High-porosity anti-mineralization sulfur autotrophic denitrification filter material capable of slowly releasing trace elements and preparation method of high-porosity anti-mineralization sulfur autotrophic denitrification filter material

Abstract

The invention relates to the technical field of sewage treatment, and particularly discloses a high-porosity slow-release microelement anti-mineralization sulfur autotrophic denitrification filter material and a preparation method thereof. The sulfur autotrophic denitrification filter material is of a core-shell structure, a complex of sulfur, volcanic rock micro powder and a curing fungicide is used as an inner core, and a hydrophobic polymer coating layer and a porous ceramic bonding layer are sequentially coated on the surface of the inner core; the hydrophobic polymer coating layer is a hydrophobic breathable composite film formed by crosslinking a polydimethylsiloxane prepolymer and calcium alginate. The volcanic rock natural trace elements are utilized to realize waste control by waste, surface mineralization is effectively prevented through the hydrophobic middle layer, the activity of the microbial inoculum is protected in combination with a low-temperature flexible sintering process, and the whole device has the advantages of high porosity, light weight, quick start, long service life, low backwashing energy consumption and the like. Compared with the prior art, the invention has remarkable innovativeness and creativity in the aspects of structural design, material selection and process integration.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of advanced wastewater treatment, in particular to a high-porosity slow-release trace element anti-mineralization sulfur autotrophic denitrification filter material and a preparation method thereof, in particular to a sulfur autotrophic denitrification filter material with high porosity, slow-release trace elements, anti-surface mineralization and pre-solidification functional bacteria agent and a preparation method thereof. BACKGROUND

[0002] Sulfur autotrophic denitrification technology is widely used in the field of low carbon-nitrogen ratio wastewater denitrification due to its advantages of no need for external organic carbon source, low sludge production and low operation cost. However, the existing sulfur autotrophic filter material still has the following problems: (1) Porosity and biofilm retention contradiction: CN116143281B improves the strength by tabletting, but the porosity is low, and backwashing easily leads to biofilm shedding. (2) Lack of trace elements: the lack of trace elements in oligotrophic wastewater limits microbial activity, and CN119038744B needs to add trace elements, which is high in cost. (3) Surface mineralization: SO4 2- and Ca 2+ form CaSO4 precipitate, blocking the pores (CN116715357B does not solve the problem). (4) Filter material weight and energy consumption: the traditional filter material has large density and high backwashing energy consumption. Bacteria agent immobilization effect is poor: CN118724272B simply adsorbs bacteria agent, which is easy to lose. SUMMARY

[0003] To solve the above technical problems, the present application provides a high-porosity slow-release trace element anti-mineralization sulfur autotrophic denitrification filter material and a preparation method thereof. The filter material obtained by the present application takes acid-washed-activated porous volcanic rock as the core skeleton, and is designed in a "core-shell-coat" three-layer structure: the inner core is a composite of sulfur, volcanic rock powder and microencapsulated sulfur autotrophic bacteria agent; the intermediate layer is a hydrophobic and breathable PDMS-calcium alginate composite membrane, which is used to physically isolate CaSO4 precipitate; and the outer shell is a lightweight porous ceramic layer formed by bonding of silica sol and metakaolin. The present application realizes "waste treatment with waste" by using the natural trace elements of volcanic rock, effectively prevents surface mineralization by the hydrophobic intermediate layer, protects the activity of bacteria agent by a low-temperature flexible sintering process, and has the advantages of high porosity (≥45%), light weight (bulk density <1.0 g / cm 3 , fast start (shortened by 40%), long service life and low backwashing energy consumption. Compared with the prior art, the present application has significant innovation and creativity in terms of structure design, material selection and process integration.

[0004] The first object of the present application is to provide a high-porosity slow-release trace element anti-mineralization sulfur autotrophic denitrification filter material, which is a core-shell structure, and the composite of sulfur, volcanic rock micro-powder and bacterial agent is the inner core, and a hydrophobic polymer coating layer and a porous ceramic bonding layer are sequentially coated on the surface of the inner core; the hydrophobic polymer coating layer is formed by cross-linking polydimethylsiloxane prepolymer and calcium alginate to form a hydrophobic and breathable composite film.

[0005] In some embodiments of the present application, the thickness of the hydrophobic polymer coating layer is 10-50 μm.

[0006] In some embodiments of the present application, the bacterial agent includes Thiobacillus (NCBI classification number 919) and / or Sulfurimonas (NCBI classification number 202746), and the viable bacterial count of the bacterial agent is ≥1×10 8 CFU / g.

[0007] The second object of the present application is to provide a preparation method of the sulfur autotrophic denitrification filter material, which comprises the following steps: S1. Acid soaking and washing to neutral of porous volcanic rock aggregate, high-temperature calcination, and then crushing and sieving to obtain modified porous volcanic rock fine powder; S2. Mixing of elemental sulfur, the modified porous volcanic rock fine powder obtained in step S1, pore-forming agent and bacterial agent, and granulating the core to obtain a composite; S3. Immersing the composite core obtained in step S2 in a hydrophobic modifier solution, and after taking out, placing it in a cross-linking agent solution for reaction to obtain a composite with a surface wrapped with a hydrophobic polymer coating layer; S4. Mixing the composite with a surface wrapped with a hydrophobic polymer coating layer with a binder, granulating and forming, and heating and curing to obtain the sulfur autotrophic denitrification filter material.

[0008] In some embodiments of the present application, the sintering temperature of step S4 is controlled at 130-150℃, and the holding time is 1-2 hours, so as to avoid damaging the physicochemical properties of the bacterial agent and sulfur.

[0009] In step S1 of the present application, the acid includes one or more of hydrochloric acid, sulfuric acid and nitric acid; the concentration of the acid is 5-10 wt%; The soaking time is 2-3 h; The calcination temperature is 800-900℃, and the time is 1-2 hours; The modified porous volcanic rock fine powder has a mesh size <200 mesh; The particle size of the modified porous volcanic rock fine powder is 0.3-0.5 mm, the bulk density is <0.9 g / cm 3 , and the porosity is ≥50%.

[0010] In some embodiments of the present application, in step S2, the hydrophobic modifier is selected from one or more of polydimethylsiloxane prepolymer, hexadecyl trimethoxysilane and octadecyl triethoxysilane, and the concentration of the hydrophobic modifier is 5-15wt%; The pore-forming agent comprises sodium carboxymethyl cellulose and / or starch. The diameter of the composite is 2-3mm.

[0011] In some embodiments of the present application, in step S3, the crosslinking agent comprises a sodium alginate solution. The concentration of the sodium alginate solution is 2-5wt%. The time of the crosslinking reaction is 5-10min.

[0012] In some embodiments of the present application, in step S4, the binder is a mixture of silica sol and metakaolin, and the mass ratio of silica sol to metakaolin is (2-4):1. The temperature of the heat curing is 120-150℃, and the time is 1-2 hours.

[0013] In some embodiments of the present application, the modified porous volcanic rock fine powder is 40-60 parts, the elemental sulfur is 20-35 parts, the binder is 5-15 parts, the pore-forming agent is 3-8 parts, the hydrophobic modifier is 1-5 parts, and the sulfur autotrophic denitrification bacteria agent curing liquid is 5-10 parts.

[0014] The above technical solution of the present application has the following advantages compared with the prior art: The sulfur autotrophic denitrification filter material has a core-shell structure, which mainly comprises an inner core: sulfur + volcanic rock fine powder + bacteria agent, which provides sulfur source, trace elements and biological activity; an intermediate layer: PDMS-calcium alginate hydrophobic film, which blocks Ca 2+ and SO4 2- contact and prevents mineralization; and an outer shell: silica sol-metakaolin light bonding layer, which ensures strength and reduces density. The present application takes modified volcanic rock as the core, utilizes its natural trace elements and pore structure, and realizes “waste treatment with waste”. The present application actively prevents mineralization by introducing a hydrophobic intermediate layer, and the process innovation: low-temperature flexible sintering + bacteria agent immobilization, protects the activity of the bacteria agent and accelerates the start-up. DETAILED DESCRIPTION

[0015] The present application will be further described below in conjunction with specific examples, so that those skilled in the art can better understand the present application and implement it, but the examples are not limiting to the present application.

[0016] Example 1 This example provides specific steps for preparing a sulfur autotrophic denitrification filter material, as shown below: S1: Take the porous volcanic rock aggregate with particle size of 3-5 mm (purchased in the market), soak it in 5wt% dilute hydrochloric acid for 2 hours, wash it to neutral, and bake it at 850℃ for 1.5 hours to obtain modified volcanic rock aggregate (the bulk density is 0.85 g / cm 3 , the porosity is 55%), crush and sieve it to obtain modified volcanic rock fine powder with mesh number of 200.

[0017] S2: Mix 25 parts of sulfur powder, 15 parts of modified volcanic rock fine powder (sieved to 200 mesh) obtained in step S1, 5 parts of sodium carboxymethyl cellulose, 8 parts of bacterial liquid (including Thiobacillus NCBI classification number 919 with a viable bacterial count of 1×10 9 CFU / g, and water) to form a core with a diameter of 2-3 mm, and dry it at 40℃.

[0018] S3: Soak the core obtained by drying in step S2 in a 10wt% PDMS prepolymer (Dow Corning 184) heptane solution, then soak it in a 2wt% sodium alginate solution for 5 minutes to form a PDMS-CaAlg hydrophobic film on the surface of the core, and dry it at 60℃ for 1h to obtain modified volcanic rock aggregate.

[0019] S4: Mix 50 parts of modified volcanic rock aggregate obtained in step S3, 10 parts of silica sol, and 5 parts of metakaolin under room temperature for 2h to coat the outer surface of the core modified volcanic rock aggregate, granulate it to a particle size of 4-5mm, and solidify it at 130℃ for 2 hours to obtain the sulfur autotrophic denitrification filter material. The performance of the obtained filter material is as follows: the bulk density is 0.95 g / cm 3 , the compressive strength is >40N / pebble, and the porosity is 45%. In simulated wastewater (NO3 - -N=30 mg / L, HRT=2 h), the denitrification load reaches 0.8 kg N / (m 3 ·d), the start-up time is shortened by 40%, and mineralization is not observed for 60 days.

[0020] Example 2 This example provides specific steps for preparing a sulfur autotrophic denitrification filter material, as follows: S1: Take the porous volcanic rock aggregate with particle size of 3-5 mm (purchased in the market), soak it in 5wt% dilute hydrochloric acid for 2 hours, wash it to neutral, and bake it at 900℃ for 1 hour to obtain modified volcanic rock aggregate (the bulk density is 0.85 g / cm 3 , the porosity is 60%), crush and sieve it to obtain modified volcanic rock fine powder with mesh number of 50.

[0021] S2: 30 parts of sulfur powder, 10 parts of modified volcanic rock powder (50 mesh) obtained in step S1, 5 parts of sodium carboxymethyl cellulose, 10 parts of bacterial agent (Sulfurimonas (NCBI classification number 202746), live bacteria number 1 x 10 9 CFU / g) were mixed, and water was added to form a core with a diameter of 2-3 mm, which was dried at 40°C.

[0022] S3: The core obtained by drying in step S2 was immersed in a 10wt% PDMS prepolymer (Dow Corning 184) heptane solution, then drained and immersed in a 3wt% sodium alginate solution for 8 minutes to form a PDMS-CaAlg hydrophobic film on the surface of the core, which was dried at 60°C for 1 hour to obtain modified volcanic rock aggregate.

[0023] S4: 50 parts of modified volcanic rock aggregate obtained in step S3, 15 parts of silica sol, and 5 parts of metakaolin were mixed under stirring at room temperature for 2 hours to coat the outer surface of the core modified volcanic rock aggregate, which was granulated to a particle size of 4-5 mm and cured at 140°C for 1.5 hours to obtain the sulfur autotrophic denitrification filter material. The performance of the obtained filter material was detected: the bulk density was 0.92 g / cm 3 , the porosity was 48%, the denitrification load was increased to 0.85 kg N / (m 3 ·d), and the start-up time was shortened by 50%.

[0024] Comparative Example 1 The preparation method of this comparative example was similar to that of Example 1, except that step S2 was omitted. The performance of the obtained filter material was detected: the bulk density was 1.1 g / cm 3 , the compressive strength was >40 N / pebble, and the porosity was 30%. In the simulated wastewater (NO3 - -N = 30 mg / L, HRT = 2 h), there was no denitrification and no mineralization.

[0025] Comparative Example 2 The preparation method of this comparative example was similar to that of Example 1, except that step S3 was omitted. The performance of the obtained filter material was detected: the bulk density was 0.98 g / cm 3 , the compressive strength was >40 N / pebble, and the porosity was 38%. In the simulated wastewater (NO3 - -N = 30 mg / L, HRT = 2 h), the denitrification load reached 0.4 kg N / (m 3 ·d), the start-up time was shortened by 10%, surface mineralization occurred at 25 days, and the pore clogging rate reached 25%.

[0026] Comparative Example 3 The preparation method of this comparative example and example 1 is similar, the difference is that step S4 is missing. The properties of the obtained filter material are: bulk density 0.8 g / cm 3 , compressive strength <20 N / acre, porosity 52%. In simulated wastewater (NO3 - -N=30 mg / L, HRT=2 h), the initial nitrogen removal load is 0.5 kg N / (m 3 ·d), the start-up time is shortened by 15%, but after backwashing once (regular backwashing intensity), the filter material breakage rate is 30%, local mineralization occurs in 30 days, and the nitrogen removal load is reduced to 0.2 kg N / (m 3 ·d).

[0027] Obviously, the above examples are merely examples for the sake of clarity, and are not limiting of the embodiments. Other different forms of changes or variations can be made by those of ordinary skill in the art on the basis of the above description. It is not necessary or possible to exhaust all embodiments. The obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A high porosity slow release trace element resistant to mineralization sulfur autotrophic denitrification filter media, characterized in that, The sulfur autotrophic denitrification filter material has a core-shell structure, and a composite of elemental sulfur, volcanic rock micro powder and bacterial agent is used as the core, and a hydrophobic polymer coating layer and a porous ceramic bonding layer are sequentially coated on the surface of the core; the hydrophobic polymer coating layer is formed by cross-linking of a polydimethylsiloxane prepolymer and calcium alginate to form a hydrophobic and breathable composite film.

2. The sulfur autotrophic denitrifying media of claim 1, wherein, The thickness of the hydrophobic polymer coating layer is 10-50 microns.

3. The sulfur autotrophic denitrification media of claim 1, wherein, The bacterial agent comprises Thiobacillus and / or Sulfurimonas, and the viable bacterial count in the bacterial agent is ≥1×10 8 CFU / g.

4. The method of claim 1-3, wherein the method is characterized by, The method comprises the following steps: S1. Acid soaking and washing to neutralize the porous volcanic rock aggregate, high-temperature calcination, and then crushing and sieving to obtain modified porous volcanic rock powder; S2. Mixing elemental sulfur, the modified porous volcanic rock powder obtained in step S1, a pore-forming agent and a bacterial agent, and granulating the mixture into a core to obtain a composite; S3. Immersing the composite core obtained in step S2 in a hydrophobic modifier solution, and then placing it in a cross-linking agent solution for reaction to obtain a composite with a hydrophobic polymer coating layer wrapped on the surface; S4. Mixing the composite with a hydrophobic polymer coating layer wrapped on the surface with a bonding agent, granulating and forming, and heating and curing to obtain the sulfur autotrophic denitrification filter material.

5. The production method according to claim 4, characterized by, The sintering temperature in step S4 is controlled at 130-150 DEG C, and the holding time is 1-2 hours to avoid damaging the physicochemical properties of the bacterial agent and sulfur.

6. The preparation method according to claim 4, characterized in that, In step S1, the acid includes one or more of hydrochloric acid, sulfuric acid and nitric acid; the concentration of the acid is 5-10 wt%; The soaking time is 2-3 hours; The calcination temperature is 800-900 DEG C, and the time is 1-2 hours; The modified porous volcanic rock powder has a mesh size of <200 mesh; The modified porous volcanic rock fine powder has a particle size of 0.3-0.5 mm, a bulk density <0.9 g / cm 3 , and a porosity ≥50%.

7. The preparation method according to claim 4, characterized in that, In step S2, the hydrophobic modifier is selected from a polydimethylsiloxane prepolymer, and the concentration of the hydrophobic modifier is 5-15 wt%; The pore-forming agent includes sodium carboxymethyl cellulose and / or starch; The diameter of the composite is 2-3 mm.

8. The preparation method according to claim 4, characterized in that, In step S3, the cross-linking agent includes a sodium alginate solution; The concentration of the sodium alginate solution is 2-5 wt%; The cross-linking reaction time is 5-10 minutes.

9. The preparation method according to claim 4, characterized in that, In step S4, the bonding agent is a mixture of silica sol and metakaolin, and the mass ratio of silica sol to metakaolin is (2-4):1; The heating and curing temperature is 120-150 DEG C, and the time is 1-2 hours.

10. The method of claim 4, wherein, Modified porous volcanic rock powder 40-60 parts, elemental sulfur 20-35 parts, bonding agent 5-15 parts, pore-forming agent 3-8 parts, hydrophobic modifier 1-5 parts, and sulfur autotrophic denitrification bacterial agent curing liquid 5-10 parts.