Biological method for rapidly degrading waste polypropylene masks by using tenebrio molitor larvae

Abstract

The invention provides a biological method for quickly and efficiently degrading a polypropylene mask by using tenebrio molitor larvae, which comprises the following step of: mixing a waste polypropylene mask and wheat bran according to a mass ratio of 1: 1 under the conditions that the temperature is 28 + / -1 DEG C and the humidity is 65 + / -5% to serve as feed for feeding the tenebrio molitor larvae. Results show that the waste polypropylene masks in the feed can be quickly eaten by the tenebrio molitor larvae and effectively mineralized, and the tenebrio molitor larvae do not have physiological abnormality. Therefore, the problem of environmental accumulation caused by difficulty in natural degradation of the polypropylene mask after use can be solved, the waste polypropylene mask product can be further subjected to pollution-free treatment, and meanwhile, the utilization value of the tenebrio molitor can be improved.

Description

Technical Field

[0001] The invention belongs to the technical field of waste plastic degradation, and specifically relates to a biological method for rapidly and efficiently degrading polypropylene masks by using yellow mealworm larvae. Background Art

[0002] The main part of disposable medical masks is made of polypropylene (PP) as raw material, and is generally composed of a spunbond layer, a meltblown layer, and a spunbond layer. The composite mask can effectively absorb dust particles and capture bacteria and virus droplets by using electrostatic electret technology. However, polypropylene masks have stable chemical properties and are extremely difficult to degrade in nature. It takes 400 to 500 years for a disposable medical mask to be completely degraded in nature, and the microplastics (MPs) produced in this process may change the microbial structure in the human lungs and gastrointestinal tract if inhaled or ingested, thereby causing harm to human health. In addition, discarded masks flowing into the ocean will harm marine life, cause safety problems for maritime transportation, and lead to a series of environmental pollution problems.

[0003] At present, there are many methods for treating discarded disposable medical masks. The mainstream treatment methods are mainly landfill, incineration, physical recycling and chemical recycling. The landfill method does not fundamentally solve the problem of plastic pollution and will also lead to soil pollution; the waste gas and waste residue generated during the incineration process will cause serious pollution to the atmospheric environment; physical recycling through pyrolysis or engineering building materials will have problems such as high energy consumption and low utilization rate; the chemical reagents required for chemical recycling are expensive, and the waste chemical waste generated cannot be properly disposed of, which will also lead to secondary pollution. In summary, the large-scale production of discarded masks has begun to become a very thorny problem. Due to the non-biodegradability of non-modified plastics, there is little research on their biodegradation. If biological methods can be used to treat plastics, it will have great environmental and ecological benefits.

[0004] A large number of studies have shown that mealworm larvae can feed on plastic for biodegradation. Feeding mealworms with discarded polypropylene masks can not only solve environmental pollution but also maximize the advantages of mealworms as resource-based insects. This is of great significance for controlling environmental pollution and realizing resource recycling. Summary of the invention

[0005] The present invention aims to solve the problem that polypropylene masks used in large quantities are difficult to degrade naturally after use, thus causing environmental accumulation, and provides a biological method for using mealworm larvae to quickly feed and degrade discarded polypropylene masks. Compared with traditional treatment methods, the method of the present invention is more environmentally friendly and can achieve the effect of resource recycling and "turning waste into treasure".

[0006] To achieve the above object, the present invention adopts the following technical solutions: A biological method for rapidly and efficiently degrading polypropylene masks using mealworm larvae comprises the following steps: 1) Feed preparation: Cut the discarded polypropylene masks into slices, sterilize them at high temperature, and place them at room temperature to fully air dry, then mix them with wheat bran as feed; 2) Cultivation of mealworms: The feed obtained in step 1) is evenly spread on the bottom of the mealworm larvae cultivation container, and then the mealworm larvae are added for cultivation.

[0007] Furthermore, the polypropylene purity of the discarded polypropylene mask in step 1) is ≥99.9%.

[0008] Furthermore, in step 1), the discarded polypropylene masks are cut into sheets with a size of 2 cm×3 cm.

[0009] Furthermore, in the feed obtained in step 1), the mass ratio of discarded polypropylene masks to wheat bran is 1:1.

[0010] Furthermore, in step 2), the density of the mealworm larvae in the culture container is 2-3 / cm 2 .

[0011] Furthermore, the amount of feed used in step 2) is one quarter of the total weight of the insect body.

[0012] Furthermore, the culture conditions in step 2) are: temperature of 28±1°C, humidity of 65±5%, and optical condition of a dark environment.

[0013] The beneficial effects of the present invention are: (1) The degradable biological mealworm used in the present invention is a common resource insect with high content of nutrients such as protein and fat in its body, and the larvae do not emit toxic and harmful substances in the process of feeding and biodegrading polypropylene masks. Therefore, the use of mealworm larvae to biologically treat waste polypropylene masks can not only play a role in controlling plastic pollution, but also make beneficial use of mealworms and obtain biomass such as protein from mealworms. The degraded insect feces produced can be used as crop fertilizer, so it is suitable for being widely used in the rapid biological treatment of "degradable plastics" under conventional environments.

[0014] (2) The method provided by the present invention enables the discarded polypropylene masks to be quickly eaten and effectively mineralized by the mealworm larvae. During the 30-day feeding period, the average feeding amount was 216.1±23.95 mg, and the various physiological indicators of the larvae were almost the same as those of the pure wheat bran group. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1These are stereomicroscope images of the intestines of the mealworm larvae in the pure wheat bran group (a) and the pure mask group (b) in the example after being raised for 30 days.

[0016] Figure 2 A comparison of the morphology of the feces discharged by the yellow mealworm larvae raised in the pure wheat bran group (a) and the pure mask group (b) in the embodiment; Figure 3 This is a FI-TR comparison of the excrement discharged by the mealworm larvae in the pure wheat bran group and the pure mask group, and the original wheat bran and original mask. Figure 4 This is a TGA analysis chart of the mealworm used in the present invention feeding on and degrading waste polypropylene mask plastic before and after the excrement is discharged; Figure 5 This is a comparison chart of the total weight of the mealworm larvae in each treatment group after being raised for 30 days in the example.

[0017] Figure 6 The figure is a comparison chart of the survival rate of mealworm larvae in each treatment group after being raised for 30 days in the embodiment.

[0018] Figure 7 The figure is a comparison chart of the pupation rates of the mealworm larvae in each treatment group after being raised for 30 days in the embodiment.

[0019] Figure 8 The figure is a comparison chart of the self-mutilation rate of mealworm larvae in each treatment group after being raised for 30 days in the embodiment.

[0020] Fig. 9 This is a comparison chart of the mask consumption of mealworm larvae in each treatment group after being raised for 30 days in the embodiment. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are 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 creative work are within the scope of protection of the present invention.

[0022] The discarded polypropylene masks used are disposable medical masks, and their polypropylene purity is ≥99.9%.

[0023] The breeding container used is a disposable plastic lunch box with a high degree of polymerization to prevent the mealworms from gnawing on it.

[0024] The wheat bran used does not contain any additives and has a moisture content of 14%. Example

[0025] This embodiment provides a biological method for quickly and efficiently degrading discarded polypropylene masks using mealworm larvae, comprising the following steps: 1) Preparation of mealworms: Select mealworm larvae of the same age and weight of 59.4±2.55 mg (and the mealworm larvae have not been given any type of antibiotics before the test) and place them at 2-3 / cm 2 The density of the insects is 20000 (to prevent self-harm caused by overcrowding) and they are placed in a culture container (the size of the container is 12.7cm long × 17.8cm wide × 10cm high), and pure wheat bran is added as feed at a quarter of the total weight of the insects. The insects are pre-cultured in a dark environment at a temperature of 28±1℃, a humidity of 65±5% for 14 days; 2) Preparation of feed: Pre-process the discarded polypropylene masks by slicing them into 2cm×3cm slices. After sterilizing them in a high-temperature sterilizer at 121℃ for 25min, place them at room temperature to fully air-dry and crush them to obtain the test material; 3) Experimental groups: starvation treatment group, pure wheat bran group, 20% mask group, 40% mask group, 50% mask group, 60% mask group, 80% mask group, and pure mask group were set up. Each treatment group had 4 biological replicates, and the corresponding feed was evenly spread on the bottom of the new breeding container according to the corresponding requirements (the feed amount was one-fourth of the total weight of the insect body); the mealworm larvae were starved for 48 hours before the test, and then transferred to the new breeding container, and cultured in a dark environment at a temperature of 28±1℃, a humidity of 65±5% (attention should be paid to changes in relevant parameters during the culture process), and the feed consumption was recorded every 5 days, and it was necessary to replenish the feed in time before it was consumed.

[0026] 1. The mealworm larvae from the pure wheat bran group and the pure mask group after 30 days of feeding were sampled and observed after pretreatment and dissection.

[0027] The specific operation process of pretreatment and dissection is as follows: soak the mealworm larvae in ethanol for 2 hours and then freeze-dry for 24 hours, so that the intestines of the mealworm larvae can be easily separated from other tissues. Then use a scalpel to remove the head from the second segment behind the head of the worm body, and use tweezers to take out the entire section of the intestine in the worm body, observe and take photos. The results are as follows Figure 1 shown.

[0028] Depend on Figure 1 By comparison, it can be observed that the shape of the intestines of the mealworm larvae fed with pure masks changed, and a small amount of ingested and not completely digested polypropylene mask material existed in the intestines.

[0029] 2. The collected insect feces of the pure wheat bran group and the pure mask group were observed and analyzed. The results are as follows: Figure 2 shown.

[0030] Depend on Figure 2It can be observed that there are obvious differences in the insect feces produced by mealworm larvae feeding on different feeds. The insect feces collected by the pure wheat bran group are regular in shape and distinct in particles; the insect feces of the pure mask group are fibrous and loose in shape under naked eye observation, and the remaining polypropylene fibers of the mask can be clearly seen (left picture). Further comparison of the morphological differences in the insect feces of larvae fed different feeds by scanning electron microscopy (SEM) shows that the insect feces collected by the pure wheat bran group are block-shaped and compact in structure; while the insect feces of the pure mask group are broken and linear in structure, and the residues of mask fibers in the insect feces can be clearly observed under the electron microscope (right picture).

[0031] 3. Functional groups can characterize the changes in the functional groups of substances and thus reflect the changes in the chemical properties of substances. FI-TR analysis was performed on the original mask, original bran, and the collected insect feces of the pure bran group and pure mask group. The results are as follows: Figure 3 shown.

[0032] Depend on Figure 2 It can be found that the mask structure in the insect feces of the pure mask group has changed, and its CH stretching bond is at 2949cm -1 、2916 cm -1 and 2867 cm -1 The peak at is much weaker than that of the original mask; and the -OH stretching vibration region of the insect feces of the pure mask group (3750~3300 cm -1 ) has a stronger peak than that of wheat bran insect feces and wheat bran original. In addition, the insect feces of the pure mask group is at 1650-1660 cm -1 The peaks near 1067 cm -1 The presence of stretching vibrations of the CO bonds nearby confirmed that the CC main chain of the mask was oxidized in the intestine through a series of oxidation reactions. The results showed that the characteristic chains of the polypropylene mask were destroyed after being digested by the mealworm intestine. The transformation of the mask residues in the insect feces from hydrophobic to hydrophilic surface properties and the emergence of new functional groups also confirmed the degradation of the polypropylene mask.

[0033] 4. TGA analysis was performed on the collected insect feces of the pure mask group. The results are as follows: Figure 4 shown.

[0034] Depend on Figure 4It can be seen that the original mask has obvious mass loss at 370~510℃, about 96.96% of the weight loss occurs in a single stage, and the maximum decomposition rate occurs at 469℃. The weight loss of the pure mask group's feces occurred in three stages: in the weight loss stage below 100℃, it may be the volatilization of some organic components in the mealworm, such as carboxylic acid compounds; in the 100℃-370℃ stage, it is inferred that it may be the digestion products of other organisms that cannibalize the mealworm and the residues of biodegradation of polypropylene masks in the intestine; in the 370℃-510℃ stage, the weight loss of the pure mask group's feces was 59.91%, which was much lower than the original mask (96.55%), indicating that it not only contained residual original masks, but also more new biodegradation products. The TGA results confirmed that disposable medical masks were degraded to varying degrees in the mealworm intestine.

[0035] 5. After a 30-day feeding cycle, the bioassay indicators of each group were counted. The results are shown in Figure 5-9 .

[0036] like Figure 5 As shown, the final weight of the mealworm larvae fed with different mask ratios had no significant difference with that of the mealworm larvae fed with pure wheat bran (P>0.05), and was significantly higher than that of the starvation treatment group (P<0.05). like Figure 6 As shown, there was no significant difference in the final survival rate of the mealworm larvae raised with different mask ratios and that of the mealworm larvae raised with pure wheat bran (P>0.05), and except for the pure mask group, the final survival rate of the mealworm larvae raised with other different mask ratios was significantly higher than that of the starvation treatment group (P<0.05). like Figure 7 As shown, the pupation rates of mealworm larvae in the 20% mask group and the 50% mask group were not significantly different from those of mealworm larvae fed with pure wheat bran (P>0.05), and were significantly higher than those in the other treatment groups (P<0.05). like Figure 8 As shown, the final self-mutilation rate of mealworm larvae in the 20% mask group, 40% mask group, and 50% mask group had no significant difference from that of mealworm larvae fed with pure wheat bran (P>0.05), and was significantly higher than that in other treatment groups (P<0.05). like Fig. 9 As shown in the figure, the mealworm larvae in the 50% mask group consumed 216.1±23.95 mg of mask food, which was significantly higher than that in the treatment groups with other mask ratios (P<0.05).

[0037] The study of the bio-test indicators of all treatment groups found that adding 50% by mass of polypropylene masks in the feed can maximize the consumption of polypropylene masks without affecting normal life development, so it is the optimal ratio.

[0038] The method provided by the present invention is aimed at the characteristic that the natural degradation of discarded polypropylene mask plastic is slow under natural conditions. The discarded polypropylene mask is crushed and fed to yellow mealworm larvae. Yellow mealworm larvae can oxidatively break and depolymerize polypropylene plastic products relatively quickly into non-toxic and harmless organic small molecules and inorganic substances such as carbon dioxide, and mineralize into their own biomass. The present invention has very good effects and a good environment. At the same time, the yellow mealworms used in the present invention do not have any toxicity to the human body, and the process of biological utilization of discarded polypropylene mask plastics will not emit toxic and harmful substances; through characterization means, it is verified that the discarded polypropylene mask material is indeed oxidatively degraded after the action of yellow mealworm intestinal microorganisms; while the yellow mealworms are beneficially utilized, it plays a role in alleviating plastic pollution, and can achieve the effect of resource recycling and "turning waste into treasure".

[0039] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments may still be modified, or some or all of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A biological method for rapidly and efficiently degrading polypropylene masks using mealworm larvae, characterized in that: The following steps are involved: 1) Feed preparation: Cut the discarded polypropylene masks into slices, sterilize them at high temperature, and place them at room temperature to fully air dry, then mix them with wheat bran as feed; 2) Cultivation of mealworms: The feed obtained in step 1) is evenly spread on the bottom of the mealworm larvae cultivation container, and then the mealworm larvae are added for cultivation.

2. A biological method for rapidly and efficiently degrading polypropylene masks using mealworm larvae according to claim 1, characterized in that: The polypropylene purity of the discarded polypropylene mask described in step 1) is ≥99.9%.

3. A biological method for rapidly and efficiently degrading polypropylene masks using mealworm larvae according to claim 1, characterized in that: In step 1), the discarded polypropylene masks are cut into sheets with a size of 2 cm × 3 cm.

4. A biological method for rapidly and efficiently degrading polypropylene masks using mealworm larvae according to claim 1, characterized in that: Step 1) In the obtained feed, the mass ratio of discarded polypropylene masks to wheat bran is 1:

1.

5. A biological method for rapidly and efficiently degrading polypropylene masks using mealworm larvae according to claim 1, characterized in that: Step 2) The density of mealworm larvae in the culture container is 2-3 / cm 2 .

6. A biological method for rapidly and efficiently degrading polypropylene masks using mealworm larvae according to claim 1, characterized in that: The amount of feed used in step 2) is one quarter of the total weight of the insect body.

7. A biological method for rapidly and efficiently degrading polypropylene masks using mealworm larvae according to claim 1, characterized in that: The culture conditions in step 2) are: temperature of 28±1°C, humidity of 65±5%, and dark environment.

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