A method for preparing solid electrolyte using sludge from sand and gravel processing system

Abstract

The present invention discloses a method for preparing a solid electrolyte using sludge from a sand and gravel processing system. The main steps of the method are: drying and crushing the sludge from the sand and gravel processing system for pretreatment, adding silicate cement and a conductive material to the pretreated sludge, mixing them evenly, and calcining the mixture at a high temperature of 750-850°C for 1-2 hours under a nitrogen protection environment to obtain an electrolyte material; the conductive material is conductive charcoal powder or carbonized kitchen waste compost powder. The prepared electrolyte material can be further used to prepare a solid-state supercapacitor or a solid-state battery. This capacitor can be used as a wall tile, floor tile, or pavement tile, and can be combined with renewable energy to form an energy storage capacitor and a wireless charging device. The present invention not only realizes the resource utilization of solid waste from sand and gravel processing system sludge, but also realizes the multifunctional application of cement-based composite materials.

Description

Technical Field

[0001] The present invention relates to the technical field of sludge resource utilization, in particular to a method for preparing solid electrolytes by utilizing sludge from a sand and gravel processing system. Background Art

[0002] Large hydropower stations or construction sites use biotite-quartz schist excavated from construction projects as a source of aggregate for sand and gravel production. Wastewater generated in sand and gravel processing systems primarily comes from the washing of crushed stone in the crushing plant, the washing of coarse aggregate in the screening plant, the washing of finished sand, and the use of water for dust suppression and cleaning in various workshops. The sludge produced after the sand and gravel processing wastewater is treated is pumped into a box-frame filter press by a slurry pump. After drying, the sludge is transported to a waste dump, which not only poses an ecological threat but also easily causes secondary pollution, contaminating the air, soil, and groundwater, and occupying large areas of land. The sludge has an excessive pH value, a very low organic matter content, and insufficient levels of available nitrogen, phosphorus, and potassium for plant growth. Furthermore, it lacks essential nutrients for plant growth. The soil also has low porosity, poor agglomeration, poor water retention, and poor aeration. Some heavy metals exceed permitted limits, and it exhibits high levels of biotoxicity. Wastewater treatment and sludge disposal in sand and gravel processing systems have long been a challenge for artificial sand and gravel processing.

[0003] Pumped storage is currently the mainstream technology for large-scale energy storage at hydropower stations, offering advantages such as large storage capacity, high system efficiency, long operating life, and mature technology. However, pumped storage only stores electricity for different periods of time, wastes significant amounts of hydraulic resources, and fails to fundamentally address the storage issues of electricity and renewable energy. The development of solid-state electrolytes or cement-based solid-state electrolytes, which could transform the sludge and cement from sand and gravel processing systems generated during hydropower station construction into solid-state electrolyte materials for supercapacitors or batteries, would have revolutionary implications for the storage of hydropower and renewable energy. Combined with wireless charging technology, roads and buildings could be transformed into charge-discharge energy storage systems. Summary of the Invention

[0004] In order to achieve harmless treatment and resource utilization of sludge from a sand and gravel processing system, the present invention provides a method for preparing a solid electrolyte using the sludge from a sand and gravel processing system.

[0005] The present invention provides a method for preparing a solid electrolyte from sand and gravel processing sludge. The main idea is to pre-treat the sand and gravel processing sludge by drying and crushing it. Portland cement and a conductive material are added to the pre-treated sludge, mixed evenly, and then calcined at 750-850°C for 1-2 hours under a nitrogen atmosphere to obtain the electrolyte material. The conductive material is preferably conductive charcoal powder or carbonized kitchen waste compost powder.

[0006] Electrolyte materials can be further used to create solid-state supercapacitors or solid-state batteries. Electrolyte materials, positive electrodes, and negative electrodes are assembled to create solid-state batteries or capacitors. These capacitors can be used as wall tiles, floor tiles, and pavement tiles, and can be combined with renewable energy sources to create energy storage capacitors and wireless charging devices.

[0007] The electrolyte preparation method can be specifically carried out according to the following two methods.

[0008] Method 1, the steps are as follows:

[0009] S1. Pretreatment of sludge from sand and gravel processing system: The sludge generated after wastewater treatment in a sand and gravel processing system of a hydropower station was naturally dried until the sample reached a constant weight (the mass change of the sludge did not exceed 1%), and then crushed.

[0010] S2. Add acid to the sludge from the sand and gravel processing system, stir for 10-30 minutes, filter to remove insoluble matter, and obtain a solution.

[0011] The acid solution is selected from any one of hydrochloric acid, nitric acid, and sulfuric acid, or a mixture of two of them.

[0012] The hydrochloric acid dissolution of the sand and gravel processing system sludge primarily removes components unsuitable for solid electrolytes, retaining active elements required for solid-state electrolysis, such as lithium, yttrium, and iron. When hydrochloric acid is used for dissolution, chloride ions can also be added, partially forming halide electrolyte materials.

[0013] S3. Add thiosulfate to the solution obtained in step S2, and then add urea or potassium hydroxide to make the solution alkaline to precipitate a precipitate, filter, and dry the precipitate.

[0014] Thiosulfate is added in this step to form a partially sulfide metal salt electrolyte material, resulting in a highly conductive sulfide electrolyte. Adding urea can form a precipitate that further forms various active metal elements bridged and coordinated by nitrogen atoms, improving conductivity and energy storage efficiency.

[0015] S4. Add silicate cement, potassium hydroxide and a conductive material to the dried precipitate, mix them evenly, and calcine the mixture at 750-850° C. for 1-2 hours under a nitrogen atmosphere to obtain an electrolyte material.

[0016] In this step, cement and sludge from the sand and gravel processing system are added to prepare a cement-based solid electrolyte, which improves its conductivity. The high-temperature calcination process removes moisture and allows the different electrolyte materials to polymerize, increasing the specific surface area and porosity, thereby enhancing conductivity and energy storage.

[0017] Preferably, in step S2, the volume ratio of the sludge in the sand and gravel processing system to the acid solution is 1:(3-5).

[0018] It is further preferred that the acid solution is concentrated hydrochloric acid with a mass fraction of hydrogen chloride of 36% to 38%.

[0019] Preferably, in step S4, the amount of silicate cement added is 5-35% of the mass of the precipitate, and the amount of potassium hydroxide added is 1-3% of the mass of the precipitate.

[0020] The conductive material is conductive charcoal powder (carbon black) or carbonized kitchen waste compost powder, and the amount of conductive material added is 1.5-5% of the mass of the precipitate. Humic acid and carbon black in kitchen waste compost can increase the energy storage and voids of the electrolyte, and increase ion migration, conversion and aggregation.

[0021] Method 2, steps are as follows:

[0022] S1. Dry and crush the sludge from the sand and gravel processing system for pre-treatment.

[0023] S2. Add lithium salt, water, silicate cement and conductive material to the pretreated sludge from the sand and gravel processing system, mix and stir for 10-30 minutes, and calcine the mixture at 750-850° C. for 1-2 hours under a nitrogen protection environment to obtain an electrolyte material.

[0024] Compared with the prior art, the present invention is beneficial in that:

[0025] The present invention prepares solid electrolyte materials by using useful components in sand and gravel processing system sludge, thereby not only realizing resource utilization of sand and gravel processing system sludge solid waste, but also realizing multifunctional application of cement-based composite materials.

[0026] Other advantages, objectives and features of the present invention will be reflected in part from the following description and will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a scanning electron microscope image of the electrolyte material powder prepared in Example 1.

[0028] Figure 2 This is a transmission electron microscope image of the electrolyte material powder prepared in Example 1. DETAILED DESCRIPTION

[0029] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0030] Example 1

[0031] A method for preparing solid electrolytes using sludge from a sand and gravel processing system, comprising the following steps:

[0032] (1) Pretreatment of sludge from sand and gravel processing system: The sludge generated after wastewater treatment in the sand and gravel processing system of a hydropower station was naturally dried until the sample reached a constant weight (the mass change of the sludge did not exceed 1%), and then crushed.

[0033] (2) Add concentrated hydrochloric acid with a concentration of 36% to 38% to the pretreated sludge from the sand and gravel processing system, with a volume ratio of sludge to concentrated hydrochloric acid of 1:4, stir for 30 minutes, filter to remove insoluble matter, and obtain solution A; take 1 L of solution A, add 1.5 mol of sodium thiosulfate, and add urea to adjust the pH of the solution to greater than 9. A large amount of precipitate precipitates in the solution, filter, collect the precipitate and dry it.

[0034] (3) Add silicate cement and a small amount of potassium hydroxide to the dried precipitate, with the amount of silicate cement accounting for 25wt% of the precipitate and the amount of potassium hydroxide accounting for 1wt% of the precipitate. After mixing evenly, add conductive charcoal powder (carbon black), with the amount of conductive charcoal powder (carbon black) accounting for 4wt% of the precipitate. After mixing evenly, place in a high-temperature furnace and calcine at 800°C for 1 hour under nitrogen protection to prepare an electrolyte material.

[0035] (4) The electrolyte material is taken out of the high-temperature furnace while it is still hot and quickly poured into a brick-making mold. When it has not yet completely hardened and has good fluidity, two electrodes (stainless steel sheets or other electrodes) are placed on both sides of the electrolyte. After the slurry hardens, an integrated supercapacitor is formed.

[0036] The scanning electron microscope and transmission electron microscope images of the electrolyte material powder prepared in Example 1 are as follows: Figure 1 and 2 shown.

[0037] In order to analyze the surface morphology of the solid electrolyte powder and determine the structure of the prepared product, the electrolyte powder with better effect of 800℃ high temperature treatment (electrolyte powder prepared in Example 1) was selected for scanning electron microscopy test to observe its surface morphology and structure. Figure 1 (a) shows the image of particles of different sizes, which can be observed by magnifying them 4,000 times. Figure 1 (b) In the area shown in the picture, a graphene-like layered structure can be clearly observed, generating the expected layered structure. Further magnification of 20,000 times yields Figure 1 (c) and Figure 1 (d) From the structural cross-section in the figure, it can be found that the structure has an obvious layered structure, and tiny powder particles are attached to its surface. Combined with the XRD spectrum analysis results, it can be considered that the solid electrolyte was successfully prepared.

[0038] Figure 2The darker colored area has good conductivity, while the lighter colored area has poor conductivity. The XRD pattern shows that the conductive part is mainly composed of NASCION-type stoichiometric ratio. Figure 2 As shown in (a), crystal agglomeration occurs in some areas, and the surrounding areas are accompanied by pore structures generated by sintering. Although the existence of pore structures may be beneficial to reduce the impact of volume changes, according to Figure 2 As shown in (b) and (c), the sintered pore area seems to be more prone to agglomeration, which obviously has an adverse effect on the conductivity of the electrolyte; further zooming in, such as Figure 2 The solid electrolyte particles shown in (d) have a thin carbon coating layer. Combined with the SEM image results, the overall results indicate that the solid electrolyte structure was successfully synthesized.

[0039] The electrochemical performance of the supercapacitor was tested using an electrochemical workstation (Shanghai Chenhua 660e). The ionic conductivity of the solid electrolyte prepared by the above method was 192.3-564.7 mS·cm -1 . When a constant voltage is applied, the corresponding current of the supercapacitor can basically reach a constant value instantly. When the voltage is reversed, the current instantly returns to the corresponding negative constant value. Cement-based supercapacitors can output current sustainably and stably, with a charge and discharge time of 31-58s. They have good capacitive behavior, a specific capacitance of 85F / g-115F / g, an internal resistance of 26.6Ω-39.8Ω, an interface resistance of 6.7Ω-30.5Ω, and a small resistance to ion diffusion and migration in the electrolyte in the low-frequency region.

[0040] The voltage of the capacitor is 0.8-1.1U(V), the current can reach 5.3-7.8mA, and the specific capacity reaches 131-210mAh / g. When the current density is 0.5A·g -1 When the structure supercapacitor has 95.6F·g -1 The high specific capacitance of the battery can be maintained at 76.2% and the coulombic efficiency is 87.1% after 2000 cycles of constant current charge and discharge, showing a good cycle life.

[0041] Example 2

[0042] A method for preparing solid electrolytes using sludge from a sand and gravel processing system, comprising the following steps:

[0043] (1) Pretreatment of sludge from sand and gravel processing system: The sludge generated after wastewater treatment in the sand and gravel processing system of a hydropower station was naturally dried until the sample reached a constant weight (the mass change of the sludge did not exceed 1%), and then crushed.

[0044] (2) Lithium chloride, water, silicate cement and conductive charcoal powder (carbon black) are added to the pretreated sludge and stirred for 30 minutes to mix evenly; the amount of lithium chloride added accounts for 5wt% of the sludge weight, the amount of water added accounts for 10wt% of the sludge weight, the amount of silicate cement added accounts for 15wt% of the sludge weight, and the amount of conductive charcoal powder added accounts for 1.0wt% of the sludge weight; the mixture is placed in a high-temperature furnace and calcined at 750°C for 2h under nitrogen protection to prepare an electrolyte material.

[0045] (3) The electrolyte material is taken out of the high-temperature furnace while it is still hot and quickly poured into a brick-making mold. When it has not yet completely hardened and has good fluidity, two electrodes (stainless steel sheets or other electrodes) are placed on both sides of the electrolyte. After the slurry hardens, an integrated supercapacitor is formed.

[0046] The electrochemical performance of the supercapacitor was tested using an electrochemical workstation (Shanghai Chenhua 660e), and the ionic conductivity of the solid electrolyte was 91.7-298.6 mS·cm -1 The resulting supercapacitors exhibited specific capacitances ranging from 598 to 782 F / V, electrolyte resistances ranging from 19.1 Ω to 31.7 Ω, and charge transfer resistances ranging from 11.6 Ω to 51.2 Ω. After 2000 constant current charge-discharge cycles, the capacitance retention reached 86.1-95.3%, and the coulombic efficiency was 81.6-91.2%, demonstrating excellent cycle life.

[0047] It has demonstrated good adaptability through durability testing, water resistance testing, and drying shrinkage testing, and can adapt to the changing requirements of high and cold areas and high and low temperatures.

[0048] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with this profession can make some changes or modifications to equivalent embodiments of the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for preparing solid electrolytes using sludge from a sand and gravel processing system, characterized in that: The following steps are involved: S1. Drying and crushing the sludge from the sand and gravel processing system; S2. Add acid to the pretreated sludge from the sand and gravel processing system, stir for 10-30 minutes, and filter to remove insoluble matter to obtain a solution; S3, adding thiosulfate to the solution obtained in step S2, and then adding urea or potassium hydroxide to make the solution alkaline to precipitate a precipitate, filtering, and drying the precipitate; S4. Add silicate cement, potassium hydroxide and a conductive material to the dried precipitate, mix them evenly, and calcine the mixture at 750-850° C. for 1-2 hours under a nitrogen atmosphere to obtain an electrolyte material.

2. The method for preparing a solid electrolyte using sludge from a sand and gravel processing system according to claim 1, wherein: The acid solution is selected from any one of hydrochloric acid, nitric acid, and sulfuric acid, or a mixture of two of them.

3. The method for preparing a solid electrolyte using sludge from a sand and gravel processing system according to claim 2, wherein: The volume ratio of sludge to acid in the sand and gravel processing system is 1:(3-5).

4. The method for preparing a solid electrolyte using sludge from a sand and gravel processing system according to claim 1, wherein: The amount of silicate cement added is 5-35% of the precipitate mass.

5. The method for preparing solid electrolyte using sludge from a sand and gravel processing system according to claim 1, wherein: In step S4, the amount of potassium hydroxide added is 1-3% of the mass of the precipitate.

6. The method for preparing solid electrolytes using sludge from a sand and gravel processing system according to claim 1, wherein: The amount of the conductive material added is 1.5-5% of the amount of the precipitate.

7. The method for preparing a solid electrolyte using sludge from a sand and gravel processing system according to claim 1, wherein: The prepared electrolyte material, positive electrode and negative electrode are assembled to form a solid-state battery or capacitor.

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