A multi-pore composite mineral cat litter and a preparation method and a recovery method thereof

Abstract

The present application relates to a kind of multi-stage pore composite mineral cat litter and its preparation method and recovery method, relate to cat litter technical field, to solve at least one of the problems such as insufficient adsorption amount of existing cat litter, poor catalytic decomposition ability to organic sulfide, environmental pollution, high cost, poor recycling ability etc..The present application realizes the targeted capture and efficient decomposition of multiple odor molecules in pet excrement by constructing gradient pore structure and biological-mineral composite deodorization system, and is suitable for feces management in scenes such as family pet care, stray animal rescue station and zoo.The specific cat litter core of the present application includes hierarchical porous diatomite, and modified sodium-based bentonite, to realize gradient adsorption and enrichment of odor molecules, and to promote the synergistic degradation of NH3, H2S and VOCs using a non-metallic catalytic-biological enzyme combined system.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of cat litter, in particular to a multi-level pore composite mineral cat litter and a preparation method and recovery method thereof. BACKGROUND

[0002] Pet cats are animals that many people like to raise. In the process of raising pet cats, if they excrete anywhere, it will cause great pollution. Using cat litter to catch these excretions can well solve this problem. There are many types of cat litter, such as plant fiber cat litter, sawdust cat litter, bentonite cat litter, etc. They can quickly wrap cat urine, form a cat urine ball, facilitate cleaning, and reduce the generation of foul odor.

[0003] However, the traditional bentonite cat litter has insufficient adsorption capacity, and quaternary ammonium salt bacteriostatic agents are added in commercially available products, which causes water body ecological toxicity. In addition, the proportion of particles with a particle size of <100 μm is >15%, which induces an annual increase of 12% in cases of respiratory diseases in pets; only physical adsorption is considered, and there is a lack of catalytic decomposition ability for organic sulfides. SUMMARY

[0004] In view of the above analysis, the present application aims to provide a multi-level pore composite mineral cat litter and a preparation method and recovery method thereof, to solve at least one of the problems of insufficient adsorption capacity of existing cat litter, poor catalytic decomposition ability for organic sulfides, environmental pollution, high cost, and poor recycling ability.

[0005] In a first aspect, the present application provides a multi-level pore composite mineral cat litter, which comprises, from the inside out, a water-absorbing inner core layer, a catalytic deodorizing intermediate layer, and a dust suppression outer shell layer.

[0006] The water-absorbing inner core layer is made of modified sodium-based bentonite, graded pore diatomite, and a binder, the catalytic deodorizing intermediate layer is made of MnO2-biochar composite material and laccase microcapsules, and the dust suppression outer shell layer is made of polyethylene glycol 2000 and nano-SiO2.

[0007] Further, the diameter of the water-absorbing inner core layer is 2.0-2.5 mm, the thickness of the catalytic deodorizing intermediate layer is 0.8-1.2 mm, and the thickness of the dust suppression outer shell layer is 0.2-0.5 mm.

[0008] Further, the graded pore diatomite has three levels of mesopores, namely 1-2 nm micropores, 5-20 nm mesopores, and 50-200 nm macropores.

[0009] Further, the mass ratio of the modified sodium-based bentonite to the graded pore diatomite is 3:1-6:1, and the mass of the binder accounts for 5-7% of the total mass of the modified sodium-based bentonite, the graded pore diatomite, and the binder.

[0010] Further, the mass ratio of the MnO2-biochar composite material and the laccase microcapsule is 2.5-3.5, and the laccase microcapsule is prepared by co-immobilization of laccase aqueous solution, trehalose and cross-linking agent.

[0011] In a second aspect, the present application provides a preparation method of the multi-level pore composite mineral cat litter, comprising the following steps:

[0012] (1) mixing sodium bentonite with sodium citrate solution, ultrasonic treatment, centrifugation, calcination to obtain modified sodium bentonite;

[0013] (2) crushing diatomite, sieving, then separating clay minerals, adding HCl solution, stirring reaction to form 1-2 nm micropores, then adding surfactant, self-assembly in ammonia environment to form 5-20 nm mesopores, then adding ammonium bicarbonate, pre-burning after compression molding to form a honeycomb-like skeleton, heating and holding reaction to form 50-200 nm macropores to obtain the hierarchical pore diatomite;

[0014] (3) oxidizing and cleaving biomass material to prepare biochar, then impregnating into Mn(NO3)2 solution after activation, and then hydrothermal reaction to obtain the MnO2-biochar composite material;

[0015] (4) mixing laccase aqueous solution with trehalose, adding into cross-linking agent, and freeze-drying to obtain the laccase microcapsule;

[0016] (5) mixing the modified sodium bentonite in step (1) and the hierarchical pore diatomite in step (2), adding binder, and granulating to obtain a water-absorbing inner core layer;

[0017] (6) mixing the MnO2-biochar composite material in step (3) and the laccase microcapsule in step (4), uniformly coating and depositing on the water-absorbing inner core layer to form a catalyst deodorization intermediate layer;

[0018] (7) heating and melting polyvinyl alcohol 2000, then adding nano-SiO2, stirring to form a uniform slurry, using electrostatic spraying process to spray the slurry on the catalyst deodorization intermediate layer to form a dust suppression outer shell layer, drying, and sieving to obtain the multi-level pore composite mineral cat litter.

[0019] Further, in step (2), the concentration of the HCl solution is 5-6 mol / L HCl, the solid-liquid ratio in the solution after adding HCl solution is 0.2-0.3, and the stirring reaction is carried out at 70-80℃ for 2-2.5 h.

[0020] Further, in step (2), the temperature is raised to 500-550℃ at a rate of 5-7℃ / min, and the holding time is 2-2.5h.

[0021] In a third aspect, the present application provides a multi-pore channel composite mineral cat litter recycling method as described above, comprising the following steps:

[0022] (a) The cat litter is first laid with a thickness of ≥5cm, and after cleaning the clumps every day, new sand is added to the original thickness;

[0023] (b) When the cumulative usage reaches 60% of the initial amount, all the cat litter is recycled;

[0024] (c) The recycled cat litter is crushed and regenerated by incineration at 400-450℃ to obtain regenerated cat litter;

[0025] (d) The regenerated cat litter is mixed with biochar, and flue gas is introduced for calcination, ball milling and crushing to obtain treated cat litter;

[0026] (e) The treated cat litter is added to unused multi-pore channel composite mineral cat litter for repeated use;

[0027] Or, the treated cat litter is used for garden slow-release fertilizer.

[0028] Further, in step (d), the NH3 adsorption capacity of the treated cat litter is 85% or more of the NH3 removal rate of the unused cat litter. Compared with the prior art, the present application can achieve at least one of the following beneficial effects:

[0029] (1) The present application realizes the targeted capture and efficient decomposition of multi-component odor molecules in pet excrement by constructing a gradient pore structure (graded pore diatomite) and a biological-mineral composite deodorization system, and is suitable for feces management in scenes such as family pet care, stray animal rescue stations and zoos. Specifically, the cat litter core of the present application includes graded pore diatomite and modified sodium-based bentonite, which realizes gradient adsorption and enrichment of odor molecules, and a non-metallic catalytic-biological enzyme combined system is used to promote the synergistic degradation of NH3, H2S and VOCs.

[0030] (2) The diameter of the water-absorbing core layer, the thickness of the intermediate layer and the thickness of the shell layer in the scope of the present application can reduce dust during transportation, and can quickly deodorize and continuously absorb water when combined with cat urine and cat feces.

[0031] (3) The preparation method of the cat litter of the present application uses a low-temperature forming process to prepare laccase microcapsules, which reduces production energy consumption while ensuring mechanical strength.

[0032] (4) The recycling method of the present application establishes a closed-loop waste treatment scheme, realizes the recycling of materials, and realizes the goal of zero waste.

[0033] The above technical solutions in the present application can also be combined with each other to realize more preferred combination solutions. Other features and advantages of the present application will be described in the subsequent specification, and some advantages will become apparent from the specification, or will be understood by implementing the present application. The purposes and other advantages of the present application can be realized and obtained from the contents specifically pointed out in the specification and the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0034] The accompanying drawings are included to provide a further understanding of the present application and are incorporated in and constitute a part of this specification, illustrate embodiments of the present application and serve to explain the principles of the present application, and are not intended to limit the scope of the present application.

[0035] Figure 1 SEM image of the hierarchical porous diatomite prepared for the present application embodiment 1;

[0036] Figure 2 SEM image of the MnO2-biochar composite material prepared for the present application embodiment 1. DETAILED DESCRIPTION

[0037] The preferred embodiments of the present application will be specifically described below in conjunction with the drawings, wherein the drawings constitute a part of the present application, and are used to illustrate the principles of the embodiments of the present application, and are not intended to limit the scope of the present application.

[0038] One specific embodiment of the present application discloses a multi-level pore composite mineral cat litter, which comprises, from inside to outside, a water-absorbing inner core layer, a catalytic deodorization intermediate layer and a dust suppression outer shell layer.

[0039] The water-absorbing inner core layer is made of modified sodium-based bentonite, hierarchical porous diatomite and a binder, the catalytic deodorization intermediate layer is made of MnO2-biochar composite material and laccase microcapsules, and the dust suppression outer shell layer is made of polyethylene glycol 2000 and nano-SiO2.

[0040] Compared with the prior art, the present application realizes the targeted capture and efficient decomposition of multiple odor molecules in pet excrement by constructing a gradient pore structure (hierarchical porous diatomite) and a biological-mineral composite deodorization system, and is suitable for feces management in scenes such as family pet care, stray animal rescue stations and zoos. Specifically, the cat litter core of the present application includes hierarchical porous diatomite, which cooperates with modified sodium-based bentonite to realize gradient adsorption and enrichment of odor molecules, and a non-metallic catalytic-biological enzyme combined system is used to promote the synergistic degradation of NH3, H2S and VOCs.

[0041] Specifically, the diameter of the water-absorbing inner core layer is 2.0-2.5 mm, the thickness of the catalytic deodorization intermediate layer is 0.8-1.2 mm, and the thickness of the dust suppression outer shell layer is 0.2-0.5 mm.

[0042] It should be noted that the diameter of the water-absorbing inner core layer, the thickness of the intermediate layer, and the thickness of the outer shell layer of the present application are within the above-mentioned ranges, which can reduce dust during transportation of the cat litter and quickly deodorize and continuously absorb water when combined with cat urine and cat feces.

[0043] Specifically, the hierarchical pore diatomite has three types of mesopores, i.e., 1-2 nm micropores, 5-20 nm mesopores, and 50-200 nm macropores.

[0044] Specifically, the mass ratio of the modified sodium-based bentonite to the hierarchical pore diatomite is 3:1-6:1, and the mass of the binder accounts for 5-7% of the total mass of the modified sodium-based bentonite, the hierarchical pore diatomite, and the binder.

[0045] Preferably, the binder is a mixture of hydroxypropyl starch (HPS), polyvinyl alcohol (PVA1788), and silica sol in a ratio of 6-11:3-5:1-4, followed by addition of a crosslinking agent and a plasticizer and stirring at 65-70°C.

[0046] Preferably, the mass of the crosslinking agent is 3-5% of the mass of the binder, and the mass of the plasticizer is 0.1-0.3% of the mass of the binder.

[0047] More preferably, the crosslinking agent is trisodium citrate, and the plasticizer is glycerol.

[0048] Specifically, the loading amount of the MnO2-biochar composite material is 30-35%, which helps the uniform dispersion of MnO2 nanosheets on the surface of biochar, avoids the aggregation of MnO2, and thus better maintains the high specific surface area and porous structure of the material. Such a structure is beneficial to increasing active sites, improving catalytic performance, and enhancing the stability of the material to prevent MnO2 from falling off or deactivating during use.

[0049] The MnO2-biochar composite material is δ-MnO2 nanosheets grown in situ on the surface of biochar, which improves the specific surface area and the catalytic efficiency of NH3.

[0050] Specifically, the mass ratio of the MnO2-biochar composite material to the laccase microcapsule is 2.5-3.5.

[0051] Specifically, the laccase microcapsule is prepared by co-immobilization of a laccase aqueous solution, trehalose, and a crosslinking agent.

[0052] Preferably, the mass ratio of the laccase aqueous solution and trehalose is 1:3-1:5, and the mass of the crosslinking agent is 0.5-1.0% of the total mass of the laccase aqueous solution, trehalose and crosslinking agent.

[0053] More preferably, the mass concentration of the laccase aqueous solution is 200-250 U / mg, the crosslinking agent is a chitosan acetic acid solution, and the mass fraction of chitosan in the acetic acid is 0.5-2%.

[0054] More preferably, the laccase microcapsule is a porous microsphere with a diameter of 50-100 μm, and the porosity of the microsphere is ≥75%.

[0055] It should be noted that the laccase microcapsule of the present application is prepared by enzyme immobilization technology, and is protected by trehalose and chitosan, so that the activity retention rate of laccase is >85% after being stored at 50℃ for 6 months.

[0056] Preferably, the particle size of the nano-SiO2 is 20-50 nm.

[0057] Another specific embodiment of the present application discloses a preparation method of the above-mentioned multi-level pore composite mineral cat litter, comprising the following steps:

[0058] (1) mixing sodium-based bentonite with a sodium citrate solution, ultrasonic treatment, centrifugation, calcination, to obtain modified sodium-based bentonite;

[0059] (2) crushing diatomite, sieving, then separating clay minerals, adding HCl solution, stirring and reacting to form 1-2 nm micropores, then adding a surfactant, self-assembling in an ammonia environment to form 5-20 nm mesopores, then adding ammonium bicarbonate, and pre-burning after compression molding to form a honeycomb-like framework, then heating and keeping warm to react to form 50-200 nm macropores, to obtain the hierarchical pore diatomite;

[0060] (3) oxidatively cleaving biomass material to prepare biochar, then impregnating the activated biochar into a Mn(NO3)2 solution, and then performing hydrothermal reaction to obtain a MnO2-biochar composite material;

[0061] (4) mixing a laccase aqueous solution with trehalose, and adding to a crosslinking agent, and then freeze-drying to obtain the laccase microcapsule;

[0062] (5) mixing the modified sodium-based bentonite in step (1) and the hierarchical pore diatomite in step (2), and then adding a binder and granulating to obtain a water-absorbing inner core layer;

[0063] (6) mixing the MnO2-biochar composite material in step (3) and the laccase microcapsule in step (4), and then uniformly coating and depositing on the water-absorbing inner core layer to form a catalyst deodorization intermediate layer.

[0064] (7) heating and melting polyvinyl alcohol 2000, adding nano-SiO2, stirring to form a uniform slurry, using electrostatic spraying process to spray the slurry on the catalyst deodorization intermediate layer to form a dust suppression outer shell layer, drying, screening, and obtaining the multi-stage pore composite mineral cat litter.

[0065] Specifically, in step (1), the concentration of sodium citrate in the sodium citrate solution is 3-5 mol / L, and the sodium citrate solution has good dispersibility in this range, which can effectively disperse the sodium bentonite uniformly in the solution and prevent particle agglomeration. The mass ratio of sodium bentonite to sodium citrate solution is 0.25-0.35.

[0066] Preferably, the sodium bentonite contains Al2O3≥28%.

[0067] Specifically, in step (1), the ultrasonic treatment temperature is 70-80℃, the ultrasonic treatment time is 50-60 min, and the ultrasonic frequency is 30-40 kHz. Under the above ultrasonic conditions, the activity of sodium ions is stimulated, and the reaction is more complete.

[0068] Specifically, in step (1), the calcination atmosphere is nitrogen, the calcination temperature is 400-450℃, and the calcination time is 2-2.5 h.

[0069] Specifically, in step (2), the diatomite is crushed to a particle size of <100 μm and treated with a 200 mesh screen.

[0070] It should be noted that the present application removes large particle impurities by a vibrating screen and separates clay minerals using a hydrocyclone to increase the SiO2 content to >70%.

[0071] Specifically, in step (2), the concentration of the HCl solution is 5-6 mol / L HCl, the solid-liquid ratio in the solution after adding the HCl solution is 0.2-0.3, and the solution is stirred and reacted at 70-80℃ for 2-2.5 h.

[0072] The purpose of the above operation is to remove metal oxides such as Fe2O3 and selectively dissolve amorphous silicon to form 1-2 nm micropores.

[0073] Specifically, in step (2), the surfactant is CTAB, and the mass of the surfactant is 3-4% of the diatomite.

[0074] Preferably, the pH value of the ammonia water is 10-10.5, at which time the ammonia water is closest to cat urine, and the self-assembly reaction is 23-24 h.

[0075] Specifically, in step (2), the ammonium bicarbonate is added in an amount of 10-15% of the mass of the diatomite, the pre-burning temperature is 300-320℃, and the time is 1-1.5h.

[0076] Specifically, in step (2), the temperature is raised to 500-550℃ at a rate of 5-7℃ / min, and the holding time is 2-2.5h. Under the above temperature conditions, the molecules inside the diatomite can be fully activated and have activity.

[0077] Specifically, in step (3), the temperature for oxidative cleavage is 550-600℃, and the time is 15-20min.

[0078] Preferably, in step (3), HNO3 is used for activation, the mass fraction of the Mn(NO3)2 solution is 30-35%, and the mass ratio of the biomass material, HNO3 and the Mn(NO3)2 solution is 6-7:1:14-12.

[0079] Preferably, the biomass material includes walnut shells and / or rice husks.

[0080] Specifically, in step (3), the temperature for the hydrothermal reaction is 160-180℃, and the time is 11-12h. The above temperature can provide heat energy, so that the intermolecular motion is faster and the reaction is accelerated to complete.

[0081] Specifically, in step (4), the freeze-drying temperature is -30--40℃, and the drying time is 24-36h.

[0082] Specifically, in step (5), the granulation is performed by using a double-screw extruder with a length-diameter ratio of 40:1 and a die temperature of 60-70℃.

[0083] Specifically, in step (6), the uniform coating is performed by using a fluidized bed bottom spraying process.

[0084] Preferably, the fluidized bed process parameters are as follows: the fluidization gas velocity is 0.8-1.2m / s, the efficiency of coating deposition is ≥90%, the coating cycle is 3-5 times, and the interval drying time is 5-10min each time.

[0085] Preferably, the inlet air temperature is 70-80℃, and the atomization pressure is 0.2-0.3MPa.

[0086] Specifically, in step (6), the mass of the catalyst deodorization intermediate layer is 10-20% of the mass of the water-absorbing inner core layer.

[0087] Specifically, in step (7), the mass of the dust suppression outer shell layer is 3-5% of the total mass of the water-absorbing inner core layer and the catalyst deodorization intermediate layer.

[0088] Specifically, in step (7), the drying temperature is 50-60 DEG C, and the mesh size is 8-35 mesh.

[0089] Specifically, in step (7), the electrostatic spraying process parameters are as follows: slurry solid content 12-15%, spraying distance 150-200 mm, and deposition electric field strength 4-6 kV / cm.

[0090] The preparation method of the cat litter of the present application adopts a low-temperature forming process for preparing the laccase microcapsules, thereby reducing the production energy consumption while ensuring the mechanical strength.

[0091] Another specific embodiment of the present application discloses a recycling method of the above-mentioned multi-level pore composite mineral cat litter, comprising the following steps:

[0092] (a) first laying the cat litter with a thickness of no less than 5 cm, and supplementing new litter to the original thickness after cleaning the clumped material every day;

[0093] (b) when the cumulative usage reaches 60% of the initial amount, recycling all the cat litter;

[0094] (c) crushing the recycled cat litter, incinerating and regenerating the cat litter at 400-450 DEG C to obtain regenerated cat litter;

[0095] (d) mixing the regenerated cat litter with biochar, introducing flue gas, calcining, ball milling and crushing to obtain treated cat litter;

[0096] (e) adding the treated cat litter to unused multi-level pore composite mineral cat litter for repeated use;

[0097] Or, the treated cat litter is used for garden slow-release fertilizer.

[0098] Specifically, in step (d), the mass of the biochar is 5-8% of the mass of the used multi-level pore composite mineral cat litter.

[0099] Specifically, in step (d), the oxygen content of the flue gas is 8-10%, the calcination temperature is 380-420 DEG C, and the calcination time is 30-45 min.

[0100] Preferably, in step (d), the NH3 adsorption capacity of the treated cat litter is more than 85% of the NH3 adsorption capacity of the unused cat litter. 3去除率

[0101] Specifically, in step (d), the crushing is to 200-250 mesh.

[0102] Specifically, in step (e), the mass of the treated cat litter is 20-30% of the mass of the unused multi-level pore composite mineral cat litter.

[0103] ​The recycling method of the application establishes a closed-loop waste treatment scheme, realizes recycling of materials, and realizes a zero waste target.

[0104] The raw materials in the application are commercially available or prepared by existing methods, and the technical solutions of the application are further explained in combination with specific examples.

[0105] Example 1

[0106] The preparation method of the multi-level pore composite mineral cat litter of the embodiment comprises the following steps:

[0107] (1) Mix sodium-based bentonite with Al2O3≥28% and 5 mol / L sodium citrate solution according to a mass ratio of 1:4, ultrasonic treat for 60 min at a temperature of 80°C and an ultrasonic frequency of 40 kHz, centrifuge to obtain exfoliated nanosheets, calcine under a nitrogen atmosphere at 450°C for 2.5 h, and obtain modified sodium-based bentonite;

[0108] (2) Crush diatomite to <100 μm, treat with a 200-mesh screen, separate clay minerals by using a hydrocyclone, add 6 mol / L HCl solution so that the solid-liquid ratio in the solution is 1:5, stir and react at 80°C for 2.5 h to form 1-2 nm micropores, then add a surfactant CTAB, the mass of the surfactant is 3% of the diatomite, self-assemble in an ammonia water environment with pH=10.5 for 24 h to form 5-20 nm mesopores, then add ammonium bicarbonate, the addition amount of the ammonium bicarbonate is 15% of the mass of the diatomite, press into shape, pre-burn at 300°C for 1 h to form a honeycomb-like framework, heat to 550°C at a heating rate of 5°C / min under nitrogen protection and keep the temperature for 2 h to form 50-200 nm macropores, and obtain the hierarchical pore diatomite;

[0109] (3) Oxidize and crack walnut shells at 600°C for 20 min to prepare biochar, dip the biochar into a Mn(NO3)2 solution after activating by HNO3, the mass fraction of the Mn(NO3)2 solution is 35%, the mass ratio of the walnut shells, HNO3 and the Mn(NO3)2 solution is 7:1:12, and the biochar is subjected to hydrothermal reaction at 180°C for 12 h to obtain a MnO2-biochar composite material;

[0110] (4) Mix a laccase aqueous solution and trehalose, the mass ratio of the laccase aqueous solution and trehalose is 1:4, the mass concentration of the laccase aqueous solution is 225 U / mg, add to a crosslinking agent, freeze-dry at -40°C for 30 h, and obtain the laccase microcapsule;

[0111] The cross-linking agent is chitosan acetic acid solution, the mass fraction of chitosan in acetic acid is 2%, the laccase microcapsule is a porous microsphere with a diameter of 50-100 μm, and the porosity of the microsphere is greater than or equal to 75%;

[0112] (5) The modified sodium bentonite in step (1) and the hierarchical pore diatomite in step (2) are mixed, a binder is added, the mass ratio of the modified sodium bentonite to the hierarchical pore diatomite is 4.5:1, the mass of the binder accounts for 6% of the total mass of the modified sodium bentonite, the hierarchical pore diatomite and the binder, granulation is performed, and a water-absorbing inner core layer is obtained;

[0113] The binder is a mixture of hydroxypropyl starch (HPS), polyvinyl alcohol (PVA1788) and silica sol in a mass ratio of 6:3:1, and then a cross-linking agent trisodium citrate and a plasticizer glycerol are added and stirred at 70°C, the mass of the cross-linking agent accounts for 5% of the mass of the binder, and the mass of the plasticizer accounts for 0.1% of the mass of the binder;

[0114] (6) The MnO2-biochar composite material in step (3) and the laccase microcapsule in step (4) are mixed in a mass ratio of 3:1, and are uniformly coated and deposited on the water-absorbing inner core layer by using a fluidized bed bottom spraying process, the fluidized bed process parameters are as follows: the inlet air temperature is 80°C, the atomization pressure is 0.3 MPa, the fluidization gas velocity is 1.0 m / s, the coating and deposition efficiency is greater than or equal to 90%, the coating and deposition cycle is 3-5 times, and the drying interval is 5-10 min each time, a catalyst deodorization intermediate layer is formed;

[0115] The mass of the catalyst deodorization intermediate layer accounts for 15% of the mass of the water-absorbing inner core layer;

[0116] (7) Polyvinyl alcohol 2000 is heated and melted, nano-SiO2 is added, and stirring is performed to form a uniform slurry, the solid content of the slurry is 13.5%, the slurry is sprayed on the catalyst deodorization intermediate layer by using an electrostatic spraying process, the spraying distance is 175 mm, and the deposition electric field strength is 5 kV / cm, a dust suppression outer shell layer is formed, the mass of the dust suppression outer shell layer accounts for 4% of the total mass of the water-absorbing inner core layer and the catalyst deodorization intermediate layer, drying is performed at a temperature of 55°C until the water content is less than or equal to 10%, and the dust suppression outer shell layer is screened by using a vibrating screen with a mesh number of 8-10 meshes, and the multi-level pore composite mineral cat litter is obtained.

[0117] The diameter of the water-absorbing inner core layer of the cat litter obtained in the example is 2.25 mm, the thickness of the catalyst deodorization intermediate layer is 1.0 mm, and the thickness of the dust suppression outer shell layer is 0.35 mm.

[0118] The SEM of the hierarchical pore diatomite prepared in the example is as follows:Figure 1 As shown in FIG. 2, the SEM of the MnO2-biochar composite material is as shown in FIG. 3. Figure 2 As shown in FIG. 3, it can be seen that the δ-MnO2nanosheet is loaded on the surface of the biochar.

[0119] Embodiment 2

[0120] The preparation method of the multi-level pore composite mineral cat litter of the embodiment comprises the following steps:

[0121] (1) The sodium-based bentonite with Al2O3≥28% is mixed with a 4 mol / L sodium citrate solution according to a mass ratio of 2:7, ultrasonic treatment is performed at a temperature of 75°C and an ultrasonic frequency of 35 kHz for 55 min, centrifugation is performed to obtain exfoliated nanosheets, and calcination is performed under a nitrogen atmosphere at 425°C for 2.25 h to obtain modified sodium-based bentonite;

[0122] (2) The diatomite is crushed to <100 μm, treated by passing through a 200-mesh screen, and clay minerals are separated by using a hydrocyclone, 5.5 mol / L HCl solution is added, the solid-liquid ratio in the solution is 1:4, stirring reaction is performed at 75°C for 2.25 h to form micropores of 1-2 nm, a surfactant CTAB is added, the mass of the surfactant is 3.5% of the diatomite, self-assembly is performed in an ammonia environment with pH=10 for 23.5 h to form mesopores of 5-20 nm, ammonium bicarbonate is added, the addition amount of the ammonium bicarbonate is 15% of the mass of the diatomite, the mixture is formed into a shape, pre-burning is performed at 310°C for 1.25 h to form a honeycomb-like skeleton, the temperature is increased to 550°C at a rate of 6°C / min under nitrogen protection, and heat preservation reaction is performed for 2.25 h to form macropores of 50-200 nm, and the hierarchical pore diatomite is obtained;

[0123] (3) The walnut shell is oxidized and cracked at 550°C for 17.5 min to prepare biochar, the biochar is immersed in a Mn(NO3)2solution after being activated by HNO3, the mass fraction of the Mn(NO3)2solution is 30.25%, and the mass ratio of the walnut shell, HNO3, and the Mn(NO3)2solution is 13:2:25, and the hydrothermal reaction is performed at 170°C for 11.5 h to obtain the MnO2-biochar composite material;

[0124] (4) The laccase aqueous solution is mixed with trehalose, the mass ratio of the laccase aqueous solution and the trehalose is 1:3, the mass concentration of the laccase aqueous solution is 200 U / mg, the mixture is added to a crosslinking agent, and freeze-drying is performed at -35°C for 24 h to obtain the laccase microcapsule;

[0125] The crosslinking agent is chitosan acetic acid solution, the mass fraction of chitosan in acetic acid is 1.25%, the laccase microcapsule is a porous microsphere with a diameter of 50-100 mu m, and the porosity of the microsphere is greater than or equal to 75%;

[0126] (5) The modified sodium bentonite in step (1) and the hierarchical pore diatomite in step (2) are mixed, a binder is added, the mass ratio of the modified sodium bentonite to the hierarchical pore diatomite is 3:1, the mass of the binder accounts for 5% of the total mass of the modified sodium bentonite, the hierarchical pore diatomite and the binder, granulation is performed, and a water-absorbing inner core layer is obtained;

[0127] The binder is a mixture of hydroxypropyl starch (HPS), polyvinyl alcohol (PVA1788) and silica sol in a ratio of 9:4:4, and then a crosslinking agent trisodium citrate and a plasticizer glycerol are added and stirred at 67.5 DEG C, the mass of the crosslinking agent accounts for 4% of the mass of the binder, and the mass of the plasticizer accounts for 0.2% of the mass of the binder;

[0128] (6) The MnO2-biochar composite material in step (3) and the laccase microcapsule in step (4) are mixed in a mass ratio of 2.5:1, are uniformly coated and deposited on the water-absorbing inner core layer by using a fluidized bed bottom spraying process, the fluidized bed process parameters are that the inlet air temperature is 75 DEG C, the atomization pressure is 0.25 MPa, the fluidization gas velocity is 0.8 m / s, the coating and deposition efficiency is greater than or equal to 90%, the coating and deposition cycle is 3-5 times, each time is interval dried for 5-10 min, and a catalyst deodorization intermediate layer is formed;

[0129] The mass of the catalyst deodorization intermediate layer accounts for 10% of the mass of the water-absorbing inner core layer;

[0130] (7) Polyvinyl alcohol 2000 is heated and melted, nano-SiO2 is added, and a uniform slurry is formed by stirring, the solid content of the slurry is 12%, the slurry is sprayed on the catalyst deodorization intermediate layer by using an electrostatic spraying process, the spraying distance is 150 mm, and the deposition electric field strength is 4 kV / cm, a dust suppression outer shell layer is formed, the mass of the dust suppression outer shell layer accounts for 3% of the total mass of the water-absorbing inner core layer and the catalyst deodorization intermediate layer, the dust suppression outer shell layer is dried at a temperature of 50 DEG C until the water content is less than or equal to 10%, and the dust suppression outer shell layer is screened through a vibrating screen with a mesh number of 8-10 meshes, and the multi-level pore composite mineral cat litter is obtained.

[0131] The diameter of the water-absorbing inner core layer of the cat litter obtained in the example is 2.0 mm, the thickness of the catalyst deodorization intermediate layer is 0.8 mm, and the thickness of the dust suppression outer shell layer is 0.2 mm.

[0132] Example 3

[0133] The preparation method of the multi-level pore composite mineral cat litter of the embodiment comprises the following steps:

[0134] (1) The sodium-based bentonite with Al2O3≥28% is mixed with 3 mol / L sodium citrate solution according to the mass ratio of 1:3, ultrasonic treatment is performed at the temperature of 70°C and the ultrasonic frequency of 30 kHz for 50 min, centrifugation is performed to obtain the exfoliated nanosheet, calcination is performed at 400°C for 2 h under the nitrogen atmosphere, and the modified sodium-based bentonite is obtained;

[0135] (2) The diatomite is crushed to <100 μm, treated by passing through a 200-mesh screen, and clay minerals are separated by using a hydrocyclone, 5 mol / L HCl solution is added, the solid-liquid ratio in the solution is 1:4, stirring reaction is performed at 70°C for 2 h to form 1-2 nm micropores, 2% surfactant CTAB is added, self-assembly is performed in the ammonia water environment with pH = 9.5 for 23 h to form 5-20 nm mesopores, ammonium bicarbonate is added, the addition amount of the ammonium bicarbonate is 10% of the mass of the diatomite, and after being pressed into a shape, pre-burning is performed at 320°C for 1.5 h to form a honeycomb-like skeleton, the temperature is increased to 550°C at a temperature increase rate of 7°C / min under the nitrogen protection, and heat preservation reaction is performed for 2 h to form 50-200 nm macropores, and the hierarchical pore diatomite is obtained;

[0136] (3) The walnut shell is oxidized and cracked at 600°C for 15 min to prepare biochar, the biochar is immersed into the Mn(NO3)2 solution after being activated by HNO3, the mass fraction of the Mn(NO3)2 solution is 30%, the mass ratio of the walnut shell, HNO3 and the Mn(NO3)2 solution is 6:1:14, and hydrothermal reaction is performed at 160°C for 11 h to obtain the MnO2-biochar composite material;

[0137] (4) The laccase aqueous solution is mixed with trehalose, the mass ratio of the laccase aqueous solution and trehalose is 1:3, the mass concentration of the laccase aqueous solution is 250 U / mg, the laccase aqueous solution and trehalose are added into the crosslinking agent, and freeze-drying is performed at -30°C for 36 h to obtain the laccase microcapsule;

[0138] The mass of the crosslinking agent is 1.0% of the total mass of the laccase aqueous solution, trehalose and the crosslinking agent, the crosslinking agent is chitosan acetic acid solution, the mass fraction of the chitosan in the acetic acid is 0.5%, and the laccase microcapsule is a porous microsphere with the diameter of 50-100 μm, and the porosity of the microsphere is ≥75%;

[0139] (5) mixing the modified sodium bentonite in step (1) and the hierarchical porous diatomite in step (2), adding a binder, the mass ratio of the modified sodium bentonite to the hierarchical porous diatomite being 6:1, the mass of the binder accounting for 7% of the total mass of the modified sodium bentonite, the hierarchical porous diatomite and the binder, granulating to obtain a water-absorbing inner core layer;

[0140] The binder is a mixture of hydroxypropyl starch (HPS), polyvinyl alcohol (PVA1788) and silica sol in a ratio of 11:5:4, and then a crosslinking agent trisodium citrate and a plasticizer glycerol are added and stirred at 65°C, the mass of the crosslinking agent being 3% of the mass of the binder, and the mass of the plasticizer being 0.3% of the mass of the binder.

[0141] (6) mixing the MnO2-biochar composite material in step (3) and the laccase microcapsule in step (4) according to a mass ratio of 3.5:1, uniformly coating and depositing on the water-absorbing inner core layer by using a fluidized bed bottom spraying process, the fluidized bed process parameters being: inlet air temperature 70°C, atomization pressure 0.2 MPa, fluidization gas velocity 1.2 m / s, the efficiency of coating and depositing being ≥90%, the coating and depositing cycle being 3-5 times, and each time being separated by drying for 5-10 min, to form a catalyst deodorization intermediate layer;

[0142] The mass of the catalyst deodorization intermediate layer is 20% of the mass of the water-absorbing inner core layer.

[0143] (7) heating and melting polyvinyl alcohol 2000, adding nano-SiO2, stirring to form a uniform slurry, the solid content of the slurry being 15%, using an electrostatic spraying process, the spraying distance being 200 mm, the deposition electric field strength being 6 kV / cm, spraying the slurry on the catalyst deodorization intermediate layer to form a dust suppression outer shell layer, controlling the mass of the dust suppression outer shell layer to be 5% of the total mass of the water-absorbing inner core layer and the catalyst deodorization intermediate layer, drying at a temperature of 60°C until the water content is ≤10%, and screening through a vibrating screen with a mesh number of 8-10 meshes to obtain the multi-level pore composite mineral cat litter.

[0144] The diameter of the water-absorbing inner core layer of the cat litter obtained in this example is 2.5 mm, the thickness of the catalyst deodorization intermediate layer is 1.2 mm, and the thickness of the dust suppression outer shell layer is 0.5 mm.

[0145] Example 4

[0146] A recycling method of the cat litter prepared in Example 1, comprising the following steps:

[0147] (a) first laying the cat litter prepared in Example 1 to a thickness ≥5 cm, and supplementing new sand to the original thickness after cleaning the clumps every day;

[0148] (b) when the cumulative amount of use reaches 60% of the initial amount, all of the cat litter is recovered;

[0149] (c) the recovered cat litter is broken up and incinerated at 400°C to regenerate the cat litter;

[0150] (d) the regenerated cat litter is mixed with walnut shells, and is calcined at a temperature of 380°C for 45 min in flue gas with an oxygen content of 8%, and is ball-milled to 200 mesh to obtain treated cat litter;

[0151] (e) the treated cat litter is added to unused multi-level pore composite mineral cat litter prepared in Example 1, and the mass of the treated cat litter is 25% of the mass of the unused multi-level pore composite mineral cat litter, and is reused.

[0152] Example 5

[0153] A method for recycling cat litter prepared in Example 2, comprising the following steps:

[0154] (a) the cat litter prepared in Example 2 is first laid to a thickness of ≥5 cm, and after daily cleaning of clumps, new sand is added to the original thickness;

[0155] (b) when the cumulative amount of use reaches 60% of the initial amount, all of the cat litter is recovered;

[0156] (c) the recovered cat litter is broken up and incinerated at 425°C to regenerate the cat litter;

[0157] (d) the regenerated cat litter is mixed with walnut shells, and is calcined at a temperature of 400°C for 37 min in flue gas with an oxygen content of 9%, and is ball-milled to 200 mesh to obtain treated cat litter;

[0158] (e) the treated cat litter is added to unused multi-level pore composite mineral cat litter prepared in Example 2, and the mass of the treated cat litter is 20% of the mass of the unused multi-level pore composite mineral cat litter, and is reused.

[0159] Example 6

[0160] A method for recycling cat litter prepared in Example 3, comprising the following steps:

[0161] (a) the cat litter prepared in Example 3 is first laid to a thickness of ≥5 cm, and after daily cleaning of clumps, new sand is added to the original thickness;

[0162] (b) when the cumulative amount of use reaches 60% of the initial amount, all of the cat litter is recovered;

[0163] (c) the recovered cat litter is broken up and incinerated at 420°C to regenerate the cat litter;

[0164] (d) mixing the regenerated cat litter with walnut shells, passing the mixture into flue gas with an oxygen content of 8%, calcining at a temperature of 420°C for 30 min, and ball-milling to 200 mesh to obtain treated cat litter;

[0165] (e) adding the treated cat litter to unused multi-level pore composite mineral cat litter prepared in Example 3, the mass of the treated cat litter being 30% of the mass of the unused multi-level pore composite mineral cat litter, and recycling.

[0166] Example 7

[0167] A recycling method for cat litter, similar to Example 4, except that in step (e), the treated cat litter is used for garden slow-release fertilizer.

[0168] Comparative Example 1

[0169] The preparation method of the cat litter of the present comparative example is similar to Example 1, except that in step (1), the sodium-based bentonite is not modified.

[0170] Comparative Example 2

[0171] The preparation method of the cat litter of the present comparative example is similar to Example 1, except that in step (2), the diatomite is not treated, i.e., the diatomite is directly used as a raw material for the cat litter.

[0172] Comparative Example 3

[0173] The preparation method of the cat litter of the present comparative example is similar to Example 1, except that step (3) is removed, i.e., the MnO2-biochar composite material is not added to the catalyst deodorizing layer, and only laccase microcapsules are present.

[0174] Comparative Example 4

[0175] The preparation method of the cat litter of the present comparative example is similar to Example 1, except that in step (5), no binder is added.

[0176] Comparative Example 5

[0177] The preparation method of the cat litter of the present comparative example is similar to Example 1, except that in step (5), the binder is hydroxypropyl starch.

[0178] Comparative Example 6

[0179] The preparation method of the cat litter of the present comparative example is similar to Example 1, except that in step (7), no nano-SiO2 is added.

[0180] Comparative Example 7

[0181] The cat litter of the present comparative example was prepared in a similar manner to Example 1, except that in step (5), the mass ratio of the modified sodium bentonite to the hierarchical pore diatomite was 7:1, and in step (6), the coating cycle was 1-2 times. The diameter of the water-absorbing core layer of the finally prepared cat litter was 1.5 mm, the thickness of the catalytic deodorizing intermediate layer was 0.6 mm, and the thickness of the dust suppression outer shell layer was 0.5 mm.

[0182] Test Example 1

[0183] (1) Deodorization effect evaluation

[0184] The deodorization effects of the cat litter prepared in Examples 1-3 and Comparative Examples 1-7 were tested respectively. The test method was as follows: according to ISO17226-3:2023, standard odor gas (NH350ppm, H2S20ppm, butyl acetate 30ppm) was injected into a 30L closed cabin, and the concentration change was monitored by gas chromatography-mass spectrometry (GC-MS). The test results are shown in Table 1.

[0185] Table 1

[0186]

[0187]

[0188] The NH3 removal rate (24h) of the cat litter of the present application was 89.2-96.5%, the H2S removal rate (24h) was 90.8-98.1%, the VOC removal rate (24h) was 78.6-85.4%, and the long-term effectiveness (7-day rebound rate) was 8.3-15.7%.

[0189] Comparative Examples 1-2 were compared with Example 1 respectively. The sodium-based bentonite and diatomite without modification had smaller NH3 and H2S removal rates, indicating that the production process needed to be modified.

[0190] Comparative Examples 3-6 were compared with Example 1 respectively. The NH3 and H2S removal rates were smaller in turn without adding MnO2-biochar composite material, binder, not using the binder of the present application, and nano-SiO2, indicating that the above-mentioned substances were indispensable in the production process, and also indicating that the binder obtained by mixing and proportioning had better effect.

[0191] Comparative Example 7 was compared with Example 1 respectively, indicating that the thickness of the inner, intermediate and outer layers was too large or too small, which was not conducive to the removal of odor of the cat litter.

[0192] (2) Physical property test

[0193] The physical properties of the cat litter prepared in Examples 1-3 and Comparative Examples 1-7 were tested respectively, and the test standards were as follows:

[0194] Pellet strength: ASTM D642, measured after simulated urine (1% urea + 0.5% NaCl) infiltration;

[0195] Dust emission: GB / T 16913-2022, PM2.5 generation amount was detected using APS 3321 type particle size spectrometer;

[0196] Water absorption rate: GB / T 8810-2023, record the time required for 10g sample to completely absorb water;

[0197] Bulk density: HG / T2825-2009, tested using bulk density tester. The test results are shown in Table 2.

[0198] Table 2

[0199]

[0200] The cat litter of the present application has a pellet strength of 12.6-15.2N, PM2.5 emission of 1.8-3.2(mg / m 3 ), water absorption time of 23-30s, and bulk density of 0.68-0.72g / cm 3 .

[0201] Comparative Examples 1-2, respectively, compared with Example 1, the unmodified sodium bentonite, diatomite pellet strength decreased, PM2.5 emission increased, water absorption time increased, indicating that the sodium bentonite, diatomite modification treatment helps to optimize the performance of cat litter.

[0202] Comparative Examples 3-6, respectively, compared with Example 1, in turn, without adding MnO2-biochar composite material, binder, not using the binder of the present application, nano-SiO2 diatomite pellet strength decreased, PM2.5 emission increased, water absorption time increased, indicating that the above-mentioned substances are indispensable in the production process, also indicating that the mixed binder has better effect.

[0203] Comparative Example 7, compared with Example 1, shows that the performance of cat litter with a thickness of water-absorbing core layer and catalytic deodorizing intermediate layer outside the scope of the present application is poor.

[0204] (3) Environmental safety assessment

[0205] The safety performance of cat litter prepared in Examples 1-3 was tested respectively.

[0206] First, according to the standard GB 15193.3-2014, the acute oral toxicity of cat litter prepared in Examples 1-3 was tested respectively, and the LD50 was >5000mg / kg, which belonged to the actual non-toxic level.

[0207] Second, according to standard EPA6010D, the heavy metal migration of the cat litter prepared in Examples 1-3 was tested respectively, 2. Pb < 2 ppm, Cd < 0.5 ppm, which met the EN71-3 standard;

[0208] Third, according to standard OECD 301B, the biodegradability of the cat litter prepared in Examples 1-3 was tested respectively, and the degradation rate in 28 days could be ≥ 88%, which was significantly better than ordinary mineral cat litter (< 5%).

[0209] Test Example 2

[0210] According to standard GB / T 18883-2022, the NH3 adsorption capacity of the cat litter after treatment in Examples 4-6 and the NH3 adsorption capacity of the cat litter prepared in Examples 1-3 were tested according to the method of Test Example 1, and the results are shown in Table 3.

[0211] Table 3

[0212]

[0213] By comparing Example 4 with Example 1, Example 5 with Example 2, and Example 6 with Example 3, it can be known that the NH3 removal rate (24h) of the cat litter treated by the method of the present application is 90.2-93.8% of that of the untreated cat litter.

[0214] The above description is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any changes or replacements within the technical range disclosed by the present application can be easily thought by those skilled in the art, which should be covered within the protection scope of the present application.

Claims

1. A multi-pore composite mineral cat litter, characterized by, The cat litter comprises, from inside to outside, a water-absorbing inner core layer, a catalytic deodorization intermediate layer and a dust suppression outer shell layer. The water-absorbing inner core layer is made of modified sodium bentonite, hierarchical pore diatomite and a binder, the catalytic deodorization intermediate layer is made of MnO2-biochar composite material and laccase microcapsules, and the dust suppression outer shell layer is made of polyethylene glycol 2000 and nano-SiO2.

2. The multi-pore composite mineral cat litter according to claim 1, wherein, The diameter of the water-absorbing inner core layer is 2.0-2.5 mm, the thickness of the catalytic deodorization intermediate layer is 0.8-1.2 mm, and the thickness of the dust suppression outer shell layer is 0.2-0.5 mm.

3. The multi-pore composite mineral cat litter according to claim 1, wherein, The hierarchical pore diatomite has three levels of mesopores, i.e., 1-2 nm micropores, 5-20 nm mesopores and 50-200 nm macropores.

4. The multi-pore composite mineral cat litter according to any one of claims 1-3, wherein, The mass ratio of the modified sodium bentonite to the hierarchical pore diatomite is 3:1-6:1, and the mass of the binder accounts for 5-7% of the total mass of the modified sodium bentonite, the hierarchical pore diatomite and the binder.

5. The multi-pore composite mineral cat litter according to any one of claims 1-3, wherein, The mass ratio of the MnO2-biochar composite material to the laccase microcapsules is 2.5-3.5, and the laccase microcapsules are co-immobilized by laccase aqueous solution, trehalose and a crosslinking agent.

6. A method of producing the multi-pore composite mineral cat litter according to any one of claims 1 to 5, characterized by, The method comprises the following steps: (1) mixing sodium bentonite with sodium citrate solution, ultrasonic treatment, centrifugation, calcination to obtain modified sodium bentonite; (2) crushing diatomite, sieving, separating clay minerals, adding HCl solution, stirring reaction to form 1-2 nm micropores, adding a surfactant, self-assembly in an ammonia environment to form 5-20 nm mesopores, adding ammonium bicarbonate, pre-burning after compression molding to form a honeycomb-like framework, heating and holding reaction to form 50-200 nm macropores to obtain the hierarchical pore diatomite; (3) oxidizing and cleaving biomass material to obtain biochar, impregnating into Mn(NO3)2 solution after activation, and obtaining MnO2-biochar composite material through hydrothermal reaction; (4) mixing laccase aqueous solution and trehalose, adding to a crosslinking agent, and freeze-drying to obtain the laccase microcapsules; (5) mixing the modified sodium bentonite in step (1) and the hierarchical pore diatomite in step (2), adding a binder, and granulating to obtain the water-absorbing inner core layer; (6) mixing the MnO2-biochar composite material in step (3) and the laccase microcapsules in step (4), uniformly coating and depositing on the water-absorbing inner core layer to form the catalytic deodorization intermediate layer; (7) heating and melting polyvinyl alcohol 2000, adding nano-SiO2, stirring to form a uniform slurry, spraying the slurry on the catalytic deodorization intermediate layer by electrostatic spraying process to form the dust suppression outer shell layer, drying and sieving to obtain the multi-level pore composite mineral cat litter.

7. The production method according to claim 6, wherein In step (2), the concentration of the HCl solution is 5-6 mol / L HCl, the solid-liquid ratio in the solution after adding the HCl solution is 0.2-0.3, and the stirring reaction is carried out at 70-80℃ for 2-2.5 h.

8. The preparation method according to claim 6, characterized in that, In step (2), the temperature is raised to 500-550 DEG C at a rate of 5-7 DEG C / min, and the holding time is 2-2.5 h.

9. The multi-pore composite mineral cat litter recycling method according to any one of claims 1 to 5, characterized by, The method comprises the following steps: (a) first, the litter is laid to a thickness of ≥5 cm, and after the clumps are cleaned up every day, new litter is added to the original thickness; (b) when the cumulative amount of use reaches 60% of the initial amount, all the litter is recovered; (c) the recovered litter is crushed and incinerated at 400-450 DEG C to regenerate the litter; (d) the regenerated litter is mixed with biochar, flue gas is introduced, calcination is performed, and ball milling is performed to obtain treated litter; (e) the treated litter is added to unused multi-level pore composite mineral litter for reuse; Or, the treated litter is used for garden slow-release fertilizer.

10. The recycling method according to claim 9, characterized in that, In step (d), the NH3 adsorption capacity of the treated litter is 85% or more of the NH3 removal rate of the unused litter.

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