Preparation method and application of solid waste-based hydrothermal carbon adsorbent

Abstract

The invention belongs to the technical fields of environmental engineering and solid waste resource utilization, and particularly relates to a preparation method and application of a solid waste-based hydrothermal carbon adsorbent. The preparation method specifically comprises the following steps: adding a sodium carbonate solution to filtered zinc chloride wastewater, stirring and filtering to obtain zinc carbonate particles, and dissolving the zinc carbonate particles in a hydrochloric acid solution to obtain a zinc chloride activator; weighing dried sludge particles and waste PVC plastic particles, placing them in a reactor for a co-hydrothermal carbonization reaction to obtain initial hydrothermal carbon, placing the initial hydrothermal carbon in the zinc chloride activator for immersion, then taking out the immersed initial hydrothermal carbon and performing a high-temperature activation treatment to obtain modified hydrothermal carbon, immersing the modified hydrothermal carbon in hydrochloric acid to remove impurities in the modified hydrothermal carbon, then washing the modified hydrothermal carbon with clean water to remove the hydrochloric acid solution on the surface of the modified hydrothermal carbon, and finally drying and pulverizing the washed modified hydrothermal carbon to obtain the solid waste-based hydrothermal carbon adsorbent.

Description

Technical Field

[0001] The present invention belongs to the technical field of environmental engineering and solid waste resource utilization, and particularly relates to a preparation method and application of a solid waste-based hydrothermal carbon adsorbent. Background Art

[0002] The production of zinc chloride is often accompanied by the generation of large quantities of zinc chloride wastewater. Direct discharge of zinc chloride wastewater poses serious environmental risks, posing a significant challenge to the industry in reducing, recycling, and rendering it harmless. Zinc chloride dehydrates and erodes adsorbent raw materials and has been widely used to activate and modify biochar adsorbents. Numerous studies have demonstrated that zinc chloride-modified biochar adsorbents exhibit enhanced pore structure and adsorption performance.

[0003] my country's sewage treatment plants currently produce a massive amount of dewatered sludge. This sludge contains not only a large amount of organic pollutants but also toxic and hazardous contaminants such as heavy metals, pathogens, and polycyclic aromatic hydrocarbons. If not properly treated and disposed of, it can easily cause secondary environmental pollution. Current sludge treatment and disposal methods primarily include landfilling, incineration, and land utilization. However, these methods also present a range of other issues, such as the waste of land resources associated with direct landfilling and the dust pollution caused by incineration.

[0004] Hydrothermal carbonization (HTC) is a novel thermochemical treatment method for treating high-moisture solid wastes, such as sludge, without the need for energy-intensive pre-drying. Instead, HTC converts the sludge's moisture into hot, compressed water, which serves as the reaction medium. Under high-temperature conditions, HTC improves sludge dewatering performance and produces biochar with a highly aromatic and mesoporous structure, offering broad opportunities for the resourceful utilization of sludge.

[0005] Studies have found that hydrothermal carbonization has a good dechlorination effect on PVC. In the hydrothermal carbonization of PVC, the organic chlorine in PVC can be effectively converted into inorganic chlorine through the hydrothermal carbonization process in subcritical water. Therefore, HTC is a feasible method for harmless treatment of PVC. In addition, the biomass (cellulose, lignin and xylan) reported in previous studies has a synergistic effect on the dechlorination efficiency of PVC during the hydrothermal carbonization process. In the hydrolysis and dechlorination reaction of PVC, biomass can provide a large number of free -OH bonds. It can strengthen the substitution of -Cl and -OH, enhancing the intensity of the dechlorination reaction. The released chlorine then dissolves in the aqueous phase to form HCl and trace cyclic compounds.

[0006] Prior art: "A Comprehensive Recovery Method for Zinc Chloride-Containing Solution" is a patent applied for by Guizhou Xing'an Environmental Protection Technology Co., Ltd. on December 11, 2017. The patent application publication number is CN 108085498A, the authorization publication number is CN108085498 B, and the authorization publication date is May 14, 2019. This invention provides a comprehensive recovery method for zinc chloride solution, with a high zinc recovery rate. However, due to the complex process, high operational difficulty, and the large number of reagents required, its practical application is limited by cost and other factors.

[0007] Prior art: "A Method for Recovering Zinc Chloride from Zinc Chloride Wastewater and Treating Wastewater with Zero Discharge" is a patent applied for by Shandong Murui Environmental Industry Co., Ltd. on March 6, 2020. The patent application publication number is CN 111362482A, and the application publication date is July 3, 2020. This invention provides a solution for recovering zinc chloride from zinc chloride wastewater, achieving efficient zinc chloride recovery while achieving zero wastewater discharge. However, the process is cumbersome, and the strong acids and bases required are dangerous, lack safety guarantees, and have certain limitations.

[0008] Therefore, how to combine the wastewater after zinc chloride production with sludge and solid waste gas materials and effectively utilize them is an issue worth exploring. Summary of the Invention

[0009] In view of the shortcomings of the existing technology, the present invention proposes a planting method for white peony root, which removes weeds grown during the planting process of white peony root by combining weed control with manual weeding, reduces the use of pesticides, avoids environmental pollution caused by large-scale use of pesticides, and also increases the yield of white peony root.

[0010] The purpose of the present invention can be achieved through the following technical solutions:

[0011] A preparation method and application of a solid waste-based hydrothermal carbon adsorbent, characterized in that the method specifically comprises: adding sodium carbonate solution to filtered zinc chloride wastewater, then stirring and filtering to obtain zinc carbonate particles, dissolving the zinc carbonate particles in a hydrochloric acid solution to obtain a zinc chloride activator; weighing dried sludge particles and waste PVC plastic particles, placing them into a reactor for a co-hydrothermal carbonization reaction to obtain initial hydrothermal carbon, placing the initial hydrothermal carbon into the zinc chloride activator for immersion to achieve the purpose of chemical activation, then taking out the immersed initial hydrothermal carbon for high-temperature activation treatment to obtain modified hydrothermal carbon, placing the modified hydrothermal carbon in hydrochloric acid to remove impurities in the modified hydrothermal carbon, then using clean water to wash the modified hydrothermal carbon to remove the hydrochloric acid solution on the surface of the modified hydrothermal carbon, and finally drying and crushing the washed modified hydrothermal carbon to obtain the solid waste-based hydrothermal carbon adsorbent.

[0012] Among them, the mass ratio of waste PVC plastic particles to sludge particles is 1:4; the mass ratio of initial hydrothermal carbon to zinc chloride activator is 1:2.

[0013] Preferably, the zinc chloride wastewater comes from a zinc chloride production process and contains a large amount of zinc chloride and other impurities.

[0014] Preferably, the sludge is taken from a sewage treatment plant and has been dehydrated, and the sludge contains rich organic matter.

[0015] Preferably, the concentration of the sodium carbonate solution is 1 mol / L, the concentration of the hydrochloric acid solution is 1 mol / L, the volume ratio of the sodium carbonate solution to the zinc chloride wastewater is 1:10, and the volume ratio of the zinc carbonate particles to the hydrochloric acid solution is 1:2.

[0016] Preferably, the reaction temperature of the co-hydrothermal carbonization reaction is 260° C., and the reaction time is 4 h.

[0017] Preferably, the immersion temperature is 70° C. and the immersion time is 8 hours.

[0018] Preferably, the high-temperature activation treatment is specifically as follows: placing the initial hydrothermal charcoal into a muffle furnace at a temperature of 600° C. for 2 hours.

[0019] Preferably, the concentration of the hydrochloric acid solution used to soak the modified hydrothermal carbon is 1 mol / L.

[0020] Preferably, the solid waste-based hydrothermal carbon adsorbent is prepared by the solid waste-based hydrothermal carbon adsorbent preparation method.

[0021] Preferably, the solid waste-based hydrothermal carbon adsorbent can be used for adsorption of organic pollutants such as tetracycline and methylene blue, and is widely applicable to water environment remediation and sewage treatment.

[0022] Beneficial effects of the present invention:

[0023] (1) The raw materials used in the present invention are all wastes that are harmful to the environment and difficult to treat. While harmlessly treating zinc chloride wastewater, municipal sludge, and waste PVC plastics, zinc chloride-modified solid waste-based hydrothermal carbon with good adsorption effect can be obtained. Under certain adsorption conditions, the adsorption capacity for tetracycline can reach 200 mg / g. The present invention provides a new solution for the reduction, resource utilization, and harmless treatment of zinc chloride wastewater, municipal sludge, and waste PVC plastics.

[0024] (2) The solution provided by the present invention has the characteristics of simple operation, easy acquisition of raw materials, and controllable and mild process. The by-products in the process of recycling zinc chloride wastewater and preparing solid waste-based hydrothermal carbon are stable in nature and low in yield, and will not cause significant impact on the environment after simple treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present disclosure or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0026] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0027] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0028] The present invention is further described in detail below through specific embodiments:

[0029] Example 1

[0030] (1) Raw water treatment;

[0031] (2) Preparation of hydrothermal carbonization by co-hydrothermal carbonization of solid waste: Sludge and waste PVC plastics were taken, dried, ground, and stored. The waste PVC plastics and municipal sludge were co-hydrothermally carbonized in a high-pressure reactor at a mass ratio of 1:4. The hydrothermal carbonization temperature was set at 260 °C and the residence time was set at 4 h. After the reaction was completed, the solid product was filtered to obtain the initial hydrothermal carbon.

[0032] (3) Chemical activation;

[0033] (4) Secondary physical activation;

[0034] (5) Product collection;

[0035] (6) Product adsorption test: 0.05 g of modified hydrothermal carbon was weighed into a 50 mL stoppered conical flask containing 50 mL of tetracycline (TC) solution with an initial concentration of 300 mg / L. The conical flask was placed in a thermostatic oscillator and oscillated at 25°C and 180 rpm until adsorption equilibrium was reached. After adsorption, the mixture was filtered through a 0.45 μm aqueous filter membrane. The residual TC concentration was determined using a UV-visible spectrophotometer.

[0036] The adsorption amount Q was calculated using [Formula (1)].

[0037]

[0038] Where C0 and Ce represent the initial and equilibrium concentrations of TC, respectively (mg·L-1); V represents the volume of the solution (L); and W represents the amount of adsorbent added (g). The results are shown in Table 1.

[0039] Table 1 Tetracycline adsorption results of the embodiment and its parallel group

[0040] sample Adsorption capacity (mg / g) Example 202.61 Parallel group 1 203.54 Parallel Group 2 200.92

[0041] Example 2

[0042] (1) Raw water treatment;

[0043] (2) Preparation of hydrothermal carbonization by co-hydrothermal carbonization of solid waste: Sludge and waste PVC plastics were taken, dried, ground, and stored. The waste PVC plastics and municipal sludge were co-hydrothermally carbonized in a high-pressure reactor at a mass ratio of 1:4. The hydrothermal carbonization temperature was set at 260 °C and the residence time was set at 6 h. After the reaction was completed, the solid product was filtered to obtain the initial hydrothermal carbon.

[0044] (3) Chemical activation;

[0045] (4) Secondary physical activation;

[0046] (5) Product collection;

[0047] (6) Product adsorption test: Same as Example 1. The results are shown in Table 2.

[0048] Table 2 Tetracycline adsorption results of the embodiment and its parallel group

[0049] sample Adsorption capacity (mg / g) Example 192.32 Parallel group 1 187.90 Parallel Group 2 190.67

[0050] Example 3

[0051] (1) Raw water treatment:

[0052] (2) Preparation of hydrothermal carbonization of solid waste: Same as Example 1;

[0053] (3) Chemical activation;

[0054] (4) Secondary physical activation;

[0055] (5) Product collection;

[0056] (6) Product adsorption test: 0.05 g of the modified hydrothermal carbon was weighed into a 50 mL stoppered Erlenmeyer flask containing 50 mL of a tetracycline (TC) solution with an initial concentration of 300 mg / L. The pH of the solution was adjusted to 9, and the Erlenmeyer flask was placed in a constant temperature oscillator. Other conditions were the same as in Example 1. The results are shown in Table 3.

[0057] Table 3 Tetracycline adsorption results of the embodiment and its parallel group

[0058] sample Adsorption capacity (mg / g) Example 182.54 Parallel group 1 179.84 Parallel Group 2 180.52

[0059] Example 4

[0060] (1) Raw water treatment:

[0061] (2) Preparation of hydrothermal carbonization of solid waste: Same as Example 1;

[0062] (3) Chemical activation;

[0063] (4) Secondary physical activation;

[0064] (5) Product collection;

[0065] (6) Product adsorption test: 0.05 g of the modified hydrothermal carbon was weighed into a 50 mL stoppered conical flask containing 50 mL of a tetracycline (TC) solution with an initial concentration of 150 mg / L. The conical flask was placed in a constant temperature oscillator. Other conditions were the same as in Example 1. The results are shown in Table 4.

[0066] Table 4 Example and its parallel group on tetracycline adsorption results

[0067] sample Adsorption capacity (mg / g) Example 123.58 Parallel group 1 123.97 Parallel Group 2 122.60

[0068] Example 5

[0069] (1) Raw water treatment:

[0070] (2) Preparation of hydrothermal carbonization of solid waste: Same as Example 1;

[0071] (3) Chemical activation;

[0072] (4) Secondary physical activation;

[0073] (5) Product collection;

[0074] (6) Product adsorption test: 0.05 g of the modified hydrothermal carbon was weighed into a 50 mL stoppered Erlenmeyer flask containing 50 mL of a methylene blue (MB) solution with an initial concentration of 200 mg / L. The Erlenmeyer flask was placed in a constant temperature oscillator. Other conditions were the same as in Example 1. The results are shown in Table 5.

[0075] Table 5 Example and its parallel group adsorption results of methylene blue

[0076] sample Adsorption capacity (mg / g) Example 82.45 Parallel group 1 82.95 Parallel Group 2 81.77

[0077] Throughout this specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0078] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention, and such changes and modifications fall within the scope of the invention as claimed.

Claims

1. A method for preparing a solid waste-based hydrothermal carbon adsorbent, characterized in that: The method specifically comprises the following steps: adding sodium carbonate solution to filtered zinc chloride wastewater, stirring and filtering to obtain zinc carbonate particles, dissolving the zinc carbonate particles in a hydrochloric acid solution to obtain a zinc chloride activator; weighing dried sludge particles and waste PVC plastic particles, placing them in a reactor for a co-hydrothermal carbonization reaction to obtain initial hydrothermal carbon, immersing the initial hydrothermal carbon in the zinc chloride activator to perform a chemical activation process, taking out the immersed initial hydrothermal carbon and performing a high-temperature activation treatment to obtain modified hydrothermal carbon, immersing the modified hydrothermal carbon in hydrochloric acid to remove impurities in the modified hydrothermal carbon, washing the modified hydrothermal carbon with clean water to remove the hydrochloric acid solution on the surface of the modified hydrothermal carbon, and finally drying and pulverizing the washed modified hydrothermal carbon to obtain a solid waste-based hydrothermal carbon adsorbent; The mass ratio of waste PVC plastic particles to sludge particles is 1:4; the mass ratio of initial hydrothermal carbon to zinc chloride activator is 1:2; The reaction temperature of the co-hydrothermal carbonization reaction is 260°C and the reaction time is 4 hours; The high temperature activation treatment is specifically as follows: placing the initial hydrothermal carbon into a muffle furnace and placing it at a temperature of 600° C. for 2 hours.

2. The preparation method according to claim 1, wherein: Zinc chloride wastewater comes from the zinc chloride production process and contains a large amount of zinc chloride and other impurities.

3. The preparation method according to claim 1, wherein: The sludge is taken from dewatered sludge in a sewage treatment plant and contains rich organic matter.

4. The preparation method according to claim 1, wherein: The concentration of the sodium carbonate solution is 1 mol / L, and the concentration of the hydrochloric acid solution is 1 mol / L; the volume ratio of the sodium carbonate solution to the zinc chloride wastewater is 1:

10.

5. The preparation method according to claim 1, wherein: The immersion temperature was 70° C. and the immersion time was 8 hours.

6. The preparation method according to claim 1, wherein: The concentration of the hydrochloric acid solution used to soak the modified hydrothermal carbon was 1 mol / L.

7. A solid waste-based hydrothermal carbon adsorbent prepared by the preparation method according to any one of claims 1 to 6.

8. Use of a solid waste-based hydrothermal carbon adsorbent prepared by the preparation method of any one of claims 1 to 6 or a solid waste-based hydrothermal carbon adsorbent as claimed in claim 7 in the adsorption of tetracycline and methylene blue organic pollutants, which is widely applicable to water environment remediation and sewage treatment.

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