High-arsenic water purification process

Abstract

The invention discloses a high-arsenic water purification process, and relates to the technical field of high-arsenic water purification. According to the method, Ca (OH) 2 is added into the wastewater, iron in the wastewater and AsO3 < 3-> and AsO4 < 3-> in the wastewater form a stable complex, and the stable complex is adsorbed and co-precipitated by hydroxide of iron to remove part of arsenic; sodium hydrosulfide is added into supernate according to the content of the copper element, copper is completely recycled, a small part of arsenic can be settled into copper concentrate at the same time, then sodium hydrosulfide is added again according to the content of the zinc element, zinc and arsenic in water are completely recycled at the moment, As < 5 + > is reduced into As < 3 + > through NaHS, As < 3 + > further reacts with sodium hydrosulfide to generate As2S3 sediment, and the As2S3 sediment is recycled. Therefore, the purpose of completely purifying the high-arsenic water is achieved. According to the method, the adding amount of sodium hydrosulfide can be accurately controlled according to the content of the copper element and the zinc element in the supernate, the purification effect can be improved to the maximum extent while chemicals are saved, copper and zinc in the supernate can be sequentially recycled by adding sodium hydrosulfide in batches, high-arsenic water can be completely purified, and treatment is comprehensive.

Description

Technical Field

[0001] The invention relates to the technical field of high-arsenic water purification, and in particular to a high-arsenic water purification process. Background Art

[0002] Most of the minerals of heavy metals such as copper, lead and zinc exist in the form of sulfides. During the smelting process, the sulfur in these sulfides is fully utilized to make industrial sulfuric acid or other products. However, when producing industrial sulfuric acid, a certain amount of acidic wastewater will be generated, containing arsenic up to 3000mg / L or more, which must be treated before it can be discharged or recycled.

[0003] In the document (application number: CN201110270354.4), a method for treating high-arsenic acid wastewater is disclosed, which adopts the following three steps: ① sulfidation reaction: adding sodium sulfide solution to high-arsenic acid wastewater, stirring, so that the arsenic, lead, and cadmium metal ions in the high-arsenic acid wastewater are precipitated in the form of sulfides, and the amount of sodium sulfide added is calculated according to the reaction equation according to the content of arsenic, lead, and cadmium heavy metals, and the excess is 10-20%; after the sodium sulfide solution is added, it is stirred for 30 minutes, and then pumped into a filter press for filtration; the sulfide slag after filtration is stored to recover arsenic and other metals; the filtrate of the sulfidation reaction is pumped into a primary neutralization reaction tank; ② Primary neutralization reaction: add lime milk to the filtrate of the sulfidation reaction and stir. When the pH value reaches 8, add the polyiron solution successively to further remove arsenic in the wastewater; the amount of polyiron added is calculated as 0.8 kg per cubic meter of the filtrate of the sulfidation reaction, and continue to add lime milk; when the pH value reaches 10, stop adding lime milk, continue stirring for 30 minutes, and filter press; the primary neutralization slag after filter press is stored, and the neutralization filtrate is pumped into the enhanced reaction tank; ③ Enhanced neutralization reaction: In the enhanced reaction tank, add polyiron solution at a ratio of 0.5kg polyiron per cubic meter of neutralization filtrate and stir; then adjust the pH value of the solution in the reaction tank with lime milk, stop adding lime milk when the pH value reaches 8-9, and continue stirring for 30 minutes; then add PAM flocculant at 0.02% of the solution in the tank, continue stirring for 10 minutes and then filter press; the enhanced neutralization residue after filter pressing is stored, and the enhanced neutralization filtrate is pumped into the general wastewater station for further treatment after inspection and meets the qualified discharge standards before discharge.

[0004] This patent uses sodium sulfide to remove arsenic. If the dosage, pH value and reaction time of sodium sulfide arsenic precipitation are not well controlled, the arsenic removal rate of sodium sulfide will be significantly reduced. (1) Dosage of sodium sulfide: Both literature and production practice indicate that even if sodium sulfide is used in excess many times during a single precipitation, arsenic cannot be removed to a very low level. (2) pH value: Sodium sulfide arsenic precipitation is carried out under acidic conditions. When the pH value is about 2, the arsenic precipitation effect is best. When the arsenic content in the sewage is too high, the arsenic precipitation efficiency decreases. When there is an excess of sodium sulfide and the alkalinity is strong, the negative charge on the surface of the adsorbent increases, the electrostatic repulsion between the negative charges increases, the adsorption amount decreases, and the arsenic precipitation efficiency decreases. (3) Reaction time: The sodium sulfide arsenic precipitation process is an ionic reaction. The reaction process is very rapid and the arsenic precipitation time should be controlled at about 40-60 minutes. However, in production practice, due to the limitations of objective conditions, the reaction time is too long. The presence of high-valent oxidized ions in the solution will re-dissolve the arsenic trisulfide precipitate, resulting in a decrease in the arsenic removal rate.

[0005] In the document (application number: CN202110533331.1), a treatment process for high-concentration arsenic-containing waste acid is disclosed, comprising the following steps: step S10, filtering the high-concentration waste acid stock solution through a filter and introducing it into a waste acid storage tank, stirring and mixing, and standing for 2 to 4 hours; Step S20, adding sodium hydrosulfide to a hydrogen sulfide gas generator, adding a dilute sulfuric acid solution with a concentration of 50%, and reacting sulfuric acid with sodium hydrosulfide to generate gas to produce hydrogen sulfide gas and sodium sulfate; Step S30, introducing the liquid in the waste acid storage tank into a sulfidation reactor through a centrifugal pump after solid-liquid separation by sedimentation, and then adding the hydrogen sulfide gas obtained in step S20, and circulating the high-concentration arsenic-containing waste acid through an internal circulation pump of the reactor, so that the hydrogen sulfide gas reacts with the heavy metals in the liquid to generate precipitation; Step S40, when the reaction reaches the end point, pumping it into a thickening tank through a drainage pump, and then processing it through a filter press to achieve solid-liquid separation and achieve standard discharge of the waste acid.

[0006] Although this process uses sodium hydrosulfide, it needs to be gasified. The process steps are complicated and the amount of sodium hydrosulfide added cannot be accurately controlled, which easily leads to waste. At the same time, wastewater usually contains copper and zinc elements. This process cannot recover the copper and zinc, and cannot fully treat and utilize wastewater resources. Summary of the invention

[0007] The purpose of the present invention is to solve the above problems and provide a high-arsenic water purification process.

[0008] In order to achieve the above-mentioned purpose, the present invention specifically adopts the following technical solutions: A high-arsenic water purification process comprises the following steps: S1. Add Ca(OH)2 to the wastewater, and the iron in the wastewater will react with AsO3 in the wastewater. 3- 、AsO4 3- It forms a stable complex and is adsorbed and co-precipitated by iron hydroxide to remove part of the arsenic. The main reaction is: Ca(OH)2+FeSO4=CaSO4+Fe(OH)2; Ca(OH)2+Fe2(SO4)3=CaSO4+Fe(OH)3; AsO4 3- +Fe(OH)3=FeAsO4+3OH - ; AsO3 3- +Fe(OH)3=FeAsO3+3OH - ; Fe 2+ It has strong reducing properties and is easily oxidized to Fe in solution. 3+ ; S2, adding an aeration device to the wastewater to remove iron; The main reaction is: 4Fe 2+ +O2+4H + →2Fe 3+ +2H2O; 2Fe 3+ +SO4 2- +3Ca(OH)2+6H2O→2Fe(OH)3+3CaSO4·2H2O; S3, in the supernatant of S2, sodium hydrosulfide is first added according to the copper content to completely recover the copper. This step will also precipitate a small amount of arsenic and zinc into the copper concentrate. Then sodium hydrosulfide is added again according to the zinc content. At this time, zinc and arsenic in the water are completely recovered. NaHS first removes As 5+ Reduction to As 3+ 、As 3+ It further reacts with sodium hydrosulfide to generate As2S3 precipitate, thus achieving the purpose of completely purifying high-arsenic water; The main reaction is: Cu 2+ +HS - =H + +CuS; Zn 2+ +HS - =H + +ZnS; NaHS+H3AsO4=H3AsO3+S+NaOH; 3NaHS+2H3AsO3=As2S3+3NaOH+3H2O.

[0009] Furthermore, sodium hydrosulfide is added to S3 at a dosing ratio of 140% according to the copper content.

[0010] Furthermore, sodium hydrosulfide is added to S3 at a dosing ratio of 600% according to the zinc content.

[0011] The beneficial effects of the present invention are as follows: 1. The present invention can not only quickly remove part of arsenic by adsorption and co-precipitation through the addition of calcium hydroxide, but also remove the iron element in the wastewater without affecting the subsequent recovery of copper concentrate and zinc concentrate. Then, sodium hydrosulfide is added in batches to sequentially recover copper and zinc in the supernatant, and high-arsenic water can be completely purified, with comprehensive treatment and high wastewater utilization rate.

[0012] 2. The present invention can accurately control the amount of sodium hydrosulfide added by adjusting the copper and zinc content of the supernatant, thereby saving reagents and maximizing the purification effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0014] To make the purpose, technical solution and advantages of the embodiments of the present invention more clear, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0015] Take dilute acid pickling wastewater (containing arsenic, iron, copper and zinc elements) as an example; Arsenic in wastewater mainly exists in the form of arsenous acid, metaarsenous acid and their salts. The following ionization equilibrium exists in the wastewater: 3H + +AsO3 3- =As(OH)3= As 3+ +3OH - ; 5H + +AsO4 3- = As 5+ + 3OH - +H2O; Embodiment 1

[0016] like Figure 1 As shown, a high arsenic water purification process comprises the following steps: S1. Add Ca(OH)2 to the wastewater, and the iron in the wastewater will react with AsO3 in the wastewater. 3- 、AsO4 3- It forms a stable complex and is adsorbed and co-precipitated by iron hydroxide to remove part of the arsenic. The main reaction is: Ca(OH)2+FeSO4=CaSO4+Fe(OH)2; Ca(OH)2+Fe2(SO4)3=CaSO4+Fe(OH)3; AsO4 3- +Fe(OH)3=FeAsO4+3OH- ; AsO3 3- +Fe(OH)3=FeAsO3+3OH - ; Fe 2+ It has strong reducing properties and is easily oxidized to Fe in solution. 3+ , so that the purpose is to remove iron first, in order to facilitate the subsequent recovery of copper concentrate and zinc concentrate; S2, adding an aeration device to the wastewater to remove iron; The main reaction is: 4Fe 2+ +O2+4H + →2Fe 3+ +2H2O; 2Fe 3+ +SO4 2- +3Ca(OH)2+6H2O→2Fe(OH)3+3CaSO4·2H2O; S3, in the supernatant of S2, sodium hydrosulfide is first added according to the copper content to completely recover the copper. This step will also precipitate a small amount of arsenic and zinc into the copper concentrate. Then sodium hydrosulfide is added again according to the zinc content. At this time, zinc and arsenic in the water are completely recovered. NaHS first removes As 5+ Reduction to As 3+ 、As 3+ It further reacts with sodium hydrosulfide to generate As2S3 precipitate, thus achieving the purpose of completely purifying high-arsenic water; The main reaction is: Cu 2+ +HS - =H + +CuS; Zn 2+ +HS - =H + +ZnS; NaHS+H3AsO4=H3AsO3+S+NaOH; 3NaHS+2H3AsO3=As2S3+3NaOH+3H2O. Embodiment 2

[0017] On the basis of the above embodiment, it also includes that sodium hydrosulfide is added in S3 at a dosing ratio of 140% according to the copper content.

[0018] Exploration on the recovery of copper with sodium hydrosulfide

[0019] Embodiment 3 On the basis of the above embodiment, it also includes that sodium hydrosulfide is added in S3 at a dosing ratio of 600% according to the zinc content.

[0020] Exploration on the Recovery of Zinc by Sodium Hydrosulfide

[0021] There is an obvious color darkening between 500% and 600%.

[0022] In summary, the experimental data obtained by using the addition ratios in Example 2 and Example 3 are as follows: Experimental data on purification of high arsenic water; (1) Take 800mL of raw water + 500mL of dilute acid leaching solution and measure Cu (the mixture is high arsenic water); (2) Iron area: Take 1200 mL of the solution, add lime milk until the pH is 3.0, filter and measure Cu and Zn; (3) Copper area: Based on the water sample volume and the measured Cu obtained in the previous step, add NaHS to collect copper according to the dosing ratio in the table, and measure Cu and Zn after filtering; (4) Zinc area: According to the water sample volume and the measured Zn obtained in the previous step, add NaHS to collect zinc according to the dosing ratio in the table, and measure Zn after filtering; Experimental table

[0023] Experimental data 1

[0024] Experimental data 2

[0025] Experimental data 3

[0026] Therefore, by adopting the purification process of the present invention, the dosage of the reagent, pH and reaction time can be accurately controlled, and the resources in the high-arsenic water can be fully recovered and utilized.

[0027] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A high-arsenic water purification process, characterized in that: The following steps are involved: S1. Add Ca(OH)2 to the wastewater, and the iron in the wastewater will react with AsO3 in the wastewater. 3- 、AsO4 3- It forms a stable complex and is adsorbed and co-precipitated by iron hydroxide to remove part of the arsenic. The main reaction is: Ca(OH)2+FeSO4=CaSO4+Fe(OH)2; Ca(OH)2+Fe2(SO4)3=CaSO4+Fe(OH)3; AsO4 3- +Fe(OH)3=FeAsO4+3OH - ; <h2 style=";text-align:left;direction:ltr">AsO3<h2 style=";text-align:left;direction:ltr"> 3- <h2 style=";text-align:left;direction:ltr"> +Fe(OH)3=FeAsO3+3OH<h2 style=";text-align:left;direction:ltr"> - <h2 style=";text-align:left;direction:ltr"> ; Fe 2+ It has strong reducing properties and is easily oxidized to Fe in solution. 3+ ; S2, adding an aeration device to the wastewater to remove iron; The main reaction is: 4Fe 2+ +O2+4H + →2Fe 3+ +2H2O; 2Fe 3+ +SO4 2- +3Ca(OH)2+6H2O→2Fe(OH)3+3CaSO4·2H2O; S3, in the supernatant of S2, sodium hydrosulfide is first added according to the copper content to completely recover the copper. This step will also precipitate a small amount of arsenic and zinc into the copper concentrate. Then sodium hydrosulfide is added again according to the zinc content. At this time, zinc and arsenic in the water are completely recovered. NaHS first removes As 5+ Reduction to As 3+ 、As 3+ It further reacts with sodium hydrosulfide to generate As2S3 precipitate, thus achieving the purpose of completely purifying high-arsenic water; The main reaction is: Cu 2+ +HS - =H + +CuS; Zn 2+ +HS - =H + +ZnS; NaHS+H3AsO4=H3AsO3+S+NaOH; 3NaHS+2H3AsO3=As2S3+3NaOH+3H2O.

2. A high-arsenic water purification process according to claim 1, characterized in that: Sodium hydrosulfide is added to S3 at a dosing ratio of 140% according to the copper content.

3. A high-arsenic water purification process according to claim 1, characterized in that: Sodium hydrosulfide is added to S3 at a dosing ratio of 600% according to the zinc content.

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