CN111018229B - Method for resource utilization of sulfuric acid waste acid wastewater from copper smelting and obtaining arsenic-containing product - Google Patents
Method for resource utilization of sulfuric acid waste acid wastewater from copper smelting and obtaining arsenic-containing product Download PDFInfo
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Abstract
The invention belongs to the technical field of industrial sewage treatment, and particularly discloses a method for resource utilization of sulfuric acid waste acid wastewater from copper smelting and obtaining arsenic-containing products, which comprises the following steps: 1. oxidizing trivalent arsenic: the waste acid and waste water is oxidized by air and hydrogen peroxide in sequence. 2. Arsenic and fluorine-chlorine separation: and after oxidation, carrying out negative pressure evaporation to obtain a fluorine-chlorine-containing condensate A, a concentrated solution B and arsenic pentoxide crystals. 3. Fluorine and chlorine separation: and absorbing the condensate A by using magnesium oxide to obtain a magnesium fluoride product and dilute hydrochloric acid. 4. Recovering valuable metals: and adding a sodium sulfide solution into the concentrated solution B to obtain valuable metal precipitate and arsenic-containing waste liquid C, wherein the valuable metal precipitate can be recycled and refined. 5. And (3) crystallization: adding flake caustic soda or recycled concentrated alkali liquor E into the arsenic-containing waste liquid C, adjusting the pH to 13.5-14.0 to obtain a sodium arsenate product and a crystallization filtrate D, and concentrating the crystallization filtrate D to obtain a sodium sulfate product and concentrated alkali liquor E. The invention recycles the resources of the sulfuric acid waste acid wastewater and obtains arsenic pentoxide and sodium arsenate products.
Description
Technical Field
The invention relates to the technical field of industrial sewage treatment, in particular to a method for utilizing sulfuric acid waste acid wastewater resources in copper smelting and obtaining arsenic-containing products.
Background
Sulfuric acid waste acid widely exists in the copper smelting industry, has the characteristics of high acidity, arsenic, fluorine and chlorine and other valuable metal elements, and is one of the most difficult-to-treat wastewater in the copper smelting industry. The traditional techniques for treating this waste water are the sulfidation process and the limemite process, which both enable the sulfuric acid waste water to reach the national discharge standard. However, with the stricter environmental laws and regulations, the emission after reaching the standard can not meet the current environmental protection requirements, and the resource recycling of sulfuric acid waste acid is in the trend.
At present, the sulfuric acid waste acid resource recycling treatment technology comprises two technologies, one technology is 'sulfuration arsenic removal, hot air blowing fluorine and chlorine removal and acid concentration recycling', and the other technology is 'evaporation concentration fluorine and chlorine removal, sulfuration arsenic removal and acid concentration recycling'. The former has the following technical difficulties: firstly, valuable metal elements in the waste acid cannot effectively distinguish the boundary points of arsenic sulfide and sulfides of other valuable metals due to relatively low concentration, so that the valuable metals cannot be recycled; secondly, after the acid is concentrated, the arsenic content in the concentrated solution exceeds the national standard, and the concentrated solution can be recycled after further arsenic removal by vulcanization; thirdly, the efficiency of blowing fluorine and chlorine by hot air is lower, and the consumed hot air quantity is larger. The latter has the technical difficulties that: firstly, the cost of the sulfuration treatment is relatively high, and the generated arsenic sulfide slag is extremely difficult to treat. Secondly, while negative pressure evaporation is carried out, arsenic and fluorine and chlorine enter the condensate together, the proportion of the arsenic escaping to the condensate can reach 20 percent at most, the condensate cannot be recycled, and the arsenic and the chlorine can be treated only by adding calcium, so that more arsenic-containing calcium slag is generated; (Shenpalant. research on a waste acid treatment technology generated by acid preparation through colored smelting flue gas [ C ]2011.) and (Liudao since Liudao, experimental research on evaporation concentration and fluorine, chlorine and arsenic removal of copper smelting waste acid [ D ] 2014.).
Therefore, how to efficiently realize the separation of arsenic and fluorine and chlorine, the recovery of valuable metals in waste acid, the generation of no arsenic sulfide slag and the realization of the production of arsenic is significant.
Disclosure of Invention
The invention aims to provide a novel method for resource utilization of copper smelting sulfuric acid waste water and obtaining arsenic-containing products aiming at the problems in the prior art and the special water quality condition of the sulfuric acid waste water, wherein the sulfuric acid waste water is sulfuric acid waste water generated in the sulfuric acid production process of copper smelting enterprises, and is called 'waste acid' for short. The arsenic content in the waste acid is 5-10 g/L; the content of chloride ion is 0-10g/L (preferably 0 is not taken); the content of fluorine ions is 0-5g/L (preferably 0 is not selected), and the total content of valuable metal elements is 0.5-5g/L (preferably 0.8-2 g/L);
the valuable metal elements include, but are not limited to, copper, lead, cadmium, zinc.
The invention adopts the following technical scheme to achieve the purpose of the invention.
A method for utilizing copper smelting sulfuric acid waste acid wastewater resources and obtaining arsenic-containing products sequentially comprises the following steps:
(1) and (3) an oxidation stage: carrying out air aeration on the waste acid in a waste acid and waste water storage tank, wherein the gas-liquid ratio is 1.0, the aeration time is 5-15h, and the dissolved oxygen in the solution after aeration is 8.5-9.5 mg/L; and adding 8-10% of hydrogen peroxide by mass into the aerated waste acid water to further oxidize trivalent arsenic in the waste acid.
The ratio of the amount of the hydrogen peroxide in the added hydrogen peroxide to the amount of the trivalent arsenic in the waste acid after aeration is (1-1.3): 1.
the hydrogen peroxide is added from the bottom of the hydrogen peroxide oxidation reaction device in two steps, wherein the adding amount in the first step is 70-80% of the total adding amount, and the rest hydrogen peroxide is added in the second step;
measuring the pH value of the waste acid after the hydrogen peroxide is oxidized;
if the pH value is more than or equal to 1.0, adding sulfuric acid with the concentration of not less than 95wt% until the pH value is less than 1.0, and then entering the step (2);
if the pH value is measured to be less than 1.0, directly entering the step (2);
(2) arsenic and fluorine-chlorine separation and concentration stage: and (2) carrying out negative pressure forced evaporation (concentration multiple is 6.0-8.0 times) on the waste acid oxidized in the step (1) at-0.1 MPa (when the air pressure value in the application document is negative, the air pressure value is recorded by taking standard atmospheric pressure as reference and marking the standard atmospheric pressure as 0) and at 75 ℃ to obtain concentrated solution B, arsenic pentoxide crystals and fluorochlorohydrin-containing condensate A.
Temporarily storing the concentrated solution B in a transfer tank, wherein 40-60% of the concentrated solution B is sent to the waste acid wastewater storage tank in the step (1) for adjusting the acidity of the waste acid wastewater and further improving the crystallization rate of arsenic pentoxide; the rest is sent to the step (4) for valuable metal recovery;
arsenic crystallization rate (%) (M)1*C1)/(C2*V1)，M1Is arsenic pentoxide mass; c1Is the mass percentage content of arsenic element in arsenic pentoxide; c2Is the mass volume concentration, V, of the arsenic element in the waste acid after the oxidation of the hydrogen peroxide1The volume of the waste acid after being oxidized by hydrogen peroxide;
the purity of the obtained arsenic pentoxide crystal is more than or equal to 90 percent, and the arsenic pentoxide crystal can be used as an arsenic-containing material product or provides a raw material for extracting metal arsenic;
the content of arsenic in the condensate A is less than or equal to 0.01mg/L, and the escape rate of the arsenic is less than or equal to 0.0001%;
(V) escape rate of arsenic2*C3)/(C2*V1)，V2Volume of condensate A, C3The mass volume concentration of the arsenic element in the condensate A;
in the step (2), the fluorine removal rate is more than or equal to 99 percent, and the chlorine removal rate is more than or equal to 95 percent.
(3) And (3) a condensate fluorine-chlorine separation stage: and (4) performing two-stage absorption on the condensate A by using the magnesium oxide suspension to obtain a magnesium fluoride product and a dilute hydrochloric acid solution. And (3) allowing the clear liquid of the condensate after the first-stage absorption to flow into the second stage, allowing magnesium fluoride precipitate generated after the second-stage absorption to flow back to the first stage, and performing solid-liquid separation on the magnesium fluoride precipitate in the first stage. The clear liquid generated after the second-stage absorption is dilute hydrochloric acid solution;
the pH value of the first-stage absorption reaction is controlled to be 1.5-2.5 by controlling the adding amount of the magnesium oxide suspension, and the pH value of the second-stage absorption reaction is controlled to be 3.0-3.5.
The purity of the magnesium fluoride product is more than or equal to 99.9 percent.
The supernatant produced after the second stage absorption can be treated in two ways, a and B:
A. concentrating to obtain concentrated hydrochloric acid and fresh water (the concentration process is to enrich salt (such as HCl) in the second-stage clear liquid) to obtain fresh water with low salt and concentrated hydrochloric acid with high salt (corresponding equipment is provided with a rectifying device, electrodialysis and the like), wherein the concentrated hydrochloric acid can be used for extracting rare and precious metals, and the fresh water is used as system water for recycling;
B. it is reused for preparing the magnesium oxide suspension.
The mass percentage of the magnesium oxide in the magnesium oxide suspension is 5-15%, preferably 10%.
(4) And (3) recovering valuable metals: distributing and adding sodium sulfide into the residual concentrated solution B in the step (2) to recover more than 99% of valuable metals, and obtaining sulfide precipitates and arsenic-containing waste liquid C of the valuable metals;
firstly, adding sodium sulfide until the pH value is 2.1-2.5, and obtaining and separating and recovering copper sulfide;
step two, continuously adding sodium sulfide until the pH value is 2.7-3.2, and separating and recovering lead sulfide;
thirdly, continuously adding sodium sulfide until the pH value is 3.5-4.5, and separating and recovering cadmium sulfide;
step four, continuously adding sodium sulfide until the pH value is 5.0-6.0, and separating and recovering zinc sulfide;
the purity of the copper sulfide is more than or equal to 95%, the purity of the lead sulfide is more than or equal to 96%, the purity of the cadmium sulfide is more than or equal to 97%, and the purity of the zinc sulfide is more than or equal to 97%.
The purity of the metal sulfide precipitate is over 95 percent, and the metal sulfide precipitate can be recycled and re-refined.
(5) And (3) a crystallization stage: adding flake caustic soda and/or recycled concentrated alkali liquor E into the arsenic-containing waste liquid C, adjusting the pH value to 13.5-13.8, reacting for 2 hours to obtain a sodium arsenate product and a crystallized filtrate D, concentrating the crystallized filtrate D to 2-3 times of concentration to obtain a sodium sulfate product and concentrated alkali liquor E, and recycling the concentrated alkali liquor E for adjusting the pH value of the arsenic-containing waste liquid C (the dosage of the flake caustic soda in the step (5) is larger for the first time, the consumption of the flake caustic soda in the subsequent steps is smaller, and the pH value is mainly adjusted by the recycled concentrated alkali liquor E).
The concentration of the sodium sulfate in the crystallization filtrate D in the step (5) is 200-300 g/L.
The purity of the sodium arsenate product is more than or equal to 90 percent, and the sodium arsenate product can be used as an arsenic-containing material product or provides a raw material for extracting metal arsenic.
The purity of the sodium sulfate product is more than or equal to 95 percent, and the sodium sulfate product can be used as an industrial sodium sulfate product.
Compared with the prior art, the treatment method for utilizing the copper smelting sulfuric acid waste acid wastewater resource and obtaining the arsenic-containing product has the following advantages and beneficial effects:
1. no generation of waste slag
The traditional treatment method of sulfuric acid waste acid is to react lime or a vulcanizing agent with arsenic to generate calcium arsenate or arsenic sulfide slag. The arsenic slag belongs to hazardous waste, needs to be subjected to stable solidification treatment, is subjected to safe landfill by a newly-built safe landfill site, and is expensive in stable solidification cost and extremely large in land occupation area of the landfill site. In the invention, only arsenic pentoxide and sodium arsenate products are produced, the purity of the arsenic pentoxide and sodium arsenate products is over 90 percent, and the arsenic pentoxide and sodium arsenate products can be used as arsenic-containing material products or provide raw materials for extracting metal arsenic. Meanwhile, the magnesium fluoride and the sodium sulfate in the invention both meet the corresponding industrial grade quality requirements and can be sold to the outside.
2. The condensate has low arsenic content and high fluorine and chlorine removal rate
In the invention, after trivalent arsenic is oxidized by polluted acid through air and hydrogen peroxide, the arsenic in the condensate is lower than 0.01mg/L, and the escape rate of the arsenic is less than 0.0001%. The escape rate of the arsenic is far lower than that of 20mg/L or 20 percent of arsenic in condensate in the traditional process. This is because trivalent arsenic has a low boiling point and is easily volatilized under evaporation conditions. And pentavalent arsenic has a high boiling point and is not easily volatilized under evaporation conditions.
Under negative pressure conditions, the rate and total amount of hydrogen fluoride and hydrogen chloride overflowing from the solution are both greater and higher than under normal pressure conditions. The fluorine removal rate is more than or equal to 99 percent, and the chlorine removal rate is more than or equal to 95 percent. Far higher than 88% of the fluorine removal rate and 77% of the chlorine removal rate in the traditional process (great bloom, summer bloom, Liu Xiao Lai., Experimental research on evaporation concentration treatment of smelting waste acid [ J ]. Zhejiang chemical industry, 2015 (8): 44-48.)
3. No waste water discharge
In the traditional process, the condensate is high in arsenic content, and alkaline substances such as lime and the like are adopted for arsenic removal treatment, and hydrogen fluoride and hydrochloric acid in the condensate are neutralized, so that a large amount of arsenic-containing waste residues and wastewater are generated and discharged. According to the invention, magnesium oxide suspension is adopted for defluorination treatment to obtain magnesium fluoride with high purity and a dilute hydrochloric acid solution, the dilute hydrochloric acid solution can be used for extracting rare and precious metals after concentration, and the concentrated fresh water can be used as system water supplement for recycling.
4. Recovery of valuable metals from waste acid
The content of valuable metals in the contaminated acid is low, and arsenic mainly exists in a trivalent arsenic form. In the process of removing arsenic by a sulfuration method, arsenic and valuable metals form sulfides together, and the arsenic and the valuable metals are extremely difficult to separate. In the invention, trivalent arsenic in the waste acid is oxidized into pentavalent arsenic, valuable metals are enriched after being concentrated under negative pressure, and the pentavalent arsenic cannot react with sodium sulfide to generate corresponding precipitates in the process of a vulcanization method, so that the separation of the valuable metals and the arsenic is finally realized. Meanwhile, one or more valuable metals can be recycled step by step according to the characteristics of the waste acid wastewater.
5. High arsenic crystallization rate and low arsenic content in crystallization filtrate
In the invention, the concentration of sodium sulfate in the alkaline crystallization filtrate D is very high and is 200-300 g/L. It can reduce the solubility of sodium arsenate in alkaline solution, so the arsenic content in the crystallization filtrate D is less than 0.2mg/L, the pH is 13.5-13.8 (the alkalinity is 12.6-25.2g/L), which is far lower than that in the traditional alkaline crystallization process, the alkalinity is 80g/L, and the arsenic content in the crystallization filtrate is 10-100 mg/L. Meanwhile, the arsenic content in the crystallization filtrate D is low, so that powerful guarantee is provided for obtaining an industrial-grade sodium sulfate product with high purity.
Drawings
FIG. 1 is a schematic diagram of a basic flow of a treatment method for resource utilization of sulfuric acid waste water from copper smelting and obtaining arsenic-containing products according to the present invention;
FIG. 2 is an XRD pattern of the arsenic pentoxide crystals obtained in example 1, and the characteristic peaks are matched with a standard pattern (PDF # -21-0056) by comparison;
FIG. 3 is the XRD pattern of sodium arsenate obtained in example 1, and the comparison shows that the characteristic peaks are consistent with the standard pattern (PDF # -24-0903).
Detailed Description
The applicant will further describe the technical solutions of the present invention with reference to specific examples, but the scope of the present invention is not limited to these examples. All changes, modifications and equivalents that do not depart from the spirit of the invention are intended to be included within the scope thereof.
Example 1
In the embodiment, sulfuric acid waste acid wastewater discharged from a sulfuric acid workshop of a copper smelting plant in Hubei is taken as a treatment object, the arsenic content is 5.5g/L, the fluorine ion concentration is 1.4g/L, the chlorine ion concentration is 3.0g/L, the copper content is 650mg/L, the lead content is 30mg/L, the cadmium content is 124mg/L, the zinc content is 287mg/L, and the pH value is 1.5.
A method for utilizing sulfuric acid waste acid wastewater resources in the copper smelting industry and obtaining arsenic-containing products comprises the following steps:
(1) and (3) an oxidation stage: taking 1L of waste acid wastewater, placing the waste acid wastewater in a waste acid storage tank for air aeration, wherein the gas-liquid ratio is 1.0, the air aeration time is 10 hours, and the dissolved oxygen in the solution after aeration is 9.1 mg/L;
the waste acid water after aeration flows into a hydrogen peroxide reaction tank, 8 wt% hydrogen peroxide is added into the bottom of the hydrogen peroxide reaction tank in two sections, the adding amount of the hydrogen peroxide in the first section is 4 times of that in the second section, the reaction time of each section is 1 hour, and the ratio of the total amount of hydrogen peroxide in the two sections to the amount of trivalent arsenic in the waste acid water is 1.1: 1;
after the oxidation is finished, the pH value of the waste acid is 2.1, wherein the content of trivalent arsenic is 2.2 mg/L;
and (3) adding 20mL of concentrated sulfuric acid (98 wt%) into the oxidized waste acid to adjust the pH to 0.9, and entering the step (2).
(2) Arsenic and fluorine-chlorine separation and concentration stage: and (2) carrying out negative pressure forced evaporation on the waste acid oxidized in the step (1) at-0.1 MPa and 75 ℃, wherein the concentration multiple is 6.7 times, the arsenic content in the obtained condensate A is 0.004mg/L, the arsenic escape rate is 0.00006%, the removal rate of chlorine in the waste acid in the step is 95.3%, the removal rate of fluorine in the waste acid in the step is 99.2%, the crystallization rate of arsenic in the waste acid in the step is 72%, and the purity of the obtained arsenic pentoxide is 96%.
And (3) the obtained concentrated solution is called as a concentrated solution B, and half of the concentrated solution B is sent to the waste acid storage tank in the step (1) for adjusting the pH value of the waste acid and further oxidizing and crystallizing.
(3) And (3) a condensate fluorine-chlorine separation stage: performing two-stage absorption on the condensate A by using a magnesium oxide suspension with the mass fraction of 10%, wherein the reaction time of each stage is 2 hours respectively, and obtaining a magnesium fluoride product and a dilute hydrochloric acid solution;
specifically, the method comprises the following steps: and (3) allowing the clear liquid of the condensate A after the first-stage absorption to flow into the second stage, allowing magnesium fluoride precipitate generated after the second-stage absorption to enter the first stage, and performing solid-liquid separation on the magnesium fluoride precipitate in the first stage. The pH value of the first stage reaction is 1.7, and the pH value of the second stage reaction is 3.0 (the dosage of the magnesium oxide suspension is controlled by an on-line pH meter); the second-stage clear liquid is a dilute hydrochloric acid solution, can be used for extracting rare and precious metals after concentration, and the produced fresh water is used as system water for recycling (a rectification device is used for concentration);
part of the second-stage clear liquid is recycled for preparing the magnesium oxide suspension;
in the step, the removal rate of the fluorinion is 92.4 percent, and the purity of the magnesium fluoride is 99.9 percent.
(4) And (3) recovering valuable metals: respectively recovering valuable metals from the concentrated solution B left in the step (2) by adding sodium sulfide step by step, wherein the end point pH value of copper recovery is 2.3, the end point pH value of lead recovery is 2.8, the end point pH value of cadmium recovery is 3.5, and the end point pH value of zinc recovery is 5.2;
the purity of copper sulfide, lead sulfide, cadmium sulfide and zinc sulfide obtained by separating and drying the precipitates obtained in each step is 98.5%, 99.6%, 98.9%, 99.2% and 99.5% respectively.
And removing all valuable metal precipitates to obtain arsenic-containing waste liquid C.
(5) And (3) a crystallization stage: adding caustic soda flakes into the arsenic-containing waste liquid C to adjust the pH value to 13.5, and continuing to react for 2 hours to obtain a sodium arsenate product and a crystallization filtrate D, wherein the arsenic content is 0.13mg/L, the sodium sulfate content is 243g/L, and concentrating the crystallization filtrate D to 2.2 times of concentration to obtain a sodium sulfate product and a concentrated alkali liquor E;
the concentrated lye E can be reused in step (5) instead of the flake caustic.
The purity of the obtained sodium arsenate product is 93 percent, and the purity of the sodium sulfate product is 95.7 percent.
The following comparative examples 1 to 4 were all used for comparison with example 1
Comparative example 1 (dirty acid not oxidized)
Essentially the same procedure as in example 1, except that: omitting the step (1), wherein the arsenic content in the condensate in the step (2) is 4.2g/L, and the escape rate of arsenic is 66%; the final pH value of the copper recovered in the step (4) is 2.3, the content of copper sulfide in the precipitate is only 12%, the content of arsenic sulfide is 88%, and the copper and arsenic cannot be effectively separated.
COMPARATIVE EXAMPLE 2 (atmospheric pressure evaporative concentration)
Essentially the same procedure as in example 1, except that: the step (2) is changed into normal pressure evaporation at the temperature of 120 ℃; in the step, the fluorine removal rate is 89%, and the chlorine removal rate is 80%.
COMPARATIVE EXAMPLE 3 (without addition of concentrated sulfuric acid)
Essentially the same procedure as in example 1, except that: in the step (2), concentrated sulfuric acid is not added to adjust the pH value; in the step, the fluorine removal rate is 29%, and the chlorine removal rate is 21%.
Comparative example 4 (adding hydrogen peroxide once to the surface of the acid after aeration)
Essentially the same procedure as in example 1, except that: the hydrogen peroxide is added in the step (1) in a one-time surface adding mode, and after stirring and reacting for 2 hours, the content of trivalent arsenic in the solution is 56 mg/L; the arsenic content in the condensate A in the step (2) is 38 mg/L.
Example 2
In the embodiment, sulfuric acid waste acid wastewater discharged from a sulfuric acid workshop of a Gansu copper smelting plant is taken as a treatment object, the arsenic content is 7.0g/L, the fluorine ion concentration is 3.0g/L, the chlorine ion concentration is 6.2g/L, the copper content is 200mg/L, the lead content is 60mg/L, the cadmium content is 50mg/L, the zinc content is 1407mg/L, and the pH value is 0.7.
A method for utilizing sulfuric acid waste acid wastewater resources in the copper smelting industry and obtaining arsenic-containing products comprises the following steps:
(1) and (3) an oxidation stage: taking 1L of waste acid wastewater, placing the waste acid wastewater in a waste acid storage tank for air aeration, wherein the gas-liquid content is 1.0, the air aeration time is 8h, and the dissolved oxygen in the solution after aeration is 8.7 mg/L;
the waste acid water after aeration flows into a hydrogen peroxide reaction tank, 10 wt% hydrogen peroxide is added into the bottom of the hydrogen peroxide reaction tank in two sections, the adding amount of the hydrogen peroxide in the first section is 2.5 times of that in the second section, the reaction time of each section is 1 hour, and the ratio of the total amount of hydrogen peroxide in the hydrogen peroxide introduced into the two sections to the amount of trivalent arsenic in the waste acid water is 1.2: 1;
and after the oxidation is finished, the pH value of the waste acid is 0.8, wherein the content of trivalent arsenic is 1.6 mg/L.
(2) Arsenic and fluorine-chlorine separation and concentration stage: performing negative pressure forced evaporation on the waste acid oxidized in the step (1) at the temperature of 75 ℃ under the pressure of-0.1 MPa, wherein the concentration multiple is 7.1 times, the arsenic content in the obtained condensate A is 0.006mg/L, the escape rate of the arsenic is 0.000008%, the removal rate of chlorine in the waste acid in the step is 96.1%, the removal rate of fluorine in the waste acid in the step is 99.4%, the crystallization rate of arsenic in the waste acid in the step is 76%, and the purity of the obtained arsenic pentoxide is 94.5%;
and (3) sending 40% of the obtained concentrated solution B to the waste acid storage tank in the step (1) for adjusting the pH value of the waste acid and further oxidizing and crystallizing.
(3) And (3) a condensate fluorine-chlorine separation stage: performing two-stage absorption on the condensate A by using a magnesium oxide suspension with the mass fraction of 10%, wherein the reaction time of each stage is 2 hours respectively, and obtaining a magnesium fluoride product and a dilute hydrochloric acid solution;
specifically, the method comprises the following steps: and (3) allowing the clear liquid of the condensate A after the first-stage absorption to flow into the second stage, allowing magnesium fluoride precipitate generated after the second-stage absorption to enter the first stage, and performing solid-liquid separation on the magnesium fluoride precipitate in the first stage. The pH value of the first stage reaction is 1.5, and the pH value of the second stage reaction is 3.5 (the dosage of the magnesium oxide suspension is controlled by an on-line pH meter); the second-stage clear liquid is dilute hydrochloric acid, can be used for extracting rare and precious metals after being concentrated, and the produced fresh water is used as system water for recycling (electrodialysis is adopted for concentration);
part of the second-stage clear liquid is recycled for preparing the magnesium oxide suspension;
in the step, the removal rate of the fluoride ions is 93.8 percent, and the purity of the magnesium fluoride is 99.9 percent.
(4) And (3) recovering valuable metals: respectively recovering valuable metals from the concentrated solution B left in the step (2) by adding sodium sulfide step by step, wherein the end point pH value of copper recovery is 2.1, the end point pH value of lead recovery is 2.9, the end point pH value of cadmium recovery is 3.9, and the end point pH value of zinc recovery is 5.5;
the purity of copper sulfide, lead sulfide, cadmium sulfide and zinc sulfide obtained by separating and drying the precipitates obtained in each step is 99.4%, 98.1%, 97.3% and 98.2%, and the recovery rate of valuable metals is 99.8%.
And removing all valuable metal precipitates to obtain arsenic-containing waste liquid C.
(5) And (3) a crystallization stage: adding a concentrated alkali liquor E (from the previous experiment, only the flake alkali is used for the first time, and then the recycled concentrated alkali liquor E is adopted to gradually replace the flake alkali, the same as in example 3) into the arsenic-containing waste liquid C to adjust the pH to 13.6, so as to obtain a sodium arsenate product and a crystallization filtrate D, wherein the arsenic content is 0.18mg/L, the sodium sulfate content is 287g/L, and the crystallization filtrate D is concentrated to 2.5 times of concentration, so as to obtain a sodium sulfate product and a concentrated alkali liquor E;
the concentrated lye E can be reused for the subsequent step (5) of the experiment.
The purity of the sodium arsenate product is 91 percent, and the purity of the sodium sulfate product is 96.2 percent.
Example 3
In the embodiment, sulfuric acid waste acid wastewater discharged from a sulfuric acid workshop of a copper smelting plant of Anhui province, the arsenic content of the wastewater is 9.4g/L, the fluorine ion concentration of the wastewater is 4.7g/L, the chlorine ion concentration of the wastewater is 9.1g/L, the copper content of the wastewater is 350mg/L, the lead content of the wastewater is 80mg/L, the cadmium content of the wastewater is 30mg/L, the zinc content of the wastewater is 430mg/L, and the pH value of the wastewater is 0.6.
A method for utilizing sulfuric acid waste acid wastewater resources in the copper smelting industry and obtaining arsenic-containing products comprises the following steps:
(1) in the oxidation stage, 1L of waste acid wastewater is taken and placed in a waste acid storage tank for air aeration, the gas-liquid ratio is 1.0, the air aeration time is 15 hours, and the dissolved oxygen in the solution after aeration is 9.4 mg/L;
the waste acid water after aeration flows into a hydrogen peroxide reaction tank, 8 wt% hydrogen peroxide is added into the bottom of the hydrogen peroxide reaction tank in two sections, the adding amount of the hydrogen peroxide in the first section is 3 times of that in the second section, the reaction time of each section is 1 hour, and the ratio of the total amount of hydrogen peroxide in the two sections to the amount of trivalent arsenic in the waste acid water is 1.3: 1;
and after the oxidation is finished, the pH value of the waste acid is 0.7, wherein the content of trivalent arsenic is 1.2 mg/L.
(2) Arsenic and fluorine-chlorine separation and concentration stage: and (2) carrying out negative pressure forced evaporation on the waste acid oxidized in the step (1) at-0.1 MPa and 75 ℃, wherein the concentration multiple is 7.5 times, the arsenic content in the obtained condensate A is 0.009mg/L, the arsenic escape rate is 0.00001%, the removal rate of chlorine in the waste acid in the step is 95.6%, the removal rate of fluorine in the waste acid in the step is 99.1%, the crystallization rate of arsenic in the waste acid in the step is 78%, and the purity of the obtained arsenic pentoxide is 95.7%.
And (3) sending 60% of the obtained concentrated solution B to the waste acid storage tank in the step (1) for adjusting the pH value of the waste acid and further oxidizing and crystallizing.
(3) And (3) a condensate fluorine-chlorine separation stage: performing two-stage absorption on the condensate A by using a magnesium oxide suspension with the mass fraction of 10%, wherein the reaction time of each stage is 2 hours respectively, and obtaining a magnesium fluoride product and a dilute hydrochloric acid solution;
specifically, the method comprises the following steps: and (3) allowing the clear liquid of the condensate A after the first-stage absorption to flow into the second stage, allowing magnesium fluoride precipitate generated after the second-stage absorption to enter the first stage, and performing solid-liquid separation on the magnesium fluoride precipitate in the first stage. The pH value of the first stage reaction is 2.0, and the pH value of the second stage reaction is 3.4 (the dosage of the magnesium oxide suspension is controlled by an on-line pH meter); the second-stage clear liquid is dilute hydrochloric acid, can be used for extracting rare and precious metals after concentration, and the produced fresh water is used as system water supplement for recycling (a rectification device is used for concentration);
part of the second-stage clear liquid is recycled for preparing the magnesium oxide suspension;
in the step, the removal rate of the fluorinion is 92.3 percent, and the purity of the magnesium fluoride is 99.9 percent.
(4) And (3) recovering valuable metals: respectively recovering valuable metals from the concentrated solution B left in the step (2) by adding sodium sulfide step by step, wherein the end point pH value of copper recovery is 2.5, the end point pH value of lead recovery is 3.2, the end point pH value of cadmium recovery is 4.3, and the end point pH value of zinc recovery is 5.9;
the purity of copper sulfide, lead sulfide, cadmium sulfide and zinc sulfide obtained by separating and drying the precipitates obtained in each step is 98.6%, 96.7%, 97.9% and 99.4%, respectively, and the recovery rate of valuable metals is 99.4%.
And removing all valuable metal precipitates to obtain arsenic-containing waste liquid C.
(5) And (3) a crystallization stage: adding concentrated alkali liquor E into the arsenic-containing waste liquid C to adjust the pH value to 13.8, obtaining a sodium arsenate product and a crystallization filtrate D, wherein the arsenic content is 0.09mg/L, the sodium sulfate content is 252g/L, and concentrating the crystallization filtrate D to 3.0 times of concentration to obtain a sodium sulfate product and concentrated alkali liquor E; the concentrated lye E can be reused for the subsequent step (5) of the experiment.
The purity of the sodium arsenate product is 93.7%, and the purity of the sodium sulfate product is 96.8%.
Claims (6)
1. A method for utilizing copper smelting sulfuric acid waste acid wastewater resources and obtaining arsenic-containing products, wherein the arsenic content in the waste acid wastewater is 5-10 g/L; the content of chloride ions is 0-10 g/L; the content of fluorine ions is 0-5g/L, the total content of valuable metal elements is 0.5-5g/L, and the valuable metal elements comprise copper, lead, cadmium and zinc; the method comprises the following steps in sequence:
(1) and (3) an oxidation stage: carrying out air aeration on the waste acid water, wherein the dissolved oxygen in the solution after aeration is 8.5-9.5 mg/L; adding hydrogen peroxide into the aerated waste acid water to further oxidize trivalent arsenic in the waste acid;
the ratio of the amount of the hydrogen peroxide in the added hydrogen peroxide to the amount of the trivalent arsenic in the waste acid after aeration is (1-1.3): 1;
measuring the pH value of the waste acid water after oxidation by hydrogen peroxide;
if the pH value is more than or equal to 1.0, adding sulfuric acid with the concentration of not less than 95wt% until the pH value is less than 1.0, and then entering the step (2);
if the pH value is measured to be less than 1.0, directly entering the step (2);
(2) arsenic and fluorine-chlorine separation and concentration stage: performing negative pressure forced evaporation on the waste acid and wastewater oxidized in the step (1) at 75 ℃ to obtain a concentrated solution B, an arsenic pentoxide crystal with the purity of more than or equal to 90 percent and a fluorine-chlorine-containing condensate A with the arsenic content of less than or equal to 0.01 mg/L;
40-60% of the concentrated solution B is sent to the step (1) for adjusting the acidity of the waste acid wastewater and further improving the crystallization rate of arsenic pentoxide; the rest is sent to the step (4) for valuable metal recovery;
(3) and (3) a condensate fluorine-chlorine separation stage: performing two-stage absorption on the condensate A by using the magnesium oxide suspension to obtain a magnesium fluoride product with the purity of more than or equal to 99.9 percent and a dilute hydrochloric acid solution; the clear liquid of the condensate after the first-stage absorption flows into the second stage, the magnesium fluoride precipitate generated after the second-stage absorption flows back to the first stage, and the magnesium fluoride precipitate is subjected to solid-liquid separation at the first stage; the clear liquid generated after the second-stage absorption is dilute hydrochloric acid solution;
controlling the pH value of the first-stage absorption reaction to be 1.5-2.5 and the pH value of the second-stage absorption reaction to be 3.0-3.5 by controlling the adding amount of the magnesium oxide suspension;
(4) and (3) recovering valuable metals: distributing and adding sodium sulfide into the residual concentrated solution B in the step (2) to recover more than 99% of valuable metals, and obtaining sulfide precipitates and arsenic-containing waste liquid C of the valuable metals;
firstly, adding sodium sulfide to pH =2.1-2.5 to obtain and separate and recover copper sulfide;
step two, continuously adding sodium sulfide until the pH is =2.7-3.2, and obtaining, separating and recovering lead sulfide;
thirdly, continuously adding sodium sulfide until the pH =3.5-4.5, and obtaining, separating and recovering cadmium sulfide;
step four, continuously adding sodium sulfide until the pH is =5.0-6.0, and obtaining, separating and recovering zinc sulfide;
the purity of the copper sulfide is more than or equal to 95 percent, the purity of the lead sulfide is more than or equal to 96 percent, the purity of the cadmium sulfide is more than or equal to 97 percent, and the purity of the zinc sulfide is more than or equal to 97 percent;
(5) and (3) a crystallization stage: adding flake caustic soda and/or recycled concentrated alkali liquor E into the arsenic-containing waste liquid C, adjusting the pH to 13.5-13.8, reacting to obtain a sodium arsenate product with the purity of more than or equal to 90% and a crystallization filtrate D, and concentrating the crystallization filtrate D to obtain a sodium sulfate product with the purity of more than or equal to 95% and concentrated alkali liquor E.
2. The method of claim 1, wherein: the adding mode of the hydrogen peroxide is that the hydrogen peroxide is added from the bottom of a hydrogen peroxide oxidation reaction device in two steps, the adding amount in the first step is 70-80% of the total adding amount, and the rest hydrogen peroxide is added in the second step.
3. The method according to claim 1 or 2, characterized in that: and (2) carrying out negative pressure forced evaporation on the waste acid and wastewater oxidized in the step (1) at 75 ℃ to obtain a concentrated solution B with the concentration multiple of 6.0-8.0 times.
4. The method according to claim 1 or 2, characterized in that: and (3) processing the clear liquid generated after the second stage absorption in one of the following two ways:
A. concentrating to obtain concentrated hydrochloric acid and fresh water, wherein the concentrated hydrochloric acid is used for extracting rare and precious metals, and the fresh water is used as system water supplement for recycling;
B. it is reused for preparing the magnesium oxide suspension.
5. The method according to claim 1 or 2, characterized in that: the mass percentage of the magnesium oxide in the magnesium oxide suspension is 5-15%.
6. The method according to claim 1 or 2, characterized in that: the concentration of the sodium sulfate in the crystallization filtrate D in the step (5) is 200-300 g/L.
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