Method for removing copper ions in strongly acidic wastewater by ascorbic acid induced vulcanization method

Abstract

The invention discloses a method for removing copper ions in strongly acidic wastewater by an ascorbic acid induced vulcanization method. The method comprises the following steps: adding ascorbic acid into the strongly acidic wastewater containing copper ions, then adding a vulcanizing agent, stirring for reaction, and removing precipitates to obtain the treated wastewater. The ascorbic acid is added, so that the removal rate and the precipitation efficiency of the copper ions in the wastewater are remarkably improved.

Description

Technical Field

[0001] The invention belongs to the technical field of sewage treatment, and in particular relates to a method for removing copper ions in strongly acidic wastewater by using an ascorbic acid-induced sulfidation method. Background Art

[0002] In the process of metal electroplating, mining and smelting, high-concentration copper-containing wastewater containing a large amount of acidic substances is produced. These wastewaters are extremely acidic (pH <4). Copper is most often present in acidic wastewater in the form of Cu(Ⅱ). Excessive intake of copper can cause serious toxicological problems, such as vomiting or convulsions. Therefore, a large amount of copper in acidic wastewater should be separated and recovered as much as possible. Compared with other commonly used technologies, due to the low solubility product of CuS (Ksp = 6.3×10 -36 ), the sulfide precipitation method has a strong selectivity for the removal of copper in aqueous solution.

[0003] The sulfidation precipitation method refers to a method of adding a sulfiding agent to wastewater to react with the metal in the wastewater to form a precipitate, thereby removing or recovering the metal. There are many commonly used sulfiding agents, such as H2S, NaHS, and Na2S. In addition to fast reaction and rapid sedimentation, the biggest advantage of the sulfidation precipitation method is the reuse value of the effluent and precipitate. The sulfidation process does not consume the acidity of the raw water, and the effluent can be reused or used to produce waste acid.

[0004] Cu(II) and S(-II) react very quickly in solution, and copper sulfide precipitation can be quickly formed after the addition of sulfiding agent. However, the dosage of sulfiding agent in the existing process is excessive, and excessive sulfiding agent is very easy to form hydrogen sulfide gas under acidic conditions, causing secondary pollution. And because the copper sulfide particles are relatively fine, the solid-liquid separation effect is poor, and additional processes to promote sedimentation, such as ultraviolet irradiation and coagulation, are often required. Therefore, it is very necessary to develop new technologies to achieve efficient removal of Cu(II) and efficient sedimentation of CuS while reducing the dosage of sulfiding agent. Summary of the invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for removing copper ions from strongly acidic wastewater by ascorbic acid-induced sulfidation; the method for removing copper ions from strongly acidic wastewater of the present invention uses less sulfiding agent and has a fast coagulation rate. Ascorbic acid is an environmentally friendly reducing agent widely used in industry and has broad scientific research applications and practical application prospects.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] The present invention provides a method for removing copper ions in strongly acidic wastewater by using an ascorbic acid-induced sulfidation method, comprising the following steps:

[0008] Ascorbic acid is added to the strongly acidic wastewater containing copper ions, and then a sulfiding agent is added to stir the reaction, and the precipitate is removed to obtain the treated wastewater.

[0009] Preferably, the pH of the copper ion-containing strongly acidic wastewater is 2-4. In particular, the coagulation rate is faster when the pH is 2.

[0010] Preferably, the molar ratio of ascorbic acid to copper ions is (0.5-1.5):1;

[0011] Preferably, the stirring rate when adding ascorbic acid is 50-100 rpm. A lower stirring rate is used to avoid mixing in too much air.

[0012] Preferably, the sulfiding agent is at least one of H2S, NaHS, and Na2S;

[0013] Preferably, the molar ratio of the sulfiding agent to the copper ion is (0.2-0.8):1; especially when the molar ratio is above 0.5, a 100% copper ion removal rate and a faster coagulation rate are achieved.

[0014] Preferably, the stirring rate when adding the sulfiding agent is 350-400 rpm. A higher stirring rate allows sodium sulfide to diffuse rapidly in the wastewater.

[0015] Preferably, the stirring reaction rate is 50-100 rpm;

[0016] Preferably, the stirring reaction time is 30-100 min.

[0017] More preferably, the stirring reaction time is 60-90 min.

[0018] Preferably, the strongly acidic wastewater containing copper ions also includes SO4 2- . Wastewater contains SO4 2- Not only does it not reduce the removal effect of copper ions, but it also increases the coagulation rate. The wastewater treatment method of the present invention has a wider application range and can regulate the wastewater components to improve the wastewater treatment effect.

[0019] Further preferably, SO4 2- The concentration is 30-100mM.

[0020] Preferably, the copper ion-containing strongly acidic wastewater also includes Fe 2+ . Wastewater contains Fe 2+ Not only does it not reduce the removal effect of copper ions, but it also increases the coagulation rate at low concentrations. The wastewater treatment method of the present invention has a wider range of applications and can regulate wastewater components to improve the wastewater treatment effect.

[0021] More preferably, Fe2+ The concentration is 30-100mg / L.

[0022] Preferably, the precipitate is removed by filtration.

[0023] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows:

[0024] The method for removing copper ions in strongly acidic wastewater of the present invention improves the removal effect of copper ions by adding ascorbic acid, reduces the amount of sulfiding agent, and improves the coagulation rate; appropriately increasing the amount of sulfiding agent can improve the copper ion removal rate and the coagulation rate; and the coagulation rate is faster when the pH is 2.

[0025] The method for removing copper ions from strongly acidic wastewater of the present invention has strong adaptability, low requirements for wastewater, and can contain other components such as SO4 2- , Fe 2+ etc.; it can also regulate SO4 in wastewater 2- , Fe 2+ content, increasing the coagulation rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The copper ion wastewater treatment effect diagram of Example 1, Comparative Example 1 and Comparative Example 2; (a) Cu(II) removal kinetics; (b) Suspension image after the reaction of the AA system in Comparative Example 1; (c) Suspension image after the reaction of the AA system in Example 1.

[0027] Figure 2 The copper ion wastewater treatment effect diagram of Example 2-5; (a) different sulfur-copper ratio, pH, SO4 2- and Fe(II) concentrations; (b) copper sulfide compound particle coagulation rate; (c) copper sulfide compound particle hydrodynamics; the green line indicates the multiple increase in removal rate and coagulation rate under AA conditions. DETAILED DESCRIPTION

[0028] The present invention will be further described in detail below in conjunction with the examples, but the embodiments of the present invention are not limited thereto.

[0029] The wastewater in the following examples is simulated wastewater obtained by dissolving copper chloride in water and adding hydrochloric acid to adjust the pH.

[0030] Example 1

[0031] This embodiment provides a method for removing copper ions in strongly acidic wastewater by ascorbic acid-induced sulfidation, comprising the following steps:

[0032] Step 1: Add ascorbic acid to wastewater with a pH of 2 and a copper ion content of 100 mg / L at room temperature, and control the stirring rate at 100 rpm to avoid mixing too much air. The molar ratio of copper ions to ascorbic acid in the wastewater is controlled at 1.6:1;

[0033] Step 2: After the stirring rate is increased to 400 rpm in advance, sodium sulfide solution (1000 mg / L) is quickly added to allow the sodium sulfide solution to diffuse rapidly in the wastewater. The molar ratio of copper ions to sodium sulfide in the wastewater is controlled at 2:1;

[0034] Step 3: After stirring at 400 rpm for 5 min, the stirring rate was set to 100 rpm and stirring was continued for 90 min. The concentration of copper ions in the solution was tested at different time points.

[0035] like Figure 1 As shown, after the reaction is completed, the removal rate of copper in the strongly acidic copper-containing wastewater reaches 100%; within 0-20 minutes, the precipitate coagulation rate k = 2.78nm / s.

[0036] Example 2

[0037] This embodiment provides a method for removing copper ions in strongly acidic wastewater by ascorbic acid-induced sulfidation. The difference from Embodiment 1 is that the S / Cu molar ratio in step 2 is different, namely 0.2, 0.3 and 0.4, respectively, and the rest is the same as Embodiment 1.

[0038] like Figure 2 As shown, when the S / Cu molar ratio is 0.2, 0.3 and 0.4, after the reaction is completed, the removal rate of copper in the copper-containing wastewater is 41%, 64% and 81%, and the condensation rate (within 0-20min) is 1.49, 1.94 and 2.38nm / s, respectively. Compared with Example 1, the removal rate of copper under the conditions of S / Cu molar ratio of 0.2, 0.3 and 0.4 is 0.4, 0.6 and 0.8 times that under the condition of S / Cu molar ratio of 0.5, and the condensation rate is 0.5, 0.7 and 0.9 times that under the condition of S / Cu molar ratio of 0.5. It is proved that the S / Cu molar ratio should preferably be 0.5.

[0039] The sample without ascorbic acid was used as a control, and the rest of the process was the same as above.

[0040] like Figure 2As shown, when the S / Cu molar ratios were 0.2, 0.3 and 0.4, respectively, after the reaction was completed, the removal rates of copper in the copper-containing wastewater were 24%, 31% and 43%, and the condensation rates (within 0-20 min) were 0.72, 0.77 and 0.74 nm / s, respectively. The removal rate of copper ions in the copper-containing wastewater with the same S / Cu molar ratio in the above AA system was twice that of the control group, and the condensation rates of the AA system were 2.1, 2.5 and 3.2 times that of the control group, respectively.

[0041] Example 3

[0042] This embodiment provides a method for removing copper ions in strongly acidic wastewater by ascorbic acid-induced sulfidation. The difference from Embodiment 1 is that the pH is different, namely, 3 and 4, respectively. The pH is pre-adjusted using 0.1M HCl / NaOH before step 1. The rest is the same as Embodiment 1.

[0043] like Figure 2 As shown, under the conditions of pH 3 and 4, after the reaction, the removal rate of copper in the copper-containing wastewater can reach 100%, and the condensation rate (0-20min) is 1.65 and 1.52nm / s respectively. Compared with Example 1, the removal rate of copper in the copper-containing wastewater under the conditions of pH 3 and 4 remains unchanged, both of which are 100%, while the condensation rate is 0.6 and 0.5 times that under the condition of pH 2. This proves that the pH condition should preferably be 2.

[0044] The sample without ascorbic acid was used as a control, and the rest of the process was the same as above.

[0045] like Figure 2 As shown, under the conditions of pH 3 and 4, after the reaction, the removal rate of copper in the copper-containing wastewater was 50%, and the coagulation rates (within 0-20 min) were 0.93 and 1.16 nm / s, respectively. The removal rate of copper ions in the copper-containing wastewater with the same pH in the above AA system was twice that of the control group, and the coagulation rates of the AA system were 1.8 and 1.3 times that of the control group, respectively.

[0046] It can be seen that when the pH of the wastewater solution is 3 and 4, the synergistic effect of ascorbic acid is still significant.

[0047] Example 4

[0048] This embodiment provides a method for removing copper ions from strongly acidic wastewater by ascorbic acid-induced sulfidation. The difference from Embodiment 1 is that SO4 2- The concentrations are different, namely 30, 60, and 100 mmol / L. Before step 1, a corresponding amount of Na2SO4 is added in advance and fully dissolved. The rest is the same as in Example 1.

[0049] like Figure 2 As shown, SO42- When the concentrations were 30, 60, and 100 mM, respectively, after the reaction, the removal rate of copper in the copper-containing wastewater was 100%, and the condensation rates (0-20 min) were 2.87, 3.27, and 3.52 nm / s, respectively. Compared with Example 1, SO4 2- The removal rate of copper in copper-containing wastewater with concentrations of 30, 60, and 100 mM remained unchanged, while SO4 2- The aggregation rates at concentrations of 60 and 100 mM were increased by 1.2 and 1.3 times, respectively, compared with Example 1.

[0050] The sample without ascorbic acid was used as a control, and the rest of the process was the same as above.

[0051] like Figure 2 As shown, SO4 2- When the concentrations were 30, 60, and 100 mM, respectively, after the reaction, the removal rate of copper in the copper-containing wastewater was 50%, and the condensation rates (0-20 min) were 0.72, 0.93, and 1.26 nm / s, respectively. 2- The removal rate of copper ions in wastewater containing copper ions of the same concentration was twice that of the control group, and the coagulation rates of the AA system were 4.0, 3.5, and 2.8 times that of the control group, respectively.

[0052] It can be seen that when SO4 exists in the wastewater solution 2- When the ascorbic acid was added, the synergistic effect was still significant, and the copper ion removal effect was further improved.

[0053] Example 5

[0054] This embodiment provides a method for removing copper ions from strongly acidic wastewater by ascorbic acid-induced sulfidation. The difference from Embodiment 1 is that Fe 2+ The concentrations are different, namely 30, 60, and 100 mg / L. Before step 1, a corresponding amount of FeCl2 is added in advance and fully dissolved. The rest is the same as in Example 1.

[0055] like Figure 2 As shown, Fe 2+ After the reaction, the removal rate of copper ions in the solution of wastewater containing copper ions with a content of 30, 60, and 100 mg / L was 100%, and the condensation rates (within 0-20 min) were 2.93, 2.89, and 2.76 nm / s, respectively. Compared with Example 1, Fe 2+ The removal rate of copper in copper-containing wastewater with a content of 30, 60, and 100 mg / L remained unchanged at 100%, and the condensation rate was 2+ When the content is 30mg / L, the Fe 2+When the content was 60 and 100 mg / L, the coagulation rate remained basically unchanged. 2+ The copper ion removal effect can be improved to a certain extent.

[0056] The sample without ascorbic acid was used as a control, and the rest of the process was the same as above.

[0057] like Figure 2 As shown, Fe 2+ After the reaction, the removal rate of copper ions in the solution of wastewater containing copper ions with a content of 30, 60, and 100 mg / L was 50%, and the condensation rate (within 0-20 min) was 0.65, 0.58, and 0.59 nm / s, respectively. 2+ The removal rate of copper ions in the wastewater containing copper ions with the same content is twice that of the control group. 2+ The coagulation rate of wastewater containing copper ions with the same content is 4.5, 5.0 and 4.7 times that of the control group.

[0058] It can be seen that when Fe 2+ The synergistic effect of ascorbic acid is still significant.

[0059] Comparative Example 1

[0060] Compared with Example 1, this comparative example omitted step 1 and did not add ascorbic acid. The other steps were the same as Example 1.

[0061] like Figure 1 As shown, after the reaction is completed, the removal rate of copper ions in the wastewater can only reach 50%, and the removal rate of copper ions in Example 1 is twice that of Comparative Example 1. Precipitation is also formed during the reaction, but the condensation rate (within 0-20 min) of the formed precipitate is 0.66 nm / s, and Example 1 is 4.2 times the condensation rate of Comparative Example 1. This proves that the addition of ascorbic acid can increase the removal rate of copper by 1 times, and the condensation rate can be increased by 4.2 times.

[0062] Comparative Example 2

[0063] Compared with Example 1, this comparative example omits step 2 and does not add sodium sulfide. Other aspects are the same as Example 1.

[0064] like Figure 1 As shown, after the reaction, no precipitation was generated in the solution and the concentration of copper ions did not change. This proves that ascorbic acid itself has no precipitation effect on copper ions.

[0065] Data Analysis:

[0066] (1) Figure 1As shown, under the conditions of pH 2 and Cu(II) concentration of 100 ppm, when Na2S was added according to the Cu / S molar ratio of 2:1 in Comparative Example 1, the reaction became stable in about 30 minutes, and the removal rate of Cu(II) in the solution was 50%. In Comparative Example 2, only ascorbic acid was added, which had no effect on the removal of copper ions. While in Example 1, the Cu / S molar ratio was kept unchanged, and AA was added according to the Cu / AA molar ratio of 1.6:1. Within 15-30 minutes, all the Cu(II) in the solution would form a precipitate ( Figure 1 In a). Within 0-20 min, the hydraulic radius of the precipitate generated in the system with AA added in Example 1 is about 2250 nm, while the hydraulic radius of the control group without AA added in Comparative Example 1 is about 750 nm. The condensation rate k control =0.66, k AA =2.78. When the reaction was carried out for 90 min, it could be observed with the naked eye that in the system without AA, there were still a lot of black particles suspended in the solution ( Figure 1 b), while in the system with AA added, the black precipitate generated was deposited at the bottom of the reaction vessel ( Figure 1 c) in.

[0067] Therefore, ascorbic acid was pre-added to the copper ion-containing wastewater, and then the sulfiding agent Na2S was added. Compared with not adding ascorbic acid, the Cu(II) removal rate in the solution increased by 2 times and the precipitation rate increased by 4.2 times. The addition of ascorbic acid can not only improve the utilization rate of negative divalent sulfur, but also increase the coagulation rate of particle formation, and the precipitation effect is significantly improved.

[0068] (2) Figure 2 As shown in the figure, the different S / Cu molar ratios, pH, and coexistence of SO4 in the solution were investigated. 2- Concentration and Fe 2+ The effect of concentration on the effect and rate of copper ion sulfide deposition under the action of AA.

[0069] It can be seen that when AA is not added, Cu(II) in the solution forms precipitation with sulfur at a ratio of 1:1, that is, when S / Cu (mol / mol) = 0.2, the removal rate of Cu(II) in the solution is 20%; after adding AA, under different S / Cu molar ratios, pH, and coexistence of SO4 in the solution, the removal rate of Cu(II) in the solution is 20%. 2- Under the conditions of Fe(II) concentration and Fe(II) concentration, the removal rate of Cu(II) in the solution was twice that of the system without AA addition ( Figure 2 a) in the figure.

[0070] The dynamic light scattering particle size analyzer was used to detect the different S / Cu molar ratios, pH, and coexistence of SO4 in the solution within 20 minutes. 2-The change of hydrodynamic radius of copper-sulfur compound precipitation in solution under the conditions of concentration and Fe(II) concentration. 2- The experimental groups of Fe(II) concentration and AA concentration showed that the hydrodynamic radius increased more significantly after AA addition ( Figure 2 c) in.

[0071] Compared with the system without AA at pH 2, the hydraulic radius of copper sulfide precipitation increased significantly in the system with AA added, but the difference decreased at pH 3 and 4. The negative charge on the surface of copper sulfide particles is caused by the adsorption of negatively charged substances on the surface. For the AA system, the deprotonation reaction of dehydroascorbic acid (DHA) in aqueous solution will affect the surface charge of copper sulfide particles. The pKa value of DHA is about 8. The concentration of anions generated by the ionization of DHA in the solution increases with the increase of pH value, resulting in the stability of copper sulfide particles increasing with the increase of surface negative charge. In the solution with pH 2, H + At high concentrations, negative charges will be neutralized, which will reduce the absolute value of the particle zeta potential and reduce stability. Therefore, compared with the systems with pH 3 and 4, the copper sulfur compound particles in the AA system with pH 2 showed a higher aggregation rate and larger particle size.

[0072] The condensation rate of copper-sulfur compound precipitation within 20 minutes can be calculated from the measured hydrodynamic radius. When S / Cu (mol / mol) is in the range of 0.2-0.5 mol / mol, the growth multiple of the condensation rate increases first and then decreases with the increase of the ratio. When the pH is in the range of 2-4, the condensation rate decreases with the increase of pH. When SO4 2- When the concentration is in the range of 30-100mM, the condensation rate increases with the SO4 2- When the Fe(II) concentration is in the range of 30-100 mg / L, the coagulation rate remains basically unchanged as the Fe(II) concentration increases ( Figure 2 b) in the above.

[0073] The above embodiments are only preferred implementation modes of the present invention and are only used to explain the present invention rather than to limit the present invention. Any changes, substitutions, modifications, etc. made by those skilled in the art without departing from the spirit of the present invention should fall within the scope of protection of the present invention.

Claims

1. A method for removing copper ions from strongly acidic wastewater by ascorbic acid-induced sulfidation, characterized in that: The following steps are involved: Ascorbic acid is added to the strongly acidic wastewater containing copper ions, and then a sulfiding agent is added to stir the reaction, and the precipitate is removed to obtain the treated wastewater.

2. The method for removing copper ions from strongly acidic wastewater by ascorbic acid-induced sulfidation according to claim 1, characterized in that: The pH of the copper ion-containing strongly acidic wastewater is 2-4; The copper ion concentration in the copper ion-containing strongly acidic wastewater is 50-300 mg / L.

3. The method for removing copper ions from strongly acidic wastewater by ascorbic acid-induced sulfidation according to claim 1, characterized in that: The molar ratio of ascorbic acid to copper ions is (0.5-1.5):1; The stirring rate during the addition of ascorbic acid was 50-100 rpm.

4. The method for removing copper ions from strongly acidic wastewater by ascorbic acid-induced sulfidation according to claim 1, characterized in that: The sulfiding agent is at least one of H2S, NaHS and Na2S; The molar ratio of the sulfiding agent to the copper ion is (0.2-0.8):1; The stirring rate when adding the vulcanizing agent is 350-400 rpm.

5. The method for removing copper ions from strongly acidic wastewater by ascorbic acid-induced sulfidation according to claim 1, characterized in that: The stirring reaction rate is 50-100 rpm; The stirring reaction time is 30-100 min.

6. The method for removing copper ions from strongly acidic wastewater by ascorbic acid-induced sulfidation according to claim 1, characterized in that: The copper ion-containing strongly acidic wastewater also includes SO4 2- .

7. The method for removing copper ions from strongly acidic wastewater by ascorbic acid-induced sulfidation according to claim 6, characterized in that: SO4 2- The concentration is 30-100mM.

8. The method for removing copper ions from strongly acidic wastewater by ascorbic acid-induced sulfidation according to claim 1, characterized in that: The copper ion-containing strongly acidic wastewater also includes Fe 2+ .

9. The method for removing copper ions from strongly acidic wastewater by ascorbic acid-induced sulfidation according to claim 8, characterized in that: Fe 2+ The concentration is 30-100mg / L.

10. The method for removing copper ions from strongly acidic wastewater by ascorbic acid-induced sulfidation according to claim 1, characterized in that: The precipitate was removed by filtration.

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