Waste cigarette end separation and recovery method

Abstract

The invention relates to a waste cigarette end separation and recovery method which comprises the following steps: (1) removing tipping paper on the surface of a collected cigarette end to obtain a pretreated cigarette end; (2) adding the pretreated cigarette end into an ethanol solution, and performing soaking treatment to obtain a first soaking solution and a first fiber section; performing acid treatment on the first soaking solution, separating a water phase, and performing alkalization treatment on the water phase to recover nicotine; (3) adding the first fiber section into a non-polar solvent, and performing soaking treatment to obtain a second soaking solution and a second fiber section; recovering a tar mixture through a second soaking solution; and (4) recycling cellulose acetate fibers by taking the second fiber section as a raw material. The method can efficiently separate and recover nicotine, a tar mixture and acetate fibers in the cigarette ends, realizes resource reutilization, reduces environmental pollution, reduces cost, and 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] In daily life, discarded cigarette butts have become a common solid waste. When people smoke, they usually only consume 4 / 5 to 2 / 3 of a cigarette, and the remaining 1 / 5 to 1 / 3 is thrown away as garbage. The World Health Organization pointed out that by 2025, the number of smokers in the world will rise to more than 1.7 billion, resulting in an extremely large number of discarded cigarette butts, causing considerable pollution to the environment. However, there are few studies on the separation and recycling of various substances in cigarette butts.

[0003] The main component of the filter part of cigarette butts is acetate fiber, which is difficult to degrade naturally. After cigarette butts are discarded, the toxic substances they contain may accumulate in the natural environment for a long time, causing potential pollution in the food chain and posing a certain threat to human health.

[0004] In 2008, Liu Dengfeng and his team used acetone and tetrahydrofuran as solvents to recover and prepare cellulose acetate homogeneous membranes of various concentrations. The following year, Min Zhao and others used a mixture of acetone and N,N-dimethylformamide to dissolve cellulose acetate and made an asymmetric membrane after stirring for 24 hours. 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 with a high recovery rate, but the soaking time was long and the temperature conditions needed to be controlled, 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 purpose, the technical solution provided by the present invention is: 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 the collected cigarette butts to obtain pretreated cigarette butts; (2) adding the pretreated cigarette butts into an ethanol solution, and obtaining a first soaking liquid and a first fiber segment through soaking treatment; separating an aqueous phase from the first soaking liquid through acid treatment, and alkalizing the aqueous phase to recover nicotine; (3) adding the first fiber segment into a non-polar solvent, and obtaining a second soaking liquid and a second fiber segment through soaking treatment; recovering a tar mixture through the second soaking liquid; and (4) recovering acetate fiber using the second fiber segment as raw material.

[0007] 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; (4) recovering acetate fiber using the second fiber segment as raw material.

[0008] Compared with the prior art, the beneficial effects of the present invention include: The present invention collects discarded cigarette butts and performs pretreatment, and then soaks them in an ethanol solution and a non-polar solvent to respectively realize nicotine recovery and tar mixture recovery, and the process sequence of the two is adjustable, and finally recovers acetate fiber to ensure its structural morphology and 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, reduce costs, and the method is simple. DETAILED DESCRIPTION

[0009] In order to make the purpose, technical solution 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 used to limit the present invention.

[0010] The existing technology has the disadvantages of 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, damage to the structure of cellulose acetate, etc. In view of the above defects, the present invention provides a method for separating and recycling waste cigarette butts, which can separate the main substances in waste cigarette butts.

[0011] 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 the collected cigarette butts to obtain pre-treated cigarette butts; the pre-treated cigarette butts include filter tips or filter tips and tobacco; (2) adding the pretreated cigarette butts into an ethanol solution to obtain a first soaking liquid and a first fiber segment through soaking treatment; separating the aqueous phase from the first soaking liquid through acid treatment, and alkalizing the aqueous phase to recover nicotine; (3) adding the first fiber segment into a non-polar solvent, and obtaining a second soaking liquid and a second fiber segment through soaking treatment; and recovering the tar mixture through the second soaking liquid; (4) Recovering acetate fiber using the second fiber segment as raw material.

[0012] 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.

[0013] 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 evenly at room temperature, and then standing to separate the phases.

[0014] Preferably, in step (2), the alkalization treatment conditions are: adding or dripping 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 includes a sodium hydroxide (NaOH) or potassium hydroxide (KOH) solution with a concentration of 0.5 to 1.5 mol / L. After alkalization, the nicotine salt can be recovered, and the nicotine salt can be used in applications such as cleaning and pharmaceutical preparations, and by adding or dripping in portions, the local concentration caused by adding all at once is avoided.

[0015] 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, it will cause partial volatilization or decomposition of the tar mixture; if the time is too short, it will lead to insufficient dissolution and the soaking efficiency will be reduced.

[0016] Preferably, the mass volume ratio of the pretreated cigarette butts in step (2) and the non-polar solvent in step (3) is 1 g: (30-50) mL. In the soaking treatment in step (3), if the amount of the non-polar solvent is too small, the tar separation rate will be reduced (below 70%). As the amount of the non-polar solvent increases, the separation rate gradually increases. After 40 mL, the separation is maintained at 80% to 90%. Therefore, the present invention preferably uses a mass volume ratio of the pretreated cigarette butts to the non-polar solvent of 1 g: (30-50) mL, more preferably 1 g: 40 mL, which can save costs while efficiently separating the tar mixture.

[0017] Preferably, in step (4), the recovery of acetate fiber using the second fiber segment as raw material specifically includes: The second fiber segment is placed in an organic solvent A, and a viscosity reducer accounting for 0 to 0.04% of the total mass of the second fiber segment and the organic solvent A is added to dissolve the acetate fiber to obtain an acetate fiber solution; The acetate fiber solution, distilled water and flocculant are mixed, allowed to stand, and then filtered to recover the acetate fiber.

[0018] 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.

[0019] Further preferably, the 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 the viscosity reducer is 0.03-0.04% of the total mass of the second fiber segment and the organic solvent A; the viscosity reducer comprises oxalic acid. The present invention helps the acetate fiber to dissolve better by adding a certain amount of viscosity reducer. And it has been verified by experiments that the use of a mixture of methyl acetate and acetone can more effectively interact with the polar groups in the diacetate fiber, and helps to destroy the hydrogen bonds in the diacetate fiber, promote its dissolution, and has a greater solubility than the mixture of acetic acid and ethanol. Therefore, methyl acetate can dissolve more acetate fiber, take less time, and can recover more acetate fiber.

[0020] More preferably, after filtering and recovering the acetate fiber, the filtrate obtained 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.

[0021] More preferably, the acetate fiber is dissolved by stirring at a rotation speed of 100 to 300 r / min for 2 to 3 minutes.

[0022] More preferably, the volume ratio of the acetate fiber solution to distilled water is 1:(2-4).

[0023] Further preferably, the amount of flocculant used is 0.3-0.5% of the total mass of the acetate fiber solution and distilled water, and the flocculant includes CPAM (cationic polyacrylamide) or alum. The present invention promotes the aggregation of acetate fiber in the solution to form larger flocs, which is convenient for recovery and increases the sedimentation rate by adding flocculants.

[0024] More preferably, the standing time is 20 to 40 minutes.

[0025] 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 into a non-polar solvent, and obtaining a first soaking liquid and a first fiber segment through soaking treatment; and 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 liquid and a second fiber segment; treating the second soaking liquid with an acid to separate an aqueous phase, and alkalizing the aqueous phase to recover nicotine; (4) Recovering acetate fiber using the second fiber segment as raw material.

[0026] 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 first recovering nicotine and then recovering the tar mixture is more preferred.

[0027] The main mechanism of action and advantages of the present invention are: (1) Separating various substances in cigarette butts. This method can be used to recycle the effective components in cigarette butts, realize resource recycling, and reduce environmental pollution.

[0028] (2) The present invention has simple operation steps and, compared with the existing patents, has lower temperature requirements, shorter time and higher recovery rate. According to tests, 3.5 mol / L n-heptane solution can separate 80%-90% of the tar mixture in cigarette butts, and the structure of acetate fiber remains intact.

[0029] (3) The solution can be reused. Cigarette tar is the product of incomplete combustion of cigarette butts. It is an extremely complex mixture of many hydrocarbons and hydrocarbon oxides, sulfides and nitrides, including benzopyrene, cadmium, arsenic, β-naphthalene, amines, nitrosamines, etc., among which 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 field of combustion. Therefore, the soaking liquid can be considered as a fuel.

[0030] (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 that polymers and highly filled composite materials become brittle, harden, and lose elasticity). The structure of acetate fiber is well maintained, which is convenient for the subsequent recovery of acetate fiber.

[0031] (5) The present invention uses a mixed solution 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, wherein too high or too low viscosity 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.

[0032] The present invention is further described in detail below through specific examples.

[0033] Example 1 A method for separating various substances in discarded cigarette butts comprises the following steps: (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.

[0034] (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 stand to separate the phases. Then separate the aqueous phase and alkalize the aqueous phase by adding 1 mol / L sodium hydroxide solution in portions, which accounts for 30% of the volume of the aqueous phase. Nicotine salt can be recovered and can be used in applications such as cleaning and pharmaceutical preparations.

[0035] (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.

[0036] According to GB / T 213-2008 "Method for Determining Calorific Value of Coal", the calorific value of the second soaking liquid was tested, and the calorific value of the second soaking liquid reached about 15000kJ / kg, which is similar to the calorific value of wood and paper compared with the calorific value of common combustion materials, and higher than the calorific value of coal, sulfur, hydrogen, and carbon monoxide. This solution can replace coal and other fuels for combustion in some occasions, and the combustion efficiency is high. It can also replace wood, paper, etc. for combustion in specific occasions. To a certain extent, the use of combustion materials is saved and the emission of environmental pollutants is reduced.

[0037] (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 60W constant speed stirrer, set the speed to 200r / min, and stir until it is completely dissolved (2 minutes to completely dissolve), to obtain a cellulose acetate solution. Then pour the cellulose acetate solution into distilled water, the volume ratio of the cellulose acetate solution to the distilled water is 1:3, 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 cellulose acetate in the solution to form larger flocs. After standing for 30 minutes, filter and recover the cellulose acetate.

[0038] Since acetate fiber is an esterified derivative of cellulose obtained through acetic acid reaction, part of the hydroxyl groups in the cellulose molecular structure are replaced by acetyl groups, which makes it impossible to directly quantify the specific content of acetate fiber. The present invention analyzes the change of 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 content of acetate fiber. The results are shown in Table 1 below.

[0039] Table 1 Changes in the acetyl content of cellulose acetate collected in Example 1

[0040] 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 fibers.

[0041] Example 2 Compared with Example 1, the only difference is that when recovering acetate fiber 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 stirred for 2 minutes. The other steps and conditions are the same as in Example 1.

[0042] Example 3 Compared with Example 1, the only difference is that when recovering acetate fiber, the viscosity reducer is removed, and the other steps and conditions are the same as those in Example 1.

[0043] Example 4 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.

[0044] 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 the above Examples 1-4 were statistically analyzed, and the results are shown in Table 2.

[0045] Table 2 Solubility and recovery rate of acetate fiber obtained in Examples 1-4

[0046] From the results in Table 2, it can be seen that Example 1 is the best. When the proportion of acetone 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; Example 3 removes the viscosity reducer, and Example 4 exchanges the order of recovering the tar mixture and recovering nicotine, which has little effect on the solubility of cellulose acetate, but both have a certain effect on the recovery rate of cellulose acetate, the recovery rate is reduced, and the actual dissolution time required for Example 4 is prolonged; in Example 2, the solvent type is changed, and after the viscosity reducer is removed, the effect is reduced relative to that of Example 1 and Example 3, indicating that the present invention uses a mixture of methyl acetate and acetone 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.

[0047] Example 5 Compared with Example 1, the dosage of the flocculant was adjusted to 0, 0.3%, 0.5% and 0.8% respectively, and the other steps and conditions were the same as those in Example 1.

[0048] The results show that not adding flocculants (i.e. adding too little) or adding too much will lead to a decrease in the treatment effect. Adding too little will cause the acetate fiber in the water to not be effectively polymerized, resulting in reduced water transparency. Adding too much will generate a large amount of colloids, making the solution turbid and opaque, and reducing the treatment efficiency. Therefore, the preferred amount of flocculants used in the present invention is 0.3-0.5%.

[0049] Comparative Example 1 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.

[0050] The results showed that the efficiency of extracting tar mixture with n-hexane solution was low and it affected the structure of acetate fiber, causing embrittlement.

[0051] Therefore, the method of the present invention is suitable for recycling cigarette butts, and can recycle as many substances as possible in 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 recycling efficiency in the existing process; the present invention requires less time, and can obtain a higher extraction rate at room temperature, and fully utilize the waste liquid, separate various substances in cigarette butts, reduce costs, and reduce pollution.

[0052] The specific implementation of the present invention described above does not constitute a limitation on the protection scope 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 protection scope 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 the nicotine; (3) adding the first fiber segment into a non-polar solvent to obtain a second soaking liquid and a second fiber segment through soaking treatment; and recovering the tar mixture through the second soaking liquid; (4) Recovering acetate fiber using the second fiber segment as raw material.

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 immersion time is 0.5 to 1.5 h; The acid treatment is to add 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 non-polar solvent is a 3-4 mol / L n-heptane solution, 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 non-polar solvent 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: In step (4), the recovery of acetate fiber using the second fiber segment as raw material specifically includes: The second fiber segment is placed in an organic solvent A, and a viscosity reducer accounting for 0 to 0.04% of the total mass of the second fiber segment and the organic solvent A is added to dissolve the acetate fiber to obtain an acetate fiber solution; The acetate fiber solution, distilled water and flocculant are mixed, allowed to stand, and then filtered to recover the acetate fiber.

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

7. The method for separating and recycling discarded cigarette butts according to claim 5, 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 reducing agent 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.

8. The method for separating and recycling discarded cigarette butts according to claim 5, characterized in that: The acetate fiber dissolving is carried out by stirring at a speed of 100 to 300 r / min for 2 to 3 minutes; The volume ratio of the acetate fiber dissolving 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, and the flocculant includes cationic polyacrylamide or alum.

9. The method for separating and recycling discarded cigarette butts according to claim 5, characterized in that: The standing time is 20 to 40 minutes.

10. 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 a non-polar solvent, and obtaining a first soaking liquid and a first fiber segment through soaking treatment; and 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 liquid and a second fiber segment; treating the second soaking liquid with an acid to separate an aqueous phase, and alkalizing the aqueous phase to recover nicotine; (4) Recovering acetate fiber using the second fiber segment as raw material.

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