A method for removing impurities from polluted acid and fully recycling it

Abstract

The present invention discloses a method for removing impurities from waste acid and fully recycling the waste acid. The method comprises the following steps: introducing hydrogen sulfide into the waste acid for a sulfidation reaction, removing arsenic sulfide and mercuric sulfide precipitates formed during the reaction; continuing to introduce hydrogen sulfide for a step-by-step sulfidation reaction, adding an iron-containing substance to adjust the reaction pH and ORP, and recovering the copper, lead, and zinc sulfide slag precipitates formed during the reaction in a step-by-step manner; adding an iron-containing substance for a neutralization reaction, controlling the pH and ORP, promoting the reaction between iron ions and arsenate, and removing the ferric arsenate precipitate formed during the reaction; adding an adsorbent for an adsorption reaction, and removing fluorine-containing and thallium-containing components by adsorption; introducing an oxidant for an oxidative hydrolysis reaction, controlling the degree of hydrolysis, and preparing polyferric sulfate. The present invention utilizes the iron-containing substance to remove impurities from waste acid, thereby achieving deep impurity removal and full resource utilization of waste acid.

Description

Technical Field

[0001] The present invention belongs to the technical field of industrial wastewater treatment and resource utilization, and specifically relates to a method for removing impurities from waste acid and fully recycling it. Background Art

[0002] Non-ferrous metal smelting emits waste acid primarily from flue gas acidification and scrubbing processes. This wastewater contains 5-15% sulfuric acid, along with significant amounts of impurities such as arsenic, lead, mercury, fluorine, and chlorine, making it one of the most challenging pollutants to treat in the smelting industry. The traditional sulfide precipitation-lime iron salt treatment process has limitations. High sulfate concentrations in the waste acid react with lime to form water treatment gypsum. Due to the presence of salt and heavy metals, this gypsum lacks economical utilization, and its storage poses environmental risks. Furthermore, the high levels of fluoride and chloride ions in the waste acid create high-salinity wastewater, leading to severe equipment corrosion and difficult treatment. Furthermore, the waste acid contains heavy metals such as thallium, which poses significant health and environmental risks. Conventional waste acid treatment neglects the treatment of this characteristic heavy metal, resulting in significant environmental risks from thallium-containing effluents. Therefore, a treatment method that deeply removes impurities from the waste acid and effectively recovers valuable components is urgently needed to achieve wastewater resource utilization and reduce waste residue. Summary of the Invention

[0003] In order to solve the technical problem of "dilemma" between resource utilization of wastewater and reduction of waste residue in waste acid treatment, the purpose of the present invention is to provide a method for removing impurities and fully recycling waste acid, using sulfide precipitation-iron-containing substances to treat waste acid, controlling the reaction conditions, and removing arsenic and mercury, recovering valuable metals, and defluorinating and removing thallium from the waste acid. The remaining main components are ferric sulfate and ferrous sulfate, which are then prepared through hydrogen peroxide oxidation to form a polyferric sulfate liquid flocculant, achieving zero wastewater discharge and no secondary pollution, and having promotion and application value.

[0004] The object of the present invention is achieved by comprising the following steps:

[0005] S1. Add hydrogen sulfide to the waste acid for sulfidation reaction to remove arsenic sulfide and mercuric sulfide precipitates formed during the reaction; the reaction consumes hydrogen ions contained in the waste acid and the pH of the waste acid increases;

[0006] S2. Continue to introduce hydrogen sulfide to carry out step-by-step sulfidation reaction, add iron-containing substances to adjust the reaction pH and ORP, and step-by-step recover the copper, lead, and zinc sulfide slag precipitate formed during the reaction; the step-by-step sulfidation reaction is achieved by controlling the combined range of redox potential and pH value, and distributed precipitation recovers copper sulfide, lead sulfide, and zinc sulfide;

[0007] S3, adding iron-containing substances to carry out neutralization reaction, controlling pH and ORP, promoting the reaction between iron ions and arsenate, and removing the iron arsenate precipitate formed during the reaction;

[0008] S4, adding adsorbent to carry out adsorption reaction to remove fluorine and thallium components;

[0009] S5. An oxidant is introduced to carry out an oxidative hydrolysis reaction, and the degree of hydrolysis is controlled. Ferrous sulfite undergoes a polymerization reaction under the action of the oxidant to prepare a polyferric sulfate liquid flocculant, thereby realizing the recovery and resource utilization of iron and sulfuric acid components.

[0010] Preferably, the waste acid in step S1 is acidic wastewater containing pollutants produced by non-ferrous metal smelting, specifically waste acid produced by copper smelting.

[0011] Preferably, the iron-containing material is pig iron, scrap iron, hematite or siderite, preferably pig iron or scrap iron.

[0012] Preferably, in step S3, the pH is controlled at 4-9, preferably 4-5.

[0013] Preferably, the oxidant in step S5 is hydrogen peroxide.

[0014] Preferably, the pH of the reaction in step S5 is controlled at 4-11, preferably 6-9.

[0015] Compared with the prior art, the present invention has the following technical effects:

[0016] 1. Using iron to replace calcium in the waste acid treatment process, and preparing polyferric sulfate through iron oxidation and hydrolysis to recover iron, can effectively avoid the generation of calcium sulfate waste residue and treatment costs;

[0017] 2. Use iron-containing substances to adjust the pH of the waste acid, and use sulfur ions to remove lead, copper and zinc in the waste acid by sulfide precipitation step by step, so as to achieve the recovery of valuable components of copper, lead and zinc;

[0018] 3. After deep decontamination, the main component of the water is ferrous sulfate. By adding hydrogen peroxide and other methods to control the iron hydrolysis conditions, polyferric sulfate can be prepared, which can realize the resource utilization of polyferric sulfate in the waste acid;

[0019] 4. Focus on the efficient removal of arsenic, fluorine and thallium. By adding iron-containing substances to neutralize the polluted acid, ferric arsenate precipitation is formed under weakly acidic conditions, which can achieve efficient removal of arsenic. Special adsorbents are used to adsorb fluorine and thallium in wastewater, which can achieve efficient removal of fluorine / thallium. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the process of the present invention. DETAILED DESCRIPTION

[0021] The present invention is further described below with reference to the embodiments and drawings, but the present invention is not limited in any way. Any changes or substitutions made based on the teachings of the present invention fall within the scope of protection of the present invention.

[0022] Example 1

[0023] As attached Figure 1 The method for removing impurities and fully recycling the waste acid in this embodiment includes the following steps:

[0024] S1. Add hydrogen sulfide to the waste acid produced by copper smelting to carry out a sulfidation reaction to remove arsenic sulfide and mercury sulfide precipitates formed during the reaction;

[0025] S2. Continue to introduce hydrogen sulfide to carry out step-by-step sulfidation reaction, add pig iron to adjust the reaction pH and ORP, first precipitate lead sulfide at a lower pH value, slightly increase the pH value to precipitate copper sulfide, further adjust the pH value to near neutral or slightly alkaline conditions to precipitate zinc sulfide, and step-by-step recover the copper, lead, and zinc sulfide slag precipitate formed during the reaction process;

[0026] S3, adding pig iron for neutralization reaction, controlling pH and ORP, pH 4.0-6.5, promoting the reaction between iron ions and arsenate, and removing the iron arsenate precipitate formed during the reaction;

[0027] S4, adding adsorbent to carry out adsorption reaction to remove fluorine and thallium components;

[0028] S5. Add hydrogen peroxide to carry out oxidative hydrolysis reaction at a pH of 4.0-7.0, control the degree of hydrolysis, and prepare polyferric sulfate.

[0029] Example 2

[0030] The method for removing impurities and fully recycling waste acid in this embodiment is the same as that in Example 1, except that all iron-containing substances are scrap iron, the pH in step S3 is 6.0-8.0, and the pH in step S5 is 6.5-9.5.

[0031] Example 3

[0032] In the method for removing impurities and fully recycling waste acid in this embodiment, the waste acid produced by nickel smelting is selected as the waste acid for removal, hematite is selected as the iron-containing substance, the pH value in step S3 is 7.0-9.0, and the pH value in step S5 is 8.0-11.0. Other aspects are the same as those in Example 1.

[0033] Example 4

[0034] The method for removing impurities and fully recycling the waste acid in this embodiment is the same as that in Example 1, except that siderite is selected as the iron-containing substance, the pH in step S3 is 4.0-5.0, and the pH in step S5 is 6.0-9.0.

Claims

1. A method for removing impurities from waste acid and recycling its entire amount, characterized in that The following steps are involved: S1. Add hydrogen sulfide to the waste acid to carry out sulfidation reaction and remove arsenic sulfide and mercury sulfide precipitates formed during the reaction; S2, continue to introduce hydrogen sulfide to carry out step-by-step sulfidation reaction, add iron-containing substances to adjust the reaction pH and ORP, and step-by-step recover the copper, lead, and zinc sulfide slag precipitate formed during the reaction; S3, adding iron-containing substances to carry out neutralization reaction, controlling pH and ORP, promoting the reaction between iron ions and arsenate, and removing the iron arsenate precipitate formed during the reaction; S4, adding adsorbent to carry out adsorption reaction to remove fluorine and thallium components; S5. An oxidant is introduced to carry out an oxidative hydrolysis reaction, and the degree of hydrolysis is controlled to prepare polyferric sulfate.

2. The method for removing impurities and fully recycling contaminated acid according to claim 1, characterized in that The polluted acid in step S1 is acidic wastewater containing pollutants produced by non-ferrous metal smelting.

3. The method for removing impurities and fully recycling contaminated acid according to claim 1, characterized in that The iron-containing material is pig iron, scrap iron, hematite or siderite.

4. The method for removing impurities and fully recycling contaminated acid according to claim 1, characterized in that In step S3, the pH is controlled at 4-9.

5. The method for removing impurities and fully recycling contaminated acid according to claim 1, characterized in that The oxidant in step S5 is hydrogen peroxide.

6. The method for removing impurities and fully recycling contaminated acid according to claim 1, characterized in that The pH of the reaction in step S5 is controlled at 4-11.

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