Electroplating sludge iron resource recycling method based on acid leaching-resin selective adsorption

Abstract

The invention discloses an electroplating sludge iron resource recovery method based on acid leaching-resin selective adsorption, and relates to the field of dangerous solid waste resource treatment.The electroplating sludge iron resource recovery method comprises the following steps that S1, collected electroplating sludge and sodium salt are evenly mixed, roasted, cooled, washed and filtered, and washing liquid and filter residues are obtained; s2, adding water into the filter residues obtained in the S1, uniformly mixing, then mixing with an acid solution, carrying out an acid leaching reaction, and carrying out solid-liquid separation to obtain an acid leaching solution; according to the electroplating sludge iron resource recycling method based on acid leaching-resin selective adsorption, selected specific chelating resin is large in iron ion adsorption capacity and excellent in selectivity under the low pH, competitive interference of coexisting ions such as Cu < 2 + > can be effectively overcome, and the iron recycling rate can reach 99% or above; the adsorption step is carried out under the strong acidic condition and is matched with the characteristics of the electroplating sludge pickle liquor, the pH does not need to be greatly adjusted, the process is simplified, and the cost is reduced.

Description

Technical Field

[0001] This invention relates to hazardous solid waste resource recovery technology, specifically to a method for recovering iron from electroplating sludge based on acid leaching and resin selective adsorption. Background Technology

[0002] With the acceleration of industrialization, the sludge generated by the electroplating industry contains large amounts of heavy metals, such as iron, copper, nickel, zinc, and chromium. These heavy metals pose a serious threat to the environment and human health.

[0003] Traditional methods for treating electroplating sludge include chemical precipitation, ion exchange, membrane separation, and biological treatment. However, these methods often suffer from problems such as low treatment efficiency, high cost, and secondary pollution.

[0004] Existing technologies cannot efficiently and selectively separate iron ions in the strongly acidic leachate of electroplating sludge. Conventional chemical precipitation methods have low precipitation efficiency at low pH and serious co-precipitation phenomenon. Ordinary ion exchange resins or adsorbents have protonated functional groups in strongly acidic environments with pH < 2, resulting in a sharp decline or even failure of adsorption capacity, leading to low iron ion removal rate and poor selectivity.

[0005] The iron sludge produced by chemical precipitation is of low purity and complex composition, and needs to be disposed of as hazardous waste. It cannot be directly utilized as a resource, resulting in waste of resources and secondary pollution, and is not economically viable.

[0006] High concentrations and high chemical activity of iron ions in the acid leaching solution of electroplating sludge can seriously interfere with the subsequent separation and purification of high-value metals such as copper and nickel. Existing iron removal methods are inefficient, resulting in a complex, costly, and low-purity recycling process. Summary of the Invention

[0007] The purpose of this invention is to provide a method for the resource recovery of iron from electroplating sludge based on acid leaching-resin selective adsorption, in order to solve the problems of low efficiency of iron removal methods in the prior art, which leads to a complex resource recovery process, high cost and low purity of the recovered products.

[0008] To achieve the above objectives, the present invention provides the following technical solution: a method for the resource recovery of iron from electroplating sludge based on acid leaching-resin selective adsorption, comprising the following steps:

[0009] S1. The collected electroplating sludge is mixed evenly with sodium salt and then roasted. After cooling, it is washed with water and filtered to obtain washing liquid and filter residue.

[0010] S2. Add water to the filter residue obtained in S1 and mix evenly. Then mix with acid solution to carry out acid leaching reaction. After solid-liquid separation, acid leaching solution is obtained.

[0011] S3. The acid leaching solution obtained in S2 is passed through an adsorption column packed with chelating resin, wherein the chelating resin is a chelating resin containing monophosphate groups, which selectively adsorbs iron ions under the condition of pH 1.5-1.75.

[0012] S4. Desorb the chelating resin that is saturated with adsorption in S3 to obtain an eluent rich in iron ions.

[0013] S5. The iron-rich eluent obtained in S4 is evaporated and concentrated to obtain a crude product of iron salt crystals.

[0014] S6. Dissolve the crude product of the iron salt crystals described in S5 in water and recrystallize it to obtain a high-purity iron salt product.

[0015] Further, in step S1, the sodium salt is one or more of sodium carbonate, sodium hydroxide, or sodium nitrate;

[0016] The roasting temperature is 500-700℃.

[0017] Further, in step S2, the acid solution is an aqueous solution of one or more of sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, or acetic acid, with a concentration of 1-10%.

[0018] Further, in step S3, the chelating resin containing monophosphate groups is ZXC-9 monophosphonic acid group chelating resin, S957 chelating resin, or D418 macroporous aminophosphonic acid type chelating resin.

[0019] Furthermore, the desorption described in step S4 is a two-stage desorption process, including:

[0020] a1. First-stage desorption: Elute the resin with an acid solution of 0.1-1% by mass to remove adsorbed copper, nickel, and zinc impurity ions;

[0021] a2. Second-stage desorption: Elute the resin with an acid solution of 5-10% by mass to obtain the eluent rich in iron ions.

[0022] Furthermore, in both the first-stage and second-stage desorption, the elution flow rate of the acid solution is 1-3 mL / min.

[0023] Furthermore, the acid solution described in steps a1 and a2 is independently selected from sulfuric acid, nitric acid, or hydrochloric acid.

[0024] Further, the recrystallization in step S6 specifically involves: dissolving the crude iron salt crystal product by heating with water, evaporating and concentrating it again, cooling and crystallizing, filtering and drying to obtain the high-purity iron salt product.

[0025] Compared with existing technologies, the present invention provides a method for the resource recovery of iron from electroplating sludge based on acid leaching and resin selective adsorption. The selected specific chelating resin has a large adsorption capacity and excellent selectivity for iron ions at low pH, which can effectively overcome the coexisting ions such as Cu. 2+ With minimal competition and interference, iron recovery rates can reach over 99%.

[0026] The adsorption step is carried out under strongly acidic conditions, which matches the characteristics of the electroplating sludge leaching solution itself. This eliminates the need for significant pH adjustment, simplifies the process, and reduces costs.

[0027] The final product is high-purity iron salt crystals, which can be directly used as industrial raw materials such as water treatment agents and chemical raw materials to improve economic efficiency. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0029] Figure 1 A schematic diagram of the iron removal rate versus time provided in an embodiment of the present invention;

[0030] Figure 2 A schematic diagram of the saturated adsorption capacity of the iron-absorbing resin under different acidic pH values ​​provided in the embodiments of the present invention;

[0031] Figure 3 A process flow diagram provided for an embodiment of the present invention. Detailed Implementation

[0032] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0033] Example 1:

[0034] Please see Figures 1 to 3 A method for the resource recovery of iron from electroplating sludge based on acid leaching-resin selective adsorption includes the following steps:

[0035] S1. The collected electroplating sludge is mixed evenly with sodium salt and then roasted. After cooling, it is washed with water and filtered to obtain washing liquid and filter residue.

[0036] S2. Add water to the filter residue obtained in S1 and mix evenly. Then mix with acid solution to carry out acid leaching reaction. After solid-liquid separation, acid leaching solution is obtained.

[0037] S3. The acid leaching solution obtained in S2 is passed through an adsorption column packed with chelating resin, wherein the chelating resin is a chelating resin containing monophosphate groups, which selectively adsorbs iron ions under the condition of pH 1.5-1.75.

[0038] S4. Desorb the chelating resin that is saturated with adsorption in S3 to obtain an eluent rich in iron ions.

[0039] S5. The iron-rich eluent obtained in S4 is evaporated and concentrated to obtain a crude product of iron salt crystals.

[0040] S6. Dissolve the crude product of the iron salt crystals described in S5 in water and recrystallize it to obtain a high-purity iron salt product.

[0041] In step S1, the sodium salt is one or more of sodium carbonate, sodium hydroxide, or sodium nitrate;

[0042] The roasting temperature is 500-700℃.

[0043] In step S2, the acid solution is an aqueous solution of one or more of sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, or acetic acid, with a concentration of 1-10%.

[0044] In step S3, the chelating resin containing monophosphate groups is ZXC-9 monophosphonic acid group chelating resin, S957 chelating resin, or D418 macroporous aminophosphonic acid type chelating resin.

[0045] Step S4 describes a two-stage desorption process, including:

[0046] a1. First-stage desorption: Elute the resin with an acid solution of 0.1-1% by mass to remove adsorbed copper, nickel, and zinc impurity ions;

[0047] a2. Second-stage desorption: Elute the resin with an acid solution of 5-10% by mass to obtain the eluent rich in iron ions.

[0048] In both the first-stage and second-stage desorption, the elution flow rate of the acid solution is 1-3 mL / min.

[0049] The acid solution described in steps a1 and a2 is independently selected from sulfuric acid, nitric acid, or hydrochloric acid.

[0050] The recrystallization in step S6 specifically involves: dissolving the crude iron salt crystal product by heating with water, evaporating and concentrating it again, cooling and crystallizing, filtering and drying to obtain the high-purity iron salt product.

[0051] Take 1 kg of electroplating sludge with a moisture content of 80%, of which 200 g is dry and contains 15% Fe, 5% Cu, 2% Ni, and 1% Zn. Mix it evenly with 100 g of sodium carbonate and place it in a muffle furnace. Calcine it at 600°C for 3 hours. After cooling, wash the calcined product three times with 500 mL of water each time. Filter to obtain the filter residue.

[0052] The filter residue was transferred to a 2L beaker, 1.5L of deionized water and 100mL of 98% concentrated sulfuric acid were added, and the mixture was stirred and acid-leached at 80℃ for 2 hours. After filtration, the residue was washed with water, and the filtrate and wash water were combined to obtain about 1.8L of acid leaching solution. The pH was measured to be approximately 0.8, and the Fe content was approximately 16.7g / L. The pH of the acid leaching solution was adjusted to 1.6 with NaOH solution.

[0053] The acid leaching solution with pH=1.6 was passed through a glass adsorption column containing 500mL ZXC-9 chelating resin at a flow rate of 2mL / min. The effluent was monitored until the iron concentration began to rise significantly. At this point, the resin adsorbed about 48g of iron.

[0054] First, the adsorption column was eluted with 500 mL of 0.5% dilute sulfuric acid at a flow rate of 2 mL / min. This desorption solution was collected, and it mainly contained impurities such as Cu, Ni, and Zn.

[0055] Elute the adsorption column with 1000 mL of 8% sulfuric acid at a flow rate of 2 mL / min and collect the iron-rich desorption solution.

[0056] The iron-rich desorption solution was placed in an evaporating dish and heated to evaporate, concentrating it to 1 / 5 of its original volume. After cooling, a large amount of brownish-yellow Fe2(SO4)3 coarse crystals precipitated.

[0057] The coarse crystals were dissolved in an appropriate amount of hot water, and then evaporated and concentrated until a crystalline film appeared on the surface. Heating was stopped, and the crystals were allowed to cool naturally and crystallize. The crystals were filtered, washed with a small amount of ice-cold ethanol, and dried under vacuum at 60°C to obtain a high-purity ferric sulfate product. The total iron recovery rate was calculated to be 99.2%, and the product purity exceeded 98.5%.

[0058] The results show that the present invention successfully and selectively separates and recovers iron from electroplating sludge, obtaining high-value-added iron salt products and achieving effective resource recovery.

[0059] Example 2:

[0060] Selection and optimization of pickling agents

[0061] Multiple samples of dried sludge, each with a solid mass of 100g, were taken and placed in a series of reactors. To maintain the same liquid-solid ratio as in Example 1, 1.5L of different types and concentrations of acid solutions were added to each reactor. The reactors were stirred and reacted at 80°C for 2 hours. After the reaction was completed, the samples were filtered, and the concentration of iron ions in the filtrate was measured to calculate the leaching rate.

[0062] The results are shown in the table below:

[0063]

[0064]

[0065] Although hydrochloric acid has the highest leaching rate, it is highly corrosive to equipment, resulting in high costs and risks in industrial applications. Nitric acid is expensive and has strong oxidizing properties, which affects the performance of subsequent resins. Sulfuric acid achieves the best balance between leaching rate, cost, safety, and equipment compatibility. Therefore, sulfuric acid is preferred as the acid leaching agent for industrial applications, and 1.0M sulfuric acid was used for acid leaching in subsequent experiments.

[0066] Example 3:

[0067] This embodiment provides a technical solution based on Embodiment 2:

[0068] Selective adsorption experiment of resin (competitive adsorption)

[0069] To simulate the competition between copper ions and iron adsorption in actual acid leaching solutions, a series of different Fe... 3+ :Cu 2 Simulated solutions with uniformly adjusted pH to 1.6 were used for dynamic adsorption column experiments with ZXC-9 chelating resin. After adsorption saturation, the adsorption capacity of the resin for the two metals was analyzed, and the results are as follows:

[0070] <![CDATA[Fe 3+ :Cu 2+ (mass ratio) Iron adsorption capacity (mg / g resin) Copper adsorption capacity (mg / g resin) 1:1 49.73 12.66 1:3 49.38 17.09 1:5 49.20 28.90

[0071] Experimental results analysis: The data shows that even in Cu 2+ Concentration several times that of Fe 3+ Under extreme conditions, the resin's resistance to Fe 3+ The adsorption capacity remains stable and high, at approximately 49-50 mg / g, while the adsorption capacity for Cu remains high. 2+ Although the adsorption capacity of the resin increases with increasing concentration, it is still much lower than that for iron. This fully demonstrates that the ZXC-9 resin has a high adsorption capacity for Fe at low pH. 3+ It has excellent selective adsorption advantages, can effectively resist the interference of coexisting copper ions, and ensure the high-purity recovery of iron.

[0072] Example 4:

[0073] Actual electroplating sludge treatment verification

[0074] Electroplating plant sludge was subjected to calcination with sodium carbonate at 600℃ in step S1 and acid leaching with sulfuric acid in step S2.0 M to obtain an acid leaching solution with pH≈0.9. The main metal contents were: [Fe]=18.2g / L, [Cu]=5.8g / L, [Ni]=2.1g / L, [Zn]=1.2g / L. The pH of the acid leaching solution was adjusted to 1.6 with NaOH solution.

[0075] The adjusted acid leaching solution was passed through an adsorption column packed with D418 chelating resin at a flow rate of 2 BV / h, with a column volume of 500 mL.

[0076] Monitor the effluent until the iron concentration breaks through to 10% of the inlet concentration. At this point, the working adsorption capacity of the resin for iron is calculated to be approximately 48.5 mg / mL resin.

[0077] Then, the two-stage desorption process in S4 is performed:

[0078] a1 First-stage desorption: Elute with 2.5 L 5 BV 0.5% dilute sulfuric acid at the same flow rate, and collect this desorbed portion (containing Cu, Ni, Zn, etc.);

[0079] a2 Second-stage desorption: Elution with 5 L 10 BV 8% sulfuric acid, and collection of iron-rich desorption solution;

[0080] The iron-rich desorption solution was evaporated and concentrated to 1 / 4 of its original volume. After cooling, a brownish-red crude product, Fe2(SO4)3·xH2O, was obtained. The crude product was dissolved in deionized water at 60°C, evaporated and concentrated again to saturation, and then recrystallized at 5°C using a programmed cooling process. After filtration, washing with ethanol, and vacuum drying, a high-purity ferric sulfate product was obtained.

[0081] Final results: ICP-OES analysis showed that the final product purity was as high as 99.0%, the iron recovery rate of the entire process reached 99.5%, and the iron content in the adsorption liquid and the first-stage desorption liquid was extremely low, creating excellent conditions for the subsequent separate recovery of copper, nickel and zinc.

[0082] This embodiment verifies the industrial applicability of sulfuric acid as an acid leaching agent through systematic experimental data, demonstrates the high selectivity of the selected resin for iron under extreme competitive conditions, and finally successfully recovers high-purity iron products from actual electroplating sludge through a full-process experiment, fully illustrating the feasibility, superiority and industrialization potential of the present invention.

[0083] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A method for the resource recovery of iron from electroplating sludge based on acid leaching-resin selective adsorption, characterized in that, Includes the following steps: S1. The collected electroplating sludge is mixed evenly with sodium salt and then roasted. After cooling, it is washed with water and filtered to obtain washing liquid and filter residue. S2. Add water to the filter residue obtained in S1 and mix evenly. Then mix with acid solution to carry out acid leaching reaction. After solid-liquid separation, acid leaching solution is obtained. S3. The acid leaching solution obtained in S2 is passed through an adsorption column packed with chelating resin, wherein the chelating resin is a chelating resin containing monophosphate groups, which selectively adsorbs iron ions under the condition of pH 1.5-1.

75. S4. Desorb the chelating resin that is saturated with adsorption in S3 to obtain an eluent rich in iron ions. S5. The iron-rich eluent obtained in S4 is evaporated and concentrated to obtain a crude product of iron salt crystals. S6. Dissolve the crude product of the iron salt crystals described in S5 in water and recrystallize it to obtain a high-purity iron salt product.

2. The method for iron resource recovery from electroplating sludge based on acid leaching-resin selective adsorption according to claim 1, characterized in that, In step S1, the sodium salt is one or more of sodium carbonate, sodium hydroxide, or sodium nitrate; The roasting temperature is 500-700℃.

3. The method for iron resource recovery from electroplating sludge based on acid leaching-resin selective adsorption according to claim 1, characterized in that, In step S2, the acid solution is an aqueous solution of one or more of sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, or acetic acid, with a concentration of 1-10%.

4. The method for iron resource recovery from electroplating sludge based on acid leaching-resin selective adsorption according to claim 1, characterized in that, In step S3, the chelating resin containing monophosphate groups is ZXC-9 monophosphonic acid group chelating resin, S957 chelating resin, or D418 macroporous aminophosphonic acid type chelating resin.

5. The method for iron resource recovery from electroplating sludge based on acid leaching-resin selective adsorption according to claim 1, characterized in that, Step S4 describes a two-stage desorption process, including: a1. First-stage desorption: Elute the resin with an acid solution of 0.1-1% by mass to remove adsorbed copper, nickel, and zinc impurity ions; a2. Second-stage desorption: Elute the resin with an acid solution of 5-10% by mass to obtain the eluent rich in iron ions.

6. The method for iron resource recovery from electroplating sludge based on acid leaching-resin selective adsorption according to claim 5, characterized in that, In both the first-stage and second-stage desorption, the elution flow rate of the acid solution is 1-3 mL / min.

7. The method for iron resource recovery from electroplating sludge based on acid leaching-resin selective adsorption according to claim 5, characterized in that, The acid solution described in steps a1 and a2 is independently selected from sulfuric acid, nitric acid, or hydrochloric acid.

8. The method for iron resource recovery from electroplating sludge based on acid leaching-resin selective adsorption according to claim 1, characterized in that, The recrystallization in step S6 specifically involves: dissolving the crude iron salt crystal product by heating with water, evaporating and concentrating it again, cooling and crystallizing, filtering and drying to obtain the high-purity iron salt product.

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