Disclosure of Invention
The invention aims to overcome the defects in the prior art and provides a sludge ash modified titanium oxide-biochar composite photocatalyst which has the advantages of low cost, high pollutant adsorption efficiency and high degradation efficiency particularly on ammonia gas which is a main component of sludge drying odor.
In order to achieve the purpose, the invention adopts the following technical scheme:
the composite photocatalyst comprises titanium oxide, sludge ash and porous biochar, wherein the porous biochar is a carrier, and the titanium oxide and the sludge ash are loaded on the porous biochar;
the composite photocatalyst comprises 20-30 wt% of titanium oxide, 10-15 wt% of sludge ash and the balance porous biochar based on the total weight of the composite photocatalyst.
The invention also provides a preparation method of the sludge ash modified titanium oxide-biochar composite photocatalyst, which comprises the following steps:
(1) grinding the biomass powder, and sieving for later use;
calcining municipal sludge, and grinding to obtain sludge ash for later use;
(2) uniformly mixing biomass, sludge ash and titanium oxide, grinding, adding a dilute hydrochloric acid solution, adjusting the pH value to 1-2, stirring and mixing for 30min, adjusting the pH value to be neutral, and filtering to obtain a mixed solid;
(3) and (3) placing the mixed solid obtained in the step (2) into a vacuum furnace for calcination treatment, wherein the obtained solid product is the sludge ash modified titanium oxide-biochar composite photocatalyst.
In a further technical scheme, in the step (1), the biomass is ground and then is sieved by a 20-30-mesh sieve.
In a further technical scheme, in the step (1), the biomass is selected from one or more of straw, straw and wood chip.
In a further technical scheme, in the step (1), the municipal sludge is calcined for 5 hours at 800 ℃ in the air atmosphere, is taken out after being cooled to room temperature, and is ground to obtain sludge ash;
the mass fraction of phosphorus compounds and iron compounds in the sludge ash is more than or equal to 20 percent.
In a further technical scheme, in the step (2), the weight ratio of the biomass to the sludge ash to the titanium oxide is 1: (0.15-0.2): (0.2-0.3);
the concentration of the dilute hydrochloric acid solution is 1mol/L, and the addition amount of the dilute hydrochloric acid solution is 200 mL.
In a further technical scheme, in the step (3), the calcining treatment conditions at least satisfy the following conditions: the calcination temperature is 400-600 ℃, and the calcination time is 0.5-1.5 hours.
Compared with the prior art, the invention has the following technical effects:
1. the main gain components of the sludge ash modified titanium oxide-biochar composite photocatalyst provided by the invention are derived from incineration ash of byproduct sludge of a sewage treatment plant and lignocellulose biomass, the solid waste resource utilization is realized, the production cost of the composite photocatalyst is effectively reduced, and the composite photocatalyst has wide market application prospect;
2. the sludge ash modified titanium oxide-biochar composite photocatalyst provided by the invention can effectively utilize visible light, and the application range of the titanium oxide-based photocatalytic material is expanded;
3. the sludge ash modified titanium oxide-biochar composite photocatalyst provided by the invention has stronger acidity, and is beneficial to the degradation of ammonia gas which is the main component of biological drying malodorous gas;
4. the preparation method of the sludge ash modified titanium oxide-biochar composite photocatalyst provided by the invention has the advantages of simplicity in operation and low price and easiness in obtaining of all raw materials.
Additional features and advantages of the invention will be set forth in the detailed description which follows.
Detailed Description
In order to make the technical means, the creation features, the achievement purposes and the effects of the invention easy to understand, the invention is further clarified with the specific embodiments.
The invention provides a sludge ash modified titanium oxide-biological carbon composite photocatalyst, which comprises titanium oxide, sludge ash and porous biological carbon, wherein the porous biological carbon is a carrier, and the titanium oxide and the sludge ash are loaded on the porous biological carbon;
the composite photocatalyst comprises 20-30 wt% of titanium oxide, 10-15 wt% of sludge ash and the balance porous biochar based on the total weight of the composite photocatalyst.
According to the technical scheme provided by the invention, the titanium oxide-biochar composite photocatalytic material is modified and modified by sludge ash, Lewis acids such as aluminum, iron and phosphorus and Bronsted acid elements in the sludge ash are fully utilized to improve the adsorption capacity of the main component ammonia in sludge drying odor and the iron phosphate component after the sludge ash acid modification has visible light catalytic capacity, and the titanium oxide is subjected to in-situ treatment by reductive gases such as hydrogen generated in the biomass pyrolysis carbonization process, so that the defect of titanium oxide oxygen vacancy is improved, and the visible light utilization degree is improved; that is, the scheme provided by the invention makes full use of elements such as iron, aluminum, phosphorus and the like in the incineration ash and the reducing atmosphere generated by biomass pyrolysis to enhance the overall acidity and the visible light utilization degree of the composite photocatalyst, and improves the degradation efficiency of the main component ammonia gas of the biological drying malodorous gas.
The obtained composite photocatalytic material has high overall acidity, high visible light utilization degree, excellent ammonia adsorption performance on the main component of sludge drying odor, high efficiency of photocatalytic degradation of sludge drying odor, simple method operation and capability of realizing solid waste resource utilization.
The invention also provides a preparation method of the sludge ash modified titanium oxide-biochar composite photocatalyst, which comprises the following steps:
(1) grinding the biomass powder, and sieving for later use;
calcining municipal sludge, and grinding to obtain sludge ash for later use;
(2) uniformly mixing biomass, sludge ash and titanium oxide, grinding, adding a dilute hydrochloric acid solution, adjusting the pH value to 1-2, stirring and mixing for 30min, adjusting the pH value to be neutral, and filtering to obtain a mixed solid;
(3) and (3) placing the mixed solid obtained in the step (2) into a vacuum furnace for calcination treatment, wherein the obtained solid product is the sludge ash modified titanium oxide-biochar composite photocatalyst.
Further, according to the method provided by the invention, in the step (1), the biomass is ground and then is sieved by a 20-30-mesh sieve.
In the present invention, in the step (1), the biomass is preferably one or a combination of more than one selected from straw, rice straw and wood chip.
In the invention, the municipal sludge is calcined to remove organic matters in the municipal sludge, so that sludge ash is obtained, and active components in the municipal sludge are ensured to have a stable state when in use. As a specific implementation mode of municipal sludge calcination, in the step (1), the municipal sludge is calcined for 5 hours at 800 ℃ in the air atmosphere, taken out after being cooled to room temperature, and ground to obtain sludge ash; the mass fractions of phosphorus compounds and iron compounds in the sludge ash are respectively more than or equal to 20 percent. Specifically, in a specific embodiment of the present invention, the sludge ash comprises the following components by mass percent: 28.6 percent of silicon oxide, 20 percent of ferric oxide, 9.7 percent of aluminum oxide, 16.3 percent of calcium oxide, 22.5 percent of phosphorus pentoxide and 3 percent of magnesium oxide, and the balance of trace compounds such as sodium, potassium, sulfur and the like.
According to the method provided by the invention, in order to ensure that odor with different concentrations generated in different time periods of sludge drying can be effectively adsorbed and degraded, and ensure that the main active component and the auxiliary active component in the composite photocatalytic material can exist and be regulated in a proper proportion after sludge ash and titanium oxide from different sources are added; the weight ratio of the biomass to the sludge ash to the titanium oxide is 1: (0.15-0.2): (0.2-0.3); the concentration of the dilute hydrochloric acid solution is 1mol/L, and the addition amount of the dilute hydrochloric acid solution is 200 mL.
According to the method provided by the invention, in the step (3), the calcining treatment conditions at least satisfy the following conditions: the calcination temperature is 400-600 ℃, and the calcination time is 0.5-1.5 hours.
The invention also provides an application of the sludge ash modified titanium oxide-biochar composite photocatalyst in sludge drying odor treatment.
The sludge ash modified titanium oxide-biochar composite photocatalyst provided by the invention is further illustrated by specific examples.
Example 1
The embodiment provides a preparation method of a sludge ash modified titanium oxide-biochar composite photocatalyst, which comprises the following steps:
(1) grinding the straws, and sieving the ground straws with a 20-mesh sieve for later use;
calcining municipal sludge in an air atmosphere at 800 ℃ for 5 hours, taking out after cooling to room temperature, and grinding to obtain sludge ash; through detection, the sludge ash comprises the following components in percentage by mass: 28.6 percent of silicon oxide, 20 percent of ferric oxide, 9.7 percent of aluminum oxide, 16.3 percent of calcium oxide, 22.5 percent of phosphorus pentoxide and 3 percent of magnesium oxide, and the balance of trace compounds such as sodium, potassium, sulfur and the like;
(2) uniformly mixing 10g of straw powder, 2g of sludge ash and 3g of titanium oxide (DeguoSa P25), grinding, adding 200mL of 1M dilute hydrochloric acid solution, adjusting the pH value to 1, stirring and mixing for 30min, adjusting the pH value to be neutral, and filtering to obtain a mixed solid;
(3) and (3) placing the mixed solid obtained in the step (2) in a vacuum furnace, calcining at 550 ℃ for 1 hour, and cooling to normal temperature to obtain a solid product, namely the sludge ash modified titanium oxide-biochar composite photocatalyst.
And (3) performance testing: the obtained composite photocatalyst is flatly laid in a photocatalytic reaction bin, and ammonia gas standard gas is introduced to serve as sludge drying odor model gas to enable the initial ammonia gas concentration in the reaction bin to be 300 ppm; and respectively irradiating the reaction bin by using a visible light source and an ultraviolet light source, and detecting every 10 min. The result shows that the ammonia removal rate reaches 91.50% after 1h under the ultraviolet irradiation; the ammonia removal rate can reach 64.10% after 3h under the irradiation of visible light.
Example 2
This example is substantially the same as the preparation method of the composite photocatalyst in example 1, except that the biomass is replaced by wood chips; and (5) keeping the other conditions unchanged, and preparing the composite photocatalyst.
The performance test is carried out according to the method in the embodiment 1, and the result shows that the ammonia removal rate reaches 90.80% after 1 hour under the ultraviolet irradiation; the ammonia removal rate can reach 65.20% after 3h under the irradiation of visible light.
Comparative example 1
The preparation method of the composite photocatalyst in the comparative example is basically the same as that of the composite photocatalyst in the example 1, except that in the step (2), 10g of straw powder, 0g of sludge ash and 3g of titanium oxide (de gu sai P25) are uniformly mixed and ground; and (5) keeping the other conditions unchanged, and preparing the composite photocatalyst.
The performance test is carried out according to the method in the embodiment 1, and the result shows that the ammonia removal rate reaches 77.10% after 1h under the ultraviolet irradiation; the ammonia removal rate can reach 37.20% after 3 hours under the irradiation of visible light.
Comparative example 2
The preparation method of the composite photocatalyst in the comparative example is basically the same as that of the composite photocatalyst in the example 1, except that in the step (2), 10g of straw powder, 2g of sludge ash and 0g of titanium oxide (de gu sai P25) are uniformly mixed and ground; and (5) keeping the other conditions unchanged, and preparing the composite photocatalyst.
The performance test is carried out according to the method in the embodiment 1, and the result shows that the ammonia removal rate reaches 51.60 percent after 1 hour under the ultraviolet irradiation; the ammonia removal rate can reach 26.90 percent after 3 hours under the irradiation of visible light.
Comparative example 3
The preparation method of the composite photocatalyst in the comparative example is basically the same as that of the composite photocatalyst in the example 1, except that the adopted sludge ash comprises the following components in percentage by mass: 31.5% of silicon oxide, 10.7% of ferric oxide, 8.7% of aluminum oxide, 41% of calcium oxide, 4% of phosphorus pentoxide and 4% of magnesium oxide, and the balance of trace compounds such as sodium, potassium, sulfur and the like; and (5) keeping the other conditions unchanged, and preparing the composite photocatalyst.
The performance test is carried out according to the method in the embodiment 1, and the result shows that the ammonia removal rate reaches 78.70% after 1 hour under the ultraviolet irradiation; the ammonia removal rate can reach 48.60% after 3h under the irradiation of visible light.
The technical scheme provided by the invention has the advantages that the titanium oxide is modified and modified by the sludge ash, so that the oxygen vacancy defect of the titanium oxide is improved, the visible light utilization degree is improved, and the excellent ammonia gas removal effect can be realized under the irradiation of the visible light.
The foregoing shows and describes the general principles, essential features, and inventive features of this invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.