Heavy metal contaminated sludge multi-innocentization agent and use method thereof

Abstract

The application discloses a kind of heavy metal pollution sludge multiple harmless reagent and its using method, the proportion of each component in total sludge weight is as follows: reducing agent 0.5%-1%, precipitant 2%-4%, curing agent 2%-4%, protective agent 0.5%-1%; the protective agent is the mixture of sawdust ash, wood ash, sodium borate and grass carbon, wherein the mass ratio of sawdust ash in protective agent is 10%-30%, the mass ratio of wood ash in protective agent is 10%-30%, the mass ratio of sodium borate in protective agent is 30%-50%, and the mass ratio of grass carbon in protective agent is 20%-40%. The application adopts multiple stable curing technology integrating reduction, precipitation, curing and protection, is economic and environmental protection, and uses the mixture of sawdust ash, wood ash, sodium borate and grass carbon as protective agent for final protection, effectively solves the pollution problem of heavy metal sludge in acid rain environment.

Description

Technical Field

[0001] This invention relates to the field of heavy metal pollution treatment technology for rivers and lakes. More specifically, this invention relates to a multi-stage harmless treatment agent for heavy metal-contaminated sludge and its application method. Background Technology

[0002] In the early stages of my country's chemical industry development, the treatment of industrial wastewater was insufficient, resulting in the discharge of large amounts of heavy metals such as Cr, Pb, Hg, As, Ni, Cd, and Zn into rivers and lakes. Over time, these heavy metals gradually accumulated. Heavy metals exist in sludge in various forms, including dissolved, exchangeable, carbonate-bound, organically bound, and residual states. Among these, iron and manganese oxide-bound and residual states are relatively stable and less affected by environmental changes. However, free, exchangeable, and carbonate-bound heavy metals are easily transformed and released into water bodies with environmental changes, posing a potential risk to the health of residents, not only harming the aquatic ecosystems of rivers and lakes but also posing a threat to public health.

[0003] Currently, domestic and international technologies for the remediation of heavy metal pollution in rivers and lakes are mainly divided into removal methods and stabilization methods. Heavy metal removal methods primarily include adsorption, chemical leaching, electrokinetic remediation, and bioleaching. While these methods can remove heavy metals from sludge, their high operating costs and operational difficulties limit their widespread application. Chemical solidification stabilization is one of the most widely used heavy metal stabilization methods in engineering. It mainly uses solidification stabilizers such as cement and lime to seal and fix heavy metals through hydration reactions, thereby achieving the goal of harmlessness.

[0004] Currently, the gel hardening of hydraulic materials in chemical solidification stabilization technology can only physically encapsulate heavy metals. While heavy metals such as Ni, Cd, and Zn can precipitate and stabilize in alkaline environments, heavy metals such as Cr and As remain in highly hazardous high-valence states. Once the soil is exposed to external environmental factors such as humic acid and acid rain, the precipitated and solidified heavy metals are likely to be directly exposed back into the soil environment, posing a significant risk of secondary pollution. Furthermore, the hydration reaction of cement and other cementing materials results in highly alkaline sludge, which is detrimental to the growth of soil organisms. Summary of the Invention

[0005] The purpose of this invention is to provide a multi-component harmless treatment agent for heavy metal contaminated sludge and its application method. It adopts a multi-stage stabilization and solidification technology that integrates reduction, precipitation, solidification and protection, which is economical and environmentally friendly. At the same time, it uses a mixture of sawdust ash, wood ash, sodium borate and peat as a protective agent for final protection, which effectively solves the pollution problem of heavy metal sludge in acid rain environment.

[0006] The technical solution adopted by this invention to solve this technical problem is: to provide a multi-component harmless treatment agent for heavy metal contaminated sludge, wherein the proportion of each component to the total weight of the sludge is as follows:

[0007] Reducing agent 0.5%-1%, precipitant 2%-4%, curing agent 2%-4%, protective agent 0.5%-1%.

[0008] Preferably, the multiple harmless treatment agent for heavy metal contaminated sludge includes a protective agent that is a mixture of sawdust, wood ash, sodium borate, and peat moss, wherein sawdust accounts for 10% to 30% of the protective agent by mass, wood ash accounts for 10% to 30% of the protective agent by mass, sodium borate accounts for 30% to 50% of the protective agent by mass, and peat moss accounts for 20% to 40% of the protective agent by mass.

[0009] Preferably, in the multiple harmless treatment agent for heavy metal contaminated sludge, the reducing agent is a mixture of micro-nano zero-valent iron powder and sodium sulfide, wherein the mass ratio of micro-nano zero-valent iron powder to sodium sulfide is 2:1.

[0010] Preferably, the heavy metal contaminated sludge is treated with a multi-component harmless agent, and the precipitant is one or more of carbide slag and blast furnace slag.

[0011] Preferably, the solidifying agent in the heavy metal contaminated sludge multi-component harmless treatment agent is one or more of fly ash, phosphate rock powder, and lime.

[0012] Preferably, the present invention also provides a method for using a multi-stage harmless treatment agent for heavy metal contaminated sludge, which mainly includes the following steps:

[0013] a. Add the reducing agent to the sludge after preliminary dehydration treatment and forcibly stir to mix;

[0014] b. Add the precipitant to the mixture from step a, stir vigorously until homogeneous, and then let stand.

[0015] c. Once the sludge in step b shows obvious stratification, drain the upper clear liquid, add the solidifying agent to the bottom sediment, forcibly stir evenly, and allow to cure naturally.

[0016] d. When applying stabilized and solidified sludge, add the protective agent during the crushing process;

[0017] e. Harmlessly treated river and lake silt can be used as engineering filler and greening soil.

[0018] The present invention has at least the following beneficial effects:

[0019] 1. This invention effectively avoids the environmental leakage risks and hazards of stabilized and solidified heavy metals through multiple stabilization and solidification technologies. The use of a protective agent for final protection effectively solves the pollution problem of heavy metal sludge in acid rain environments.

[0020] 2. The resource utilization of industrial waste residue significantly reduces the amount of cementitious materials used and increases the application range of harmless heavy metal sludge, resulting in significant economic and environmental benefits.

[0021] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0022] Figure 1 This is a schematic diagram illustrating the working principle of a multi-stage harmless treatment agent for heavy metal contaminated sludge. Detailed Implementation

[0023] The present invention will now be described in detail and completely with reference to the accompanying drawings. Those skilled in the art will be able to implement the present invention based on these descriptions. Before describing the present invention with reference to the accompanying drawings, it should be particularly noted that the technical solutions and features provided in various parts of the present invention, including the following description, can be combined with each other without conflict.

[0024] Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0025] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. The specific implementation process is as follows:

[0026] A multi-component harmless treatment agent for heavy metal contaminated sludge, with the following proportions of each component by weight of the sludge:

[0027] Reducing agent 0.5%-1%, precipitant 2%-4%, curing agent 2%-4%, protective agent 0.5%-1%.

[0028] Furthermore, the multiple harmless treatment agent for heavy metal contaminated sludge includes a protective agent that is a mixture of sawdust, wood ash, sodium borate, and peat moss, wherein sawdust accounts for 10% to 30% of the protective agent by mass, wood ash accounts for 10% to 30% of the protective agent by mass, sodium borate accounts for 30% to 50% of the protective agent by mass, and peat moss accounts for 20% to 40% of the protective agent by mass.

[0029] Sawdust ash and peat can neutralize the alkaline environment of the stabilized and solidified sludge, while sodium phosphate and sodium borate are evenly distributed on the surface of the stabilized and solidified microparticles, preventing the erosion of acidic substances and protecting the stabilized and solidified sludge.

[0030] Furthermore, in the aforementioned multi-component harmless treatment agent for heavy metal contaminated sludge, the reducing agent is a mixture of micro-nano zero-valent iron powder and sodium sulfide, wherein the mass ratio of micro-nano zero-valent iron powder to sodium sulfide is 2:1.

[0031] Medium-alkaline reducing agents such as iron powder and sodium sulfide can reduce the high-valence, highly toxic, and persistently dangerous As(V) and Cr(VI) in sludge to low-valence As(III) and Cr(III), significantly reducing their biological hazards. At the same time, the iron ions generated after the oxidation of micro-nano zero-valent iron powder can not only react with As(III) to precipitate, but also hydrolyze to produce flocculation, adsorbing heavy metals in the water and achieving preliminary precipitation stabilization.

[0032] Furthermore, the heavy metal contaminated sludge multi-harmless treatment agent mentioned above, wherein the precipitant is one or more of carbide slag and blast furnace slag.

[0033] The calcium carbide slag and blast furnace slag contain alkaline oxides such as CaO and MgO, which generate a large number of hydroxide ions when they come into contact with water, precipitating heavy metals such as Cr, Pb, Hg, Ni, Cd, and Zn in the sludge, thus achieving precipitation stabilization of various heavy metals.

[0034] Furthermore, the solidifying agent in the aforementioned heavy metal contaminated sludge multi-component harmless treatment agent is one or more of fly ash, phosphate rock powder, and lime.

[0035] Cement, phosphate rock powder, and fly ash can hydrate to produce a large amount of cementitious products, which further precipitate heavy metals while encapsulating and sealing the stable heavy metal precipitates produced by reduction and precipitation, thus initially preventing the leakage of heavy metal stabilizers. The high-valence iron ions produced by the reducing agent reaction also play a certain role in promoting the hydration of cementitious materials.

[0036] like Figure 1 As shown, the present invention also provides a method for using a multi-stage harmless treatment agent for heavy metal contaminated sludge, which mainly includes the following steps:

[0037] a. Add the reducing agent to the sludge after preliminary dehydration treatment and forcibly stir and mix thoroughly; convert the high-valence heavy metals in the sludge into low-valence states, thereby reducing their harmfulness.

[0038] b. Add the precipitant to the mixture in step a, stir for 2 minutes, and let stand for 60 minutes; the hydroxide ions in the precipitant combine with the heavy metals to undergo a precipitation reaction.

[0039] c. Once the sludge in step b shows obvious stratification, drain the upper clear liquid, add the solidifying agent to the bottom sediment, forcibly stir evenly, and allow to cure naturally for 7 days; the solidifying agent granulates the heavy metal precipitate particles generated in steps a and b, encapsulates and seals them, and initially prevents the leakage of heavy metal stabilizers.

[0040] d. When applying the stabilized and solidified sludge, the protective agent is added during the crushing process; the protective agent is distributed on the surface of the stabilized and solidified microparticles to prevent them from being corroded by acidic substances, which would lead to the exposure of heavy metals.

[0041] e. Harmlessly treated river and lake silt can be used as engineering filler and greening soil.

[0042] The technical solution of the present invention will be demonstrated below with reference to specific embodiments. The river and lake dredging sediment used has a water content of 60%-70%, a pH of 6.8, and heavy metal concentrations as shown in Table 1.

[0043] Table 1. Heavy metal concentrations in heavy metal-contaminated sludge

[0044]

[0045] Comparative Example 1

[0046] In this comparative example, the heavy metal sludge harmless treatment agent contains only a reducing agent, which accounts for 0.5% of the total weight of the sludge.

[0047] Comparative Example 2

[0048] In this comparative example, the heavy metal sludge harmless treatment agent contains only a precipitant, which accounts for 1% of the total weight of the sludge.

[0049] Comparative Example 3

[0050] In this comparative example, the heavy metal sludge harmless treatment agent contains only a solidifying agent, which accounts for 2% of the total weight of the sludge.

[0051] Comparative Example 4

[0052] In this comparative example, the heavy metal sludge harmless treatment agent contains only a protective agent, which accounts for 0.5% of the total weight of the sludge. The mass ratios of sawdust, wood ash, sodium borate, and peat moss in the protective agent components are 10%, 30%, 40%, and 20%, respectively.

[0053] Comparative Example 5

[0054] In this comparative example, the proportions of each component of the heavy metal sludge harmless treatment agent to the total weight of the sludge are: 0.5% reducing agent and 1% precipitant.

[0055] Comparative Example 6

[0056] In this comparative example, the proportions of each component of the heavy metal sludge harmless treatment agent to the total weight of the sludge are: reducing agent 0.5%, precipitant 1%, and solidifying agent 2%.

[0057] Example 1

[0058] In this embodiment, the proportions of each component of the heavy metal sludge harmless treatment agent to the total weight of the sludge are as follows: reducing agent 0.5%, precipitant 1%, solidifying agent 2%, and protective agent 0.5%. The mass proportions of sawdust ash, wood ash, sodium borate, and peat moss in the protective agent component are 10%, 30%, 40%, and 20%, respectively.

[0059] Example 2

[0060] In this embodiment, the proportions of each component of the heavy metal sludge harmless treatment agent to the total weight of the sludge are as follows: reducing agent 1%, precipitant 2%, solidifying agent 2%, and protective agent 0.5%. The mass ratios of sawdust ash, wood ash, sodium borate, and peat moss in the protective agent component are 20%, 30%, 25%, and 25%, respectively.

[0061] Example 3

[0062] In this embodiment, the proportions of each component of the heavy metal sludge harmless treatment agent to the total weight of the sludge are as follows: reducing agent 1%, precipitant 2%, solidifying agent 3%, and protective agent 1%. The mass proportions of sawdust ash, wood ash, sodium borate, and peat moss in the protective agent component are 20%, 30%, 25%, and 25%, respectively.

[0063] Example 4

[0064] In this embodiment, the proportions of each component of the heavy metal sludge harmless treatment agent to the total weight of the sludge are as follows: reducing agent 1%, precipitant 4%, solidifying agent 4%, and protective agent 1%. The mass proportions of sawdust ash, wood ash, sodium borate, and peat moss in the protective agent component are 30%, 20%, 30%, and 20%, respectively.

[0065] The leaching concentration of heavy metals in the river and lake sludge of each embodiment after stabilization and solidification with multiple harmless agents was determined according to the method in "Solid Waste Leaching Toxicity Test" (GB / T1555.1-15555.11) (unit: mg·g). -1 The measurement results are shown in Table 2.

[0066] Table 2. Heavy metal leaching detection results of the examples.

[0067]

[0068] Based on the data in Table 2, it can be seen that the multi-stage stabilization and solidification technology integrating reduction, precipitation, solidification, and protection adopted in this invention, compared with single heavy metal harmless treatment technologies, more effectively avoids the environmental leakage risks and environmental hazards of stabilized and solidified heavy metals. The use of a protective agent for final protection effectively solves the pollution problem of heavy metal sludge in acid rain environments. Simultaneously, the resource utilization of industrial waste significantly reduces the amount of cementitious materials used, increases the application range of harmless heavy metal sludge, and has significant economic and environmental benefits.

[0069] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and embodiments shown and described herein.

Claims

1. A method for using a multi-component harmless treatment agent for heavy metal contaminated sludge, characterized in that, Includes the following steps: a. Add a reducing agent to the sludge after preliminary dehydration and forcefully stir to mix; b. Add a precipitant to the mixture in step a, forcefully stir to mix evenly, and then let stand; c. Once the sludge in step b shows obvious stratification, drain the upper clear liquid, add a solidifying agent to the bottom sediment, forcibly stir until uniform, and allow to cure naturally. d. When applying stabilized and solidified sludge, add a protective agent during the crushing process; e. Harmlessly treated river and lake silt can be used as engineering filler and landscaping soil; The proportions of each component of the multiple harmless treatment agents for heavy metal contaminated sludge by the total weight of the sludge are as follows: Reducing agent 0.5%-1%, precipitant 2%-4%, curing agent 2%-4%, protective agent 0.5%-1%; The reducing agent is a mixture of micro-nano zero-valent iron powder and sodium sulfide, wherein the mass ratio of micro-nano zero-valent iron powder to sodium sulfide is 2:1; The precipitant is one or more of carbide slag and blast furnace slag; The curing agent is one or more of fly ash, phosphate rock powder and lime; The protective agent is a mixture of sawdust, wood ash, sodium borate and peat, wherein sawdust accounts for 10% to 30% of the protective agent by mass, wood ash accounts for 10% to 30% of the protective agent by mass, sodium borate accounts for 30% to 50% of the protective agent by mass, and peat accounts for 20% to 40% of the protective agent by mass.

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