Application of pulping and papermaking wastewater sludge in photo-thermal field

Abstract

The invention discloses an application of pulping and papermaking wastewater sludge in the photo-thermal field, belongs to the technical field of sludge recycling, and solves the problems of difficulty in realizing high-added-value resource utilization of the pulping and papermaking wastewater sludge and how to safely, efficiently and greenly treat the pulping and papermaking wastewater sludge at present. The specific application comprises the steps of carbonization of pulping and papermaking wastewater sludge, preparation of the photo-thermal conversion device and use of the photo-thermal conversion device which are carried out in sequence. The result shows that the carbonized product of the pulping and papermaking wastewater sludge has the average light absorptivity exceeding 93%, the photothermal conversion film has excellent photothermal conversion capacity and stability, and efficient and stable interface evaporation can be achieved when the photothermal conversion film is combined with the solar interface evaporation technology to be applied to seawater desalination and sewage treatment.

Description

Technical Field

[0001] The invention belongs to the technical field of sludge resource utilization, and specifically relates to the application of pulping and papermaking wastewater sludge in the field of photothermal energy. Background Art

[0002] Papermaking sludge mainly comes from the dehydration, pressing, washing and other processes in the pulping process. In the pulping process, the wood is chopped and water is added, and the lignin and cellulose are separated by mechanical force to form pulp. This process will produce a large amount of wastewater, which contains a large amount of suspended matter and dissolved matter. These substances are dehydrated, pressed, washed and other processes to form sludge. The organic matter content of papermaking sludge is as high as 50%. It mainly contains high-molecular organic matter such as cellulose, hemicellulose, lignin, as well as fillers and coagulants. It is a biomass resource. However, due to the complex components of papermaking sludge, it is very difficult to handle and is prone to secondary pollution to the environment. Therefore, when treating papermaking sludge, more attention should be paid to the resource utilization of sludge and the full and reasonable use of papermaking sludge. At present, the existing sludge treatment and disposal methods mainly include landfill, composting, natural drying, incineration, cement building materials and other methods. Traditional landfill and incineration can no longer meet the needs of the rapidly developing modern society for environmental protection and economic benefits. Therefore, developing high-value-added sludge resource utilization methods is an urgent issue for the harmless disposal of sludge.

[0003] There is a related technology that adds calcium chloride to the remaining papermaking sludge for pyrolysis, and then adds hydrochloric acid solution to remove metal oxides after pyrolysis to obtain sludge-based biochar adsorption materials for treating antibiotic-containing wastewater. There is also a related technology that mixes papermaking sludge with cellulose and guar gum to prepare hydrogel and then pyrolyzes it at high temperature to obtain a carbon-based electrocatalyst for degrading dye wastewater. Although the above technologies disclose the process of preparing biochar materials by recycling papermaking sludge at high temperature, the preparation process is still relatively cumbersome, and the resulting materials do not have competitive advantages in their respective application fields. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes an application of pulping and papermaking wastewater sludge in the field of photothermal, which solves the problems of low economic benefits, high mud quality requirements, and easy secondary pollution in the existing pulping and papermaking wastewater sludge disposal methods. On the other hand, the obtained product is applied to the solar interface evaporation treatment of papermaking wastewater, which can also solve the current problem of how to efficiently and cleanly treat papermaking wastewater.

[0005] According to an embodiment of the first aspect of the present invention, there is provided an application of pulping and papermaking wastewater sludge in the field of photothermal energy.

[0006] The control method according to the embodiment of the present invention has at least the following beneficial effects:

[0007] At present, the resource utilization of pulping and papermaking wastewater sludge is mainly to prepare it into biochar material and use it for direct water adsorption; the present invention creatively applies it to the field of introducing photothermal interface, utilizes the black appearance of the pulping and papermaking wastewater sludge after carbonization to improve the light absorption performance, and achieves excellent performance in evaporating water at the solar energy interface, providing a new idea for the resource utilization of pulping and papermaking wastewater sludge.

[0008] After the pulping and papermaking wastewater sludge is applied to the photothermal field, it has excellent light absorption capacity in the range of 200-2500nm solar radiation wavelength and thermal stability, ensuring that the application of the carbonized product of the pulping and papermaking wastewater sludge in the solar interface evaporation technology will not cause secondary pollution. Its light absorption capacity and thermal stability have significant competitive advantages in the photothermal field.

[0009] According to some embodiments of the present invention, the water content of the pulping and papermaking wastewater sludge is 50-80%, the lignin content is 5-30%, the crude fiber content is 10-20%, the organic matter content is 40-80%, and the carbon content is 15-50%. Among them, the organic matter includes lignin and crude fiber. The carbon element includes carbon elements in lignin and carbon fiber. In traditional technology, if biochar materials are to play an excellent role in the field of photothermal, it is necessary to re-match the biochar materials and adjust the components therein. In the application provided by the present invention, the composition of the pulping and papermaking waste paper is reasonable, and the performance of the carbonized product in the field of photothermal is very excellent.

[0010] According to some embodiments of the present invention, the moisture content of the pulping and papermaking wastewater sludge is 60-75%, for example, about 65%, 66%, 68%, 70%, 71% or about 73%.

[0011] According to some embodiments of the present invention, the lignin content in the pulping and papermaking wastewater sludge is 7-30%, for example, it may be about 8%, 10%, 15%, 20%, 25% or about 29%.

[0012] According to some embodiments of the present invention, the crude fiber content in the pulping and papermaking wastewater sludge is 13-18%, for example, 14%, 15%, 16% or about 17%.

[0013] According to some embodiments of the present invention, the organic matter content in the pulp and papermaking wastewater sludge is 50-60%, for example, about 52%, 54%, 55%, 56%, 57% or about 58%.

[0014] According to some embodiments of the present invention, the carbon content in the pulp and papermaking wastewater sludge is 20-35%, for example, about 25%, 28% or about 30%.

[0015] According to some embodiments of the present invention, the pH of the pulping and papermaking wastewater sludge is 6 to 8. For example, it may be about 6.5, 7 or about 7.5.

[0016] According to some embodiments of the present invention, the pulping and papermaking wastewater sludge is waste from the pulping and papermaking industry sewage treatment process, that is, the product after precipitation and preliminary filtration of pulping and papermaking sewage.

[0017] According to some embodiments of the present invention, the application includes sequentially carbonizing the pulp and papermaking wastewater sludge, preparing a photothermal conversion device, and using the photothermal conversion device.

[0018] According to some embodiments of the present invention, the carbonization of pulping and papermaking wastewater sludge comprises the following steps:

[0019] S1: dewatering and crushing the pulping and papermaking wastewater sludge;

[0020] S2: The product obtained from high temperature carbonization step S1.

[0021] In the application provided by the present invention, the papermaking wastewater sludge can be transformed into a black carbonized product through a simple high-temperature carbonization process. The carbonized product has excellent performance in the field of photothermal, specifically, high light absorption rate and high stability.

[0022] According to some embodiments of the present invention, in step S1, the dehydration method includes drying. The drying temperature is 90-120° C., for example, about 100° C. or about 110° C. The drying time is 1-3 hours, for example, about 2 hours.

[0023] According to some embodiments of the present invention, in step S1, the crushing method includes grinding.

[0024] According to some embodiments of the present invention, in step S2, the temperature of the high temperature carbonization is 400-700°C. For example, it may be about 500°C, 550°C, 600°C or about 650°C.

[0025] According to some embodiments of the present invention, in step S2, the high temperature carbonization time is 1 to 8 hours, for example, about 2 hours, 3 hours, 4 hours, 5 hours, 6 hours or about 7 hours.

[0026] According to some embodiments of the present invention, in step S2, the heating rate of the high temperature carbonization is 2-10°C·min -1 ; For example, it can be about 5℃·min -1 .

[0027] According to some embodiments of the present invention, in step S2, the high temperature carbonization atmosphere is argon or nitrogen, thereby protecting the carbon in the organic matter from being oxidized and lost.

[0028] According to some embodiments of the present invention, the flow rate of the atmosphere is 20 to 80 mL min -1 For example, it can be about 30 mL min -1 、40mL·min -1 、50mL·min -1 、60mL·min -1 or about 70 mL min -1 .

[0029] According to some embodiments of the present invention, step S2 further includes sequentially cooling and screening after the high-temperature carbonization.

[0030] According to some embodiments of the present invention, the light-to-heat conversion device includes a light-to-heat conversion film or a light-to-heat converter including the light-to-heat conversion film.

[0031] According to some embodiments of the present invention, the light-to-heat conversion film includes a base film and a coating layer provided on the surface of the base film; the raw material for preparing the coating layer includes the carbonization product of the pulping and papermaking wastewater sludge.

[0032] According to some embodiments of the present invention, the base film is at least one of a glass fiber film, rice paper and an organic nylon film.

[0033] According to some embodiments of the present invention, the average light absorption rate of the light-to-heat conversion film in the range of 200-2500 nm is ≥ 93%, for example, about 94%, 95%, 96%, 97% or about 98%.

[0034] According to some embodiments of the present invention, the light-to-heat conversion film has a stable temperature of ≥40° C. under 1 sun intensity, for example, about 41° C. or about 42° C. The time to reach the above stable temperature is ≤10 min.

[0035] According to some embodiments of the present invention, the preparation process of the photothermal conversion film includes slurrying the carbonized product and the binder in a dispersant, and compounding the obtained slurry on the base film. It can be seen that the photothermal conversion film is easy to prepare, has low equipment requirements, has the potential for industrial promotion, and provides a new idea for the high-value-added resource utilization of pulp and paper wastewater sludge.

[0036] According to some embodiments of the present invention, the dispersant is N-methylpyrrolidone, N,N Dimethylformamide, dimethyl sulfoxide, N,N At least one of dimethylacetamide, tetrahydrofuran and ethylene dichloride.

[0037] According to some embodiments of the present invention, the binder is polyvinylidene fluoride and / or polyvinyl pyrrolidone.

[0038] According to some embodiments of the present invention, the binder is used in the form of a dispersion; the concentration of the dispersion is 0.1-3 wt %, for example, about 0.5 wt %, 1.0 wt %, 2.0 wt % or about 2.5 wt %.

[0039] According to some embodiments of the present invention, in the slurry, the mass ratio of the carbonized product, the binder and the dispersant is 10:(0.01-0.8):(100-500). In this ratio, the binder is calculated by the mass of the solid matter therein, and the solvent in its dispersion is not included in the dispersant. Further specifically, the mass ratio of the carbonized product and the binder is 10:0.1-0.6; for example, it can be about 10:0.2, 10:0.3 or about 10:0.5. The mass ratio of the carbonized product and the dispersant is 10:150-200; for example, it can be about 10:160, 10:170, 10:180 or about 10:190.

[0040] According to some embodiments of the present invention, the homogenization method includes ultrasonic dispersion. Specifically, the duration of the ultrasonic dispersion is 0.5 to 3 hours. For example, it can be about 1 hour, 1.5 hours, 2 hours or about 2.5 hours.

[0041] According to some embodiments of the present invention, the composite method of the slurry and the base film includes at least one of vacuum filtration, coating and dipping.

[0042] According to some embodiments of the present invention, the preparation process of the light-to-heat conversion film further includes drying after the compounding, wherein the drying process is baking at a temperature of 50 to 70° C. and a drying time of 10 to 15 hours.

[0043] According to some embodiments of the present invention, the photothermal field includes photothermal desalination or photothermal sewage purification. The sewage purified by the sewage includes papermaking wastewater, that is, the mother liquor of the pulping and papermaking wastewater sludge is obtained. The photothermal method is solar interfacial evaporation technology.

[0044] Traditional water pollution treatment processes are difficult to cope with the complex pollutant treatment in sewage. The present invention combines the carbonization product of pulping and papermaking wastewater sludge as a photothermal material with solar interfacial evaporation technology and applies it to the treatment of papermaking wastewater. The total amount of sewage is greatly reduced through interfacial evaporation. At the same time, solar energy is used as energy, which is green and energy-saving, and has environmental awareness and economic benefits.

[0045] According to some embodiments of the present invention, the papermaking wastewater contains metal ions. The metal ions include Na + Mg 2+ , K + and Ca 2+ At least one of .

[0046] According to some embodiments of the present invention, at 1 kW / m 2 Under the light intensity, the evaporation rate of pure water by the photothermal converter is ≥2.3kg·m -2 ·h -1 ; For example, it can be about 2.4kg·m -2 ·h -1 .

[0047] According to some embodiments of the present invention, at 1 kW / m 2 Under the light intensity, the evaporation rate of seawater by the photothermal converter is ≥2.2kg·m -2 ·h -1 ; For example, it can be about 2.3kg·m -2 ·h -1 .

[0048] According to some embodiments of the present invention, at 1 kW / m 2 Under the light intensity, the evaporation rate of papermaking wastewater by the photothermal converter is ≥2.1kg·m -2 ·h -1 ; For example, it can be about 2.2kg·m -2 ·h -1 or about 2.3 kg·m -2 ·h -1 .

[0049] According to some embodiments of the present invention, at 1 kW / m 2 Under the light intensity, when the photothermal converter is used for water treatment, the removal efficiency of metal ions in the water to be treated is ≥93%; for example, it can be about 94%, 95%, 96%, 97%, 98%, 99% or about 100%.

[0050] If there is no special explanation, the actual meaning of “about” in the present invention is that the error is allowed to be within the range of ±2%, for example, about 100 is actually 100±2%×100.

[0051] Unless otherwise specified, “between” in the present invention includes the number itself, for example, “between 2 and 3” includes the endpoint values ​​2 and 3.

[0052] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which: Figure 1 The appearance diagrams of the carbonized products obtained in Example 1 (A6-6) and Example 2 (B6-6) of the present invention, and the products obtained in Comparative Example 1 (A) and Comparative Example 2 (B);

[0054] Figure 2 Surface images of the light-to-heat conversion films obtained in Example 1 (A6-6) and Example 2 (B6-6) of the present invention;

[0055] Figure 3 The SEM images of the carbonized products obtained in Example 1(a) and Example 2(b) of the present invention;

[0056] Figure 4 The XRD patterns of the powder materials obtained in Examples 1 to 4 and Comparative Examples 1 to 2 are as follows;

[0057] Figure 5 The absorption spectra of the powder materials obtained in Examples 1-2 and Comparative Examples 1-2 in a dry state;

[0058] Figure 6 A schematic diagram of the structure of the photothermal converter used in the present invention;

[0059] Figure 7 The photothermal conversion films obtained in Examples 1 and 2 were exposed to 1 sun intensity (1 kW / m 2 ) The interface temperature changes when pure water evaporates under light;

[0060] Figure 8 The mass reduction curve of the light-to-heat conversion film obtained in Examples 1 to 2 when evaporating different water bodies under the condition of 1 sun intensity;

[0061] Fig. 9 It is the metal ion content of the condensate obtained by evaporating papermaking wastewater using the light-to-heat conversion membrane obtained in Examples 1 to 2. DETAILED DESCRIPTION

[0062] The following will be combined with the embodiments to clearly and completely describe the concept of the present invention and the technical effects produced, so as to fully understand the purpose, characteristics and effects of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0063] Examples of embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention in combination with the specific content of the technical solution.

[0064] Example 1

[0065] This example provides an application of pulp and papermaking wastewater sludge in the field of photothermal energy, which specifically includes the following steps:

[0066] A1. Carbonization of pulping and papermaking wastewater sludge (including steps S1 and S2):

[0067] S1. Pulp and papermaking wastewater sludge A is placed in an oven and dried at 105°C for 2 hours, and the dried sludge A is taken out and ground into powder A for later use.

[0068] The composition of the pulp and papermaking wastewater sludge A used in this example is shown in Table 1.

[0069] Table 1 Composition analysis of pulp and papermaking wastewater sludge A and B used in Examples 1-2

[0070] sample Organic matter / % Ash / % Lignin / % Crude fiber / % Moisture content / % pH A 55.64 44.36 7.71 16.57 70.50 7.56 B 53.47 46.53 29.84 14.24 65.50 6.76

[0071] In Table 1, the crude fiber content is determined in accordance with the national standard GB / T 6434-94 "Determination of crude fiber in feed"; the test method for lignin content is to weigh about 20g of sludge in a beaker, add 50mL of 80℃ hot water, and then add 100mL of 10% NaOH solution to dissolve the lignin in the sludge; the filtrate obtained by suction filtration of the above dissolution system is adjusted to a pH value between 3 and 4 (within this range, it can be any, it does not affect the results) with appropriate amounts of concentrated sulfuric acid and 10% sulfuric acid, respectively, so that the lignin contained in the sludge is completely precipitated; the above precipitation system is kept at 80-90℃ (within this range, it can be any, it does not affect the results) for 50min, so that the upper clear liquid turns yellow-brown, and after suction filtration, the precipitate is washed with water to neutrality, dried and weighed to obtain crude lignin. Organic matter, ash and pH are measured in accordance with the method specified in the national urban construction industry standard CJ / T221.2005 urban sewage treatment plant sludge detection method. The moisture content is measured by the drying loss method.

[0072] S2. Weigh 8.0 g of the powder A obtained in step S1 and place it in a porcelain boat and place it in a tube furnace. Enter argon gas and control the argon flow rate to 40 mL min. -1 , at 5℃·min -1 The temperature was raised from room temperature to 600°C and kept at this temperature for 6 hours. After the temperature inside the tube dropped to room temperature, it was taken out to obtain a carbonized product named A6-6.

[0073] A2. Preparation of light-to-heat conversion film:

[0074] 2.0 g of polyvinylidene fluoride powder was weighed and dissolved in 98 g of N-methylpyrrolidone to obtain a binder dispersion with a concentration of 2 wt %.

[0075] Weigh 0.1 g of A6-6 into a conical flask, then add 18 mL of N-methylpyrrolidone and 2 mL of binder dispersant dispersion, seal the conical flask with a stopper and put it into an ultrasonic machine for dispersion for 2 h to obtain a slurry.

[0076] The slurry was taken out, vacuum filtered onto a glass fiber membrane (base membrane), and placed in an oven for drying at 60° C. for 12 h to obtain a photothermal conversion film, which was cut into discs with a diameter of 3 cm for subsequent experiments and tests.

[0077] A3. Preparation of photothermal converter:

[0078] refer to Figure 6 , assemble the photothermal conversion film, water transfer cotton swab, thermal insulation sponge and beaker (containing the water body to be treated) into a photothermal converter. Specifically, the water transfer cotton swab passes through the thermal insulation sponge to connect the bottom film of the photothermal conversion film and the water body to be treated.

[0079] A4. Use of photothermal converter.

[0080] Example 2

[0081] This example provides an application of pulp and papermaking wastewater sludge in the field of photothermal energy, which is different from Example 1 in that:

[0082] In step S1, the pulping and papermaking wastewater sludge used is of different types, specifically pulping and papermaking wastewater sludge B, the composition of which is shown in Table 1;

[0083] Correspondingly, the compositions of the subsequent intermediate products and final products are slightly different (described in detail later).

[0084] Example 3

[0085] This example provides an application of pulp and papermaking wastewater sludge in the field of photothermal energy, which is different from Example 1 in that:

[0086] In step S2, the high temperature carbonization temperature is 500°C; the carbonized product is named A5-6.

[0087] Example 4

[0088] This example provides an application of pulp and papermaking wastewater sludge in the field of photothermal energy, which is different from Example 2 in that:

[0089] In step S2, the high temperature carbonization temperature is 500°C; the carbonized product is named B5-6.

[0090] Comparative Example 1

[0091] This example provides an application of pulp and papermaking wastewater sludge in the field of photothermal energy, which is different from Example 1 in that:

[0092] Step S2 is not included, that is, the subsequent light-to-heat conversion film is directly prepared using the powder A obtained in step S1.

[0093] Comparative Example 2

[0094] This example provides an application of pulp and papermaking wastewater sludge in the field of photothermal energy, which is different from Example 2 in that:

[0095] Step S2 is not included, that is, the subsequent light-to-heat conversion film is directly prepared using the powder B obtained in step S1.

[0096] Test Example 1

[0097] In the first aspect of this example, the appearance of the carbonized product A6-6 of Example 1, the carbonized product B6-6 of Example 2, the dried product powder A of Comparative Example 1, and the dried product powder B of Comparative Example 2 were observed. By comparison, it can be clearly observed that the particles of A6-6 and B6-6 are looser and finer than those of A and B, and are dark black as a whole, which means that the carbonized product has good light absorption performance. The specific results are as follows Figure 1 shown.

[0098] In the second aspect of this example, SEM was used to test the microscopic morphology of the carbonized product A6-6 of Example 1 and the carbonized product B6-6 of Example 2. It can be observed that there are many small particles accumulated on the particle surface of the two carbonized products. When magnified, it can be found that there are many holes inside the particles, indicating that the organic matter inside the pulp and paper wastewater sludge has turned into carbon particles attached to the surface of inorganic matter. The rough and porous structure can increase the refraction path of light on the material surface and improve the light absorption rate. The specific results are as follows Figure 3 shown.

[0099] In the third aspect of this example, the carbonized products A6-6 of Example 1, the carbonized products B6-6 of Example 2, the dried product powder A of Comparative Example 1, and the dried product powder B of Comparative Example 2 were tested for carbon and sulfur content. The results are shown in Table 2.

[0100] Table 2 Carbon and sulfur composition of the powder obtained in step A1 of Examples 1-2 and Comparative Examples 1-2

[0101] Element content A A6-6 B B6-6 C (w%) 29.8 28.6 23.8 23.3 S(w%) 0.28 0.70 0.25 1.05

[0102] The results in Table 2 show that the carbon element in the pulping and papermaking wastewater sludge is basically retained after the high-temperature carbonization treatment, which shows that the parameters of the high-temperature carbonization treatment provided by the present invention are appropriate.

[0103] The fourth aspect of this example tests the XRD spectra of the powders obtained in Examples 1 to 4 and Step A1 of Comparative Examples 1 to 2. The results show that the powders obtained in Example 1, Example 3 and Comparative Example 1 all have obvious peaks at 26.7°, 29.7°, 39.5°, 43.3°, 47.6° and 48.4°, which are typical peaks of calcium carbonate. This shows that ventilation protection during high-temperature calcination allows calcium carbonate to remain stably present in the product. The powder obtained in Comparative Example 2 does not show obvious crystalline characteristics, while the powders obtained in Example 2 and Example 4 both show characteristic peaks of calcium silicon compounds, indicating that organic matter is removed and the crystals of inorganic matter are reshaped during the high-temperature carbonization process. The specific test results are as follows: Figure 4 As shown, A6-6 represents Example 1, A5-6 represents Example 3, A represents Comparative Example 1, B represents Comparative Example 2, B6-6 represents Example 2, and B5-6 represents Example 4.

[0104] In the fifth aspect of this example, the appearance of the light-to-heat conversion films obtained in Example 1 and Example 2 was observed. The results showed that the base film and the coating layer were tightly combined and had good adhesion. Specifically, Figure 2 As shown in the figure, A6-6 represents embodiment 1 and B6-6 represents embodiment 2.

[0105] The sixth aspect of this example tests the absorption spectra of the powder materials obtained in step A1 of Examples 1-2 and Comparative Examples 1-2 in a dry state (using a xenon lamp to simulate sunlight irradiation). The average absorbance of A6-6 (Example 1) in the range of 200-2500nm is 93.46%, and that of B6-6 (Example 2) is 96.72%, which exceeds the light absorption rate of most existing photothermal materials. Under the same conditions, the average absorbance of Comparative Example 1 (A) is 64.43%, and the average absorbance of Comparative Example 2 (B) is 71.35%. The specific test results are as follows Figure 5 shown.

[0106] In the seventh aspect of this example, the photothermal converter obtained in Examples 1 and 2 was tested under a 1-sun intensity (1 kW / m 2 ) The interface temperature changes when evaporating water (pure water) under light, the results show that both photothermal conversion films can respond quickly to the light source and reach a stable temperature of 41°C within 10 minutes, indicating that the carbonization product of pulping and papermaking wastewater sludge has good photothermal conversion ability in the application provided by the present invention. The specific test results are as follows Figure 7 shown.

[0107] In the eighth aspect of this example, the evaporation time-water quality change curve was tested when the photothermal converter obtained in Examples 1 and 2 was used for photothermal evaporation of different water bodies. The results showed that the quality changes of the photothermal conversion membrane obtained in Examples 1 and 2 when evaporating pure water, seawater and papermaking wastewater were all linear, which proved that the photothermal conversion membrane can achieve efficient and rapid evaporation when treating different water bodies. Among them, the A6-6 photothermal conversion membrane (Example 1) was 1kW / m 2 The evaporation rates of pure water, seawater and papermaking wastewater AW under the light intensity were 2.32 kg·m -2 ·h -1 , 2.23kg·m -2 ·h -1 and 2.19 kg·m -2 ·h -1 , B6-6 photothermal conversion film (Example 2) at 1kW / m 2 The evaporation rates of pure water, seawater and papermaking wastewater BW under the same light intensity were 2.34 kg·m -2 ·h -1 , 2.26kg·m -2 ·h -1 and 2.28 kg·m -2 ·h -1 Specific test results are as follows: Figure 8 As shown, Figure a corresponds to Example 1, and Figure b corresponds to Example 2.

[0108] In the ninth aspect of this example, the purification effect of the photothermal converter obtained in Example 1 on papermaking wastewater AW (corresponding to the mother liquor of pulping and papermaking wastewater sludge in Example 1) and the photothermal converter obtained in Example 2 on papermaking wastewater BW (corresponding to the mother liquor of pulping and papermaking wastewater sludge in Example 2) was tested. During the test, the illumination condition was 1 kW / m 2 The results showed that Na + Mg 2+ , K + and Ca 2+ The contents of Na in the condensate after being treated with the photothermal converter obtained in Example 1 were 418.5 mg / L, 27.4 mg / L, 34.9 mg / L, and 211.5 mg / L, respectively. + Mg 2+ , K + , Ca 2+ The ion concentration decreased to 4.9 mg / L, 1.7 mg / L, 1.2 mg / L, and 5.6 mg / L; the corresponding Na + Mg 2+ , K + , Ca 2+ The removal rates of ions were 98.83%, 93.68%, 96.69% and 97.33% respectively.+ Mg 2+ , K + and Ca 2+ The contents of Na + Mg 2+ , K + , Ca 2+ The ion concentration decreased to 4.1mg / L, 0.5mg / L, 0.9mg / L, and 4.3mg / L corresponding to Na + Mg 2+ , K + , Ca 2+ The ion removal rates were 99.08%, 97.64%, 96.91% and 96.36% respectively, proving that pulp and papermaking wastewater sludge has great application potential in the treatment and purification of papermaking wastewater by preparing carbonized products and photothermal conversion membranes. Fig. 9 shown.

[0109] In summary, pulp and paper wastewater sludge has great application potential in the field of photothermal treatment, especially in the field of thermal interface water treatment.

[0110] This work was funded and supported by the National Key R&D Program of China (No. 2023YFC3207005).

[0111] The embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the purpose of the present invention. In addition, the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

Claims

1. An application of pulp and papermaking wastewater sludge in the field of photothermal energy.

2. The use according to claim 1, characterized in that: The pulping and papermaking wastewater sludge has a moisture content of 50-80%, a lignin content of 5-30%, a crude fiber content of 10-20%, an organic matter content of 40-80%, and a carbon element content of 15-50%.

3. The use according to claim 1 or 2, characterized in that The application includes sequentially carbonizing the pulp and papermaking wastewater sludge, preparing a photothermal conversion device, and using the photothermal conversion device.

4. The use according to claim 3, characterized in that: The carbonization of pulping and papermaking wastewater sludge comprises the following steps: S1: dewatering and crushing the pulping and papermaking wastewater sludge; S2: The product obtained from high temperature carbonization step S1.

5. The use according to claim 4, characterized in that: In step S2, the temperature of the high temperature carbonization is 400-700°C; preferably, in step S2, the atmosphere of the high temperature carbonization is argon or nitrogen; preferably, the flow rate of the atmosphere is 20-80 mL·min -1 .

6. The use according to claim 3, characterized in that: The light-to-heat conversion device includes a light-to-heat conversion film or a light-to-heat converter including the light-to-heat conversion film.

7. The use according to claim 6, characterized in that: The light-to-heat conversion film comprises a base film and a coating layer provided on the surface of the base film; the raw material for preparing the coating layer comprises the carbonized product of the pulping and papermaking wastewater sludge; Preferably, the preparation process of the light-to-heat conversion film comprises slurrying the carbonization product and the binder in a dispersant, and compounding the obtained slurry on the base film.

8. The use according to claim 7, characterized in that: In the slurry, the mass ratio of the carbonized product, the binder and the dispersant is 10:(0.01-0.8):(100-500).

9. The use according to claim 7, characterized in that: The binder is polyvinylidene fluoride and / or polyvinyl pyrrolidone.

10. The use according to claim 1 or 2, characterized in that: The photothermal field includes photothermal seawater desalination or photothermal wastewater purification.

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