Synchronous dehydration curing agent for arsenic-polluted bottom mud and application method of synchronous dehydration curing agent

Abstract

The invention discloses an arsenic-polluted bottom mud synchronous dehydration curing agent and an application method thereof, the curing agent comprises the following components by mass: 0.1%-5% of a coagulant A, 1%-5% of a curing stabilizer B and 0.05%-0.5% of a flocculant C, the addition amounts of the coagulant A, the curing stabilizer B and the flocculant C are respectively 0.1%-5%, 1%-5% and 0.05%-0.5% of the dry matter content of sludge; the coagulant A is at least one of ferric salt and aluminum salt; the curing stabilizer B comprises an alkaline curing material and an arsenic fixing agent; and the flocculant C is at least one of cationic polyacrylamide, anionic polyacrylamide or nonionic polyacrylamide. The method is synchronously added in the conditioning process of the arsenic-polluted bottom mud, secondary conditioning generated by separation in dehydration and solidification stabilization links of the arsenic-polluted bottom mud is avoided, the dehydrated mud cake can reach a certain strength after being cured and stabilizes the arsenic element in the sludge, the arsenic content in the leachate can be reduced by 90% or above, and the arsenic content in the leachate can be reduced by 90% or above. And the maintained mud cake can be used for resource utilization of land such as roadbed soil and filling soil.

Description

Technical Field

[0001] The invention relates to a curing agent and a preparation method thereof, in particular to an arsenic-contaminated sludge synchronous dehydration curing agent and an application method thereof. Background Art

[0002] At present, many rivers are polluted by heavy metals to varying degrees, and arsenic contamination of sediments has become a common phenomenon. The content of arsenic in the earth's crust is not high, even lower than some rare elements. It has the characteristics of high toxicity at low doses, difficulty in degradation, and variability in form. With the large-scale development of dredging projects, a huge amount of dredged mud has been brought in, part of which is contaminated by arsenic. It is necessary to consider the stabilization of heavy metal arsenic during the sludge treatment process.

[0003] Patent CN118045858 A discloses a method for solidifying and stabilizing heavy metal arsenic in soil, using industrial solid waste scrap iron and safe and harmless chitosan as raw materials to prepare a solidifying / stabilizing agent, giving full play to its adsorption, complexation and precipitation of arsenic-containing pollutants, and achieving the purpose of treating waste with waste. Patent CN 105537247B discloses a method for solidifying arsenic-containing waste residue using industrial waste residue, using waste residue generated by non-ferrous metal smelters themselves, with basically zero material cost, while achieving the excellent effect of treating waste with waste.

[0004] Although the existing technology has made certain progress, it still has the following problems:

[0005] (1) The dehydration and solidification and stabilization treatment of arsenic-contaminated sludge are carried out separately. The mud cake after dehydration needs to undergo secondary dosing and solidification and stabilization treatment, which increases the number of steps and costs of sludge treatment.

[0006] (2) The curing agent can also be used as a sludge dehydration conditioning agent. Using the curing agent alone after the sludge is dehydrated does not fully utilize the dehydration conditioning properties of the curing agent. Summary of the invention

[0007] Purpose of the invention: The purpose of the present invention is to provide an arsenic-contaminated sludge synchronous dehydration and solidification agent that can simultaneously dehydrate and solidify the sludge and significantly reduce the arsenic content in the leachate;

[0008] The second object of the present invention is to provide an application method of the above-mentioned arsenic-contaminated sludge synchronous dehydration and solidification agent.

[0009] Technical solution: The arsenic-contaminated sludge synchronous dehydration solidifying agent of the present invention comprises the following components by mass percentage: coagulant A, solidifying stabilizer B and flocculant C, and the addition amounts are 0.1% to 5%, 1% to 5%, and 0.05% to 0.5% of the sludge dry matter content respectively;

[0010] The coagulant A is at least one of an iron salt and an aluminum salt;

[0011] The curing stabilizer B includes an alkaline curing material and an arsenic fixing agent;

[0012] The flocculant C is at least one of cationic polyacrylamide, anionic polyacrylamide or nonionic polyacrylamide.

[0013] Wherein, the alkaline solidifying material is at least one of cement, lime, gypsum, fly ash or polymer soil solidifying agent.

[0014] The arsenic fixing agent in the solidifying stabilizer B is magnetically separated iron concentrate obtained by ball milling and / or magnetic separation of industrial waste slag.

[0015] Among them, the arsenic fixer in the solidifying stabilizer B is magnetically separated iron concentrate; the magnetically separated iron concentrate is added according to the molar ratio of Fe3O4 to the molar ratio of arsenic element in arsenic-contaminated sludge of n(Fe3O4):n(As)=(0.10~3):1, and the added amount is 0.1%~1.8% of the dry matter of the sludge.

[0016] The application method of the above-mentioned arsenic-contaminated sludge synchronous dehydration solidifying agent comprises the following steps:

[0017] (1) Determine the solid content, particle size composition and arsenic content of arsenic-contaminated sediment;

[0018] (2) adding coagulant A to the arsenic-contaminated sludge at a ratio of 0.1% to 5% of the sludge dry matter content, and mixing and stirring;

[0019] (3) weighing an alkaline solidifying material according to 1-5% of the dry matter content of the sludge, weighing an arsenic fixative according to a molar ratio of n(Fe3O4):n(As)=(0.10-3):1 or 0.1%-1.8% of the dry matter of the sludge, mixing the alkaline solidifying material and the arsenic fixative, and adding them to the arsenic-contaminated sludge, mixing and stirring;

[0020] (4) adding flocculant C to the arsenic-contaminated sludge at a ratio of 0.05% to 0.5% of the sludge dry matter content, and mixing and stirring;

[0021] (5) Allow the sediment to settle and dehydrate the sediment to obtain dehydrated sludge.

[0022] Wherein, in step (2), the coagulant A is prepared into a solution with an effective content of 3% to 10%, and the solution is weighed according to 0.1% to 5% of the dry matter content of the sludge and added to the arsenic-contaminated sludge.

[0023] Wherein, in step (2), when coagulant A is aluminum salt, the aluminum salt is added according to 0.1% to 1% of the dry matter content of the sludge; when coagulant A is iron salt, the iron salt is added according to 0.5% to 5% of the dry matter content of the sludge.

[0024] Wherein, in step (4), the flocculant C is prepared into a solution with an effective content of 0.1% to 0.3%, and the solution is weighed according to 0.05% to 0.5% of the mud dry matter content and added to the arsenic-contaminated sludge.

[0025] Wherein, in step (5), the solid content of the dehydrated sludge reaches 60-80%, preferably 60-75%; and the dehydrated mud cake is left to stand for curing for 7-28 days.

[0026] The arsenic-contaminated sludge is dredging engineering of arsenic-contaminated sludge in rivers, lakes, reservoirs and other water bodies, which uses environmentally friendly suction dredging, and the sludge generally undergoes processes such as impurity removal and screening.

[0027] Beneficial effects: Compared with the prior art, the present invention achieves the following significant effects:

[0028] (1) The dehydration solidifying agent provided by the present invention is added simultaneously during the conditioning process of arsenic-contaminated sludge, thereby avoiding the secondary conditioning caused by the separation of the dehydration and solidification stabilization links of the arsenic-contaminated sludge. After a period of curing, the dehydrated mud cake can reach a certain strength and stabilize the arsenic element in the sludge. The arsenic content in the leachate can be reduced by more than 90%. The cured mud cake can be used for land use such as roadbed soil and fill soil for resource utilization, thereby reducing environmental risks. (2) The dehydration solidifying agent provided by the present invention can significantly accelerate the dehydration rate of sludge, shorten the sludge processing time and processing links. (3) The sludge synchronous dehydration solidifying agent and application method provided by the present invention are simple to operate and suitable for large-scale application. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is the process flow chart for simultaneous dehydration and solidification of arsenic-contaminated sludge. DETAILED DESCRIPTION

[0030] The present invention is described in further detail below.

[0031] Example 1

[0032] like Figure 1 As shown, a method for applying an arsenic-contaminated sludge synchronous dehydration solidification agent comprises the following steps:

[0033] (1) The treatment object is the arsenic-contaminated bottom mud of Datunhai Reservoir. Its basic physical properties are shown in Table 1.

[0034] Table 1 Basic properties of arsenic-contaminated sludge in Datunhai Reservoir

[0035]

[0036] The arsenic-contaminated bottom mud was removed from impurities and passed through a 2 cm sieve, and the dehydration solidifying agent of the present invention was added to the mud under the sieve. The components, dosing methods and addition amounts of the dehydration solidifying agent added are shown in Table 2.

[0037] Table 2 Dehydration curing agent component 1

[0038]

[0039] Among them, for coagulants, first take a large amount of polyaluminium chloride to dissolve into a solution with an effective content of 3%, then weigh the solution according to 0.4% of solute / dry matter, and add it to the mud for reaction; for flocculants, first take a large amount of anionic polyacrylamide to dissolve into a solution with a solid content of 0.2%, then weigh the solution according to 0.06% of solute / dry matter, and add it to the mud for reaction.

[0040] Add polyaluminium chloride, lime and magnetically separated iron concentrate in sequence and stir evenly. Use a mud pump to pump the slurry to the sedimentation tank, add anionic polyacrylamide in the pipeline for static mixing, and let it stand in the sedimentation tank for 30 minutes.

[0041] The solid content of the concentrated mud after the addition of chemicals and precipitation was 28.4%. The bottom concentrated mud was pumped into the plate and frame mill by a plunger pump. The filter press dehydration parameters were 1.2 MPa for 1 h and 2.0 MPa for 1 h to obtain the dehydrated mud cake. The mud cake was collected with a mold and cured for 14 days. The physical and chemical properties, unconfined compressive strength and pollutant leaching amount of the mud cake were measured, as shown in Table 3.

[0042] Example 2

[0043] On the basis of Example 1, different from Example 1, the coagulant, the solidifying stabilizer and the flocculant are all added in minimum amounts, as shown in Table 3.

[0044] Table 3 Dehydration curing agent component 2

[0045]

[0046] Example 3

[0047] On the basis of Example 1, the difference from Example 1 is that the coagulant, the solidifying stabilizer and the flocculant are all added in maximum amounts, as shown in Table 4.

[0048] Table 4 Dehydration curing agent component 3

[0049]

[0050] Comparative Example 1

[0051] On the basis of Example 1, the difference from Example 1 is that polyaluminium chloride and anionic polyacrylamide are added in the same amount when conditioning the mud.

[0052] Table 5 Dehydration curing agent component 4

[0053]

[0054] Comparative Example 2

[0055] On the basis of Example 1, the difference from Example 1 is that polyaluminium chloride and curing stabilizer are added in the same amount when conditioning the mud.

[0056] Table 6 Dehydration curing agent component 5

[0057]

[0058] Comparative Example 3

[0059] On the basis of Example 1, the difference from Example 1 is that a curing stabilizer and anionic polyacrylamide are added in the same amount when conditioning the mud.

[0060] Table 7 Dehydration curing agent component 6

[0061]

[0062] Comparative Example 4

[0063] On the basis of Example 1, the difference from Example 1 is that only lime is added as the solidification stabilizer.

[0064] Table 8 Dehydration curing agent component 7

[0065]

[0066]

[0067] Comparative Example 5

[0068] Based on Example 1, the difference from Example 1 is that the solidification stabilizer is only added to the magnetically separated iron ore concentrate.

[0069] Table 9 Dehydration curing agent component 8

[0070]

[0071] The properties of the dehydrated water cakes of Examples 1 to 3 and Comparative Examples 1 to 5 are shown in Table 10.

[0072] Table 10 Dewatered Cake Properties

[0073]

[0074] It can be seen from Comparative Examples 1, 2 and 3 that no solidifying stabilizer was added during the mud conditioning process, i.e., in Comparative Example 1, the water content of the mud cake was relatively high, the leachate was acidic, and the arsenic content in the leachate reached 1.655 mg / L, which was inferior Class V water according to the "Surface Water Environmental Quality Standard" GB3838-2002; no flocculant was added during the mud conditioning process, i.e., in Comparative Example 2, the water content of the mud cake was >40%, and the unconfined compressive strength of the mud cake could not be measured; no coagulant was added in the mud conditioning, i.e., in Comparative Example 3, the water content of the mud cake was relatively high, and the pH of the mud cake was >9, which did not meet the general soil standards.

[0075] It can be seen from Comparative Examples 4 and 5 that no arsenic fixative was added during the mud conditioning process, i.e., in Comparative Example 4, the arsenic content in the mud cake leachate was 0.394 mg / L, which was inferior Class V water; no alkaline solidifying material was added during the mud conditioning process, i.e., in Comparative Example 5, the water content of the mud cake was high, and the arsenic content in the leachate was 0.256 mg / L, which was inferior Class V water.

[0076] In summary, it can be seen that the present invention simultaneously adds flocculants, coagulants, alkaline solidifying materials and heavy metal fixatives during the dehydration treatment of arsenic-contaminated sludge. The test results also show that the addition of alkaline solidifying materials and heavy metal fixatives can not only accelerate the dehydration efficiency, but also significantly reduce the leaching amounts of pollutants such as arsenic and nitrogen and phosphorus in the dehydrated mud cake. At the same time, the dehydration and solidification treatments are completed, and the two links of dehydration and solidification treatments in general engineering are combined into one, which is more efficient.

Claims

1. A synchronous dehydration and solidification agent for arsenic-contaminated sludge, characterized in that: The components are as follows by mass percentage: coagulant A, solidifying stabilizer B and flocculant C, the addition amounts of which are 0.1% to 5%, 1% to 5%, and 0.05% to 0.5% of the sludge dry matter content respectively; The coagulant A is at least one of an iron salt and an aluminum salt; The curing stabilizer B includes an alkaline curing material and an arsenic fixing agent; The flocculant C is at least one of cationic polyacrylamide, anionic polyacrylamide or nonionic polyacrylamide.

2. The arsenic-contaminated sludge synchronous dehydration solidifying agent according to claim 1, characterized in that: The alkaline solidifying material is at least one of cement, lime, gypsum, fly ash or a polymer soil solidifying agent.

3. The arsenic-contaminated sludge synchronous dehydration solidifying agent according to claim 1, characterized in that: The arsenic fixing agent in the solidifying stabilizer B is magnetically separated iron concentrate obtained by ball milling and / or magnetic separation of industrial waste slag.

4. The arsenic-contaminated sludge synchronous dehydration solidifying agent according to claim 1, characterized in that: The arsenic fixer in the solidifying stabilizer B is magnetically separated iron concentrate; the magnetically separated iron concentrate is added according to the molar ratio of Fe3O4 to the molar ratio of arsenic element in arsenic-contaminated sludge, which is n(Fe3O4):n(As)=(0.10-3):1, and the added amount is 0.1%-1.8% of the dry matter of the sludge.

5. A method for applying the arsenic-contaminated sludge synchronous dehydration solidifying agent according to claim 1, characterized in that: The following steps are involved: (1) Determine the solid content, particle size composition and arsenic content of arsenic-contaminated sediment; (2) adding coagulant A to the arsenic-contaminated sludge at a ratio of 0.1% to 5% of the sludge dry matter content, and mixing and stirring; (3) weighing an alkaline solidifying material according to 1-5% of the dry matter content of the sludge, weighing an arsenic fixative according to a molar ratio of n(Fe3O4):n(As)=(0.10-3):1 or 0.1%-1.8% of the dry matter of the sludge, mixing the alkaline solidifying material and the arsenic fixative, and adding them to the arsenic-contaminated sludge, mixing and stirring; (4) adding flocculant C to the arsenic-contaminated sludge at a ratio of 0.05% to 0.5% of the sludge dry matter content, and mixing and stirring; (5) Allow the sediment to settle and dehydrate the sediment to obtain dehydrated sludge.

6. The application method of the arsenic-contaminated sludge synchronous dehydration solidifying agent according to claim 5, characterized in that: In step (2), the coagulant A is prepared into a solution with an effective content of 3% to 10%, and the solution is weighed according to 0.1% to 5% of the dry matter content of the sludge and added to the arsenic-contaminated sludge.

7. The application method of the arsenic-contaminated sludge synchronous dehydration solidifying agent according to claim 5, characterized in that: In step (4), the flocculant C is prepared into a solution with an effective content of 0.1% to 0.3%, and the solution is weighed according to 0.05% to 0.5% of the mud dry matter content and added to the arsenic-contaminated sludge.

8. The application method of the arsenic-contaminated sludge synchronous dehydration solidifying agent according to claim 5, characterized in that: In step (2), when the coagulant A is an aluminum salt, the aluminum salt is added according to 0.1% to 1% of the dry matter content of the sludge; when the coagulant A is an iron salt, the iron salt is added according to 0.5% to 5% of the dry matter content of the mud.

9. The application method of the arsenic-contaminated sludge synchronous dehydration solidifying agent according to claim 5, characterized in that: In step (5), the solid content of the sludge after dewatering reaches 60-80%.

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