New applications of paper sludge-based incineration ash

Abstract

The application discloses a new application of papermaking sludge-based incineration ash, and combines the papermaking sludge-based incineration ash and a persulfate salt to degrade terramycin in wastewater, and the degradation efficiency of the terramycin reaches 100% within 15 min, and the treated water body is in a near neutral state, so that the application provides a new use of the papermaking sludge-based incineration ash in actual industry, and improves the catalytic activity of removal of organic pollutants.

Description

Technical Field

[0001] This invention relates to a novel application of papermaking sludge-based incineration ash, and to the field of organic pollutant treatment technology. Background Technology

[0002] With the rapid development of industrial technology, various emerging organic pollutants (such as pharmaceuticals and personal care products (PPCPs), endocrine disruptors (EDCs), etc.) are widely used in various fields. However, due to the strong antibacterial activity and biological resistance of these organic pollutants, traditional biological wastewater treatment methods (such as physical treatment, biological treatment, and chemical treatment) are difficult to remove them. The advanced oxidation process (AOP) of persulfate (PS) has been proven to be an effective method for degrading organic pollutants because it can generate highly oxidizing free radicals (such as hydroxyl radicals, sulfate radicals, and superoxide radicals) that effectively degrade pollutants. However, unactivated persulfate has poor activity against most organic pollutants and requires activation through methods such as ultraviolet light, electrolysis, heating, ultrasound, transition metal ions, and metal oxidants. These methods require large energy inputs and complex synthesis processes, thus limiting their practical application in wastewater treatment. Therefore, developing a low-cost catalyst that does not require additional energy (light, electricity, heat, etc.) to achieve efficient activation of persulfate is urgent and necessary.

[0003] Paper mill sludge is a large-scale solid waste generated during the wastewater treatment process in paper mills, containing a large amount of inorganic substances (polyferric sulfate, polyaluminum sulfate, SiO2, etc.). Currently, the most common method for treating biological sludge in industry is incineration. However, this process generates a large amount of paper mill sludge ash, the disposal of which has become another major problem for researchers. Paper mill sludge-based incineration ash contains a large amount of calcium, which can effectively stabilize the environmental pH. Therefore, whether the components of paper mill sludge-based incineration ash can be effectively utilized to achieve efficient catalytic degradation has become a key issue that researchers need to focus on. In advanced oxidation processes based on persulfate, the problem of water acidification caused by the introduction of persulfate has not yet been effectively solved. Summary of the Invention

[0004] This invention provides a new application for papermaking sludge-based incineration ash, which is obtained by incinerating papermaking sludge under an oxygen-limited atmosphere. The obtained papermaking sludge-based incineration ash can become a highly active persulfate activator without any physical or chemical treatment, providing abundant active sites (octahedral Fe sites) for persulfate. At the same time, the water body treated with the papermaking sludge-based incineration ash will not be acidified.

[0005] This invention provides a new application for papermaking sludge-based incinerator ash, specifically for the degradation of oxytetracycline in wastewater. In the degradation experiment, papermaking sludge-based incinerator ash and persulfate were used in combination.

[0006] The preparation method of the papermaking sludge-based incineration ash specifically includes the following steps:

[0007] (1) The papermaking sludge is dried and ground into a uniform powder;

[0008] (2) Weigh the papermaking sludge dried in step (1) and incinerate it in an oxygen-limited atmosphere to obtain papermaking sludge-based incineration ash (pmSA).

[0009] Step (2) The volume fraction of oxygen in the oxygen-limited atmosphere is 10-30%.

[0010] The incineration temperature in step (2) is 600-1000℃, and the holding time is 0-10h.

[0011] The dosage of the papermaking sludge-based incineration ash is 0.05-0.4 g / L.

[0012] The persulfate is peroxymonosulfate (PMS) with a concentration of 0.005-0.05 g / L. Specifically, peroxymonosulfate (PMS) includes potassium peroxymonosulfate, sodium peroxymonosulfate, etc.

[0013] The papermaking sludge-based incineration ash obtained by this invention requires no physical or chemical treatment and can be directly used for the degradation of organic pollutants. The activated papermaking sludge-based incineration ash can be recycled multiple times.

[0014] When flocculants such as polyferric sulfate and polyaluminum ferric sulfate in papermaking sludge are incinerated in a limited O2 atmosphere, a phase transformation occurs at the temperature of this invention. Under the action of O2, Fe components such as Fe3O4 and Fe2O3 are generated, which can provide abundant Fe metal sites for activating persulfate without the need for an external iron source.

[0015] The papermaking sludge-based incinerator ash of this invention contains abundant Fe sites (such as octahedral Fe). 3+ Site, octahedral Fe 2+ Sites and tetrahedral Fe 3+ (site), in which octahedral Fe 3+ The site can effectively activate persulfate.

[0016] The papermaking sludge-based incineration ash obtained by this invention contains alkaline components such as CaO and CaCO3, which can effectively stabilize the pH value of the environment during the reaction and play a self-buffering role for acidic water bodies, preventing the water body from becoming acidified. This ensures that the persulfate-based process is always carried out under near-neutral conditions, thereby avoiding the problem of needing to perform secondary treatment of the purified water body. Attached Figure Description

[0017] Figure 1 The XRD pattern of the papermaking sludge-based incinerator ash of the present invention is shown.

[0018] Figure 2 This is a FITR diagram of the papermaking sludge-based incinerator ash of the present invention;

[0019] Figure 3 The change in wastewater pH during the degradation of oxytetracycline when the initial pH is 6. Detailed Implementation

[0020] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are all within the scope of protection of this invention.

[0021] The potassium persulfate used in the examples was purchased from RHAWN Reagents.

[0022] Example 1

[0023] A method for preparing papermaking sludge-based incineration ash specifically includes the following steps:

[0024] (1) The papermaking sludge is dried and ground into a uniform powder;

[0025] (2) Weigh the papermaking sludge dried in step (1) and incinerate it in an oxygen-limited atmosphere (the volume fraction of oxygen in the oxygen-limited atmosphere is 20%, and the remainder is nitrogen). The temperature is increased from room temperature to the corresponding temperature (600℃, 800℃, 1000℃) at a heating rate of 5℃ / min. The papermaking sludge-based incinerator ash prepared by holding the temperature at the three temperatures for 2 hours is labeled as pmSA-T, where T refers to the incineration temperature, i.e. pmSA600, pmSA800, and pmSA1000.

[0026] Comparative Example 1

[0027] A method for preparing papermaking sludge-based incineration carbon specifically includes the following steps:

[0028] (1) The papermaking sludge is dried and ground into a uniform powder;

[0029] (2) Weigh the papermaking sludge dried in step (1) and heat it from room temperature to the corresponding temperature (600℃) at a heating rate of 5℃ / min in a nitrogen atmosphere. Keep it at this temperature for 2 hours to prepare papermaking sludge-based incineration carbon, which is labeled as pmSC-T, where T refers to the incineration temperature, i.e. pmSC600.

[0030] Figure 1XRD patterns of papermaking sludge-based incineration ash and carbon obtained at different incineration temperatures are shown. Under aerobic conditions, CaO is more likely to combine with SO2 gas produced by the decomposition of organic matter in sludge to form CaSO4. Furthermore, the removal of organic matter is conducive to the formation of Fe3O4 crystals and the exposure of potential active crystal faces of Fe3O4 and α-Fe2O3. In addition, the pmSA800 and pmSA1000 materials obtained after increasing the temperature (800℃ and 1000℃) have similar crystallographic properties to pmSA600 obtained by low-temperature calcination. Compared to pmSC600, the peak intensities of Fe3O4 and α-Fe2O3 phases in pmSA (600, 800) are significantly increased, and are more prominent in pmSA800. Moreover, with increasing temperature, the amount of acid-resistant Ca2Al2SiO7 crystals formed by the combination of CaO species obtained from CaCO3 decomposition and Al species gradually increases. This change will reduce the formation of free calcium species in papermaking sludge-based incinerator ash during PMS activation, but will help suppress the dissolution of Al species. At 18.0° and 33.2°, the significant diffraction signals of pmSA800 are attributed to the Fe3O4 (111) and α-Fe2O3 (104) crystal planes, respectively, indicating that the increase in temperature causes the octahedral Fe in Fe3O4 to be affected. 2+ Migration occurs in the crystal lattice, forming a cation vacancy, leading to the formation of α-Fe2O3. When the temperature is further increased to 1000℃, the diffraction peaks of each crystal plane of the iron-containing crystal species do not change significantly, except for the peak intensity corresponding to the highly active Fe3O4 (311) crystal plane at 35.5°, which decreases significantly. Therefore, when flocculants such as polyferric sulfate and polyaluminum ferric sulfate in papermaking sludge are incinerated in a limited O2 atmosphere, a phase transformation will occur at the temperature of this invention, producing Fe3O4 and Fe2O3 under the action of O2. This can provide abundant Fe metal sites for activating persulfate, without the need for an external iron source. The incineration ash based on papermaking sludge contains abundant Fe sites (such as octahedral Fe). 3+ Site, octahedral Fe 2+ Sites and tetrahedral Fe 3+ (site), in which octahedral Fe 3+ The site can effectively activate persulfate.

[0031] Figure 2 The FITR plots of papermaking sludge-based incinerator ash obtained at different incineration temperatures are shown, with pmSA600 at 1430 cm⁻¹. -1 The presence of peaks indicates that the incineration ash based on papermaking sludge obtained under low-temperature aerobic conditions still contains a small amount of organic carbon. However, at this point, the incineration ash based on papermaking sludge exposes octahedral Fe atoms. t -O(454cm -1 ) and tetrahedral Fe t -O(566cm -1The presence of the functional groups (e.g., octahedral Fe) demonstrates that the presence of organic carbon does not affect the accessibility of PMS to active Fe species; the presence of these two functional groups further proves that active Fe species have multiple spatial occupancy sites (such as octahedral Fe) in papermaking sludge-based incinerator ash. 3+ Site, octahedral Fe 2+ Sites and tetrahedral Fe 3+ When the temperature was increased, the Fe-O tension peak in the obtained pmSA800 reached its maximum, indicating that pmSA800 has the most active Fe sites, which is consistent with the XRD analysis.

[0032] Paper sludge-based incineration ash contains abundant Fe sites (such as octahedral Fe). 3+ Site, octahedral Fe 2+ Sites and tetrahedral Fe 3+ (site), in which octahedral Fe 3+ The site can effectively activate persulfate, thereby efficiently degrading oxytetracycline.

[0033] Example 2

[0034] The papermaking sludge-based incineration ash obtained in Example 1 and the papermaking sludge-based incineration carbon obtained in Comparative Example 1 were directly degraded to degrade organic pollutants without any treatment. Specifically:

[0035] In 100 mL of 20 mg / L oxytetracycline (no pH adjustment required), papermaking sludge-based incineration ash and papermaking sludge-based incineration carbon were added at a dosage of 0.2 g / L, followed by 0.03 g / L of PMS (potassium peroxymonosulfate). The mixture was reacted under magnetic stirring for 30 min, and the degradation rate of oxytetracycline was measured at 15 min. The specific results are shown in Table 1.

[0036] Table 1. Degradation efficiency of oxytetracycline by incineration ash / carbon from papermaking sludge at different incineration temperatures.

[0037] catalyst Degradation rate of oxytetracycline / % pmSA600 (600℃ papermaking sludge-based incineration carbon) 82.91 pmSC600 (paper sludge-based incineration ash at 600℃) 95.3 pmSC800 (800℃ papermaking sludge-based incineration ash) 100.0 pmSC1000 (paper sludge-based incineration ash at 1000℃) 98.7

[0038] Table 1 shows that pmSA800 has the best degradation effect. Compared with papermaking sludge-based incineration carbon, papermaking sludge-based incineration ash has a better degradation effect on oxytetracycline.

[0039] Example 3

[0040] The effect of pH on degradation efficiency was investigated using the following steps:

[0041] Add 0.1M hydrochloric acid or 0.1M NaOH solution dropwise to 100mL of 20mg / L oxytetracycline to adjust the pH to 3-11. Then add 0.2g / L pmSA800, followed by 0.03g / L PMS (potassium persulfate). After reacting for 30min with magnetic stirring, oxytetracycline showed good catalytic effect within a pH range of 3-9. After the reaction, the pH of the water was 5.48-7.93. The specific results are shown in Table 2. When the initial pH of the water was 6, the pH change during the reaction was as follows: Figure 3 As shown.

[0042] Table 2. Degradation effect of oxytetracycline at different initial pH levels

[0043] initial pH value pH value after the reaction is completed Degradation rate of oxytetracycline / % 3 5.48 82.3 5 6.76 100 7 6.97 100 8 7.37 100 9 7.93 100 11 10.89 74.9

[0044] As shown in Table 2, the degradation rate of oxytetracycline can reach 100% when the initial pH value is 5-9.

[0045] Example 4

[0046] The effects of papermaking sludge-based incineration ash dosage and peroxymonosulfate (potassium peroxymonosulfate) on degradation efficiency were investigated. The specific steps are as follows:

[0047] Add 0.05-0.4 g / L of papermaking sludge-based incinerator ash to 100 mL of 20 mg / L oxytetracycline (no pH adjustment required), followed by 0.005-0.05 g / L of PMS (potassium peroxymonosulfate). React under magnetic stirring for 30 min, and then detect the degradation rate of oxytetracycline. The specific results are shown in Table 3.

[0048] Table 3. Degradation effect of oxytetracycline under different process parameters

[0049] Dosage of papermaking sludge-based incineration ash / g / L PMS concentration / g / L Degradation rate / % <![CDATA[Degradation rate / min -1 > 0.05 0.03 67.53 0.03963 0.1 0.03 87.06 0.10322 0.2 0.03 100 0.47845 0.4 0.03 100 0.73237 0.2 0.005 53.1 0.04773 0.2 0.01 86.57 0.20165 0.2 0.05 100 0.33962

[0050] As shown in Table 3, the degradation rate increases proportionally with the increase of the amount of papermaking sludge-based incinerator ash, reaching 100% after the amount is 0.2. Similarly, the degradation rate increases proportionally with the increase of the amount of PMS, reaching 100% after the amount is 0.2.

[0051] Example 5

[0052] The study on the effect of shielding agents on degradation efficiency follows the specific steps as follows:

[0053] Different shielding agents (sodium azide, isopropanol, p-benzoquinone, tetrahydrofurfuryl alcohol, and dimethyl sulfoxide) were added to 100 mL of 20 mg / L oxytetracycline (pH adjustment not required). Paper sludge-based incinerator ash was added at a dosage of 0.2 g / L, followed by 0.03 g / L of PMS (potassium peroxymonosulfate). The reaction was carried out under magnetic stirring for 30 min, and the main active species in the reaction were detected. The specific results are shown in Table 4.

[0054] Table 4 Inhibition rates of different shielding agents

[0055]

[0056]

[0057] As shown in Table 4, hydroxyl radicals, sulfate radicals, superoxide radicals, and singlet oxygen are not the main active species; high-valence iron is the main active species in this degradation reaction.

[0058] Example 6

[0059] The study on the impact of the number of recycling cycles of papermaking sludge-based incinerator ash on degradation efficiency is conducted through the following steps:

[0060] In 100 mL of 20 mg / L oxytetracycline (pH adjustment not required), papermaking sludge-based incinerator ash was added at a dosage of 0.2 g / L, followed by 0.03 g / L of PMS (potassium peroxymonosulfate). The mixture was reacted under magnetic stirring for 40 min, and the degradation rate of oxytetracycline was measured. After degradation was completed, without removing the catalyst, 10 mL of 200 mg / L oxytetracycline stock solution and 0.03 g / L of PMS (potassium peroxymonosulfate) were added directly. The experiment was repeated three times. The specific results are shown in Table 5.

[0061] Table 5 Degradation efficiency in cyclic experiments

[0062] Loop count Pollutant degradation rate / % 1 100 2 93.9 3 90.77 4 90.11

[0063] As can be seen from Table 5, the incineration ash based on papermaking sludge can be recycled, and the degradation effect is still significant after four recycling cycles.

[0064] By adjusting the volume fraction of oxygen in the oxygen-limited atmosphere in Example 1 to 10-30% and the heat preservation time of the incineration treatment to 0-10h, different papermaking sludge-based incineration ash can be obtained. Application experiments can yield similar conclusions to Examples 2-6.

[0065] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made to it in form and detail without departing from the scope defined by the claims of the present invention.

Claims

1. A new application of papermaking sludge-based incineration ash, which is combined with a persulfate salt to degrade terramycin in wastewater; The preparation method of the papermaking sludge-based incineration ash specifically comprises the following steps: (1) drying and grinding the papermaking sludge into uniform powder; (2) weighing the dried papermaking sludge in step (1) and performing incineration treatment in a limited oxygen atmosphere to obtain papermaking sludge-based incineration ash; the volume fraction of oxygen in the limited oxygen atmosphere is 10-30%; the temperature of the incineration treatment is 600-1000℃; wherein the polymeric ferric sulfate and polymeric aluminum ferric sulfate in the papermaking sludge produce Fe3O4 and Fe2O3 under the action of O2, and the papermaking sludge-based incineration ash contains CaO and CaCO3.

2. Use according to claim 1, characterized in that, The holding time of the incineration treatment in step (2) is 0-10h.

3. Use according to claim 1, characterized in that, The dosage of the papermaking sludge-based incineration ash is 0.05-0.4g / L.

4. The use according to claim 1, characterized in that, The persulfate salt is peroxymonosulfate, and the dosage thereof is 0.005-0.05g / L.

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