CN113213579B - Application of photocatalytic biochar composite material in catalytic degradation of printing and dyeing wastewater - Google Patents
Application of photocatalytic biochar composite material in catalytic degradation of printing and dyeing wastewater Download PDFInfo
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Images
Classifications
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/30—Treatment of water, waste water, or sewage by irradiation
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
- B01J27/02—Sulfur, selenium or tellurium; Compounds thereof
- B01J27/04—Sulfides
-
- B01J35/39—
-
- B01J35/615—
-
- B01J35/633—
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/28—Treatment of water, waste water, or sewage by sorption
- C02F1/283—Treatment of water, waste water, or sewage by sorption using coal, charred products, or inorganic mixtures containing them
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/30—Organic compounds
- C02F2101/308—Dyes; Colorants; Fluorescent agents
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/30—Organic compounds
- C02F2101/36—Organic compounds containing halogen
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/30—Organic compounds
- C02F2101/38—Organic compounds containing nitrogen
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/30—Organic compounds
- C02F2101/40—Organic compounds containing sulfur
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
- C02F2103/30—Nature of the water, waste water, sewage or sludge to be treated from the textile industry
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2305/00—Use of specific compounds during water treatment
- C02F2305/10—Photocatalysts
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W10/00—Technologies for wastewater treatment
- Y02W10/30—Wastewater or sewage treatment systems using renewable energies
- Y02W10/37—Wastewater or sewage treatment systems using renewable energies using solar energy
Abstract
The invention provides an application of a photocatalytic biochar composite material in catalytic degradation of printing and dyeing wastewater. The invention provides an application of a photocatalytic biochar composite material in catalytic degradation of printing and dyeing wastewater, wherein the photocatalytic biochar composite material comprises biochar and a ZnO/ZnS mixture, the loading rate of the ZnO/ZnS mixture is 14-20%, and the ZnO/ZnS mixture is loaded in micropores and/or on the surface of the biochar.
Description
Technical Field
The invention relates to the field of environmental functional materials, in particular to a photocatalytic biochar composite material and a preparation method and application thereof.
Background
The textile dyeing and finishing is the traditional prop industry and the important civil industry in China, but the discharge amount of the printing and dyeing wastewater is large, the total water consumption of a factory is 60-80%, the annual discharge amount exceeds 15 hundred million tons, and the textile dyeing and finishing has the characteristics of high chromaticity, high toxicity, high organic matter content, high salinity, complex components, large water quality change and the like, and is the industrial wastewater which is accepted at home and abroad and difficult to treat, and three times or deep treatment is needed. After advanced treatment, the printing and dyeing wastewater can be secondarily used for production, so that pollution is reduced, water is saved, the cost of enterprises is reduced, and the method has important practical significance for realizing the green manufacturing technology of textile industry.
Common advanced treatment methods include advanced oxidation, membrane biological, physical adsorption, photocatalytic oxidation, and the like. The advanced oxidation method (such as application publication number CN202499737U, CN 102180558A) has extremely short free radical existence time and no selectivity, has high water distribution requirement, has complex process and can possibly introduce secondary pollutants. The membrane biological method (such as the application publication number of CN111285448A, CN 210656547U) has high dye removal rate and simple process, but the membrane has high cost and high process energy consumption, and the industrialized popularization is limited. The physical adsorption method has simple process, and commonly used adsorbents are activated carbon, biomass carbon and the like (such as application publication number CN111003744A, CN 103803754A), but the preparation and regeneration of the activated carbon need high temperature (more than or equal to 850 ℃), so that the cost of the adsorbent is increased; the biomass charcoal is formed by pyrolyzing biomass such as agricultural and forestry waste at a low temperature (< 700 ℃) under a complete or partial anoxic state, has the advantages of abundant raw materials, simple manufacture and low cost, but has limited adsorption effect and is not easy to regenerate. The photocatalytic oxidation method (such as the application publication number of CN110723777A, CN110683608A, CN 105384308A) has the advantages that the photocatalytic material is generally high in price, easy to run off in use and difficult to recover, and an ultraviolet light source is additionally required to excite the catalytic reaction, so that the complexity and the cost of the process are increased. The advanced treatment technology of printing and dyeing wastewater with simple and efficient process and low cost becomes a focus of increasing attention and a technical problem to be solved.
Disclosure of Invention
Aiming at the problems existing in the prior art, the development of a printing and dyeing wastewater advanced treatment method which has the advantages of simple process, high efficiency, low cost and easy large-scale popularization and application is urgent.
The inventor finds that the waste straw powder is used in ZnSO for solving the technical problems 4 The modified biochar is prepared by low-temperature pyrolysis after being fully soaked in the solution, and methylene blue organic macromolecules in the wastewater can be rapidly removed under the natural light condition. The surface of the modified biochar composite material is firmly combined with a large number of photocatalytic active points, organic dye molecules in wastewater are rapidly adsorbed, the adsorbed dye molecules are oxidized and degraded under the induction of natural light, and the used modified biochar can be recycled after simple regeneration treatment, so that the effect is stable. The photocatalytic biochar composite material has the advantages of simple production process, short production period and low cost, breaks through the self adsorption upper limit of the biochar by utilizing the natural photocatalytic degradation effect, does not need to be supported by an ultraviolet light source, greatly simplifies the wastewater treatment process and cost, can be recycled, and really realizes the advanced treatment of the printing and dyeing wastewater with low cost.
The invention provides an application of a photocatalytic biochar composite material in catalytic degradation of printing and dyeing wastewater, wherein the photocatalytic biochar composite material comprises biochar and a ZnO/ZnS mixture, the loading rate of the ZnO/ZnS mixture is 14-20%, and the ZnO/ZnS mixture is loaded in micropores and/or on the surface of the biochar.
The loading of the ZnO/ZnS mixture in the invention is controlled by (W UBC -W BC )/W UBC Calculated as x100%, where W UBC And W is BC Respectively the quality of the photocatalytic biochar composite material and the quality of the straw biochar at different pyrolysis temperatures.
Preferably, the mass percentage of Zn element in the surface element of the photocatalytic biochar composite material is 25% -40%.
The mass percentage of Zn element in the surface element of the photocatalytic biochar composite material is detected by an energy spectrometer.
Preferably, the specific surface area of the photocatalytic biochar composite material is 300-500m 2 ·g -1 Preferably 330-480m 2 ·g -1 ；
Alternatively, preferably, the pore volume of the photocatalytic biochar composite material is 0.220-0.330 cm 3 Preferably 0.240-0.330 cm/g 3 /g。
Preferably, 4g/L of the photocatalytic biochar composite material is added into 10-100mg/L of methylene blue solution for 1-30 hours, and the chromaticity of the solution is 0.0-22.9;
or it is used in COD cr After the photocatalytic biochar composite material with the value of 75-170mg/L and 4g/L is added for 1-30 hours, the solution COD is obtained cr The value is 0-11mg/L;
or the degradation rate of the photocatalytic charcoal composite material is 97-100% after adding 4g/L of the photocatalytic charcoal composite material into 10-100mg/L of methylene blue solution for 1-30 hours.
Preferably, the preparation method of the photocatalytic biochar composite material comprises the following steps:
(1) Dipping straw powder into zinc source water solution, and then drying to prepare a composite material precursor;
(2) And (3) placing the composite material precursor obtained in the step (1) in an inert gas atmosphere, preserving heat at 100-150 ℃, and then heating for pyrolysis to obtain the photocatalytic biochar composite material.
Preferably, the straw in the step (1) is any one of tobacco stalk, corn stalk, coix seed stalk, sorghum stalk and mixture thereof.
Preferably, the zinc source aqueous solution in step (1) is ZnSO 4 The aqueous solution of the water-soluble polymer,
preferably, the ZnSO 4 The mass concentration of the aqueous solution is 1-5%, preferably, the ZnSO 4 The mass concentration of the aqueous solution is 3-5%, and the ZnSO is more preferable 4 The mass concentration of the solution is 3%;
preferably, the ZnSO 4 The mass ratio of the aqueous solution to the straw powder is (2-4) 1, preferably the ZnSO 4 The mass ratio of the aqueous solution to the straw powder is (2-3):1。
preferably, the ZnSO of step (1) 4 The temperature of the aqueous solution is 60-100 ℃, preferably 80 ℃;
preferably, the straw powder is prepared in ZnSO 4 The dipping time in the solution is 5-12 h, and more preferably, the straw powder is in ZnSO 4 The soaking time in the solution is 8-10 h;
alternatively, preferably, the stirring rate is from 100 to 400r/min,
alternatively, preferably, the stirring time is 3 to 5 hours, preferably 5 hours;
alternatively, preferably, the drying temperature is 60-100 ℃, preferably 70-90 ℃,
alternatively, the drying time is preferably 10 to 24 hours, and preferably 10 to 13 hours.
Preferably, the temperature of the inert gas atmosphere in the step (2) is 100-120 ℃, preferably, the temperature keeping time is 1-5 h, preferably, the temperature keeping time is 1.5-3 h;
alternatively, preferably, the pyrolysis temperature in the step (2) is 400-700 ℃, and preferably, the pyrolysis temperature is 600 ℃;
or, preferably, the heating rate is 8-10 ℃/min;
or, preferably, the pyrolysis time is 1-4 h, and the pyrolysis time is 2-2.5 h;
alternatively, preferably, the inert gas is N 2 Or Ar;
alternatively, preferably, the flow rate of the inert gas is 40-100 ml/min;
alternatively, preferably, the pyrolysis reaction is carried out in a tube furnace.
Preferably, the CODcr value of the organic dye of the printing and dyeing wastewater is lower than 200mg/L,
preferably, the pH value of the printing and dyeing wastewater is 6-9.
Preferably, the catalytic degradation reaction is performed under natural light.
The invention also provides a printing and dyeing wastewater treatment method, which comprises the following steps:
adding the photocatalytic biochar composite material in the application into printing and dyeing wastewater to be treated, and oscillating under natural light to perform catalytic degradation reaction;
the photocatalytic biochar composite material comprises biochar and a ZnO/ZnS mixture, wherein the loading rate of the ZnO/ZnS mixture is 15-20%, and the ZnO/ZnS mixture is loaded in micropores and/or on the surface of the biochar.
Preferably, the mass percentage of Zn element in the surface element of the photocatalytic biochar composite material is 25% -40%.
Preferably, the specific surface area of the photocatalytic biochar composite material is 300-550m 2 ·g -1 Preferably 340-380m 2 ·g -1 ；
Alternatively, preferably, the pore volume of the photocatalytic biochar composite material is 0.220-0.330 cm 3 Preferably 0.250-0.270 cm/g 3 /g。
Preferably, the preparation method of the photocatalytic biochar composite material comprises the following steps:
(1) Dipping straw powder into zinc source water solution, and then drying to prepare a composite material precursor;
(2) And (3) placing the composite material precursor obtained in the step (1) in an inert gas atmosphere, preserving heat at 100-150 ℃, and then heating for pyrolysis to obtain the photocatalytic biochar composite material.
Preferably, the straw in the step (1) is any one of tobacco stalk, corn stalk, coix seed stalk, sorghum stalk and mixture thereof.
Preferably, the zinc source aqueous solution in step (1) is ZnSO 4 The aqueous solution of the water-soluble polymer,
preferably, the ZnSO 4 The mass concentration of the aqueous solution is 1-5%, preferably, the ZnSO 4 The mass concentration of the aqueous solution is 3-5%, and the ZnSO is more preferable 4 The mass concentration of the solution is 3%;
preferably, the ZnSO 4 The mass ratio of the aqueous solution to the straw powder is (2-4) 1, preferably the ZnSO 4 The mass ratio of the aqueous solution to the straw powder is (2-3): 1.
Preferably, the ZnSO of step (1) 4 The temperature of the aqueous solution is 60-100 ℃, preferably 80 ℃;
the straw powder is prepared in ZnSO 4 The dipping time in the solution is 5-12 h, and more preferably, the straw powder is in ZnSO 4 The soaking time in the solution is 8-10 h;
alternatively, preferably, the stirring rate is from 100 to 400r/min,
alternatively, preferably, the stirring time is 3 to 5 hours, preferably 5 hours;
alternatively, preferably, the drying temperature is 60-100 ℃, the drying temperature is 70-90 ℃,
alternatively, it is preferable that the drying time is 10 to 24 hours and the drying time is 10 to 13 hours.
Preferably, the temperature of the inert gas atmosphere in the step (2) is 100-120 ℃, preferably, the temperature keeping time is 1-5 h, preferably, the temperature keeping time is 1.5-3 h;
alternatively, preferably, the pyrolysis temperature in the step (2) is 400-700 ℃, and preferably, the pyrolysis temperature is 600 ℃;
or, preferably, the heating rate is 8-10 ℃/min;
or, preferably, the pyrolysis time is 1-4 h, and the pyrolysis time is 2-2.5 h;
alternatively, preferably, the inert gas is N 2 Or Ar;
alternatively, preferably, the flow rate of the inert gas is 40-100 ml/min;
alternatively, preferably, the carbonization reaction is performed in a tube furnace.
Preferably, the oscillation is carried out at a temperature of 28-32 ℃;
preferably, the oscillation frequency is 250-300 times/min;
preferably, the oscillation time is 1-30h.
The beneficial effects of the invention include:
1. the photocatalytic biochar composite material is prepared by low-temperature pyrolysis of waste straws by an infiltration method, the production cost is greatly reduced compared with that of a common photocatalyst, the preparation process is simple, the preparation condition is mild, no secondary pollution is caused, the environment is friendly, the photocatalytic adsorption performance is rapid and efficient, the CODcr value is lower than 100mg/L of raw water after the low-temperature pyrolysis of 600 ℃, the removal rate is higher than 94% in 0.5h, and the removal rate is 100% in 1 h.
2. The regeneration process of the photocatalytic biochar composite material provided by the invention is simple to operate, low in cost, strong in settleability and small in mass loss, solves the problems of easy loss and difficult recovery of a common nano photocatalyst in use, and has the removal capacity of more than 95% of that of the first use after five times of cyclic utilization, so that the post-treatment cost of an adsorbent by enterprises is reduced, and the environmental pressure is reduced.
3. The method for deeply treating the organic dye wastewater by natural photocatalytic adsorption does not need to be held by an ultraviolet light source, has simple treatment process and good treatment effect, can obtain 100% decolored wastewater after being treated for 1h under the conditions that the concentration of the organic dye is lower than 30mg/L, the pH value of the wastewater is 7-7.5 and the CODcr value is lower than 100mg/L, is higher than the recycling standard, and meets the technical requirements of deeply treating the printing and dyeing wastewater with low cost.
Drawings
FIG. 1 is a graph showing the isothermal adsorption and desorption of nitrogen from the photocatalytic biochar composite material according to examples 1-4;
FIG. 2 is a graph of removal rate of methylene blue versus time for photocatalytic biochar composite UBC400-700 under natural light in example 5;
FIG. 3 is a comparison of FTIR of example 5 before and after photocatalytic adsorption of methylene blue by a photocatalytic biochar composite UBC600 under natural light, wherein,
FIG. 3 (a) is a graph of surface organic functional groups of a photocatalytic biochar composite material UBC600 before and after wastewater treatment;
FIG. 3 (b) is 1000-400cm -1 Organic functional group patterns of surfaces before and after wastewater treatment by using a band photocatalytic biochar composite material UBC 600;
figure 4 (a) is a methylene blue photocatalytic degradation mechanism,
FIG. 4 (b) shows Zn 2+ An electron transfer schematic;
FIG. 5 (a) is an SEM photograph of a photocatalytic biochar composite material UBC600 before treating wastewater,
FIG. 5 (b) is an SEM photograph of a photocatalytic biochar composite material UBC600 after treating wastewater,
FIG. 5 (c) is an EDX-ray photograph of a photocatalytic biochar composite material UBC600 prior to treating wastewater,
FIG. 5 (d) is an EDX-ray photograph of a photocatalytic biochar composite material UBC600 prior to treating wastewater;
FIG. 6 is a graph showing the comparative curves of the removal rate of methylene blue with respect to time under the condition of natural light and light-shielding for the photocatalytic biochar composite material UBC400-700 in example 5 and comparative example 1, wherein,
FIG. 6 (a) is a graph showing the comparison of the removal rate of methylene blue by the photocatalytic biochar composite material UBC400 under the conditions of natural light and light shielding,
FIG. 6 (b) is a graph showing the comparative graph of the removal rate of methylene blue by the photocatalytic biochar composite material UBC500 under the conditions of natural light and light shielding,
FIG. 6 (c) is a graph showing the comparison of the removal rate of methylene blue by the photocatalytic biochar composite material UBC600 under the conditions of natural light and light shielding,
FIG. 6 (d) is a graph showing the comparison of the removal rate of methylene blue by the photocatalytic biochar composite material UBC700 under the conditions of natural light and light shielding;
fig. 7 is a kinetic model of the photocatalytic biochar composite material UBC600 according to example 5 and comparative example 1 for removing methylene blue under natural light and light-shielding conditions, wherein,
figure 7 (a) is a quasi-first order kinetic model under natural light,
figure 7 (b) is a quasi-first order kinetic model in the dark,
figure 7 (c) is a quasi-secondary kinetic model under natural light,
FIG. 7 (d) is a quasi-secondary kinetic model under light-shielding conditions;
FIG. 8 is a graph showing degradation rate of methylene blue at different initial concentrations by photocatalytic adsorption of a photocatalytic biochar composite UBC600 under natural light in examples 5 and 6;
FIG. 9 is an isothermal adsorption model for removing methylene blue from photocatalytic biochar composite UBC600 under natural light in examples 5 and 6;
FIG. 10 is a comparison of methylene blue removal rates after regeneration cycles of photocatalytic biochar composite UBC400-700 in example 7.
Detailed Description
The invention provides a photocatalytic biochar composite material, which comprises biochar and ZnO/ZnS mixture, wherein the ZnO/ZnS mixture is loaded in micropores of the biochar and/or on the surface of the biochar.
The present invention will be further described in detail with reference to specific examples for a better understanding of the present invention by those skilled in the art. It should be understood by those skilled in the art that this should not be construed as limiting the scope of the claims. It should also be noted that the reagents and apparatus of the invention are commercially available without any particular explanation.
In the embodiment of the invention, UBC400 ℃ represents the photocatalytic biochar composite material prepared at the carbonization temperature of 400 ℃.
The photocatalytic biochar composite material can be recycled by a method comprising the following steps: the photocatalytic biochar composite material is collected, dried for 8-24 hours at the temperature of 80-160 ℃, added into dye wastewater again for recycling, and the degradation rate is not obviously reduced after multiple cycles. If the removal effect of the photocatalytic biochar composite material is obviously reduced, the photocatalytic biochar composite material can be recovered after being dried for a week or more under natural light.
Specific sources of reagents used in the present invention are listed in Table 1 below.
Table 1 raw materials and instruments used in examples and comparative examples
The invention is further described below in connection with the drawings and the specific preferred embodiments, but the scope of protection of the invention is not limited thereby.
Example 1
(1) Crushing corn stalk waste, sieving with 50 mesh sieveThe method comprises the steps of carrying out a first treatment on the surface of the Then adding 30g of sieved corn stalk powder into 60g of ZnSO with the temperature of 80 ℃ and the mass concentration of 3% 4 Stirring and immersing in the aqueous solution at the speed of 200r/min for 8h, taking out, washing with deionized water until the aqueous solution is neutral, and then placing the washed powder in a vacuum drying oven at 80 ℃ for drying for more than 12h to obtain the precursor of the composite material.
Simultaneously crushing corn straw waste, and sieving with a 50-mesh sieve; and then 30g of sieved corn stalk powder is used for preparing the biochar material.
(2) Respectively placing the composite material precursor and the corn stalk powder into N 2 In a tubular furnace Dan Yingmin with the flow rate of 60ml/min, heating to 100 ℃ at the heating rate of 8 ℃/min, preserving heat for 1h, heating to 400 ℃ at the heating rate of 8 ℃/min, preserving heat for 2h, and naturally cooling to obtain the photocatalytic biochar composite material UBC 400.7 g and the biochar BC 400.5 g.
Example 2
30g of composite material precursor and 30g of sieved corn stalk powder are prepared according to the step (1) of the embodiment 1, wherein the difference is that the temperature is raised to 500 ℃ in the step (2), the temperature is kept for 2 hours, and the photocatalytic biochar composite material UBC 500.1 g and the biochar BC 500.0 g are obtained after natural cooling.
Example 3
30g of composite material precursor and 30g of sieved corn stalk powder are prepared according to the step (1) of the embodiment 1, wherein the difference is that the temperature is raised to 600 ℃ in the step (2), the temperature is kept for 2 hours, and natural cooling is carried out, so as to obtain the photocatalytic biochar composite material UBC 600.6 g and the biochar BC 600.5 g.
Example 4
30g of composite material precursor and 30g of sieved corn stalk powder are prepared according to the step (1) of the embodiment 1, wherein the difference is that the temperature is raised to 700 ℃ in the step (2), the temperature is kept for 2 hours, and the photocatalytic biochar composite material UBC 700.1 g and the biochar BC 700.3 g are obtained after natural cooling.
Example 5
S1, preparing 10mg/L methylene blue simulated wastewater, regulating the pH value to 7.0+/-0.2, and regulating the COD cr The value is 77.2mg/L, 25mL are respectively put into 4 conical flasks of 100 mL;
s2, directly adding the photocatalytic biochar composite materials UBC400, UBC500, UBC600 and UBC700 prepared in the examples 1-4 into 4 parts of wastewater according to the ratio of 4g/L, respectively, placing the materials in a constant-temperature oscillator with the temperature of 30 ℃ under the natural light condition, and carrying out the oscillation frequency about 275 times/min for 4 hours;
s3, precipitating and filtering to obtain wastewater after advanced treatment.
Example 6
S1, respectively preparing 4 different types of wastewater:
(1) Methylene blue concentration is 30mg/L, COD cr A value of 85.3mg/L, a pH value of 7.0 + -0.2,
(2) Methylene blue concentration is 50mg/L, COD cr 89.7mg/L of simulated wastewater with pH value of 7.0+/-0.2,
(3) The methylene blue concentration is 70mg/L, COD cr A value of 125.7mg/L, a pH value of 7.0 + -0.2,
(4) The methylene blue concentration is 100mg/L, COD cr A value of 168.0mg/L, a pH value of 7.0 + -0.2,
putting 25mL of the 4 kinds of wastewater into 4 100mL conical flasks respectively;
s2, directly adding the photocatalytic adsorbent UBC600 prepared in the embodiment 3 into 4 parts of wastewater according to the ratio of 4g/L, placing the wastewater in a constant-temperature oscillator with the temperature of 30 ℃ under natural light, and carrying out oscillation frequency about 275 times/min for 24 hours;
s3, precipitating and filtering to obtain wastewater after advanced treatment.
Example 7
(1) The photocatalytic biochar composite materials UBC400, UBC500, UBC600 and UBC700 used in example 5 were collected after filtration, and dried in an oven at 110 ℃ for 12 hours to obtain regenerated photocatalytic biochar composite materials UBC400, UBC500, UBC600 and UBC700.
(2) S1, preparing 25mL of methylene blue simulated wastewater with the concentration of 10mg/L, putting the wastewater into a100 mL conical flask, regulating the pH value to 7.0+/-0.2, and regulating the CODcr value to 77.2mg/L;
s2, directly adding regenerated photocatalytic biochar composite materials UBC400, UBC500, UBC600 and UBC700 into the wastewater according to the ratio of 4g/L, placing the wastewater in a constant-temperature oscillator under the natural light condition, keeping the temperature at 30 ℃ and the oscillation frequency at about 275 times/min, and adsorbing for 4 hours;
s3, precipitating and filtering to obtain the deeply treated wastewater.
(3) The above steps were cycled five times.
Comparative example 1
S1, preparing 10mg/L methylene blue simulated wastewater, regulating the pH value to 7.0+/-0.2, and regulating the COD cr The value is 77.2mg/L, 25mL are respectively put into 4 conical flasks of 100 mL;
s2, directly adding the photocatalytic biochar composite materials UBC400, UBC500, UBC600 and UBC700 prepared in the examples 1-4 into 4 parts of wastewater according to the ratio of 4g/L, placing the wastewater in a constant-temperature oscillator with the temperature of 30 ℃ under the condition of avoiding light, and carrying out oscillation frequency about 275 times/min for 4 hours;
s3, precipitating and filtering to obtain wastewater after advanced treatment.
Characterization of photocatalytic Properties of examples and comparative examples
The photocatalytic biochar composite materials UBC400, UBC500, UBC600, UBC700 prepared in examples 1 to 4 were tested for nitrogen adsorption-desorption isotherms at 77K using a Brunauer-Emmett-Teller (BET, quantachrome NOVA 1000) and the resulting curves are shown in fig. 1.
By the multi-BET method (P/P 0 0.005-0.02) to calculate the specific surface area of the material.
BHJ analysis calculated the mean pore size of the material.
The pore volume is defined by P/P 0 N at=0.95 2 And (5) calculating an adsorption value.
The specific surface area, average pore diameter and pore volume results of the photocatalytic biochar composite materials prepared in examples 1 to 4 are shown in table 2.
The removal rate of the wastewater is calculated by the formula: removal rate= (C 0 -C t )/C 0 Calculated as x 100%. Calculating the concentration C of methylene blue in the wastewater under different treatment time by using ultraviolet spectrophotometry t The initial concentration of methylene blue is noted as C 0 . The removal rate versus time curve of the photocatalytic biochar composite material for methylene blue in example 5 is shown in fig. 2, wherein the removal rate for 4 hours is shown in table 2.
CODcr is a method using potassium dichromate (K 2 Cr 2 O 7 ) The chemical oxygen consumption measured as an oxidant, i.e., dichromate index. In example 5, wastewater after 4 hours of advanced treatment was subjected to a dichromate method (HJ 828-2017, "determination of COD of Water quality) cr The results are detailed in Table 2.
The chromaticity of the water was determined by platinum cobalt colorimetry (ISO 7887-1985 test and determination of Water quality color). The chroma value of the raw wastewater solution in example 5 is 116.1, and the chroma value of the wastewater after 4 hours of advanced treatment is shown in Table 2.
The actual loading of the ZnO/ZnS mixture is calculated by the formula: load factor= (W) UBC -W BC )/W UBC Calculated as x100%, where W UBC And W is BC The quality of the photocatalytic biochar composite material and the quality of the straw biochar at different pyrolysis temperatures are given in examples 1-4.
TABLE 2 structural parameters of photocatalytic biochar composite Material and parameters of wastewater after 4h of treatment under natural light
As can be seen from FIG. 2 and Table 2, the removal rate of the photocatalytic biochar composite material UBC400-700 to methylene blue is increased with time until the removal rate is balanced, the removal rate is close to or reaches 100% in 4 hours, and the COD is obtained cr The value and the chromaticity are both higher than the industrial wastewater recycling standard (GB/T19923-2005 industrial wastewater quality for urban wastewater recycling). Wherein, the removal rate of the photocatalytic biochar composite material UBC600 for treating wastewater for 20min reaches 94.07 percent, the removal rate of the photocatalytic biochar composite material UBC for 1h reaches 100 percent, and the COD of the wastewater after 4h treatment is realized cr The value and the chromaticity are both 0.0, and the treatment effect is optimal. The degradation performance of the photocatalytic biochar composite material on methylene blue is arranged from high to low as follows: UBC600 > UBC700 > UBC500 > UBC400.
The organic functional groups on the surface of the photocatalytic biochar composite material UBC600 before and after wastewater treatment in example 5 are analyzed by using a Fourier infrared spectrophotometer, and the results are shown in the figure3, wherein FIG. 3 (a) shows the surface organic functional group diagram before and after the photocatalytic biochar composite material UBC600 is used for treating wastewater, and FIG. 3 (b) is further enlarged by 1000-400cm -1 Is a comparison curve of (2). As can be seen from FIG. 3 (b), the photocatalytic biochar composite material UBC600 before wastewater treatment is 444cm -1 The wide strong peak is the accumulation of C-C vibration absorption peaks of various aromatic groups on the carbon surface, so that methylene blue organic macromolecules and aromatic derivatives are easy to generate large pi conjugated adsorption and further generate photocatalytic degradation; the photocatalytic biochar composite material UBC600 after wastewater treatment is 419cm -1 、450cm -1 The small peaks appear at the two positions, namely the C-C vibration absorption peaks of meta-position and para-position binary substituted benzene, which should be intermediate products after methylene blue photocatalytic degradation, and are shown in figure 4 (a). The N-H external deformation vibration is characteristic absorption of amines in a fingerprint area, and is wide and strong. 878-752cm of the photocatalytic biochar composite material UBC600 appears before and after wastewater treatment -1 A plurality of small and wide peaks are arranged on the surface of the biochar, namely-NH 2 The primary amine structure, but the peak of the part of the UBC600 of the photocatalysis charcoal composite material after treatment is weakened or disappeared, which shows that the N-containing group on the surface is an effective adsorption point of methylene blue. 1565cm -1 The tiny peak is-NH-vibration, the strength of the peak of the processed photocatalytic biochar composite material UBC600 is weakened, and partial adsorption exists. UBC600 before treatment at 1379cm -1 The minor peak is an aromatic tertiary amine
C-N vibration of 1702cm -1 The vibration of-CHO, the two tiny peaks remained unchanged after treatment, indicating that neither tertiary amine nor aldehyde groups are adsorption sites for methylene blue. And a new 1327cm appears on the treated photocatalytic biochar composite material UBC600 -1 The frequency is reduced at a tiny peak, which indicates that a new product containing a fat and aromatic mixed primary secondary amine structure appears, and further proves that methylene blue is degraded by photocatalysis. The UBC600 of the photocatalysis biological carbon composite material before and after the treatment is 3400cm -1 The large and wide peaks all appear in the positions belong to the associated-OH in the biochar molecules, and the peak shape of the association body is wider. The greater the degree of association, the broader the peak and the lower the waveAnd (5) number shifting. 2922. 2844, 2337cm -1 The small peak comes from lattice vibration of ZnO on the surface of the carbon, and the peak is basically disappeared after adsorption because the surface is covered by methylene blue and products thereof. Zn (zinc) 2+ A schematic diagram of electron transfer after excitation by light quanta is shown in FIG. 4 (b).
And (3) performing vacuum suction filtration on the used photocatalytic biochar composite material UBC600, and drying. The microporous morphology of the photocatalytic biochar composite material UBC600 before and after the treatment of methylene blue under natural light was observed by a Scanning Electron Microscope (SEM), and the results are shown in fig. 5 (a) and (b). As can be seen from fig. 5 (a) and (b), the photocatalytic biochar is an adsorption material with abundant microporous structures, and has good adsorption performance without damaging the microporous structures after use. The photocatalytic biochar composite material UBC600 was analyzed for the types and contents of surface elements of the materials before and after use by using an energy spectrometer (EDX), and the results are shown in fig. 5 (c), (d) and table 3. As can be seen from table 3, the front surface of the photocatalytic biochar composite material UBC600 is mainly C, O, S, zn, and Zn is mainly present in the state of ZnO and ZnS; after the photocatalytic biochar composite material UBC600 is regenerated, the mass percentage of O on the surface of the material is increased, and a small amount of P and K elements are adsorbed from the wastewater, so that the mass percentage of Zn and S is slightly reduced. In general, the photocatalytic biochar composite material UBC600 has substantially unchanged photocatalytic active ingredients on the surface before and after use, and has increased O-containing groups on the surface, probably because catalytic degradation products of organic matter adsorb on the surface of the carbon material.
TABLE 3 results of elemental analysis of the photocatalytic biochar composite UBC600 before and after use
| UBC600 | Cwt.％ | Owt.％ | Swt.％ | Znwt.％ | Pwt.％ | Kwt.％ |
| Before use | 46.19 | 16.30 | 7.33 | 30.19 | ||
| After use | 42.92 | 24.49 | 5.72 | 22.01 | 3.93 | 0.93 |
The removal rate-time curve of the photocatalytic biochar composite material UBC400-700 in comparative example 5 and comparative example 1 on methylene blue under natural light and light-shielding conditions further demonstrates the effect of natural light in a photocatalytic degradation system for degrading methylene blue, as shown in FIG. 6. Wherein fig. 6 (a) is a graph comparing the removal rate of methylene blue with respect to time under natural light and light-shielding conditions of the photocatalytic biochar composite material UBC400, fig. 6 (b) is a graph comparing the removal rate of methylene blue with respect to time under natural light and light-shielding conditions of the photocatalytic biochar composite material UBC500, fig. 6 (c) is a graph comparing the removal rate of methylene blue with respect to time of the photocatalytic biochar composite material UBC600 under natural light and light-shielding conditions of the photocatalytic biochar composite material UBC700, and fig. 6 (d) is a graph comparing the removal rate of methylene blue with respect to time under natural light and light-shielding conditions of the photocatalytic biochar composite material UBC700. In general, the photocatalytic biochar composite material UBC400-700 shows that the degradation effect of methylene blue under the natural light condition is better than that under the light-shielding condition, and the natural light condition has more remarkable superiority than the light-shielding condition along with the rising of the pyrolysis temperature of the photocatalytic biochar.
Fig. 7 is a quasi-primary dynamics and quasi-secondary dynamics model of the photocatalytic biochar composite material UBC600 according to example 5 and comparative example 1 for removing methylene blue under natural light and light-shielding conditions, wherein fig. 7 (a) is a quasi-primary dynamics model under natural light, fig. 7 (b) is a quasi-primary dynamics model under light-shielding conditions, fig. 7 (c) is a quasi-secondary dynamics model under natural light, and fig. 7 (d) is a quasi-secondary dynamics model under light-shielding conditions. The model equation is as follows:
quasi-first order dynamics model:
quasi-second order dynamics model:
in which Q e Fitting the equilibrium adsorption quantity with the unit of mg/g;
Q t the adsorption quantity is the unit mg/g at the moment t;
k 1 is the quasi-first-order adsorption rate constant, unit min -1 ；
k 2 Is the quasi-secondary adsorption rate constant, unit g.mg -1 ·min -1 ；
k 2 0 ＝k 2 Q e 2 The initial adsorption rate constant is mg.g -1 ·min -1 。
Overall, the process of removing methylene blue from the photocatalytic biochar composite material UBC600 under the natural light and light-shielding conditions is more in accordance with a quasi-secondary kinetic model, and the calculation result of kinetic parameters is shown in table 4.
TABLE 4 Paramy Primary kinetics and Paramy Secondary kinetics parameters of photocatalytic biochar composite UBC600 for removal of methylene blue under Natural light and light-protected conditions
FIG. 8 is a graph showing the removal rate versus time of methylene blue at initial concentrations of 10, 30, 50, 70, 100mg/L, respectively, for the photocatalytic biochar composite UBC600 in examples 5 and 6, when treated with natural light. As can be seen from fig. 8, the removal performance of the photocatalytic biochar composite UBC600 gradually decreases with increasing initial concentration of methylene blue, because the photocatalytic adsorption of the photocatalytic biochar reaches equilibrium for a certain period of time, but the treatment time is continued to be prolonged to 24 hours, even for several days, and the removal rate of methylene blue will continue to increase, which coincides with the system quasi-kinetic adsorption rate constant in table 4. The above system was fitted with Langmuir isothermal adsorption model and Freundlich isothermal adsorption model, respectively, and the results are shown in FIG. 9.
The isothermal adsorption model equation is as follows:
langmuir isothermal adsorption model:
wherein C is e Is the equilibrium concentration of the solution, in mg/L;
Q max is the maximum adsorption amount (or called saturation adsorption amount), unit mg/g;
K L units of L/g are Langmuir constants related to affinity and adsorption energy of the binding site.
The Langmuir molecular adsorption model has quite uniform adsorption effect on the solid surface, can better represent experimental results when the adsorption is limited to a monomolecular layer, and has poor consistency with the experimental system.
Freundlich isothermal adsorption model
In which Q e For the adsorption amount when the adsorption reaches equilibrium, the unit is mg/g;
C e the unit of the concentration of the adsorbate in the solution is mg/L at the adsorption equilibrium;
K F is a constant related to adsorption capacity and adsorption strength under the Freundlich model;
1/n is a Freundlich constant, and is generally between 0 and 1, and the value of the constant indicates the strength of the influence of concentration on the adsorption amount.
The smaller 1/n, the better the adsorption performance. 1/n is 0.1 to 0.5, which means that the adsorption is easy, and the adsorption is difficult when 1/n is more than 2.
Compared with the Langmuir isothermal adsorption model, the system is more in line with the Freundlich isothermal adsorption model, and the calculation results of corresponding parameters are shown in Table 5. The system 1/n= 0.13107 shows that the photocatalytic biochar composite material UBC600 is a material which is easy to adsorb for methylene blue and has larger K F The n value is an indication that the adsorbent has better adsorption performance.
TABLE 5 Freundlich isothermal adsorption model parameters for removing methylene blue under natural light conditions of photocatalytic biochar composite UBC600
| K F | n | R 2 |
| 2.18595 | 7.62951 | 0.91463 |
The photocatalytic biochar can repeatedly treat the organic dye wastewater for many times through a simple regeneration process, and has a relatively stable removal effect, and has important significance for realizing low cost of the organic dye wastewater treatment.
By the invention, the photocatalytic biochar can be recovered by treating the printing and dyeing wastewater with the photocatalytic biochar, and recycling is realized, and the photocatalytic biochar has recycling property. Example 7 compares the 4h removal rate of methylene blue after five regeneration cycles of the photocatalytic biochar composite material UBC400-700, and the results are shown in fig. 10. As can be seen from FIG. 10, after five times of recycling, the removal rate of methylene blue for 4 hours is still maintained to be more than 95%, which proves that the photocatalytic biochar has good recycling performance.
Prior art facility and Low-cost fabrication of ZnObiochar nanocomposites fromjute fibers for efficient and stable photodegradation ofmethylene blue dye, mingxin Chen et al Journal of Analytical and Applied Pyrolysis 139 (2019) 319-332. The prior art is a biochar material only loaded with ZnO. The specific surface area of the material provided in the prior art is 4.71-62.2 m 2 ·g -1 The photocatalytic biochar composite material has larger specific surface area (300-550 m) 2 ·g -1 ). The removal rate of the ZnO-loaded biochar material in the prior art after degradation for 60 minutes under the ultraviolet light condition is less than 100%, while the removal rate of the photocatalytic biochar composite material in the invention after degradation for 60 minutes under natural light can reach 100%, and the COD (chemical oxygen demand) cr The chromaticity was 0.0.
The above description is merely a basic description of the inventive concept, and any equivalent transformation according to the technical solution of the present invention shall fall within the protection scope of the present invention.
Claims (40)
1. A method for treating printing and dyeing wastewater, which is characterized by comprising the following steps:
adding the recyclable photocatalytic biochar composite material into printing and dyeing wastewater to be treated, and oscillating under natural light to perform catalytic degradation reaction;
the photocatalytic biochar composite material comprises biochar and a ZnO/ZnS mixture, wherein the loading rate of the ZnO/ZnS mixture is 15-20%, and the ZnO/ZnS mixture is loaded in micropores and/or on the surface of the biochar;
the preparation method of the photocatalytic biochar composite material comprises the following steps:
(1) Dipping straw powder into zinc source water solution, and then drying to prepare a composite material precursor;
(2) Placing the composite material precursor obtained in the step (1) in inert gas atmosphere, preserving heat at 100-150 ℃, and then heating for pyrolysis to obtain the photocatalytic biochar composite material;
the pyrolysis temperature in the step (2) is 500-700 ℃;
the CODcr value of the organic dye of the printing and dyeing wastewater is lower than 200mg/L, and the pH value of the printing and dyeing wastewater is 6-9;
wherein, 4g/L of the photocatalytic charcoal composite material is added into a solution with CODcr value of 75-170mg/L for 1-30h, the CODcr value of the solution is 0-11mg/L, and the degradation rate is 97-100% after 1-30h of the photocatalytic charcoal composite material is added into a solution with 10-100mg/L of methylene blue.
2. The printing and dyeing wastewater treatment method according to claim 1, wherein the mass percentage of Zn element in the surface element of the photocatalytic biochar composite material is 25% -40%.
3. The method for treating printing and dyeing wastewater according to claim 1, wherein the specific surface area of the photocatalytic biochar composite material is 300-500m 2 •g -1 。
4. The method for treating printing and dyeing wastewater according to claim 2, wherein the specific surface area of the photocatalytic biochar composite material is 300-500m 2 •g -1 。
5. The method for treating printing and dyeing wastewater according to claim 1, wherein the specific surface area of the photocatalytic biochar composite material is 330-480m 2 •g -1 。
6. The printing and dyeing wastewater treatment method according to claim 1, wherein the photocatalytic biochar composite material has a pore volume of 0.220-0.330 cm 3 /g。
7. The printing and dyeing wastewater treatment method according to claim 2, wherein the pore volume of the photocatalytic biochar composite material is 0.220-0.330 cm 3 /g。
8. The method for treating printing and dyeing wastewater according to claim 1, wherein the pore volume of the photocatalytic biochar composite material is 0.240-0.330 and 0.330cm 3 /g。
9. The method for treating printing and dyeing wastewater according to any one of claims 1 to 8, wherein the straw in step (1) is any one of tobacco stalk, corn stalk, myotonin stalk, sorghum stalk and a mixture thereof.
10. The method for treating printing and dyeing wastewater according to any one of claims 1 to 8, wherein the zinc source aqueous solution in the step (1) is ZnSO 4 An aqueous solution.
11. The method for treating printing and dyeing wastewater according to claim 10, wherein the ZnSO is one of the following 4 The mass concentration of the aqueous solution is 1% -5%.
12. The printing and dyeing wastewater treatment process according to claim 10The method is characterized in that the ZnSO is 4 The mass concentration of the aqueous solution is 3% -5%.
13. The method for treating printing and dyeing wastewater according to claim 10, wherein the ZnSO is one of the following 4 The mass concentration of the solution is 3%.
14. The method for treating printing and dyeing wastewater according to claim 10, wherein the ZnSO is one of the following 4 The mass ratio of the aqueous solution to the straw powder is (2-4): 1.
15. The method for treating printing and dyeing wastewater according to claim 11, wherein the ZnSO is one of the following 4 The mass ratio of the aqueous solution to the straw powder is (2-4): 1.
16. The method for treating printing and dyeing wastewater according to claim 10, wherein the ZnSO is one of the following 4 The mass ratio of the aqueous solution to the straw powder is (2-3): 1.
17. The method for treating printing and dyeing wastewater according to claim 10, wherein the ZnSO in the step (1) 4 The temperature of the aqueous solution is 60-100 ℃.
18. The method for treating printing and dyeing wastewater according to any one of claims 11 to 16, wherein the ZnSO in the step (1) 4 The temperature of the aqueous solution is 60-100 ℃.
19. The method for treating printing and dyeing wastewater according to claim 10, wherein the ZnSO in the step (1) 4 The aqueous solution temperature was 80 ℃.
20. The method for treating printing and dyeing wastewater according to claim 10, wherein the straw powder in step (1) is obtained by using ZnSO as a raw material 4 The soaking time in the solution is 5-12 h.
21. According to claim 10A printing and dyeing wastewater treatment method is characterized in that the straw powder in the step (1) is prepared in ZnSO 4 The soaking time in the solution is 8-10 h.
22. The method for treating printing and dyeing wastewater according to claim 10, wherein the stirring rate in the step (1) is 100-400r/min.
23. The method for treating printing and dyeing wastewater according to claim 10, wherein the stirring time in the step (1) is 3-5 hours.
24. The method for treating printing and dyeing wastewater according to claim 10, wherein the stirring time in the step (1) is 5 hours.
25. The method for treating printing and dyeing wastewater according to claim 10, wherein the drying temperature in the step (1) is 60-100 ℃.
26. The method for treating printing and dyeing wastewater according to claim 10, wherein the drying temperature in the step (1) is 70-90 ℃.
27. The method for treating printing and dyeing wastewater according to claim 10, wherein the drying time in the step (1) is 10 to 24 hours.
28. The method for treating printing and dyeing wastewater according to claim 10, wherein the drying time in the step (1) is 10-13 hours.
29. The method for treating printing and dyeing wastewater according to any one of claims 1 to 8, wherein the inert gas atmosphere holding temperature in the step (2) is 100 to 120 ℃.
30. The method for treating printing and dyeing wastewater according to any one of claims 1 to 8, wherein the time of the heat preservation in the step (2) is 1h to 5h.
31. The method for treating printing and dyeing wastewater according to any one of claims 1 to 8, wherein the time of heat preservation in the step (2) is 1.5 to 3 hours.
32. The method for treating printing and dyeing wastewater according to any one of claims 1 to 8, wherein the pyrolysis temperature in the step (2) is 600 ℃.
33. The method for treating printing and dyeing wastewater according to any one of claims 1 to 8, wherein the heating rate in the step (2) is 8 to 10 ℃/min.
34. The method for treating printing and dyeing wastewater according to any one of claims 1 to 8, wherein the pyrolysis time in the step (2) is 1 to 4 hours and the pyrolysis time is 2 to 2.5 hours.
35. The method for treating printing and dyeing wastewater according to any one of claims 1 to 8, wherein the inert gas in the step (2) is N 2 Or Ar.
36. The method for treating printing and dyeing wastewater according to any one of claims 1 to 8, wherein the flow rate of the inert gas in the step (2) is 40 to 100ml/min.
37. The method for treating printing and dyeing wastewater according to any one of claims 1 to 8, wherein the pyrolysis reaction of step (2) is performed in a tube furnace.
38. The method for treating printing and dyeing wastewater according to any one of claims 1 to 8, wherein the shaking is performed at a temperature of 28 to 32 ℃.
39. The method for treating printing and dyeing wastewater according to any one of claims 1 to 8, wherein the frequency of the oscillation is 250 to 300 times/min.
40. The method for treating printing and dyeing wastewater according to any one of claims 1 to 8, wherein the time of the shaking is 1 to 30 hours.
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