A method for treating chlorine-containing waste acid water

Abstract

The present invention discloses a method for treating chlorine-containing waste acid water. Zinc suboxide or zinc calcine is added to the chlorine-containing waste water for neutralization. Different neutralizing agents are added to the chlorine-containing waste water for neutralization, followed by primary and secondary zinc precipitation. Sulfate radicals in the chlorine-containing waste water are completely recovered in the form of basic zinc sulfate, while chlorine remains in the waste water. This achieves the recycling of sulfuric acid and avoids chlorine enrichment and secondary dechlorination. No gypsum slag is generated during the treatment of chlorine-containing waste water by the present invention. The entire reaction process is mild, energy-efficient, safe, and environmentally friendly. The auxiliary materials used in the treatment method are low-cost, no expensive reagents or a new evaporation system are required, and the industrial output value is high and economical.

Description

Technical Field

[0001] The present invention relates to the technical field of chlorine-containing wastewater treatment, and in particular to a method for treating chlorine-containing waste acid water. Background Art

[0002] More than 75% of my country's refined zinc is produced through the hydrometallurgical zinc smelting process, and recycled zinc production accounts for about 20-30% of the total refined zinc production. Due to the depletion of high-grade mineral resources and the difficulty of mining due to the prevalence of poor-grade ores and the scarcity of rich ores, recycled zinc raw materials have attracted increasing attention.

[0003] Recycled zinc raw materials include zinc slag, zinc ash, crude zinc oxide, flue dust, gas sludge / ash, zinc-containing smoke dust, and other zinc-containing materials. These are rich in valuable metals such as zinc, lead, and indium, and have high recycling value. However, their high fluorine and chlorine content makes the recycling process long, difficult, and complex, limiting their large-scale use.

[0004] There are two main methods for removing fluorine and chlorine from recycled zinc raw materials: pyrolysis and wet dechlorination. Pyrolysis is based on the difference in saturated vapor pressure between substances, achieving evaporative separation at a certain temperature. The main equipment includes rotary kilns and multi-hearth furnaces. Chinese patent CN102634676A discloses a method for defluorination, dechlorination, and dearsenicization of low-grade zinc oxide using rotary kiln reduction roasting. Low-grade zinc oxide raw material is added to a rotary kiln and roasted under high temperature and slightly negative pressure inside the kiln. Fluorine removal rates reach 92.4% and chlorine removal rates reach 85%. Wet dechlorination methods mainly include alkaline washing, copper slag dechlorination, bismuth salt dechlorination, and ion exchange dechlorination. Chinese patent: CN101492772A discloses an industrial ion exchange method for removing fluorine and chlorine from wet zinc smelting. The technology uses anion exchange resin D201 to selectively adsorb fluorine and chlorine in the solution, with a chlorine removal efficiency of greater than 80% and a fluorine removal efficiency of greater than 50%. A 10% sulfuric acid solution is then used as a desorbent to desorb the fluorine and chloride ions adsorbed by the resin into the desorbed liquid, allowing the resin to be regenerated.

[0005] Compared with the above-mentioned copper slag dechlorination and bismuth salt dechlorination, the use of ion exchange dechlorination requires less investment, high operating efficiency and low cost of use. However, there are also large amounts of wastewater, high acidity of the post-analysis liquid, and difficulty in treatment. Some companies choose to use lime to neutralize the post-analysis liquid, resulting in a large amount of hazardous waste gypsum slag, which is difficult to dispose of. Or soda ash is used to neutralize the post-analysis liquid, and the neutralized liquid is then put into wastewater treatment. Although the generation of gypsum slag is avoided, the treatment cost is high and all sulfate ions are lost in the wastewater. Chinese patent: CN104529036A discloses a dechlorination method and device for ion exchange dechlorination wastewater, which uses a strong oxidant potassium permanganate for oxidation to convert liquid chloride ions into gaseous chlorine gas, and then transfers the chloride ions to an absorption liquid to generate ferric chloride. The liquid after the chloride ion transfer is adsorbed to remove residual chlorine, and the adsorbed liquid is returned as a desorbent to recover sulfuric acid. The oxidant potassium permanganate used in this method is expensive, the disposal cost is high, highly toxic chlorine gas is generated in the intermediate process, and management and control are difficult. The by-product ferric chloride is not easy to sell. Chinese patent CN105274342A discloses a process for producing zinc sulfate monohydrate using waste acid and waste zinc slag. The process involves leaching copper-cadmium slag from the solution after ion exchange analysis, which is then purified and evaporated to obtain zinc sulfate monohydrate. This method is intended to address the problem of chlorine-containing waste acid water, but copper slag is used for dechlorination during the purification process, which is repeated, and residual chlorine can affect the quality of the zinc sulfate. Chinese patent CN112357950A discloses a method for removing and recovering fluorine and chlorine from zinc sulfate solution. The process involves selecting three mixed anion resins (201×7, D201, and D301) to remove fluorine and chlorine from the zinc sulfate solution. A sulfuric acid solution with a mass concentration of 150-400 g / L is used for countercurrent desorption. The desorbed solution is distilled to obtain a regenerated desorption solution and a mixed gas of HF and HCl. The hydrofluoric acid product is obtained by stepwise directional condensation (condensation temperature is 0-20°C), and the remaining HCl gas is absorbed by water to obtain the hydrochloric acid product. This method uses distillation to recover sulfuric acid as a regeneration agent, which has high energy consumption and large equipment investment, and does not consider the problem of azeotropy of the by-product hydrochloric acid.

[0006] Therefore, the present invention proposes a method for treating chlorine-containing waste acid water to address the many deficiencies in the treatment of the liquid after ion exchange analysis. It has low cost, low energy consumption, does not produce a large amount of gypsum slag, and is environmentally friendly. Summary of the Invention

[0007] In order to solve the above technical problems, the present invention provides a method for treating chlorine-containing waste acid water, which is characterized by comprising the following steps:

[0008] S1. Add zinc oxide or zinc calcine to the chlorine-containing wastewater for neutralization. The chlorine-containing wastewater contains at least H2SO4, Cl - and Zn 2+, react at 60℃~70℃ for 1~2h, control the pH range of the reaction end point to be 4.8~5.2, and then perform solid-liquid separation to obtain Zn-containing 2+ and Cl - The neutralized liquid and the neutralized residue are put into acid leaching;

[0009] Chemical reaction equation 1: H2SO4+ZnO=ZnSO4+H2O

[0010] Chemical reaction equation 2: 2HCl + ZnO = ZnCl2 + H2O

[0011] S2, based on S1, adding the Zn 2+ 1.0 to 1.2 times the molar equivalent of zinc calcine or zinc oxide is used for primary zinc precipitation, and the reaction is controlled at a temperature of 70° C. to 80° C. for 1 hour, followed by solid-liquid separation to obtain a primary zinc precipitation liquid and a primary zinc precipitation residue, and the primary zinc precipitation residue is put into intermediate leaching;

[0012] Chemical reaction equation 3: ZnSO4+3ZnO+7H2O=ZnSO4·3Zn(OH)2·4H2O↓

[0013] S3. Based on S2, lime slurry is added to the primary zinc precipitation liquid for secondary zinc precipitation, the pH is controlled to 6.5, the reaction is carried out at a temperature of 50° C. to 60° C. for 1 hour, and then solid-liquid separation is performed to obtain a secondary zinc precipitation liquid and a secondary zinc precipitation residue. The secondary zinc precipitation residue is re-added to step S2, and the secondary zinc precipitation liquid is added to wastewater treatment.

[0014] Chemical reaction equation 4: CaO + H2O = Ca(OH)2

[0015] Chemical reaction equation 5: ZnCl2+Ca(OH)2=Zn(OH)2↓+CaCl2

[0016] Preferably, the concentration of H2SO4 in the chlorine-containing wastewater in step S1 is 51.13 g / L, Cl - The concentration is 5946mg / L, Zn 2+ The concentration is 3.0 g / L, zinc suboxide is added to the chlorine-containing wastewater for neutralization, the reaction is carried out at a temperature of 70°C for 1.5 hours, the pH at the end of the reaction is controlled to be 5.0, and then solid-liquid separation is carried out.

[0017] Preferably, in step S2, the neutralized liquid is added with the Zn 2+ The reaction was completed with 1.2 times the molar equivalent of zinc oxide, and the reaction was carried out at 80 ° C for 1 hour, followed by solid-liquid separation to obtain Zn in the primary zinc precipitation solution. 2+ The concentration is 3.7g / L, Cl -The concentration is 8590 mg / L; the Zn content in the primary zinc precipitation slag is 48.93%.

[0018] Preferably, in step S3, the secondary zinc precipitation is carried out at a temperature of 50° C. for 1 hour, the pH is controlled to be 6.5, and then solid-liquid separation is performed to obtain a secondary zinc precipitation solution Zn 2+ The concentration of Cl is 0.15g / L - The concentration is 8590 mg / L, the secondary zinc precipitation slag is re-added to step S2, and the secondary zinc precipitation liquid is added to wastewater treatment.

[0019] Preferably, the concentration of H2SO4 in the chlorine-containing wastewater in step S1 is 37g / L, Cl - The concentration is 2376mg / L, Zn 2+ The concentration is 2.0 g / L, zinc roasted sand is added to the chlorine-containing wastewater for neutralization, the reaction is carried out at a temperature of 70°C for 1 hour, the pH at the end of the reaction is controlled to be 4.8, and then solid-liquid separation is carried out.

[0020] Preferably, in step S2, the Zn 2+ The reaction was completed with 1.0 times the molar equivalent of zinc calcine, which was reacted at 70 ° C for 1 h, followed by solid-liquid separation to obtain Zn in the primary zinc precipitation solution. 2+ The concentration is 2.5g / L, Cl - The concentration is 2600 mg / L; the Zn content in the primary zinc precipitation slag is 45.66%.

[0021] Preferably, in step S3, the secondary zinc precipitation is carried out at a temperature of 60° C. for 1 hour, the pH is controlled to be 6.5, and then solid-liquid separation is performed to obtain a secondary zinc precipitation solution Zn 2+ The concentration of Cl is 0.12g / L - The concentration is 2650 mg / L, the secondary zinc precipitation slag is re-added to step S2, and the secondary zinc precipitation liquid is added to wastewater treatment.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) No gypsum slag is generated during the treatment of chlorine-containing wastewater by the present invention. The entire reaction process is mild, energy-consuming, safe and environmentally friendly. The auxiliary material cost used in the disposal method is low, no expensive reagents and new evaporation systems are required, and the industrial output value is high. Chlorine-containing wastewaters of different concentrations are neutralized by adding different neutralizing agents and then subjected to primary zinc precipitation and secondary zinc precipitation. Sulfate ions in the chlorine-containing wastewater are fully recovered in the form of basic zinc sulfate, and chlorine is still retained in the wastewater, thereby realizing the recycling of sulfuric acid and avoiding chlorine enrichment and secondary dechlorination. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The figure is a flow chart of the overall method of the present invention. DETAILED DESCRIPTION

[0025] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0026] In the description of the present invention, unless otherwise specified, "plurality" means two or more; terms such as "upper," "lower," "left," "right," "inner," "outer," "front end," "rear end," "head," and "tail" indicate positions or relationships based on those shown in the accompanying drawings. These terms are intended solely to facilitate the description of the present invention and simplify the description. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limiting the present invention. Furthermore, terms such as "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0027] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "connected" and "connection" should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integral connection; mechanical connection, electrical connection; direct connection, or indirect connection through an intermediary. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0028] like Figure 1 As shown, the method for treating chlorine-containing waste acid water includes the following three embodiments:

[0029] Example 1

[0030] S1. Add zinc oxide or zinc calcine to the chlorine-containing wastewater for neutralization. The chlorine-containing wastewater contains at least H2SO4, Cl - and Zn 2+ , react at 60℃~70℃ for 1~2h, control the pH range of the reaction end point to be 4.8~5.2, and then perform solid-liquid separation to obtain Zn-containing 2+ and Cl - The neutralized liquid and the neutralized residue are put into acid leaching;

[0031] S2, based on S1, adding the Zn 2+ 1.0 to 1.2 times the molar equivalent of zinc calcine or zinc oxide is used for primary zinc precipitation, and the reaction is controlled at a temperature of 70° C. to 80° C. for 1 hour, followed by solid-liquid separation to obtain a primary zinc precipitation liquid and a primary zinc precipitation residue, and the primary zinc precipitation residue is put into intermediate leaching;

[0032] S3. Based on S2, lime slurry is added to the primary zinc precipitation liquid for secondary zinc precipitation, the pH is controlled to 6.5, the reaction is carried out at a temperature of 50° C. to 60° C. for 1 hour, and then solid-liquid separation is performed to obtain a secondary zinc precipitation liquid and a secondary zinc precipitation residue. The secondary zinc precipitation residue is re-added to step S2, and the secondary zinc precipitation liquid is added to wastewater treatment.

[0033] Example 2

[0034] S1, the concentration of H2SO4 in chlorine-containing wastewater is 51.13g / L, Cl - The concentration is 5946mg / L, Zn 2+ The concentration is 3.0g / L, zinc suboxide is added to the chlorine-containing wastewater for neutralization, the reaction is carried out at a temperature of 70℃ for 1.5h, the pH at the end of the reaction is controlled to be 5.0, and then solid-liquid separation is carried out;

[0035] S2, after neutralization, add Zn 2+ The zinc oxide of 1.2 times of the molar equivalent of the complete reaction was used for a zinc precipitation, and the reaction was carried out at a temperature of 80 ° C for 1 hour, followed by solid-liquid separation to obtain Zn in the zinc precipitation solution. 2+ The concentration is 3.7g / L, Cl - The concentration is 8590 mg / L; the Zn content in the primary zinc slag is 48.93%;

[0036] S3, add lime slurry to the primary zinc precipitation solution for secondary zinc precipitation, the secondary zinc precipitation is reacted at a temperature of 50 ° C for 1 hour, the pH is controlled to 6.5, and then solid-liquid separation is performed to obtain the secondary zinc precipitation solution Zn 2+ The concentration of Cl is 0.15g / L - The concentration is 8590 mg / L, the secondary zinc precipitation slag is re-added to step S2, and the secondary zinc precipitation liquid is added to wastewater treatment.

[0037] Example 3

[0038] S1, the concentration of H2SO4 in chlorine-containing wastewater is 37g / L, Cl - The concentration is 2376mg / L, Zn 2+ The concentration is 2.0g / L, zinc calcine is added to the chlorine-containing wastewater for neutralization, the reaction is carried out at a temperature of 70℃ for 1h, the pH at the end of the reaction is controlled to be 4.8, and then solid-liquid separation is carried out;

[0039] S2, add Zn into the neutralized solution 2+ The zinc calcined sand with 1.0 times of the molar equivalent of the complete reaction was used for zinc precipitation, and the reaction was carried out at a temperature of 70 ° C for 1 h, followed by solid-liquid separation to obtain Zn in the zinc precipitation solution. 2+ The concentration is 2.5g / L, Cl -The concentration is 2600 mg / L; the Zn content in the primary zinc slag is 45.66%;

[0040] S3, add lime slurry to the primary zinc precipitation solution for secondary zinc precipitation, the secondary zinc precipitation is reacted at a temperature of 60 ° C for 1 hour, the pH is controlled to 6.5, and then solid-liquid separation is performed to obtain the secondary zinc precipitation solution Zn 2+ The concentration of Cl is 0.12g / L - The concentration is 2650 mg / L, the secondary zinc precipitation slag is re-added to step S2, and the secondary zinc precipitation liquid is added to wastewater treatment.

[0041] The three embodiments of the present invention do not generate gypsum slag during the treatment process. The entire reaction process is mild, has low energy consumption, is safe and environmentally friendly, and the cost of auxiliary materials used in the treatment method is low. No expensive reagents or new evaporation systems are required, and the industrial output value is high. Chlorine-containing wastewater with different concentrations is neutralized by adding different neutralizing agents and then undergoing primary zinc precipitation and secondary zinc precipitation. Sulfate ions in the chlorine-containing wastewater are completely recovered in the form of basic zinc sulfate, and chlorine remains in the wastewater, thereby achieving the recycling of sulfuric acid and avoiding chlorine enrichment and secondary dechlorination.

[0042] The above embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of rights of the present invention. Therefore, modifications, equivalent changes, improvements, etc. made according to the scope of the patent application of the present invention are still within the scope covered by the present invention.

Claims

1. A method for treating chlorine-containing waste acid water, characterized in that: The following steps are involved: S1. Add zinc oxide or zinc calcine to the chlorine-containing wastewater for neutralization. The chlorine-containing wastewater contains at least H2SO4, Cl - and Zn 2+ , react at 60℃~70℃ for 1~2h, control the pH range of the reaction end point to be 4.8~5.2, and then perform solid-liquid separation to obtain Zn-containing 2+ and Cl - The neutralized liquid and the neutralized residue are put into acid leaching; S2, based on S1, adding the Zn 2+ 1.0 to 1.2 times the molar equivalent of zinc calcine or zinc oxide is used for primary zinc precipitation, and the reaction is controlled at a temperature of 70° C. to 80° C. for 1 hour, followed by solid-liquid separation to obtain a primary zinc precipitation liquid and a primary zinc precipitation residue, and the primary zinc precipitation residue is put into intermediate leaching; S3. Based on S2, lime slurry is added to the primary zinc precipitation liquid for secondary zinc precipitation, the pH is controlled to 6.5, the reaction is carried out at a temperature of 50° C. to 60° C. for 1 h, and then solid-liquid separation is performed to obtain a secondary zinc precipitation liquid and a secondary zinc precipitation residue, the secondary zinc precipitation residue is re-added to step S2, and the secondary zinc precipitation liquid is put into wastewater treatment; The concentration of H2SO4 in the chlorine-containing wastewater in step S1 is 51.13 g / L, and the concentration of Cl - The concentration is 5946mg / L, Zn 2+ The concentration is 3.0g / L, zinc oxide is added to the chlorine-containing wastewater for neutralization, the reaction is carried out at a temperature of 70°C for 1.5h, the pH of the reaction end point is controlled to be 5.0, and then solid-liquid separation is carried out; in the step S2, the liquid after neutralization is added with the Zn 2+ The reaction was completed with 1.2 times the molar equivalent of secondary zinc oxide, which was reacted at 80 ° C for 1 hour, followed by solid-liquid separation to obtain Zn in the primary zinc precipitation solution. 2+ The concentration is 3.7g / L, Cl - The concentration is 8590 mg / L; the Zn content in the primary zinc precipitation slag is 48.93%.

2. The method for treating chlorine-containing waste acid water according to claim 1, wherein: In step S3, the secondary zinc precipitation is carried out at a temperature of 50° C. for 1 hour, the pH is controlled to be 6.5, and then solid-liquid separation is performed to obtain the secondary zinc precipitation solution Zn 2+ The concentration of Cl is 0.15g / L - The concentration is 8590 mg / L, the secondary zinc precipitation slag is re-added to step S2, and the secondary zinc precipitation liquid is added to wastewater treatment.

3. The method for treating chlorine-containing waste acid water according to claim 1, wherein: The concentration of H2SO4 in the chlorine-containing wastewater in step S1 is 37g / L, Cl - The concentration is 2376mg / L, Zn 2+ The concentration is 2.0 g / L, zinc roasted sand is added to the chlorine-containing wastewater for neutralization, the reaction is carried out at a temperature of 70°C for 1 hour, the pH at the end of the reaction is controlled to be 4.8, and then solid-liquid separation is carried out.

4. The method for treating chlorine-containing waste acid water according to claim 3, wherein: In the step S2, the Zn 2+ The reaction was completed with 1.0 times the molar equivalent of zinc calcine, which was reacted at 70 ° C for 1 h, followed by solid-liquid separation to obtain Zn in the primary zinc precipitation solution. 2+ The concentration is 2.5g / L, Cl - The concentration is 2600 mg / L; the Zn content in the primary zinc precipitation slag is 45.66%.

5. A method for treating chlorine-containing waste acid water according to claim 4, characterized in that: In step S3, the secondary zinc precipitation is carried out at a temperature of 60° C. for 1 hour, the pH is controlled to be 6.5, and then solid-liquid separation is performed to obtain the secondary zinc precipitation solution Zn 2+ The concentration of Cl is 0.12g / L - The concentration is 2650 mg / L, the secondary zinc precipitation slag is re-added to step S2, and the secondary zinc precipitation liquid is added to wastewater treatment.

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