CN113023987B - Treatment method of arsenic-containing wastewater - Google Patents
Treatment method of arsenic-containing wastewater Download PDFInfo
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- CN113023987B CN113023987B CN202110265572.2A CN202110265572A CN113023987B CN 113023987 B CN113023987 B CN 113023987B CN 202110265572 A CN202110265572 A CN 202110265572A CN 113023987 B CN113023987 B CN 113023987B
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Abstract
The invention provides a method for treating arsenic-containing wastewater, which comprises the following steps: adding an oxidant into the arsenic-containing wastewater, stirring for reaction, filtering after the reaction is finished, removing filter residues, and carrying out subsequent treatment on the filtrate; pouring the filtrate into a microwave reactor, starting microwaves, heating to raise the temperature, then slowly dropwise adding ferric salt to perform arsenic precipitation reaction under the condition that the pH value is 2-3, performing heat preservation aging after the reaction is finished, and then filtering to obtain low-arsenic wastewater solution and filter residue, wherein the filter residue is scorodite; adding a neutralizing agent into the low-arsenic wastewater solution to adjust the pH value, adding an iron salt to deeply remove residual arsenic in the low-arsenic wastewater, and filtering to obtain filtrate, namely the wastewater after arsenic removal. The treatment method provided by the invention has the advantages that the arsenic-containing wastewater is treated by microwave assistance, the wastewater treatment efficiency is effectively improved, the consumption of ferric salt in the subsequent deep arsenic removal process is effectively reduced, and the reduction of hazardous waste and the further reduction of cost are realized.
Description
Technical Field
The invention belongs to the technical field of wastewater treatment, and particularly relates to a treatment method of arsenic-containing wastewater.
Background
Arsenic is a main associated element in nonferrous and precious metal ores such as copper, lead, zinc, tin, antimony and the like, and can enter smoke dust and waste acid to different degrees in the extraction process of nonferrous metals. Except that a very small amount of arsenic is recovered as arsenic trioxide, the vast majority of the arsenic is removed from the waste stream and discharged to the environment as arsenic-containing solid waste.
At present, the domestic and foreign methods for treating arsenic-containing wastewater mainly comprise lime method, lime-iron salt method, sulfuration method, pyrolusite method, scorodite method, iron oxide coating sand treatment and the like. The ideal treatment method can reduce the treatment cost, reduce the output of waste residue and obtain stable waste residue on the premise of ensuring that the arsenic treatment reaches the standard so as to prevent the secondary pollution of arsenic. Scorodite has the advantages of high arsenic content (up to 32%), low iron demand, low leaching toxicity, high stability, small volume, low storage cost and the like, and is an arsenic-containing carrier suitable for stockpiling treatment; at present, the conventional scorodite preparation method comprises an atmospheric pressure method, a hydrothermal method and an improved atmospheric pressure method, but the conventional scorodite preparation method has the treatment time of 8-12 hours, the production efficiency is low, the residual arsenic content in the treated wastewater reaches 300-500mL/L, and because iron salt with high iron-arsenic ratio needs to be added during the subsequent deep arsenic removal, the high residual arsenic content increases the arsenic-containing hazardous waste content of the conventional scorodite preparation method.
Disclosure of Invention
The invention belongs to arsenic removal by a scorodite method, and aims to solve the technical problems of overcoming the defects and shortcomings in the background art and providing a method for treating arsenic-containing wastewater.
In order to solve the technical problems, the technical scheme provided by the invention is as follows:
a method for treating arsenic-containing wastewater comprises the following steps:
(1) Adding an oxidant into the arsenic-containing wastewater, stirring for reaction, filtering after the reaction is finished, removing filter residues, and carrying out subsequent treatment on the filtrate;
(2) Pouring the filtrate obtained in the step (1) into a microwave reactor, starting microwaves, heating to raise the temperature, then slowly dropwise adding ferric salt to perform arsenic precipitation reaction under the condition that the pH value is 2-3, controlling the supersaturation degree, performing heat preservation aging after the reaction is finished, and then filtering to obtain a low-arsenic wastewater solution and filter residues, wherein the filter residues are scorodite;
(3) And (3) adding a neutralizing agent into the low-arsenic wastewater solution obtained in the step (2) to adjust the pH value, adding ferric salt to deeply remove residual arsenic in the low-arsenic wastewater, and filtering to obtain filtrate, namely the wastewater after arsenic removal.
In the above treatment method, preferably, the frequency of the microwave is 300MHz-300KMHz. The microwave is to directly convert electromagnetic energy into heat energy by utilizing the dielectric loss of microscopic molecules or atoms of the wave-absorbing material in a microwave field, and the heating speed is high and uniform. Under the action of microwaves, arsenate ions and ferric ions move at high speed, so that the collision probability of the arsenate ions and the ferric ions is increased, the growth speed of the scorodite crystal is increased, and the supersaturation degree is reduced. The frequency of the microwave is controlled within the range of the invention, so that the crystallization time can be effectively shortened, and scorodite crystals with good crystallinity can be obtained.
In the above treatment method, preferably, the trivalent arsenic in the wastewater is oxidized into pentavalent arsenic by adding an oxidant, and in order to avoid introducing new impurity ions into the system, the oxidant is air and/or hydrogen peroxide. More preferably, in order to ensure the oxidation effect, in the acidic wastewater, a hydrogen peroxide solution with the mass fraction of 1.2-4.0% is selected as an oxidant; in alkaline wastewater, air is selected as an oxidant.
In the above treatment method, preferably, the iron salt is ferric sulfate and/or ferrous sulfate.
In the above treatment method, in the step (2), the molar ratio of the iron element in the iron salt to the arsenic element in the filtrate is (1 to 1.5): 1; in the step (3), the molar ratio of the iron element in the ferric salt to the arsenic element in the low-arsenic wastewater is (8-12): 1.
In the above treatment method, preferably, in the step (2), the temperature is raised to 65-95 ℃, and the arsenic precipitation reaction time is 15min-1h.
In the above treatment method, preferably, in the step (2), the temperature for heat preservation and aging is 85-100 ℃ for 1-4h. The parameters of heat preservation and aging are controlled within the range of the invention, so that ferric arsenate can be gradually gathered from nano-sized particles to form scorodite crystals with larger particles, the stability of the scorodite crystals is improved, and the leaching toxicity is reduced.
In the above treatment method, preferably, in the step (3), the neutralizing agent is sodium hydroxide and/or lime milk, and the neutralizing agent is added to adjust the pH value to 8-10.
In the above treatment method, preferably, in the step (1), the arsenic content of the arsenic-containing wastewater is 0.3 to 20g/l.
In the above treatment method, preferably, in the step (3), the residual arsenic content in the treated wastewater is 60mg/L or less.
Compared with the prior art, the invention has the advantages that:
according to the treatment method, the arsenic-containing wastewater is treated by microwave assistance, so that the wastewater treatment efficiency is effectively improved, the reaction time for preparing scorodite is greatly reduced to 1-4 hours, and the arsenic removal efficiency is improved by at least one time compared with the reaction time (usually 8-12 hours) of the conventional scorodite preparation methods such as an atmospheric pressure method, a hydrothermal method and an improved atmospheric pressure method; meanwhile, the residual amount of arsenic in the wastewater after scorodite is prepared by microwave induction is less than 60mL/L, while the residual amount of arsenic in the wastewater after scorodite is prepared by the improved normal pressure method is generally 300-500mL/L, so that the consumption of ferric salt in the subsequent deep arsenic removal process is effectively reduced, and the reduction of dangerous waste amount and the further reduction of cost are realized.
The treatment method has the advantages of simple process flow, low process cost, high treatment efficiency, low arsenic-containing slag content and high stability, and is suitable for large-scale application.
Drawings
In order to more clearly illustrate the embodiments or technical solutions of the present invention, the drawings used in the embodiments or technical solutions in the prior art are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a schematic view of the process flow of the method for treating arsenic-containing wastewater of example 1 of the present invention.
Detailed Description
In order to facilitate an understanding of the invention, the invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of the invention is not limited to the specific embodiments below.
Unless otherwise defined, all terms of art used hereinafter have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present invention.
Unless otherwise specifically indicated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.
Example 1:
the technical process schematic diagram of the treatment method of arsenic-containing wastewater of the invention is shown in figure 1, the treated arsenic-containing wastewater is mixed wastewater of arsenic alkaline residue leachate of certain antimony smelting plant and acidic sewage (arsenic content is 8.9 g/L), and the treatment method specifically comprises the following steps:
(1) Adding 2mL of hydrogen peroxide into 220mL of arsenic-containing wastewater, stirring and reacting for 60min, filtering after the reaction is finished, removing filter residues, and performing subsequent treatment on the filtrate;
(2) Adding the filtrate obtained in the step (1) into a microwave reactor, starting microwave with the frequency of 2450MHz, heating to 85 ℃, and stirring at the speed of 200r/min according to the molar ratio of iron to arsenic of 1.25: slowly dripping 30mL of ferric sulfate solution at the dripping speed of 0.5mL/min, carrying out arsenic precipitation reaction under the conditions of pH value of 2-3 and stirring, wherein the arsenic precipitation reaction time is 50 minutes, carrying out heat preservation and aging at 95 ℃ for 4 hours after the reaction is finished, and filtering to obtain low-arsenic wastewater solution and filter residue, wherein the filter residue is scorodite;
(3) Adding a neutralizing agent lime milk into the low-arsenic wastewater solution obtained in the step (2) to adjust the pH value to 10, then adding ferrous sulfate to carry out aeration reaction to deeply remove residual arsenic in the low-arsenic wastewater, wherein the molar ratio of iron in iron salt to arsenic in the low-arsenic wastewater is 10.
The arsenic content in the treated wastewater solution is 0.1mg/L through detection; the arsenic slag (scorodite) is subjected to leaching toxicity test, and the result shows that the leaching toxicity concentration of the arsenic is 0.55mg/L, which is far lower than the control limit value of 1.2mg/L in hazardous waste landfill pollution control Standard (GB 18598-2019).
Example 2:
the invention relates to a method for treating arsenic-containing wastewater, which is acidic wastewater (the main chemical components of which are shown in Table 1) of a certain lead-zinc smelting plant, and specifically comprises the following steps:
TABLE 1 main constituent elements and contents of As-containing wastewater in example 2
| Element(s) | As | Cd | Pb | Cu | Zn |
| Content (wt.) | 2.17g/L | 145mg/L | 18 mg/L | 0.16mg/L | 0.56mg/L |
(1) Adding 1mL of hydrogen peroxide into 100mL of arsenic-containing wastewater, stirring and reacting for 60min, filtering after the reaction is finished, removing filter residues, and performing subsequent treatment on the filtrate;
(2) Adding the filtrate obtained in the step (1) into a microwave reactor, starting microwave with the microwave power of 2450MHz, heating to 85 ℃, and stirring at the stirring speed of 200r/min according to the molar ratio of iron to arsenic of 1.2: slowly dripping 30mL of ferric sulfate solution at the dripping speed of 1mL/min, carrying out arsenic precipitation reaction under the conditions of pH value of 2-3 and stirring, wherein the arsenic precipitation reaction time is 30 minutes, carrying out heat preservation and aging at 95 ℃ for 3 hours after the reaction is finished, and then filtering to obtain low-arsenic wastewater solution and filter residue, wherein the filter residue is scorodite;
(3) Adding a neutralizing agent sodium hydroxide into the low-arsenic wastewater solution obtained in the step (2) to adjust the pH value to 10, adding ferric sulfate to deeply remove residual arsenic in the low-arsenic wastewater, wherein the molar ratio of iron in ferric salt to arsenic in the low-arsenic wastewater is 8.
The arsenic content in the treated wastewater solution is 0.22mg/L through detection; the arsenic slag (scorodite) is subjected to leaching toxicity test, and the result shows that the leaching toxicity concentration of the arsenic is 0.65mg/L, which is far lower than the control limit of 1.2mg/L in hazardous waste landfill pollution control Standard (GB 18598-2019).
Claims (7)
1. The method for treating the arsenic-containing wastewater is characterized by comprising the following steps of:
(1) Adding an oxidant into the arsenic-containing wastewater, stirring for reaction, filtering after the reaction is finished, removing filter residues, and carrying out subsequent treatment on the filtrate;
(2) Pouring the filtrate obtained in the step (1) into a microwave reactor, starting microwaves, heating, raising the temperature, then slowly dropwise adding ferric salt to perform arsenic precipitation reaction under the condition that the pH value is 2-3, performing heat preservation aging after the reaction is finished, and then filtering to obtain low-arsenic wastewater solution and filter residue, wherein the filter residue is scorodite;
(3) Adding a neutralizing agent into the low-arsenic wastewater solution obtained in the step (2) to adjust the pH value, adding an iron salt to deeply remove residual arsenic in the low-arsenic wastewater, and filtering to obtain filtrate, namely the wastewater after arsenic removal;
the frequency of the microwave is 300MHz-300KMHz;
the ferric salt is ferric sulfate and/or ferrous sulfate;
in the step (2), the temperature is increased to 65-95 ℃, and the time of arsenic precipitation reaction is 15min-1h.
2. The process of claim 1, wherein the oxidizing agent is air and/or hydrogen peroxide.
3. The treatment method according to claim 1, wherein in the step (2), the molar ratio of the iron element in the iron salt to the arsenic element in the filtrate is (1 to 1.5): 1; in the step (3), the molar ratio of the iron element in the ferric salt to the arsenic element in the low-arsenic wastewater is (8-12): 1.
4. The treatment method according to claim 1, wherein in the step (2), the temperature for heat preservation and aging is 85-100 ℃ and the time is 1-4h.
5. The process according to claim 1, wherein in the step (3), the neutralizing agent is sodium hydroxide and/or lime milk, and the neutralizing agent is added to adjust the pH value to 8-10.
6. The treatment method according to claim 1, wherein in the step (1), the arsenic-containing wastewater has an arsenic content of 0.3 to 20g/l.
7. The treatment method according to claim 1, wherein the arsenic residue content in the treated wastewater in the step (3) is 60mg/L or less.
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