Introduction

The outbreak of COVID-19 has brought a great deal of global disruption on the social and economic levels. The infection rate and death rate due to the virus are excessive. As of August 2022, the total number of confirmed COVID-19 cases was 591.6 million (Worldometer 2022). Since it is an infectious disease that spreads through respiratory droplets and close contact (Cai et al. 2020), it has been insisted to use masks to reduce the transmission of the virus. It must be noted that it is challenging to filter viruses using any mask. However, the primary purpose of using a face mask is to retard the airflow, which is the primary carrier of viruses. This purpose makes the masks an essential protective measure (Pandit et al. 2021) against the spread of the virus. Thus, PPE consumption, mainly masks, increased, as reported by WHO, which says a 40% increment in the production of disposable PPEs due to the pandemic (World Health Organisation 2020a, b). This increased consumption also resulted in rapid disposal. The COVID-19 pandemic has been estimated to have resulted in 3.5 million metric tons of mask waste being dumped in landfills worldwide in the first year alone. As a result, global municipal solid waste could increase by 3.5% (Patrício Silva et al. 2021). Being synthetic materials, the impact associated with these wastes is also unmanageable. Out of all the PPEs, the disposable mask has significantly contributed to the waste. While analyzing the contamination of coastal sides with PPE, De-la-Torre et al. reported masks were abundant, with a contribution of 87.7% (De-la-Torre et al. 2021). A study has revealed that the cheaper cost of masks and other PPEs and the lack of awareness among the public about the impact made them consume more and dispose of them (Singh et al. 2022).

While addressing the macro-litter problems associated with these disposable masks on one side, recent studies are pointing out the microplastic issues due to the improper disposal of masks. When the masks are disposed of and end up in different environments, they undergo degradation and fragmentation due to external conditions and release microfibers into the environment. As synthetic fibers, primarily, polypropylene, is used in these masks, the microfibers released from the masks are accounted as microplastics. Researchers reported releasing microfibers from the surgical masks when exposed to an aquatic (marine) environment. The chemical and physical degradation of masks under such conditions was noted as the primary reason for the release of microfibers (Saliu et al. 2021). It has been reported that when the masks end up in landfills, they will undergo natural weathering under sunlight which can degrade the masks effectively and lead to increased release of microfibers. Researchers claimed that the microfiber release from disposable masks could increase from 71.06 to 99.99% when exposed to natural weathering (Rathinamoorthy and Balasaraswathi 2022; Shen et al. 2021). However, the analysis of microfiber release kinetics revealed that the release happens faster initially and will gradually slow down (Liang et al. 2022). The prevalence of microplastics and microfibers in the environment and their adverse impact on the ecosystem and human beings are very well known (Chang et al. 2020). The presence of microplastics in human lungs, placenta, hair, skin, and blood was evidenced (Abbasi et al. 2019; Goodman et al. 2021; Leslie et al. 2022; Ragusa et al. 2021), and these particles were noted to impact cell morphology and inhibit cell proliferation (Goodman et al. 2021). Yee et al. reported inflammation, apoptosis, and metabolic homeostasis as effects of human exposure to microplastics (Yee et al. 2021). It is, therefore, essential to deal with the problem with utmost care.

The disposal issue of surgical masks is being addressed from different perspectives, such as at the production stage (use of bio-based alternatives for synthetic materials), consumption stage (extending the usage period by reusing masks), and disposal stage (recycling of masks into valuable resources). The use of biodegradable polymers as filtering membranes, the use of natural fibers with antibacterial/antimicrobial finishes, and the use of cellulose and nanocellulose-based materials were explored (in manufacturing) by different researchers as an alternative for the synthetic materials used in the disposable masks (Costa et al. 2022; Garcia et al. 2021; Pandit et al. 2021). However, these biodegradable sustainable materials fail to beat synthetic fibers in terms of performance, easy availability, and also in cost. When the reusing strategy is considered, the single-use disposable masks were explored (in consumption) for their reusability after disinfection. Treatments with hydrogen peroxide, plasma, and ultraviolet germicidal irradiations (Ibáñez-Cervantes et al. 2020; Rubio-Romero et al. 2020; Yang et al. 2020) were studied for their disinfectant ability. Researchers studied the effectiveness of different methods of disinfection methods, such as treating in hot water at 40 °C and 80 °C, autoclave, microwave at 750 W, and ultraviolet germicidal irradiations, out of which immersion in hot water at 80 °C and microwave sterilization methods showed a higher level of disinfection (Scaglione et al. 2022). These disinfection processes can increase usage cycles and reduce consumption and disposal rates. However, economic feasibility and consumers’ knowledge about these technologies are essential to adopt such practices domestically.

The third category is the management of disposed masks after their life. While exploring the proper management of these disposed-of masks, recycling was noted as a promising strategy, and few studies were performed to recycle the masks into valuable products. The disposable masks made of polypropylene fibers were recycled into composites with reinforcement of natural fibers (sisal and hemp) to find applications as packaging materials and cutleries (Pulikkalparambil et al. 2022). Varghese et al. developed a blend of recycled polypropylene fibers and nitrile rubber with a maleic anhydride compatibilizer. The developed blend showed a better thermomechanical property that makes it suitable for different engineering applications (Varghese et al. 2022). The disposed masks were cut and recycled using the melt extrusion method, where the extruded recycled materials were made into pellets and were analyzed for thermal, chemical, and mechanical properties (Battegazzore et al. 2020). Similarly, the other researcher demonstrated the mechanical recycling method for the recycling of face masks and developed blends which can be processed using melt extrusion and injection molding equipment. These materials are noted to be suitable for the applications such as flower pots, storage bins, shipping pallets, or toys (Crespo et al. 2021).

Based on the previous literature, it is evident that the masks are recycled into different engineering products that find applications more popularly as packaging materials and composites. However, none of the research addressed reusing such reclaimed fibers in the textile application. Hence, this study aims to develop a textile-based product by recycling disposable tri-layer masks to reduce plastic waste and the corresponding microplastic pollution. The masks are recycled to extract the fibers back mechanically, and the reclaimed fibers from the masks were blended with cotton fibers to produce rPP/cotton blend yarns. The fabrics developed from recycled yarns were analyzed for their physical properties to find a suitable application, and it is also evaluated for the microfiber release potential as a textile material.

Materials and methods

Materials

Used masks were collected from different collection points inside the educational institution. The collected masks were segregated for their types, where tri-layer non-woven masks were identified and used for this analysis. The top and bottom layers of the masks were noted as spun bonded non-woven, whereas the intermediate layer was made of melt-blown non-woven structure. This analysis did not use other types of masks, including cloth masks. For blending purpose, raw cotton fiber was sourced from Coimbatore, India. The average cotton fiber length is 28 mm, and fineness was noted as 1.35 dtex.

FTIR analysis

The fiber composition of the masks was confirmed as polypropylene by FT-IR analysis. KBr plate sample testing method has been adopted where the FT-IR spectrum was measured with 4000/cm to 400/cm wave numbers at 1.0/cm resolution.

Disinfection and shredding

The collected masks were quarantined for 14 days and then subjected to a disinfection process using an autoclave at 120 °C for 1 h. The autoclaved masks were shadow-dried inside a room till it gets completely dried. After the disinfection, the masks were cut using scissors to eliminate the nose wire, ear loops, and the melt-blown filtration layer in the middle. The masks’ outer and skin-contact layer (spun-bonded non-woven) were carefully taken and further cut into smaller pieces. The cut pieces were then passed into a mechanical shredder, shredding the fabric to form fibers. These reclaimed polypropylene fibers (rPP) were used for subsequent yarn preparation. The average length of rPP fiber is ~ 12 mm, and fineness was noted as 1.2 dtex.

Development of recycled yarn using the rotor spinning

Attempts were made to produce 100% recycled polypropylene (rPP) yarns. However, the fibers were clogged into the carding cylinder due to different fiber lengths (after shredding). Hence, virgin cotton fibers were blended with rPP fibers in different ratios during the carding process, namely 50/50, 60/40, and 70/30 (cotton/rPP). The developed sliver is passed through the draw frame and spun into yarn using a rotor spinning machine with a rotor speed of 20,000 rpm and 18 twists per inch with a Z twist. The feed hank count is 0.15 Ne, the opening roller speed is 5000 rpm, and the resultant yarn count is 10 Ne. The detailed yarn manufacturing process flow is provided in Fig. 1.

Fig. 1
figure 1

The manufacturing process of fabric by recycling polypropylene disposable masks

Full size image

Characterization of yarn

The developed yarns were characterized for their physical properties at standard atmospheric conditions (temperature — 20 ± 2 °C and relative humidity — 65 ± 4%) as per the standard ISO 139: 2005. The following tests were conducted for the developed yarns of different compositions (50/50% cotton/rPP, 60/40% cotton/rPP, 70/30% cotton/rPP) and 100% cotton yarn.

  • Single-yarn tenacity and elongation were estimated using Uster tenso rapid 4 as per standard ASTM D 2256–02, where the actual strength, CV% of strength, % elongation, CV% of elongation, and RKM (g/tex) were calculated.

  • U% Imperfections like mean U%, mean CVm%, thin places (− 50%), thick places (+ 50%), neps (+ 200%), and neps (+ 280%) were calculated using Ustar unevenness tester 5 as per ASTM D1425/D1425M-14 (2020).

  • Hairiness was estimated using Uster unevenness tester 5.

Development of knitted fabric and its characterization

Knitted fabrics were produced from the motorized socks knitting machine with 160 needles, with a speed of 220 rpm and a diameter of 4 inches. The developed fabrics were evaluated for their physical and mechanical characteristics like thickness (ASTM D 1777–96), grams per square meter (ASTM D 3776), bursting strength (ASTM D 3786), abrasion resistance (ASTM D 4966), absorbency (BS 4554), air permeability (ASTM D 737–04), water vapor permeability (BS 7209: 1990), and vertical wicking (AATCC 197) as per respective standard test methods.

Microfiber release characteristics analysis

As the masks were reported to release microfibers, the fabrics developed by recycling masks can also release fibers. Hence, the microfiber release of masks and the fabrics was analyzed at different life stages.

Microfiber release from disposable masks

The microfiber release from the masks was examined at the usage and disposal stage. The wear time release was analyzed by rubbing the masks in a dry state to resemble the wear time abrasion, as reported in the previous study (Rathinamoorthy and Balasaraswathi 2022). The release was examined for the new and naturally weathered masks at the disposal stage. The microfiber release from the new mask was analyzed by soaking the mask in tap water for 5 min and rubbing and beating it with the help of a plastic rod for 10 min. A similar method of microfiber release analysis was done for the samples, which are kept on the terrace of the institute building for 30 days (August 22, 2022, to September 20, 2022) for natural weathering. The geographical and atmospheric conditions during weathering were as follows: location coordinates — 12.9120° N, 77.6526° E; average temperature — 24 °C; average rainfall — 241 mm; average daylight — 12.5 h; average humidity — 76%; average UV index — 12.

Microfiber release from fabrics developed using reclaimed fibers

Similar to masks, the microfiber release during wear time was analyzed, and based on the previous literature (Klepp et al. 2020; Wiedemann et al. 2020), the average number of wear was taken as 75. Throughout its lifetime, fabrics will be washed (maximum of 40 washes, assuming one wash cycle after two wear cycles) and then disposed into landfills. Hence, to replicate domestic laundering, fabrics were washed at laboratory scale as per standard ISO 105 C06, and the wash liquor was filtered to retain the microfiber released. Since polypropylene fibers come under the microplastic category because of their synthetic nature, only polypropylene fibers were considered in the quantification. Since the microfiber release will stabilize after the fifth wash (Belzagui et al. 2019), the fabrics were washed five times, and the fiber release at the fifth wash was considered for the subsequent washes. To replicate the weathering of fabrics, they were exposed to natural weathering similar to masks, and the microfiber release was examined using the same procedure.

All the wash samples are filtered using Whatman Grade 1 filter paper (pore size of 11 µm) and are examined with Digital Microscope (× 1000) to count the number of fibers and convert them into the mass of fibers released. The counting method and weight conversion method have been adopted from previous studies (de Falco et al. 2018; Napper and Thompson 2016).

Results and discussion

Analysis of mask

The collected masks were analyzed using an FT-IR spectrometer to understand the chemical composition, and the results are presented in Fig. 2. Results showed standard peaks of non-woven fabrics in the front and back sides of the mask and confirmed that the layers were made of polypropylene fibers. In Fig. 2, peaks in the wavelength of 2900–2950 cm−1 represent CH-stretch vibrations, and the CH2 and CH3 deformations were noted at the wavelengths of 1450 cm−1 and 1380 cm−1, respectively. Prominent peaks at 1170 cm−1, 950 cm−1, and 850 cm−1 showed the standard peaks of polypropylene fiber (Akarsu et al. 2021). Based on the identified peaks and their corresponding chemical structure, it can be noted that the top and bottom layers of masks are polypropylene fibers.

Fig. 2
figure 2

FTIR spectrum of the spun-bonded layer of disposable mask

Full size image

Yarn characteristics

The reclaimed PP fibers from masks were blended with cotton fiber in different ratios, namely 50/50, 60/40, and 70/30 (cotton/rPP), and yarns were developed. The result shows a significant reduction (~ 35%) in the tensile strength of the blended yarns compared to the 100% cotton yarn. When the blended yarns are considered, the increase in the proportion of rPP fibers increases the tensile strength, which is evident from the higher positive correlation of 0.93 between the percentage of rPP in the yarn and the tensile strength of blended yarns. A similar trend was also noted in the case of RKM value, where blended yarns showed a lesser RKM value than the 100% cotton yarn; however, in the blended yarns, an increase in rPP content increased the RKM value (correlation coefficient, r = 0.93). In the case of elongation percentage, a higher elongation was noted with 100% cotton yarn compared to blends. When the blended yarns are considered, increased rPP composition increases the elongation (correlation coefficient, r = 0.91). This increment in the blended yarn elongation is associated with the higher elongation of the rPP fibers. These findings were in line with the previous research, where the researchers evaluated the properties of cotton polypropylene blended yarn (Behera et al. 2001). Within the rPP blend composition, a reduction in the rPP content showed a lower extension. The unevenness (U%) and coefficient of variations (CV%) were observed to increase with increased rPP proportion in the yarn composition. However, like the elongation value, the U% and CV% were also noted less for 70/30 C/rPP composition. Figure 3 shows the relationship between the rPP compositions and the yarn characteristics.

Fig. 3
figure 3

Relationship between the proportion of rPP in the yarn and the yarn characteristics

Full size image

A similar trend was reported in the case of thin, thick, and neps in the blended yarn. The 50/50 and 70/30 C/rPP yarns showed higher thick and thin places than the 100% cotton yarn. However, the case of 60/40 C/rPP yarns showed a statistically significant reduction in the thin and thick places. The addition of rPP considerably reduced the nep content in the recycled yarn compared to the 100% cotton yarn. As reported earlier, though all rPP blended yarns showed a reduction in nep count, a significant reduction was reported with 60/40 rPP/cotton yarns. These changes might be attributed to the higher uniformity and smooth surface of the rPP fibers on the outer surface of the yarn structure (Silich 2012). In contrast to the above properties, the hairiness percentage increased with the blended yarn. Specifically, 60/40 rPP/cotton yarns showed 10.12% hairiness, higher than all other blend proportions and 100% cotton yarn. The fiber lengths were not uniform because the mechanical shredding produced the rPP fibers. Furthermore, during the yarn manufacturing, though the rPP was aligned in the core layer of the yarn, a higher projection was reported on the outer side due to shorter fiber length, as shown in Fig. 4 (Silich 2012). Due to the presence of short fibers outside the yarn structure, higher hairiness was evident in these yarns.

Fig. 4
figure 4

Arrangement of reclaimed polypropylene fiber (blue fibers) in the blended yarn structure

Full size image

Fabric characteristics

60/40 Cotton/rPP yarns were further taken for the fabric manufacturing process due to their lower imperfections with higher rPP content. Whereas, in the case of 50/50 cotton/rPP yarns, higher yarn breakages and knitting needle breakages limited the fabric production using motorized socks knitting machine. The developed 60/40 cotton/rPP fabric was evaluated for its physical and mechanical properties, and the results were compared with that of 100% cotton fabric with similar constructional parameters, as provided in Table 1.

Table 1 Fabric characteristics of knitted fabrics made of 60/40 cotton/rPP blended yarns
Full size table

Regarding the physical properties, a reduction in the strength was reported in the developed rPP fabric compared to 100% cotton fabric. The same results were also evident in the case of single yarn strength, where adding rPP fibers reduced the tensile strength. This reduction in strength was expected as the quality (surface and physical properties) of the rPP fiber was not up to the level of virgin polypropylene fibers. Hence, our results contradicted the previous literature, which reported that adding polypropylene as a blend in the cotton yarn subsequently increased the yarn and fabric strength (Behera et al. 2001). In the case of permeability, developed rPP blended fabric showed a lower permeability to air and water vapor than 100% cotton fabric. These results are mainly due to the higher hairiness properties and structural compactness of the rPP fabric compared to cotton fabric. The higher hairiness of fabric made of rPP fibers resists the air and moisture flow due to the reduction in the pore size between those yarns. These findings can also be related to the slight variation in the thickness and GSM of the two fabrics (Nazir et al. 2014). Secondly, higher structural compactness associated with coarser count and higher tightness factor of the recycled yarn restricted the permeability characteristics. A significantly lower absorbency was reported with the rPP fabric compared to the cotton fabric. The increment in the absorbency time of the rPP blend fabric was mainly due to the presence of hydrophobic rPP fibers in the yarn. A few rPP fibers in the yarn structure lie on the outer surface, and a reduction in absorbency was reported in the rPP fabric. Similarly, lower wicking was reported for the developed rPP blend fabric. Though polypropylene fiber usually increases the wicking behavior, the reduction is associated with the staple nature of the rPP fibers over filament. When it is filament, the twist required for the yarn formation is lesser than for the staple fibers. With an increased twist, the wickability is reduced as the yarn will have a densely packed structure (Li et al. 2017).

The abrasion resistance results showed a higher weight loss percentage of rPP fabric compared to the cotton fabric due to the presence of very short rPP fibers than the cotton fabric. As rPP fibers migrate towards the outer surface of the yarn while applying pressure, chances for release of the PP fibers were unavoidable in this case also. The structure of both 100% cotton fabric and 60/40 C/rPP fabric is provided in Fig. 5. Based on these characteristics, it can be concluded that despite their lower mechanical properties (compared to 100% cotton), the fabric has higher potential in the apparel endues. Though a lower absorbency was reported, good air and moisture permeability with wicking showed its potential as apparel in outerwear applications. Due to higher thickness and GSM, scopes of skin contact layers like inner wear are minimal.

Fig. 5
figure 5

Structure of A 100% cotton fabric, B 60/40 cotton/reclaimed polypropylene fabric and C polypropylene spun bonded non-woven fabric

Full size image

Microfiber release analysis

The microfiber release behavior of developed fabrics was analyzed and compared with that of disposable masks. For both fabrics, microfiber release was evaluated throughout their life cycle. For masks, the microfiber release will happen during wearing (1 time) and then at the disposal stage (environmental exposure). For fabrics, the microfiber release will happen during wearing and washing (multiple times) and then at the disposal stage (environmental exposure).

For masks, the wear time release was measured by rubbing the non-woven layer against itself, as reported in the literature. After usage, the masks will be disposed of in the environment. The microfiber release from a new mask when ended up in an aquatic environment is evaluated by soaking and rubbing it in the water (Saliu et al. 2021)). After that, weathering these masks under environmental conditions can accelerate the microfiber release (Saliu et al. 2021; Shen et al. 2021). Hence, the release after weathering for 30 days was taken into account. Similarly, for fabrics developed out of reclaimed fibers from masks, the wear time release was measured as per Laitala et al. (2018), and release during washing is also considered (40 washes). While washing, the fiber release was high at the initial washes, and it can get stabilized after the fifth wash (Belzagui et al. 2019); hence, the microfiber release at the fifth wash has been taken for all the subsequent washes.

After disposal, the fabrics are also expected to undergo similar conditions like masks, and the same method is adopted for microfiber release estimation. Table 2 summarizes the microfiber release of masks and fabrics in their lifetime, and Fig. 6 shows the microfibers released from the fabric and mask. As per the yarn production data, 100-g fibers can develop 1185.35 m of 60/40 c/rPP yarn with the previously mentioned rotor spinning conditions. Based on this information, it was estimated that to produce a square meter of fabric, we required 203.35 g of fiber, out of which (40%) 81.34 g of fibers are rPP. Similarly, for comparison purposes, the area of the mask that can contain the same amount of polypropylene fibers was estimated. It was found that 3.253 sq. m of polypropylene spun-bonded non-woven layer of 25 GSM will have 81.34 g of fibers. With this background, similar quantities of developed rPP fabric and 100% pure spun bonded fabrics were compared. The estimation showed that 3.235 sq. cm of non-woven fabric contains an equal amount of polypropylene as in 1 sq. cm of knitted fabric. From this analysis, a square centimeter of PP non-woven fabric can release 399.16 microfiber/sq. cm, whereas the rPP knitted fabric can release 218.59 fibers/sq. cm. Based on these facts, we compared the microfiber release characteristics of those fabrics. The results showed that 218.59 fibers/sq. cm were released throughout the lifetime, whereas a similar amount of masks (3.235 times) showed the release of 1298.47 fibers. Thereby, a reduction of 83.17% was noted in the recycled fabric. The difference is mainly associated with the compact structure of yarn in recycled fabrics compared to non-woven fabrics. It is worth mentioning that the fibers are in the form of a twisted state in the yarn structure. The twist inserted during the yarn manufacturing had an impact on holding the rPP fibers inside the structure. This was the first reason for the lower release of fiber. Along with this, the role of fabric parameters (tightness factor and GSM) is also to be considered as the yarns were knitted into the fabric. The structure formed by the fabric also acts as a barrier and restricts the release of the reclaimed fibers included in the structure. In the case of non-woven, the fibers are directly bonded into fabrics, as shown in Fig. 4. When a specified force is applied to this material, like abrasion and laundry, the release rate highly differs due to their structural difference. This higher fiber release in non-woven fabrics was in line with the previous reports, which showed a 70% increment in the microfiber release with the non-woven made of cotton compared to the cotton knitted fabric (Kwon et al. 2021). Moreover, the analysis of the developed blended yarn structure (Fig. 4) showed that though some rPP fibers can be found in the outer sheath of the yarn, most of the fibers were bound inside by the cotton fibers. Additionally, the insertion of a twist in the yarn (18 TPI) significantly reduced the rPP fiber release from the structure. In the case of spun-bonded non-woven, the fibers were fused at a random point. Though other construction parameters like GSM and thickness significantly impact microfiber release (Raja Balasaraswathi and Rathinamoorthy 2021), they cannot be compared in this case, as these fabrics are manufactured by different technology.

Table 2 Summary of the microfiber release from masks and recycled fabrics in their lifetime
Full size table
Fig. 6
figure 6

Microfiber release from A, B mask and C, D recycled knitted fabric

Full size image

Implication of the study

After COVID-19, the increased use and disposal of single-use disposal masks jeopardized environmental health. Hence, several attempts were made to reuse or recycle such disposed masks to reduce their immediate environmental impact. However, many such research works were energy intensive and caused higher environmental footprints. Table 3 summarizes the methods of recycling masks experimented with in literature. Studies reported methods to convert the disposed-of masks into biochar by treating the mask at 350 °C (Emenike et al. 2022). Other researchers melted the polymers and developed injection molded samples from the disposed-of mask (Crespo et al. 2021). Few other researchers used the disposed-of masks for the oil sorption process after heptane treatment; however, no information was provided about their microfiber release behavior (Park et al. 2022), whereas few other researchers evaluated the use of polypropylene from disposed face masks and nitrile glows using compression molding techniques (Varghese et al. 2022). Similarly, other researchers tried the possibility of using the mask in construction material (Idrees et al. 2022; Parija et al. 2020), covering as a filtration membrane (Cavalcante et al. 2022), floor tiles (Remic et al. 2022), and also as composites (Jingfang et al. 2022). Though these processes were able to provide alternative ways of utilizing the waste, the amount percentage utilized, energy used for the conversion process, and their subsequent carbon footprints are often not considered. In contrast, the current study proposes a recycling option as an alternative method to reduce microfiber pollution from reusable disposable masks. In this recycling method, the spun-bonded layers in the masks are recycled, whereas the meltblown layers, earloops, and nose pins are eliminated, and 80.5% (based on weight) of masks are recycled. The advantage of such a method is lower energy requirement and carbon footprint due to their mechanical processing over the thermal method with a higher percentage of fiber use (40% rPP fibers) with their corresponding microfiber release behavior. The conversion of shredded polypropylene fibers into yarn and subsequently as fabric reduced the microfiber release by up to 83.17%. The best part of this recycling method is the higher quantity of mask utilization at a cheaper cost than other methods.

Table 3 Literature summary of mask recycling process with their proportion of utilization and challenges
Full size table

If this recycling method is adopted on a large scale, the waste associated with disposable masks can be significantly reduced. Previous studies reported consumption of 4.64 × 109 masks per week in India alone (Selvaranjan et al. 2021), and with the implementation of the proposed recycling method, 80.5% of the waste can be reduced. Considering the average weight of a single mask as 3.44 g, India alone can release around 430 tons of polypropylene microfibers into the environment (Rathinamoorthy and Raja Balasaraswathi 2022a, b). However, this recycling method reduces microfiber release by up to 83.17%; hence, if at least 50% of the discarded masks are recycled into the fabric, then the entire microfiber release can be brought down from 430 to 251.18 tons/week. Based on this information, it can be estimated that this release can be further reduced to 72.3 tons/week if all (100%) of the discarded masks are recycled into fabrics.

Conclusions

This study evaluated the potential of mechanical recycling in converting the discarded used mask into fibers and utilizing them in the textile application. The reclaimed polypropylene (rPP) fibers were blended with cotton fiber, and yarns with different (cotton/rPP) ratios were produced. Based on the yarn characteristics, 60/40 cotton/rPP yarn was converted into the fabric, and their properties were analyzed. Based on the proposed apparel endues, the recycled fabrics were also analyzed for their microfiber emission characteristics and compared with the release of disposed-of masks. The current research showed a significant reduction in the emission of microfibers (83.17%) from the developed fabric compared to the same non-woven mask (based on fiber weight). By converting the used masks into textiles, these recycling options help us restrict around 178 tons of microfibers/week from entering the environment, even if 50% of the improperly disposed-of masks are recycled in this method.

Additionally, mechanical recycling and developing it as the fabric was noted to be a cheap and more straightforward process with higher fiber utilization (%). Though the conversion of fabric seems to be a better option than the direct disposal of masks, the microfiber emission from the fabric persists in the developed fabric. The structure of the yarn showed that the rPP fibers were packed inside the structure; however, during the process of laundry, wearing, and mechanical abrasion, the applied pressure forced the fiber to release. As we estimated the lifetime fiber release from the average cloth utilization data, we found that the developed recycled fabric can release around a 218 microfiber/sq. cm in its lifetime with a massive reduction compared to the disposed-of non-woven masks. Future research must focus on this aspect to eliminate this limitation by reducing emissions, promoting recycling, and effectively utilizing used masks.