Journal of Polymers and the Environment最新文献

Modified adsorption of gel materials has received wide attention, but enhancing the efficiency and rate of phosphate adsorption by gel materials still needs further exploration. In this study, Fe(III) was doped into sodium alginate-based gel beads to analyze the principle of its action in enhancing the adsorption performance of the gel beads by revealing the role of Fe(III) cross-linking. Meanwhile, the adsorption mechanism of phosphate removal was explored. The addition of Fe(III) displaces part of the cross-linking between Ca(II) and sodium alginate, forming a solid monodentate covalent coordination structure with the carboxyl group of sodium alginate. 2% iron doping concentration forms better lattice support and pore structure so that its specific surface area increases and has abundant adsorption sites. Compared with the gel beads without iron, the gel beads with 2% iron realize a 4-fold increase in phosphate adsorption. With a high adsorption efficiency, the adsorption reaction can reach equilibrium in 2 h. The adsorption is mainly monolayer chemisorption, and the maximum adsorption capacity can reach 84.08 mgPO₄³⁻-P/g. Compared with calcium alginate, iron salts are preferentially and rapidly adsorbed to phosphate, followed by the formation of modified phosphates and iron hydrogen phosphate salts and the formation of the corresponding iron salts. The modified gel materials can remove phosphate efficiently in water treatment and provide a reference for the preparation of gel polymerization materials and phosphate adsorption studies.

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Biodegradable aerogels possessing flexibility and high strength are appealing for applications in construction, acoustic and thermal insulation. However, their susceptibility to flammability presents a significant challenge. Enhancing the flame retardancy of these aerogels has been a prominent focus of research, with the widespread use of inorganic fillers and layered materials for this purpose. In the current study, our objective is to fabricate cellulose nanofiber aerogels characterized by low density, exceptional flame retardancy, high mechanical properties, and thermal insulation. This is achieved through the cross-linking of melamine and formaldehyde under aqueous conditions using an eco-friendly freeze-drying process, followed by post-curing. The resulting aerogels demonstrate flexibility, effective sound absorption within the mid-frequency range, and outstanding flame retardancy (Limiting Oxygen Index ∼33%) with a non-flammable behaviour. The thermal conductivity of the fabricated melamine formaldehyde-modified cellulose nanofiber (MF-CNF) aerogels was 0.064 ± 0.014 W/m.K. MF-CNF aerogels exhibited a Time to Ignition (TTI) of 489 s, whereas pristine CNF aerogels only have 3 s. This improvement was attributed to the concurrent reductions in both the Peak Heat Release Rate (PHRR) and Fire Growth Rate (FIGRA) of MF-CNF aerogels. The straightforward melamine formaldehyde modification of CNF aerogels enhances their mechanical strength as well as fire resistance. These sustainable multifunctional aerogels hold great potential for a variety of real-life applications in the realm of buildings and its structures for ensuring fire safety and sound insulation.

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The mechanical responses during loading, unloading, and reloading cyclic tensile tests of a tubular blown film of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) are studied. Although the stress–strain curve recorded during the initial stretching process is typical for a crystalline polymer, the stretched film behaves like a rubber during the reloading process; that is, low modulus with a small residual strain after unloading. Furthermore, the stress–strain curves during the reloading process are an inverted “S” shape. During the first stretching process of the polymer film, small crystals are destroyed without reorganization into a crystalline structure, leading to the observed decrease of crystallinity. In contrast, well-developed crystals that orient to the machine direction of the film do not disappear during the first stretching and act as crosslink points during reloading. As a result, a rubber-like response is detected. This mechanical response during reloading is considerably different from those of conventional crystalline plastics such as polyethylene and polypropylene.

The Chinese herbal medicine industry plays a crucial role globally, providing traditional remedies and significantly contributing to healthcare. Disease prevention and control in Chinese herbal medicine face unique challenges distinct from conventional plant protection methods. The distinctive requirements for disease control add complexity to disease management, necessitating specialized approaches. In this study, we developed a bio-based hydrogel (CSA-gel) using a straightforward procedure designed for the sustained release of azoxystrobin for soil disinfection with the aim of preventing fungal diseases in Chinese herbal medicine. The synthesized hydrogel was characterized using FTIR, zeta potential measurement, cryo-TEM, SEM, and elemental analysis. CSA-gel demonstrated a release duration of azoxystrobin for over 14 days, maintaining high antifungal activity throughout the entire release period. Additionally, CSA-gel exhibited the ability to release a significant quantity of calcium ions during pesticide release, fostering plant growth and enhancing plant disease resistance. The use of CSA-gel is anticipated to decrease both how often and how much pesticide is needed, highlighting the significance of our research in improving sustainable disease control in traditional Chinese herbal medicine farming.

Conventional plastics pose environmental threats due to their non-biodegradable nature and their reliability on fossil resources, leading to the exploration of sustainable alternatives. In this sense, biodegradable bioplastics derived from renewable resources offer a promising solution to mitigate ecological impacts. This study focuses on the combination of extrusion and injection molding for the development of rice bran-based bioplastics. Being a by-product from the rice industry rich in starches and proteins, rice bran is an abundant and non-expensive resource that contributes to an enhanced waste management and represents a step forward in integrating the principles of a circular economy. This study delves into the optimization of processing conditions through a Design of Experiment approach. For this purpose, the number of extrusion steps, cylinder and mold temperatures, and injection pressure were investigated. The results showed that two extrusion steps led to a significant increase of approximately 22.8% in Young’s modulus and 37.5% in tensile strength compared to a single extrusion cycle. This enhancement was attributed to the facilitation of starch gelatinization and biopolymer-plasticizer interactions (achieving thermoplastic starch and protein plasticization). Similarly, manipulation of injection temperatures and pressure had notable effects on tensile properties, highlighting the complex interplay between processing parameters. In particular, when using cylinder and mold temperatures of 110 °C and 180 °C, respectively, along with 800 bar, it was possible to achieve a further enhancement in tensile properties, with an increase of 97.1% in Young’s modulus and over 100% in tensile strength. Overall, this research underscores the importance of understanding the relationship between processing conditions and biopolymer interactions for bioplastic production.

Biological process to extract chitin from crustacean wastes may be an interesting and safe alternative than chemical process. The inoculation of lactic acid bacteria is an environmentally-friendly strategy to extract chitin especially if low-cost raw materials are utilized as fermentation substrates. The deacetylation of chitin by chemical or biological processes results in an important and multifaceted biopolymer, the chitosan, with a range of applications in diverse areas. A two-step process consisting of lactic fermentation (by Lactiplantibacillus plantarum) of shrimp wastes and chemical deacetylation of chitin to obtain chitosan was here proposed focusing on the replacement of the semi-synthetic medium MRS (de Man–Rogosa–Sharpe) by sugarcane molasses, on the variation in the concentration and drying of shrimp wastes in the fermentation step, and increased deacetylation times of chitin. Chitosan was characterized and assayed for antimicrobial activity, microsphere and film-forming properties. Diluted molasses containing 150 g/L of total reducing sugars and supplemented with 12 g/L yeast extract is a viable and cost-effective alternative to MRS to recover chitin from oven-dried shrimp wastes at a concentration of 5% w/v. A low molecular weight chitosan (95.3 kDa) was obtained after a 2-h chemical deacetylation (79.6% deacetylation degree). Molasses chitosan exhibited antibacterial and antifungal activities. Chitosan rough microspheres capable of loading antibiotic (monensin), and transparent and homogenous films were also obtained. The complete flow of operations until obtaining chitosan with considerable yields is here presented, also demonstrating the intrinsic properties of this polymer. The molasses chitosan, utilized without purification, has potential application in industry and agriculture as a biomaterial.

Utilizing xanthan gum, a biodegradable polymer, in enhanced oil recovery (EOR) is imperative wherever there is a need for innovation in oil production that is both cost-effective and environmentally friendly. Xanthan, chosen for its natural sourcing, availability, controllability, eco-friendliness, and biodegradability, proves resilient against harsh reservoir conditions owing to its rigid structure and elongated polysaccharide chains. This study investigates two modified xanthan gum composites, achieved by grafting with synthetic vinyl monomers through emulsified polymerization. Spectroscopic characterization using FTIR and ¹H-NMR, along with surface morphology analysis via atomic force microscopy (AFM) and thermal behavior screening through TGA analysis, elucidates the properties of these modified composites. Rheological behavior under reservoir conditions, including stress scanning and viscosity/shear rate dependency, was evaluated. Material modeling with the Materials Studio program simulated the equilibrium adsorption of xanthan and modified biopolymer chains on SiO₂-quartz crystal to assess wettability alteration. Simulation results indicate that XG-g-AM, MMA&TEVS exhibit greater stability and surface coverage with more negative electrostatic energies compared to XG and XG-g-AM&MMA. The laboratory runs on a sandstone-packed model to identify the disclosed XG-g-AM&MMA and XG-g-AM, MMA&TEVS biopolymers as promising EOR candidates and wettability modifiers in challenging sandstone reservoirs, as per experimental outcomes.

Recent studies have reported the biodegradation of polyethylene waste in the gut of beeswax-eating insect larvae of Galleria mellonella and Achroia grisella. In this study we examined the life cycle stages and duration of each stage of three common beeswax eating honeybee pests (G. mellonella, A. grisella, and Uloma sp.) from Apis cerana indica colonies under laboratory conditions. The insect larvae of the three species were provided with beeswax, low density polyethylene (PE), or expanded polystyrene (PS) foam diet. The weight loss of beeswax, PE, and PS feed as a function of time caused by the consumption of the three insect larvae were measured. Additionally, the effects of beeswax, PE, and PS feed on the development and survival of the three insect larvae were studied. The beeswax-feeding insects G. mellonella, A. grisella, and Uloma sp. completed their life cycles with average durations of 62 ± 2.1 days, 49 ± 3.6 days, 202 ± 3.2 days, respectively. The G. mellonella, A. grisella, and Uloma sp. larvae ate and digested beeswax, PE, and PS. The insect larvae were found to survive on plastic diets (PE and PS) but a decreased body mass was observed compared to that of beeswax-eating conspecifics. The insect larvae that eat and digest beeswax and plastics could help to eliminate global pollution from recalcitrant plastic wastes.

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