Self-cleaning water permeable brick based on sludge biochar-TiO2 composite material and preparation method of self-cleaning water permeable brick

Abstract

The invention belongs to the technical field of environmental protection and building materials, and particularly relates to a self-cleaning water permeable brick based on a sludge biochar-TiO2 composite material and a preparation method thereof.The preparation method comprises the following steps that industrial sludge biochar and nanoscale titanium dioxide are mixed and then ground, and the sludge biochar-TiO2 composite material is obtained; the preparation method comprises the following steps: respectively preparing a surface layer mixture and a base layer mixture, wherein the surface layer mixture contains a sludge carbon-TiO2 composite material; the base layer mixture is guided into a mold for static pressing; pouring the surface layer mixture into the upper surface of the base layer mixture subjected to static pressure, and then performing static pressure; demolding after curing, and then curing for 28 + / -3 days under standard curing conditions to obtain the water permeable brick. The water permeable brick is a functional water permeable brick used for purifying organic pollutants (especially polycyclic aromatic hydrocarbons (PAHs)) in rainwater.

Description

Technical Field

[0001] This invention belongs to the field of environmental protection and building materials technology, specifically relating to a functional permeable brick for purifying organic pollutants (especially polycyclic aromatic hydrocarbons, PAHs) in rainwater and its preparation method. Background Technology

[0002] The rapid pace of urbanization has led to a surge in the area of ​​impermeable pavements, directly exacerbating the frequency of urban flooding and exacerbating non-point source pollution. In recent years, road runoff, enriched with large amounts of organic matter, nutrients, and heavy metals, has raised widespread concerns about its pollution risks. These runoff pollutants not only disrupt the stability of aquatic ecosystems but may also induce various diseases through water circulation, posing a serious threat to human health. While permeable bricks are an effective means of alleviating urban flooding, traditional permeable bricks, primarily made of sand, gravel, and cement, are limited to infiltration and drainage. Their removal rate of organic pollutants in rainwater, especially persistent organic pollutants such as polycyclic aromatic hydrocarbons (PAHs), is extremely low (usually less than 10%), failing to effectively control rainwater pollution. Furthermore, during long-term use, the pores of traditional permeable bricks are easily clogged by suspended particles in the water, leading to a rapid decline in permeability and a significant shortening of their actual service life, making it difficult to meet the long-term needs of urban stormwater management and ecological protection. Therefore, developing a permeable brick that combines high permeability, long-lasting pollutant removal capability (especially for PAHs), and anti-clogging and self-regeneration functions has become a key technical problem that urgently needs to be solved in this field.

[0003] Industrial sludge is a solid precipitate produced during the treatment of industrial wastewater. It is generally characterized by high viscosity, high oil content, and a high proportion of inorganic matter. Unlike municipal sludge, it has a complex composition and significant toxicity, commonly containing heavy metals (copper, nickel, cadmium, etc.), polycyclic aromatic hydrocarbons, and other recalcitrant organic compounds. Due to its hazardous characteristics such as leaching toxicity and corrosiveness, it is included in the "National Hazardous Waste List".

[0004] Biochar preparation technology provides a new approach for the efficient disposal of industrial sludge: This technology transforms the organic matter in sludge into biochar with a porous structure and high specific surface area through controlled pyrolysis at 300-800℃. In the process, not only can the volume of sludge be reduced by more than 50% and the mass reduced by 30%-40%, achieving significant volume reduction, but it can also kill pathogens through pyrolysis and fix heavy metals in the biochar lattice, reducing their bioavailability and achieving the goal of harmlessness.

[0005] Chinese patent (application number: CN2019103757891) discloses a method for preparing adsorbent permeable bricks using electrolytic manganese slag as the main raw material. The required raw materials mainly include electrolytic manganese slag, waste ceramics, zeolite, and kaolin. In this method, the adsorption function is mainly achieved by zeolite. After acid leaching, the zeolite, with its porous structure and ion exchange characteristics, adsorbs dissolved heavy metals and phosphorus from surface runoff. However, the zeolite requires multiple pretreatment steps, which increases the complexity of the process. Furthermore, the method does not mention a solution to the potential zeolite adsorption saturation problem after long-term use of the permeable bricks; subsequent maintenance of adsorption performance may require periodic replacement or regeneration of the zeolite. In addition, the electrolytic manganese slag in the raw materials contains approximately 13.3% SO3, which, if not properly controlled in the treatment process, can easily lead to SO3 leaching pollution.

[0006] Chinese patent (application number: CN201510762208.1) discloses a method for preparing self-cleaning permeable bricks using fluorapatite as the main raw material. The required raw materials include fluorapatite, silica fume, bauxite homogenizer, sugar filter mud, carbon black, and slag wool, making the raw material composition relatively complex. Furthermore, the permeable bricks require a high-temperature sintering process, resulting in high energy consumption. In addition, because the pores of the brick body rely on a "carbonate pore-forming agent" for formation, they are easily clogged by mud, sand, and microorganisms during long-term use, thus requiring frequent maintenance. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a self-cleaning permeable brick based on sludge biochar-TiO2 composite material and its preparation method.

[0008] To address the aforementioned technical problems, this invention provides a method for preparing self-cleaning permeable bricks based on sludge biochar-TiO2 composite materials, comprising the following steps:

[0009] 1) Preparation of sludge-TiO2 composite material:

[0010] Industrial sludge biochar and nano-sized titanium dioxide were mixed at a mass ratio of (5±0.5):1 and then ground (until they passed through a 40~60 mesh sieve) to obtain sludge biochar-TiO2 composite material (i.e., sludge biochar-TiO2 composite material).

[0011] 2) Preparation of surface mixture:

[0012] The surface mixture consists of the following components by mass percentage: 58%~63% quartz sand, 22%~25% river sand, 8%~12% sludge-carbon-TiO2 composite material, and 5% epoxy resin (as a binder).

[0013] Instructions: Mix the above four materials and place them in a mixer and stir (stir for 4-6 minutes) to obtain the surface mixture;

[0014] 3) Preparation of base layer mixture:

[0015] Weigh water and silicate cement according to the water-cement ratio (0.3±0.05), mix them evenly with basalt to obtain the base course mixture; the weight ratio of basalt to silicate cement is (4±0.2):1.

[0016] Note: The water-cement ratio is (0.3±0.05), which is the weight ratio of water to silicate cement = (0.3±0.05):1.

[0017] Mix the two materials with water and place them in a mixer and stir (stir for 4-6 minutes) to obtain the base mixture.

[0018] This achieves a target porosity of approximately 20% for the base layer.

[0019] 4) Pour the base mixture obtained in step 3) into the mold, with a base mixture filling thickness of 40~60mm, and press statically; then pour the surface mixture obtained in step 2) onto the upper surface of the statically pressed base mixture, controlling the surface mixture filling thickness to 8~12mm, and then press statically; after curing, demold, and then cure for 28±3 days under standard curing conditions (temperature 20±2℃, relative humidity ≥95%) to obtain permeable bricks.

[0020] As an improvement to the preparation method of the self-cleaning permeable brick based on sludge biochar-TiO2 composite material of the present invention: industrial sludge is used as raw material, and after drying (conventional outdoor air drying for about one week), grinding and sieving (10~20 mesh), it is pyrolyzed at (500±20)℃ for (4±0.5) hours under the protection of an inert atmosphere (including nitrogen) to obtain industrial sludge biochar.

[0021] Note: Pyrolysis can be carried out in a tubular furnace, followed by natural cooling to obtain industrial sludge biochar.

[0022] As a further improvement to the preparation method of the self-cleaning permeable brick based on sludge biochar-TiO2 composite material of the present invention: pyrolysis is performed by programmably heating to (500±20)℃ at a heating rate of (10±2)℃ / min.

[0023] As a further improvement to the preparation method of the self-cleaning permeable brick based on sludge biochar-TiO2 composite material of the present invention:

[0024] Basalt has a mesh size of 4-8 mesh, quartz sand has a mesh size of 20-45 mesh, river sand has a mesh size of 8-100 mesh, and nano-titanium dioxide has a mesh size of 5-30 nm.

[0025] As a further improvement to the preparation method of the self-cleaning permeable brick based on sludge biochar-TiO2 composite material of the present invention:

[0026] The silicate cement is P.O 42.5R cement.

[0027] As a further improvement to the preparation method of the self-cleaning permeable brick based on sludge biochar-TiO2 composite material of the present invention:

[0028] In step 4):

[0029] The static pressure corresponding to the base course mix is: static pressure of 1MPa for 10~15s;

[0030] The static pressure after adding the surface mixture is: static pressure of 3~5MPa for 45~60s;

[0031] The standard maintenance conditions are: temperature 20±2℃, relative humidity ≥95%.

[0032] This invention also provides a self-cleaning permeable brick prepared using any of the above methods: a self-cleaning permeable brick with a double-layer composite structure of a base layer and a surface layer. The porosity of the base layer is controlled at around 20%, mainly providing structural strength and basic water permeability channels. The surface layer and the base layer are jointly pressed into a single brick body.

[0033] Sludge biochar-TiO2 composite material is a highly efficient pollutant treatment material based on the synergistic effect of adsorption and photocatalysis. The biochar pore surface adsorbs nano-titanium dioxide, a photocatalytic material. Upon light irradiation, it generates hydroxyl radicals, superoxide radicals, and H2O radicals, all possessing strong oxidation and decomposition capabilities, directly oxidizing persistent organic matter. Its core value lies in overcoming the technical shortcomings of single adsorbent or photocatalytic materials through the functional complementarity and mechanistic coupling of the two components, achieving a closed-loop treatment of pollutants through "rapid capture-deep mineralization-material regeneration." This composite material combines the high adsorption capacity of sludge biochar with the photocatalytic activity of TiO2.

[0034] This invention aims to overcome the shortcomings of existing technologies, on the one hand realizing the resource utilization of industrial waste, and on the other hand providing solutions for alleviating urban flooding and effectively purifying organic pollutants in rainwater runoff. Ultimately, it provides a permeable brick with synergistic adsorption and photocatalytic degradation that can efficiently remove organic pollutants such as polycyclic aromatic hydrocarbons (PAHs) from rainwater, and also has excellent permeability, high strength and a certain degree of self-cleaning function, as well as its preparation method.

[0035] Compared with existing technologies, this invention has the following significant advantages: It achieves a removal rate of 55%–95% for the 16 polycyclic aromatic hydrocarbons (PAHs) prioritized for control by the US Environmental Protection Agency (USEPA), far exceeding that of traditional permeable bricks (whose removal rate is <10%); relying on an adsorption-photocatalysis synergistic mechanism, the material can be regenerated under light after adsorption saturation, extending its service life and preventing secondary pollution at its source; while achieving highly efficient purification, it maintains excellent permeability (permeability coefficient ≥3.7mm / s) and mechanical properties (compressive strength ≥30 MPa); and using waste sewage sludge as raw material realizes high-value resource utilization of waste, deeply aligning with the concept of green and sustainable development; furthermore, the optimized pore structure of the functional surface layer, combined with adsorption, reduces the migration of fine particles, giving the product superior long-term permeability stability. This invention can be specifically applied to urban rainwater treatment, especially to remove organic pollutants such as PAHs in rainwater through the synergistic effect of adsorption and photocatalysis of the functional surface layer. Specifically, the pollutants are first adsorbed and enriched by the sludge-carbon-TiO2 composite material component in the surface layer, and then catalytically degraded by the adjacent TiO2 component under light conditions (especially ultraviolet light), thereby realizing the in-situ regeneration of the material and the complete removal of pollutants, while giving the permeable bricks self-cleaning ability.

[0036] Based on composite sand-based permeable bricks, this invention specifically adds sludge-derived biochar made from the pyrolysis of industrial waste and nano-titanium dioxide with photocatalytic degradation function to the surface layer. This design not only significantly improves the permeable brick's ability to remove runoff pollutants, achieving a removal rate of 55%–95%, but also effectively degrades persistent organic pollutants with the help of light energy, achieving a degradation rate of 40%–95%. Compared to traditional composite permeable bricks, this invention adds the function of removing environmental pollutants, and its double-layer structure has superior anti-clogging properties, high permeability, and high compressive strength, providing an innovative solution for urban stormwater pollution control. Attached Figure Description

[0037] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0038] Figure 1 This is a physical image of the permeable brick prepared in Example 1 of this invention.

[0039] Figure 2 This is a schematic diagram of the experimental setup. Detailed Implementation

[0040] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto:

[0041] The permeable bricks produced in the following examples are all 200mm long, 100mm wide, and 60mm high.

[0042] The industrial sludge originated from the wastewater treatment plant of Juhua Chemical Group in Quzhou City, Zhejiang Province. Its main components include humus, protein, inorganic salts, and inorganic particles (sludge); the percentages of some heavy metals are as follows:

[0043] Vanadium (V) 0.021% Chromium (Cr) 0.070 % Manganese (Mn) 0.122% Iron (Fe) 7.481% Nickel (Ni) 0.103% Copper (Cu) 0.139% Zinc (Zn) 0.341%

[0044] Example 1

[0045] The raw material components of permeable bricks include basalt (4-8 mesh), epoxy resin, quartz sand (20-45 mesh), river sand (8-100 mesh), 40-60 mesh sludge biochar-TiO2 composite material, and PO 42.5R cement (ordinary Portland cement). The preparation method is as follows:

[0046] (1) Take 150g of dried (usually air-dried outdoors for about one week) and sieved (10-20 mesh) industrial sludge, place it in a tube furnace, and heat it to 500℃ at a programmed heating rate of 10℃ / min under a nitrogen atmosphere, and pyrolyze it at this temperature for 4 hours. After natural cooling, industrial sludge biochar is obtained. Subsequently, the obtained industrial sludge biochar and titanium dioxide (5-10nm nano-sized titanium dioxide) are weighed at a mass ratio of 5:1, mixed and ground thoroughly (until passing through a 40-60 mesh sieve). After uniform mixing, sludge biochar-TiO2 composite material is obtained.

[0047] (2) Surface mixture: Take 5% epoxy resin, 62% quartz sand, 25% river sand and 8% sludge carbon-TiO2 composite material obtained in step (1) by weight percentage, mix them thoroughly in a mixer to obtain the surface mixture.

[0048] (3) Base course mixture: Weigh out PO 42.5R cement and water at a water-cement ratio of 0.3, and mix them evenly with basalt (basalt aggregate) to obtain the base course mixture. The weight ratio of basalt to PO 42.5R cement is 4:1.

[0049] The water-cement ratio of 0.3 means that the weight ratio of water to PO 42.5R cement is 0.3.

[0050] (4) In a 200×100×60mm (length×width×height) mold, first add the base layer mixture, level it, and control the height to 50mm. Then, press it statically at 1MPa for 10~15s. Next, add the surface layer mixture to fill the mold (i.e., the height of the surface layer mixture is 10mm), and press it statically at 3MPa for 45~60s to form the mold. After curing at normal room temperature for 24 hours and demolding, cure it in a standard curing room (temperature 20±2℃, humidity ≥95%) for 28 days to obtain the self-cleaning permeable brick of the present invention.

[0051] Experiment 1, Adsorption

[0052] The permeable bricks obtained in Example 1 (permeable bricks that have been cured) were placed in... Figure 2 In the experimental apparatus shown, a mixed standard aqueous solution of 16 polycyclic aromatic hydrocarbons (PAHs) with a concentration of ≈1 mg / L (as shown in Table 1) was introduced and continuously sprayed for 1 hour at a flow rate of 1.5 mm / s (the mixed standard aqueous solution of 16 polycyclic aromatic hydrocarbons (PAHs) was collected in a container after being filtered through a permeable brick). The initial concentration of the influent and the final concentration of the effluent were then measured.

[0053] The adsorption efficiency of the permeable bricks obtained in Example 1 is shown in Table 1.

[0054] Table 1

[0055]

[0056] Experiment 2: Photocatalysis

[0057] Based on the influent and effluent concentrations of the 16 polycyclic aromatic hydrocarbons (PAHs) standard solutions in Experiment 1, the adsorption capacity of the permeable bricks for PAHs was calculated using Formula 1. Subsequently, the PAH-adsorbed permeable bricks were placed under sunlight for 6 hours. After the irradiation period, the surface layer of the permeable bricks was separated and crushed in a crusher. The crushed surface material was extracted using an organic solvent (acetone: n-hexane = 1:1), and the residual concentration of PAHs after degradation was determined. This is a standard experimental procedure.

[0058] Formula 1:

[0059] =

[0060] Q e Adsorption capacity (mg / kg)

[0061] C0: Initial concentration (mg / L)

[0062] C e Equilibrium concentration (mg / L)

[0063] V: Solution volume (L)

[0064] m: Biochar mass (kg)

[0065] Formula 2

[0066] q=

[0067] q: Volume (mg / kg)

[0068] C: Concentration (mg / L)

[0069] V: Constant volume (L)

[0070] m: Sample mass (kg)

[0071] The photocatalytic efficiency of the permeable bricks obtained in Example 1 is shown in Table 2.

[0072] Table 2

[0073]

[0074] illustrate:

[0075] Taking naphthalene-NAP as an example, the pollutant content in the permeable brick was calculated according to Formula 1. The influent concentration (C0 = 1.087 mg / L) and effluent concentration (Ce = 0.213 mg / L) in Table 1 were used. In this Example 1, the amount of sludge-carbon-TiO2 composite material added was 5.78 g (m = 0.00578 kg). After spraying in Experiment 1, 20 ml of solution (V = 0.02 L) was drawn from the collection container for testing. =3.03577 mg / L, finally obtained as 3.036 mg / kg;

[0076] The pollutant content in the permeable bricks after degradation was calculated according to Formula 2. After the surface layer of the permeable bricks was crushed following light exposure, 1g of the surface material was extracted using an organic solvent. The extracted material was then diluted to 1ml. The concentration of naphthalene-NAP was determined to be 0.148mg / L. Therefore, the naphthalene-NAP content in the surface material after light exposure was... =0.148mg / kg, the final result is 0.148mg / kg.

[0077] The permeable bricks obtained in Experiment 3 and Example 1 have a compressive strength of 41 MPa according to the national testing standard GB / T 28635-2012 and a permeability coefficient of 4.2 mm / s according to the national testing standard GB / T 25993-2010.

[0078] Example 2: Compared to Example 1, the following changes are made:

[0079] The surface mixture of "5% epoxy resin, 62% quartz sand, 25% river sand, and 8% sludge-TiO2 composite material" was changed to "5% epoxy resin, 66% quartz sand, 27% river sand, and 2% sludge-TiO2 composite material," with the rest remaining the same as in Example 1. The adsorption performance of the permeable bricks was determined according to the above test methods. Based on the experimental data in Table 1, the three pollutants with the best adsorption effect (anthracene, β-anthracene, and dibenzo[a,h]anthracene) were selected for targeted analysis and detection.

[0080] The adsorption efficiency of the permeable bricks obtained in Example 2 is shown in Table 3.

[0081] Table 3

[0082] Simulated pollutants Influent concentration effluent concentration Adsorption efficiency Anthracene 0.973 mg / L 0.732 mg / L 24.76% CHR 1.110 mg / L 0.816 mg / L 26.48% Dibenzo[a,h]anthracene-DBA 1.072 mg / L 1.015 mg / L 5.32%

[0083] Comparing Tables 1 and 3, it can be seen that: Example 1, by introducing 8% sludge biochar-TiO2 composite material into the functional surface layer, constructed a high specific surface area, porous adsorption system mainly composed of biochar, effectively enriching and immobilizing polycyclic aromatic hydrocarbons (PAHs), thereby significantly improving the adsorption efficiency for high-cyclic PAHs. In contrast, Example 2 only added 2% sludge biochar-TiO2 composite material, lacking sufficient biochar pore structure to achieve effective adsorption and enrichment, resulting in a shorter residence time of pollutants in the brick body and insufficient contact sites, thus significantly reducing its adsorption efficiency.

[0084] Example 3: Compared to Example 1, the following changes are made:

[0085] The composition of the surface mixture, "5% epoxy resin, 62% quartz sand, 25% river sand, and 8% sludge-TiO2 composite material", was changed to "5% epoxy resin, 66% quartz sand, 27% river sand, and 2% sludge-TiO2 composite material".

[0086] Furthermore, sludge-TiO2 composite material is added to the base mixture accordingly, that is, the weight ratio of basalt: P.O42.5R cement: sludge-TiO2 composite material is controlled at 4:1:0.08.

[0087] The rest is the same as in Example 1. The adsorption performance of the permeable bricks was determined according to the above test method. Based on the experimental data in Table 1, the three pollutants with the best adsorption effect (anthracene, β-anthracene, and dibenzo[a,h]anthracene) were selected for targeted analysis and detection.

[0088] The adsorption efficiency of the permeable bricks obtained in Example 2 is shown in Table 4.

[0089] Table 4

[0090] Simulated pollutants Influent concentration effluent concentration Adsorption efficiency Anthracene 0.973 mg / L 0.598 mg / L 38.54% CHR 1.110 mg / L 0.716 mg / L 35.49% Dibenzo[a,h]anthracene-DBA 1.072 mg / L 0.902 mg / L 15.85%

[0091] Comparing Tables 1 and 4, it can be seen that: Example 1, by adding 8% sludge-TiO2 composite material to the surface layer, constructed a highly efficient adsorption and photocatalytic degradation system, enabling pollutants (such as anthracene, α, and dibenzo[a,h]anthracene) to be more effectively adsorbed and degraded under light conditions, thereby achieving efficient pollutant removal. In contrast, Example 3, which added only 2% sludge-TiO2 composite material to the surface layer, although also adding a certain proportion of sludge-TiO2 composite material to the base mixture, showed a slight improvement in adsorption efficiency compared to Example 2, but the effect was far inferior to Example 1.

[0092] Comparative Example 1, compared to Example 1, the following changes were made:

[0093] In the preparation process of the sludge biochar-TiO2 composite material in the surface layer, the weight ratio of industrial sludge biochar to titanium dioxide was changed from "5:1" to "1:1", while the rest remained the same as in Example 1. The photocatalytic performance of the material was determined according to the above test method. Considering the differences in the degradation effect of photocatalysis on polycyclic aromatic hydrocarbons (PAHs) with different ring numbers, three representative pollutants, namely 3-ring (anthracene), 4-ring (H), and 5-ring (dibenzo[a,h]anthracene), were selected for targeted analysis and detection.

[0094] The photocatalytic efficiency of the permeable bricks obtained in Comparative Example 1 is shown in Table 5.

[0095] Table 5

[0096] Simulated pollutants Pollutant content in permeable bricks Pollutant content after degradation Photocatalytic efficiency Anthracene 3.021 mg / kg 1.410 mg / kg 53.33% CHR 3.239 mg / kg 1.726 mg / kg 46.72% Dibenzo[a,h]anthracene-DBA 3.420 mg / kg 1.988 mg / kg 41.87%

[0097] When the amount of nano-TiO2 is too high, particle agglomeration is very likely to occur. This not only causes the active sites of the catalyst to be blocked, but also weakens the synergistic electron transfer effect between BC and nano-TiO2 because the pores of biochar (BC) cannot completely accommodate the excess nano-TiO2. Compared with Example 1, the photocatalytic efficiency will be significantly reduced in this case.

[0098] Comparative Example 2, compared to Example 1, makes the following changes:

[0099] The ratio of "biochar to nano-titanium dioxide 5:1" in the preparation process of the sludge-TiO2 composite material in the surface layer was changed to "biochar to nano-titanium dioxide 10:1", with the rest remaining the same as in Example 1. The photocatalytic performance of the material was determined according to the above test method. Considering the differences in the degradation effect of photocatalysis on polycyclic aromatic hydrocarbons (PAHs) with different ring numbers, three representative pollutants, namely 3-ring (anthracene), 4-ring (H), and 5-ring (dibenzo[a,h]anthracene), were selected for targeted analysis and detection.

[0100] The photocatalytic efficiency of the permeable bricks obtained in Comparative Example 2 is shown in Table 6.

[0101] Table 6

[0102] Simulated pollutants Pollutant content in permeable bricks Pollutant content after degradation Photocatalytic efficiency Anthracene 3.021 mg / kg 1.983 mg / kg 34.35% CHR 3.239 mg / kg 2.339 mg / kg 27.78% Dibenzo[a,h]anthracene-DBA 3.420 mg / kg 2.763 mg / kg 19.21%

[0103] When the amount of nano-TiO2 is insufficient, the number of active sites in the system is significantly lacking, making it difficult to effectively attack the aromatic ring structure of polycyclic aromatic hydrocarbons (PAHs). This effect is particularly pronounced for recalcitrant high-ring PAHs, and the photocatalytic efficiency shows a more significant decrease compared to Example 1.

[0104] Finally, it should be noted that the above examples are merely some specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments and many variations are possible. All variations that can be directly derived or conceived by those skilled in the art from the disclosure of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A method for preparing self-cleaning permeable bricks based on sludge biochar-TiO2 composite materials, characterized in that... Includes the following steps: 1) Preparation of sludge-TiO2 composite material: Industrial sludge biochar and nano-sized titanium dioxide were mixed at a mass ratio of (5±0.5):1 and then ground to obtain sludge biochar-TiO2 composite material. 2) Preparation of surface mixture: The surface mixture consists of the following components by mass percentage: 58%~63% quartz sand, 22%~25% river sand, 8%~12% sludge-carbon-TiO2 composite material, and 5% epoxy resin; 3) Preparation of base layer mixture: Weigh water and silicate cement according to the water-cement ratio (0.3±0.05), mix them evenly with basalt to obtain the base course mixture; the weight ratio of basalt to silicate cement is (4±0.2):

1. 4) Pour the base mixture obtained in step 3) into the mold, with a base mixture filling thickness of 40~60mm, and press statically; then pour the surface mixture obtained in step 2) onto the upper surface of the statically pressed base mixture, controlling the surface mixture filling thickness to 8~12mm, and then press statically; after curing, demold, and then cure under standard curing conditions for 28±3 days to obtain permeable bricks.

2. The method for preparing self-cleaning permeable bricks based on sludge biochar-TiO2 composite materials according to claim 1, characterized in that: Industrial sludge biochar was obtained by drying, grinding and screening industrial sludge as raw material and then pyrolyzing it at (500±20)℃ for (4±0.5) hours under an inert atmosphere.

3. The preparation method of the self-cleaning permeable brick based on sludge biochar-TiO2 composite material according to claim 2, characterized in that: The temperature was programmed to rise to (500±20)℃ at a heating rate of (10±2)℃ / min for pyrolysis.

4. The method for preparing self-cleaning permeable bricks based on sludge biochar-TiO2 composite materials according to any one of claims 1 to 3, characterized in that: Basalt has a mesh size of 4-8 mesh, quartz sand has a mesh size of 20-45 mesh, river sand has a mesh size of 8-100 mesh, and nano-titanium dioxide has a mesh size of 5-30 nm.

5. The method for preparing self-cleaning permeable bricks based on sludge biochar-TiO2 composite materials according to claim 4, characterized in that: The silicate cement is P.O 42.5R cement.

6. The method for preparing self-cleaning permeable bricks based on sludge biochar-TiO2 composite materials according to any one of claims 1 to 5, characterized in that... In step 4): The static pressure corresponding to the base course mix is: static pressure of 1MPa for 10~15s; The static pressure after adding the surface mixture is: static pressure of 3~5MPa for 45~60s; The standard maintenance conditions are: temperature 20±2℃, relative humidity ≥95%.

7. The self-cleaning permeable brick prepared by any one of claims 1 to 6, characterized in that: It is a self-cleaning permeable brick with a double-layer composite structure of base layer and surface layer.

Images