A drying agent for high-moisture, high-salinity, and high-organic-matter sludge, its preparation method, and its application.

Abstract

This invention relates to the field of sludge treatment technology, and in particular to a specialized drying agent for sludge with high water content, high salinity, and high organic matter content, its preparation method, and its application. The drying agent, by weight, comprises 7-25 parts quicklime, 10-50 parts mineral powder, 1-10 parts desulfurized gypsum, 1-5 parts anhydrous sodium sulfate, and 2-12 parts sulfonated iron salt-modified activated carbon. This invention, through the synergistic effect of multiple components, overcomes the limitations of a single inorganic cementitious substrate, effectively reducing the water content of sludge and weakening the migration of organic matter and salt ions. It effectively solves the technical problems of existing sludge solidification technologies, such as poor treatment effect and inability to achieve efficient resource utilization for sludge with high water content, high salinity, and high organic matter content.

Description

Technical Field

[0001] This invention relates to the field of sludge treatment technology, and in particular to a special drying agent for sludge with high water content, high salinity, and high organic matter content, as well as its preparation method and application. Background Technology

[0002] Composite sludge characterized by high water content, high salinity, and high organic matter exhibits three distinct "high" characteristics: water content reaches 50-75%, exhibiting a fluid or even liquid state with virtually no load-bearing capacity, making direct stockpiling or transportation difficult; salt ion conductivity EC ≥ 8 mS / cm, indicating significant salinization; and organic matter content is 12-20%, mostly plant and animal humus, easily decomposing and emitting foul odors, and slowly releasing corrosive substances such as organic acids. These combined "high" characteristics make conventional treatment technologies unsuitable, necessitating the development of targeted solidification technologies to achieve sludge reduction, harmlessness, and resource utilization.

[0003] Among common sludge treatment methods, landfilling requires the occupation of a large amount of valuable arable land or landfill resources, and the salt and pollutants in the sludge are easily seeped in by rainwater, inducing long-term pollution of groundwater and soil. Incineration can achieve the goal of volume reduction, but it requires pre-dehydration and drying of the sludge, resulting in high overall energy consumption. During the incineration process, it releases strong carcinogens such as dioxins, and the cost of exhaust gas treatment is extremely high, making it difficult to meet the requirements of current environmental protection policies. In terms of resource utilization, the "three highs" characteristics of sludge severely restrict the application of conventional solidification technologies. Excessive salt ions in a high-salt environment will seriously interfere with the cement hydration reaction, not only weakening the strength of the dried body and causing secondary mudification, but also inhibiting the hydration reaction of cementitious materials when used as roadbed materials, resulting in a decrease in the strength of the dried body. At the same time, the chemical reaction between salt ions and hydration products will generate expansive substances, causing the dried body to crack and break. In addition, high organic matter content hinders the aggregation and coagulation of hydration products due to the negative charge carried on its surface, and the organic acids produced by its decomposition lower the pH value of the system, inhibiting the formation and development of the gel network.

[0004] Therefore, developing a specialized drying agent that can synergistically solve the problems of high water content, high salinity, and high organic matter, and achieve efficient reduction, harmlessness, and resource utilization of sludge, has become an urgent technical need in this field. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a drying agent, its preparation method, and its application for efficiently treating sludge with high water content, high salinity, and high organic matter. This drying agent, through the synergistic effect of multiple components, achieves rapid dehydration, salt fixation, and reduction of organic matter, while also increasing the strength of the dried body. It effectively solves the technical problems of existing sludge solidification technologies, such as poor treatment effects on sludge with these "three high" characteristics and the inability to achieve efficient resource utilization.

[0006] To achieve the above-mentioned technical objectives, the present invention adopts the following technical solution:

[0007] One technical solution of the present invention provides a drying agent for sludge with high water content, high salinity, and high organic matter content, wherein the raw materials, by weight, include:

[0008] 7-25 parts quicklime, 10-50 parts mineral powder, 1-10 parts desulfurized gypsum, 1-5 parts anhydrous sodium sulfate, and 2-12 parts sulfonated iron salt double-modified activated carbon.

[0009] In some possible implementations, the raw materials, by weight, include:

[0010] 7-25 parts quicklime, 13-50 parts mineral powder, 2-10 parts sulfur gypsum, 1-5 parts anhydrous sodium sulfate, 3-10 parts sulfonated iron salt double-modified activated carbon.

[0011] In some possible implementations, the sulfonated iron salt double-modified activated carbon accounts for 4-18% of the total mass of the drying agent.

[0012] Furthermore, the sulfonated iron salt double-modified activated carbon accounts for 9-13% of the total mass of the drying agent.

[0013] Furthermore, the mass ratio of sulfonated iron salt-modified activated carbon to mineral powder is (0.2-0.3):1.

[0014] In this invention, when the mass ratio of sulfonated iron salt-modified activated carbon to mineral powder is below 0.2 or above 0.3, the dehydration effect of the drying agent is not ideal. The possible reasons are as follows:

[0015] When the mass ratio of sulfonated iron salt-modified activated carbon to mineral powder is less than 0.2, the iron salt (FeCl3) The catalytic effect of Fe(OH)3 colloids formed in an alkaline environment is significantly weakened, which delays the secondary hydration reaction of mineral powder and inhibits the early formation of ettringite. At the same time, insufficient activated carbon cannot provide enough nucleation sites, making it difficult for ettringite to anchor, weakening the strength of the dried body, causing local blockage of its pore channels to hinder water evaporation, and delaying the decrease in the moisture content of the dried body.

[0016] When the mass ratio of sulfonated iron salt-modified activated carbon to mineral powder is higher than 0.3, the excessive amount of modified activated carbon particles cannot be fully encapsulated by hydration products, weakening the strength of the interfacial transition zone between activated carbon and cementitious material matrix; at the same time, the cementitious material matrix is ​​diluted, resulting in insufficient C-(A)-SH gel formation, making it difficult to maintain smooth pore drainage, and ultimately delaying the change in moisture content of the early dried body.

[0017] In some possible implementations, the sulfonated iron salt-modified activated carbon in the above scheme is prepared by the following method:

[0018] (1) Iron salt modification:

[0019] Pretreated activated carbon was added to an iron salt solution and stirred at room temperature. After filtration, washing, and drying, it was placed in a nitrogen-atmosphere tube furnace for calcination and cooled to room temperature to obtain iron salt modified biochar.

[0020] (2) Sulfonation modification:

[0021] Under ice-water bath conditions, iron salt modified biochar is added to concentrated sulfuric acid and mixed evenly. The mixture is heated and stirred. After the reaction is completed, the reaction solution is poured into ice water, filtered, washed until the pH of the filtrate is 3.0-4.0, dried, and ground to obtain sulfonated iron salt double-modified activated carbon.

[0022] In some possible implementations, the pretreatment step of activated carbon in step (1) above is as follows:

[0023] At room temperature, activated carbon that has passed through an 80-100 mesh standard sieve is added to a hydrochloric acid solution with a concentration of 0.8-1.2 mol / L, with a solid-liquid ratio of 1:(15-25) (in g / mL). The inorganic ash in the activated carbon is fully dissolved through an acid-base neutralization reaction. The mixture is then magnetically or mechanically stirred for 2-3 hours, filtered, and washed with deionized water until the pH of the filtrate is 6.5-7.0. Finally, it is dried to constant weight to obtain pretreated activated carbon.

[0024] For example, activated carbon can be sieved through 80-mesh, 90-mesh, or 100-mesh sieves; the concentration of hydrochloric acid solution can be selected as 0.8 mol / L, 1 mol / L, or 1.2 mol / L; the stirring time can be selected as 2 h, 2.5 h, or 3 h; and the solid-liquid ratio of activated carbon to hydrochloric acid solution can be selected as 1:15, 1:20, or 1:25.

[0025] In some possible implementations, in step (1) of iron salt modification above:

[0026] The iron salt solution used was FeCl3 with a concentration of 0.8-1.2 mol / L. The solid-liquid ratio of the pretreated activated carbon to the iron salt solution is 1:(10-20) (in g / mL). The stirring time is 4-8 h, and the stirring method is magnetic stirring or mechanical stirring to control the degree of adsorption and complexation of iron ions on the surface of biochar. The drying temperature is 60-80℃ and the drying time is 6-10 h. During calcination, the temperature is increased from room temperature to 360-400℃ at a rate of 3-8℃ / min and then calcined for 2-3 h. This ensures that the iron component is converted into highly active amorphous iron oxide, and at the same time adapts to the reactivity of different batches of raw materials, ensuring that the iron salt forms catalytic active sites through adsorption, complexation and high-temperature immobilization.

[0027] For example, FeCl3 The concentration of the 6H₂O aqueous solution is 0.8 mol / L, 1 mol / L, or 1.2 mol / L; the solid-liquid ratio of the pretreated activated carbon to the iron salt solution can be selected as 1:10, 1:15, or 1:20; the stirring time can be 4 h, 6 h, or 8 h; the drying temperature is 60℃, 65℃, 70℃, 75℃, or 80℃, and the drying time is 6 h, 7 h, 8 h, 9 h, or 10 h; the heating rate during calcination is 3℃ / min, 5℃ / min, or 8℃ / min, the calcination temperature is 360℃, 370℃, 380℃, 390℃, or 400℃, and the calcination time is 2 h, 2.5 h, or 3 h. 。

[0028] In some possible implementations, in step (2) of the above sulfonation modification:

[0029] The temperature of the ice-water bath is controlled at 0-5℃, and the mass concentration of concentrated sulfuric acid is 93-98%. Concentrated sulfuric acid can provide sufficient electrophilic particles (such as HSO3). + The core sulfonation mechanism of introducing SO3H by electrophilic substitution of Fe-BC aromatic ring is satisfied. The mass ratio of iron salt modified biochar to concentrated sulfuric acid is 1:(6-10); the reaction temperature is 70-80℃ and the reaction time is 3-5h.

[0030] After the reaction is complete, the reaction solution is slowly poured into rapidly stirred ice water for quenching, filtered, and the filter residue is washed with deionized water until the pH of the filtrate is 3.0-4.0. Then it is dried to constant weight, and finally ground and sieved to obtain sulfonated iron salt double-modified activated carbon.

[0031] For example, the mass ratio of iron-modified biochar to concentrated sulfuric acid is 1:6, 1:8, or 1:10; the reaction temperature is 70℃, 75℃, or 80℃; and the reaction time is 3h, 4h, or 5h. This ensures the efficient electrophilic substitution sulfonation reaction while avoiding high temperature damage to the porous structure of biochar and the activity of iron components. The 3-5h reaction time can precisely control the grafting density and uniformity of sulfonic acid groups on the Fe-BC surface. All of these are consistent with the core sulfonation mechanism of concentrated sulfuric acid electrophilic substitution of aromatic rings in biochar to introduce -SO3H groups, thus ensuring the loading effect of functional groups.

[0032] In some possible implementations, the drying temperature in step (2) of the above-mentioned sulfonation modification is 60-80℃, and the drying time is changed to 10-14h. Under these drying conditions, the residual moisture in S-Fe-BC can be removed by gentle drying, and the active sites of sulfonic acid groups (-SO3H) and amorphous iron oxides on its surface can be preserved. After grinding, the activated carbon is passed through a 60-100 mesh sieve to obtain sulfonated iron salt double-modified activated carbon.

[0033] For example, the drying temperature in the above sulfonation modification is 60°C, 70°C or 80°C, the drying time is 10h, 12h or 14h, and the sieve after grinding can be a 60 mesh, 80 mesh or 100 mesh standard sieve.

[0034] The present invention also provides a method for preparing a drying agent for high-moisture, high-salinity, and high-organic-matter sludge as described in any of the above schemes, comprising:

[0035] The quicklime, mineral powder, desulfurized gypsum, anhydrous sodium sulfate, and sulfonated iron salt double-modified activated carbon are mixed evenly, dried, and sieved to obtain the drying agent.

[0036] In some possible implementations, the specific steps of preparing a drying agent for high-moisture, high-salinity, and high-organic-matter sludge include:

[0037] (a) Add quicklime, mineral powder, desulfurized gypsum and anhydrous sodium sulfate to a mixer and mix at a speed of 25~30 r / min for 15~20 min to obtain inorganic cementitious base material;

[0038] (b) Add sulfonated iron salt double-modified activated carbon to the inorganic cementitious base obtained in step (a) and mix at a speed of 20~25 r / min for 20~25 min to obtain a mixture;

[0039] (c) Dry the mixture obtained in step (b) at 60~80℃ for 1~2h, and control the moisture content to ≤2%;

[0040] (d) Pass the dried material through a 100-mesh sieve. The material passing through the sieve is the finished drying agent.

[0041] For example, in step (a), the mixer speed can be selected as 25, 28 or 30 r / min, and the mixing time can be 15, 18 or 20 min.

[0042] For example, in step (b), the rotation speed can be selected as 20, 23 or 25 r / min, and the stirring time can be 20, 23 or 25 min.

[0043] For example, in step (c), the drying temperature can be selected as 60°C, 65°C, 70°C, 75°C or 80°C, and the drying time can be selected as 1, 1.5 or 2 hours.

[0044] The present invention also provides a drying agent for high-moisture, high-salt, and high-organic-matter sludge using any of the above-mentioned methods, or a drying agent prepared using any of the above-mentioned methods for preparing a drying agent for high-moisture, high-salt, and high-organic-matter sludge, which is applied to treat high-moisture, high-salt, and high-organic-matter sludge. The amount of sludge drying agent added is 4-10 wt% of the total mass of the sludge to be treated. The moisture content of the high-moisture, high-salt, and high-organic-matter sludge is 50-75%, the salt ion conductivity EC≥8mS / cm, and the organic matter content is 12-20%.

[0045] The drying agent in this invention achieves highly efficient treatment of "three-high" sludge through the synergistic effect of its components. The possible mechanism is analyzed as follows:

[0046] Quicklime can rapidly reduce the water content of silt with high water content through physical water absorption and heat release during hydration; its strong alkalinity can destroy the stable structure of organic colloids such as humic acid, release the bound water they contain, and initially reduce the interference of salt ions on the gel reaction through ion exchange.

[0047] Mineral powder: Under the alkaline activation of quicklime, it can generate calcium silicate hydrate (CSH) and calcium aluminate hydrate (CAH) gels, which fill the pores of silt, further reducing water retention and dissolving Na+. + Cl - Salt ions are "locked" inside the gel, reducing their migration and corrosiveness.

[0048] Desulfurized gypsum: used to provide SO4 2- It reacts with the hydration products of mineral powder to form ettringite (3CaO·Al2O3·3CaSO4·32H2O), accelerating early strength development; at the same time, SO4 2- Can be with Cl - Competitive adsorption sites reduce Cl - It enhances the salt resistance of CSH gel Si-O-Al by resisting its erosion.

[0049] Anhydrous sodium sulfate: can destroy the organic adsorption film on the surface of sludge particles, and improve the interfacial bonding force between cementing materials and sludge particles.

[0050] Sulfonated iron salt-modified activated carbon: Utilizing the high specific surface area of ​​the activated carbon matrix to adsorb high levels of organic matter and salt ions, it can reduce the encapsulation of cementitious particles by organic matter and improve sludge treatment efficiency; after modification with iron salts, the introduced Fe... 3+Fe(OH)3 colloid is generated in an alkaline system. This colloid has strong adsorption properties and can effectively adsorb and fix organic matter and salt ions in the system, reducing their mobility. At the same time, Fe(OH)3 can assist in catalyzing the depolymerization of mineral powder glass, promote gelation reaction, optimize pore structure, facilitate the dehydration of sludge particles, and reduce water content. After sulfonation modification, the grafted sulfonic acid groups can significantly improve the hydrophilicity of activated carbon, enhance its dispersibility and compatibility in the sludge-cementation system, and thus better synergize with other components.

[0051] The present invention has the following beneficial effects:

[0052] (1) The present invention utilizes quicklime, mineral powder, desulfurized gypsum, anhydrous sodium sulfate, and sulfonated iron salt to prepare a sludge drying agent. This drying agent breaks through the limitations of a single inorganic cementitious substrate and effectively reduces the water content of sludge and weakens the migration of organic matter and salt ions through the synergistic effect of multiple mechanisms such as physicochemical modification, adsorption fixation and cementation solidification.

[0053] (2) This invention introduces sulfonated iron salt-modified activated carbon, which combines adsorption, chemical consolidation, and catalytic activation effects. 3+ Fe(OH)3 colloids can be generated in the system. Fe(OH)3 colloids have strong adsorption properties and can effectively adsorb organic matter and salt ions in the system, reducing their mobility. At the same time, Fe(OH)3 can also help catalyze the deagglomeration of mineral powder glass, promote gelation, optimize pore structure, and facilitate the dehydration of sludge particles, reducing water content.

[0054] (3) The present invention uses sulfonic acid groups to graft activated carbon, which can improve its hydrophilicity and compatibility in the system, thereby synergistically treating sludge better with other components.

[0055] (4) The preparation method of the drying agent of the present invention is simple, the raw materials are readily available, the cost is low, and it is easy to industrialize. The treated sludge has significant advantages in terms of volume reduction, harmlessness and resource utilization. Detailed Implementation

[0056] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Although the description of the present invention will be presented in conjunction with preferred embodiments, this does not mean that the features of the invention are limited to these embodiments.

[0057] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below. Unless otherwise specified, the raw materials used in the following embodiments are all commercially available products.

[0058] Example 1

[0059] The drying agent for high-moisture, high-salinity, and high-organic-matter sludge provided in this embodiment comprises, by weight, the following raw materials:

[0060] 15 parts quicklime, 29 parts mineral powder, 6 parts desulfurized gypsum, 3 parts anhydrous sodium sulfate, and 6.5 parts sulfonated iron salt double-modified activated carbon.

[0061] Among them, sulfonated iron salt double-modified activated carbon accounts for 10.92% of the total mass of the drying agent, and the mass ratio of sulfonated iron salt double-modified activated carbon to mineral powder is 0.22:1.

[0062] The above-mentioned sulfonated iron salt-modified activated carbon is prepared by the following method:

[0063] (1) Pre-treated activated carbon:

[0064] At room temperature, activated carbon that has passed through a 100-mesh standard sieve is added to a 1 mol / L hydrochloric acid solution with a solid-liquid ratio of 1:20 (g / mL). The mixture is magnetically stirred for 2.5 h, filtered, and washed with deionized water until the pH of the filtrate is 6.5-7.0. The filtrate is then dried at 60 °C for 12 h to constant weight to obtain pretreated activated carbon.

[0065] (2) Iron salt modification:

[0066] Pretreated activated carbon was added to FeCl3 at a concentration of 1 mol / L. In an aqueous solution of iron salts (6H2O), the solid-liquid ratio of pretreated activated carbon to iron salt solution was 1:15 (g / mL). The solution was magnetically stirred at room temperature for 6 hours, filtered, washed with deionized water, dried at 70°C for 8 hours, and then placed in a tube furnace under a nitrogen atmosphere for calcination. The temperature was increased from room temperature to 380°C at a rate of 5°C / min and calcined for 2.5 hours. After cooling to room temperature, iron salt modified biochar was obtained.

[0067] (3) Sulfonation modification:

[0068] Iron-modified biochar was added to 98% concentrated sulfuric acid at a mass ratio of 1:8 under ice-water bath conditions of 0-5℃. The mixture was heated to 75℃ and stirred for 4 hours. The reaction solution was then slowly poured into rapidly stirred ice water for quenching. The mixture was filtered, and the filter residue was washed with deionized water until the pH of the filtrate was 3.0-4.0. The filtrate was then dried at 70℃ for 12 hours to constant weight. Finally, it was ground through an 80-mesh sieve to obtain sulfonated iron-modified activated carbon.

[0069] This embodiment also provides a method for preparing the above-mentioned drying agent for high moisture content, high salinity, and high organic matter sludge, the specific steps of which are as follows:

[0070] (a) Add quicklime, mineral powder, desulfurized gypsum and anhydrous sodium sulfate to a double helix cone mixer according to the above weight proportions, and mix at a speed of 30 r / min for 20 min to obtain inorganic cementitious base material;

[0071] (b) Add sulfonated iron salt double-modified activated carbon to the inorganic cementitious base obtained in step (a) and mix at a speed of 25 r / min for 25 min to obtain a mixture;

[0072] (c) Dry the mixture obtained in step (b) at 70°C for 1 hour, controlling the moisture content to be ≤2%;

[0073] (d) Pass the dried material through a 100-mesh sieve. The material passing through the sieve is the finished drying agent.

[0074] Example 2

[0075] The drying agent for high-moisture, high-salinity, and high-organic-matter sludge provided in this embodiment comprises, by weight, the following raw materials:

[0076] 7 parts quicklime, 13 parts mineral powder, 2.8 parts desulfurized gypsum, 1.4 parts anhydrous sodium sulfate, and 3.5 parts sulfonated iron salt double-modified activated carbon.

[0077] Among them, sulfonated iron salt double-modified activated carbon accounts for 12.64% of the total mass of the drying agent, the mass ratio of sulfonated iron salt double-modified activated carbon to mineral powder is 0.27:1, and the preparation method of sulfonated iron salt double-modified activated carbon is the same as in Example 1.

[0078] This embodiment also provides a method for preparing the above-mentioned drying agent for high water content, high salinity, and high organic matter sludge, with the specific steps being the same as in Embodiment 1.

[0079] Example 3

[0080] The drying agent for high-moisture, high-salinity, and high-organic-matter sludge provided in this embodiment comprises, by weight, the following raw materials:

[0081] 25 parts quicklime, 50 parts mineral powder, 10 parts desulfurized gypsum, 5 parts anhydrous sodium sulfate, and 9.8 parts sulfonated iron salt double-modified activated carbon.

[0082] Among them, sulfonated iron salt double-modified activated carbon accounts for 9.82% of the total mass of the drying agent, the mass ratio of sulfonated iron salt double-modified activated carbon to mineral powder is 0.2:1, and the preparation method of sulfonated iron salt double-modified activated carbon is the same as in Example 1.

[0083] This embodiment also provides a method for preparing the above-mentioned drying agent for high water content, high salinity, and high organic matter sludge, with the specific steps being the same as in Embodiment 1.

[0084] Example 4

[0085] The drying agent for high-moisture, high-salinity, and high-organic-matter sludge provided in this embodiment comprises, by weight, the following raw materials:

[0086] 14 parts quicklime, 28 parts mineral powder, 5 parts desulfurized gypsum, 2 parts anhydrous sodium sulfate, and 10.5 parts sulfonated iron salt double-modified activated carbon.

[0087] Among them, sulfonated iron salt double-modified activated carbon accounts for 17.65% of the total mass of the drying agent, the mass ratio of sulfonated iron salt double-modified activated carbon to mineral powder is 0.38:1, and the preparation method of sulfonated iron salt double-modified activated carbon is the same as in Example 1.

[0088] This embodiment also provides a method for preparing the above-mentioned drying agent for high water content, high salinity, and high organic matter sludge, with the specific steps being the same as in Embodiment 1.

[0089] Example 5

[0090] The drying agent for high-moisture, high-salinity, and high-organic-matter sludge provided in this embodiment comprises, by weight, the following raw materials:

[0091] 16 parts quicklime, 30 parts mineral powder, 7 parts desulfurized gypsum, 4 parts anhydrous sodium sulfate, and 2.5 parts sulfonated iron salt double-modified activated carbon.

[0092] Among them, the sulfonated iron salt double-modified activated carbon accounts for 4.2% of the total mass of the drying agent, the mass ratio of sulfonated iron salt double-modified activated carbon to mineral powder is 0.08:1, and the preparation method of sulfonated iron salt double-modified activated carbon is the same as in Example 1.

[0093] This embodiment also provides a method for preparing the above-mentioned drying agent for high water content, high salinity, and high organic matter sludge, with the specific steps being the same as in Embodiment 1.

[0094] Comparative Example 1

[0095] This comparative example provides a drying agent that differs from Example 1 in that the sulfonated iron salt double-modified activated carbon is replaced with iron salt modified biochar.

[0096] The above-mentioned iron salt modified biochar was prepared by the following method:

[0097] (1) Pre-treated activated carbon:

[0098] At room temperature, activated carbon that has passed through a 100-mesh standard sieve is added to a 1 mol / L hydrochloric acid solution with a solid-liquid ratio of 1:20 (g / mL). The mixture is magnetically stirred for 2.5 h, filtered, and washed with deionized water until the pH of the filtrate is 6.5-7.0. The filtrate is then dried at 60 °C for 12 h to constant weight to obtain pretreated activated carbon.

[0099] (2) Iron salt modification:

[0100] Pretreated activated carbon was added to FeCl3 at a concentration of 1 mol / L. In an aqueous solution of iron salts (6H2O), the solid-liquid ratio of pretreated activated carbon to iron salt solution was 1:15 (g / mL). The solution was magnetically stirred at room temperature for 6 hours, filtered, washed with deionized water, dried at 70°C for 8 hours, and then placed in a tube furnace under a nitrogen atmosphere for calcination. The temperature was increased from room temperature to 380°C at a rate of 5°C / min and calcined for 2.5 hours. After cooling to room temperature, iron salt modified biochar was obtained.

[0101] Comparative Example 2

[0102] This comparative example provides a drying agent that differs from Example 1 in that the sulfonated iron salt double-modified activated carbon is replaced with sulfonated modified biochar.

[0103] The above-mentioned sulfonated modified biochar was prepared by the following method:

[0104] (1) Pre-treated activated carbon:

[0105] At room temperature, activated carbon that has passed through a 100-mesh standard sieve is added to a 1 mol / L hydrochloric acid solution with a solid-liquid ratio of 1:20 (g / mL). The mixture is magnetically stirred for 2.5 h, filtered, and washed with deionized water until the pH of the filtrate is 6.5-7.0. The filtrate is then dried at 60 °C for 12 h to constant weight to obtain pretreated activated carbon.

[0106] (2) Sulfonation modification:

[0107] Under ice-water bath conditions of 0-5℃, pretreated activated carbon was added to concentrated sulfuric acid with a mass concentration of 98% and mixed evenly. The mass ratio of pretreated activated carbon to concentrated sulfuric acid was 1:8. The mixture was heated to 75℃ and stirred for 4 hours. The reaction solution was then slowly poured into rapidly stirred ice water for quenching. The mixture was filtered, and the filter residue was washed with deionized water until the pH of the filtrate was 3.0-4.0. The filtrate was then dried at 70℃ for 12 hours to constant weight. Finally, it was ground through an 80-mesh sieve to obtain sulfonated modified activated carbon.

[0108] Comparative Example 3

[0109] This comparative example provides a drying agent that differs from Example 1 in that:

[0110] The sulfonated iron salt double-modified activated carbon was replaced with sulfonated modified biochar and ferric chloride, with a mass ratio of sulfonated modified biochar to ferric chloride of 4:1.

[0111] The preparation method of the above-mentioned sulfonated modified biochar is the same as that of Comparative Example 2.

[0112] Performance testing

[0113] The silt sample was taken from a coastal dredging project in Fujian Province. It had a water content of 63.2%, a salt content EC≥8mS / cm, an organic matter content of 15.6%, and a fishy odor.

[0114] Add 6 wt% of the drying agent prepared in Examples 1-5 and Comparative Examples 1-3 to the sludge, mix evenly, and prepare test samples into cylinders with a height of 100 cm and a diameter of 100 cm. Use the same process to prepare sludge blocks without drying agent as a blank group. Place each block in a well-ventilated environment at a temperature of 25±2℃ and air dry for 3 days to obtain sludge products.

[0115] The moisture content, organic matter content, salt content, electrical conductivity, and dry body strength of the above-mentioned silt products were measured respectively. Among them, the moisture content was determined according to the drying method in GB / T 50123 "Standard for Geotechnical Testing Methods";

[0116] The organic matter content was determined according to HJ 76-2015 "Determination of Organic Matter in Solid Waste by Loss on Ignition Method". After curing, each sample was weighed to the same mass, and the organic matter content in the sample was determined using a muffle furnace.

[0117] Salt content and electrical conductivity were determined by extraction according to LY / T 1251-1999 "Analysis of Water-Soluble Salts in Forest Soils", and the total salt content in the leachate was determined by electrical conductivity method.

[0118] The strength of the dried body was determined according to the unconfined compressive strength test in GB / T 50123 "Standard for Geotechnical Testing Methods". The measurement results are shown in Table 1 below.

[0119] Table 1 Performance test results of sludge sample preparation

[0120]

[0121] Analysis of the data in Table 1 shows that:

[0122] The sludge samples prepared using the drying agents of Examples 1-3 of this application exhibit good performance in various aspects, with a moisture content controlled below 16.2%, an organic matter content below 6.5%, a salt ion conductivity below 3.1 mS / cm, and a dried body strength above 0.9 MPa.

[0123] Comparing Examples 1 and 4, it is evident that all performance characteristics of Example 4 have decreased. The possible reasons are as follows: Example 4 contains a high content of sulfonated iron salt-modified activated carbon, reaching 17.65%, and the mass ratio of sulfonated iron salt-modified activated carbon to mineral powder is 0.38:1. This imbalance in the ratio of sulfonated iron salt-modified activated carbon to mineral powder prevents the formation of the complete "adsorption-catalysis-gelling" pathway. Insufficient mineral powder content leads to insufficient gelling product formation, while excessive biochar content weakens adsorption and catalysis, creating a cumulative effect of weaknesses. Unadsorbed salt ions further inhibit mineral powder hydration, preventing the formation of a continuous gelling product network. Furthermore, the lack of effective support in the dried body results in minimal changes in moisture content, causing the strength of the dried body specimen to decrease to 0.51 MPa.

[0124] Comparing Example 1 and Example 5, all performance aspects of Example 5 decreased. The possible reasons are: the reduced dosage of sulfonated iron salt-modified activated carbon resulted in insufficient Fe(OH)3 catalytic components, and the high-dosage mineral powder was difficult to activate due to a lack of effective catalysis. A large amount of mineral powder relied solely on the alkalinity of the inorganic material for activation; the unreacted mineral powder existed as an inert filler, limiting the improvement in the strength of the dried body. Simultaneously, the severe lack of adsorption sites allowed salt ions and organic matter to directly interfere with the remaining small amount of gelation reaction, hindering the evaporation of moisture from the dried body and resulting in a slower decrease in water content.

[0125] Comparing Example 1 and Comparative Example 1, the performance of Comparative Example 1 showed a significant decline. The possible reason is that, without the sulfonation group, the biochar's adsorption of salt ions relies solely on the retention of physical pores, and it cannot achieve active adsorption through ion exchange. This is particularly true for highly water-soluble Na+. + Cl - The capture capacity is poor; at the same time, the physical adsorption is highly reversible, and during the drying process, adsorbed salt ions and organic matter desorb as water migrates, making it impossible to fix salt ions. Salt ion enrichment further inhibits the gelation reaction, resulting in a lower degree of hardening of the dried body, the inability to form smooth pore channels, a decrease in water evaporation, and a small change in the moisture content of the dried body, leading to a lower compressive strength of the specimen.

[0126] Comparing Example 1 and Comparative Example 2, the performance of Comparative Example 2 showed a significant decline. The possible reasons are as follows: Without the iron salt component, Fe(OH)3 colloid cannot be formed, resulting in insufficient hydration products from the secondary hydration of the mineral powder, a significant decrease in the depolymerization rate of the glass, and a reduction in the efficiency of cementitious product formation; at the same time, the lack of iron salt to guide the nucleation of ettringite crystals leads to irregular crystal growth and an inability to form a dense network with directional overlap, which increases the gaps between crystals, reduces structural strength, and prevents moisture from evaporating quickly, resulting in a persistently high moisture content and a compressive strength of only 0.28 MPa for the specimen.

[0127] Comparing Example 1 and Comparative Example 3, the performance of Comparative Example 3 was significantly reduced. The possible reasons are as follows: the sulfonated biochar and ferric chloride did not form a chemical bond, and the ferric chloride was lost with free water during the drying process, failing to stably form a catalytic colloid on the surface of the mineral powder particles, thus rendering the catalytic effect essentially ineffective; at the same time, physical mixing caused the adsorption sites of the sulfonated biochar to be occupied by free iron ions, reducing the adsorption efficiency for salt ions and organic matter, and the adsorption products had no spatial correlation with the catalytic components, failing to be timely encapsulated and fixed through the gelation reaction, remaining free in the reaction environment, affecting the formation of the gelling material, resulting in a test block strength of only 0.21 MPa, which is low.

[0128] Although the preferred embodiments of the present invention have been disclosed above, they are not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

Claims

1. A drier for high water content, high salt, high organic matter sludge, characterized by, The raw materials include, in parts by weight: 7-25 parts of quicklime, 10-50 parts of mineral powder, 1-10 parts of desulfurization gypsum, 1-5 parts of anhydrous sodium sulfate, and 2-12 parts of the activated carbon modified by both sulfonation and iron salt; The activated carbon modified by both sulfonation and iron salt is prepared by the following method: (1) Iron salt modification: The pretreated activated carbon is added into a ferric salt solution, and stirred at room temperature. After filtration, washing, drying, and calcination, the ferric salt modified biochar is obtained after cooling to room temperature; (2) Sulfonation modification: The ferric salt modified biochar is added into concentrated sulfuric acid under ice water bath condition, and stirred at elevated temperature. After the reaction, the reaction solution is poured into ice water. After filtration and washing until the pH of the filtrate is 3.0-4.0, drying and grinding, the activated carbon modified by both sulfonation and iron salt is obtained.

2. The drier of high water content, high salt, and high organic sludge according to claim 1, characterized by, The activated carbon modified by both sulfonation and iron salt accounts for 4-18% of the total mass of the drying agent.

3. The drier of high water content, high salt, and high organic sludge according to claim 1, characterized by, The activated carbon modified by both sulfonation and iron salt accounts for 9-13% of the total mass of the drying agent.

4. The drier of high water content, high salt, and high organic sludge according to claim 1, characterized by, In step (1), the pretreatment of the activated carbon is as follows: At room temperature, the activated carbon is added into a hydrochloric acid solution. The solid-liquid ratio of the activated carbon to the hydrochloric acid solution is 1: (15-25). After stirring for 2-3 h, filtration, washing until the pH of the filtrate is 6.5-7.0, and drying to constant weight, the pretreated activated carbon is obtained.

5. The high-moisture, high-salinity, high-organic-content sludge drying agent of claim 1, wherein, In step (1), the iron salt solution has a concentration of 0.8-1.2 mol / L FeCl3 6H2O aqueous solution, the solid-liquid ratio of the pretreated activated carbon and the iron salt solution is 1:(10-20), the reaction time is 4-8 h, and the calcination temperature is 360-400℃, and the calcination time is 2-3 h.

6. The high-moisture, high-salinity, high-organic-content sludge drying agent of claim 1, wherein, In step (2), the mass ratio of the ferric salt modified biochar to concentrated sulfuric acid is 1: (6-10). The reaction temperature is 70-80°C, and the reaction time is 3-5 h.

7. A method for preparing the drier of high water content, high salt, high organic matter sludge according to any one of claims 1 to 6, characterized in that, The preparation method comprises the following steps: The quicklime, mineral powder, desulfurization gypsum, anhydrous sodium sulfate, and activated carbon modified by both sulfonation and iron salt are mixed uniformly, dried, and sieved to obtain the drying agent.

8. The method of claim 7, wherein the drying agent is prepared by the steps of: The specific steps include: (a) The quicklime, mineral powder, desulfurization gypsum, and anhydrous sodium sulfate are added into a mixing machine, and mixed at a speed of 25-30 r / min for 15-20 min to obtain an inorganic cement base; (b) The activated carbon modified by both sulfonation and iron salt is added into the inorganic cement base obtained in step (a), and mixed at a speed of 20-25 r / min for 20-25 min to obtain a mixture; (c) The mixture obtained in step (b) is dried at 60-80°C for 1-2 h, and the water content is controlled to be ≤2%; (d) The dried material is sieved through a 100-mesh sieve, and the undersize material is the finished product of the drying agent.

9. Application of a sludge drying agent in treating high-moisture, high-salinity, and high-organic sludge. The sludge drying agent is the drying agent for high-moisture, high-salinity, and high-organic sludge according to any one of claims 1-6, or is prepared by the method according to any one of claims 7-8. The addition amount of the sludge drying agent is 4-10 wt% of the total mass of the sludge to be treated.

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