly, the recovery rate of valuable metals is not high, and resource utilization efficiency needs to be improved. These problems severely restrict the industrial application of waste circuit board ash treatment technology, making it difficult to effectively remove bromine from waste circuit board ash and efficiently recover valuable metals such as copper and zinc, thus failing to meet environmental protection requirements and the needs of resource utilization. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the background art above and provide a resource utilization method for waste circuit board ash. This resource utilization method has the characteristics of high bromine removal efficiency, low reagent cost and high metal recovery rate, and can achieve effective removal of bromine and efficient recovery of valuable metals such as copper and zinc from waste circuit board ash.

[0005] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:

[0006] A method for resource recovery from waste circuit board ash includes the following steps: (1) Add pH adjuster to waste circuit board ash to be treated, adjust pH to 7.5-9.0, and carry out air aeration oxidation reaction for 30-60 min; then add first leaching agent, carry out first leaching reaction under the condition of redox potential ORP of 30mV-90mV, and after the reaction is completed, separate solid and liquid to obtain first leaching solution rich in bromine and chloride ions, and first leaching residue rich in copper and zinc precipitates; (2) Add a second leaching agent to the first leaching residue and carry out a second leaching reaction under the condition of pH 2.0 to 4.0. After the reaction is completed, the solid and liquid are separated to obtain a second leaching solution rich in copper and zinc ions and a second leaching residue with iron phosphate as the main component. (3) Add a reducing precipitant to the first leachate and carry out a reduction precipitation reaction under the conditions of pH 2.0 to 4.0, temperature 35℃ to 45℃, and ORP -50mV to -100mV. After the reaction is completed, the solid and liquid are separated to obtain a reduction precipitate residue with cuprous bromide as the main component and a reduction precipitate filtrate.

[0007] In the above-mentioned resource recovery method, preferably, the mass percentage of Cu in the waste circuit board ash to be treated is 18%–28%, the mass percentage of Zn is 5%–10%, the mass percentage of Br is 16%–26%, the mass percentage of S is 4%–8%, the mass percentage of O is 24%–32%, the mass percentage of Na is 1%–3%, the mass percentage of K is 1%–3%, the mass percentage of P is 2%–5%, and the mass percentage of Fe is 1%–3%. In the waste circuit board ash, Cu mainly exists in the form of CuBr, Cu oxides, and sulfates, while Zn mainly exists in the form of ZnBr2, Zn oxides, and sulfates.

[0008] In the above-mentioned resource recovery method, preferably, in step (1), the pH adjuster is an aqueous solution of one or more of NaOH and KOH; The first leaching agent is one or more of Na2CO3, NaHCO3, K2CO3, KHCO3, and CO2.

[0009] In the above-mentioned resource recovery method, preferably, in step (1), the aeration rate of the air aeration to the mass ratio of the waste circuit board ash is 1-3 m³. 3 / kg; By quantitatively supplying oxidation, enhancing the reaction process, and co-controlling with ORP, the overall cost can be reduced.

[0010] The ratio of carbon in the first leaching agent to the total molar amount of copper and zinc in the waste circuit board ash is 0.3–0.6:1. This ratio provides just enough carbonate ions to precipitate the metal, ensuring a high precipitation rate while avoiding reagent waste and reducing the burden of subsequent liquid treatment.

[0011] In the above-mentioned resource recovery method, preferably, in step (2), the second leaching agent comprises an aqueous solution of H2SO4 and an activator, wherein the activator is one or more of gluconic acid, malic acid, and lactic acid; The ratio of the activator to the total molar number of copper and zinc elements in the first leaching residue is 0.25 to 0.45:1.

[0012] The second leaching agent contains an activator. The hydroxycarboxylic acid in the activator has a strong complexing ability for copper and zinc ions, forming soluble complexes at the solid-liquid interface. This significantly lowers the energy barrier of the dissolution reaction, thereby greatly improving the leaching reaction kinetics and leaching efficiency. Controlling the ratio of the activator to the total molar amount of copper and zinc in the first leaching residue to 0.25–0.45:1 ensures sufficient activation while avoiding excessive reagent dosage.

[0013] In the above-mentioned resource recovery method, preferably, in step (3), the reducing precipitant is Na2SO3, Na2S2O3, NaHSO3, SO42-. 2、 One or more of hydroxylamine hydrochloride and ascorbic acid. The reducing precipitant can reduce divalent copper to monovalent copper, promoting the formation of CuBr precipitate.

[0014] In the above-mentioned resource recovery method, the purpose of step (1) is to convert Cu and Zn in the waste circuit board ash into insoluble Cu(OH)2, Zn(OH)2, ZnCO3, and CuCO3 precipitates, fixing copper and zinc in the slag, while retaining Br and Cl in the solution, thus achieving preliminary and efficient separation of Cu and Zn from Br and Cl. The copper in the waste circuit board ash may be cuprous (Cu2+) + It exists in the form of copper (e.g., CuBr). Air aeration aims to oxidize it to divalent copper (Cu), which is more likely to form a stable precipitate. 2+ Controlling ORP within a mild oxidation range of 30mv to 90mv ensures complete oxidation while avoiding excessive oxidation that leads to ineffective oxygen consumption and potential increased reagent consumption.

[0015] In step (1), a pH adjuster is first added to precisely control the initial pH of the system to a weakly alkaline range, laying the foundation for the subsequent carbonate precipitation reaction. Compared to a strongly alkaline environment (pH>10), this significantly reduces the amount of alkali used and lowers reagent costs. Subsequently, Na2CO3, NaHCO3, and other first leaching agents (providing CO32-) are added. 2- / HCO3 - ), can be with Cu 2+ Zn 2+ The reaction produces basic carbonate or hydroxide precipitates with low solubility products, such as Cu2(OH)2CO3, Zn2(OH)6(CO3)2, or Cu(OH)2, Zn(OH)2.

[0016] In the above-described resource recovery method, the purpose of step (2) is to redissolve the copper and zinc precipitates in the first leaching residue. Under an acidic environment of pH 2.0–4.0, these precipitates can be effectively acidified, allowing Cu to be released. 2+ and Zn 2+ The first leaching solution is then introduced into the second leaching solution. Under weakly acidic conditions of pH 2.0–4.0, the solubility of FePO4 precipitate in the first leaching residue is extremely low, thus effectively suppressing it in the residue phase. This achieves efficient separation of copper and zinc from the main impurity, iron, ensuring the purity of the second leaching solution.

[0017] In the above-described resource recovery method, the purpose of step (3) is to efficiently separate the residual copper in the first leaching solution. This is achieved by adding a reducing precipitant (such as Na2SO3, SO2, etc.) to separate the Cu... 2+ Reduced to cuprous ions (Cu) + Cu + With high concentrations of Br in solution - The copper is combined to form a precipitate of cuprous bromide (CuBr) with extremely low solubility, thereby achieving deep removal of copper.

[0018] In the above resource recovery method, step (3) controls the ORP within the range of -50mV to -100mV to ensure complete reduction to Cu. + To ensure the smooth progress of the CuBr precipitation reaction, controlling the pH to 2.0–4.0 can effectively prevent Cu from precipitating. + Disproportionation or hydrolysis occurs to ensure its stability and interaction with Br. - Combined precipitation. Appropriate heating (35℃-45℃) can significantly accelerate the kinetics of the reduction and precipitation reaction and shorten the reaction time.

[0019] In the above-mentioned resource recovery method, preferably, the reduction precipitate obtained in step (3) is returned to step (1) and mixed with new waste circuit board ash to repeat step (1). The reduction precipitate is rich in copper and bromine. When it is returned to step (1), the CuBr in it can be re-oxidized and converted under alkaline aeration, so that this part of copper can re-enter the main recovery process of "precipitation-acid leaching-crystallization", thereby realizing the "capture" and recovery of dispersed copper in the system and improving the overall copper recovery rate of the process.

[0020] The above-mentioned resource recovery method, preferably, further includes step (4): the second leachate obtained in step (2) is concentrated by membrane, and then cooled and crystallized, with the cooling and crystallization temperature controlled at -5℃ to 5℃, and copper sulfate crystals and cooling crystallization mother liquor are obtained after solid-liquid separation; then the cooling crystallization mother liquor is evaporated and crystallized, with the evaporation and crystallization temperature controlled at 80℃ to 95℃, and zinc sulfate crystals and evaporation crystallization mother liquor are obtained after solid-liquid separation.

[0021] In the above-mentioned resource recovery method, preferably, the copper ion concentration in the second leachate after membrane concentration is 150-200 g / L and the zinc ion concentration is 60-80 g / L; the copper concentration in the cooling crystallization mother liquor is 35-55 g / L and the zinc concentration is 60-80 g / L.

[0022] In the above-mentioned resource recovery method, preferably, a portion of the evaporated crystallization mother liquor is returned to the cooling crystallization step (4), and the remaining portion is returned to the reduction precipitation reaction step (3); the ratio of the volume of the evaporated crystallization mother liquor returned to the cooling crystallization step to the volume of the evaporated crystallization mother liquor returned to the reduction precipitation reaction step is 3-5:1. The evaporated crystallization mother liquor contains a small amount of incompletely crystallized copper and zinc, as well as accumulated soluble impurities such as bromine. Most of the evaporated crystallization mother liquor is returned to the cooling crystallization step, allowing the valuable metals (Cu, Zn) in it to participate in the crystallization process again, thereby improving the overall metal recovery rate. A small portion of the evaporated crystallization mother liquor is returned to step (3), where the bromide and copper ions are used to further generate CuBr precipitate under reducing conditions. This not only recovers the residual copper, but more importantly, it provides a controllable process open point for bromine, preventing it from accumulating indefinitely within the crystallization system and affecting the quality of the crystallized product.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) This invention achieves efficient separation and solidification of bromine through a synergistic process of "alkaline precipitation - acidic leaching - reduction precipitation". The residual copper is deeply removed in the form of CuBr through the reduction precipitation step, which effectively avoids the cyclic accumulation of bromine in the system and meets the environmental emission requirements.

[0024] (2) The present invention adopts a two-stage leaching combined with activator enhancement, which significantly improves the leaching efficiency of copper and zinc; then, through subsequent step-by-step crystallization, the copper sulfate and zinc sulfate are highly separated, the overall metal recovery rate is significantly improved, and the valuable metal is efficiently recovered.

[0025] (3) By precisely controlling the reaction pH, ORP and reagent ratio, the present invention avoids the excessive use of reagents; the recycling of reduction precipitate and cooling crystallization mother liquor further reduces the consumption of fresh reagents, and the overall treatment cost is economical and feasible. Attached Figure Description

[0026] 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.

[0027] Figure 1 This is a process flow diagram of the resource utilization of waste circuit board ash in an embodiment of the present invention; Figure 2 This is an XRD pattern of the burnt ash from a discarded circuit board in an embodiment of the present invention. Detailed Implementation

[0028] 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.

[0029] 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.

[0030] 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.

[0031] The waste circuit board ash processed in the following examples and comparative examples was taken from a solid waste incinerator in Yunnan Province. The mass percentages of Cu, Zn, Br, S, O, Na, K, P, and Fe were 23.2%, 7.8%, 21.2%, 7.0%, 27.5%, 2.4%, 2.1%, 3.5%, and 1.6%, respectively. Its XRD pattern is shown below. Figure 2 As shown.

[0032] Example 1: A method for resource utilization of waste circuit board ash according to the present invention is shown in the process flow diagram below. Figure 1 As shown, it includes the following steps: (1) Add 50L of pH adjuster (containing 2.5g of NaOH) to 5kg of waste circuit board ash to adjust the pH to 8.0, and aerate for 30min (the ratio of air aeration to waste circuit board ash is 2m). 3 After adding the first leaching agent (Na2CO3 1.15kg), the molar ratio of C element in the first leaching agent to Cu and Zn in the waste circuit board ash is controlled to be 0.45:1. Stir and carry out the first leaching reaction. The reaction ORP is 60mv, so that about 85% of the copper and about 90% of the zinc in the waste circuit board ash precipitate into the first leaching residue in the form of basic carbonates. After the reaction is completed, filter to obtain 49.74L of first leaching solution and 2.63kg of first leaching residue. (2) Add 13.13 kg of second leaching agent (1.05 kg of H2SO4 and 1.15 kg of activator gluconic acid) to 2.63 kg of first leaching residue. The total molar ratio of activator to Cu and Zn in the first leaching residue is 0.35:1. Stir and carry out the second leaching reaction. The pH of the second leaching is 3.0. After the reaction is completed, filter to obtain 15.73 L of second leaching solution and wet residue. After drying the wet residue, 210 g of second leaching residue (dry residue) is obtained. (3) Add 430g of reducing precipitant (Na2S2O3) to 49.74L of the first leachate, heat and stir to carry out the reduction precipitation reaction, control the reaction pH to 3.0, the reaction temperature to 40℃, the reaction ORP to -75mv, and after the reaction is completed, slowly cool down and filter to obtain 0.37kg of reduction precipitate residue and 49.70L of reduction precipitate filtrate; (4) Mix the reduction precipitate residue with the waste circuit board ash, repeat the above step (1), and adjust the amount of reagent added appropriately according to the above control principle.

[0033] (5) The 15.73L second leachate obtained in step (2) is concentrated by membrane (operating pressure is 1.0MPa) to obtain 5.24L concentrate, in which the copper concentration is 184g / L and the zinc concentration is 65g / L. The concentrate is cooled and crystallized, and the cooling and crystallization temperature is controlled at 0℃ to obtain 2.83kg copper sulfate pentahydrate crystals and cooling crystallization mother liquor. The copper concentration in the cooling crystallization mother liquor is 46g / L and the zinc concentration is 65g / L. The cooling crystallization mother liquor is evaporated and crystallized, and the evaporation and crystallization temperature is controlled at 87℃ to obtain 1.51kg zinc sulfate heptahydrate crystals and 2.88kg evaporation and crystallization mother liquor.

[0034] (6) The mother liquor of evaporation crystallization is fed into the cooling crystallization step of step (5) and the reduction precipitation step of step (3), respectively. The volume ratio of the mother liquor of evaporation crystallization entering the cooling crystallization and reduction precipitation steps (2.31L and 0.58L respectively) is 4:1.

[0035] After the above steps, a total of 4.44 kg of qualified copper sulfate pentahydrate and 1.67 kg of qualified zinc sulfate heptahydrate were obtained. The copper sulfate had a purity of 98.5% and a bromine content of 0.3%, meeting the requirements of HG / T 5215-2017 "Industrial Copper Sulfate" standard. The zinc sulfate had a purity of 98.3% and a bromine content of 0.2%, meeting the requirements of Class II Grade 1 of the "Industrial Zinc Sulfate" (HG / T 2326-2015) standard. The comprehensive recovery rate of copper was 98%, and the comprehensive recovery rate of zinc was 97%.

[0036] Example 2: A method for resource utilization of waste circuit board ash according to the present invention is shown in the process flow diagram below. Figure 1 As shown, it includes the following steps: (1) Add 15L of pH adjuster (containing 1.2g of NaOH) to 5kg of waste circuit board ash to adjust the pH to 7.5. After aeration for 30min (the ratio of air aeration to waste circuit board ash is 1m), 3 / kg), and continue to add the first leaching agent (NaHCO3 0.61kg), control the total molar ratio of C in the first leaching agent to Cu and Zn in the waste circuit board ash to be 0.3:1, stir and carry out the first leaching reaction, the reaction ORP is 30mv, filter after the reaction is completed, and obtain 14.75L of the first leaching solution and 2.55kg of the first leaching residue; (2) Add 7.64 kg of second leaching agent (0.99 kg of H2SO4 and 0.54 kg of activator malic acid) to 2.55 kg of first leaching residue. The total molar ratio of activator to Cu and Zn in the first leaching residue is 0.25:1. Stir and carry out the second leaching reaction. Control the mass ratio of second leaching agent to first leaching residue to be 3:1. The pH of the second leaching is 2.0. After the reaction is completed, filter to obtain 10.16 L of second leaching solution and wet residue. After drying the wet residue, 210 g of second leaching residue (dry residue) is obtained. (3) Add 169g of reducing precipitant (NaHSO3) to 14.75L of the first leachate, heat and stir to carry out the reduction precipitation reaction, control the reaction pH to 2.0, the reaction temperature to 35℃, the reaction ORP to -50mv, and after the reaction is completed, slowly cool down and filter to obtain 0.44kg of reduction precipitate residue and 14.70L of reduction precipitate filtrate. (4) Mix the reduction precipitate residue with the waste circuit board ash, repeat step (1), and adjust the amount of reagent added appropriately according to the above control principles.

[0037] (5) The second leachate obtained in step (2) is concentrated by membrane (operating pressure is 1.0 MPa) to obtain 5.08 L of concentrate, in which the copper concentration is 180 g / L and the zinc concentration is 64 g / L. The concentrate is cooled and crystallized, and the cooling crystallization temperature is controlled at -5℃ to obtain 2.68 kg of copper sulfate pentahydrate crystals and cooling crystallization mother liquor. The copper concentration in the cooling crystallization mother liquor is 45 g / L and the zinc concentration is 64 g / L. The cooling crystallization mother liquor is evaporated and crystallized, and the evaporation crystallization temperature is controlled at 80℃ to obtain 1.44 kg of zinc sulfate heptahydrate crystals and 2.79 kg of evaporation crystallization mother liquor.

[0038] (6) The mother liquor from evaporation crystallization enters the cooling crystallization step and the reduction precipitation step respectively. The volume ratio of the mother liquor from evaporation crystallization entering the cooling crystallization step and the reduction precipitation step (2.09L and 0.70L respectively) is 3:1.

[0039] After the above steps, 4.39 kg of qualified copper sulfate pentahydrate and 1.65 kg of qualified zinc sulfate heptahydrate were finally obtained. The copper sulfate had a purity of 98.4% and a bromine content of 0.4%, meeting the requirements of HG / T 5215-2017 "Industrial Copper Sulfate" standard. The zinc sulfate had a purity of 98.2% and a bromine content of 0.3%, meeting the requirements of Class II Grade 1 of "Industrial Zinc Sulfate" (HG / T 2326-2015) standard. The comprehensive recovery rate of copper was 97%, and the comprehensive recovery rate of zinc was 96%.

[0040] Example 3: A method for resource utilization of waste circuit board ash according to the present invention is shown in the process flow diagram below. Figure 1 As shown, it includes the following steps: (1) Add 25L of pH adjuster (containing 8.3g KOH) to 5kg of ash to adjust the pH to 9.0. After air aeration for 60min (the ratio of air aeration to waste circuit board ash is 3m), 3 / kg), continue to add the first leaching agent (CO2 0.64kg), control the total molar ratio of C in the first leaching agent to Cu and Zn in the waste circuit board ash to be 0.6:1, stir and carry out the first leaching reaction, the reaction ORP is 90mv, filter after the reaction is completed, and obtain 24.74L of the first leaching solution and 2.63kg of the first leaching residue; (2) Add 26.26 kg of second leaching agent (1.02 kg of H2SO4 and 0.68 kg of activator lactic acid) to 2.63 kg of first leaching residue. The molar ratio of activator to Cu and Zn in the first leaching residue is 0.45:1. Stir and carry out the second leaching reaction. Control the mass ratio of second leaching agent to first leaching residue to be 3:1. The pH of the second leaching is 4.0. After the reaction is completed, filter to obtain 28.86 L of second leaching solution and wet residue. After drying the wet residue, obtain 210 g of second leaching residue (dry residue). (3) Add 171g of reducing precipitant (Na2SO3) to 24.74L of the first leachate, heat and stir to carry out the reduction precipitation reaction, control the reaction pH to 4.0, the reaction temperature to 45℃, the reaction ORP to -100mv, and after the reaction is completed, slowly cool down and filter to obtain 0.37kg of reduction precipitate residue and 24.70L of reduction precipitate filtrate; (4) Mix the reduction precipitate residue with the waste circuit board ash, repeat step (1), and adjust the amount of reagent added appropriately according to the above control principles.

[0041] (5) The second leachate was concentrated by membrane (operating pressure 1.1 MPa) to obtain 5.77 L of concentrate, in which the copper concentration was 167 g / L and the zinc concentration was 59 g / L. The concentrate was cooled and crystallized at 5 °C to obtain 2.83 kg of copper sulfate pentahydrate crystals and cooling crystallization mother liquor. The copper concentration in the cooling crystallization mother liquor was 42 g / L and the zinc concentration was 59 g / L. The cooling crystallization mother liquor was evaporated and crystallized at 95 °C to obtain 1.51 kg of zinc sulfate heptahydrate crystals and 3.17 kg of evaporation crystallization mother liquor.

[0042] (6) The mother liquor from evaporation crystallization enters the cooling crystallization step and the reduction precipitation step respectively. The volume ratio of the mother liquor from evaporation crystallization entering the cooling crystallization step and the reduction precipitation step (2.65L and 0.53L respectively) is 5:1.

[0043] After the above steps, 4.46 kg of qualified copper sulfate pentahydrate and 1.69 kg of qualified zinc sulfate heptahydrate were finally obtained. The copper sulfate had a purity of 98.6% and a bromine content of 0.2%, meeting the requirements of HG / T 5215-2017 "Industrial Copper Sulfate" standard. The zinc sulfate had a purity of 98.4% and a bromine content of 0.3%, meeting the requirements of Class II Grade 1 of "Industrial Zinc Sulfate" (HG / T 2326-2015) standard. The comprehensive recovery rate of copper was 99%, and the comprehensive recovery rate of zinc was 98%.

[0044] Comparative Example 1: The difference between this comparative example and Example 1 is that in step (1), the molar ratio of C in the first leaching agent to Cu and Zn in the waste circuit board ash is controlled to be 0.2:1, while the rest is the same as in Example 1.

[0045] After the above steps, 4.40 kg of copper sulfate pentahydrate and 1.67 kg of zinc sulfate heptahydrate were finally obtained. However, the bromine content in both copper sulfate and zinc sulfate was higher than 3%, which did not meet the requirements for product reuse.

[0046] Comparative Example 2: The difference between this comparative example and Example 1 is that in step (6), the mother liquor of evaporation crystallization enters the cooling crystallization step and the reduction precipitation step respectively, and the volume ratio of the mother liquor of evaporation crystallization entering the cooling crystallization step and the reduction precipitation step (1.92L and 0.96L respectively) is 2:1.

[0047] After the above steps, 4.12 kg of qualified copper sulfate pentahydrate and 1.59 kg of qualified zinc sulfate heptahydrate were obtained. The overall copper recovery rate was 91% and the overall zinc recovery rate was 92%, with both copper and zinc recovery rates decreasing.

[0048] Comparative Example 3: The difference between this comparative example and Example 1 is that no activator is added in the second leaching step of step (2), while the rest is the same as Example 1.

[0049] After the above steps, 3.04 kg of qualified copper sulfate pentahydrate and 1.02 kg of qualified zinc sulfate heptahydrate were obtained. The overall copper recovery rate was 67% and the overall zinc recovery rate was 57%, with both copper and zinc recovery rates significantly reduced.

[0050] Comparative Example 4: The difference between this comparative example and Example 1 is that a pH adjuster (202g NaOH) was added to the waste circuit board ash for the first leaching to adjust the pH to 13. The first leaching residue obtained then directly enters the membrane concentration-cooling crystallization and evaporation crystallization in step (5) without undergoing a second leaching. The process parameters of membrane concentration-cooling crystallization and evaporation crystallization are the same as in Example 1. Before membrane concentration, 0.25kg H2SO4 needs to be added to adjust the pH.

[0051] After the above steps, 4.44 kg of qualified copper sulfate pentahydrate and 1.67 kg of qualified zinc sulfate heptahydrate were obtained, with a comprehensive copper recovery rate of 98% and a comprehensive zinc recovery rate of 97%. However, the amount of NaOH added was 202 g, and 0.49 kg of H2SO4 was required for pH adjustment, significantly increasing the reagent cost.

[0052] Comparative Example 5: The difference between this comparative example and Example 1 is that the waste circuit board ash does not undergo the first leaching step, but directly undergoes the second leaching, membrane concentration-cooling crystallization and evaporation crystallization. The second leaching pH is 0.3, the amount of H2SO4 added is 1.44 kg, and other parameters are the same as in Example 1.

[0053] After the above steps, 4.44 kg of copper sulfate pentahydrate and 1.67 kg of zinc sulfate heptahydrate were finally obtained, with a comprehensive copper recovery rate of 98% and a comprehensive zinc recovery rate of 97%. However, the bromine content in both copper sulfate and zinc sulfate was higher than 3%, which did not meet the requirements for product reuse. At the same time, the amount of H2SO4 added was 1.44 kg, which significantly increased the reagent cost.

[0054] The above description of the disclosed embodiments enables those skilled in the art to experiment with or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for resource utilization of waste circuit board ash, characterized in that, Includes the following steps: (1) Add pH adjuster to waste circuit board ash to be treated, adjust pH to 7.5-9.0, and carry out air aeration oxidation reaction for 30-60 min; then add first leaching agent, carry out first leaching reaction under ORP of 30mV-90mV, and after the reaction is completed, separate solid and liquid to obtain first leaching solution rich in bromine and chloride ions, and first leaching residue rich in copper and zinc precipitates; (2) Add a second leaching agent to the first leaching residue and carry out a second leaching reaction under the condition of pH 2.0 to 4.

0. After the reaction is completed, the solid and liquid are separated to obtain a second leaching solution rich in copper and zinc ions and a second leaching residue with iron phosphate as the main component. (3) Add a reducing precipitant to the first leachate and carry out a reduction precipitation reaction under the conditions of pH 2.0 to 4.0, temperature 35℃ to 45℃, and ORP -50mV to -100mV. After the reaction is completed, the solid and liquid are separated to obtain a reduction precipitate residue with cuprous bromide as the main component and a reduction precipitate filtrate.

2. The resource recovery method as described in claim 1, characterized in that, The waste circuit board ash to be processed contains Cu at a mass percentage of 18%–28%, Zn at a mass percentage of 5%–10%, Br at a mass percentage of 16%–26%, S at a mass percentage of 4%–8%, O at a mass percentage of 24%–32%, Na at a mass percentage of 1%–3%, K at a mass percentage of 1%–3%, P at a mass percentage of 2%–5%, and Fe at a mass percentage of 1%–3%.

3. The resource recovery method as described in claim 1, characterized in that, In step (1), the pH adjuster is an aqueous solution of one or more of NaOH and KOH; The first leaching agent is one or more of Na2CO3, NaHCO3, K2CO3, KHCO3, and CO2.

4. The resource recovery method as described in claim 1, characterized in that, In step (1), the aeration rate of the air aeration to the mass ratio of the waste circuit board ash is 1-3 m³. 3 / kg; The ratio of carbon in the first leaching agent to the total molar number of copper and zinc in the waste circuit board ash is 0.3 to 0.6:

1.

5. The resource recovery method as described in claim 1, characterized in that, In step (2), the second leaching agent comprises an aqueous solution of H2SO4 and an activator, wherein the activator is one or more of gluconic acid, malic acid, and lactic acid; The ratio of the activator to the total molar number of copper and zinc elements in the first leaching residue is 0.25 to 0.45:

1.

6. The resource recovery method as described in claim 1, characterized in that, In step (3), the reducing precipitant is one or more of Na2SO3, Na2S2O3, NaHSO3, SO2, hydroxylamine hydrochloride, and ascorbic acid.

7. The resource recovery method according to any one of claims 1 to 6, characterized in that, The reduced precipitate obtained in step (3) is returned to step (1) and mixed with new waste circuit board ash, and step (1) is repeated.

8. The resource recovery method according to any one of claims 1 to 6, characterized in that, The process also includes step (4): the second leachate obtained in step (2) is concentrated by membrane treatment, and then cooled and crystallized. The cooling and crystallization temperature is controlled at -5℃ to 5℃. After solid-liquid separation, copper sulfate crystals and cooling crystallization mother liquor are obtained. Then, the cooling crystallization mother liquor is evaporated and crystallized. The evaporation and crystallization temperature is controlled at 80℃ to 95℃. After solid-liquid separation, zinc sulfate crystals and evaporation crystallization mother liquor are obtained.

9. The resource recovery method as described in claim 8, characterized in that, In the second leachate after membrane concentration, the copper ion concentration is 150-200 g / L and the zinc ion concentration is 60-80 g / L; in the cooling crystallization mother liquor, the copper concentration is 35-55 g / L and the zinc concentration is 60-80 g / L.

10. The resource recovery method as described in claim 8, characterized in that, A portion of the evaporated crystallization mother liquor is returned to the cooling crystallization step in step (4), and the remaining portion is returned to the reduction precipitation reaction step in step (3); the ratio of the volume of the evaporated crystallization mother liquor returned to the cooling crystallization step to the volume of the evaporated crystallization mother liquor returned to the reduction precipitation reaction step is 3 to 5:1.

Images