Journal of Polymers and the Environment最新文献

This study evaluates the photocatalytic performance of two innovative nanocomposites, Fe₃O₄/chitosan and Fe₃O₄/phthalhydrazide/chitosan, for the degradation of tetracycline (TC) under visible light irradiation. The synthesized photocatalysts were characterized using Fourier-transform infrared (FTIR) spectroscopy, X-Ray diffraction (XRD), field emission scanning electron microscopy (FESEM), UV-Vis spectroscopy, and energy-dispersive X-Ray spectroscopy (EDS) to confirm their structural, morphological, optical, and elemental properties. These analyses provide insights into the role of phthalhydrazide in enhancing photocatalytic activity. The isoelectric point (pH_iep) of the Fe₃O₄/phthalhydrazide/chitosan composite was found to be 9.2, indicating favorable electrostatic stability. Photocatalytic tests demonstrated that the Fe₃O₄/phthalhydrazide/chitosan composite exhibited significantly superior degradation efficiency, achieving 93% TC removal after 120 min, compared to 53% for the Fe₃O₄/chitosan composite. The effect of catalyst dosage on photocatalytic activity was also investigated, revealing optimal performance at concentrations between 0.01 g and 0.02 g. Furthermore, the influence of TC concentration on degradation efficiency was examined, showing a decline in photocatalytic activity at higher TC concentrations due to competitive adsorption on active sites. The optimal concentration for achieving the highest photocatalytic activity appears to be around 10 to 20 ppm. pH studies showed in alkaline media about 12 the photodegradation efficiency is reached to about 100% due to enhancing the hydroxyl radicals and surface charges of photocatalyst. Mechanistic studies employing scavengers confirmed the involvement of reactive species, providing further insight into the degradation pathways of TC. The incorporation of phthalhydrazide into the Fe₃O₄/chitosan composite significantly enhanced its photocatalytic efficiency, presenting a promising strategy for the environmental remediation of pharmaceutical pollutants. These findings emphasize the critical role of optimizing catalyst design and operational conditions to enhance the effectiveness of photocatalytic processes in wastewater treatment applications.

The increasing demand for sustainable materials has underscored the importance of utilizing polymer waste in various applications. Despite the growing interest in using polyethylene waste for foam production, concerns regarding the mechanical properties of recycled foams present challenges to their reuse, as these properties are critical for foam performance. The mechanical characteristics of foams are closely linked to their cell structure. This study investigates the foaming behavior of irradiated crosslinked virgin and recycled low-density polyethylene by comparing parameters of foam’s cell structure, including foaming degree, cell size distribution, cell density, volume expansion ratio, and foaming rate on a batch scale. Polyethylene foams were produced by melt mixing polyethylene with azodicarbonamide (ADCA) as a blowing agent, followed by irradiation and hot pressing for foaming. The analysis of the produced foams focused on gel content and structural, thermal, and mechanical properties. Results indicate that an absorbed dose of 50 kGy optimizes both virgin and recycled foams, enhancing their expansion and mechanical stability. At this dosage, both types exhibit a closed microcellular structure with a maximum cell density of 10⁵ cells/cm³. The results reveal that while tensile strength decreases with increasing absorbed doses, elongation at break significantly increases. This indicates that recycled polyethylene foams offer enhanced flexibility despite the reduced strength, making them advantageous for applications requiring deformation resistance without failure.

Herein high-strength composites are prepared from elemental sulfur, sunflower oil, and wastewater sludge. Fats extracted from dissolved air flotation (DAF) solids were reacted with elemental sulfur to yield composite DAFS (10 wt% DAF fats and 90 wt% sulfur). Additional composites were prepared from DAF fat, sunflower oil and sulfur to give SunDAF_x (x = wt% sulfur, varied from 85–90%). The composites were characterized by spectroscopic, thermal, and mechanical methods. FT-IR spectra revealed a notable peak at 798 cm^–1 indicating a C–S stretch in DAFS, SunDAF₉₀, and SunDAF₈₅ indicating successful crosslinking of polymeric sulfur with olefin units. SEM/EDX analysis revealed homogenous distribution of carbon, oxygen, and sulfur in SunDAF₉₀ and SunDAF₈₅. The percent crystallinity exhibited by DAFS (37%), SunDAF₉₀ (39%), and SunDAF₈₅ (45%) was observed to be slightly lower than that of previous composites prepared from elemental sulfur and fats and oils. DAFS and SunDAF_x displayed compressive strengths (26.4–38.7 MPa) of up to 227% above that required (17 MPa) of ordinary Portland cement for residential building foundations. The composite decomposition temperatures ranged from 211 to 219 °C, with glass transition temperatures of − 37 °C to − 39 °C. These composites thus provide a potential route to reclaim wastewater organics for use in value-added structural materials having mechanical properties competitive with those of commercial products.

The global water scarcity crisis has been exacerbated by the increasing demand for clean water and water pollution caused by the persistent release of pharmaceuticals such as ciprofloxasin, into water systems. The biodegradation and adsorption potential of CIP is crucial for its elimination in wastewater treatment systems. However conventional methods in wastewater treatment plant (WWTP) often struggle to efficiently eliminate of CIP from water due to its chemically stability and nonbiodegradability. Many researchers observed that CIP was not biodegraded even after 48 days in municipal WWTP, therefor no CIP removal occurred. The objective of this study was to investigate adsorption potential of CIP using a designed electrospun nanofiber. Within the scope of this purpose, we prepared electrospun acrylic acid (AAc)-based hydrogels modified with n-hexadecyl acrylate (C16A) for the first time and evaluated their efficacy in removing CIP from water. Our results show that the desired fiber size and surface smoothness can be obtained in the electrospun hydrogel containing 35 mol% of C16A. As a result, the AAc-based hydrogel nanofiber containing 35 mol% C16A exhibited superior adsorption properties. The adsorption efficiency of the hydrogel for CIP removal from aqueous medium was as high as 98% under equilibrium conditions. The adsorption process was found to follow the pseudo-second-order model, which suggests chemisorption as the dominant mechanism. Isothermal analysis showed that the adsorption fit well with the Langmuir model, suggesting single layer adsorption on a uniform surface. These results highlight the potential of AAc-based hydrogels for the sustainable removal of pharmaceuticals from wastewater, addressing a critical need in environmental contaminant management.

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World population growth associated with unbridled consumption have led to notable increases in the use of petroleum-based plastics. Biodegradable polymers produced from sustainable and low-cost raw materials have been emerging as a key solution. The objective of this work was to obtain a polymer of microbial origin from an alternative and renewable source. Bacterial Polyhydroxybutyrate (PHB-B) was produced by submerged culture of Cupriavidus necator using commercial sugarcane molasses (CSM) as a renewable substrate. A 2² factorial experimental design with three central point replications was conducted to identify the most favorable culture conditions. The 15 g.L⁻¹ concentration of reducing sugar (RS) obtained from the CSM was effective as a carbon source, yielding (under stirring at 180 rpm and 30 °C) a maximum production of 35.70% PHB-B, while presenting the same functional groups and crystal structure as commercial grade Polyhydroxybutyrate (PHB-C). The intensities obtained for the 2933 and 2975 cm⁻¹ bands, suggested that PHB-C presents higher crystallinity than PHB-B. ¹H and ¹³C NMR confirmed the identity of the bacterial biopolymer as Polyhydroxybutyrate. The diffraction peaks were less intense for PHB-B, and the peaks at (021) and (101) coalesced into a single peak at (111). The peak shapes indicated that PHB-B presents smaller and/or less perfect crystals than PHB-C. Considering the observed structural differences, the rigidity and flexibility of the biopolymers may differ. Bacterial PHB was produced using a low-pollution route. This resulted in a product which potentially expands the range of environmentally friendly PHB applications.

Polyurethanes (PUs) are widely used in various industries, but their durability raises significant disposal and environmental concerns. Enzymatic degradation offers a sustainable approach to address these challenges by providing a pathway for PU waste management. This study investigates the enzymatic degradation pathways of PU structures of varying complexity using lipase, protease, peroxidase, and combinations of these enzymes. The focus is on elucidating the mechanisms of degradation and structural changes through structure characterization and thermal analysis techniques. Complementing the experimental analyses, a comprehensive computational study evaluates the interactions between the enzyme and the PU structures. The computational results are then compared with the experimental findings, providing a thorough understanding of these interactions. The findings underscore the potential of enzymatic degradation of PU and the effectiveness of enzyme mixtures, especially the combination of lipase and peroxidase, as well as the synergistic action of all three enzymes. Peroxidase emerges as a highly efficient catalyst for PU degradation, complementing the esterase and amidase enzymes previously studied in this context. The key amino acids that participate in the binding of the enzymes to PUs are also highlighted. This research underscores the promise of enzymatic approaches for environmentally friendly PU recycling.

Over the years, brown algae have been highlighted as valuable natural sources of bioactive polysaccharides. They are known to consist of a number of bioactive polysaccharides, fucoidan being the principal polysaccharide. Fucoidans, a sulphated polysaccharide composed of a fucopyranose backbone and several monosaccharaides have been reported to possess numerous biological activities such as anticancer, antioxidant, antiviral, antithrombotic, and anti-inflammatory properties, thus may confer health benefits to humans. However, the main mechanisms bridging the structural complexity of fucoidans and their biological activity are mostly unexplored. This study aimed to compare the structural features and the antimicrobial properties of the fucoidan extracts isolated from the two brown macroalgae, Fucus vesiculosus and Saccharina latissima, sampled in the littoral zone of the Barents Sea. The physicochemical properties of fucoidans and their polyelectrolyte properties were investigated. The antibacterial activity of fucoidans was evaluated using the disc diffusion method against Bacillus subtilis (gram-positive bacteria), Pseudomonas aeruginosa, and Proteus mirabilis (gram-negative bacteria). It was shown that fucoidans inhibited the growth of both gram-positive and gram-negative microorganisms. At the concentration of 0.25–0.5%, the highest clear inhibition zones were observed for all the studied bacteria. The high antibacterial activity of fucoidans was due to the availability of functional groups and the particle sizes of fucoidan molecules that affect the cell membranes of the bacterial microflora. On the basis of obtaining results, fucoidans were suggested as potential natural and green bactericidal agents to be used by the pharmaceutical, medicine, and food industries.

One of the most challenging features of textile recycling is the widespread use of mixed fibre blends, which hardens the task of effective separation. A mixture of aqueous sodium hydroxide and a cosolvent was applied to a polycotton pre-consumer fabric to promote the chemical separation of polyester (PES) and cotton (CO). The feasibility of reusing the hydrolytic solutions was tested, where dimethyl sulfoxide (DMSO) and 2-propanol allowed the reusage of the hydrolytic solution for up to 3 consecutive cycles when applied to pristine material. The recovery of pure terephthalic acid (TPA), after treatment at 50 °C followed by vacuum filtration, achieved yields ranging from 65 to 69%. No further purification was required in 75% of the tested conditions. Through this environmentally sustainable procedure, a method was proposed that could facilitate the development of a scalable process for the TPA recovery from polycotton textiles. This approach aims to reduce both textile waste production and the need for the de novo synthesis of TPA.