Solidification treatment method for reducing arsenic leaching amount in arsenic-containing neutralization slag

Abstract

The invention relates to the technical field of neutralization slag solidification treatment, in particular to a solidification treatment method for reducing the arsenic leaching amount in arsenic-containing neutralization slag, which comprises the following steps: step 1, carrying out humidity pretreatment on the arsenic-containing neutralization slag to obtain wet-based neutralization slag; 2, calcium hydroxide is added into the wet base neutralization residues, and a mixture I is obtained; 3, ferrous sulfate is added into the mixture I, and a mixture II is obtained; step 4, adding a chelating agent into the mixture II to obtain a mixture III; and 5, adding cement into the mixture III, and curing to obtain an arsenic-containing neutralization slag cured product. According to the method, the arsenic leaching rate is reduced, and the lowest value of the arsenic leaching amount is 0.2307 mg / kg and is far lower than the highest limit value in the national standard; the curing treatment cost is low.

Description

Technical Field

[0001] The present application relates to the technical field of neutralization slag solidification treatment, and in particular to a solidification treatment method for reducing the amount of arsenic leaching in arsenic-containing neutralization slag. Background Art

[0002] Arsenic is mainly associated with gold, copper, lead, tin, zinc, nickel, cobalt and other minerals in the form of sulfides in nature. The sources of arsenic-containing neutralized slag mainly include: tailings left over from ore mining, arsenic-containing soot, arsenic-containing alkaline slag and other waste residues produced during metal smelting, and sludge obtained after treatment of arsenic-containing wastewater and waste acid. The forms of arsenic in arsenic-containing waste residues from different sources are not exactly the same. For example, arsenic is mostly volatilized in the form of oxides in the process of metal smelting and exists in arsenic-containing smoke dust, and exists in the form of sulfides or arsenates in the sludge obtained after precipitation treatment of arsenic-containing wastewater and waste acid.

[0003] At present, there are two main methods for treating arsenic-containing waste residues: one is to use stabilization / solidification to treat arsenic-containing waste residues, that is, to wrap arsenic with inert materials to prevent arsenic leakage or convert arsenic into chemically stable arsenate for storage; the other is to recycle arsenic-containing waste residues and recycle arsenic and other valuable metals contained in the waste residues to achieve the dual purpose of harmless treatment and resource utilization of arsenic-containing waste residues. When using the stabilization / solidification method, there is a high arsenic leaching rate, and the added reagents are subject to control, which increases the treatment cost. Summary of the invention

[0004] The object of the present invention is to provide a solidification treatment method for reducing the arsenic leaching amount in arsenic-containing neutralized slag. After pre-treatment of the arsenic-containing neutralized slag, calcium hydroxide, ferrous sulfate, thiourea and cement are added in sequence to obtain a mixture, thereby reducing the arsenic leaching rate and solving the problems existing in the prior art.

[0005] In order to solve the above technical problems, the present invention adopts the following solutions: A solidification treatment method for reducing the amount of arsenic leaching from arsenic-containing neutralized slag comprises the following steps: Step 1: pre-treating the humidity of the arsenic-containing neutralized slag to obtain wet-based neutralized slag; Step 2: adding calcium hydroxide to the wet base and slag to obtain a mixture I; Step 3: adding ferrous sulfate to mixture I to obtain mixture II; Step 4: adding a chelating agent to mixed material II to obtain mixed material III; Step 5: Add cement to mixture III, and obtain arsenic-containing neutralized slag solidified material after solidification.

[0006] In the present application, the arsenic-containing neutralized slag is first pretreated so that the humidity of the obtained wet-based neutralized slag is within a certain range, on the one hand to ensure the effect of the chemical reactions in steps two to four; on the other hand to ensure the morphology of the solidified body of the arsenic-containing neutralized slag. A high moisture content will result in a long curing time in the later stage, and a low moisture content will result in a poor curing effect.

[0007] Calcium hydroxide, ferrous sulfate and chelating agent are added to the wet neutralized slag in sequence, so that the arsenate in the wet neutralized slag reacts to form calcium arsenate or calcium arsenite; then the arsenate reacts with ferrous sulfate through electrostatic attraction to form an outer layer complex, that is, a coprecipitated compound formed by adsorption; at the same time, free arsenic directly reacts with free iron ions through ligand exchange to form an inner layer complex, thereby generating sparingly soluble iron-arsenic compounds. The chelating agent is thiourea, which makes the sparingly soluble iron-arsenic compounds form a relatively stable metal complex, which reacts with cement. The cement is mainly used as a gelling agent. After gelling the relatively stable metal complex, the obtained mixture is solidified to form an arsenic-containing neutralized slag solidified material, thereby improving the solidification effect, that is, improving the hardness of the solidified material; at the same time, flexible landfill treatment is carried out to make the arsenic leaching amount of the arsenic-containing neutralized slag that has completed the solidification treatment within the range of 0.2307~1.5738mg / kg, and the minimum arsenic leaching amount is 0.2307mg / kg, which greatly reduces the arsenic leaching amount in the arsenic-containing neutralized slag after solidification treatment.

[0008] Preferably, in the step 1, the humidity of the wet-based neutralized slag is 30% to 60%.

[0009] Preferably, the humidity pretreatment is carried out by adding water or drying.

[0010] Before humidity pretreatment, the arsenic-containing neutralization slag can be crushed to ensure that the particle size of all neutralization slag is less than 1 mm, which is convenient for subsequent humidity pretreatment.

[0011] Preferably, in step 2, the pH of the mixture I is adjusted to 10-12; The weight ratio of the wet-based neutralized slag to calcium hydroxide is 100:3-5.

[0012] Among them, calcium hydroxide can also form a bridging effect during the reaction here, which is helpful for the complexation and flocculation of metal ions; at the same time, calcium hydroxide plays a role in adjusting the pH range of the mixture I, and increasing the subsequent complexation reaction rate of the wet-based neutralization slag with ferrous sulfate and thiourea.

[0013] Preferably, in step 3, the pH of mixture II is adjusted to 10-11; The weight ratio of the wet-based neutralized slag to ferrous sulfate is 15-20:1.

[0014] Preferably, in the step 4, the weight ratio of the wet-based neutralization residue to the chelating agent is 100:0.5-0.8.

[0015] Preferably, the chelating agent is thiourea.

[0016] Among them, compounds with sulfur-carbon double bonds and carbon-nitrogen double bonds in thiourea can play a stabilizing role. In thiourea molecules, multiple atoms have parallel P orbitals that overlap and form a whole. P electrons move between multiple atoms to form a large π bond. As the electron activity area increases, a delocalization effect occurs, which reduces the energy of the system, increases its stability, and makes the bond length uniform, thereby changing the configuration and properties of the molecule, weakening the sulfur-carbon double bond component and strengthening the carbon-nitrogen double bond component. Due to the formation of a large π bond and the donation of a pair of electrons on the sulfur atom to arsenic and mercury ions, a relatively stable metal complex can be formed.

[0017] Preferably, the mixing reaction time of the wet-based neutralized residue and thiourea is 15 min to 20 min.

[0018] Preferably, the weight ratio of the wet-based neutralized slag to cement is 10:1-4.

[0019] Preferably, the cement is of C325 type. The cement herein is a powdery material containing calcium carbonate, quartz, aluminate, metaaluminate, alumina and silicate.

[0020] After the cement is added, a certain amount of water is added to the mixture formed by the cement and the mixture III, so as to ensure that the moisture content of the mixture reaches 60%~70% before solidification, thereby achieving a good solidification effect.

[0021] The beneficial effects of the present invention are as follows: the present invention is a solidification treatment method for reducing the arsenic leaching amount in arsenic-containing neutralized slag, and calcium hydroxide, ferrous sulfate, thiourea and cement are added in sequence after pretreatment of the arsenic-containing neutralized slag to obtain a mixture, thereby reducing the arsenic leaching rate. The minimum arsenic leaching amount is 0.2307 mg / kg, which is far lower than the maximum limit value in the national standard.

[0022] The arsenic-containing neutralized slag solidified material after solidification treatment can meet the requirements of flexible landfill disposal, without the need to select rigid landfill, thus reducing the processing cost and avoiding the cost and risk of secondary excavation disposal.

[0023] The calcium hydroxide, ferrous sulfate and thiourea used in the present invention do not belong to controlled agents, thereby reducing the actual management difficulty and the cost of purchasing agents. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The present invention is a process flow chart of a solidification treatment method for reducing the amount of arsenic leaching in arsenic-containing neutralization slag. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings of the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] Example 1 Raw materials of this embodiment: arsenic-containing neutralized slag, calcium hydroxide, ferrous sulfate, thiourea, cement; Arsenic-containing neutralized slag: arsenic content is between 0.5% and 3%; pH value is between 7.77 and 10.25; moisture content: 16.25% to 31.59%; soluble salt content: 6.03% to 8.92%; arsenic leaching: 10.45 mg / kg (total content 7047 to 26429 mg / kg); mercury leaching: 0.0044 mg / kg (total content 104.2307 mg / kg).

[0027] Reference Figure 1 , each raw material is carried out according to the following steps: (1) Add water or dry the arsenic-containing neutralization slag to obtain wet-based neutralization slag, so that the humidity of the wet-based neutralization slag is 30% to 60%; (2) adding calcium hydroxide to the wet-base neutralized slag, stirring to obtain a mixture I, and adjusting the pH of the mixture I to 10-12; The weight ratio of the wet-based neutralized slag to calcium hydroxide is 100:3-3.5; (3) Add ferrous sulfate to mixture I, stir and react to obtain mixture II, and adjust the pH of mixture II to 10-11; The weight ratio of the wet-based neutralized slag to ferrous sulfate is 19-20:1; (4) adding thiourea to the mixture II, mixing and reacting to obtain the mixture III, wherein the weight ratio of the wet-based neutralized residue to thiourea is 100:0.5-0.8; and the mixing reaction time is 15 min-20 min; (5) adding cement to the mixture III, stirring evenly to obtain a total mixture, and subjecting the mixture to natural curing to complete the solidification treatment of the arsenic-containing neutralized slag; The weight ratio of wet-base neutralized slag to cement is 10:1~2.5, and the cement used is C325 model.

[0028] (6) The total mixture after curing is tested for pH value, leached arsenic, leached mercury, and soluble salts.

[0029] Table 1 Performance data of arsenic-containing neutralized slag after solidification treatment with different weight ratios of thiourea and cement According to Table 1, the weight ratio of the wet-based neutralization slag to thiourea is 100:0.5~0.8, and thiourea is added in a variable amount within this range, so that the arsenic leaching amount in the arsenic-containing neutralization slag after solidification treatment is 0.3487~0.7587 mg / kg, and the mercury leaching amount is lower, mostly undetectable.

[0030] Example 2 Raw materials of this embodiment: arsenic-containing neutralized slag, calcium hydroxide, ferrous sulfate, thiourea, cement; Arsenic-containing neutralized slag: arsenic content is between 0.5% and 3%; pH value is between 7.77 and 10.25; moisture content: 16.25% to 31.59%; soluble salt content: 6.03% to 8.92%; arsenic leaching: 10.45 mg / kg (total content 7047 to 26429 mg / kg); mercury leaching: 0.0044 mg / kg (total content 104.2307 mg / kg).

[0031] The raw materials are processed according to the following steps: (1) Add water or dry the arsenic-containing neutralization slag to obtain wet-based neutralization slag, so that the humidity of the wet-based neutralization slag is 30% to 60%; (2) adding calcium hydroxide to the wet-base neutralized slag, stirring to obtain a mixture I, and adjusting the pH of the mixture I to 10-12; The weight ratio of the wet-based neutralized slag to calcium hydroxide is 100:3-5; (3) Add ferrous sulfate to mixture I, stir and react to obtain mixture II, and adjust the pH of mixture II to 10-11; The weight ratio of the wet-based neutralized slag to ferrous sulfate is 15-20:1; (4) adding thiourea to the mixture II, mixing and reacting to obtain the mixture III, wherein the weight ratio of the wet neutralized residue to thiourea is 100:0.7-0.8; and the mixing reaction time is 15 min-20 min; (5) adding cement to the mixture III, stirring evenly to obtain a total mixture, and subjecting the mixture to natural curing to complete the solidification treatment of the arsenic-containing neutralized slag; The weight ratio of wet-base neutralized slag to cement is 10:1~2.5, and the cement used is C325 model.

[0032] (6) The total mixture after curing is tested for pH value, leached arsenic, leached mercury, and soluble salts.

[0033] Table 2 Performance data of arsenic-containing neutralized slag after solidification treatment with different weight ratios of calcium hydroxide and ferrous sulfate According to Table 2, the weight ratios of wet neutralization slag to calcium hydroxide and ferrous sulfate are 100:3~5 and 15~20:1 respectively. The addition amounts of calcium hydroxide and ferrous sulfate are variables. Too much or too little addition of the two will cause the leaching amount of mercury and arsenic to increase. The minimum value of arsenic leaching amount is 0.2307 mg / kg. At the same time, the salt content tends to increase.

[0034] In summary, the data results of Example 1 and Example 2 show that the addition amount of calcium hydroxide, ferrous sulfate and thiourea within this range can achieve an arsenic leaching amount of 0.2307~1.5738 mg / kg after solidification treatment, with a minimum value of 0.2307 mg / kg, which is significantly lower than the maximum limit of arsenic leaching amount in the "Identification of Hazardous Waste Identification Standard Leaching Toxicity Identification" (GB5085.3-2007) for the solidified material after curing; the arsenic-containing neutralized slag solidified material after solidification treatment can meet the requirements of flexible landfill disposal, without the need to select rigid landfill, reducing the processing cost, and avoiding the cost and risk of secondary excavation disposal.

[0035] The above description is only a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with the profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A solidification treatment method for reducing the amount of arsenic leaching from arsenic-containing neutralized slag, characterized in that: The following steps are involved: Step 1: pre-treating the humidity of the arsenic-containing neutralized slag to obtain wet-based neutralized slag; Step 2: adding calcium hydroxide to the wet base and slag to obtain a mixture I; Step 3: adding ferrous sulfate to mixture I to obtain mixture II; Step 4: adding a chelating agent to mixed material II to obtain mixed material III; Step 5: Add cement to mixture III, and obtain arsenic-containing neutralized slag solidified material after solidification.

2. A solidification treatment method for reducing the amount of arsenic leaching from arsenic-containing neutralized slag according to claim 1, characterized in that: The humidity of the wet-based neutralized slag is 30% to 60%.

3. A solidification treatment method for reducing the arsenic leaching amount in arsenic-containing neutralized slag according to claim 1, characterized in that: The humidity pretreatment method is adding water or drying.

4. A solidification treatment method for reducing the arsenic leaching amount in arsenic-containing neutralized slag according to claim 1, characterized in that: In the step 2, the pH of the mixture I is adjusted to 10-12; The weight ratio of the wet-based neutralized slag to calcium hydroxide is 100:3-5.

5. A solidification treatment method for reducing the arsenic leaching amount in arsenic-containing neutralized slag according to claim 1, characterized in that: In the step 3, the pH of the mixture II is adjusted to 10-11; The weight ratio of the wet-based neutralized slag to ferrous sulfate is 15-20:

1.

6. A solidification treatment method for reducing the arsenic leaching amount in arsenic-containing neutralized slag according to claim 1, characterized in that: In the step 4, the weight ratio of the wet-based neutralization residue to the chelating agent is 100:0.5-0.

8.

7. A solidification treatment method for reducing the amount of arsenic leaching from arsenic-containing neutralized slag according to claim 1, characterized in that: The chelating agent is thiourea.

8. A solidification treatment method for reducing the arsenic leaching amount in arsenic-containing neutralized slag according to claim 7, characterized in that: The mixing reaction time of the wet-based neutralization residue and thiourea is 15 min to 20 min.

9. A solidification treatment method for reducing the arsenic leaching amount in arsenic-containing neutralized slag according to claim 7, characterized in that: The weight ratio of the wet-based neutralized slag to cement is 10:1-4.

10. A solidification treatment method for reducing the arsenic leaching amount in arsenic-containing neutralized slag according to claim 7, characterized in that: The cement used is C325 type.

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