Leaching method of calcium ions in calcium-containing solid waste

Abstract

The invention relates to the technical field of industrial waste recycling and carbon dioxide mineralization, and discloses a leaching method for calcium ions in calcium-containing solid waste. The method for leaching the calcium ions in the calcium-containing solid waste comprises the following steps that S1, the calcium-containing solid waste is subjected to pre-screening and ball milling, and solid waste micro powder is collected; s2, mixing the solid waste micro powder with a leaching agent, and reacting to obtain a calcium ion leaching solution; s3, introducing CO2 gas into the calcium ion leachate, reacting, and separating to obtain a calcium carbonate solid and a regenerated leaching agent; in the step S2, the leaching agent comprises protonated organic amine. According to the method for leaching the calcium ions in the calcium-containing solid waste, the leaching agent selectivity is good, the calcium ion leaching rate is high, the reaction condition is mild, ammonia escape in the leaching process is little, and environment friendliness is achieved; by introducing CO2 gas into the calcium-containing leachate, the leaching agent can be quickly regenerated, and the cyclic stability of the regenerated leaching agent is good.

Description

Technical Field

[0001] The invention relates to the technical field of industrial waste resource utilization and carbon dioxide mineralization, and in particular to a method for leaching calcium ions from calcium-containing solid waste. Background Art

[0002] Calcium-containing solid wastes such as carbide slag, fly ash and steel slag are generally alkaline, and the leaching of heavy metal ions in their components will cause great pollution to land and groundwater resources. Among them, carbide slag is mainly composed of calcium hydroxide, calcium carbonate, water, silicon dioxide, aluminum hydroxide and carbon slag; the main source is the process of preparing acetylene gas by hydrolysis of carbide when producing polyvinyl chloride (PVC) by coal-based carbide method. Due to the large output of polyvinyl chloride produced by coal-based carbide method, the discharge of carbide slag is also large. At present, it is usually landfilled or stored, but its high alkalinity can easily cause environmental pollution, and there is also a phenomenon of waste of land and calcium resources.

[0003] Calcium carbide slag has fine particle size and high reactivity. Traditional large-scale consumption is mainly used to replace limestone to prepare cement and other construction materials, but it is limited by factors such as market saturation and geographical regions. Calcium carbide slag is strongly alkaline and has good solubility. It has excellent performance in environmental treatment processes such as acidic wastewater and flue gas desulfurization, and can replace calcium-based absorbents for flue gas desulfurization. The main component of calcium carbide slag is calcium hydroxide, which can be used to prepare high-value products such as calcium oxide and calcium carbonate. However, due to the influence of impurities in calcium carbide slag, calcium ions need to be leached and purified, resulting in high processing costs. In summary, the resource utilization of calcium carbide slag has significant economic and environmental benefits, while the harmful components and impurities in calcium carbide slag are the main factors limiting the utilization of calcium carbide slag.

[0004] At present, the most typical process for preparing calcium carbonate using carbide slag as raw material is to use ammonium salt solution and acid to leach calcium ions, then adjust the pH of the leachate to alkaline and further react with CO 2 The reaction generates calcium carbonate precipitation. However, ammonium salt solution and acid leaching face the problem that the leaching solvent cannot be recycled. The process of using ammonium salt leaching will also have serious ammonia escape, and the leaching solution needs to be repeatedly replenished, which is harmful to the environment. The acid solution leaching process will produce a large amount of wastewater, causing secondary pollution.

[0005] Sucrose can react with calcium hydroxide to form sucrose calcium complex. Lime is often used as a clarifier in the sugar production process to remove pigments, suspended particles, etc. in sugar juice. Sucrose does not react with other impurities in carbide slag, such as silicon dioxide, iron oxide, calcium carbonate, etc. Therefore, sucrose can be used as an environmentally friendly and biologically derived leaching agent to extract calcium ions from carbide slag. It can also be used to extract calcium ions from carbide slag through the reaction of sucrose calcium with CO 2Although sucrose can avoid the disadvantages of ammonium salt or acid leaching agents as a leaching agent, the solution viscosity of sucrose calcium complex is relatively large. When the sucrose concentration is high, the fluidity of the leaching solution will deteriorate. 2 The reaction efficiency of the regeneration process is limited. Therefore, the liquid-to-solid ratio of the sucrose leaching process is generally controlled at a high ratio, the calcium ion concentration in the leaching solution is low, the solvent circulation volume is large, and the leaching energy consumption is high. At present, there is still a lack of environmentally friendly and efficient methods for leaching calcium ions from carbide slag, which limits the resource utilization of carbide slag. Summary of the invention

[0006] The present invention aims to solve at least one of the above-mentioned technical problems existing in the prior art. To this end, the object of the present invention is to provide a method for leaching calcium ions from calcium-containing solid waste.

[0007] The basic principle of the present invention is described as follows:

[0008] The present invention removes large-sized coarse particles such as agglomerated materials and sintered coke from the calcium-containing solid waste by pre-screening, and then obtains small-size solid waste powder by ball milling; a specific leaching agent protonated organic amine (RNH + ), directly extract the calcium ions in the solid waste powder, Ca(OH) 2 It can be selectively leached by protonated organic amine to obtain a leachate containing calcium ions. The reaction process is shown in Formula I:

[0009] 2RN + +Ca(OH) 2 →Ca 2+ +2RN+2H 2 O, formula I;

[0010] CO is introduced into the calcium ion-containing leaching solution. 2 Gas, CO 2 Ca in the leaching solution 2+ The reaction generates calcium carbonate precipitation, and the leaching agent is regenerated simultaneously. After filtering and separating the calcium carbonate solid, the regenerated protonated organic amine can be directly used for the cyclic leaching of calcium ions in solid waste micropowder. 2 The reaction process of regenerating protonated organic amine is shown in Formula II:

[0011] CO 2 +Ca 2+ +2RN+H 2 O→CaCO 3 ↓+2RNH + , formula II.

[0012] In order to achieve the above object, the technical solution adopted by the present invention is:

[0013] The present invention provides a method for leaching calcium ions from calcium-containing solid waste, comprising the following steps:

[0014] S1. Pre-screening and ball-milling the calcium-containing solid waste to collect solid waste powder;

[0015] S2, mixing the solid waste powder with a leaching agent, reacting to obtain a calcium ion leaching solution;

[0016] S3, introducing CO into the calcium ion leaching solution 2 gas, react, and separate to obtain calcium carbonate solid and regenerated leaching agent;

[0017] In the step S2, the leaching agent includes a protonated organic amine.

[0018] Preferably, the calcium-containing solid waste includes at least one of carbide slag, fly ash, steel slag, lime kiln dust and phosphogypsum; further preferably, the calcium-containing solid waste is carbide slag.

[0019] Preferably, the carbide slag comprises the following chemical components in mass percentage: 65-80% Ca(OH) 2 、10-20% CaCO 3 1-10% SiO 2 , 1-10%C, 1-5%Al 2 O 3 1-5% H 2 O; Further preferably, the carbide slag comprises the following chemical components by mass percentage: 65-75% Ca(OH) 2 、15-20% CaCO 3 1-5% SiO 2 , 1-5%C, 1-3%Al 2 O 3 1-3% H 2 O.

[0020] Preferably, in step S1, the aperture of the pre-screening screen is 4-5 meshes.

[0021] Preferably, in step S1, the ball milling time is 5-10 min.

[0022] Preferably, in step S1, the particle size of the solid waste fine powder is 48-115 mesh; further preferably, the particle size of the solid waste fine powder is 50-100 mesh.

[0023] Preferably, in step S2, the mass ratio of the leaching agent to the solid waste powder is (10-30):1; further preferably, the mass ratio of the leaching agent to the solid waste powder is (15-25):1.

[0024] Preferably, in step S2, the reaction temperature is 20-60°C; further preferably, the reaction temperature is 20-30°C.

[0025] Preferably, in step S2, the reaction time is 30-60 min; more preferably, the reaction time is 50-60 min.

[0026] Preferably, in step S2, the reaction process is assisted by stirring.

[0027] Preferably, the stirring speed is 300-500 r / min; further preferably, the stirring speed is 350-450 r / min.

[0028] Preferably, in step S2, after the reaction is completed, the step of standing, settling, filtering and separating to obtain a calcium ion leachate is further included.

[0029] Preferably, the protonation degree of the protonated organic amine is 40-60%.

[0030] Preferably, in the protonated organic amine, the concentration of the organic amine is 1-3 mol / L; further preferably, the concentration of the organic amine is 1-2 mol / L.

[0031] Preferably, among the protonated organic amines, the organic amine includes at least one of alcohol amines and substituted anilines; further preferably, the organic amine includes at least one of N-methyldiethanolamine, N,N-dimethylethanolamine, N,N-dimethylpropanolamine, N,N-diethylethanolamine, N-ethyldiethanolamine, N,N-dimethylcyclohexylamine, N,N-dimethylaniline and N,N-diethylaniline; further preferably, the organic amine is N-methyldiethanolamine (MDEA).

[0032] Preferably, the proton donor of the protonated organic amine includes a proton acid that does not react with calcium ions to form a precipitate; further preferably, the proton donor includes at least one of hydrochloric acid, nitric acid, formic acid, acetic acid, propionic acid, butyric acid, oxalic acid, citric acid, malic acid, and maleic acid; further preferably, the proton donor is hydrochloric acid (HCl).

[0033] Preferably, the leaching agent is N-methyldiethanolamine protonated with hydrochloric acid, the protonation degree is 40-60%, and the concentration of the organic amine is 1-2 mol / L.

[0034] Preferably, the protonated organic amine is prepared by a method comprising the following steps:

[0035] The organic amine, the proton donor and deionized water are mixed and stirred to make the organic amine and the proton donor dispersed evenly to obtain the protonated organic amine.

[0036] Preferably, in step S3, the CO 2 The concentration of gas is ≥99%.

[0037] Preferably, in step S3, the reaction temperature is 20-30°C.

[0038] Preferably, in step S3, the reaction is carried out in CO 2 The process is carried out in an absorption reactor; the rotation speed of the reactor is 180-230 r / min.

[0039] Preferably, in step S3, the reaction ends when the pH of the leaching solution is less than 9; further preferably, the reaction ends when the pH of the leaching solution is 7-9.

[0040] Preferably, in step S3, the regenerated leaching agent is repeatedly used to leach calcium ions from solid waste fine powder.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] The method for leaching calcium ions from calcium-containing solid waste provided by the present invention has good leaching agent selectivity, high calcium ion leaching rate, mild reaction conditions, high safety factor in the operation process, less ammonia escape in the leaching process, and is environmentally friendly; by introducing CO into the calcium-containing leaching solution 2 Gas can achieve rapid regeneration of the leaching agent, and the regenerated leaching agent has good cyclic stability; the simultaneous leaching of calcium ions and regeneration of the leaching agent can simplify the steps and effectively reduce costs; the regeneration of the leaching agent can achieve CO 2 It can reduce consumption and obtain insoluble calcium carbonate products, which has good environmental and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 The figure is a schematic flow chart of a method for leaching calcium ions from calcium-containing solid waste according to an embodiment. DETAILED DESCRIPTION

[0044] The present invention is further described in detail below by specific examples. Unless otherwise specified, the raw materials, reagents or devices used in the examples and comparative examples can be obtained from conventional commercial sources or can be obtained by prior art methods. Unless otherwise specified, the experiments or test methods are conventional methods in the art.

[0045] Figure 1 The schematic diagram of the process of leaching calcium ions from calcium-containing solid waste is shown in the following. Figure 1 , the method for leaching calcium ions from calcium-containing solid waste in the embodiment is described.

[0046] The chemical composition of carbide slag in the embodiments and comparative examples is shown in Table 1:

[0047] Table 1 Chemical composition of carbide slag in the embodiments and comparative examples

[0048] chemical composition Mass percentage content <![CDATA[H 2 The]]> 2.7％ <![CDATA[SiO 2 ]]> 4.3％ <![CDATA[Al 2 THE 3 ]]> 1.5％ C 4.3％ <![CDATA[Ca(OH) 2 ]]> 71.9％ <![CDATA[CaCO 3 ]]> 15.3％

[0049] Example 1

[0050] This embodiment provides a method for selectively leaching calcium ions from carbide slag using protonated organic amines, the steps being as follows:

[0051] S11, pre-screening and impurity removal of carbide slag: pre-screen the carbide slag raw material through a 5-mesh screen to remove coarse particles such as large-sized agglomerated materials and sintered coke, and collect the screened carbide slag;

[0052] S12, carbide slag ball milling: put the sieved carbide slag particles into a ball mill and mill for 10 minutes, send the milled powder into a 100-mesh sieving machine to separate the silicate phase and coke that are difficult to break, and collect the sieved carbide slag powder;

[0053] S21. Prepare a protonated organic amine solution: add a certain amount of MDEA, hydrochloric acid and deionized water into a beaker, stir thoroughly to make the MDEA and hydrochloric acid dispersed evenly, prepare the MDEA concentration to be 2 mol / L, the protonation degree to be 60%, and let stand for use;

[0054] S22, calcium ion leaching: the protonated organic amine solution and the carbide slag powder are mixed in a mass ratio of 20:1, and the mixture is stirred at a speed of 400 r / min at 25° C. for 60 min. The solution after the reaction is allowed to stand, settle, and filter to obtain a calcium ion leaching solution;

[0055] S31, protonated organic amine solution regeneration: the separated clarified calcium ion leachate is transferred to CO 2 In the absorption reactor, the reaction temperature was set at 25°C, the rotation speed was set at 200 r / min, and 99% CO was introduced. 2 When the pH value of the solution is less than 9, stop introducing CO 2 gas, filtering the formed white slurry to separate the calcium carbonate solid, and obtaining a regenerated protonated organic amine solution;

[0056] S41, cyclic leaching: the regenerated protonated organic amine solution is subjected to calcium ion leaching and solution regeneration for 5 times according to steps S4 and S5.

[0057] The analysis was performed to detect the calcium ion leaching rate of the protonated organic amine solution when it was used for the first time, the calcium ion leaching rate of the regenerated protonated organic amine solution after leaching once and then leaching for 5 times, and the degradation rate of the regenerated protonated organic amine solution after 5 cycles of use.

[0058] Example 2

[0059] This embodiment provides a method for selectively leaching calcium ions from carbide slag using protonated organic amines, the steps being as follows:

[0060] S11, pre-screening and impurity removal of carbide slag: pre-screen the carbide slag raw material through a 5-mesh screen to remove coarse particles such as large-sized agglomerated materials and sintered coke, and collect the screened carbide slag;

[0061] S12, carbide slag ball milling: put the sieved carbide slag particles into a ball mill and mill for 10 minutes, send the milled powder into a 50-mesh sieving machine to separate the silicate phase and coke that are difficult to break, and collect the sieved carbide slag powder;

[0062] S21. Prepare a protonated organic amine solution: add a certain amount of MDEA, hydrochloric acid and deionized water into a beaker, stir thoroughly to make the MDEA and hydrochloric acid dispersed evenly, prepare the MDEA concentration to be 1 mol / L, the protonation degree to be 40%, and let stand for use;

[0063] S22, calcium ion leaching: the protonated organic amine solution and the carbide slag powder are mixed in a mass ratio of 20:1, and the mixture is stirred at a speed of 400 r / min at 25° C. for 60 min. The solution after the reaction is allowed to stand, settle, and filter to obtain a calcium ion leaching solution;

[0064] S31, protonated organic amine solution regeneration: the separated clarified calcium ion leachate is transferred to CO 2 In the absorption reactor, the reaction temperature was set at 25°C, the rotation speed was set at 200 r / min, and 99% CO was introduced. 2 When the pH value of the solution is less than 9, stop introducing CO 2 gas, filtering the formed white slurry to separate the calcium carbonate solid, and obtaining a regenerated protonated organic amine solution;

[0065] S41, cyclic leaching: the regenerated protonated organic amine solution is subjected to calcium ion leaching and solution regeneration for 5 times according to steps S4 and S5.

[0066] The analysis was performed to detect the calcium ion leaching rate of the protonated organic amine solution when it was used for the first time, the calcium ion leaching rate of the regenerated protonated organic amine solution after leaching once and then leaching for 5 times, and the degradation rate of the regenerated protonated organic amine solution after 5 cycles of use.

[0067] Comparative Example 1

[0068] This comparative example provides a method for selectively leaching calcium ions from carbide slag using ammonium chloride solution, the steps are as follows:

[0069] S11, pre-screening and impurity removal of carbide slag: pre-screen the carbide slag raw material through a 5-mesh screen to remove coarse particles such as large-sized agglomerated materials and sintered coke, and collect the screened carbide slag;

[0070] S12, carbide slag ball milling: put the sieved carbide slag particles into a ball mill and mill for 10 minutes, send the milled powder into a 100-mesh sieving machine to separate the silicate phase and coke that are difficult to break, and collect the sieved carbide slag powder;

[0071] S21, calcium ion leaching: ammonium chloride solution and carbide slag powder are mixed in a mass ratio of 20:1, stirred at 400 r / min at 25°C for 60 min, and the reaction solution is allowed to stand, settle, and filter to obtain a calcium ion leachate;

[0072] S31, ammonium chloride solution regeneration: the separated clarified calcium ion leachate is transferred to CO 2 In the absorption reactor, the reaction temperature was set at 25°C, the rotation speed was set at 200 r / min, and 99% CO was introduced. 2 When the pH value of the solution is less than 9, stop introducing CO 2 gas, and filtering the formed white slurry to separate the calcium carbonate solid to obtain a regenerated ammonium chloride solution;

[0073] S41, cyclic leaching: the regenerated ammonium chloride solution is subjected to calcium ion leaching and solution regeneration for 5 times according to steps S3 and S4.

[0074] The analysis was conducted to detect the calcium ion leaching rate of the ammonium chloride solution when it was first used, the calcium ion leaching rate of the regenerated ammonium chloride solution after leaching once and then leaching for 5 cycles, and the degradation rate of the regenerated ammonium chloride solution after 5 cycles.

[0075] In Examples 1 and 2 and Comparative Example 1, the calcium ion leaching rate of the leachate when it is first used, the calcium ion leaching rate of the regenerated leachate obtained after leaching once and then undergoing 5 cycles of leaching reaction, and the degradation rate of the leachate for the 5th time are shown in Table 2:

[0076] Table 2 Performance test results of the leachate and regenerated leachate in Examples 1, 2 and Comparative Example 1

[0077]

[0078] Table 2 shows the performance test results of the leachate and the regenerated leachate in Examples 1, 2 and Comparative Example 1. Compared with Example 2, the particle size of the carbide slag powder obtained in step S12 of Example 1 is smaller, and the MDEA concentration in the hydrochloric acid protonated MDEA solution prepared in step S21 is higher. The data in Table 2 show that the calcium ion leaching rate of the leachate in Example 1 reaches 81.76%, and the calcium ion leaching rate of the regenerated leachate after 5 cycles reaches 78.93%. The leaching effect of calcium ions and the cyclic leaching effect of the regenerated leachate are better than those of Example 2, but the degradation rate of the regenerated leachate in Example 1 is slightly higher than that of Example 2. Overall, the leaching method in Example 1 shows excellent calcium ion leaching effect and good leaching agent cyclic stability.

[0079] The difference between Comparative Example 1 and Example 1 is that ammonium chloride solution is used instead of MDEA protonated with hydrochloric acid as the leaching agent. It can be seen that the initial calcium ion leaching rate of the ammonium chloride solution is 78.14%, which is slightly lower than Example 1 (81.76%); after the regenerated leachate is leached for 5 cycles, the calcium ion leaching rate in Comparative Example 1 is 70.55%, and the leaching rate decreases rapidly; the degradation rate of the regenerated leachate after 5 cycles is close to 10%, and the leaching agent is severely degraded, indicating that when ammonium chloride solution is used as the leaching agent, the initial leaching has a relatively good leaching effect, but there is a serious ammonia escape phenomenon in the ammonium chloride leaching process. The degradation rate of ammonium chloride reaches 9.71% after only 5 cycles, and the cycle stability is poor. Not only does it need to replenish the leaching agent in time to ensure the leaching effect, but there is also a large environmental hazard. The calcium ion leaching rate of the leachate in Example 2 is slightly lower than that in Comparative Example 1, but the calcium ion leaching rate of the regenerated leachate after 5 cycles and the cyclic stability of the regenerated leachate are better than those in Comparative Example 1. Overall, the method provided by the present invention can achieve a leaching effect that is better than that of the leaching method using ammonium salt solution as the leaching agent.

[0080] The method for leaching calcium ions from calcium-containing solid waste provided by the present invention can efficiently leach calcium ions from calcium-containing solid wastes such as carbide slag. Compared with the leaching method using ammonium salt solution as the leaching agent, the method has good selectivity, high leaching rate, less ammonia escape, and is environmentally friendly. The protonated organic amine of the leaching agent can be introduced into the leaching agent by CO 2 Regeneration, good leaching agent cycle stability, and can achieve CO 2The invention can seal and obtain calcium carbonate products, and has high environmental and economic benefits. Compared with the method of using acidic substances as leaching agents, the leaching process does not produce a large amount of acidic wastewater, which is environmentally friendly. Compared with the method of using sucrose as the leaching agent, the protonated organic amine has high solubility in aqueous solution and does not directly combine with calcium ions. The viscosity of the leachate is not greatly affected by the concentration of calcium ions, and the applicable operation range is wider. Compared with the existing calcium-containing solid waste leaching and mineralization technology using protonated organic amine as the main leaching agent, the leaching method provided by the invention can realize the simultaneous leaching of calcium ions and regeneration of the leaching agent, and there is no need to regenerate the leaching agent by electrodialysis or the like. The steps are simple and cost-saving. It is a clean and green new process for leaching calcium ions from calcium-containing solid waste.

Claims

1. A method for leaching calcium ions from calcium-containing solid waste, characterized in that: The following steps are involved: S1. Pre-screening and ball-milling the calcium-containing solid waste to collect solid waste powder; S2, mixing the solid waste powder with a leaching agent, reacting to obtain a calcium ion leaching solution; S3, introducing CO2 gas into the calcium ion leachate to react and separate to obtain calcium carbonate solid and regenerated leaching agent; In the step S2, the leaching agent includes a protonated organic amine.

2. The leaching method according to claim 1, characterized in that The calcium-containing solid waste includes at least one of carbide slag, fly ash, steel slag, lime kiln dust and phosphogypsum.

3. The leaching method according to claim 2, characterized in that The carbide slag includes the following chemical components in mass percentage: 65-80% Ca(OH)2, 10-20% CaCO3, 1-10% SiO2, 1-10% C, 1-5% Al2O3, and 1-5% H2O.

4. The leaching method according to claim 1, characterized in that In the step S1, the particle size of the solid waste fine powder is 48-115 mesh.

5. The leaching method according to claim 1, characterized in that In the step S2, the mass ratio of the leaching agent to the solid waste fine powder is (10-30):1; And / or, the reaction temperature is 20-60°C; And / or, the reaction time is 30-60 min.

6. The leaching method according to claim 5, characterized in that The protonation degree of the protonated organic amine is 40-60%; And / or, in the protonated organic amine, the concentration of the organic amine is 1-3 mol / L.

7. The leaching method according to any one of claims 1 to 6, characterized in that: In the protonated organic amine, the organic amine includes at least one of an alcohol amine and a substituted aniline; And / or, the proton donor of the protonated organic amine includes a protonic acid that does not react with calcium ions to form a precipitate.

8. The leaching method according to claim 7, characterized in that: The organic amine includes at least one of N-methyldiethanolamine, N,N-dimethylethanolamine, N,N-dimethylpropanolamine, N,N-diethylethanolamine, N-ethyldiethanolamine, N,N-dimethylcyclohexylamine, N,N-dimethylaniline and N,N-diethylaniline; And / or, the proton donor includes at least one of hydrochloric acid, nitric acid, formic acid, acetic acid, propionic acid, butyric acid, oxalic acid, citric acid, malic acid, and maleic acid.

9. The leaching method according to claim 1, characterized in that: In step S3, the concentration of the CO2 gas is ≥ 99%; And / or, the reaction temperature is 20-30°C; And / or, the reaction ends when the pH of the leaching solution is less than 9.

10. The leaching method according to claim 1, characterized in that: In step S3, the regenerated leaching agent is repeatedly used to leach calcium ions from solid waste fine powder.

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