Microfibers Research Articles

Engineering of clarithromycin loaded stimulus responsive dissolving microneedle patches for the treatment of biofilms

This study aimed to fabricate clarithromycin laden Eudragit S-100-based microfibers (MF), microfibers coated film (MB), clarithromycin loaded polyvinyl pyrollidone, hyaluronic acid and sorbitol-based dissolving microneedle patches (CP) and microfibers coated microneedle patches (MP). Morphological and phase analysis of formulations were carried out by scanning electron microscopy and differential scanning calorimetry, X-ray diffraction, respectively. Substrate liquefaction test, in vitro drug release, antimicrobial assay and in vivo antibiofilm studies were performed. MF exhibited a uniform surface and interconnected network. Morphological analysis of CP revealed sharp-tipped and uniform-surfaced microstructures. Clarithromycin was incorporated within MF and CP as amorphous solid. Liquefaction test indicated hyaluronate lyase enzyme responsiveness of hyaluronic acid. Fibers-based formulations (MF, MB and MP) provided an alkaline pH (7.4) responsive drug release; ∼79 %, ∼78 % and ∼81 %, respectively within 2 h. CP showed a drug release of ∼82 % within 2 h. MP showed ∼13 % larger inhibitory zone against Staphylococcus aureus (S. aureus) as compared to MB and CP. A relatively rapid eradication of S. aureus in infected wounds and subsequent skin regeneration was observed following MP application as compared to MB and CP indicating its usefulness for the management of microbial biofilms.

Synthetic microfiber emissions from denim industrial washing processes: An overlooked microplastic source within the manufacturing process of blue jeans

In recent years, domestic laundry has been recognized as a relevant source of microfiber (MF) pollution to aquatic environments. Nevertheless, the MF emissions from industrial washing processes in real world scenarios have not been quantified. The aim of this study was to quantify the MF emissions from 3 industrial washing processes (rinse wash, acid wash and enzymatic wash) commonly employed in the manufacturing process of blue jeans. The blue jeans were characterized by ATR-FT-IR, SEM and TGA to study the morphology, the polymer chemical identity and the proportion of synthetic and natural fibers, respectively. The MF emissions were quantified as the MF mass and number emitted per washed jean. All the industrial washing processes released a majority of synthetic MF. The enzymatic wash produced the highest amount of MF, with 1423 MF per gram of fabric (MF/g) equivalent to 381.7 MF grams per gram of fabric (MF g/g), followed by the acid wash with 253 MF/g equivalent to 142.7 MF g/g and lastly the rinse wash with 133 MF/g equivalent to 62.3 MF g/g. Statistically significant differences between the MF sizes for all washing processes were found when evaluating the emissions by MF/g, however, the previous trend was not found for MF g/g. Moreover, the total MF emissions of an industrial washing process of a pair of blue jeans during its manufacture process are up to 10.95 times higher than the reported domestic washing estimates performed by the consumer available in the published literature. We demonstrate that studying industrial washing procedures of textile garments will improve the accuracy of the current estimates of MF emissions available in published reports, which will ultimately aid in the development of regulations for MF emissions at an industrial level.

Effects of Household Cleaning Supplies on Trace Blood Evidence

This research is useful in forensic laboratories to prevent contamination. If a cleaner was found to remove all traces of blood, it could be used to sterilize lab benches and equipment to ensure no cross contamination between pieces of evidence. It could also be used in the field to determine which presumptive test would be more useful in different scenarios. The purpose of this project was to determine if common household cleaners could efficiently remove the presence of blood. To test this theory, I used hydrogen peroxide cleaner, dawn dish soap, and Clorox bleach to clean blood from three surfaces, laminate flooring, textured glass, and carpet. This was done using two different cleaning materials, paper towels and microfiber cloths, at 3-time intervals. After removing the visual evidence of blood, I tested for residual blood using two different presumptive tests, tetramethylbenzidine and phenolphthalein.
 Results show that three out of the twelve variable combinations gave all positive results. Over 50% of the presumptive tests ran on textured glass were negative. From the results of the presumptive tests, it was found that the tetramethylbenzidine test was more sensitive than the phenolphthalein test. Household cleaners do not effectively clean up blood, leaving behind enough residual blood to test positive using presumptive blood tests. The tetramethylbenzidine test was more sensitive than the other. More variables should be tested to determine the effects of household cleaners on surfaces such as furniture. Different presumptive tests should also be examined.

Design and fabrication of nickel lanthanum telluride microfibers for redox additive electrolyte-based flexible solid-state hybrid supercapacitor

In this article, we describe the design of a flexible solid-state hybrid supercapacitor (FSSHSC) using mixed metal telluride NiLaTe microfibers (MFs) atop Ni foam (NF). The goal of the study is to examine the effect of counter metal ions Ni and La, in addition to Te, in the formation of longer one-dimensional (1-D) architecture. The NiTe MFs and La2Te3 microrods (MRs) were synthesized and compared with bimetallic telluride. La exhibit's slower reaction kinetics than Ni when reacting with Te due to the different crystal structural stability of La2Te3 (cubic phase) and Te (hexagonal phase). Three-electrode investigations incorporating aqueous potassium ferrocyanide (KFC) reveal that the electrochemical performance of NiLaTe MFs is doubled compared to the typical aqueous KOH electrolyte alone. The presence of the redox pair [Fe(CN)6]3−/[Fe(CN)6]4− allows for faster ion transport inside the active electrode surface, which improves electrochemical performance. The FSSHSC device was fabricated, comprising NiLaTe as the positive, activated carbon (AC) as the negative electrode, and PVA-KOH-KFC gel, which acts as an electrolyte and a separator. The device performance was compared to that of a liquid system as well as one without a redox additive gel system. The significance of polymer-based gel and KFC for device construction is briefly reviewed. The final built device NiLaTe//AC in gel + KFC system has a maximum areal capacity of 65.6 μAh cm−2 (60.0 mA h g−1) at a current density of 2 mA cm−2, a maximum energy density of 45.5 Wh Kg−1 (52.36 μWh cm−2), and a maximum power density of 5488.7 W Kg−1(6312.0 μW cm−2). Furthermore, the device outperforms the cyclic stability for 10,000 cycles with an 80.1 % capacity retention and exhibits excellent flexibility at different bending angles. The assembled FSSHSCs device successfully illuminates an LED bulb for 70 s.

Centrifugal Melt Spun Microfi brous Solid Dispersion of Diclofenac Sodium with Enhanced Solubility

A lower dissolution rate of poorly soluble drugs is the prime factor aff ecting their bioavailability. The centrifugal melt spinning method is a simple, aff ordable and scalable technique to prepare microfi bers with enhanced solubility and dissolution rate. This study aimed to enhance the solubility and dissolution rate of poorly soluble drug diclofenac sodium by centrifugal melt spinning technique. Microfi brous solid dispersion of diclofenac sodium 10% w/w with sucrose were prepared to utilize a cotton candy device. The dissolution studies revealed that the drug-loaded microfi bers released 98.10 ± 0.52% of drug within 5 minutes as compared with pure drug and physical mixture. The drug-loaded microfi bers were bead-free with uniform morphology and diameter of 13.25 ± 4.4 μm. The centrifugal melt-spinning process converted the drug and carrier to amorphous state, which was further confi rmed from the calorimetric and crystallographic study results. The results indicated that the centrifugal melt spinning process rapidly produced microfi bers with improved solubility and dissolution rate. The results of this study have shown that the centrifugal melt spinning technique may provide an easy, highly scalable, and adaptable fabrication technique to increase the solubility and rate of dissolution of poorly soluble drugs.

Composite Fibrin and Carbon Microfibre Implant to Modulate Postraumatic Inflammation after Spinal Cord Injury.

Poor functional recovery after spinal cord injury (SCI) drives the development of novel strategies to manage this devastating condition. We recently showed promising immunomodulatory and pro-regenerative actions of bio-functionalized carbon microfibres (MFs) implanted in a rodent model of SCI. In order to maximize tissue repair while easing MF implantation, we produced a composite implant based on the embedding of several MFs within a fibrin hydrogel. We used intravital imaging of fluorescent reporter mice at the early stages and spinal sections of the same animals 3 months later to characterize the neuroinflammatory response to the implant and its impact on axonal regeneration. Whereas fibrin alone was inert in the first week, its enzymatic degradation drove the chronic activation of microglial cells and axonal degeneration within 3 months. However, the presence of MFs inside the fibrin hydrogel slowed down fibrin degradation and boosted the early recruitment of immune cells. Noteworthy, there was an enhanced contribution of monocyte-derived dendritic cells (moDCs), preceding a faster transition toward an anti-inflammatory environment with increased axonal regeneration over 3 months. The inclusion of MF here ensured the long-term biocompatibility of fibrin hydrogels, which would otherwise preclude successful spinal cord regeneration.

Microplastics: The stemming environmental challenge and the quest for the missing mitigation strategies

Repetitious manufacturing, usage and irresponsible disposal trigger the breakdown of primary and secondary plastics, ending up in aquatic, terrestrial, and pristine locations like arctic tundra due to their diaphanous property. Owing to their origin, size, interaction with other contaminants, and chemical behavior they can be very idiosyncratic; they not only accumulate in the ecosystem, imparting chemical alterations but also are being consumed by the aquatic and terrestrial animals leading to hazardous consequences. Washing machine wastewater significantly contribute to the global microplastic load. For the past few years, microplastics (MP) and microfibers (MF) have been contaminants of grave concern pertaining to their deleterious nature against human, marine, and ecosystem health and grabbed the attention of environmental researchers. This review sums up the inimical ramifications of these tiny particles on biota, their types and characterization strategies, along with the biological removal strategies of these plastics and fibers highlighting the circular economy approach to limit them in the source and the enzymatic pathways regulating their eradication. Additionally, there are several research gaps in the biological remediation of these particles, which can be explored further to develop distinct, lucrative and ecologically reliable technologies for combating this mammoth (ironically) environmental adulterants.

A Study of Microfiber Phytoremediation in Vertical Hydroponics

Microfibers (MFs) are one of the most prevalent microplastic (MP) sub-groups found in the aquatic environment released from many sources, including household laundry. MPs pose risks to the growth rate of terrestrial/aquatic biota and through biomagnification. Although MFs can be ingested by humans, their toxic effects and potential impact on public health are not yet clearly understood. Moreover, the removal of MPs, including MFs, during wastewater treatment is a challenge, since treatment plants are not designed to collect them. Therefore, this work aims to study the potential of the in situ phytoremediation of microfibers from a domestic washing machine effluent by growing barley in a vertical hydroponic system. The temporal variation in barley growth, water quality parameters, length distribution of MFs, and their removal were evaluated over 4 weeks. We investigated the MFs’ interaction with two systems: without barley (System NP) (used as a control) and with barley (System P). The results show the barley growth is negatively affected at the end of 4 weeks, mainly by the accumulation of phosphate and the presence of fungi. However, the level of dissolved oxygen in System P is satisfactory and the presence of MFs decreases considerably (mainly for MFs > 600 µm) from different interactions with the barley roots. These interactions were corroborated by microscopy images. The total removal of MFs through the hydroponic system was 52% in week 2, decreasing to 42%. This is the first time that the removal of MFs has been evaluated using vertical hydroponics, which demonstrates that this phytoremediation system can be used at the household level. It also shows that vertical hydroponics, as an experimental methodology, for the analyses of MFs’ impacts on plant health has merit. It is expected that this study will contribute to new investigations of MF removal by green technologies.

Effects of cleaning spray use on eyes, airways, and ergonomic load

BackgroundCleaning workers are exposed to chemicals and high physical workload, commonly resulting in airway problems and pain. In this study the response in the upper airways and the physical workload following airborne and ergonomic exposure of cleaning spray was investigated.MethodsA survey was answered by professional cleaning workers to investigate their use of cleaning sprays and the perceived effects on eyes, airways and musculoskeletal pain. A human chamber exposure study was then conducted with 11 professional cleaning workers and 8 non-professional cleaning workers to investigate the airborne exposure, acute effects on eyes and airways, and physical load during cleaning with sprays, foam application and microfiber cloths premoistened with water. All cleaning products used were bleach, chlorine, and ammonia free. The medical assessment included eye and airway parameters, inflammatory markers in blood and nasal lavage, as well as technical recordings of the physical workload.ResultsA high frequency of spray use (77%) was found among the 225 professional cleaning workers that answered the survey. Based on the survey, there was an eight times higher risk (p < 0.001) of self-experienced symptoms (including symptoms in the nose, eyes and throat, coughing or difficulty breathing) when they used sprays compared to when they cleaned with other methods. During the chamber study, when switching from spray to foam, the airborne particle and volatile organic compound (VOC) concentrations showed a decrease by 7 and 2.5 times, respectively. For the whole group, the peak nasal inspiratory flow decreased (-10.9 L/min, p = 0.01) during spray use compared to using only water-premoistened microfiber cloths. These effects were lower during foam use (-4.7 L/min, p = 0.19). The technical recordings showed a high physical workload regardless of cleaning with spray or with water.ConclusionSwitching from a spraying to a foaming nozzle decreases the exposure of both airborne particles and VOCs, and thereby reduces eye and airway effects, and does not increase the ergonomic load. If the use of cleaning products tested in this study, i.e. bleach, chlorine, and ammonia free, cannot be avoided, foam application is preferable to spray application to improve the occupational environment.

Release of microfibers from surgical face masks: an undesirable contributor to aquatic pollution

The worldwide usage of surgical face masks (SFM) has increased rapidly during the COVID-19 pandemic. Its degradation possibly produces billions of microplastics (MPs) in the environment. To quantify the release of microfibers (MFs), unused SFM were treated with eight different aqueous solutions, each with five replications in two categories, i.e., freshwater (FW) treatments [800 mL FW, 40 mL of 95% alcohol + 800 mL FW, 40 mL of 30% H2O2 + 800 mL FW, and 4 g sodium dodecyl sulfate (SDS) + 800 mL FW], and saltwater (SW) treatments (800 mL SW, 40 mL of 95% alcohol + 800 mL SW, 40 mL of 30% H2O2 + 800 mL SW, and 4 g SDS + 800 mL SW) at 25 °C for 60 days. The predominant MFs disposed from SFM were transparent and sized between 1.0 to &lt; 0.5 mm. The mean highest amount of MFs observed was 4,911.3 (1-day) and 6,180.24 (30-day) in sodium dodecyl sulfate (SDS) mixed with SW, and 7,269.7 (60-day) in SDS with FW. The greatest number of MFs released per day was 275 (SDS in SW), followed by 193 (SDS in FW). The results indicated that if different kinds of water are mixed with detergent (SDS), it could accelerate the disposal of MP, whereas SW has considerably higher ability to release more MFs in a shorter time period compared to FW. Furthermore, this study implied that the inappropriate dumping of SFM could unfortunately escalate the preexisting MP pollution in the aquatic environment, which could negatively affect the aquatic living beings.

Lakes with or without urbanization along their coasts had similar level of microplastic contamination, but significant differences were seen between sampling methods

The influence of sampling method on microplastic (MP) quantification and the impact of population density on the levels of MP contamination in surface waters from Patagonian lakes were investigated. Six lakes located in Northern Patagonia (Argentina) were studied using two different sampling protocols widely reported in the literature: water collected in glass bottles vs. water collected using a 50 μm mesh size net. To assess the influence of population density on MP contamination, lakes with urbanization at shores (Nahuel Huapi, Gutierrez and Moreno) and lakes without urbanization on their shores (Espejo, Espejo Chico and Mascardi) were considered. We identified contamination with secondary MP at all the freshwater lakes studied, with predominance (>90 %) of textile-based microfibers (MF). Remarkably the levels of contamination were similar in all the lakes, independently of whether they were impacted by urbanization along their coasts or not, which supports the notion that there is atmospheric transport of MP. The greatest variability found was among sampling methods, with differences above of three orders magnitude. Samples collected directly in 1-l bottles had an average of 5257 MP/m3 in comparison to 1.57 MP/m3 in the samples that were collected with a 50 μm net. Interestingly, Nahuel Huapi lake samples collected with bottles where the WWTP discharges effluents were significantly more contaminated (SD 9400 ± 4351 MP/MF per m3) than samples collected 5 km west of the plant (2100 ± 1197 MP/MF per m3). Results highlight the significance of textile microfibers as microplastic contaminants of freshwater, and the need to address mesh size when looking for textile microfibers and to develop standardized sampling protocols to make studies on freshwater MF contamination comparable.

Controlling orientation, polymorphism, and crystallinity in thin films of poly(lactic‐acid) homopolymer and stereocomplex aligned by high temperature rubbing

AbstractHigh temperature rubbing is a fast and low‐cost method that can align semi‐crystalline polymers such as poly(lactic acid) (PLA) by application of a shear‐force via a rotating cylinder covered with a microfiber cloth on a thin film maintained at high temperature. A multi technique approach uncovers the role of rubbing temperature and film thickness on the PLA thin film structure. Both poly(l‐lactic acid) (PLLA) and the stereo‐complex (SC‐PLA) can be readily aligned by high temperature rubbing. The rubbing temperature TR and the film thickness are the key parameters that control polymorphism, in‐plane orientation, crystallinity and contact plane of the polymer crystals. Rubbing PLLA films in the range 80–140°C affords different aligned polymorphs (mesophase, α′, α′ + α mixtures and pure α phase) depending on the rubbing temperature. Pure α form of PLLA with 53% crystallinity is obtained at TR = 140°C whereas pure oriented crystalline SC‐PLA films are obtained by rubbing at 200°C.

Effects of microfiber exposure on medaka (Oryzias latipes): Oxidative stress, cell damage, and mortality

Fiber-type microplastics are major anthropogenic contaminants of marine environments. They are released mainly during cloth washing and are discharged from wastewater treatment plants into aquatic environments. This study aimed to evaluate whether microfiber exposure causes oxidative stress and cell damage in medaka (Oryzias latipes Temminck and Schlegel 1846). Fish were exposed to one of two different concentrations (500 and 1000 fibers/L) of a polyester-based microfiber (MF) for 21 days, and the degree of cell damage and changes in expression of antioxidant enzymes were investigated. Fish survival decreased with increasing concentrations of MF. The expression levels of superoxide dismutase (SOD) and catalase (CAT) increased in MF-exposed groups compared to those in the control. SOD activity increased compared to the control group, and MF exposure induced a significant increase in both SOD activity and mRNA expression over time. CAT mRNA expression increased from day 10 onwards following exposure. Plasma malondialdehyde content increased significantly on day 7 of exposure in the 1000 fiber/L group and on day 10 in the 500 fiber/L group. Caspase-3 mRNA expression significantly increased until day 10 of exposure. A terminal transferase dUTP nick end labeling assay confirmed increased apoptosis, and a comet assay demonstrated that higher DNA damage occurred in response to increased MF concentration and exposure time. In conclusion, we confirmed that MF exposure affects antioxidant reactions in fish, thus inducing oxidative stress, apoptosis, and DNA damage. In addition, a comprehensive understanding of MF pollution in aquatic systems is urgently required.

Evaluation of the coagulation properties of magnesium hydroxide for removal combined contamination of reactive dyes and microfibers.

Microfibers are a new type of pollutants that are widely distributed in water bodies. And the simultaneous removal of pollutants in water is popular research in the field of water treatment. In this study, magnesium hydroxide was used as coagulant to investigate the performance and mechanism of coagulation and removal of dyes (reactive orange) and microfibers (MFs). The presence of dyestuff in the composite system promoted the removal of microfibers, and the maximum removal efficiency of both could reach 95.55% and 95.35%. The coagulation mechanism was explored by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and zeta potential. The removal of reactive orange and microfibers relied on electrical neutralization, sweep flocculation, and adsorption mechanisms. Turbidity can enhance the removal efficiency of both. Boosting the rotational speed can increase the removal efficiency of microfibers. This study provides an important theoretical support for an in-depth understanding of the characteristics and mechanisms of coagulation for the removal of complex pollutants from printing and dyeing wastewater.

ISOLATION OF MICROFIBERS IN THE PROCESSING OF POLYAMIDE FABRICS

In recent years, the problem of the release of polymer microparticles (the so-called microplastics) from textile products has been extensively investigated. The main reason of the release of a large number of plastic microfibers is considered to be machine washing of synthetic clothing. However, approaches aimed at reducing the amounts of detached microfibers (MFs) differ significantly. This paper reviews the existing approaches, presents a method for processing polyamide fabrics with a chitosan solution, and describes the experiments that confirm the feasibility of the proposed method. The formation of a chitosan film on the surface of polyamide fibers was evidenced with the results of scanning electron microscopy. The authors have shown that fabric surface treatment with a 1 % chitosan solution reduces the amount of microfibers released during washing by  60 %. A fluorescent analysis demonstrated that mechanical processing of polyamide fabrics with a higher surface density is associated with a release of a smaller number of microfibers (358 ± 24) MF/g as compared to less dense fabrics (533 ± 16) MF/g. The results obtained in the present study can be used in the development of a standard method for quantifying the amount of synthetic microfibers shed from textile materials during their washing.

Kitchen cloths: Consumer practices, drying properties and bacterial growth and survival

Kitchen cloths have an important role in maintaining kitchen surfaces hygienically clean but may also act as vehicles for cross contamination of pathogens from food spills to hands and other foods. The aim of the present study was to map consumer practices across Europe and identify main factors that may contribute to unsafe use of kitchen cloths, such as type of cloth and storage practices. Consumer practices related to cloths were investigated in a web-based survey (N = 2394), while drying properties and growth and survival of Salmonella , Campylobacter and non-pathogenic food associated bacteria in inoculated cloths were studied in laboratory tests mimicking consumer practices. Among consumers in six European countries, cotton and microfiber cloths were reported to be the most used cloth types for cleaning food preparation areas and wiping up spills. . Fifty-seven percent of the consumers reportedly hang the cloth to dry after use. A large majority (72%) changed their cloths at regular times, with an average reported frequency of every 6 days. Large variations in water absorption (63–201 g) and drying rate (31.8–99.8% water loss after 4.5 hours ) among 17 types of commercially available cloths were found. Hanged up cloths dried faster than cloths stored crumpled as balls. Salmonella multiplied in all types of new cloths that were not hung to dry (crumpled), but about 3 log reduction or more were found after hanging cloths to dry for 24 hours. For cloths collected from consumers, growth of inoculated Salmonella was not observed, but hanging the cloths resulted in more than 3 log reduction in numbers. A large variation in survival of Campylobacter was found depending on the type of cloth, but more than 5 log reduction was found after 24 hours in all hanging cloths. A polypropylene and a viscose cloth with low water uptake and fast drying appeared to be the safest choice with a rapid reduction of both pathogens when hung (respectively 2 log and >6 log reduction for Salmonella and Campylobacter after 4.5 hours) and reduction of Campylobacter when stored crumpled. The least safe cloth regarding pathogen growth and survival was a knitted cotton cloth with high water uptake and slow drying. There was no systematic difference in growth and survival of bacteria between microfiber cloths and cloths of other materials, nor between cloths with and without antimicrobial compounds. The present study shows that 16% of consumers have practices that would allow pathogens to contaminate, grow and survive in cloths until the next use. Touching and using these cloths can lead to contamination of hands and food contact surfaces, and potentially to ingestion of pathogens. Consumers should be advised to change cloths after using them for meat spills, but also to choose cloths that dry fast and keep them hanging to dry between use. • Cloths commonly used for cleaning food preparation areas. • Large variation in drying rate between cloths. • Salmonella grows in humid cloths. • Less survival of pathogens in hanging cloths.

Vibrio spp and other potential pathogenic bacteria associated to microfibers in the North-Western Mediterranean Sea.

Microfibers, whether synthetic or natural, have increased dramatically in the environment, becoming the most common type of particles in the ocean, and exposing aquatic organisms to multiple negative impacts. Using an approach combining morphology (scanning electron microscopy-SEM) and molecular taxonomy (High-Throughput DNA Sequencing- HTS), we investigated the bacterial composition from floating microfibers (MFs) collected in the northwestern Mediterranean Sea. The average number of bacteria in 100 μm2 on the surface of a fiber is 8 ± 5.9 cells; by extrapolating it to a whole fiber, this represents 2663 ± 1981 bacteria/fiber. Attached bacterial communities were dominated by Alteromonadales, Rhodobacterales, and Vibrionales, including the potentially human/animal pathogen Vibrio parahaemolyticus. This study reveals a high rate of bacterial colonization on MFs, and shows that these particles can host numerous bacterial species, including putative pathogens. Even if we cannot confirm its pathogenicity based only on the taxonomy, this is the first description of such pathogenic Vibrio living attached to MFs in the Mediterranean Sea. The identification of MFs colonizers is valuable in assessing health risks, as their presence can be a threat to bathing and seafood consumption. Considering that MFs can serve as vector for potentially pathogenic microorganisms and other pollutants throughout the ocean, this type of pollution can have both ecological and economic consequences.

Effect of temperature, holding time and gas atmospheres in the synthesis and evolution of polymer-derived nanoceramics: A pyrometallurgical approach to precision nanorecycling of multiphase microplastics

Microplastics (MPs) are a critical type of persistent anthropogenic micro debris reported globally as ubiquitous to urban and non-urban settings. These complex micropollutants are of great concern given their contribution to severe environmental impact across ecosystems, confirmed as hazardous to the soil, biota, as well as to human health. From the materials perspective MPs are a heterogeneous mixture constituted predominantly by multiphase synthetic and natural polymers in the form of fibres, fragments and particles, from which microfibers (MFs) account for ∼90% of the global MPs pollution. The recovery and batch recycling of MFs is still in early stages remaining operationally, technologically and economically challenging. Therefore, the objective of the present study is the valorization of MFs examining its feasibility as alternative precursor for the green synthesis of engineered polymer-derived nanoceramics. The strategic approach targets the precision nanorecycling via selective high-temperature fast carbothermal method, which to the best of our knowledge is first reported for MFs. The effect of temperature, retention time, and gas atmospheres on the output products was investigated in the temperature range of 1300 −1600 °C, under controlled argon and nitrogen flow. The compositional, structural evolutions, morphological and textural properties of the output products are discussed. The experimental results indicated the precursor contained an inherent compositional advantage, in which silica-containing polymers along with embedded trace metals favoured the evolution of the organic carbon into mesoporous graphitic carbon, as well as the development of self-assembled self-catalytic one-dimensional SiC crystalline nanostructures, in both atmosphere systems. Specifically, the N-doped nanoneedles demonstrated higher thermal and chemical stability providing a suitable candidate for harsh environment applications. The relevance and significance of this proposal lays in the advancement of MFs recovery via precision nanorecycling of carbon and silica at a molecular level for the synthesis of high-end engineered outputs.

New insights into the adsorption behavior of thiacloprid at the microfibers/water interface: Role of humic acid

Dissolved organic matter regulates the interaction between microplastics (MPs) and organic pollutants. Here, this paper investigated the effect and mechanism of humic acid (HA) on the adsorption behavior of thiacloprid at two microfibers (MFs)/water interface, and compared the differences in the performance of MFs and pure MPs. The results showed that 10 mg L−1 HA decreased the adsorption capacity and the partition coefficient KD of thiacloprid on MFs and pure MPs. Spectral analysis showed that HA could form hydrogen bonds and van der Waals forces with both MPs and thiacloprid, ultimately affecting the adsorption behavior of thiacloprid at MPs/water interface via competitive adsorption and bridging effect. Furthermore, two-dimensional correlation spectroscopy demonstrated that thiacloprid was preferentially adsorbed onto MPs compared with HA. Finally, density functional theory calculation demonstrated that phenolic-OH, –COOH, and alcoholic-OH played critical roles in competing adsorption and bridging effect. This study offers a theoretical foundation for a better comprehension of the adsorption behavior of organic pollutants at the MPs/water interface.

Microfiber-loaded bacterial community in indoor fallout and air-conditioner filter dust

Microfibers (MFs) are widely existed in indoor air; however, characteristic of microbiota on MFs is largely unknown. In this study, air-borne MFs were collected from fallout or air-conditioner (AC) filter dust in three types of indoor space including living room, dormitory and office. Both plastic and natural MFs were identified by Fourier transform infrared spectroscopy. Ultramicroscopic observation showed dense biofilms adhering on surfaces of MFs. Fallout MFs contained more bacteria but fewer fungi than MFs from AC filter dust. MFs-loaded bacteria were of highest abundance in living rooms, following dormitories and offices. Bacterial community and its diversity were further analyzed by 16S rRNA High-throughput sequencing. Up to 4540 of bacterium OTUs were shared in these MFs samples, unique OTUs in fallout and AC filter samples accounting for 26.3 % and 25.7 % of the total. Compared to MFs fallout, AC filter MFs contained more species of pathogenic bacteria, such as Betaproteobacteriales and Ralstonia, with obviously different β-diversity between two groups. Phenotypic analysis showed that fallout and AC filter MFs bacteria presented high index values of film formation, oxidative stress tolerance and potential pathogenicity. Overall, these results suggest that abundant bacteria including pathogen can be loaded on MFs, and would pose health risks through delivery of indoor MFs.