CN113414220B

CN113414220B - Harmless treatment method for arsenic-containing slag

Info

Publication number: CN113414220B
Application number: CN202110697138.1A
Authority: CN
Inventors: 段铭诚; 张洪; 樊新淼
Original assignee: Honghe Arsenic Co ltd
Current assignee: Honghe Arsenic Co ltd
Priority date: 2021-06-23
Filing date: 2021-06-23
Publication date: 2023-04-07
Anticipated expiration: 2041-06-23
Also published as: CN113414220A

Abstract

A harmless treatment method of arsenic-containing slag comprises the steps of heating the arsenic-containing slag to 80-100 ℃, and preserving heat for 2-4 hours to obtain dry arsenic-containing slag; roasting the dried salt-containing arsenic slag to volatilize organic matters in the salt-containing arsenic slag into ash to obtain roasted slag; and adding an arsenic fixing agent and a cementing material into the roasting slag for solidification, curing the solidified body, then carrying out a toxicity leaching test, and sending the solidified body into a landfill for landfill after the leaching toxicity meets the national standard, namely completing the harmless treatment of the salt-containing arsenic slag. According to the invention, through the combination of roasting-cement curing processes, arsenic forms a stable cured body, the leached toxic arsenic content is less than 1.2mg/L, and the harmless treatment of the salt-containing arsenic slag is realized.

Description

Harmless treatment method for arsenic-containing slag

Technical Field

The invention belongs to the technical field of harmful substance treatment methods, and particularly relates to a harmless treatment method of arsenic slag containing salt.

Background

Arsenic is commonly present in metal ore bodies, and during ore body smelting and arsenic-containing wastewater treatment, arsenic is often present in smoke dust and waste residues in the form of arsenic trioxide or arsenate and the like. The smoke dust and the arsenic chemical waste residue with lower arsenic content must be subjected to harmless treatment. With the increasing environmental protection requirements of the country on the production and operation processes of enterprises, the arsenic-containing slag can bring harm to the environment if not properly disposed, and meanwhile, the method also brings great environmental protection pressure to the safety production of the enterprises. Along with the development of arsenic products and the effective opening of arsenic-containing materials, the harmless treatment of arsenic-containing waste residues becomes an important research direction for the treatment of the arsenic-containing waste residues.

At present, the disposal modes of arsenic-containing waste residues at home and abroad are two types, namely resource utilization and landfill after solidification pretreatment.

1. Resource utilization

When the arsenic-containing waste residue contains more than 20 percent of arsenic and other valuable metals, the arsenic-containing waste residue is treated by a resource utilization process. The method mainly comprises the following two treatment processes:

(1) Firing: and carrying out pyrogenic processes such as oxidizing roasting, reducing roasting, vacuum roasting and the like to recycle arsenic in the slag in the form of arsenic trioxide, or carrying out reduction refining on a crude product of arsenic trioxide to prepare simple substance arsenic with higher purity.

(2) Wet leaching: wet processing such as acid leaching, alkali leaching or salt leaching is used for separating arsenic from waste residue, and then arsenic or arsenic trioxide is obtained by further processing, thus achieving the purpose of comprehensive utilization of arsenic-containing residue.

The technological routes of the pyrogenic process and the wet process have respective advantages and disadvantages, the production flow of the pyrogenic process roasting process is short, the equipment requirement is not high, the material handling capacity is large, but the volatile smoke dust is easy to cause secondary pollution to the environment, the raw materials have a certain limit range, and the method has better economic benefit when being used for treating arsenic slag with the arsenic content of more than 20 percent. The wet leaching does not generate dust, can meet the requirement of environmental protection, and has the advantages of low energy consumption, little pollution, high efficiency and the like, but the wet process has the defects of complex flow, high subsequent wastewater treatment cost and the like.

2. Landfill after harmless pretreatment

When the arsenic content in the arsenic-containing waste residue is less than 20 percent, and other valuable metals have low content and no resource utilization value, the arsenic-containing waste residue is generally sent to a landfill site for landfill after solidification pretreatment. The solidification treatment is a harmless treatment method for fixing or containing harmful solid waste in an inert solid matrix by a physical/chemical method to ensure that the harmful solid waste is chemically stable or sealed. The curing treatment technology can be divided into glue coating curing, self-cementing curing and melting curing according to different curing agents. The curing of encapsulation can be further divided into cement curing, lime curing, plastic curing, organic polymer curing and ceramic curing according to the different encapsulating materials.

Because the arsenic-containing slag contains salt and organic matters, when the arsenic-containing slag is cured by cement, the salt and the organic matters in the slag destroy the arsenic solidification effect of cement glue, a large amount of salt is separated out from the surface of a cured body after curing, so that the strength of the cured body is insufficient, the arsenic solidification effect is poor, the arsenic leaching content is greater than the requirement that the arsenic content in a toxic leaching solution specified by national standards is less than 1.2mg/L, and the aim of harmless treatment cannot be achieved.

When the roasting treatment is adopted to treat the salt-containing arsenic slag, if the roasting temperature is low, the volatilization rate of arsenic in the salt-containing arsenic slag is low, and the arsenic content leached from the roasting slag is greater than the requirement that the arsenic content in a toxic leaching solution specified by the national standard is less than 1.2 mg/L. The roasting temperature is increased, the volatilization rate of arsenic is increased, but salt in arsenic slag is melted and agglomerated, the continuous volatilization of arsenic in the slag is hindered, the arsenic content in the roasted slag is higher than the requirement that the arsenic content in a toxic leachate specified by national standard is less than 1.2mg/L, and the purpose of harmless treatment cannot be achieved.

Disclosure of Invention

The invention aims to solve the problems in the prior art and provides a harmless treatment method of salt-containing arsenic slag, so as to effectively solve the problem of arsenic pollution caused by the salt-containing arsenic slag generated in the preparation process of arsenic chemical products.

The purpose of the invention is realized by the following technical scheme:

a harmless treatment method of arsenic slag containing salt comprises the following steps:

(1) Heating the salt-containing arsenic slag to 80-100 ℃, and preserving the heat for 2-4 hours to obtain dry salt-containing arsenic slag;

(2) Roasting the dried salt-containing arsenic slag obtained in the step (1) to volatilize organic matters in the salt-containing arsenic slag into ash to obtain roasted slag;

(3) And (3) adding an arsenic fixing agent and a cementing material into the roasting slag obtained in the step (2) for curing, curing the cured body, performing a toxicity leaching test, and sending the cured body into a landfill after the leaching toxicity meets the national standard for landfill to complete harmless treatment.

Further, the national standard of the invention is the hazardous waste landfill pollution control standard (GB 18598-2019).

Further, the arsenic-containing slag containing salt is generated after arsenic-containing wastewater generated in the preparation process of the arsenic chemical product is concentrated or chemically precipitated, wherein the salt exists in the form of taking sodium sulfate and sodium chloride as main components, the arsenic exists in the form of taking sodium arsenate and sodium arsenite as main components, and the organic matter exists in the form of taking benzyl chloride and benzyl alcohol as main components; the arsenic slag containing salt has 30-40 wt.% of salt, 2-10 wt.% of arsenic, 5-8 wt.% of organic matter and 15-40% of water content.

Further, the water content of the dried waste arsenic slag obtained in the step (1) is less than 3%.

Further, when the dried salt-containing arsenic slag is roasted in the step (2), the roasting temperature is 450-550 ℃, the roasting time is 3-5 hours, and the content of organic matters in the roasted slag is less than 1wt.%.

Further, the arsenic fixing agent in the step (3) is polymeric ferric sulfate, the cementing material is cement and lime, and the weight percentage of the calcined slag is as follows: cement: polymeric ferric sulfate: lime: the weight ratio of water is 6:1-2:1-2: 1, and uniformly mixing to obtain a solidified body.

Further, the solidified body is sent to a landfill site after natural curing for 14 days.

According to the invention, by combining roasting-cement curing processes, arsenic forms a stable solidified body, the leached toxic arsenic content is lower than 1.2mg/L, and the harmless treatment of the salt-containing arsenic slag is realized. Compared with the prior art that the method for treating the arsenic-containing slag by singly adopting cement solidification, the method eliminates the adverse effect of salt and organic matters on the arsenic solidification effect when the arsenic-containing slag is solidified, avoids the problem that the volatilization effect of arsenic is influenced by the melting and caking of salt in the slag during roasting, and effectively solves the problem of arsenic pollution caused by the arsenic-containing slag containing salt and organic matters generated in the arsenic chemical production process.

Detailed Description

The present invention will be described in detail with reference to examples, but the specific examples described herein are only for the purpose of illustrating the present invention and are not intended to limit the present invention.

The harmless treatment method of the arsenic-containing slag comprises the following steps:

(1) And heating the salt-containing arsenic slag to 80-100 ℃, and preserving the heat for 2-4 hours to obtain the dry salt-containing arsenic slag with the water content of less than 3%. The salt-containing arsenic slag is generated after arsenic-containing wastewater generated in the preparation process of arsenic chemical products is concentrated or chemically precipitated, wherein salt mainly exists in the forms of sodium sulfate and sodium chloride, arsenic mainly exists in the forms of sodium arsenate and sodium arsenite, and organic matters mainly exist in the forms of benzyl chloride and benzyl alcohol. The arsenic slag containing salt has 30-40 wt% of salt, 2-10 wt% of arsenic, 5-8 wt% of organic matter and 15-40% of water content.

(2) And (2) roasting the dried salt-containing arsenic slag obtained in the step (1), wherein the roasting temperature is 450-550 ℃, and the roasting time is 3-5 hours, so that organic matters in the salt-containing arsenic slag are volatilized into ash, and the roasted slag with the organic matter content of less than 1wt.% is obtained, thereby being beneficial to subsequent curing treatment and reducing the interference of the organic matters.

(3) And (3) adding an arsenic fixing agent and a cementing material into the roasting slag obtained in the step (2) for solidification, maintaining the solidified body for about 14 days, and then performing a toxicity leaching test, wherein the leached toxicity meets the requirement that the arsenic content is less than 1.2mg/L specified in the national standard hazardous waste landfill pollution control standard (GB 18598-2019), and then the leached toxicity can be sent into a landfill for landfill, so that the aim of harmless treatment of the arsenic-containing slag is fulfilled. The toxicity leaching test method is a prior art method. The solid arsenic agent usually adopts polymeric ferric sulfate which plays a role in flocculating and solidifying arsenic, and compared with other solid arsenic agents, the polymeric ferric sulfate has the advantages of high activity, good arsenic-fixing effect, high flocculation speed and the like. The cement and lime curing agent has the advantages of good curing effect, full concrete aging, enhanced strength of the cured body and the like compared with the single cement curing agent. The process operation is carried out according to the following steps: cement: polymeric ferric sulfate: lime: the weight ratio of water is 6:1-2:1-2: 1, and uniformly mixing to obtain a solidified body.

Example 1

And (3) putting 1000g of arsenic slag containing 30.33% of salt, 9.82% of arsenic, 6.01% of organic matters and 22% of water content into a constant-temperature drying oven for drying at the drying temperature of 80 ℃ for 4 hours to obtain 770g of dried slag with the water content of less than 3%. And transferring the dried slag to a muffle furnace for roasting at the roasting temperature of 450 ℃ for 5 hours to obtain 726.2g of roasted slag. And adding 121g of cement, 121g of polymeric ferric sulfate, 60g of lime and 121mL of water into the roasting slag, stirring and curing to obtain a cured body, and naturally curing the cured body for 14 days to perform a toxicity leaching test. The leaching results are shown in table 1.

TABLE 1 cured body toxicity leaching test results

Numbering	As(mg/L)
		Standard (GB 18598-2019)	＜1.2
Before being innoxious	376
		After being innoxious	0.738

Example 2

And (2) putting 1000g of arsenic slag containing 36.2% of salt, 2.08% of arsenic, 7.92% of organic matters and 15% of water content into a constant-temperature drying oven for drying at 90 ℃ for 2 hours to obtain 740g of dried slag with the water content lower than 3%. And transferring the dried slag to a muffle furnace for roasting at 500 ℃ for 4 hours to obtain 693g of roasted slag. 173g of cement, 173g of polymeric ferric sulfate, 81g of lime and 116mL of water are added into the roasting slag, the mixture is stirred and solidified to obtain a solidified body, and the solidified body is naturally cured for 14 days and then a toxicity leaching test is carried out. The leaching results are shown in table 2.

TABLE 2 toxic Leaching test results of cured bodies

Example 3

And (2) putting 1000g of arsenic slag containing 39.8% of salt, 8.1% of arsenic, 5.2% of organic matters and 40% of water content into a constant-temperature drying oven for drying at 100 ℃ for 3 hours to obtain 600g of dried slag with water content less than 3%. And transferring the dried slag to a muffle furnace for roasting at the roasting temperature of 550 ℃ for 3 hours to obtain 557g of roasted slag. 186g of ordinary cement, 186g of polymeric ferric sulfate, 93g of lime and 93mL of water are added into the roasting slag, the mixture is stirred and solidified to obtain a solidified body, and the solidified body is naturally cured for 14 days and then subjected to a toxicity leaching test. The leaching results are shown in table 3.

TABLE 3 toxic Leaching test results of the cured bodies

Numbering	As(mg/L)
		Standard (GB 18598-2019)	＜1.2
Before being innoxious	680
		After being innoxious	0.542

All percentages stated in the present invention are percentages by mass, unless otherwise stated.

Claims

1. A harmless treatment method of arsenic slag containing salt is characterized by comprising the following steps:

(1) Heating the salt-containing arsenic slag to 80-100 ℃, and preserving the heat for 2-4 hours to obtain dry salt-containing arsenic slag; the salt-containing arsenic slag is produced by concentrating or chemically precipitating arsenic-containing wastewater produced in the preparation process of an arsenic chemical product, wherein salt exists in the form of taking sodium sulfate and sodium chloride as main components, arsenic exists in the form of taking sodium arsenate and sodium arsenite as main components, and organic matters exist in the form of taking benzyl chloride and benzyl alcohol as main components; 30-40 wt% of salt, 2-10 wt% of arsenic, 5-8 wt% of organic matters and 15-40% of water content in the arsenic slag containing salt;

(2) Roasting the dried salt-containing arsenic slag obtained in the step (1) to volatilize organic matters in the salt-containing arsenic slag into ash, thereby obtaining roasted slag;

(3) And (3) adding an arsenic fixing agent and a cementing material into the roasting slag obtained in the step (2) for solidification, maintaining the solidified body, then carrying out a toxicity leaching test, and sending the solidified body into a landfill for landfill after the leaching toxicity meets the national standard, thereby realizing harmless treatment.

2. The harmless treatment method of arsenic slag containing salt according to claim 1, wherein the national standard is "hazardous waste landfill pollution control Standard" (GB 18598-2019).

3. The method for harmless treatment of arsenic slag containing salt as claimed in claim 1 or 2, wherein the moisture content of the dried waste arsenic slag obtained in step (1) is less than 3%.

4. The method for harmless treatment of arsenic slag containing salt as claimed in claim 1 or 2, wherein in the step (2), when the dried arsenic slag containing salt is roasted, the roasting temperature is 450-550 ℃, the roasting time is 3-5 hours, and the content of organic matters in the roasted slag is less than 1wt.%.

5. The method for harmlessly treating the arsenic-containing slag according to claim 1 or 2, wherein in the step (3), the arsenic fixing agent is polymeric ferric sulfate, the cementing materials are cement and lime, and the ratio of the solid arsenic to the solid arsenic in the roasting slag is as follows: cement: polymeric ferric sulfate: lime: the water is 6:1-2:1-2: 1, and uniformly mixing to obtain a solidified body.

6. The method of claim 5, wherein the solidified body is naturally cured for 14 days and then sent to a landfill.