Journal of Polymers and the Environment最新文献

A new polyol derived from gamma-valerolactone with 10 carbon chain and four hydroxyl groups was used in combination with choline chloride for the production of a deep eutectic solvent (DES) employed as plasticizer for chitosan. The polyol estimated boiling point was 340 °C and the glass transition temperature (T_g) was − 6 °C. No crystallization temperature was observed due to the non-symmetric structure of polyol and because it is a mixture of stereoisomers. A eutectic condition was detected in an interval of choline chloride(ChCl)/polyol composition from 2:1 to 1:10. It was observed that only the mixtures with higher ChCl content showed melting points, so the eutectic composition was chosen by the lowest T_g that was obtained by the 1:1 molar ratio mixture, circa − 40 °C. This ChCl/Polyol composition was used to prepare plasticized chitosan film, by hot pressing. The glycerol/choline chloride mixture was also used as DES for comparison purposes. Both DES acted as plasticizer to obtain chitosan thermoplastic films, verified by the significant T_g drop from 165 °C, for unplasticized film, to -2 °C and − 30 °C, for films plasticized with DES based on ChCl-polyol and ChCl-glycerol, respectively. The materials plasticized with ChCl-polyol, showed a decrease in modulus of about 54% and an increase of 455% in elongation compared to ChCl/Glycerol, indicating better plasticization efficiency of the polyol based DES. The use of ChCl/Polyol have opened up a new opportunity for the use of chitosan as a plastic material and the high boiling point of polyol has made it a real and highly stable plasticizer.

Microalgae have emerged as a promising feedstock for biofuel production due to their ability to accumulate significant quantities of lipids. However, efficient extraction of these intracellular lipids remains a critical challenge. This study investigated pulsed electric field (PEF) and ultrasonic treatments for disrupting the robust cell walls of Nannochloropsis microalgae and extracting intracellular oils. A custom PEF setup with corrugated steel electrodes treated Nannochloropsis salina slurries under varying electric field strengths, pulse frequencies, processing times, and biomass concentrations. The Taguchi method optimized PEF parameters to maximize oil yields. Optimal PEF conditions of 20 kV/cm, 400 Hz, 30 min, and 20 g/L facilitated enhanced oil extraction by reversibly electroporating the cells. After PEF treatment, a solvent extraction process using chloroform and methanol recovered the released oils, yielding a maximum of 0.52 g_oil/g_{dry biomass} while consuming 39.6 kJ/kg of energy. Notably, PEF outperformed ultrasonic treatment, achieving higher oil yields with minimal temperature rise that could degrade cellular components. Microscopic observations confirmed oil droplet release and cell membrane permeabilization after PEF, without significant cell debris. The results showcase PEF as an efficient, non-thermal, and environmentally friendly pretreatment approach for extracting oils from robust microalgae like Nannochloropsis, making it viable for microalgae-based biofuel and industrial applications involving oil extraction.

To address the increasing demand for sustainable biomaterials because of the excessive usage of fossil fuel and growing concerns with the environment, a novel biodegradable and environmentally friendly rigid polyurethane foam (RPUF) has been synthesized. These foams are derived from chemically modified soybean oil-based polyol (SBO-polyol) obtained through the formation of oxirane followed by the opening of the oxirane reaction. Polyurethane foam is generally used in construction, furniture, and automobile industries but is highly flammable and releases toxic fumes in combustion. In this study, an efficient synergistic effect of non-halogen flame-retardant (FR) melamine salt, 2-carboxyethyl(phenyl)phosphinic acid melamine salt (CMA) was synthesized from 2-carboxyethyl(phenyl)phosphinic acid (CEPP) and melamine (MA). Fourier transform infrared (FT-IR) spectroscopy characterized the chemical structure of CMA. Three different FRs, MA, melamine cyanurate (MC), and CMA were separately introduced in increasing quantities for the foam preparation to suppress the flame during combustion. The influence of these FRs on the thermal properties, flame retardancy, morphology, physical, and mechanical properties of the prepared RPUFs was studied through closed cell content, apparent density, compression test, horizontal burning test, thermogravimetric analysis (TGA), and gel permeation chromatography (GPC), scanning electron microscopy (SEM). The addition of 28.56 wt% of MA (MA-15), MC (MC-15), and CMA (CMA-15) presented a burning time of 10.1 s with weight loss of 5.34% and 28.4 s with 13.02% and 15.25 s with 8%, respectively. The findings demonstrated that all three FRs gave RPUF good FR properties.

This study explores the blending of poly(lactic acid) (PLA) and poly(butylene adipate-co-terephthalate) (PBAT) with rice straw micro-particles (10 to 30 wt%, ≤ 250 μm) to create biocomposites using a kinetic mixer. It examines the effects of chain extender (J) and maleic anhydride (MA) as compatibilizers on material properties. Biocomposites underwent 500 h accelerated weathering to simulate environmental conditions, with analysis via Fourier-transform infrared spectroscopy (FTIR), mechanical testing, dynamic mechanical analyses (DMA), and rheological evaluations. Results indicate that the chain extender’s superior performance over MA, generating 6% insoluble content compared to 1% with MA. Scanning electron microscopy (SEM) revealed reduced interfacial voids in biocomposites treated with compatibilizers. The addition of the rice straw was found to increase the tensile modulus from 2.3 to 3.4 indicating a 43% increase after 40 wt% rice particles; all the while reducing the tensile strength and ductility. Post-weathering, Joncryl® treated samples retained properties better than MA-treated ones, showing enhanced crosslinking and less decline in tensile strength (10–19% reduction for J vs. 27–30% for MA). Compatibilizers, especially the chain extender, play a crucial role in strengthening PLA and PBAT biocomposites, particularly under accelerated weathering.

This study explores the photocatalytic performance of ZnS nanoparticle-integrated chitosan nanocomposite for degrading organic dyes in water and textile wastewater. ZnS nanoparticles with a cubic sphalerite crystal structure were uniformly distributed in a chitosan matrix, as confirmed by FT-IR, Raman, and XRD analyses. The FT-IR spectrum of ZnS displayed peaks at 410 and 490 cm^‒1 (symmetric and asymmetric Zn‒S stretching vibrations) and a peak at 640 cm^‒1 (asymmetric Zn‒S stretching). Chitosan exhibited bands at 893 and 1156 cm^‒1 (C‒H and C‒O‒C bending modes) and a peak at 1412 cm^‒1 (C‒H bending vibrations). The FT-IR spectrum of the ZnS-chitosan nanocomposite showed Zn‒S stretching modes at 619 and 670 cm^‒1, along with peaks in the 1000–1117 cm^‒1 range attributed to ZnS vibrations. Amide groups were represented by bands at 1588 cm^‒1, while chitosan contributed peaks at 1399 and 2924 cm^‒1 (C‒H bending and stretching vibrations). A broad band at 3374 cm^‒1 indicated O‒H and N‒H stretching of chitosan. Peak shifts indicated interactions between ZnS and chitosan functional groups, confirming the formation of the nanocomposite. Raman analysis revealed peak broadening due to ZnS-chitosan interactions. XRD patterns exhibited intense diffraction peaks at 2θ values of 28.6, 47.5, and 56.4°, corresponding to the cubic ZnS sphalerite phase, and a broad chitosan peak at 2θ = 20°, confirming the presence of amorphous chitosan phases. SEM images depicted spherical or near-spherical ZnS nanoparticles (30–70 nm) within the porous chitosan network, confirmed by EDX mapping. TGA/DSC indicated chitosan degradation around 250–500 °C. The residual weight% at 600 °C directly represents the content of ZnS nanoparticles. Optical studies demonstrated a reduced band gap of 2.6 eV compared to 4.25 eV for ZnS. The optimized ZnS-chitosan nanocomposite achieved up to 100% and 97.99% removal efficiency for Brilliant Blue FCF and Acid Orange 2 dyes, respectively, following pseudo-second-order kinetics. It also demonstrated 90% dye removal from textile wastewater, surpassing ZnS alone due to the high surface area, favorable adsorption, and efficient charge transfer facilitated by the ZnS-chitosan nanostructure. The excellent reusability of the nanocomposite highlights its potential for sustainable wastewater treatment.

The amount of global plastic waste on land or in marine environments is a critical environmental issue. Plastic biodegradation by microorganisms, insect larvae, and enzymes has become one of the most popular solutions due to the ability of this strategy to generate environmentally benign byproducts, addressing ecological plastic waste concerns. This study revealed the biodegradation of ethylene vinyl acetate (EVA) by the bacterial strain identified as Klebsiella aerogenes EM011, isolated from effective microorganisms. The study found that K. aerogenes EM011 can survive in a carbon-free medium for 30 days using EVA films as the sole energy source, decomposing 0.65 ± 0.04% of 1 g of EVA film. The surface changes of the film were detected using scanning electron microscopy after treatment with K. aerogenes EM011. In addition, elemental modifications were detected in the imaged area of the plastic surfaces by energy-dispersive X-ray spectroscopy. Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses were conducted to detect changes in the functional groups and chemical components, elucidating alterations on the surface of the EVA films. Through these physicochemical analyses, the formation of carbonyl groups (C=O), ester groups (C–O), and hydroxyl groups (–OH) confirmed the oxidation of EVA. Furthermore, the oxidation led to the decomposition of the EVA film, resulting in changes in its thermal stability and molecular weight distribution. These findings show that the K. aerogenes EM011 strain plays a role in accelerating the biodegradation of EVA.

Herein, we synthesized a new type of porphyrin-based porous organic polymer (PPOP) as an effective bio-inspired adsorbent capable of rapidly separating and measuring Hg(II) ions from the water. The synthesized bio-based adsorbent was analyzed by several techniques including PXRD (presented an amorphous network), FT-IR, SEM (spherical 250–1000 nm nanoparticles), EDS, BET, and TG/DTG (high thermal stability up to 500 °C). The experimental parameters in the procedure of adsorption including pH of the samples, times for adsorption and desorption, the sorbent mass, and also, the type and volume of eluent were examined and optimized. The experimental data were evaluated by Freundlich and Langmuir isotherm model equations and the results showed that the Langmuir model exhibited a better fit for mercury ions adsorption. PPOP exhibited the highest capacity for adsorption at 384.6 mg/g within only five minutes. The enhanced efficiency for adsorption can be mainly attributed to the combination effect of the electrostatic and coordination interactions between PPOP and Hg(II) ions. In addition, PPOP showed an excellent limit of detection (LOD) value of 2.1 ng L^− 1. Finally, the prepared adsorbent was employed for the extraction of Hg(II) ions in various water samples from the environment, achieving recoveries up to 91%.

In this work, poly(L-lactide) (PLLA)/poly(D-lactide) (PDLA)/carbon fiber (CF) composites with different PDLA content were prepared by simple melt blending. The stereocomplex (SC) crystallites were in situ formed. The effects of CFs and SC crystallites on the morphology, crystallization, rheological behaviors, mechanical properties, heat resistance, thermal and electrical conductivity of composites were investigated. The SC crystallites acted as nucleating agents of PLLA to accelerate the crystallization of PLLA, improve the degree of crystallinity, and refine spherical crystals, which led to a more homogeneous and dense dispersion of CFs. For the PLLA/PDLA/CF composite with 10 wt% PDLA, attributing to the synergistic effect of CFs and SC crystallites, vicat softening temperature (VST) was increased by about 100 ℃ over neat PLLA. The thermal conductivity increased from 0.21 W (mK)⁻¹ of neat PLLA to 0.47 W (mK)⁻¹, and surface resistivity decreased dramatically by about 8 orders of magnitude. More importantly, an increases of 156% and 29.2% were achieved in the tensile modulus and strength of composite with 10 wt % PDLA compared to neat PLLA. Melt viscosity and elasticity were also significantly improved with the addition of CFs and PDLA. The unusual combination of the improved mechanical and rheological performances, thermal resistance, thermal and electrical conductivity established in the degradable composites meets the properties required for a wider range of PLLA applications.