A method for separating and recycling discarded cigarette butts

Abstract

The present invention relates to a method for separating and recycling discarded cigarette butts, comprising the following steps: (1) removing tipping paper from the surface of collected cigarette butts to obtain pretreated cigarette butts; (2) adding the pretreated cigarette butts to an ethanol solution and soaking them to obtain a first soaking liquid and a first fiber segment; treating the first soaking liquid with acid to separate an aqueous phase, and alkalizing the aqueous phase to recover nicotine; (3) adding the first fiber segment to a non-polar solvent and soaking them to obtain a second soaking liquid and a second fiber segment; recovering a tar mixture through the second soaking liquid; and (4) recovering cellulose acetate using the second fiber segment as a raw material. The present invention can efficiently separate and recover nicotine, tar mixture, and cellulose acetate from cigarette butts, thereby achieving resource reuse, reducing environmental pollution, and lowering costs, and the method is simple.

Description

Technical Field

[0001] The invention relates to the field of cigarette butt recycling, and in particular to a method for separating and recycling discarded cigarette butts. Background Art

[0002] Discarded cigarette butts have become a ubiquitous form of solid waste in daily life. People typically consume only 4 / 5 to 2 / 3 of a cigarette, with the remaining 1 / 5 to 1 / 3 discarded as trash. The World Health Organization predicts that the number of smokers worldwide will exceed 1.7 billion by 2025, resulting in a massive amount of discarded cigarette butts and significant environmental pollution. However, limited research exists on separating and recycling the various substances in cigarette butts.

[0003] Cigarette filters are primarily made of acetate fiber, a material that is difficult to degrade naturally. Once discarded, toxic substances contained in discarded cigarette butts can accumulate in the environment over time, potentially contaminating the food chain and posing a threat to human health.

[0004] In 2008, Liu Dengfeng and his team used acetone and tetrahydrofuran as solvents to recover and prepare homogeneous cellulose acetate membranes of various concentrations. The following year, Min Zhao and others used a mixture of acetone and N,N-dimethylformamide to dissolve cellulose acetate, stirring it for 24 hours to produce an asymmetric membrane. These methods are complex and time-consuming, with low recovery rates. In 2017, Zhang Yanhui and others successfully recovered cellulose acetate using acetic acid as a solvent, achieving a high recovery rate. However, the soaking time was long, temperature control was required, and other substances in the cigarette butts were not recovered. Summary of the Invention

[0005] The purpose of the present invention is to overcome the above technical deficiencies and provide a method for separating and recycling discarded cigarette butts to solve the technical problems in the prior art of incomplete recovery of components in cigarette butts or complex and harsh recovery conditions.

[0006] In order to achieve the above technical objectives, the technical solution provided by the present invention is:

[0007] In a first aspect, the present invention provides a method for separating and recycling discarded cigarette butts, comprising the following steps: (1) removing the tipping paper on the surface of collected cigarette butts to obtain pretreated cigarette butts; (2) adding the pretreated cigarette butts to an ethanol solution, and soaking them to obtain a first soaking liquid and a first fiber segment; the first soaking liquid is treated with acid to separate the aqueous phase, and the aqueous phase is alkalized to recover nicotine; (3) adding the first fiber segment to a non-polar solvent, and soaking them to obtain a second soaking liquid and a second fiber segment; recovering a tar mixture through the second soaking liquid; and (4) recovering acetate fiber using the second fiber segment as a raw material.

[0008] In a second aspect, the present invention provides a method for separating and recycling discarded cigarette butts, comprising the following steps: (1) removing the tipping paper on the surface of the collected cigarette butts to obtain pretreated cigarette butts; (2) adding the pretreated cigarette butts to a non-polar solvent, and obtaining a first soaking liquid and a first fiber segment through soaking treatment; recovering the tar mixture through the first soaking liquid; (3) adding the first fiber segment to an ethanol solution, and obtaining a second soaking liquid and a second fiber segment through soaking treatment; separating the aqueous phase from the second soaking liquid after acid treatment, and alkalizing the aqueous phase to recover nicotine; and (4) recovering acetate fiber using the second fiber segment as raw material.

[0009] Compared with the prior art, the present invention has the following beneficial effects:

[0010] The present invention collects discarded cigarette butts and pre-treats them, then soaks them in an ethanol solution and a non-polar solvent to respectively recover nicotine and a tar mixture, and the process sequence of the two processes is adjustable. Finally, acetate fiber is recovered to ensure its structural morphology and a high recovery rate. Therefore, the present invention can efficiently separate and recover nicotine, tar mixture and acetate fiber in cigarette butts, realize resource recycling, reduce environmental pollution, lower costs, and the method is simple. DETAILED DESCRIPTION

[0011] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0012] The existing technology has defects such as complex methods for recycling cigarette butts, long processing time, high temperature and other harsh conditions, incomplete recovery of components in cigarette butts, insufficient utilization of waste solution, and damage to the acetate fiber structure. To address the above defects, the present invention provides a method for separating and recycling discarded cigarette butts, which can separate the main substances in discarded cigarette butts.

[0013] In a first aspect, the present invention provides a method for separating and recycling discarded cigarette butts, comprising the following steps:

[0014] (1) removing the tipping paper on the surface of the collected cigarette butts to obtain pre-treated cigarette butts; the pre-treated cigarette butts include filter tips or filter tips and tobacco;

[0015] (2) adding the pretreated cigarette butts into an ethanol solution and soaking them to obtain a first soaking liquid and a first fiber segment; the first soaking liquid is treated with acid to separate the aqueous phase, and the aqueous phase is alkalized to recover nicotine;

[0016] (3) adding the first fiber segment into a non-polar solvent and soaking the solvent to obtain a second soaking liquid and a second fiber segment; recovering the tar mixture through the second soaking liquid;

[0017] (4) Recovering cellulose acetate using the second fiber segment as raw material.

[0018] Preferably, in step (2), the volume fraction of the ethanol solution is 60% to 80%, the mass volume ratio of the pretreated cigarette butts to the ethanol solution is 1 g: (30 to 50) mL; and the immersion time is 0.5 to 1.5 h.

[0019] Preferably, in step (2), the acid treatment is performed by adding an equal volume of 1-2 mol / L hydrochloric acid to the first soaking solution, stirring the solution at room temperature and then allowing the solution to stand for phase separation.

[0020] Preferably, in step (2), the alkalization treatment is performed by adding or dripping an alkali solution accounting for 20% to 50% of the volume of the aqueous phase to the separated aqueous phase in portions to obtain a nicotine salt solution; the alkali solution comprises a sodium hydroxide (NaOH) or potassium hydroxide (KOH) solution having a concentration of 0.5 to 1.5 mol / L. After alkalization, the nicotine salt can be recovered and used in applications such as cleaning and pharmaceutical preparations. Furthermore, by adding the nicotine salt in portions or dripping it, excessive local concentration caused by a single addition can be avoided.

[0021] Preferably, in step (3), the non-polar solvent is a 3-4 mol / L n-heptane ethanol solution, and the soaking time is 1.5-2.0 hours. According to the principle of like dissolves like, tar (polycyclic aromatic hydrocarbons, hydrocarbons, etc.) in cigarette butts can be well dissolved in non-polar n-heptane. After adding n-heptane solution to react with the fiber segment at room temperature, the recovered second soaking liquid can be used as fuel, which contains substances such as tar, solanesol and triacetin, and the tar can be used for combustion. In the soaking treatment of step (3), if the soaking time is too long, the tar mixture will partially volatilize or decompose; if the time is too short, the dissolution will be insufficient, and the soaking efficiency will be reduced.

[0022] Preferably, the mass-to-volume ratio of the pretreated cigarette butts in step (2) to the non-polar solvent in step (3) is 1 g: (30-50) mL. In the soaking treatment in step (3), if the amount of non-polar solvent used is too small, the tar separation rate will decrease (below 70%). As the amount of non-polar solvent used increases, the separation rate gradually increases. After 40 mL, the separation rate is maintained at 80% to 90%. Therefore, the present invention preferably uses a mass-to-volume ratio of 1 g: (30-50) mL, and more preferably 1 g: 40 mL, to efficiently separate the tar mixture while saving costs.

[0023] Preferably, in step (4), the recovery of cellulose acetate using the second fiber segment as raw material specifically includes:

[0024] placing the second fiber segment into an organic solvent A, and adding a viscosity reducer accounting for 0 to 0.04% of the total mass of the second fiber segment and the organic solvent A to dissolve the cellulose acetate to obtain a cellulose acetate solution;

[0025] The acetate fiber solution, distilled water and flocculant are mixed, allowed to stand and then filtered to recover the acetate fiber.

[0026] Further preferably, the mass volume ratio of the pretreated cigarette butts and the organic solvent A in step (2) is 1 g: (40-60) mL.

[0027] Further preferably, organic solvent A comprises a mixture of methyl acetate and acetone in a volume ratio of 3:7 or a mixture of glacial acetic acid and ethanol in a volume ratio of 1:1; the amount of viscosity reducer used is 0.03-0.04% of the total mass of the second fiber segment and organic solvent A; the viscosity reducer comprises oxalic acid. The present invention helps acetate fiber dissolve better by adding a certain amount of viscosity reducer. Experimental verification has shown that the use of a mixture of methyl acetate and acetone can more effectively interact with the polar groups in diacetate fiber, and helps to destroy the hydrogen bonds in diacetate fiber, promoting its dissolution, and has greater solubility than a mixture of acetic acid and ethanol. Therefore, methyl acetate can dissolve more acetate fiber, takes less time, and can recover more acetate fiber.

[0028] More preferably, after filtering and recovering the cellulose acetate, the filtrate is distilled and reused. The filtered mixed solution is distilled to increase the concentration of glacial acetic acid, and then returned to step (4) for repeated use to reduce costs.

[0029] More preferably, the acetate fiber is dissolved by stirring at a rotation speed of 100 to 300 r / min for 2 to 3 minutes.

[0030] More preferably, the volume ratio of the acetate fiber solution to distilled water is 1:(2-4).

[0031] More preferably, the amount of flocculant used is 0.3-0.5% of the total mass of the cellulose acetate solution and distilled water. The flocculant includes CPAM (cationic polyacrylamide) or alum. The addition of the flocculant promotes aggregation of cellulose acetate in the solution, forming larger flocs that facilitate recovery and increase sedimentation velocity.

[0032] More preferably, the standing time is 20 to 40 minutes.

[0033] In a second aspect, the present invention provides a method for separating and recycling discarded cigarette butts, comprising the following steps:

[0034] (1) removing the tipping paper on the surface of the collected cigarette butts to obtain pretreated cigarette butts;

[0035] (2) adding the pretreated cigarette butts into a non-polar solvent, and soaking them to obtain a first soaking liquid and a first fiber segment; recovering the tar mixture through the first soaking liquid;

[0036] (3) adding the first fiber segment into an ethanol solution and soaking the solution to obtain a second soaking solution and a second fiber segment; treating the second soaking solution with an acid to separate the aqueous phase, and alkalizing the aqueous phase to recover nicotine;

[0037] (4) Recovering cellulose acetate using the second fiber segment as raw material.

[0038] That is, the steps of recovering nicotine and recovering the tar mixture in the present invention can be reversed in order, but the process of recovering nicotine first and then recovering the tar mixture in the first aspect is more preferred.

[0039] The main mechanism of action and advantages of the present invention are:

[0040] (1) Separate various substances in cigarette butts. This method can recycle the effective components in cigarette butts, realize resource reuse, and reduce environmental pollution.

[0041] (2) The present invention has simple operation steps and, compared with existing patents, lower temperature requirements, shorter processing time, and higher recovery rates. Tests have shown that a 3.5 mol / L n-heptane solution can separate 80%-90% of the tar mixture in cigarette butts, while maintaining the intact structure of the cellulose acetate.

[0042] (3) The solution can be reused. Cigarette tar is a product of incomplete combustion of cigarette butts. It is an extremely complex mixture of numerous hydrocarbons and hydrocarbon oxides, sulfides, and nitrides, including benzopyrene, cadmium, arsenic, β-naphthalene, amines, nitrosamines, etc. Among them, polycyclic aromatic hydrocarbons can be dissolved in n-heptane. n-heptane is an extremely stable hydrocarbon compound with strong solubility and can dissolve polycyclic aromatic hydrocarbons. In addition, n-heptane has a high calorific value and is widely used in the combustion field. Therefore, the soaking liquid can be considered as a fuel.

[0043] (4) Compared with the existing invention of using n-hexane solution to extract tar mixture, n-heptane extraction has higher efficiency and will not produce the "embrittlement" phenomenon (the phenomenon of polymer and highly filled composite materials becoming brittle, hardening, and losing elasticity). The structure of acetate fiber is well maintained, which is convenient for the subsequent recovery of acetate fiber.

[0044] (5) The present invention uses a mixture of methyl acetate and acetone to recover acetate fiber, which takes less time and can recover more acetate fiber; and a certain amount of viscosity reducer is added. Viscosity that is too high or too low is not conducive to industrial production. If the viscosity is too high, it will affect the dissolution efficiency, increase the burden on the equipment, and increase the equipment failure rate. Adding a viscosity reducer facilitates industrial production.

[0045] The present invention is further described in detail below through specific examples.

[0046] Example 1

[0047] A method for separating various substances from discarded cigarette butts comprises the following steps:

[0048] (1) Cigarette butt pretreatment: Collect cigarette butts and tear off the tipping paper on the surface of the cigarette butts to obtain pretreated cigarette butts.

[0049] (2) Recovering nicotine: Take 1 g of pretreated cigarette butts and soak them in 40 mL of 80% ethanol solution for 1 hour to separate the first soaking liquid and the first fiber segment. Add an equal volume of 2 mol / L hydrochloric acid to the first soaking liquid, stir evenly, and let it stand for phase separation. Then separate the aqueous phase and alkalize the aqueous phase by adding 1 mol / L sodium hydroxide solution at 30% of the volume of the aqueous phase in batches. Nicotine salt can be recovered and can be used in applications such as cleaning and pharmaceutical preparations.

[0050] (3) Recovering the tar mixture: adding 40 mL of 3.5 mol / L n-heptane solution to the first fiber segment at room temperature and reacting for 2 h, separating the second soaking liquid and the second fiber segment, and recovering the second soaking liquid.

[0051] Calorific value testing of the second soaking liquid in accordance with GB / T 213-2008, "Determination of the Calorific Value of Coal," revealed a calorific value of approximately 15,000 kJ / kg. This is similar to the calorific value of wood and paper compared to common combustibles, and higher than that of coal, sulfur, hydrogen, and carbon monoxide. This solution can replace coal and other fuels in certain situations, with high combustion efficiency. It can also replace wood and paper in certain situations. This, to a certain extent, conserves the use of combustibles and reduces the emission of environmental pollutants.

[0052] (4) Recovery of cellulose acetate: Place the second fiber segment into a mixture of 50 mL of methyl acetate and acetone (3:7 by volume) at room temperature, and add a viscosity reducer (oxalic acid) accounting for 0.034% of the total mass of the second fiber segment and the mixture to help the cellulose acetate dissolve better in the solution. Use a constant speed stirrer with a power of 60 W and set the speed to 200 r / min, stir until it is completely dissolved (complete dissolution is required in 2 minutes), and obtain a cellulose acetate solution. Then pour the cellulose acetate solution into distilled water with a volume ratio of 1:3 between the cellulose acetate solution and the distilled water, and add a flocculant (CPAM) accounting for 0.4% of the total mass of the cellulose acetate solution and the distilled water to promote the aggregation of the cellulose acetate in the solution to form larger flocs. After standing for 30 minutes, filter and recover the cellulose acetate.

[0053] Because acetate fiber is an esterified derivative of cellulose obtained through an acetic acid reaction, some of the hydroxyl groups in the cellulose molecular structure are replaced by acetyl groups, making it impossible to directly quantify the specific content of acetate fiber. The present invention analyzes the changes in the acetyl content in the second fiber segment obtained in step (3) of Example 1 and the acetate fiber collected in step (4) as an effective indicator for evaluating and reflecting the acetate fiber content. The results are shown in Table 1 below.

[0054] Table 1 Changes in acetyl content of cellulose acetate collected in Example 1

[0055]

[0056] As can be seen from Table 1, after the treatment in step (4), the acetyl content increased by about 10% compared with that before the treatment in step (4), indicating that the present invention can collect more acetate fiber.

[0057] Example 2

[0058] Compared with Example 1, the only difference is that when recovering cellulose acetate in step (4), oxalic acid is not added, and 50 mL of a mixed solution of glacial acetic acid and ethanol in a volume ratio of 1:1 is used instead of the acetone and methyl acetate mixed solution, and stirring is carried out for 2 minutes. The other steps and conditions are the same as those in Example 1.

[0059] Example 3

[0060] Compared with Example 1, the only difference is that the viscosity reducer is removed when recovering cellulose acetate, and the other steps and conditions are the same as those in Example 1.

[0061] Example 4

[0062] Compared with Example 1, the only difference is that the order of step (2) and step (3) is swapped (i.e., the tar mixture is recovered first, and then the nicotine is recovered). The other steps and conditions are the same as those in Example 1.

[0063] The solubility and recovery rate (95% of the mass of the separated cellulose acetate divided by the dry weight of the pre-treated cigarette butts) of the cellulose acetate obtained in Examples 1-4 were statistically analyzed, and the results are shown in Table 2.

[0064] Table 2 Solubility and recovery of cellulose acetate obtained in Examples 1-4

[0065]

[0066] As shown in Table 2, Example 1 is the best. When the acetone ratio is relatively high, the solubility of cellulose acetate is significantly improved. In a mixture of 70% acetone and 30% methyl acetate, cellulose acetate is completely dissolved and the solution is uniform and transparent. In Example 3, the viscosity reducer is removed, and in Example 4, the order of recovering the tar mixture and recovering the nicotine is reversed, which has little effect on the solubility of cellulose acetate. However, both have a certain impact on the recovery rate of cellulose acetate, which reduces the recovery rate, and the actual dissolution time required for Example 4 is prolonged. In Example 2, after changing the solvent type and removing the viscosity reducer, the effect is reduced relative to that of Examples 1 and 3. This shows that the present invention uses a mixture of methyl acetate and acetone in combination with a viscosity reducer to improve the recovery rate of cellulose acetate and also has a certain promoting effect on the solubility of cellulose acetate.

[0067] Example 5

[0068] Compared with Example 1, the dosage of the flocculant was adjusted to 0, 0.3%, 0.5% and 0.8% respectively. Other steps and conditions were the same as those in Example 1.

[0069] The results showed that either not adding a flocculant (i.e., adding too little) or adding too much resulted in reduced treatment effectiveness. Adding too little prevented the effective polymerization of cellulose acetate in the water, resulting in reduced water clarity. Adding too much generated a large amount of colloid, making the solution turbid and opaque, and reducing treatment efficiency. Therefore, the preferred flocculant dosage in the present invention is 0.3-0.5%.

[0070] Comparative Example 1

[0071] Compared with Example 1, the n-heptane solution was replaced by the n-hexane solution of the same concentration, and the other steps and conditions were the same as those in Example 1.

[0072] The results showed that the efficiency of extracting tar mixture with n-hexane solution was low, and it affected the structure of acetate fiber and caused embrittlement.

[0073] Therefore, the method of the present invention is suitable for recycling cigarette butts, and can recycle as many substances as possible from discarded cigarette butts, and the waste liquid can be used for combustion or reused after treatment. The present invention can effectively solve the problems of high temperature conditions, long processing time, and low recovery efficiency in existing processes. The present invention requires less time and only requires room temperature to achieve a high extraction rate, fully utilizes the waste liquid, separates multiple substances from cigarette butts, reduces costs, and reduces pollution.

[0074] The specific embodiments of the present invention described above do not limit the scope of protection of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the scope of protection of the claims of the present invention.

Claims

1. A method for separating and recycling discarded cigarette butts, characterized in that: The following steps are involved: (1) removing the tipping paper on the surface of the collected cigarette butts to obtain pretreated cigarette butts; (2) adding the pretreated cigarette butts into an ethanol solution and soaking them to obtain a first soaking liquid and a first fiber segment; The first soaking liquid is treated with acid to separate the aqueous phase, and the aqueous phase is subjected to alkalization treatment to recover nicotine; (3) adding the first fiber segment into an n-heptane solution and soaking the solution to obtain a second soaking solution and a second fiber segment; recovering the tar mixture through the second soaking liquid; (4) Recovering cellulose acetate using the second fiber segment as a raw material, specifically comprising: placing the second fiber segment in an organic solvent A, and adding a viscosity reducer accounting for 0 to 0.04% of the total mass of the second fiber segment and the organic solvent A, dissolving the cellulose acetate to obtain a cellulose acetate solution; the organic solvent A is a mixture of methyl acetate and acetone or a mixture of glacial acetic acid and ethanol; The acetate fiber solution, distilled water and flocculant are mixed, allowed to stand and then filtered to recover the acetate fiber.

2. The method for separating and recycling discarded cigarette butts according to claim 1, characterized in that: In step (2), the volume fraction of the ethanol solution is 60% to 80%, the mass volume ratio of the pretreated cigarette butts to the ethanol solution is 1 g: (30 to 50) mL; the soaking time is 0.5 to 1.5 h; The acid treatment is performed by adding an equal volume of 1-2 mol / L hydrochloric acid to the first soaking solution.

3. The method for separating and recycling discarded cigarette butts according to claim 1, characterized in that: In step (3), the concentration of the n-heptane solution is 3-4 mol / L, and the soaking time is 1.5-2.0 h.

4. The method for separating and recycling discarded cigarette butts according to claim 1, characterized in that: The mass volume ratio of the pretreated cigarette butts in step (2) and the n-heptane solution in step (3) is 1 g: (30-50) mL.

5. The method for separating and recycling discarded cigarette butts according to claim 1, characterized in that: The mass-to-volume ratio of the pretreated cigarette butts to the organic solvent A is 1 g: (40-60) mL.

6. The method for separating and recycling discarded cigarette butts according to claim 1, characterized in that: The organic solvent A is a mixture of methyl acetate and acetone in a volume ratio of 3:7 or a mixture of glacial acetic acid and ethanol in a volume ratio of 1:1; The amount of the viscosity reducer is 0.03-0.04% of the total mass of the second fiber segment and the organic solvent A; The viscosity reducing agent includes oxalic acid.

7. The method for separating and recycling discarded cigarette butts according to claim 1, characterized in that: The cellulose acetate is dissolved by stirring at a speed of 100 to 300 r / min for 2 to 3 minutes; The volume ratio of the acetate fiber solution to the distilled water is 1:(2-4); The amount of the flocculant used is 0.3-0.5% of the total mass of the acetate fiber solution and the distilled water. The flocculant includes cationic polyacrylamide or alum.

8. The method for separating and recycling discarded cigarette butts according to claim 1, characterized in that: The standing time is 20 to 40 minutes.

9. A method for separating and recycling discarded cigarette butts, characterized in that: The following steps are involved: (1) removing the tipping paper on the surface of the collected cigarette butts to obtain pretreated cigarette butts; (2) adding the pretreated cigarette butts into an n-heptane solution and soaking them to obtain a first soaking liquid and a first fiber segment; recovering the tar mixture through the first soaking liquid; (3) adding the first fiber segment into an ethanol solution and soaking the solution to obtain a second soaking solution and a second fiber segment; treating the second soaking solution with an acid to separate the aqueous phase, and alkalizing the aqueous phase to recover nicotine; (4) Recovering cellulose acetate using the second fiber segment as a raw material, specifically comprising: placing the second fiber segment in an organic solvent A, and adding a viscosity reducer accounting for 0 to 0.04% of the total mass of the second fiber segment and the organic solvent A, dissolving the cellulose acetate to obtain a cellulose acetate solution; the organic solvent A is a mixture of methyl acetate and acetone or a mixture of glacial acetic acid and ethanol; The acetate fiber solution, distilled water and flocculant are mixed, allowed to stand and then filtered to recover the acetate fiber.