An integrated dewatering and solidification agent based on fly ash for dredged sludge, its preparation method and application

Abstract

This invention discloses an integrated dewatering and solidification agent for dredged sludge based on fly ash, its preparation method, and its application. The agent is characterized by using modified fly ash as a base, tetraethyl orthosilicate and rhodamine B as grafting agents, starch-acrylonitrile graft copolymer as a dewatering agent, and cerium ammonium sulfate as an initiator. It is prepared using a combined surface modification-low-temperature calcination coating-reactive grafting method. This agent is environmentally friendly, low-cost, and can absorb and solidify water, heavy metal ions, and odorous gases in dredged sludge at room temperature, playing a crucial role in the reduction and disposal of dredged sludge, thus possessing significant economic and social benefits.

Description

Technical Field

[0001] This invention relates to an integrated agent for dewatering and solidifying fly ash-based dredged sludge, its preparation method, and its application, belonging to the fields of environmental protection materials and sludge treatment. Background Technology

[0002] With rapid urbanization and industrialization, siltation in rivers, lakes, and ports has become increasingly serious, making dredging a crucial means of maintaining water body functions. Reports indicate that approximately 1.4 billion tons of silt accumulate in reservoirs, rivers, lakes, and irrigation canals annually in my country, while 1.8 billion tons enter estuaries and the ocean, creating a substantial demand for dredging.

[0003] Dredged sludge disposal mainly includes sanitary landfill, incineration, aerobic composting, and building material utilization. The primary goals are reduction, harmlessness, stabilization, and resource recovery. Drying and solidification are essential key steps in the dredged sludge disposal process, effectively reducing moisture content and lowering transportation, storage, and subsequent treatment costs. This plays a crucial role in achieving the reduction, harmlessness, stabilization, and resource recovery of high-moisture-content waste such as dredged sludge. However, dredged sludge often exhibits high moisture content, high compressibility, low permeability, and contains heavy metals and malodorous gases. This leads to challenges in equipment drying, such as long sludge transportation distances, high investment in drying equipment, high energy consumption, and poor equipment stability. These issues make it difficult to meet the needs of my country's large-scale, widely distributed, high-moisture-content, and scattered dredged sludge production.

[0004] Furthermore, current methods for treating dredged sludge typically involve dewatering and drying followed by solidification of heavy metal ions and odorous gases. This further increases treatment costs, and both dewatering agents / technologies and solidification agents / technologies must be considered in light of cost and efficiency to promote the reduction and resource utilization of dredged sludge. Therefore, developing a highly efficient integrated dewatering and solidification agent for dredged sludge has significant scientific research value and social implications. Summary of the Invention

[0005] The purpose of this invention is to address the current situation and existing problems in the field of dredged sludge treatment, and to propose an integrated fly ash-based dewatering and solidification agent for dredged sludge. Another purpose of this invention is to provide a method for preparing the above-mentioned agent.

[0006] An integrated dewatering and solidification agent for fly ash-based dredged sludge is disclosed. This agent uses modified fly ash as a base, tetraethyl orthosilicate and rhodamine B as grafting agents, starch-acrylonitrile graft copolymer as a dewatering agent, and cerium ammonium sulfate as an initiator. It is prepared using a combined surface modification-low-temperature calcination coating-reactive grafting method. Based on the mass of the modified fly ash base, the grafting agent comprises 10%–30% by mass, the dewatering agent comprises 20%–50% by mass, and the initiator comprises 1%–10% by mass.

[0007] The above-mentioned integrated dewatering and solidification agent for fly ash-based dredged sludge comprises, based on the quality of the fly ash substrate, a grafting agent with a mass percentage of 10% to 30%, a dewatering agent with a mass percentage of 30% to 50%, and an initiator with a mass percentage of 1% to 2%.

[0008] A method for preparing an integrated dewatering and solidification agent for fly ash-based dredged sludge, the preparation method of which is as follows:

[0009] (1) Surface modification of fly ash

[0010] Fly ash is soaked in acidic and alkaline solutions and then filtered. After filtration, it is washed and dried to obtain pretreated fly ash. The pretreated fly ash is then subjected to plasma treatment to obtain modified fly ash.

[0011] (2) Rhodamine B grafting

[0012] Tetraethyl orthosilicate was added to Rhodamine B solution and mixed. Then, dilute hydrochloric acid solution was added to hydrolyze and condense tetraethyl orthosilicate to form a grafting solution. The surface-modified fly ash was placed in the grafting solution for 5-10 seconds, then filtered out and placed in an oven to dry. Finally, it was calcined to form a mixed substrate.

[0013] (3) Integrated pharmaceutical preparation

[0014] After heating and cooling, cerium ammonium sulfate, acrylonitrile monomer and the mixed substrate prepared in step (2) are added to the starch slurry. After mixing, the mixture is reacted. After the reaction is completed, acetone is added and stirring is continued. Finally, after standing for 2-4 hours, the mixture is filtered and dried to obtain the fly ash-based integrated agent for dewatering and solidifying dredged sludge.

[0015] In the above preparation method: the dilute hydrochloric acid solution mentioned in step (1) is a hydrochloric acid solution with a mass fraction of 3% to 7%, and the sodium hydroxide solution has a mass fraction of 1% to 10%; the soaking time is 4 to 8 hours; the drying temperature is 80 to 100°C, and the drying time is 6 to 12 hours.

[0016] In the above preparation method: the plasma surface treatment instrument mentioned in step (1) is a Plasma clean-PL–5010 type, the input voltage during surface treatment is 220V, the working distance is 5 to 12mm, the treatment atmosphere is oxygen, and the plasma flame scanning rate is 20 to 100mm / s.

[0017] In the above preparation method: the mass ratio of Rhodamine B and tetraethyl orthosilicate in step (2) is 1:(0.1-0.2); the dilute hydrochloric acid solution is a hydrochloric acid solution with a mass fraction of 3%-7%, and the mass ratio of tetraethyl orthosilicate to dilute hydrochloric acid solution is 1:(50-100).

[0018] In the above preparation method: the drying temperature in step (2) is 25-40℃ and the drying time is 3-6 hours; the calcination temperature is 160-200℃ and the calcination time is 2-4 hours.

[0019] In the above preparation method: in step (3), the mass concentration of starch slurry is 1-10%, and the mass ratio of starch slurry to acrylonitrile is 3-8:1.

[0020] In the above preparation method: in step (3), the starch is heated to 85-95℃ for 2-4 hours and then cooled to room temperature; the reaction temperature is 20-40℃ for 2-4 hours; the drying temperature is 40-60℃ for 6-12 hours.

[0021] The present invention relates to the application of the agent in the field of dredging sludge dewatering and volume reduction.

[0022] Performance conditions and results of the present invention: Take 100g of soil slurry (wherein, the mass concentration of soil is 40% and the mass concentration of ZnCl2 is 0.1%), add 10g of integrated reagent, stir for 3min until the reagent absorbs the water in the slurry, then take 10g of moist soil and place it in 100g of deionized water and stir for 1h to form purified soil slurry. Then, use inductively coupled plasma mass spectrometry to determine the Zn content in the purified soil slurry. 2+ Zn concentration is thus used to calculate 2+ To determine the solidification and removal rate, 10g of damp soil was placed in an oven at 100℃ for 10 hours and dried. The moisture content of the damp soil was then calculated, and the dehydration rate of the agent on the soil slurry was calculated based on the moisture content. The agent was applied at room temperature and pressure, and Zn... 2+ The solidification and removal rate reaches 98%, and the soil slurry dewatering rate can reach 95%.

[0023] Beneficial effects:

[0024] The agent prepared in this invention can efficiently remove water and heavy metal ions from dredged sludge, achieving sludge reduction and heavy metal ion solidification. Compared with existing technologies, this agent uses modified fly ash as a base, which can utilize the high water absorption and high porosity of fly ash to quickly adsorb water molecules and heavy metal ions, achieve high-value-added resource utilization of low-value fly ash, and reduce agent costs. Using starch-acrylonitrile graft copolymer as a dehydrating agent, it can not only absorb water by forming hydrogen bonds with water molecules using the large number of hydroxyl groups in starch, but also adsorb and store large amounts of water using the three-dimensional network structure formed by the starch-acrylonitrile graft copolymer swelling in water. Furthermore, after swelling in water, the internal ion concentration of the starch-acrylonitrile graft copolymer is higher than that of the external solution, generating osmotic pressure that further drives water molecules into the network structure. Finally, the hydrophilic groups such as carboxyl groups of the starch-acrylonitrile graft copolymer ionize in water to generate charged ions, which can inhibit the separation of water molecules and heavy metal ions. Internally, because fly ash is inorganic while starch-acrylonitrile graft copolymer is organic, conventional methods make it difficult for the starch-acrylonitrile graft copolymer to grow on the surface and inside the pores of fly ash. Therefore, tetraethyl orthosilicate and rhodamine B are used as grafting agents. The hydrolysis and condensation of tetraethyl orthosilicate solidifies rhodamine B, thereby coupling tetraethyl orthosilicate and rhodamine B to form a film on the surface and inside the pores of the modified fly ash substrate. The modified fly ash substrate and the starch-acrylonitrile graft copolymer are grafted using the film, achieving a highly efficient synergistic effect between the starch-acrylonitrile graft copolymer and the modified fly ash substrate. During the formation of the film solution with rhodamine B, dilute hydrochloric acid solution is used to promote the hydrolysis and condensation of tetraethyl orthosilicate and form linear or branched polymers. Thus, the film solution of tetraethyl orthosilicate and rhodamine B not only involves physical coating but also chemical bonding. Therefore, the agent of the present invention can adsorb and remove water and heavy metal ions in dredged sludge at room temperature and solidify it, avoiding the precipitation of heavy metal ions, and finally achieving the drying, solidification and volume reduction of dredged sludge. Moreover, the agent components are environmentally friendly, the preparation process is simple, the cost is low, the cost performance is high, and it has strong application and promotion value. Detailed Implementation

[0025] The present invention will be further described below with reference to embodiments, but the scope of protection of the present invention is not limited thereto: Embodiment 1

[0026] (1) Surface modification of fly ash

[0027] Weigh 20.000g of fly ash and add 400.000g of deionized water and 40.000g of 3% hydrochloric acid solution. Soak for 8 hours, let stand, and then filter. Add 400.000g of deionized water and 20.000g of sodium hydroxide and soak for 8 hours. Let stand and then filter. Add 1000.000g of deionized water and wash three times. Filter and place in an oven at 80℃ for 12 hours to obtain acid-alkali washed fly ash. Then measure 2mL of acid-alkali washed fly ash and place it in a plasma surface treatment instrument (Plasma clean-PL–5010 type, the same below). First, evacuate the plasma surface treatment instrument, then fill it with 40mL of oxygen. Then, perform surface treatment under the conditions of input voltage of 220V, working distance of 5mm, and plasma flame scanning rate of 20mm / s to obtain surface-modified fly ash. Repeat the plasma surface modification steps until the acid-alkali washed fly ash is used up.

[0028] (2) Rhodamine B grafting

[0029] Weigh 0.909g of Rhodamine B and dissolve it in 27.270g of ethanol to form a Rhodamine B solution. Then weigh 0.091g of tetraethyl orthosilicate and add it to the Rhodamine B solution. Place the mixed solution on a magnetic stirrer and stir at 25°C for 4 hours. Then add 9.100g of 3% dilute hydrochloric acid solution to hydrolyze and condense the tetraethyl orthosilicate to form a grafting solution. Weigh 10.000g of the surface-modified fly ash obtained in step (1) and place it in the grafting solution for 5 seconds. Then filter it out and place it in an oven at 25°C for 6 hours. Repeat the process of placing the surface-modified fly ash in the grafting solution and drying it until the grafting solution is consumed. Finally, place it in a muffle furnace and calcine at 160°C for 4 hours to form a mixed substrate.

[0030] (3) Integrated pharmaceutical preparation

[0031] Weigh 0.500g of starch and add 10g of deionized water to form a starch slurry. Heat in a water bath at 85℃ for 4 hours and then cool to room temperature. Then add 0.100g of cerium ammonium sulfate, 2.500g of acrylonitrile monomer and 10.000g of the mixed substrate prepared in step (2). Place the mixed slurry on a magnetic heating stirrer and heat in a water bath at 20℃ for 4 hours. After the reaction is complete, add 15.000g of acetone and continue stirring. Finally, let it stand for 2 hours and then filter it. Dry it in an oven at 40℃ for 12 hours to obtain an integrated agent for dewatering and solidifying fly ash-based dredging sludge.

[0032] (4) Performance evaluation test

[0033] Take 100g of soil slurry (where the mass concentration of soil is 40% and the mass concentration of ZnCl2 is 0.1%), add 10g of integrated reagent, stir for 3 minutes until the reagent absorbs the water in the slurry, then take 10g of moist soil and place it in 100g of deionized water and stir for 1 hour to form purified soil slurry. Then, use inductively coupled plasma mass spectrometry to determine the Zn content in the purified soil slurry. 2+ Zn concentration is thus used to calculate 2+ To determine the solidification and removal rate, 10g of damp soil was placed in an oven at 100℃ for 10 hours and dried. The moisture content of the damp soil was then calculated, and the dehydration rate of the agent on the soil slurry was calculated based on the moisture content. The agent was applied at room temperature and pressure, and Zn... 2+ The solidification and removal rate reached 98.8%, and the soil slurry dewatering rate reached 95.6%.

[0034] Example 2:

[0035] (1) Surface modification of fly ash

[0036] Weigh 20.000g of fly ash and add 800.000g of deionized water and 60.000g of 7% hydrochloric acid solution. Soak for 4 hours, let stand, and then filter. Add 800.000g of deionized water and 40.000g of sodium hydroxide and soak for 4 hours. Let stand and then filter. Add 1600.000g of deionized water and wash three times. Filter and place in an oven at 100℃ for 6 hours to obtain acid-alkali washed fly ash. Then measure 2mL of acid-alkali washed fly ash and place it in a plasma surface treatment instrument. First, evacuate the plasma surface treatment instrument, then fill it with 80mL of oxygen. Then, perform surface treatment under the conditions of input voltage of 220V, working distance of 12mm, and plasma flame scanning rate of 100mm / s to obtain surface-modified fly ash. Repeat the plasma surface modification steps until the acid-alkali washed fly ash is used up.

[0037] (2) Rhodamine B grafting

[0038] Weigh 2.500g of Rhodamine B and dissolve it in 150.000g of ethanol to form a Rhodamine B solution. Then weigh 0.500g of tetraethyl orthosilicate and add it to the Rhodamine B solution. Place the mixed solution on a magnetic stirrer and stir at 35°C for 2 hours. Then add 25.000g of 7% dilute hydrochloric acid solution to hydrolyze and condense the tetraethyl orthosilicate to form a grafting solution. Weigh 10.000g of the surface-modified fly ash obtained in step (1) and place it in the grafting solution for 10 seconds. Then filter it and place it in an oven at 40°C for 3 hours to dry. Repeat the process of placing the surface-modified fly ash in the grafting solution and drying until the grafting solution is consumed. Finally, place it in a muffle furnace and calcine at 200°C for 2 hours to form a mixed substrate.

[0039] (3) Integrated pharmaceutical preparation

[0040] Weigh 0.455g of starch and add 18.200g of deionized water to form a starch slurry. Heat in a water bath at 95℃ for 2 hours and then cool to room temperature. Then add 0.200g of cerium ammonium sulfate, 4.545g of acrylonitrile monomer and 10.000g of the mixed substrate prepared in step (2). Place the mixed slurry on a magnetic heating stirrer and heat in a water bath at 40℃ for 2 hours. After the reaction is complete, add 27.300g of acetone and continue stirring. Finally, let stand for 4 hours and filter. Dry in an oven at 60℃ for 6 hours to obtain an integrated agent for dewatering and solidifying fly ash-based dredging sludge.

[0041] (4) Performance evaluation test

[0042] Take 100g of soil slurry (where the mass concentration of soil is 40% and the mass concentration of ZnCl2 is 0.1%), add 10g of integrated reagent, stir for 3 minutes until the reagent absorbs the water in the slurry, then take 10g of moist soil and place it in 100g of deionized water and stir for 1 hour to form purified soil slurry. Then, use inductively coupled plasma mass spectrometry to determine the Zn content in the purified soil slurry. 2+ Zn concentration is thus used to calculate 2+ To determine the solidification and removal rate, 10g of damp soil was placed in an oven at 100℃ for 10 hours and dried. The moisture content of the damp soil was then calculated, and the dehydration rate of the agent on the soil slurry was calculated based on the moisture content. The agent was applied at room temperature and pressure, and Zn... 2+ The solidification and removal rate reached 98.2%, and the soil slurry dewatering rate reached 98.3%.

[0043] Comparative Example 1

[0044] (1) Pharmaceutical preparation

[0045] Except that fly ash is not used as a base in the preparation of the reagent, the other conditions are the same as in Example 1;

[0046] (2) Performance evaluation test

[0047] Take 100g of soil slurry (where the mass concentration of soil is 40% and the mass concentration of ZnCl2 is 0.1%), add 10g of integrated reagent, stir for 3 minutes until the reagent absorbs the water in the slurry, then take 10g of moist soil and place it in 100g of deionized water and stir for 1 hour to form purified soil slurry. Then, use inductively coupled plasma mass spectrometry to determine the Zn content in the purified soil slurry. 2+ Zn concentration is thus used to calculate 2+ To determine the solidification and removal rate, 10g of damp soil was placed in an oven at 100℃ for 10 hours and dried. The moisture content of the damp soil was then calculated, and the dehydration rate of the agent on the soil slurry was calculated based on the moisture content. The agent was applied at room temperature and pressure, and Zn...2+ The solidification and removal rate reached 62.4%, and the soil slurry dewatering rate reached 88.1%.

[0048] (3) Comparison effect

[0049] Compared to Example 1, if fly ash is not used as a base during reagent preparation, the dehydration rate of the reagent is slightly reduced, but the Zn content is higher. 2+ The curing removal rate is significantly reduced, mainly because the starch-acrylonitrile graft copolymer is the main dehydration component in the agent, while some heavy metal ions may enter the interior of the fly ash channels. Without the fly ash substrate, the removal rate of heavy metal ions will be significantly reduced.

[0050] Comparative Example 2:

[0051] (1) Pharmaceutical preparation

[0052] Except that Rhodamine B grafting was not used in the preparation of the drug, the other conditions were the same as in Example 2;

[0053] (2) Comparison effect

[0054] Compared to Example 2, if Rhodamine B grafting is not used during reagent preparation, the starch-acrylonitrile graft copolymer and fly ash will exhibit stratification, meaning that the starch-acrylonitrile graft copolymer does not grow on the fly ash mixed substrate. This will cause physical stratification of the reagent during transportation and use, making it impossible to accurately weigh the reagent and determine the reagent usage ratio, thereby affecting the effectiveness of the application.

Claims

1. A fly ash-based dewatering and solidifying integrated agent for dredged sludge, characterized by: This agent uses modified fly ash as a base, tetraethyl orthosilicate and rhodamine B as grafting agents, starch-acrylonitrile graft copolymer as a dehydrating agent, and cerium ammonium sulfate as an initiator. It is prepared by a combined method of surface modification-low temperature calcination coating-reaction grafting. Based on the mass of the modified fly ash base, the mass percentage of grafting agent is 10%~30%, the mass percentage of dehydrating agent is 20%~50%, and the mass percentage of initiator is 1%~10%. The preparation method of this drug is as follows: (1) Surface modification of fly ash Fly ash is soaked in acidic and alkaline solutions and then filtered. After filtration, it is washed and dried to obtain pretreated fly ash. The pretreated fly ash is then subjected to plasma treatment to obtain modified fly ash. (2) Rhodamine B graft Tetraethyl orthosilicate was added to Rhodamine B solution and mixed. Then, dilute hydrochloric acid solution was added to hydrolyze and condense tetraethyl orthosilicate to form a grafting solution. The surface-modified fly ash was placed in the grafting solution for 5-10 seconds, then filtered out and placed in an oven to dry. Finally, it was calcined to form a mixed substrate. (3) Integrated pharmaceutical preparation After heating and cooling, cerium ammonium sulfate, acrylonitrile monomer and the mixed substrate prepared in step (2) are added to the starch slurry. After mixing, the mixture is reacted. After the reaction is completed, acetone is added and stirring is continued. Finally, after standing for 2-4 hours, the mixture is filtered and dried to obtain the fly ash-based integrated agent for dewatering and solidifying dredged sludge.

2. The integrated dewatering and solidification agent for fly ash-based dredged sludge according to claim 1, characterized in that: Based on the quality of fly ash substrate, the grafting agent has a mass percentage of 10% to 30%, the dehydrating agent has a mass percentage of 30% to 50%, and the initiator has a mass percentage of 1% to 2%.

3. The preparation method of the fly ash-based integrated dewatering and solidification agent for dredged sludge as described in claim 1, characterized in that: The preparation method of this drug is as follows: (1) Surface modification of fly ash Fly ash is soaked in acidic and alkaline solutions and then filtered. After filtration, it is washed and dried to obtain pretreated fly ash. The pretreated fly ash is then subjected to plasma treatment to obtain modified fly ash. (2) Rhodamine B graft Tetraethyl orthosilicate was added to Rhodamine B solution and mixed. Then, dilute hydrochloric acid solution was added to hydrolyze and condense tetraethyl orthosilicate to form a grafting solution. The surface-modified fly ash was placed in the grafting solution for 5-10 seconds, then filtered out and placed in an oven to dry. Finally, it was calcined to form a mixed substrate. (3) Integrated pharmaceutical preparation After heating and cooling, cerium ammonium sulfate, acrylonitrile monomer and the mixed substrate prepared in step (2) are added to the starch slurry. After mixing, the mixture is reacted. After the reaction is completed, acetone is added and stirring is continued. Finally, after standing for 2-4 hours, the mixture is filtered and dried to obtain the fly ash-based integrated agent for dewatering and solidifying dredged sludge.

4. The preparation method according to claim 3, characterized in that: In step (1), the acidic solution is a hydrochloric acid solution with a mass fraction of 3% to 7%, and the alkaline solution is a sodium hydroxide solution with a mass fraction of 1% to 10%. The soaking time is 4 to 8 hours. The drying temperature is 80 to 100°C, and the drying time is 6 to 12 hours.

5. The preparation method according to claim 3, characterized in that: In step (1), the plasma treatment instrument is a Plasma Clean-PL-5010 model. The input voltage during surface treatment is 220V, the working distance is 5~12mm, the treatment atmosphere is oxygen, and the plasma flame scanning rate is 20~100 mm / s.

6. The preparation method according to claim 3, characterized in that: In step (2), the mass ratio of Rhodamine B to tetraethyl orthosilicate is 1:(0.1~0.2); the dilute hydrochloric acid solution is a hydrochloric acid solution with a mass fraction of 3%~7%, and the mass ratio of tetraethyl orthosilicate to dilute hydrochloric acid solution is 1:(50~100).

7. The preparation method according to claim 3, characterized in that: The drying temperature in step (2) is 25~40℃ and the drying time is 3~6 hours; the calcination temperature is 160~200℃ and the calcination time is 2~4 hours.

8. The preparation method according to claim 3, characterized in that: In step (3), the mass concentration of starch slurry is 1-10%, and the mass ratio of starch slurry to acrylonitrile is 3-8:

1.

9. The preparation method according to claim 3, characterized in that: In step (3), the starch is heated to 85~95℃ for 2~4h and then cooled to room temperature; the reaction temperature is 20~40℃ for 2~4h; the drying temperature is 40~60℃ for 6~12h.

10. The application of the agent according to claim 1 in the field of dredging sludge dewatering and volume reduction.