Treatment method of arsenic-containing acidic wastewater

Abstract

The invention provides an arsenic-containing acidic wastewater treatment method which comprises the following steps: adding an alkaline agent into arsenic-containing acidic wastewater, and adjusting the pH value to be greater than or equal to 8.5 to obtain alkaline wastewater; synchronously adding a weight removal agent and a first arsenic removal agent into the alkaline wastewater, and reacting at 20-50 DEG C to obtain a first mixed solution; adding a second arsenic removal agent into the first mixed solution, and reacting at 20-50 DEG C to obtain a second mixed solution; and carrying out filter pressing treatment on the second mixed solution, and separating to obtain filtrate and arsenic-containing sludge. The treatment method of the arsenic-containing acidic wastewater is simple in process, convenient to operate and mild in reaction condition, can realize synchronous deep removal of various heavy metals such as copper, cobalt, nickel, lead, cadmium and the like, trivalent arsenic and pentavalent arsenic, greatly reduces energy consumption, further reduces operation and treatment cost, and is easy to popularize and apply on a large scale.

Description

Technical Field

[0001] This invention belongs to the field of industrial wastewater treatment technology, and particularly relates to a method for treating arsenic-containing acidic wastewater. Background Technology

[0002] Arsenic-containing acidic wastewater is a typical type of high-risk wastewater generated during industrial production processes such as mining and smelting, non-ferrous metal processing, chemical production, and sulfuric acid manufacturing. It is typically characterized by strong acidity (pH<2) and high concentrations of arsenic pollution. It is highly toxic and has high environmental mobility. If discharged directly without proper treatment, it will cause serious and irreversible damage to water bodies, soil, and ecosystems, and can accumulate through the food chain, seriously threatening human health.

[0003] Currently, the treatment technologies for arsenic-containing acidic wastewater mainly revolve around "acid neutralization" and "arsenic speciation conversion." Common methods include: lime neutralization precipitation, which is low-cost but produces large amounts of sludge and the precipitate is prone to back-dissolution; iron / aluminum salt coagulation precipitation, which is effective in removing pentavalent arsenic but has limited capacity for removing trivalent arsenic and generates a large amount of arsenic-containing sludge; sulfide precipitation, suitable for high-concentration arsenic wastewater, but poses risks of hydrogen sulfide gas release and secondary sulfide pollution; adsorption, mostly used for low-concentration deep treatment, but is easily affected by pH under high acid and high arsenic conditions and has limited adsorption capacity; membrane separation and ion exchange are costly and face problems such as membrane fouling and regenerated liquid treatment. Furthermore, existing processes often require the pre-oxidation of trivalent arsenic to pentavalent arsenic, increasing process complexity and treatment costs. Therefore, this invention provides a method for treating arsenic-containing acidic wastewater to solve the problems of complex existing processes and the difficulty in simultaneously removing heavy metals and arsenic. Summary of the Invention

[0004] The main objective of this invention is to provide a method for treating arsenic-containing acidic wastewater, aiming to solve the technical problems of complex processes and difficulty in simultaneously removing heavy metals and arsenic in the prior art.

[0005] To achieve the above objectives, the present invention provides a method for treating arsenic-containing acidic wastewater, comprising the following steps: S1: Add an alkaline agent to the arsenic-containing acidic wastewater to adjust the pH to ≥ 8.5, thus obtaining alkaline wastewater.

[0006] S2: Add a weight removal agent and a first arsenic removal agent simultaneously to the alkaline wastewater, and react at 20~50℃ to obtain a first mixed solution.

[0007] S3: Add the second arsenic removal agent to the first mixed solution and react at 20~50℃ to obtain the second mixed solution.

[0008] S4: The second mixed solution is subjected to pressure filtration to separate the filtrate and arsenic-containing sludge.

[0009] The heavy metal content in the arsenic-containing acidic wastewater includes: Cu≥1mg / L, Co≥0.5mg / L, Ni≥1.0mg / L, Cd≥0.2mg / L, Pb≥3mg / L, Hg≥0.02mg / L, and As≥15mg / L.

[0010] According to embodiments of this application, the alkaline agent includes one or more of sodium hydroxide and sodium carbonate.

[0011] According to embodiments of this application, the sludge remover includes one or more of aluminum salts, iron salts, trisodium trimercaptotriazine (TMT), and dithiocarbamate (DTC) compounds.

[0012] The mass fraction of the active ingredient in the weight-removing agent is 5-95%.

[0013] The chemical composition of the sludge remover, by mass fraction, includes one or more of the following: 10-70% dithiocarbamate, 10-30% trithiotriazine trisodium salt, and 1-30% polyaluminum salt.

[0014] According to embodiments of this application, the first arsenic removal agent includes one or more of calcium oxide, calcium hydroxide, magnesium oxide, magnesium hydroxide, magnesium sulfate, polyaluminum sulfate, and polyferric sulfate.

[0015] According to embodiments of this application, the second arsenic removal agent includes one or more of sodium persulfate, ferric chloride, and hydrogen peroxide.

[0016] According to an embodiment of this application, the mass ratio of alkaline wastewater to desiccant is 100:(0.05~0.1).

[0017] The mass ratio of alkaline wastewater to the first arsenic removal agent is 100:(0.01~1).

[0018] The mass ratio of the second mixed solution to the second arsenic removal agent is 100:(0.01~0.1).

[0019] According to an embodiment of this application, the pH of the first mixed solution is 8.0 to 9.0.

[0020] The pH of the second mixed solution is 6.0~9.0.

[0021] According to embodiments of this application, the arsenic in the arsenic-containing acidic wastewater includes trivalent and / or pentavalent arsenic, and contains Cu. 2+ Ni 2+ Co 2+ Cd 2+ Zn 2+ Pb2+ Hg 2+ One or more of them.

[0022] According to the embodiments of this application, the content of heavy metal elements in the filtrate includes: Cu≤1mg / L, Co≤1mg / L, Ni≤0.5mg / L, Cd≤0.02mg / L, Zn<4mg / L, Pb≤0.2mg / L, Hg≤0.01mg / L, and As≤0.1mg / L.

[0023] The present invention also provides an application of the filtrate obtained by the above-mentioned treatment method, wherein the filtrate is used for industrial circulating cooling, production process reuse, or discharge in compliance with standards.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: The aforementioned method for treating arsenic-containing acidic wastewater employs a step-by-step treatment process of "alkaline adjustment - simultaneous heavy metal and arsenic removal - secondary deep arsenic removal," achieving simultaneous removal of heavy metals and arsenic. Compared to traditional segmented treatment processes, this significantly simplifies the operation process. Furthermore, each reaction stage is conducted under mild conditions of 20-50℃, eliminating the need for harsh conditions such as high temperature and high pressure, making operation simple and reducing production costs. Through a two-stage arsenic removal process design, the synergistic effect of primary arsenic removal and simultaneous heavy metal removal, coupled with the deep arsenic removal in the secondary stage, ensures complete arsenic removal. Simultaneously, it efficiently removes multiple heavy metal ions such as Cu, Co, Ni, Cd, Pb, and Hg, effectively solving the problem of treating complex pollution. Ultimately, the concentrations of arsenic and heavy metals in the filtrate consistently meet standards, resulting in highly reliable effluent quality.

[0025] Moreover, the treatment method for arsenic-containing acidic wastewater of the present invention has a simple process, is easy to operate, and has mild reaction conditions, which greatly reduces energy consumption, further reduces operating and treatment costs, and is easy to promote and apply on a large scale. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0027] Figure 1 This is a flowchart of the method for treating arsenic-containing acidic wastewater according to Embodiment 1 of the present invention.

[0028] The realization of the objective, functional characteristics and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0031] To achieve the above objectives, the present invention provides a method for treating arsenic-containing acidic wastewater, comprising the following steps: S1: Add an alkaline agent to the arsenic-containing acidic wastewater to adjust the pH to ≥ 8.5, obtaining alkaline wastewater. The heavy metal content in the arsenic-containing acidic wastewater includes: Cu ≥ 1 mg / L, Co ≥ 0.5 mg / L, Ni ≥ 1.0 mg / L, Cd ≥ 0.2 mg / L, Pb ≥ 3 mg / L, Hg ≥ 0.02 mg / L, and As ≥ 15 mg / L.

[0032] In some embodiments, the content of heavy metal elements in the arsenic-containing acidic wastewater includes: Cu content of 1~1.50 mg / L, Co content of 0.5~0.6 mg / L, Ni content of 1~1.4 mg / L, Cd content of 0.2~0.3 mg / L, Pb content of 3~4 mg / L, Hg content of 0.02~0.03 mg / L, and As content of 15~18 mg / L.

[0033] In some embodiments, an alkaline agent is added to the arsenic-containing acidic wastewater to adjust the pH to 8.5-13.0, rapidly raising the original acidic system to alkaline, which simultaneously converts dissolved arsenic into highly active arsenate ions (AsO4). 3- The conversion of arsenic and precipitation of heavy metal hydroxides directly eliminates the traditional steps of "segmented pH adjustment - arsenic reprecipitation," significantly simplifying the treatment process for arsenic-containing acidic wastewater and improving overall treatment efficiency. The highly alkaline environment instantly disrupts the complexation balance between arsenic and heavy metals in the wastewater, causing the complexed arsenic and heavy metals to dissociate simultaneously. This effectively avoids arsenic residue problems caused by complex "encapsulation," significantly reducing the concentration of arsenic and heavy metals in the treated filtrate, achieving simultaneous removal of arsenic and heavy metals to meet standards, with a simultaneous compliance rate ≥99%.

[0034] In some embodiments, adding an alkaline agent to arsenic-containing acidic wastewater to adjust the pH to 8.5-9.0 can, while initially removing heavy metals through hydroxide precipitation, alter the occurrence form of metal ions in the wastewater. This creates suitable reaction conditions for subsequent deep heavy metal and arsenic removal processes, ensuring the efficiency and stability of subsequent treatment stages. Under alkaline conditions, dissolved arsenic converts to arsenate ions (AsO4). 3- The directional transformation of ions provides highly active binding sites for the subsequent calcium-arsenic coprecipitation reaction, laying a good foundation for the deep removal of arsenic. The purpose of adjusting the alkali is to initially remove heavy metals (generating hydroxide precipitates) and change the form of metal ions, creating conditions for subsequent heavy metal and arsenic removal.

[0035] S2: Add a weight removal agent and a first arsenic removal agent simultaneously to the alkaline wastewater, and react at 20~50℃ to obtain a first mixed solution.

[0036] In some embodiments, adjusting the alkali can achieve preliminary weight removal, initially removing metal ions that easily form hydroxide precipitates. This creates conditions for subsequent chelation weight removal and reduces the amount of subsequent weight removal agent required. After adding the weight removal agent, the formation of chelated precipitates is the primary process, and the process can efficiently remove metals and potassium in complex form. SP Smaller metal ions enable simultaneous deep removal of multiple metals. Simultaneously, the addition of the first arsenic removal agent achieves dual precipitation of metal chelates and sparingly soluble arsenic residue, utilizing the co-precipitation effect to achieve efficient arsenic removal. The addition of the second arsenic removal agent aims to oxidize residual trivalent arsenic to pentavalent arsenic, achieving deep arsenic removal. The process can eliminate interference from water quality fluctuations, organic residues, and reducing substances on the removal of weight and arsenic, enhancing the stability of the removal effect.

[0037] In some embodiments, a weight removal agent and a first arsenic removal agent are simultaneously added to the alkaline wastewater and reacted at 20-50°C to generate chelate precipitates for deep weight removal. Arsenic is initially removed through adsorption co-precipitation and chemical precipitation (arsenic is reduced from 200 mg / L to below 1 mg / L). The removal rate of arsenic and other heavy metals in the process is over 99.9%.

[0038] In some embodiments, a weight removal agent and a first arsenic removal agent are simultaneously added to the alkaline wastewater, and the mixture is reacted at 35-45°C to obtain a first mixed solution.

[0039] S3: Add the second arsenic removal agent to the first mixed solution and react at 20~50℃ to obtain the second mixed solution.

[0040] In some embodiments, by selecting a suitable second arsenic removal agent, the dual effects of "surface complexation-encapsulation" and "arsenate reprecipitation" can continue to occur on the already formed primary calcium-arsenic / iron-arsenic eutectic surface, thereby reducing the residual As concentration in the filtrate to ≤0.1 mg / L in one step.

[0041] In some embodiments, a second arsenic removal agent is added to the first mixed solution and reacted at 20~50°C to achieve deep arsenic removal (arsenic concentration is reduced from 0.5 mg / L to below 0.1 mg / L). The dosage of the second arsenic removal agent can be adjusted according to the water quality to achieve deep removal of low-valent arsenic, while further enhancing the weight removal effect and reducing the impact of water quality fluctuations, organic residues, and reducing substances on the weight removal effect.

[0042] In some embodiments, a second arsenic removal agent is added to the first mixed solution, and the mixture is reacted at 40-50°C to obtain a second mixed solution.

[0043] In some embodiments, the selected second arsenic removal agent can form amorphous hydroxyl iron / aluminum flocs, which have "self-flocculation" characteristics and "secondary collection" of residual heavy metals such as Pb, Cd, and Cu, achieving "dual compliance of arsenic and heavy metals"; at the same time, the flocs have weak competitive adsorption of anions such as fluorine and phosphate, ensuring treatment selectivity and avoiding waste of reagents.

[0044] S4: The second mixed solution is subjected to pressure filtration to separate the filtrate and arsenic-containing sludge.

[0045] In some embodiments, diaphragm pressure filtration (pressure 0.8~1.2 MPa) is used to completely retain suspended calcium arsenate / ferric arsenate and heavy metal hydroxides in the second mixed solution. At the same time, the high alkalinity condition can inhibit the redissolution of arsenic, ensuring that the filtrate contains As≤0.1 mg / L, Cu≤1 mg / L, Co≤1 mg / L, Ni≤0.5 mg / L, Cd≤0.02 mg / L, Zn<4 mg / L, Pb≤0.2 mg / L, and Hg≤0.01 mg / L.

[0046] In some embodiments, the filtrate obtained after pressure filtration has simultaneously completed the three major indicators of arsenic removal, heavy metal removal, and alkali adjustment, and can be directly recycled for upstream processes or directly discharged.

[0047] In some embodiments, arsenic in arsenic-containing sludge exists stably in the forms of Ca3(AsO4)2·xH2O, FeAsO4, and eutectic morphology. The sludge is homogeneous, and the arsenic in the sludge exists stably in the form of arsenates. Heavy metals mainly exist in the form of chelates and are stable in properties. Due to the small amount of sludge and the high grade of valuable metals, it has high recovery value.

[0048] The aforementioned method for treating arsenic-containing acidic wastewater employs a step-by-step treatment process of "alkaline adjustment - simultaneous heavy metal and arsenic removal - secondary deep arsenic removal," achieving simultaneous removal of heavy metals and arsenic. Compared to traditional segmented treatment processes, this significantly simplifies the operation process. Furthermore, each reaction stage is conducted under mild conditions of 20-50℃, eliminating the need for harsh conditions such as high temperature and high pressure, making operation simple and reducing production costs. Through a two-stage arsenic removal process design, the synergistic effect of primary arsenic removal and simultaneous heavy metal removal, coupled with the deep arsenic removal in the secondary stage, ensures complete arsenic removal. Simultaneously, it efficiently removes multiple heavy metal ions such as Cu, Co, Ni, Cd, Pb, and Hg, effectively solving the problem of treating complex pollution. Ultimately, the concentrations of arsenic and heavy metals in the filtrate consistently meet standards, resulting in highly reliable effluent quality.

[0049] In some embodiments, the alkaline agent includes one or more of sodium hydroxide and sodium carbonate.

[0050] In some embodiments, the alkaline agent includes sodium hydroxide or sodium carbonate.

[0051] In some embodiments, the alkaline agent includes sodium hydroxide. Preferably, the alkaline agent includes a sodium hydroxide solution with a mass fraction of 45-50%. NaOH is a strong base with a degree of ionization >95%, and can raise the pH of arsenic-containing acidic wastewater to ≥8.5 within 5-30 seconds.

[0052] In some embodiments, the alkaline agent includes sodium carbonate, which, although a weak base, is effective against CO3. 2- It possesses both alkalinity and complexing ability, and also has a synergistic decomposition effect on Cu, Ni, Pb, etc., thereby increasing the rate of the "one alkali, two precipitation" reaction.

[0053] In some embodiments, the alkaline agent includes sodium hydroxide and sodium carbonate. Compared to using sodium hydroxide or sodium carbonate alone, CO3... 2- / HCO3 - The system forms a pH buffer zone of 9-11, ensuring that arsenic is contained in AsO4. 3- The presence of the reagent in its original form avoids subsequent arsenic re-dissolution due to a sudden drop in pH caused by atmospheric CO2 dissolution, thus reducing the need for secondary reagent adjustments. The introduced CO3... 2- Can be used with Pb 2+ Cd 2+ Zn 2+ Instantly generates sparingly soluble carbonates such as PbCO3, CdCO3, and Zn5(CO3)2(OH)6, which form a "ternary eutectic" with hydroxides and arsenates, thus achieving the removal of heavy metal ions.

[0054] In some embodiments, the scavenging agent includes one or more of aluminum salts, iron salts, trisodium trimercaptotriazine (TMT), and dithiocarbamate (DTC) compounds.

[0055] The mass fraction of the active ingredient in the weight-removing agent is 5-95%.

[0056] The chemical composition of the sludge remover, by mass fraction, includes one or more of the following: 10-70% dithiocarbamate, 10-30% trithiotriazine trisodium salt, and 1-30% polyaluminum salt.

[0057] In some embodiments, the chemical composition of the scavenging agent, by mass fraction, includes one or more of the following: 10-70% dithiocarbamate (effective content ≥90%), 10-30% trithiotriazine trisodium salt (effective content ≥15%), and 1-30% polyaluminum salt (alumina ≥15.8%).

[0058] In some embodiments, the dithiocarbamate is sodium thiram, and the polyaluminum salt is polyaluminum sulfate. Sodium thiram and trisodium trimercaptotriazine react with Cu via the -SNa / -SH active groups. 2+ Zn 2+ Pb 2+ Cd 2+ Ni 2+ Simultaneous formation of stable five- or six-membered ring chelates with heavy metal ions enables the simultaneous removal of heavy metal ions. Polyaluminum sulfate can simultaneously provide Al... 13 O4(OH) 24 7+ Highly charged aluminum hydroxyl clusters cause the chelates to rapidly aggregate into flocs, significantly shortening the settling time.

[0059] In some embodiments, the mass fraction of the active ingredient in the desiccant is 90-95%.

[0060] In some embodiments, the first arsenic removal agent includes one or more of calcium oxide, calcium hydroxide, magnesium oxide, magnesium hydroxide, magnesium sulfate, polyaluminum sulfate, and polyferric sulfate.

[0061] In some embodiments, the first arsenic removal agent includes one of calcium oxide, calcium hydroxide, magnesium oxide, magnesium hydroxide, magnesium sulfate, polyaluminum sulfate, and polyferric sulfate.

[0062] In some embodiments, the first arsenic removal agent is magnesium oxide (effective content of 90%) and polyaluminum sulfate (effective content of aluminum oxide of 16.0%), wherein the mass ratio of magnesium oxide to polyaluminum sulfate is 78~82:18~22.

[0063] In some embodiments, the first arsenic removal agent includes one or more of the following: calcium oxide (effective content ≥90%), calcium hydroxide (effective content ≥90%), magnesium oxide (effective content ≥85%), magnesium hydroxide (effective content ≥92%), magnesium sulfate (effective content ≥98%), polyaluminum sulfate (alumina ≥15.8%), and polyferric sulfate (iron ≥20%).

[0064] In some embodiments, the first arsenic removal agent comprises an iron salt, which includes one or more of ferric chloride, ferrous sulfate, and polyferric sulfate.

[0065] In some embodiments, the first arsenic removal agent includes an aluminum salt, which includes one or more of polyaluminum chloride and aluminum sulfate, and can form aluminum arsenate precipitate with arsenate ions, thereby removing arsenic and fluorine simultaneously without the need for additional reagents.

[0066] In some embodiments, the second arsenic removal agent includes one or more of sodium persulfate, ferric chloride, and hydrogen peroxide.

[0067] In some embodiments, the second arsenic removal agent includes one of sodium persulfate, ferric chloride, and hydrogen peroxide.

[0068] In some embodiments, the second arsenic removal agent includes sodium persulfate.

[0069] In some embodiments, the second arsenic removal agent includes one or more of sodium persulfate (effective content ≥99%), ferric chloride (effective content ≥30%), and hydrogen peroxide (effective content ≥27.5%).

[0070] In some embodiments, the mass ratio of alkaline wastewater to sludge removal agent is 100:(0.05~0.1).

[0071] The mass ratio of alkaline wastewater to the first arsenic removal agent is 100:(0.01~1).

[0072] The mass ratio of the second mixed solution to the second arsenic removal agent is 100:(0.01~0.1).

[0073] In some embodiments, the mass ratio of alkaline wastewater to sludge removal agent is 100:0.5~0.1.

[0074] The mass ratio of the alkaline wastewater to the first arsenic removal agent is 100:0.01~0.05.

[0075] The volume ratio of the second mixed solution to the second arsenic removal agent is 100:0.01~0.05.

[0076] In some embodiments, the pH of the first mixed solution is 8.0 to 9.0.

[0077] The pH of the second mixed solution is 6.0~9.0.

[0078] In some embodiments, the pH of the first mixed solution is 8.5 to 9.0.

[0079] The pH of the second mixed solution is 6.5 to 8.5.

[0080] In some embodiments, the arsenic-containing acidic wastewater is wastewater generated by the metallurgical, chemical, or mining industries.

[0081] In some embodiments, the arsenic in the arsenic-containing acidic wastewater includes trivalent and / or pentavalent arsenic, and contains Cu. 2+ Ni 2+ Co 2+ Cd 2+ Zn 2+ Pb 2+ Hg 2+ One or more of them.

[0082] In some embodiments, the arsenic in the arsenic-containing acidic wastewater includes trivalent and / or pentavalent arsenic, and contains Cu. 2+ Ni 2+ Co 2+ Cd 2+ Zn 2+ Pb 2+ Hg 2+ One of them.

[0083] In some embodiments, the arsenic-containing acidic wastewater from copper smelting is wastewater generated during the copper smelting process through absorption treatment.

[0084] The arsenic-containing acidic wastewater contains arsenic in the forms of trivalent and pentavalent arsenic, and also contains Cu. 2+ Ni 2+ Co 2+ Cd 2+ Zn 2+ Pb 2+ Hg 2+ .

[0085] In some embodiments, the content of heavy metal elements in the filtrate includes: Cu≤1mg / L, Co≤1mg / L, Ni≤0.5mg / L, Cd≤0.02mg / L, Zn<4mg / L, Pb≤0.2mg / L, Hg≤0.01mg / L, and As≤0.1mg / L.

[0086] In some embodiments, the content of heavy metal elements in the filtrate is as follows: Cu content is 0.05~0.6 mg / L, Co content is 0.001~0.5 mg / L, Ni content is 0.1~0.5 mg / L, Cd content is 0.003~0.02 mg / L, Zn content is 0.0016~3 mg / L, Pb content is 0.05~0.2 mg / L, Hg content is 0.0004~0.01 mg / L, and As content is 0.007~0.1 mg / L.

[0087] The method for treating arsenic-containing acidic wastewater of the present invention is simple in process, easy to operate, and has mild reaction conditions, which greatly reduces energy consumption, further reduces operating and treatment costs, and is easy to promote and apply on a large scale.

[0088] The present invention also provides an application of the filtrate obtained by the above-mentioned treatment method, wherein the filtrate is used for industrial circulating cooling, production process reuse, or discharge in compliance with standards.

[0089] To further illustrate the present invention, the following examples are provided: Example 1 A method for treating arsenic-containing acidic wastewater, comprising the following steps: S1: An alkaline agent is added to the arsenic-containing acidic wastewater to adjust the pH to 8.6, resulting in alkaline wastewater; the alkaline agent is a 50% sodium hydroxide solution. The heavy metal content in the arsenic-containing acidic wastewater is as follows: Cu 1.20 mg / L, Co 0.52 mg / L, Ni 1.34 mg / L, Cd 0.24 mg / L, Pb 3.31 mg / L, Hg 0.03 mg / L, and As 15.8 mg / L.

[0090] Arsenic-containing acidic wastewater from copper smelting refers to the wastewater generated during the copper smelting process through absorption treatment.

[0091] In arsenic-containing acidic wastewater, arsenic exists in trivalent and pentavalent forms, and it also contains Cu. 2+ Ni 2+ Co 2+ Cd 2+ Zn 2+ Pb 2+ Hg 2+ .

[0092] S2: A sludge removal agent and a first arsenic removal agent are simultaneously added to alkaline wastewater and reacted at 40°C to obtain a first mixed solution; the sludge removal agent is sodium thiram; the mass fraction of the effective component in the sludge removal agent is 95%; The mass ratio of alkaline wastewater to de-gravity agent is 100:0.1.

[0093] The first arsenic removal agent is magnesium oxide (effective content of 90%) and polyaluminum sulfate (effective content of aluminum oxide of 16.0%), wherein the mass ratio of magnesium oxide to polyaluminum sulfate is 80:20.

[0094] The mass ratio of alkaline wastewater to the first arsenic removal agent is 100:0.05.

[0095] The pH of the first mixed solution is 8.7.

[0096] S3: Add the second arsenic removal agent to the first mixed solution and react at 50°C to obtain the second mixed solution; the second arsenic removal agent is sodium persulfate. The volume ratio of the second mixed solution to the second arsenic removal agent is 100:0.025.

[0097] The pH of the second mixed solution is 6.8.

[0098] S4: The second mixed solution is subjected to pressure filtration to separate the filtrate and arsenic-containing sludge. See the experimental procedure below. Figure 1 .

[0099] According to the test, the content of heavy metal elements in the filtrate obtained by the treatment method in Example 1 is as follows: Cu content is 0.09 mg / L, Co content is 0.008 mg / L, Ni content is 0.37 mg / L, Cd content is 0.0032 mg / L, Zn content is 1.6 mg / L, Pb content is 0.052 mg / L, Hg content is 0.0004 mg / L, and As content is 0.007 mg / L.

[0100] Example 2 Compared to Example 1, Example 2 changed the deweighting agent.

[0101] The precipitant used was polyaluminum sulfate. The other steps were the same as in Example 1, yielding filtrate and arsenic-containing sludge.

[0102] According to the test, the content of heavy metal elements in the filtrate obtained by the treatment method in Example 2 is as follows: Cu content is 0.19 mg / L, Co content is 0.1 mg / L, Ni content is 0.42 mg / L, Cd content is 0.015 mg / L, Zn content is 1.9 mg / L, Pb content is 0.06 mg / L, Hg content is 0.0007 mg / L, and As content is 0.0086 mg / L.

[0103] Example 3 Compared to Example 1, Example 3 differs in that the first arsenic removal agent is modified.

[0104] The first arsenic removal agent consisted of calcium oxide (effective content of 90%) and magnesium hydroxide (effective content of 92%). The other steps were the same as in Example 1, and filtrate and arsenic-containing sludge were obtained.

[0105] According to the test, the content of heavy metal elements in the filtrate obtained by the treatment method in Example 3 is as follows: Cu content is 0.27 mg / L, Co content is 0.3 mg / L, Ni content is 0.5 mg / L, Cd content is 0.017 mg / L, Zn content is 2.02 mg / L, Pb content is 0.13 mg / L, Hg content is 0.001 mg / L, and As content is 0.0091 mg / L.

[0106] Example 4 Compared to Example 1, Example 4 modifies the second arsenic removal agent.

[0107] The second arsenic removal agent consisted of ferric chloride (effective content of 30%) and hydrogen peroxide (effective content of 28%). The other steps were the same as in Example 1, and filtrate and arsenic-containing sludge were obtained.

[0108] According to the test, the content of heavy metal elements in the filtrate obtained by the treatment method in Example 4 is as follows: Cu content is 0.360 mg / L, Co content is 0.25 mg / L, Ni content is 0.48 mg / L, Cd content is 0.01 mg / L, Zn content is 2.17 mg / L, Pb content is 0.11 mg / L, Hg content is 0.008 mg / L, and As content is 0.0068 mg / L.

[0109] Comparative Example 1 In Comparative Example 1, no alkaline agent was added compared to Example 1. The other steps were the same as in Example 1, yielding filtrate and arsenic-containing sludge.

[0110] Testing revealed that in the filtrate obtained using the treatment method in Comparative Example 1, because no alkaline agent was added, the arsenic in the wastewater was mainly in the form of AsO3. 3- Arsenic exists in soluble anionic form, cannot directly form a precipitate, and is difficult to be effectively adsorbed by hydroxide flocs, thus hindering effective solid-liquid separation. This results in the following heavy metal content in the filtrate: Cu 1.2 mg / L, Co 0.47 mg / L, Ni 1.27 mg / L, Cd 0.22 mg / L, Zn 1.3 mg / L, Pb 2.63 mg / L, Hg 0.025 mg / L, and As 14.6 mg / L.

[0111] Comparative Example 2 Compared to Example 1, Comparative Example 2 did not simultaneously add a weight removal agent and a first arsenic removal agent.

[0112] In this process, a sludge remover was added first, followed by a first arsenic remover. The other steps were the same as in Example 1, resulting in filtrate and arsenic-containing sludge.

[0113] Testing revealed that in the filtrate obtained using the treatment method in Comparative Example 2, because a heavy metal removal agent was added first, followed by the first arsenic removal agent, the heavy metal removal agent preferentially reacted with heavy metal ions in the wastewater to form heavy metal precipitates. Simultaneously, the cations in the heavy metal removal agent reacted with OH- ions in the wastewater. - CO3 2- Calcium salt precipitates are formed. These precipitates initially form a large number of solid particles in the system. When the first arsenic removal agent is added subsequently, the hydroxide colloids generated by its hydrolysis preferentially adsorb onto the surface of the already formed heavy metal / calcium salt precipitates, rather than being fully dispersed in the wastewater to adsorb arsenic anions. This leads to a significant reduction in the effective adsorption sites of the colloids, a sharp drop in the binding efficiency of arsenic to the colloids, and ultimately, incomplete arsenic removal in the first stage. A second arsenic removal agent is needed to compensate, resulting in a significant decrease in the arsenic removal efficiency of the first arsenic removal agent and a high likelihood of exceeding the arsenic concentration standard in the effluent. The heavy metal content in the filtrate is as follows: Cu > 1 mg / L, Co > 1 mg / L, Ni > 0.5 mg / L, Cd > 0.02 mg / L, Zn > 4 mg / L, Pb > 0.2 mg / L, Hg > 0.01 mg / L, As > 0.1 mg / L.

[0114] The content of Cu is 0.80 mg / L, the content of Co is 0.46 mg / L, the content of Ni is 1.23 mg / L, the content of Cd is 0.15 mg / L, the content of Pb is 2.15 mg / L, the content of Hg is 0.013 mg / L, and the content of As is 6.8 mg / L.

[0115] Comparative Example 3 In Comparative Example 3, no second arsenic removal agent was added compared to Example 1. The other steps were the same as in Example 1, yielding filtrate and arsenic-containing sludge.

[0116] Tests showed that, in the filtrate prepared by the treatment method in Comparative Example 3, the lack of a second arsenic removal agent meant that the weakly bound arsenic in the first mixed solution had no subsequent fixation process. This not only resulted in excessive arsenic levels in the effluent, making deep arsenic removal impossible, but also caused the generated waste residue to become a hazardous arsenic-containing waste, leading to secondary pollution of soil and groundwater. The heavy metal content in the filtrate was as follows: Cu > 1 mg / L, Co > 1 mg / L, Ni > 0.5 mg / L, Cd > 0.02 mg / L, Zn > 4 mg / L, Pb > 0.2 mg / L, Hg > 0.01 mg / L, and As > 0.1 mg / L.

[0117] The content of Cu is 0.3 mg / L, the content of Co is 0.28 mg / L, the content of Ni is 0.85 mg / L, the content of Cd is 0.13 mg / L, the content of Pb is 1.62 mg / L, the content of Hg is 0.01 mg / L, and the content of As is 0.26 mg / L.

[0118] The aforementioned method for treating arsenic-containing acidic wastewater employs a step-by-step treatment process of "alkaline adjustment - simultaneous heavy metal and arsenic removal - secondary deep arsenic removal," achieving simultaneous removal of heavy metals and arsenic. Compared to traditional segmented treatment processes, this significantly simplifies the operation process. Furthermore, each reaction stage is conducted under mild conditions of 20-50℃, eliminating the need for harsh conditions such as high temperature and high pressure, making operation simple and reducing production costs. Through a two-stage arsenic removal process design, the synergistic effect of primary arsenic removal and simultaneous heavy metal removal, coupled with the deep arsenic removal in the secondary stage, ensures complete arsenic removal. Simultaneously, it efficiently removes multiple heavy metal ions such as Cu, Co, Ni, Cd, Pb, and Hg, effectively solving the problem of treating complex pollution. Ultimately, the concentrations of arsenic and heavy metals in the filtrate consistently meet standards, resulting in highly reliable effluent quality.

[0119] Moreover, the treatment method for arsenic-containing acidic wastewater of the present invention has a simple process, is easy to operate, and has mild reaction conditions, which greatly reduces energy consumption, further reduces operating and treatment costs, and is easy to promote and apply on a large scale.

[0120] In summary, the above-described technical solutions of the present invention are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made using the contents of the present invention's specification and drawings under the technical concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for treating arsenic-containing acidic wastewater, characterized in that, Includes the following steps: S1: Add an alkaline agent to the acidic wastewater containing arsenic to adjust the pH to ≥ 8.5, and obtain alkaline wastewater; S2: Add a weight removal agent and a first arsenic removal agent simultaneously to the alkaline wastewater, and react at 20~50℃ to obtain a first mixed solution; S3: Add the second arsenic removal agent to the first mixed solution and react at 20~50℃ to obtain the second mixed solution; S4: The second mixed solution is subjected to pressure filtration to separate the filtrate and arsenic-containing sludge; The heavy metal content in the arsenic-containing acidic wastewater includes: Cu≥1mg / L, Co≥1.0mg / L, Ni≥0.5mg / L, Cd≥0.02mg / L, Zn≥4.0mg / L, Pb≥0.2mg / L, Hg≥0.01mg / L, and As≥0.1mg / L.

2. The method for treating arsenic-containing acidic wastewater according to claim 1, characterized in that, The alkaline agent includes one or more of sodium hydroxide and sodium carbonate.

3. The method for treating arsenic-containing acidic wastewater according to claim 1, characterized in that, The sludge removal agent includes one or more of the following compounds: aluminum salts, iron salts, trisodium trimercaptotriazine (TMT), and dithiocarbamates (DTC). The mass fraction of the active ingredient in the deweighting agent is 5-95%; The chemical composition of the sludge remover, by mass fraction, includes one or more of the following: 10-70% dithiocarbamate, 10-30% trithiotriazine trisodium salt, and 1-30% polyaluminum salt.

4. The method for treating arsenic-containing acidic wastewater according to claim 1, characterized in that, The first arsenic removal agent includes one or more of calcium oxide, calcium hydroxide, magnesium oxide, magnesium hydroxide, magnesium sulfate, polyaluminum sulfate, and polyferric sulfate.

5. The method for treating arsenic-containing acidic wastewater according to claim 1, characterized in that, The second arsenic removal agent includes one or more of sodium persulfate, ferric chloride, and hydrogen peroxide.

6. The method for treating arsenic-containing acidic wastewater according to claim 1, characterized in that, The mass ratio of the alkaline wastewater to the sludge removal agent is 100:(0.05~0.1); The mass ratio of the alkaline wastewater to the first arsenic removal agent is 100:(0.01~1); The mass ratio of the second mixed solution to the second arsenic removal agent is 100:(0.01~0.1).

7. The method for treating arsenic-containing acidic wastewater according to claim 1, characterized in that, The pH of the first mixed solution is 8.0~9.0; The pH of the second mixed solution is 6.0 to 9.

0.

8. The method for treating arsenic-containing acidic wastewater according to claim 1, characterized in that, The arsenic-containing acidic wastewater contains arsenic in the forms of trivalent and / or pentavalent arsenic, and also contains Cu. 2+ Ni 2+ Co 2+ Cd 2+ Zn 2+ Pb 2+ Hg 2+ One or more of them.

9. The method for treating arsenic-containing acidic wastewater according to claim 1, characterized in that, The filtrate contains the following heavy metals: Cu≤1mg / L, Co≤1mg / L, Ni≤0.5mg / L, Cd≤0.02mg / L, Zn<4mg / L, Pb≤0.2mg / L, Hg≤0.01mg / L, and As≤0.1mg / L.

10. The application of the filtrate obtained by the treatment method according to any one of claims 1 to 9, characterized in that, The filtrate is used for industrial circulating cooling, production process reuse, or discharge in compliance with standards.

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