A solidifying agent and method for fixing arsenic in riverbed mud

Abstract

The present invention discloses a curing agent and method for fixing arsenic in riverbed mud, which belongs to the technology for treating heavy metal pollution in mud. It belongs to the technical field of treating heavy metal pollution in mud. The present application comprises mixing Schmidt mineral, cement and water to form a curing slurry, adding the smidt mineral to the riverbed mud and mixing evenly, wherein the amount of the added smidt mineral is 0.5%-5% of the mass of the riverbed mud, the amount of the added cement is 3%-20% of the mass of the riverbed mud, and the amount of the added water is water: Schmidt mineral + cement (v:w) = (0.3-0.5):1. The method continuously stabilizes the arsenic in the mud by the Schmidt mineral to prevent it from being released into the water body, and fixes the Schmidt mineral and the mud mixture in the riverbed by a small amount of cement to avoid the loss of the Schmidt mineral during the flood season.

Description

Technical Field

[0001] The invention belongs to a technology for treating heavy metal pollution in riverbed mud, and specifically relates to a curing agent and a method for fixing arsenic in riverbed mud. Background Art

[0002] Arsenic-containing tailings, slag, smelting wastewater and other wastes generated by long-term arsenic-containing mineral mining and smelting activities (such as gold mining and smelting) have been discharged into natural water bodies such as rivers, lakes and other natural water bodies flowing through mining areas by human or rainwater due to factors such as weak environmental awareness in the early stage, weak supervision, imperfect stacking management system and economic development restrictions. Over time, arsenic accumulates in the bottom mud and then enters the water body through endogenous continuous release, posing a great threat to aquatic ecosystems and human life and health.

[0003] Arsenic is difficult to be purified naturally and must be treated and repaired through human intervention, such as sediment dredging and in-situ covering technology, which directly or indirectly removes arsenic-containing sediment with the help of large-scale engineering equipment and isolation materials. However, this method is only applicable to small water bodies, and the principle and operation are simple. However, in the face of large basins such as rivers, lakes, etc., there are disadvantages of huge engineering workload, and the subsequent legacy problems such as sediment storage are difficult to solve. Another example is plant remediation and microbial remediation technology. Among them, plant remediation mainly absorbs arsenic in sediment through its own growth, and microbial remediation changes arsenic toxicity through biological adsorption and redox. However, in actual remediation, the growth period of plants often coincides with the flood season of the basin, and they cannot grow normally. In addition, the subsequent treatment of plants after absorbing arsenic still faces the risk of secondary release of arsenic into the food chain. Microbial remediation is still in the laboratory research stage, and the actual application effect is not significant. Therefore, it is particularly urgent to find a method to fix arsenic in river sediment so that it will not be released into the water body. Summary of the invention

[0004] 1. Problem to be solved

[0005] Aiming at the environmental problem that arsenic is contaminated in riverbed mud and causes excessive arsenic in water bodies through endogenous release, the first purpose of the present invention is to provide a solidifying agent for fixing arsenic in riverbed mud;

[0006] The second object of the present invention is to provide a method for fixing arsenic in riverbed mud, which method can stabilize arsenic in riverbed mud for a long time.

[0007] 2. Technical solution

[0008] The present invention is mainly achieved by the following technical solutions:

[0009] The first object of the present invention is to provide a solidifying agent for fixing arsenic in riverbed mud. The solidifying agent comprises schreberitide and cement. The addition amount of schreberitide is 0.5%-5% of the mass of the riverbed mud, and the addition amount of cement is 3%-20% of the mass of the riverbed mud.

[0010] Furthermore, water is added to the curing agent, and the amount of water added is water: Schottky mineral+cement (v:w)=(0.3-0.5):1.

[0011] Schmidtite is a poorly crystalline, metastable secondary ferric hydroxysulfate mineral with a large amount of HO in its structure. - and SO4 2- Active functional groups such as ferrite and ferrihydrite have high efficiency in passivating arsenic and can be used for high efficiency passivation of arsenic in polluted water and soil. Studies have found that the maximum adsorption capacity of schreiterite for trivalent arsenic is as high as 100-250 mg / g, and its passivation ability is much higher than that of other iron minerals such as lepidocrocite, ferrihydrite, hematite, and goethite.

[0012] The specific surface area of ​​the Schmidtite mineral in this application is greater than 200m 2 / g, so that the arsenic in the riverbed mud is fully adsorbed in the Schroeder mineral.

[0013] Furthermore, the cement is silicate cement. In addition, other types of cement, such as aluminate cement, sulphoaluminate cement, ferroaluminate cement, fluoroaluminate cement, phosphate cement, cement with volcanic ash or potential hydraulic material and other active materials as main components, which can react with water to hydrate and fix the Schroeder mineral to make it not easy to lose, are all applicable.

[0014] It should be noted that the ratio of the "curing agent" as described herein affects the effect of arsenic curing; the curing agent of the present application includes Schmidt mineral, cement and water, wherein the cement is hydrated in water to form a gelling substance, which is used to fix the Schmidt mineral and prevent the loss of the Schmidt mineral. Preferably, the mass of the Schmidt mineral and the cement is 1:1, and the curing degree of the riverbed is adjusted by controlling the amount of cement added. If the cement ratio is too large, the curing degree of the riverbed is too high, affecting its fluidity. If the cement ratio is too low, the curing effect of the Schmidt mineral is not good; if the amount of the Schmidt mineral added is too small, the arsenic solidification effect is not good, and if the amount of the Schmidt mineral added is too large, the cost is too high. In addition, the addition of water is to achieve uniform mixing of the Schmidt mineral and cement to form a solidified slurry. The specific amount of addition is adjusted according to the actual situation and injected into the riverbed mud. The actual riverbed mud also contains water. The cement hydration step mainly occurs after the solidified slurry is mixed with the riverbed mud.

[0015] Another object of the present invention is to provide a method for fixing arsenic in riverbed mud, which uses the above-mentioned curing agent and specifically comprises the following steps:

[0016] The curing agent including the Schroeder mineral and cement is mixed to form a curing slurry, which is then added into the riverbed mud and mixed evenly.

[0017] Furthermore, the added amount of the Schroeder mineral is 0.5%-5% of the mass of the riverbed mud, and the added amount of cement is 3%-20%.

[0018] Furthermore, water is added to the curing agent, and the amount of water added is water: Schottky mineral+cement (v:w)=(0.3-0.5):1.

[0019] The amount of water added is water:Schmidtite+cement (v:w)=(0.3-0.5):1.

[0020] Specifically, the schist mineral, cement and water are mixed in a mechanical stirring tank to form a solidified slurry, which is then injected into the bottom mud through a slurry pipe. At the same time, the mixing pile mechanical vehicle turns the bottom mud through a mixing drill bit to evenly distribute the solidified slurry in the bottom mud.

[0021] It should be noted that the addition of water is to achieve uniform mixing of the schreberite and cement to form a solidified slurry, which is mixed with the riverbed mud. In actual operation, in order to facilitate the full mixing of the curing agent and the riverbed mud, the schreberite, cement and water are generally mixed evenly and then injected into the riverbed mud.

[0022] Furthermore, in the above steps, the slurry outlet of the slurry pipe is fixed together with the mixing pile, and the solidifying slurry is injected through the slurry pipe while the mixing drill bit turns over the bottom mud. The grouting flow rate of the solidifying slurry is 20-30L / min.

[0023] Furthermore, before mixing the curing agent with the riverbed mud, the method further comprises the following steps:

[0024] Two diversion channels were built on both sides of the river to divert the water from the river;

[0025] The quality of the sediment that needs to be treated is determined based on the length, width, depth and sediment density of the river to be treated.

[0026] Furthermore, the length of the above-mentioned diversion channel is determined by the length of the river channel to be managed, and the width is determined by the terrain conditions, which can generally be 2-3m. This step can be omitted if the construction is carried out in the dry season.

[0027] Furthermore, in the above steps, the depth of the riverbed sediment to be treated is 0.5-1m.

[0028] 3. Beneficial effects

[0029] (1) A solidifying agent for fixing arsenic in riverbed mud of the present invention fixes the mixture of schrenkiogen and mud on the riverbed through a small amount of cement, thereby preventing the loss of schrenkiogen during the flood season;

[0030] (2) A method for fixing arsenic in riverbed sediment of the present invention, wherein the arsenic in the sediment is continuously stabilized by using schreber mineral to prevent it from being released into the water body, and a mixture of schreber mineral and sediment is fixed on the riverbed by using a small amount of cement, thereby effectively improving the arsenic fixation effect;

[0031] (3) A method for fixing arsenic in riverbed mud of the present invention, wherein the solidified slurry is added to the riverbed mud while stirring, thereby improving the mixing efficiency of the solidified slurry and the mud, and treating 1m 3 The time required for sedimentation is about 3-5 minutes. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The arsenic fixation effect of different amounts of Schroeder mineral on arsenic-contaminated sediment. In the figure, S is the effective As content in the sediment after adding Schroeder mineral, 1-1M is the effective As content in the sediment after adding 1-1M of Beckett; 2-1 is the effective As content in the sediment after adding 2-1M of Beckett;

[0033] Figure 2 The arsenic fixation effect of Schroeder mineral and cement combined to treat arsenic-contaminated sediment in the laboratory (a) and the change of arsenic concentration in the overlying water (b). In the figure, CK is the effective As content in the river sediment without adding a curing agent, Sch is the effective As content in the river sediment with the addition of Schroeder mineral and cement; 1-1M is the effective As content in the river sediment with the addition of Beckett 1-1M and cement, and 2-1M is the effective As content in the river sediment with the addition of Beckett 2-1M and cement.

[0034] Figure 3 On-site construction drawings for the combined treatment of arsenic-contaminated sludge by Shi's mineral and cement;

[0035] Figure 4 This is the actual application effect of the combined treatment of arsenic-contaminated sludge by Schiff mineral and cement. DETAILED DESCRIPTION

[0036] The present disclosure may be more easily understood by reference to the following description in conjunction with the accompanying drawings and examples, all of which constitute a part of the present disclosure. It should be understood that the present disclosure is not limited to the specific products, methods, conditions or parameters described and / or shown herein. Further, the terms used herein are only used for the purpose of describing specific embodiments by way of example and are not intended to be limiting unless otherwise stated.

[0037] It should also be understood that, for the sake of clarity, certain features of the present disclosure may be described herein in the context of a separate embodiment, but may also be provided in combination with each other in a single embodiment. That is, unless clearly incompatible or particularly not included, each separate embodiment is considered to be combinable with any other embodiment, and the combination is considered to represent another different embodiment. On the contrary, for the sake of simplicity, the various features of the present disclosure described in the context of a single embodiment may also be provided individually or in any sub-combination. Finally, although a particular embodiment may be described as part of a series of steps or part of a more general structure, each step or substructure itself may also be considered to be an independent embodiment.

[0038] In this disclosure, the singular forms of the articles "a," "an," and "the" also include the corresponding plural references, and a reference to a specific value includes at least that specific value unless the context clearly indicates otherwise. Thus, for example, a reference to "a substance" is a reference to at least one of that substance and equivalents thereof.

[0039] When items are described by using the conjunction terms "... and / or...," etc., the description should be understood to include any one of the associated listed items and all combinations of one or more thereof.

[0040] Concentration, amount and other numerical data can be presented in range format in this article.It should be understood that such range format is only used for convenience and simplicity, and should be flexibly interpreted as not only including the numerical value clearly described as range limit, but also including all single numerical values ​​or sub-ranges included in the range, just as each numerical value and sub-range are clearly described.For example, the numerical range of about 0.3 to about 0.5 should be interpreted as not only including the limit value of 0.3 to about 0.5 clearly described, but also including single numerals (such as 0.4) and sub-ranges (such as 0.3 to 0.4, 0.4 to 0.5, etc.).The same principle is applicable to the scope of only narrating a numerical value, such as "less than about 0.5", which should be interpreted as including all the above-mentioned values ​​and scopes.In addition, no matter how the breadth of the described scope or feature is, this explanation should be applicable.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention belongs; the terms used herein and / or include any and all combinations of one or more of the associated listed items.

[0042] It should be noted that, in the embodiments of the present invention, the riverbed mud was taken from the lower reaches of Jiehe River in Zhaoyuan City, Yantai City, Shandong Province, and the effective arsenic content was 1-100 mg / kg.

[0043] The preparation of Schmidt mineral refers to patent CN115920825A, and its specific surface area is greater than 200m 2 / g.

[0044] The cement is 425 type silicate cement.

[0045] The passivation rate in the embodiment is calculated in the following manner: the ratio of the reduction in the effective arsenic content measured after the curing agent / repairing agent treatment to the initial effective arsenic content is the passivation rate.

[0046] Comparative Example 1

[0047] Weigh 150g of arsenic-contaminated sludge into a plastic bottle, add 0.5%-5% of Beckett 1-1M remediation agent and Beckett 2-1M remediation agent according to the mass ratio, mix well, add water to keep moist, and cure for 10 days; take sludge samples on the 1st, 3rd, 5th, 7th and 10th days respectively, grind them and determine the effective arsenic content.

[0048] The results are as follows Figure 1 As shown, the effective arsenic content of the arsenic contaminated sludge used was 3.50 mg / kg. After 10 days of curing, for Beckett 1-1M remediation agent, the passivation rate of arsenic was 62.6% when 0.5% was applied, and the passivation rate of arsenic was 93.8% when 5% was applied. For Beckett 2-1M remediation agent, the passivation rate of arsenic was 60.4% when 0.5% was applied, and the passivation rate of arsenic was 94.3% when Beckett 2-1M 5% was applied.

[0049] Comparative Example 2

[0050] This comparative example provides a method for fixing arsenic in riverbed mud, which does not include the addition of cement and is a laboratory test, mainly comprising the following steps:

[0051] Weigh 150g of arsenic-contaminated sludge into a plastic bottle, add 0.5%-5% of Schroeder mineral according to the mass ratio, mix well, add water to keep it moist, and cure for 10 days; take sludge samples on the 1st, 3rd, 5th, 7th and 10th days respectively, grind them and determine the effective arsenic content.

[0052] The results are as follows Figure 1 As shown, the effective arsenic content of the arsenic-contaminated sludge used was 3.50 mg / kg, and the stabilizing effect of Schreiber mineral on arsenic increased with the increase of the added amount. After the sludge was cured for 10 days, the passivation rate of arsenic by applying 0.5% Schreiber mineral reached more than 79%, and the passivation rate of arsenic by applying 5% Schreiber mineral reached more than 94.4%.

[0053] Example 1

[0054] This embodiment provides a method for fixing arsenic in riverbed mud, which is a laboratory test and mainly includes the following steps:

[0055] S1: Weigh 150g of arsenic-contaminated sludge into a plastic bottle, add 3% of Schroeder mineral according to the mass ratio, mix well, add water to keep it moist, and cure for 4 days;

[0056] S2: Add 30g cement (i.e. 20% of the mass of the sediment) to the plastic bottle and mix with the cured sediment to solidify (the sediment is moist, no need to add water), let it stand for 2 days to completely solidify, then flood with water, with a water layer of 1-2cm (each treated solidified body volume is 100cm 3 , water volume 170mL). Before adding cement, take a sample to determine the effective arsenic content of the bottom mud. After that, take solidified samples at 1 month, 6 months, and 12 months of flooding, crush and grind them to determine the effective arsenic content. At the same time, take the overlying water sample to determine the arsenic concentration. The results are as follows: Figure 2 shown.

[0057] Comparative Example 3

[0058] The difference between Comparative Example 3 and Example 1 is that the curing agent used is Beckett 1-1M repair agent and Beckett 2-1M repair agent, which specifically includes the steps of:

[0059] S1: Weigh 150g of arsenic-contaminated sludge into a plastic bottle, add 3% of Beckett 1-1M and Beckett 2-1M remediation agents according to the mass ratio, mix well, add water to keep it moist, and cure for 4 days;

[0060] S2: Add 30g cement (i.e. 20% of the mass of the sediment) to the plastic bottle and mix with the cured sediment to solidify (the sediment is moist, no need to add water), let it stand for 2 days to completely solidify, then flood with water, with a water layer of 1-2cm (each treated solidified body volume is 100cm 3 , water volume 170mL). Before adding cement, take a sample to determine the effective arsenic content in the bottom mud. Then, take solidified samples at 1 month, 6 months, and 12 months of flooding, crush and grind them to determine the effective arsenic content. At the same time, take overlying water samples to determine the arsenic concentration. The results are as follows: Figure 2 As shown in a.

[0061] The results are as follows Figure 2 As shown in the figure, the effective arsenic content in the arsenic-contaminated sludge was 26.68 mg / kg. After fixation with Schmidtite and cement, the effective arsenic content dropped to below 0.5 mg / kg and remained stable for the next 12 months. In the 12th month, the passivation rates of Schmidtite, Beckett 1-1M and Beckett 2-1M on arsenic were 99.38%, 98.88% and 96.90%, respectively ( Figure 2a). In addition, the arsenic concentration of the overlying water in the group treated with Schmidt mineral and cement was more stable than that in the other experimental groups during the 12 months and did not exceed 10 μg / L. The untreated sediments and the sediments treated with Beckett 1-1M and Beckett 2-1M gradually released arsenic into the water body over time. The overlying water arsenic concentration of the sediments treated with Beckett 1-1M and Beckett 2-1M was the same as that of the Schmidt mineral treatment only in the first month ( Figure 2 b), the reason may be that the addition of cement leads to a local increase in pH, which inhibits the arsenic adsorption capacity of the two materials, but has little effect on schreberite, indicating that the addition of cement significantly improves the stability of schreberite in the sediment.

[0062] Example 2

[0063] This embodiment provides a method for fixing arsenic in riverbed mud, which is a practical engineering application case and mainly includes the following steps:

[0064] S1: During the dry season, two 3m wide diversion channels were built along both sides of the river to divert the residual water from the river;

[0065] S2: The length and width of the river to be treated are both 100m, and the treatment depth is 0.5m;

[0066] S3: Stirling mineral, cement and water are mixed in a mechanical stirring tank to form a solidified slurry. The amount of Stirling mineral added is 3% of the mass of the bottom mud, the amount of cement added is 3% of the mass of the bottom mud, and water is added at a ratio of water: Stirling mineral + cement (v:w) = 0.35:1. It is injected into the bottom mud through the slurry pipe. At the same time, the mixing pile mechanical vehicle turns the bottom mud through the mixing drill bit to make the solidified slurry evenly distributed in the bottom mud. The maximum mixing depth of the mixing drill bit is 0.5m. After one week of maintenance, samples are taken regularly to determine the effective arsenic content in the bottom mud.

[0067] The results are as follows Figure 4 As shown in the figure, the effective arsenic content of the riverbed sediment in the construction section was 26 mg / kg. After one week of maintenance, the effective arsenic concentrations of the sediments at depths of 0-15 cm, 15-25 cm and 35-50 cm were 0.56, 0.34 and 1.22 mg / kg, respectively, and the passivation rates were 97.9%, 98.7% and 95.4%, respectively. The effective arsenic concentration of the sediments at the surface layer of 0-15 cm and 35-50 cm remained stable for 4 months, but the effective arsenic concentration of the sediments at the depth of 35-50 cm was slightly higher than that of the surface layer of 0-15 cm. In addition, the effective arsenic concentration of the sediments at 15-25 cm increased to 1.5 mg / kg in the second month, but did not continue to increase in the following two months and remained stable. The reason may be that the deeper the riverbed, the more anaerobic the sediments are, the stronger the reducibility is, and the slightly destructive effect is on the Schmidt mineral, thus affecting the adsorption and fixation of arsenic.

[0068] In summary, the present invention continuously stabilizes arsenic in the sediment through the schrenckite mineral to prevent it from being released into the water body, and fixes the mixture of the schrenckite mineral and the sediment on the riverbed through a small amount of cement to avoid the loss of the schrenckite mineral during the flood season, thereby effectively improving the arsenic fixation effect.

[0069] Although the specific implementation of the present invention is described in detail in conjunction with the accompanying drawings, it should not be understood as limiting the scope of protection of this patent. Within the scope described in the claims, various modifications and variations that can be made by those skilled in the art without creative work still fall within the scope of protection of this patent.

Claims

1. A solidifying agent for fixing arsenic in riverbed mud, characterized in that: The method comprises a Schmidtite mineral and cement, wherein the amount of the Schmidtite mineral added is 0.5%-5% of the mass of the riverbed mud, and the amount of the cement added is 3%-20% of the mass of the riverbed mud.

2. The curing agent according to claim 1, characterized in that It also includes water, and the added amount of water is water: Schroeder mineral+cement (v:w)=(0.3-0.5):

1.

3. The curing agent according to claim 1, characterized in that The specific surface area of ​​the Schmidtite mineral is greater than 200m 2 / g.

4. The curing agent according to claim 1, characterized in that The cement is silicate cement.

5. A method for fixing arsenic in river sediment, characterized in that: Using the curing agent as described in any one of claims 1 to 4, it specifically comprises the following steps: Mix the curing agent evenly to form a curing slurry, and add it into the riverbed mud and mix evenly.

6. The method for fixing arsenic in riverbed mud according to claim 5, characterized in that: The schist mineral, cement and water are mixed to form a solidified slurry, which is then injected into the bottom mud through a slurry pipe. The bottom mud is stirred and turned at the same time to make the solidified slurry evenly distributed in the bottom mud.

7. The method for fixing arsenic in riverbed mud according to claim 6, characterized in that: The grouting flow rate of the solidifying slurry is 20-30L / min.

8. The method for fixing arsenic in riverbed mud according to claim 6, characterized in that: Before mixing the curing agent with the riverbed mud, the following steps are also included: Two diversion channels were built on both sides of the river to divert the water from the river; The quality of the sediment that needs to be treated is determined based on the length, width, depth and sediment density of the river to be treated.

9. The method for fixing arsenic in riverbed mud according to claim 8, characterized in that: The length and width of the drainage channel are 2-3m.

10. The method for fixing arsenic in riverbed mud according to claim 8, characterized in that: The depth of riverbed mud is 0.5-1m.

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