Step-by-step removal method for thallium and arsenic in lead-zinc smelting waste acid

Abstract

The invention discloses a step-by-step removal method for thallium and arsenic in lead-zinc smelting waste acid, which comprises the following steps: adding a calcium-containing precipitant into the lead-zinc smelting waste acid for neutralization and precipitation to obtain a neutralization and precipitation filtrate and a neutralization and precipitation filter residue; adding a calcium remover into the neutralized and precipitated filtrate to carry out calcium removal reaction to obtain calcium-removed filtrate and calcium-removed slag; adding an oxidizing agent I and a catalyst into the calcium-removed filtrate, controlling the pH value of the oxidation process to be 9.0-11.5 by using alkali liquor, carrying out selective oxidation thallium removal, and filtering to obtain thallium-removed filtrate and thallium-removed slag; and adding iron salt into the thallium-removed filtrate for deep arsenic removal to obtain effluent and arsenic-removed slag. According to the method, thallium and arsenic in the contaminated acid can be removed step by step, so that the concentration of arsenic and thallium in effluent stably reaches the standard for a long time while thallium slag and arsenic slag are separated.

Description

Technical Field

[0001] The invention belongs to the technical field of industrial wastewater treatment and relates to a step-by-step removal method of thallium and arsenic from lead and zinc smelting waste acid. Background Art

[0002] In the important industrial production process of lead and zinc smelting, the generation of waste acid is an issue that cannot be ignored. In daily operations, lead and zinc smelters continuously generate a large amount of waste acid. These waste acids contain complex components, among which high concentrations of harmful components are their prominent characteristics.

[0003] From the perspective of acid, the acid content in waste acid is high, which itself has corrosive hazards. Arsenic, fluorine, mercury, and heavy metal ions such as lead, zinc, cadmium, and thallium are extremely harmful to the environment and organisms. Long-term exposure to arsenic can cause irreversible damage to multiple organs of the human body, such as the liver and kidneys, and it is easy to accumulate in the environment, causing long-lasting and serious damage to the ecological environment such as soil and water bodies. Excessive fluoride ions can affect the health of the bones and teeth of organisms. The toxicity of mercury is well known. It can be continuously enriched in organisms through the food chain, causing serious damage to the nervous system. Heavy metal ions such as lead, zinc, cadmium, and thallium should not be underestimated. They will interfere with the normal physiological and biochemical processes in organisms.

[0004] At present, chemical precipitation is the most commonly used method for the treatment of waste acid. In this method, alkaline materials such as hydroxides and sulfides are usually used, and coagulants such as iron salts and alum (aluminum sulfate) are also used. The treatment process generally undergoes one or more stages of neutralization reactions. In this process, alkaline materials are added to neutralize the acidic substances in the waste acid. Aeration is then performed, which helps certain chemical reactions and the conversion of substances. This is followed by a sedimentation process, in which the formed precipitate will gradually sink, and then be filtered, and finally the precipitate is removed through solid-liquid separation to achieve the purpose of purifying the waste acid, so that the waste acid can meet the discharge standards.

[0005] However, this chemical precipitation method has many problems. Especially in the treatment of arsenic and thallium, even after treatment, it is still difficult to stably meet the emission standards. During the treatment process, due to the use of sulfides and the like for precipitation reactions, a large amount of arsenic-containing sulfide waste slag and thallium-containing waste slag will be produced. For the subsequent treatment of these waste slags, new challenges will be faced when conventional technologies such as lime stabilization and cement solidification are used. These technologies have the problem of high dosage of reagents, which not only increases the treatment cost, but also has poor disposal effects, and it is difficult to effectively avoid the harmful substances in the waste slag from seeping out again to cause secondary pollution to the environment. In summary, the existing waste acid treatment technology still has a lot of room for improvement, and new technical solutions are needed to solve these problems. Summary of the invention

[0006] In view of this, the purpose of the present invention is to provide a step-by-step removal method for thallium and arsenic in lead-zinc smelting waste acid. The method of the present invention can remove thallium and arsenic in the waste acid step by step, so that the thallium slag and arsenic slag are separated and the arsenic and thallium concentration in the effluent is stably up to the standard for a long time, thereby solving the problems of large reagent consumption, inability to deeply remove arsenic and thallium, and generation of a large amount of arsenic-containing sulfide waste slag and thallium-containing waste slag in the existing thallium and arsenic removal process in lead-zinc smelting waste acid.

[0007] In order to achieve the above technical purpose, the present invention provides a step-by-step removal method of thallium and arsenic in lead and zinc smelting waste acid, comprising the following steps:

[0008] 1) adding a calcium-containing precipitant to the lead-zinc smelting waste acid for neutralization precipitation to obtain a neutralization precipitation filtrate and a neutralization precipitation residue;

[0009] 2) adding a decalcifying agent to the neutralized precipitation filtrate to carry out a decalcification reaction to obtain a decalcified filtrate and a decalcified slag;

[0010] 3) adding an oxidant I and a catalyst to the decalcified filtrate, and using an alkali solution to control the pH value of the oxidation process to be between 9.0 and 11.5 to perform selective oxidation to remove thallium, and obtaining a thallium-removing filtrate and a thallium-removing slag after filtration;

[0011] 4) adding iron salt to the thallium removal filtrate to perform deep arsenic removal to obtain effluent and arsenic removal slag;

[0012] The oxidant I is ozone and / or sodium hypochlorite;

[0013] The catalyst is at least one of a manganese-containing compound, a titanium-containing compound and a lanthanum-containing compound.

[0014] The step-by-step removal method of thallium and arsenic in the lead-zinc smelting waste acid provided by the present invention is key to first removing sulfate and carbonate ions in the waste acid, and then combining a catalyst and an oxidant I to selectively oxidize and remove thallium in the waste acid and deeply remove arsenic, so as to achieve the effect of significantly reducing the amount of arsenic slag and thallium slag and long-term stable arsenic and thallium concentration in the effluent. Specifically, the present invention first precipitates and removes sulfate, fluorine, carbonate, lead, zinc, and cadmium ions in the waste acid by adding a calcium-containing precipitant; then adds a decalcifying agent to precipitate the calcium ions introduced by the calcium-containing precipitant; then, under the action of the catalyst and the oxidant I, the monovalent thallium in the decalcified filtrate is oxidized into trivalent thallium to generate thallium trioxide precipitation, and the thallium-containing precipitation is attached to the catalyst, and can be recycled in the system after filtration and separation, and the thallium content on the catalyst is continuously increased, and finally the mixture of the catalyst and thallium is discharged as needed. In this process, arsenic is oxidized to arsenate. Since the metal ions such as iron and calcium in the water that can generate precipitation with arsenate have been removed in the previous steps, arsenic slag will not be precipitated, which not only realizes the separation of arsenic slag and thallium slag, but also significantly reduces the amount of slag. At the same time, COD will also be oxidized and removed; finally, arsenic is converted into ferric arsenate precipitation and removed under the action of iron salt, and the excess iron is converted into ferric hydroxide precipitation, which plays a role of flocculation precipitation, thereby achieving the deep removal of arsenic. The oxidant I selected by the present invention has high oxidizability and does not introduce impurity ions into the system.

[0015] In the selective oxidation process of thallium removal in the present invention, OH is mainly used in an alkaline environment. - It reacts with oxidized thallium to generate thallium trioxide precipitate, but the control of the reaction pH value is crucial. Even if the selective oxidation process for thallium removal is in an alkaline environment, when the pH value is lower than the range of the present invention, the thallium content in the effluent process will not meet the discharge requirements. This is because when the pH is lower than the range of the present invention, thallium will change into other forms and dissolve, and when the pH value is higher than the range of the present invention, the consumption of alkali solution will be greatly increased, thereby increasing the treatment cost.

[0016] And the inventor found that the order of step 3 and step 4 in the present invention cannot be exchanged. If step 3 and step 4 are exchanged, iron salt is first added to the decalcification filtrate, and the pH value is adjusted to 4-6 with acid solution. The arsenic in the decalcification filtrate will be oxidized into arsenate and combined with iron to form ferric arsenate precipitation. At the same time, thallium is oxidized into trivalent thallium. Due to the flocculation and precipitation of ferric hydroxide, the ferric arsenate precipitation will also carry part of thallium with it, resulting in incomplete separation of arsenic and thallium. In addition, since the pH value range of the oxidation and thallium removal filtration process is 9.0-11.5, the decalcification filtrate needs to be adjusted to a pH of 4.0-6.0 with acid solution to remove arsenic and then needs to be adjusted to a pH of 9.0-11.5 with alkali solution to remove thallium for oxidation, which will increase the consumption of alkali solution and increase the processing cost.

[0017] As a preferred scheme, in the lead-zinc smelting waste acid, the concentration of sulfuric acid is 10-100 g / L, the concentration of chloride ions is 100-5000 mg / L, the concentration of fluoride ions is 100-2000 mg / L, the concentration of carbonate ions is 100-1000 mg / L, the concentration of arsenic ions is 1-1500 mg / L, the concentration of thallium ions is 0.1-500 mg / L, the concentration of lead ions is 1-200 mg / L, the concentration of zinc ions is 0.1-500 mg / L, the concentration of cadmium ions is 1-200 mg / L, and the COD concentration is 50-1000 mg / L.

[0018] As a preferred solution, the calcium-containing precipitant is calcium hydroxide and / or calcium carbonate; the pH of the neutralization precipitation is 10-11, and the time is 0.5-1h. By adding the calcium-containing precipitant and controlling the pH of the solution, sulfate, fluorine, carbonate, lead, zinc, and cadmium in the lead-zinc smelting waste acid can be removed simultaneously. If the pH value during the neutralization precipitation process is lower than the range of the present invention, the fluorine, lead, zinc, and cadmium in the lead-zinc smelting waste acid cannot be completely removed, and the residual metal ions will affect the subsequent step-by-step precipitation and separation of thallium and arsenic. When the pH value during the neutralization precipitation process is higher than the range of the present invention, excessive neutralization precipitant will be consumed, increasing the processing cost.

[0019] As a preferred solution, the decalcifying agent is at least one of air, carbon dioxide, sodium carbonate, sodium bicarbonate, potassium carbonate and potassium bicarbonate; the molar ratio of the decalcifying agent to the calcium ions in the neutralization precipitation filtrate is 1 to 1.5 times the theoretical reaction molar ratio; the conditions of the decalcification reaction are: pH value is 10 to 11.0, and the time is 0.5 to 2.5 hours. By adding the decalcifying agent, the calcium ions in the neutralization precipitation filtrate can generate calcium carbonate precipitate under the condition of pH value of 10.0 to 11.0, and the decalcified slag is obtained by filtration, thereby achieving the purpose of decalcification.

[0020] As a preferred solution, the alkali solution is sodium hydroxide and / or potassium hydroxide.

[0021] As a preferred solution, the molar ratio of the oxidant I to the thallium ions in the decalcification filtrate is 1 to 1.5 times the theoretical reaction molar ratio; the catalyst dosage is 0.2 mg / L to 20 g / L of the decalcification filtrate; and the selective oxidation time for thallium removal is 0.5 to 2.5 hours. When the dosage of the oxidant I and the time for selective oxidation for thallium removal are less than the scope of the present invention, the thallium in the decalcification filtrate cannot be effectively oxidized to convert it into thallium trioxide precipitation, and the thallium concentration of the effluent is stabilized to meet the standard. When the dosage of the oxidant I and the time for selective oxidation for thallium removal are greater than the scope of the present invention, the consumption of reagents will be increased, the processing cost will be increased, and the processing efficiency will be reduced.

[0022] As a preferred solution, the iron salt is at least one of ferrous sulfate, ferrous chloride, polyferric sulfate and ferric sulfate; when the iron salt is ferrous sulfate and / or ferrous chloride, at least one oxidant II selected from hydrogen peroxide, sodium hypochlorite and ozone needs to be added during the deep arsenic removal process.

[0023] As a preferred solution, the molar ratio of the iron ions in the iron salt to the arsenate ions in the thallium removal filtrate is 1.0 to 1.5 times the theoretical reaction molar ratio; the molar ratio of the oxidant II to the ferrous ions in the iron salt is 1.0 to 1.5 times the theoretical reaction molar ratio; the deep arsenic removal uses an acid solution to adjust the pH to 4.0 to 6.0, and the reaction time is 0.5 to 2.5 hours. The added oxidant II can oxidize the ferrous ions into trivalent ferrous ions, and the arsenate in the thallium removal filtrate is converted into ferric arsenate precipitate, and the excess iron salt will be fully converted into ferric hydroxide precipitate within the pH range and reaction time of the present invention, and play a role in flocculation precipitation to further remove arsenic. When the dosage of iron ions is too low, the arsenate in the thallium removal filtrate cannot be completely converted into ferric arsenate precipitate. When the iron salt is ferrous sulfate and / or ferrous chloride, and the dosage of oxidant II is too low, it is not enough to convert all ferrous ions into trivalent ferrous ions to combine with arsenate, thereby affecting the removal of arsenic in the thallium removal filtrate and causing the arsenic concentration in the effluent to fail to meet the standard.

[0024] As a preferred solution, the acid solution is hydrochloric acid and / or sulfuric acid.

[0025] As a preferred solution, the catalyst is at least one of manganese dioxide, manganese sulfate, manganese chloride, titanium dioxide, titanium trioxide, lanthanum trioxide and lanthanum chloride. The catalysts selected in the present invention all have high catalytic activity and achieve full catalytic oxidation of thallium.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1) The method provided by the present invention can make the effluent arsenic concentration lower than 0.3 mg / L, stably meeting the requirements of the "Lead and Zinc Industrial Pollutant Emission Standard" (GB25466-2010), and the effluent thallium concentration lower than 15 μg / L, stably meeting the pollutant limit requirements for the wastewater discharge outlet of the workshop or production facility specified in the amendment to the "Lead and Zinc Industrial Pollutant Emission Standard" (GB25466-2010).

[0028] 2) Compared with the chemical precipitation method, the method of the present invention can separate arsenic slag from thallium slag, and the separated arsenic slag can be recycled, while the amount of arsenic slag and thallium slag can be reduced by more than 50%.

[0029] 3) The present invention can not only convert arsenic into ferric arsenate precipitation and remove it by adding iron salt, but also convert excess iron into ferric hydroxide precipitation by adjusting the pH of the system, which also plays a role of flocculation precipitation, thereby achieving deep removal of arsenic.

[0030] 4) The present invention combines the catalyst and the oxidant I to selectively catalyze and oxidize thallium, thereby improving the oxidation efficiency. At the same time, the catalyst can be continuously recycled and reused in the catalytic oxidation system without affecting the treatment effect or increasing the cost of the agent. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0032] Figure 1 A process flow chart for removing arsenic and thallium from lead and zinc smelting waste acid provided in an embodiment of the present invention.

[0033] Figure 2 This is a process flow chart for removing arsenic and thallium from lead and zinc smelting waste acid provided in Comparative Example 2 of the present invention.

[0034] Figure 3 This is a process flow chart for removing arsenic and thallium from lead and zinc smelting waste acid provided in Comparative Example 3 of the present invention. DETAILED DESCRIPTION

[0035] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the protection scope of the present invention.

[0036] The present invention provides a step-by-step method for removing thallium and arsenic from lead and zinc smelting waste acid, comprising the following steps:

[0037] 1) Neutralization precipitation filtration: Add calcium-containing precipitant to the waste acid for neutralization precipitation filtration, control the pH value between 10.0 and 11.0, and obtain neutralization precipitation filtrate and neutralization precipitation residue.

[0038] 2) Decalcification reaction filtration: add a decalcification agent to the neutralization precipitation filtrate to carry out a decalcification reaction to obtain a decalcified filtrate and a decalcified slag.

[0039] 3) Oxidation and thallium removal filtration: add oxidant I and catalyst to the decalcified filtrate, and use alkali solution to control the pH value of the oxidation process between 9.0 and 11.5. After thallium removal filtration, thallium removal filtrate and thallium removal slag are obtained.

[0040] 4) Deep arsenic removal filtration: Add iron salt to the thallium removal filtrate, and adjust the pH value to 4.0-6.0 with acid solution. After stirring the reaction, perform deep arsenic removal filtration to obtain effluent and arsenic removal slag.

[0041] In the present invention, the sulfuric acid concentration of the lead-zinc smelting waste acid is preferably 10-100 g / L, specifically 10 g / L, 20 g / L, 40 g / L, 60 g / L, 80 g / L or 100 g / L; the chlorine concentration of the lead-zinc smelting waste acid is preferably 100-5000 mg / L, specifically 100 mg / L, 500 mg / L, 1000 mg / L, 2000 mg / L, 3000 mg / L, 4000 mg / L or 5000 mg / L; the fluorine concentration of the lead-zinc smelting waste acid is preferably 100-2000 mg / L. The carbonate concentration of the lead-zinc smelting waste acid is preferably 100-1000 mg / L, specifically 100 mg / L, 200 mg / L, 400 mg / L, 600 mg / L, 800 mg / L or 1000 mg / L; the arsenic concentration of the lead-zinc smelting waste acid is preferably 1-1500 mg / L, specifically 1 mg / L, 500 mg / L, 1000 mg / L or 1500 mg / L. 00mg / L; the thallium concentration of the lead-zinc smelting waste acid is preferably 0.1mg / L-500mg / L, specifically 0.1mg / L, 100mg / L, 200mg / L, 300mg / L, 400mg / L or 500mg / L; the lead concentration of the lead-zinc smelting waste acid is preferably 1-200mg / L, specifically 1mg / L, 50mg / L, 100mg / L, 150mg / L or 200mg / L; the zinc concentration of the lead-zinc smelting waste acid is preferably 0.1-500mg / L, specifically 0.1 mg / L, 100mg / L, 200mg / L, 300mg / L, 400mg / L or 500mg / L; the cadmium concentration of the lead-zinc smelting waste acid is preferably 1-200mg / L, specifically 1mg / L, 50mg / L, 100mg / L, 150mg / L or 200mg / L; the COD concentration of the lead-zinc smelting waste acid is 50-1000mg / L, specifically 50mg / L, 200mg / L, 400mg / L, 600mg / L, 800mg / L, 1000mg / L.

[0042] In step 1), the calcium-containing precipitant may be calcium hydroxide. By adding calcium hydroxide to the lead-zinc smelting waste acid for neutralization, precipitation and filtration, and controlling the reaction pH value to be 10.0-11.0, sulfate, fluoride, carbonate, lead, zinc and cadmium in the lead-zinc smelting waste acid can be removed. The reaction equations are shown in formulas (1) to (6):

[0043] Ca(OH) 2 +H 2 SO 4 →CaSO 4 ↓+2H 2 O (1)

[0044] Ca(OH) 2 +2HF→CaF 2 ↓+2H 2 O (2)

[0045] Ca(OH) 2 +2H + +CO 3 2- →CaCO 3 ↓+2H 2 O (3)

[0046] Pb 2+ +SO 4 2- →PbSO 4 ↓ (4)

[0047] Zn 2+ +2OH - →Zn(OH) 2 ↓ (5)

[0048] Cd 2+ +2OH - →Cd(OH) 2 ↓ (6)

[0049] In step 1), the pH value of the neutralization precipitation filtration is preferably controlled to be 10.0-11.0, specifically 10.0, 10.5, 11.0; the reaction time is preferably 0.5-1.0 h.

[0050] In step 2), a decalcifying agent is added to the neutralization precipitation filtrate to make the calcium ions in the neutralization precipitation filtrate generate calcium carbonate precipitate under the condition of pH value of 10.0-11.0, and decalcified slag is obtained by filtration to achieve the purpose of decalcification.

[0051] In step 2), the pH value of the decalcification reaction filtration is preferably controlled to be 10.0-11.0, specifically 10.0, 10.5, and 11.0. The molar ratio of calcium ions in the decalcification agent and the neutralization precipitation filtrate is 1.0-1.5 times the theoretical value, specifically 1.0 times, 1.1 times, 1.2 times, 1.3 times, 1.4 times, and 1.5 times. The reaction time is preferably 0.5h-2.5h, specifically 0.5h, 1.0h, 1.5h, 2.0h, and 2.5h.

[0052] In step 3), the oxidant I may be ozone, and the alkali solution may be sodium hydroxide. Ozone is introduced into the decalcification filtrate, and the reaction pH is adjusted to 9.0-11.5 with sodium hydroxide, so that the monovalent thallium in the decalcification filtrate can be oxidized into trivalent thallium to generate thallium trioxide precipitation, thereby obtaining oxidized thallium removal slag, and the trivalent arsenic in the decalcification filtrate is converted into pentavalent arsenic. The reaction equations are shown in formulas (7) and (8).

[0053] 6OH - +6Tl + +2O 3 →3Tl 2 O 3 ↓+3H 2 O (7)

[0054] 18OH - +3A S 3+ +O 3 →3AsO 4 3- +9H 2 O (8)

[0055] In step 3), the dosage of the oxidant I is 1 to 1.5 times the sum of the theoretical reaction molar ratios of arsenic, thallium and COD in the decalcification filtrate, specifically 1, 1.1, 1.2, 1.3, 1.4, and 1.5; the pH value of the oxidation to remove thallium is preferably controlled to be 9.0 to 11.5, specifically 9.0, 9.5, 10.0, 10.5, 11.0, and 11.5; the dosage of the catalyst is 0.2 mg / L to 20 g / L of the decalcification filtrate, specifically 0.2 mg / L, 0.2 g / L, 2 g / L, 10 g / L, and 20 g / L; the reaction time of the selective oxidation to remove thallium is preferably controlled to be 0.5 h to 2.5 h, specifically 0.5 h, 1.0 h, 1.5 h, 2.0 h, and 2.5 h.

[0056] In step 4), the iron salt may be ferrous sulfate, and the oxidant II may be hydrogen peroxide. Ferrous sulfate and hydrogen peroxide are added to the thallium removal filtrate, and the pH value is adjusted to 4.0-6.0 with acid to convert the arsenic in the calcium removal filtrate into ferric arsenate precipitate for removal, and at the same time, the excess iron is converted into ferric hydroxide precipitate, which also plays the role of flocculation precipitation. The reaction equations are shown in formula (9) and formula (10).

[0057] 2AsO 4 3- +2Fe 2+ +H 2 O 2 →2FeAsO 4 ↓+2OH - (9)

[0058] 2Fe 2+ +H 2 O 2 +4OH - →2Fe(OH) 3 ↓ (10)

[0059] In step 4), the pH value of the deep arsenic removal filtration is preferably controlled at 4.0-6.0, specifically 4.0, 4.5, 5.0, 5.5, and 6.0; the reaction time of the deep arsenic removal filtration is preferably 0.5h-2.5h, specifically 0.5h, 1.0h, 1.5h, 2.0h, and 2.5h; the molar ratio of iron ions in the iron salt to arsenate in the neutralization reaction filtrate is 1.0-1.5 times the reaction molar ratio, specifically 1.0, 1.1, 1.2, 1.3, 1.4, and 1.5; the molar ratio of the deep arsenic removal filtration oxidant II to the ferrous ions in the iron salt is 1.0-1.5 times the reaction molar ratio, specifically 1.0, 1.1, 1.2, 1.3, 1.4, and 1.5.

[0060] The present invention has no particular limitation on the sources of the above raw materials, which can be commercially available.

[0061] In order to further illustrate the present invention, a method for removing thallium and arsenic from waste acid in lead and zinc smelting is described in detail below in combination with the following embodiments and comparative examples, but they should not be construed as limiting the scope of protection of the present invention.

[0062] In the following embodiments and comparative examples provided by the present invention, the lead and zinc smelting waste acid used was taken from a smelter in Guangdong, with a sulfuric acid concentration of 70 g / L, chlorine 4899 mg / L, fluorine 1970 mg / L, carbonate 720 mg / L, arsenic 244 mg / L, thallium 0.480 mg / L, lead 80 mg / L, zinc 52 mg / L, cadmium 29 mg / L, and a COD concentration of 482 mg / L.

[0063] Example 1

[0064] A method for removing thallium and arsenic from lead and zinc smelting waste acid, the process flow chart is as follows Figure 1 As shown, Figure 1 In the diagram, a single underline indicates the material in the feed and process, and a double underline indicates the final discharge. The specific process is as follows:

[0065] Measure 2.0m 3 The pH value of the waste acid was adjusted to 11.0 with 20% lime slurry, consuming 653.67 kg of 20% lime slurry. After stirring for 0.5 h, the mixture was filtered to obtain 263.22 kg of neutralization precipitate residue and 2.40 m of neutralization precipitate filtrate. 3 . Neutralization precipitation can remove most of the sulfate, all of the carbonate, fluorine, lead, zinc and cadmium in the polluted acid. The neutralization precipitation residue contains 95.84wt% calcium sulfate dihydrate, 3.07wt% calcium fluoride, 0.91wt% calcium carbonate, 0.09wt% lead sulfate, 0.06wt% zinc hydroxide, 0.03wt% cadmium hydroxide. The sulfate concentration in the neutralization precipitation filtrate is 1600mg / L, the calcium concentration is 2876.05mg / L, the arsenic concentration is 203.60mg / L, the thallium concentration is 0.4mg / L, and the COD is 368mg / L. Then, 18.27kg of sodium carbonate solid is added to the neutralization precipitation filtrate at a molar ratio of carbonate to calcium of 1:1. The pH of the decalcification reaction is 11. After stirring the reaction for 0.5h, filter and remove the calcium ions in the water to obtain 2.39m of decalcified filtrate. 3 , decalcification slag (calcium carbonate) 17.23kg.

[0066] To 2.39m 3 Add 411.47 g / m3 of ozone to the decalcified filtrate at 1 times the theoretical value 3 , 0.47L of 0.05mol / L manganese sulfate solution was added at a catalyst dosage of 1.77mg / L to carry out ozone catalytic oxidation to remove thallium. The ozone aeration reaction time was controlled to be 1 hour. The pH value was monitored during the process, and 1mol / L sodium hydroxide solution was continuously added to control the pH value of the oxidation process to be around 11.0. After the aeration was completed, it was filtered to obtain 2.52m3 of thallium removal filtrate. 3 And 3.11g of thallium slag, the thallium slag contains 34.40wt% thallium oxide and 65.59wt% manganese dioxide, the thallium concentration of the oxidation and thallium removal filtrate is reduced to 13μg / L, the arsenic concentration is 193.90mg / L, and the COD is reduced to 30mg / L.

[0067] Use dilute sulfuric acid to adjust the pH value of the thallium removal filtrate to about 4.0, then add 2.35 kg of ferrous sulfate heptahydrate according to the molar ratio of iron to arsenate of 1.3, add 4.80 kg of 3% hydrogen peroxide according to the molar ratio of hydrogen peroxide to ferrous ions in iron salt of 0.5, that is, 1.0 times the theoretical reaction molar ratio of hydrogen peroxide to ferrous ions in iron salt, stir and react for 1 hour, filter, and obtain 1.48 kg (dry weight) of deep arsenic removal slag and 2.52 m3 of deep arsenic removal effluent. 3 The deep arsenic removal slag contains 85.80wt% of ferric arsenate and 14.20wt% of ferric hydroxide. The arsenic concentration in the effluent from the deep arsenic removal is 0.02mg / L, and the thallium concentration is 0.013mg / L.

[0068] Example 2

[0069] A method for removing thallium and arsenic from lead and zinc smelting waste acid, the process flow chart is as follows Figure 1 As shown, the specific process is as follows:

[0070] Measure 2.0m 3 The pH value of the waste acid was adjusted to 10.0 with 20% lime slurry, consuming 629.34 kg of 20% lime slurry. After stirring for 1.0 h, the mixture was filtered to obtain 251.73 kg of neutralization precipitate residue and 2.38 m of neutralization precipitate filtrate. 3 . Neutralization precipitation can remove most of the sulfate, all of the carbonate, fluorine, lead, zinc and cadmium in the polluted acid. The neutralization precipitation residue contains 95.83wt% calcium sulfate dihydrate, 3.08wt% calcium fluoride, 0.91wt% calcium carbonate, 0.09wt% lead sulfate, 0.06wt% zinc hydroxide, 0.03wt% cadmium hydroxide. The sulfate concentration in the neutralization precipitation filtrate is 1750mg / L, the calcium concentration is 1845.44mg / L, the arsenic concentration is 205.25mg / L, the thallium concentration is 0.40mg / L, and the COD is 405.45mg / L. Then, 17.44kg of sodium carbonate solid is added to 2.38L of the neutralization precipitation filtrate at a molar ratio of carbonate to calcium of 1.5:1. The pH of the decalcification reaction is 10. The calcium ions in the water are removed to obtain 2.38m of decalcified filtrate. 3 , decalcification slag (calcium carbonate) 10.97kg (dry weight).

[0071] To 2.38m 3 Ozone (617.73 mg / L) was added to the decalcified filtrate at 1.5 times the theoretical value, and 0.05 mol / L manganese sulfate solution (1.88 L) was added at a catalyst dosage of 7.10 mg / L to perform ozone catalytic oxidation to remove thallium. The ozone aeration reaction time was controlled to be 2.5 hours. The pH value was monitored during the process, and 1 mol / L sodium hydroxide solution was continuously added to control the pH value of the oxidation process to be around 10.0. After the aeration was completed, 2.48 m3 of thallium removal filtrate was obtained by filtration. 3The thallium precipitate is attached to the catalyst and recycled. The thallium concentration of the thallium oxidation filtrate is reduced to 15μg / L, the arsenic concentration is 197.12mg / L, and the COD is reduced to 30mg / L.

[0072] Use dilute sulfuric acid to adjust the pH value of the thallium removal filtrate to about 4.0, then add 2.72 kg of ferrous sulfate heptahydrate according to the ratio of iron to arsenate of 1.5, add 5.54 kg of 3% hydrogen peroxide according to the molar ratio of hydrogen peroxide to ferrous ions in iron salt of 0.5 (i.e. 1.0 times the theoretical reaction molar ratio of hydrogen peroxide to ferrous ions in iron salt), stir and react for 1 hour, filter, and obtain 1.62 kg (dry weight) of deep arsenic removal slag and 2.48 m3 of deep arsenic removal effluent. 3 The deep arsenic removal slag contains 78.40wt% ferric arsenate and 21.60wt% ferric hydroxide. The arsenic concentration in the effluent from the deep arsenic removal is 0.03mg / L, and the thallium concentration is 0.015mg / L.

[0073] The thallium precipitate attached to the catalyst was separated by filtration and recycled five times (2m 3 ), producing 13.53g of thallium slag, containing 39.54wt% thallium oxide and 60.46wt% manganese dioxide.

[0074] Example 3

[0075] A method for removing thallium and arsenic from lead and zinc smelting waste acid, the process flow chart is as follows Figure 1 As shown, the specific process is as follows:

[0076] Measure 2.0m 3 The pH value of the waste acid was adjusted to 11.0 with 20% lime slurry, consuming 653.67 kg of 20% lime slurry. After stirring for 0.5 h, the mixture was filtered to obtain 263.22 kg of neutralization precipitate residue and 2.40 m of neutralization precipitate filtrate. 3 . Neutralization precipitation can remove most of the sulfate, all carbonate, fluorine, lead, zinc and cadmium in the polluted acid. The neutralization precipitation residue contains 95.84wt% calcium sulfate dihydrate, 3.07wt% calcium fluoride, 0.91wt% calcium carbonate, 0.09wt% lead sulfate, 0.06wt% zinc hydroxide, 0.03wt% cadmium hydroxide, and the sulfate concentration in the neutralization precipitation filtrate is 1600mg / L, calcium concentration is 2876.05mg / L, arsenic concentration is 203.60mg / L, thallium concentration is 0.4mg / L, and COD is 368mg / L. Then, 23.78kg of potassium carbonate solid is added to the neutralization precipitation filtrate according to the molar ratio of carbonate to calcium of 1:1. The pH of the decalcification reaction is 11. After stirring the reaction for 0.5h, filter and remove calcium ions in the water to obtain 2.38L of decalcified filtrate and 17.23kg of decalcified residue (calcium carbonate).

[0077] To 2.38m 3Ozone (411.47 mg / L) was added to the decalcified filtrate at 1 times the theoretical value, and 47.6 kg of manganese dioxide solid was added at a catalyst dosage of 20 g / L to perform ozone catalytic oxidation to remove thallium. The ozone aeration reaction time was controlled to be 1 hour. The pH value was monitored during the process, and 1 mol / L sodium hydroxide solution was continuously added to control the pH value of the oxidation process to be around 11.0. After the aeration was completed, 2.52 m3 of thallium removal filtrate was obtained by filtration. 3 The thallium precipitate is attached to the catalyst and recycled. The thallium concentration of the thallium oxidation filtrate is reduced to 15μg / L, the arsenic concentration is 193.90mg / L, and the COD is reduced to 30mg / L.

[0078] Use dilute sulfuric acid to adjust the pH value of the thallium removal filtrate to about 6.0, then add 2.60kg of ferric sulfate according to the ratio of iron to arsenate ion of 1.0, and according to the theoretical reaction molar ratio of hydrogen peroxide and ferrous ion of 0, no need to add hydrogen peroxide, stir magnetically to react for 1 hour, filter, and obtain 1.27kg (dry weight) of deep arsenic removal slag (ferric arsenate) and 2.52m deep arsenic removal effluent. 3 After deep arsenic removal, the arsenic concentration in the effluent is 0.03 mg / L, and the thallium concentration is 0.015 mg / L.

[0079] The thallium precipitate attached to the catalyst was separated by filtration. After 60 days of circulation, 48.67 kg of thallium slag was produced, containing 2.20 wt% of thallium oxide and 97.80 wt% of manganese dioxide.

[0080] Example 4

[0081] A method for removing thallium and arsenic from lead and zinc smelting waste acid, the process flow chart is as follows Figure 1 As shown, the specific process is as follows:

[0082] Measure 2.0m 3 The pH value of the waste acid was adjusted to 11.0 with 20% lime slurry, consuming 653.67 kg of 20% lime slurry. After stirring for 0.5 h, the mixture was filtered to obtain 263.22 kg of neutralization precipitate residue and 2.40 m of neutralization precipitate filtrate. 3. Neutralization precipitation can remove most of the sulfate, all of the carbonate, fluorine, lead, zinc and cadmium in the polluted acid. The neutralization precipitation residue contains 95.84wt% calcium sulfate dihydrate, 3.07wt% calcium fluoride, 0.91wt% calcium carbonate, 0.09wt% lead sulfate, 0.06wt% zinc hydroxide, 0.03wt% cadmium hydroxide. The sulfate concentration in the neutralization precipitation filtrate is 1600mg / L, the calcium concentration is 2876.05mg / L, the arsenic concentration is 203.60mg / L, the thallium concentration is 0.4mg / L, and the COD is 368mg / L. Then, 18.27kg of sodium carbonate solid is added to the neutralization precipitation filtrate at a molar ratio of carbonate to calcium of 1:1. The pH of the decalcification reaction is 11. After stirring the reaction for 0.5h, filter and remove the calcium ions in the water to obtain 2.39m of decalcified filtrate. 3 , decalcification slag (calcium carbonate) 17.23kg.

[0083] To 2.39m 3 43.76 L of sodium hypochlorite solution (effective chlorine content 10%) was added to the decalcified filtrate at 1 times the theoretical value, and 1.88 L of 0.05 mol / L manganese sulfate solution was added at a catalyst dosage of 7.10 mg / L. The mixture was stirred for 0.5 hours, the pH value was monitored during the process, and the pH value of the reaction was adjusted to 9.0 with sodium hydroxide solution or dilute sulfuric acid. After the reaction was completed, the mixture was filtered to obtain 2.46 m3 of thallium oxide removal filtrate. 3 The thallium precipitate is attached to the catalyst and recycled. The thallium concentration of the thallium oxidation filtrate is reduced to 15μg / L, the arsenic concentration is 198.63mg / L, and the COD is reduced to 26mg / L.

[0084] Use dilute sulfuric acid to adjust the pH value of the thallium removal filtrate to about 6.0, then add 2.72 kg of ferrous sulfate heptahydrate according to the molar ratio of iron to arsenate ion of 1.5, and add 5.54 kg of 3% hydrogen peroxide according to the molar ratio of hydrogen peroxide to ferrous ion in iron salt of 0.5, stir magnetically to react for 1 hour, filter, and obtain 1.62 kg (dry weight) of deep arsenic removal slag and 2.46 m3 of deep arsenic removal effluent. 3 The deep arsenic removal slag contains 78.40wt% ferric arsenate and 21.60wt% ferric hydroxide. The arsenic concentration in the effluent from the deep arsenic removal is 0.02mg / L, and the thallium concentration is 0.015mg / L.

[0085] The thallium precipitate attached to the catalyst was filtered and separated, and then recycled five times (2 m 3 ), producing 13.53g of thallium slag, containing 39.54wt% thallium oxide and 60.46wt% manganese dioxide.

[0086] Comparative Example 1

[0087] The difference from Example 1 is that the pH of ozone oxidation is controlled to be 8.5. At this time, after 1 hour of ozone oxidation, the thallium concentration of the thallium removal filtrate is 0.096 mg / L, which cannot meet the treatment requirement of 0.015 mg / L.

[0088] Comparative Example 2

[0089] use Figure 2 The process shown for treating lead and zinc smelting waste acid is different from that in Example 1 in that, after neutralization, precipitation and filtration, sodium sulfide and iron salt are used to remove thallium and arsenic from the waste acid. The arsenic concentration of the effluent cannot be stably lower than 0.03 mg / L, and the thallium concentration of the effluent cannot be stably lower than 0.015 mg / L. The output of arsenic-thallium slag in the treatment process is 1650 g (dry weight) / t of waste acid, which is more than twice the slag output in Example 1 (740.55 g / t of waste acid).

[0090] Comparative Example 3

[0091] use Figure 3 The process shown for treating lead-zinc smelting waste acid is different from that in Example 1 in that, after the lead-zinc smelting waste acid is neutralized, precipitated and filtered, and calcium removal reaction is filtered, acid solution, iron salt and oxidant II are first added for arsenic removal treatment. At this time, arsenic and thallium in the decalcification filtrate are precipitated at the same time, and the slag obtained contains both arsenic and thallium. The arsenic slag cannot be directly recycled, and the amount of alkali solution used in the process is twice that of Example 1.

[0092] Comparative Example 4

[0093] use Figure 1 The process shown for treating lead and zinc smelting waste acid is different from that in Example 1 in that, after the lead and zinc smelting waste acid is filtered through neutralization precipitation, calcium removal reaction filtration and oxidation thallium removal filtration, ferrous sulfate is added to the thallium removal filtrate, and the pH value is adjusted to 4.0-6.0 with acid solution. At the same time, air is introduced as oxidant II for air aeration oxidation for 2.5 hours. The arsenic concentration of the effluent is 15.53 mg / L, which cannot meet the treatment requirement of arsenic concentration lower than 0.3 mg / L.

[0094] Combining Examples 1 to 4 and Comparative Example 1, it can be seen that controlling the pH value of ozone oxidation to remove thallium within the range of the present invention can ensure stable operation of the system, and the arsenic and thallium concentrations in the effluent meet the effluent requirements.

[0095] Combining Examples 1 to 4 and Comparative Example 2, it can be seen that if the present process is not used to treat lead and zinc smelting waste acid, arsenic and thallium will not stably meet the standards, and the amount of arsenic and thallium slag will increase, thereby increasing the treatment cost of arsenic and thallium slag.

[0096] It can be seen from Examples 1 to 4 and Comparative Example 3 that if the present process is not used to treat waste acid from lead and zinc smelting, the separation of arsenic slag and thallium slag cannot be achieved, and the amount of alkali solution used is greatly increased.

[0097] Combining Examples 1 to 4 and Comparative Example 4, it can be seen that using this process to treat lead and zinc smelting waste acid and using air instead of the oxidant II of the present invention for deep arsenic removal filtration will result in an effluent arsenic concentration higher than 0.3 mg / L, which does not meet the arsenic requirements for the treated effluent.

[0098] The above description of the disclosed embodiments enables those skilled in the art to experiment or use the present invention. Various modifications to these embodiments will be apparent to those 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 step-by-step method for removing thallium and arsenic from lead and zinc smelting waste acid, characterized in that: The following steps are involved: 1) adding a calcium-containing precipitant to the lead-zinc smelting waste acid for neutralization precipitation to obtain a neutralization precipitation filtrate and a neutralization precipitation residue; 2) adding a decalcifying agent to the neutralized precipitation filtrate to carry out a decalcification reaction to obtain a decalcified filtrate and a decalcified slag; 3) adding an oxidant I and a catalyst to the decalcified filtrate, and using an alkali solution to control the pH value of the oxidation process to be between 9.0 and 11.5 to perform selective oxidation to remove thallium, and obtaining a thallium-removing filtrate and a thallium-removing slag after filtration; 4) adding iron salt to the thallium removal filtrate to perform deep arsenic removal to obtain effluent and arsenic removal slag; The oxidant I is ozone and / or sodium hypochlorite; The catalyst is at least one of a manganese-containing compound, a titanium-containing compound and a lanthanum-containing compound.

2. The method for removing thallium and arsenic from lead and zinc smelting waste acid according to claim 1, characterized in that: In the lead-zinc smelting waste acid, the concentration of sulfuric acid is 10-100 g / L, the concentration of chloride ions is 100-5000 mg / L, the concentration of fluoride ions is 100-2000 mg / L, the concentration of carbonate ions is 100-1000 mg / L, the concentration of arsenic ions is 1-1500 mg / L, the concentration of thallium ions is 0.1-500 mg / L, the concentration of lead ions is 1-200 mg / L, the concentration of zinc ions is 0.1-500 mg / L, the concentration of cadmium ions is 1-200 mg / L, and the COD concentration is 50-1000 mg / L.

3. The method for removing thallium and arsenic from lead and zinc smelting waste acid according to claim 2, characterized in that: The calcium-containing precipitant is calcium hydroxide and / or calcium carbonate; the pH of the neutralization precipitation is 10-11.0, and the time is 0.5-1h.

4. A step-by-step method for removing thallium and arsenic from lead and zinc smelting waste acid according to any one of claims 1 to 3, characterized in that: The decalcifying agent is at least one of air, carbon dioxide, sodium carbonate, sodium bicarbonate, potassium carbonate and potassium bicarbonate; the molar ratio of the decalcifying agent to calcium ions in the neutralized precipitation filtrate is 1 to 1.5 times the theoretical reaction molar ratio; the conditions of the decalcification reaction are: pH value is 10 to 11.0, and the time is 0.5 to 2.5 hours.

5. The method for removing thallium and arsenic from lead and zinc smelting waste acid according to claim 4, characterized in that: The alkali solution is sodium hydroxide and / or potassium hydroxide.

6. The method for removing thallium and arsenic from lead and zinc smelting waste acid according to claim 1, characterized in that: The dosage of the oxidant I is 1 to 1.5 times the sum of the theoretical reaction molar ratios of arsenic, thallium and COD in the decalcified filtrate; The catalyst dosage is 0.2mg / L to 20g / L of the decalcified filtrate; The time for the selective oxidation to remove thallium is 0.5 to 2.5 hours.

7. The method for removing thallium and arsenic from lead and zinc smelting waste acid according to claim 1, characterized in that: The iron salt is at least one of ferrous sulfate, ferrous chloride, polyferric sulfate and ferric sulfate; When the iron salt is ferrous sulfate and / or ferrous chloride, at least one oxidant II selected from hydrogen peroxide, sodium hypochlorite and ozone needs to be added during the deep arsenic removal process.

8. The method for removing thallium and arsenic from lead and zinc smelting waste acid according to claim 7, characterized in that: The molar ratio of the iron ions in the iron salt to the arsenate ions in the thallium removal filtrate is 1.0 to 1.5 times the theoretical reaction molar ratio; The molar ratio of the oxidant II to the ferrous ions in the iron salt is 1.0 to 1.5 times the theoretical reaction molar ratio; The deep arsenic removal adopts acid solution to adjust the pH to 4.0-6.0, and the reaction time is 0.5-2.5h.

9. A step-by-step method for removing thallium and arsenic from lead and zinc smelting waste acid according to claim 1 or 6, characterized in that: The catalyst is at least one of manganese dioxide, manganese sulfate, manganese chloride, titanium dioxide, titanium trioxide, lanthanum trioxide and lanthanum chloride.

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