Hydrolytic degradation and biodegradation of polylactic acid electrospun fibers.

Increased use of bioplastics, such as polylactic acid (PLA), helps in reducing greenhouse gas emissions, decreases energy consumption and lowers pollution, but its degradation efficiency has much room for improvement. The degradation rate of electrospun PLA fibers of varying diameters ranging from 0.15 to 1.33 µm is measured during hydrolytic degradation under different pH from 5.5 to 10, and during aerobic biodegradation in seawater supplemented with activated sewage sludge. In hydrolytic conditions, varying PLA fiber diameter had significant influence over percentage weight loss (W%L), where faster degradation was achieved for PLA fibers with smaller diameter. W%L was greatest for PLA-5 > PLA-12 > PLA-16 > PLA-20, with average W%L at 30.7%, 27.8%, 17.2% and 14.3% respectively. While different pH environment does not have a significant influence on PLA degradation, with W%L only slightly higher for basic environments. Similarly biodegradation displayed faster degradation for small diameter fibers with PLA-5 attaining the highest degree of biodegradation at 22.8% after 90 days. Hydrolytic degradation resulted in no significant structural change, while biodegradation resulted in significant hydroxyl end capping products on the PLA surface. Scanning electron microscopy (SEM) imaging of degraded PLA fibers showed a deteriorated morphology of PLA-5 and PLA-12 fibers with increased adhesion structures and irregularly shaped fibers, while a largely unmodified morphology for PLA-16 and PLA-20.

Unveiling the Microfiber Release Footprint: Guiding Control Strategies in the Textile Production Industry.

Microplastic fibers from textiles have been known to significantly contribute to marine microplastic pollution. However, little is known about the microfiber formation and discharge during textile production. In this study, we have quantified microfiber emissions from one large and representative textile factory during different stages, spanning seven different materials, including cotton, polyester, and blended fabrics, to further guide control strategies. Wet-processing steps released up to 25 times more microfibers than home laundering, with dyeing contributing to 95.0% of the total emissions. Microfiber release could be reduced by using white coloring, a lower dyeing temperature, and a shorter dyeing duration. Thinner, denser yarns increased microfiber pollution, whereas using tightly twisted fibers mitigated release. Globally, wet textile processing potentially produced 6.4 kt of microfibers in 2020, with China, India, and the US as significant contributors. The study underlined the environmental impact of textile production and the need for mitigation strategies, particularly in dyeing processes and fiber choice. In addition, no significant difference was observed between the virgin polyesters and the used ones. Replacing virgin fibers with recycled fibers in polyester fabrics, due to their increasing consumption, might offer another potential solution. The findings highlighted the substantial impact of textile production on microfiber released into the environment, and optimization of material selection, knitting technologies, production processing, and recycled materials could be effective mitigation strategies.

Oligomer nanoparticle release from polylactic acid plastics catalysed by gut enzymes triggers acute inflammation.

The health risks of exposure to 'eco-friendly' biodegradable plastics of anthropogenic origin and their effects on the gastrointestinal tract are largely unknown. Here we demonstrate that the enzymatic hydrolysis of polylactic acid microplastics generated nanoplastic particles by competing for triglyceride-degrading lipase during gastrointestinal processes. Nanoparticle oligomers were formed by hydrophobically driven self-aggregation. In a mouse model, polylactic acid oligomers and their nanoparticles bioaccumulated in the liver, intestine and brain. Hydrolysed oligomers caused intestinal damage and acute inflammation. A large-scale pharmacophore model revealed that oligomers interacted with matrix metallopeptidase 12. Mechanistically, high binding affinity (Kd = 13.3 µmol l-1) of oligomers to the catalytic zinc-ion finger domain led to matrix metallopeptidase 12 inactivation, which might mediate the adverse bowel inflammatory effects after exposure to polylactic acid oligomers. Biodegradable plastics are considered to be a solution to address environmental plastic pollution. Thus, understanding the gastrointestinal fates and toxicities of bioplastics will provide insights into potential health risks.

Insight into the oxidation of phenolic pollutants by enhanced permanganate with biochar: The role of high-valent manganese intermediate species.

This work demonstrated that the oxidation of phenolic pollutants by permanganate (KMnO4) was effectively enhanced by a commercial biochar. Detailed characterization data indicated that the biochar contains porous structures, amounts of defective sites and abundant redox-active groups. In the presence of biochar, the degradation efficiency of 4-nitrophenol by KMnO4 surged from 5% to 92% in 180 min, up to 37.8% of total organic carbon (TOC) was removed. Meanwhile, acute toxicity of 4-nitrophenol was greatly reduced. Through analyzing oxidation products of triclosan (TCS) and using methyl phenyl sulfoxide (PMSO) as a chemical probe, high-valent Mn intermediates (i.e. Mn(VI)/Mn(V)) were proved to be the dominant oxidant in the KMnO4/biochar system. Quantitative structure-activity relationships (QSARs) were established between oxidation rate constants of various substituted phenols and classical descriptor variables (i.e., Hammett constant σ+). KMnO4/biochar was found to be less selective to the substituent variation of phenolic compounds compared with O3, K2FeO4, ClO2 and persulfate/carbon nanotube (PDS/CNT). This work provided a novel catalytic oxidation technology for eliminating phenolic compounds, and improved insights into the mechanistic study of the KMnO4-based oxidation process.

Deca-BDE and alternative halogenated flame retardants in a wastewater treatment plant in Harbin (2009-2016): Occurrence, temporal trends, seasonal variation, and fate.

This study is the first attempt to comprehensively investigate deca-BDE and alternative flame retardants in a wastewater treatment plant in such a long term in China (2009-2016). Influent, effluent and sludge samples were collected. The mean concentration of deca-BDE, Σ19NBFRs and ΣDPs in influent were 311.5, 76.0 and 1.4ng/L, respectively, which were at the low end of the global range. The levels of deca-BDE, Σ19NBFRs and ΣDPs in effluent were range from 9.5-68.6, 4.1-38.5 and BLD-1.6ng/L, respectively. In sludge samples, the mean concentrations were 406.7, 510.5 and 6.9ng/g dw for deca-BDE, Σ19NBFRs and ΣDPs. The concentration of temporal trends in this study may reflected the release of those compounds. Compared to the beginning year of this study, the usage of deca-BDE was decreased but the usage of total NBFRs and DPs presented sustained increase over the sampling period. There were no significant variation of deca-BDE, NBFRs and DPs in the wastewater treatment plant in Harbin was observed in the four seasons except for NBFRs in influents, which the Σ19NBFRs mean concentration in influents in the summer was statistically significantly higher than that in winter indicating that NBFRs was easier impacted by temperature compared to deca-BDE and DPs. In addition, sorption and accumulation to sludge was the major removal mechanism for those compounds, accounting for 73.3% to 89.0%.

The occurrence and fate of PAHs over multiple years in a wastewater treatment plant of Harbin, Northeast China.

The occurrence and fate of polycyclic aromatic hydrocarbons (PAHs) were investigated in wastewater, sludge and surrounding air from the wastewater treatment plant (WWTP) in Harbin, Northeast China. The concentration of total PAHs in the influent, effluent and sludge were 4080ng/L, 864ng/L and 8200ng/gdw, respectively. The total concentration of PAHs showed a trend of first rising, and then decreasing over years in the influent, effluent and sludge, which was in agreement with the usage of coal and oil in Harbin. The level of PAHs was 26-560ng/m3 in air from site 1 (the top of the A/O tank), 62-608ng/m3 in air from site 2 (the vicinity of the WWTP) and 61-686ng/m3 in air from site 3 (the urban district of Harbin). In the influent and effluent, the mean concentration of PAHs followed the sequence of summer>winter>autumn>spring, while the sequence was winter>summer>autumn>spring in sludge and air. Rainfall may be the main reason for higher contamination in summer. Coal fired central heating and indoor dust may be reasons for higher PAHs in winter. The mean removal efficiency of total PAHs was approximately 85% (20% of which was adsorbed onto sludge, and 65% volatilized into air or degraded by biodegradation), and 15% of PAHs were discharged through the effluent. There was approximately 6240kg of PAHs imported into the WWTP every year, 1005kg discharged into the Songhua River through the effluent, and 327kg absorbed onto sludge and the rest was degraded or volatilized into air. PCA was applied to identify the sources of PAHs for both heating and non-heating seasons. In general, coal combustion was the main source of PAHs during the heating season and vehicle exhaust was the main source of PAHs during the non-heating season.