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1.
Chemphyschem ; 21(1): 9-12, 2020 Jan 03.
Artigo em Inglês | MEDLINE | ID: mdl-31483076

RESUMO

Whilst the formation of plastic nanoparticles (nanoplastics) from plastic wastes has been unequivocally evidenced, little is known about the effects of these materials on living organisms at the subcellular or molecular levels. In the present contribution we show through molecular dynamics simulations that polyethylene nanoparticles dissolve in the hydrophobic core of lipid bilayers into a network of disentangled, single polymeric chains. The thereby induced structural and dynamic changes in the bilayer alter vital functions of the cell membrane, which if lacking a mechanism to decompose the polymer chains may result in the death of the cell.


Assuntos
Membrana Celular/química , Bicamadas Lipídicas/química , Nanopartículas/química , Polietileno/química , Interações Hidrofóbicas e Hidrofílicas , Simulação de Dinâmica Molecular
2.
Sci Total Environ ; 704: 135891, 2020 Feb 20.
Artigo em Inglês | MEDLINE | ID: mdl-31838300

RESUMO

Wastewater-based epidemiology (WBE), the per capita normalised measurement of drugs, chemicals or metabolites in wastewater influent, relies on sampling and quantitative analysis to evaluate temporal and spatial trends of chemical consumption. Continuous, high-resolution, flow proportional composite sampling is optimal for accurate representations of chemical mass loads, but is rarely implemented, with conventional autosamplers providing relatively low frequency time or volume proportional samples. However, due to equipment or resource constraints at many wastewater treatment plants (WWTPs), even this may not be feasible. Passive sampling may provide an alternative sampling strategy. To investigate this, samplers comprising hollow, cylindrical Microporous Polyethylene Tubes (MPTs) containing polymeric sorbent phases of Strata-X and Strata-X in agarose were simultaneously deployed in a municipal WWTP influent stream. Samplers were extracted, analysed and evaluated for a range of illicit drugs and pharmaceuticals and personal care products (PPCPs) after 4, 7, 15, 21, and 29 day deployments. The MPT samplers were calibrated against 24-hour time proportional composite grab samples that were collected in parallel. Diffusion through the MPT governed uptake, reducing or eliminating the influence of external flow rates that may fluctuate unpredictably in a WWTP environment. Calibration data for six illicit drugs and fourteen PPCPs, including methamphetamine, benzoylecgonine, MDMA, codeine and carbamazepine, demonstrated linear accumulation in the samplers (R2 ≥ 0.84). Derived sampling rates for these analytes ranged from 0.25 to 17 mL d-1 for ibuprofen and verapamil, respectively. A validation study using this sampling rate data showed the MPT could effectively quantify concentrations (≥0.1 ng mL-1) of a range of amphetamine-type stimulants, opioids and metabolites as well as nicotine, accounting for 95% of the variance in parallel composite grab sample concentrations of these compounds. The MPT sampler shows promise for providing essential monitoring data for WBE, informing future intervention and research strategies.


Assuntos
Cosméticos/análise , Monitoramento Ambiental/instrumentação , Preparações Farmacêuticas/análise , Águas Residuárias/química , Poluentes Químicos da Água/análise , /análise , Polietileno/análise , Polietileno/química
3.
Ecotoxicol Environ Saf ; 187: 109788, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31648073

RESUMO

The potential threats of microplastics to global health are a new problem. However, little is known about the influence of microplastics on soil organisms. Here, we investigated the effects of low-density polyethylene (LDPE, < 400 µm) on earthworms (Eisenia fetida) under different concentrations (0.1, 0.25, 0.5, 1.0, 1.5 g/kg dry) with three replicates in artificial soil. Results showed that surface damage of earthworms was observed at the concentration of 1.5 g/kg LDPE after exposure 28 days. The microplastics were ingested in a dose-response manner. Smaller sizes of LDPE microplastics were found in the casts of E. fetida, and approximately 30% of the microplastics egested (size < 100 µm) were increased compared with initial microplastics in the soil. The catalase activity and malondialdehyde content increased significantly at the concentration of 1.0 g/kg LDPE after exposure 28 days, and acetylcholine esterase was significantly stimulated at concentrations of 1.5 and 1.0 g/kg LDPE on days 21 and 28, respectively. The results of this study demonstrate the potential risk of LDPE microplastics to E. fetida and may provide a reference for the impact of microplastics on terrestrial creatures.


Assuntos
/toxicidade , Oligoquetos/efeitos dos fármacos , Polietileno/toxicidade , Poluentes do Solo/toxicidade , Solo/química , Animais , Relação Dose-Resposta a Droga , Malondialdeído/metabolismo , Oligoquetos/metabolismo , Tamanho da Partícula , Polietileno/química , Poluentes do Solo/química
4.
Food Chem ; 309: 125792, 2020 Mar 30.
Artigo em Inglês | MEDLINE | ID: mdl-31711806

RESUMO

Seven commercial samples, consisted of plastic bags, tetrabrik and box, were evaluated by gas chromatography-olfactometry-mass spectrometry (GC-O-MS) to find the compounds responsible for off-odors in different PP, PE, multilayer cardboard and paper materials used for food contact. Migration assays were carried out with Tenax as food simulant to analyze the food safety as well as to evaluate the odor intensity after migration assay. Forty six compounds with characteristic odors were directly found in the materials studied. The strongest odors identified were acetic, propanoic and butyric with vinegar and rancid odors and octanal, nonanal and decanal with fat/soup odors, all of them found in PP and PE samples. Trimethylbenzenes with solvent and oily odors as well as terpenes with weakly woody odors were found in cardboard and paper materials. After migration, all compounds were below the European Legislation limits and maximum migration values recommended by Cramer. However propanoic, acetic and butyric acid as well as aldehydes compounds, phenol and 1-octanol were detected by sniffers, after migration assay, with high modified frequency (between 50 and 78%), what could change the organoleptic properties of packaged food.


Assuntos
Embalagem de Alimentos , Odorantes/análise , Olfatometria/métodos , Polietileno/química , Polipropilenos/química , Aldeídos/análise , Contaminação de Alimentos/análise , Cromatografia Gasosa-Espectrometria de Massas , Papel , Fenóis/análise
5.
J Environ Sci (China) ; 87: 349-360, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31791508

RESUMO

Low-density polyethylene (LDPE) has been widely used as a sorbent for passive sampling of hydrophobic organic contaminants (HOCs) in aquatic environments. However, it has seen only limited application in passive sampling for measurement of freely dissolved concentrations of parent and substituted PAHs (SPAHs), which are known to be toxic, mutagenic and carcinogenic. Here, the 16 priority PAHs and some typical PAHs were selected as target compounds and were simultaneously determined by gas chromatography-mass spectrometer (GC-MS). Some batch experiments were conducted in the laboratory to explore the adsorption kinetics of the target compounds in LDPE membranes. The results showed that both PAHs and SPAHs could reach equilibrium status within 19-38 days in sorption kinetic experiments. The coefficients of partitioning between LDPE film (50 µm thickness) and water (KLDPE) for the 16 priority PAHs were in good agreement with previously reported values, and the values of KLDPE for the 9 SPAHs are reported in this study for the first time. Significant linear relationships were observed, i.e., log KLDPE = 0.705 × log KOW + 1.534 for PAHs (R2 = 0.8361, p < 0.001) and log KLDPE = 0.458 × log KOW + 3.092 for SPAHs (R2 = 0.5609, p = 0.0077). The selected LDPE film was also proven to meet the condition of "zero sink" for the selected target compounds. These results could provide basic support for the configuration and in situ application of passive samplers.


Assuntos
Monitoramento Ambiental/métodos , Hidrocarbonetos Policíclicos Aromáticos/análise , Polietileno/análise , Poluentes Químicos da Água/análise , Adsorção , Interações Hidrofóbicas e Hidrofílicas , Cinética , Hidrocarbonetos Policíclicos Aromáticos/química , Polietileno/química , Poluentes Químicos da Água/química
6.
Chemosphere ; 245: 125628, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31864060

RESUMO

Microplastics and Nitropolycyclic aromatic hydrocarbons (NPAHs) are two types of emerging pollutants that are strong potential threats to aquatic ecosystems and organisms. The adsorption of NPAHs on microplastics may explain the fate and effects of NPAHs in natural environments. In this study, the adsorption behavior of 9-Nitroanthrene (9-NAnt) on polyethylene (PE), polypropylene (PP) and polystyrene (PS) was investigated. Kinetic experiments revealed that 9-NAnt was inclined to be adsorbed onto microplastics, especially PE, which had a large adsorption amount of 734 µg g-1. A linear isothermal model better described the isothermal adsorption process for 9-NAnt, which indicated that a hydrophobic distribution may be the main adsorption mechanism in an aqueous solution. Water environment factors, such as the pH and ionic strength, had negligible effects on the adsorption for PE. In contrast, alkaline and high ionic strength conditions resulted in the inhibition of adsorption of PP and PS. In addition, the particle size of microplastics was negatively correlated with the log Kd of 9-NAnt, and the performance of transient aging treatments on microplastics reduced their affinity for 9-NAnt, due to the addition of oxygen-containing functional groups. Above all, hydrophobic and electrostatic processes were the main adsorption mechanisms between microplastics and 9-NAnt.


Assuntos
Antracenos/química , Poluentes Químicos da Água/química , Adsorção , Ecossistema , Interações Hidrofóbicas e Hidrofílicas , Cinética , Plásticos/química , Polietileno/química , Polipropilenos/química , Poliestirenos/química , Eletricidade Estática , Poluentes Químicos da Água/análise
7.
Bull Environ Contam Toxicol ; 103(6): 766-769, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31587083

RESUMO

The ingestion of microplastics by marine species has been at least partially attributed to plastics emitting a dimethyl sulfide signature when exposed to marine conditions. Dimethyl sulfide, a member of the volatile organic sulfur compounds group, is an infochemical that many species rely on to locate and identify prey while foraging. Microplastic ingestion is also observed in freshwater systems; however, this study shows that the same dimethyl sulfide signature is not obtained by three common types of plastic (high-density polyethylene, low-density polyethylene, and polystyrene) in freshwater systems, suggesting that there may be an alternate mechanism driving plastic ingestion by freshwater species.


Assuntos
Água Doce/química , Sulfetos/química , Animais , Monitoramento Ambiental , Modelos Químicos , Polietileno/química , Poliestirenos/química , Sulfetos/análise , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/química
8.
J Food Sci ; 84(11): 3194-3203, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31589346

RESUMO

A multilayer film containing star anise essential oil and thymol coating layers (SAEO and TH, respectively), with insect repellent and antimicrobial properties, has been developed using bar coating and adhesive lamination processes. Our previous study reported the in vitro activities of this polypropylene film (PP)/SAEO/polyethylene terephthalate film (PET)/TH/low-density polyethylene film (LDPE) multilayer film. The current study focused on demonstrating the morphological, optical, and mechanical properties of the film, and evaluating its in vivo activities when used as a bread packaging material. The developed film was 15.03% thicker and 1.86% less transparent than the control film (without active agent coating layers: PP/PET/LDPE). While the color values of the developed film were slightly different from the control film, both films appeared similar to the naked eye. The tensile strength in the developed film was somewhat lower than that of the control film, while both films had statistically comparable values for elongation at break. During storage of sliced bread packaged in the developed film, the film both deterred insects from approaching toward and impeded the growth of microorganisms in the bread. These results suggest the potential applicability of the developed film as an active food packaging material with insect repellent and antimicrobial activities. PRACTICAL APPLICATION: A multilayer film incorporated with insect repellent and antimicrobial coating layers was applied in sliced wheat bread packaging. The developed film effectively inhibited approaches of stored-product insects to packaged bread and growth of microorganisms on the bread surface. It can be used as an active food packaging material that improves the safety and shelf-life of foods.


Assuntos
Antibacterianos/química , Pão/análise , Conservação de Alimentos/métodos , Illicium/química , Repelentes de Insetos/química , Óleos Voláteis/química , Timol/química , Animais , Antibacterianos/farmacologia , Bactérias/efeitos dos fármacos , Bactérias/crescimento & desenvolvimento , Pão/microbiologia , Embalagem de Alimentos/instrumentação , Conservação de Alimentos/instrumentação , Repelentes de Insetos/farmacologia , Insetos/efeitos dos fármacos , Insetos/crescimento & desenvolvimento , Óleos Voláteis/farmacologia , Óleos Vegetais/química , Óleos Vegetais/farmacologia , Polietileno/química , Polipropilenos/química , Timol/farmacologia , Triticum/química , Triticum/microbiologia
9.
Mar Pollut Bull ; 145: 260-269, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31590785

RESUMO

The sorption of polybrominated diphenyl ethers (PBDEs) onto polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyamide (PA) microplastics was analyzed using different kinetic and isotherm models, and under various environmental conditions, including temperature, pH, salinity and dissolved organic matter (DOM). The sorption capacity was in the order of PS > PA > PP > PE, due to the different crystallinity, specific surface area, and surface structure. PS demonstrated the equilibrium sorption capacity, namely, 6.41 ng/g BDE-47, 12.83 ng/g BDE-99, and 14.42 ng/g BDE-153. The second-order kinetic model described the sorption kinetics of PBDEs, and surface sorption was the main mechanism. The sorption of PBDEs by microplastics was a multilayer and physical process. Low temperatures reduced BDE-47 sorption on microplastics, and sorption was a spontaneous and endothermic process. The sorption of BDE-47 was not significantly influenced by pH and salinity. However, DOM exerted a negative effect on the sorption of BDE-47.


Assuntos
Éteres Difenil Halogenados/química , Plásticos/química , Poluentes Químicos da Água/química , Adsorção , Concentração de Íons de Hidrogênio , Cinética , Bifenil Polibromatos/química , Polietileno/química , Poliestirenos/química , Salinidade , Temperatura Ambiente
10.
Mar Pollut Bull ; 145: 306-315, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31590792

RESUMO

Understanding the fate of spilled oil in cold environments is essential for oil spill response in Arctic areas. The potential for oils to adhere to sea ice and mechanical skimmers can significantly impact the success of oil spill response and influence the fate of oil in the marine environment. Therefore, the affinity of oil to sea ice and skimmer material was quantified experimentally for three different types of oils at various degrees of weathering. Contact angle measurements of crude oil droplets were performed on the top of and under sea ice and polyethylene-based skimmer material, being submerged in seawater (-2 °C). In addition, "dip- and refloat" tests were performed to quantify the adhesion and study the re-floating process of oil from sea ice at -2 °C (moist ice) and -20 °C (cold dry ice), and from a skimmer material prior to and subsequently to its submersion in seawater (-2 °C). The results indicated limited interaction of oils with sea ice submerged in seawater, but a strong affinity of oils towards polyethylene-based skimmer material.


Assuntos
Camada de Gelo/química , Petróleo , Polietileno/química , Água do Mar/química , Poluentes Químicos da Água/química , Regiões Árticas , Poluição por Petróleo/análise
11.
Mar Pollut Bull ; 145: 536-546, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31590821

RESUMO

Microplastic particles (<5 mm), which are an emerging threat, are commonly found in marine ecosystems worldwide. This study investigated the effect of different types of coastal land use on microplastic frequency and distribution on the coastline of Bandar Abbas city; this study used a large sample compared to that used in other studies conducted in this region. The average number of microplastics was determined as 3252 ±â€¯2766 microplastics/m2 (±SD). ATR FT-IR spectroscopy showed that the dominant microplastic particles are expanded polystyrene, polyethylene terephthalate, polypropylene, and polyethylene. Statistical analysis showed a significant difference in microplastic contamination levels between the urban and nonuse beaches. This shows that heavily urbanized areas and human activities have significant effects on the dispersion and frequency of microplastics in the coastal areas of Bandar Abbas. Periodical coast-based cleanup and studies on microplastic pollution and their fluxes by comprehensive sampling are mostly recommended for the Persian Gulf coastline.


Assuntos
/análise , Poluentes Químicos da Água/análise , Monitoramento Ambiental/métodos , Oceano Índico , Irã (Geográfico) , Polietileno/análise , Polietileno/química , Polipropilenos/análise , Polipropilenos/química , Poliestirenos/análise , Poliestirenos/química , Espectroscopia de Infravermelho com Transformada de Fourier , Urbanização , Poluentes Químicos da Água/química
12.
Mar Pollut Bull ; 145: 547-554, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31590822

RESUMO

Microplastics are becoming a global concern due to their potential to accumulate pollutants in aquatic environments. In this paper, sulfamethazine (SMT) sorption onto six types of microplastics, including polyamide (PA), polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP), polystyrene (PS), and polyvinyl chloride (PVC) was investigated by experimental and molecular dynamics simulation methods. The experimental results indicated that SMX sorption reached equilibrium within 16 h. The kinetics of SMT sorption by PA, PVC, PE, and PP could be fitted by pseudo first-order model, while SMT sorption by PA and PET could be described by pseudo second-order model. The partition coefficient Kd values were 38.7, 23.5, 21.0, 22.6, 18.6 and 15.1 L·kg-1 for PA, PE, PS, PET, PVC and PP, respectively. SMT sorption onto microplastics decreased when pH and salinity increased. The molecular dynamics simulation results indicated that the main mechanisms involved in sorption are electrostatic and Van der Waals interaction.


Assuntos
/química , Sulfametazina/química , Poluentes Químicos da Água/química , Adsorção , Concentração de Íons de Hidrogênio , Cinética , Simulação de Dinâmica Molecular , Polietileno/química , Polietilenotereftalatos , Polipropilenos/química , Poliestirenos/química , Cloreto de Polivinila/química , Eletricidade Estática
13.
Mar Pollut Bull ; 145: 604-610, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31590830

RESUMO

A floating plastic monitoring program was conducted for two years on a weekly basis in Banderas Bay, Mexico. A total of 94 samples were collected from May 2016 to April 2018 in the southern part of the bay. Half (57%) of them contained plastic debris; 79% of it being <5 mm in length. Polypropylene and Polyethylene were the most abundant polymers, accounting for 45% and 43% of the plastic pieces (pp), respectively. The highest abundance of plastic pieces was found in July 2016, with a maximum of 0.3 pp/m3 found in one sample. The amount of floating plastics was significantly higher in the hurricane season compared to the dry season (p < 0.001). This suggests that rainfall may play a significant role in the offload of plastics from land-based sources into the bay.


Assuntos
Plásticos/análise , Poluentes Químicos da Água/análise , Baías , Monitoramento Ambiental , México , Plásticos/química , Polietileno/análise , Polietileno/química , Polipropilenos/análise , Polipropilenos/química , Estações do Ano , Resíduos/análise
14.
Molecules ; 24(19)2019 Oct 07.
Artigo em Inglês | MEDLINE | ID: mdl-31591310

RESUMO

The Rapid Alert System for Food and Feed (RASFF) has reported many cases of different UV curing inks components in foodstuffs during the last few years. These contaminants reach foodstuffs mainly by set-off, their principal migration mechanism from the package. Under this premise, this work has tried to characterize the process of migration of two common UV ink components: a photoinitiator (4-Methylbenzophenone) and a coinitiator (Ethyl-4-(dimethylamino) benzoate), from the most common plastic material used in food packaging low-density polyethylene (LDPE) into six different food simulants. The migration kinetics tests were performed at four different common storage temperatures, obtaining the key migration parameters for both molecules: the coefficients of diffusion and partition. The migration process was highly dependent on the storage conditions, the photoinitiator properties and the pH of the foodstuff.


Assuntos
Benzofenonas/análise , Contaminação de Alimentos/análise , Embalagem de Alimentos , para-Aminobenzoatos/análise , Difusão , Tinta , Cinética , Modelos Químicos , Plásticos/química , Polietileno/química , Temperatura Ambiente , Raios Ultravioleta
15.
J Chem Phys ; 151(14): 144901, 2019 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-31615257

RESUMO

We demonstrate that nascent polymer crystals (i.e., nuclei) are anisotropic entities with neither spherical nor cylindrical geometry, in contrast to previous assumptions. In fact, cylindrical, spherical, and other high symmetry geometries are thermodynamically unfavorable. Moreover, postcritical transitions are necessary to achieve the lamellae that ultimately arise during the crystallization of semicrystalline polymers. We also highlight how inaccurate treatments of polymer nucleation can lead to substantial errors (e.g., orders of magnitude discrepancies in predicted nucleation rates). These insights are based on quantitative analysis of over four million crystal clusters from the crystallization of prototypical entangled polyethylene melts. New comprehensive bottom-up models are needed to capture polymer nucleation.


Assuntos
Polietileno/química , Cristalização , Conformação Molecular , Simulação de Dinâmica Molecular , Termodinâmica
16.
Ecotoxicol Environ Saf ; 186: 109778, 2019 Dec 30.
Artigo em Inglês | MEDLINE | ID: mdl-31627095

RESUMO

Freshness protection packages and preservative films are widely used food-contact plastic made of polyethylene. Diode array detector (DAD), charged aerosol detector (CAD) and evaporative light-scattering detector (ELSD) were evaluated for determination of 6 bisphenols (bisphenol A, bisphenol S, bisphenol F, bisphenol B, bisphenol AF and tetrabromobisphenol A.) in polyethylene. DAD presented better parameters including limit of quantification (LOQs) ranging from 0.05 to 0.5 µg/g with relative standard deviations (RSDs, n = 5) lower than 1% at two concentration levels. CAD and ELSD are universal detectors with relative consistent response parameters for different analogues which have potential application by using single calibrant for quantification of multiple analytes. Matrix effects were barely observed on three detectors. Samples of freshness protection packages and preservative films were further analyzed and preliminary profiles of bisphenols in products from Beijing market was obtained. Bisphenol S have become most abundant analogue instead of bisphenol A in investigated products.


Assuntos
Compostos Benzidrílicos/análise , Cromatografia Líquida de Alta Pressão/métodos , Embalagem de Alimentos , Fenóis/análise , Polietileno/química , Sulfonas/análise , Cromatografia Líquida de Alta Pressão/instrumentação , Limite de Detecção
17.
Mar Pollut Bull ; 149: 110579, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31551196

RESUMO

Microplastics in wastewater treatment plant (WWTP) effluent have been identified and quantified, but few studies have examined the microplastics in advanced treatment systems. A new method for isolating, quantifying, and determining the polymer type of microplastics was developed that included chemical digestion coupled with Raman microspectroscopy to investigate microplastics in the effluent of reverse osmosis nanofiltration and activated carbon filtration systems. This method allows for the removal of organics and the quantification and identification of all microplastics present in the sample. A large number of microplastics, the majority of which were smaller than 10 µm, were identified in the effluent of the advanced filtration systems with polyethylene the most common polymer identified. This study not only reports a new method for microplastic identification and quantification but also shows the importance of measuring the smallest fraction of microplastics, those smaller than 20 µm, which have previously been understudied.


Assuntos
/análise , Análise Espectral Raman/métodos , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/análise , Carvão Vegetal , Monitoramento Ambiental/métodos , Filtração/métodos , Limite de Detecção , /isolamento & purificação , Polietileno/análise , Polietileno/química , Polietileno/isolamento & purificação , Virginia , Águas Residuárias/química , Poluentes Químicos da Água/química , Poluentes Químicos da Água/isolamento & purificação
18.
Chemosphere ; 235: 1073-1080, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31561297

RESUMO

As one of emerging contaminants, microplastics (MPs) can enter the environment and adsorb toxic metals such as cadmium (Cd), thereby causing potential environmental risks. However, adsorption characteristics of MPs are poorly understood. Herein, batch experiments were performed to investigate the adsorption characteristics of Cd onto high-density polyethylene (HDPE) MPs with different particle sizes, that is, 1-2 mm, 0.6-1 mm, and 100-154 µm. The adsorption of Cd was quite rapid initially, and the equilibrium time was approximately 90 min. An increase in the pH of the Cd solution led to an increase in Cd adsorption. MPs with particle size of 100-154 µm had the highest adsorption capacity. Addition of 1, 10, and 100 mg/L NaCl all significantly decreased Cd adsorption. Adsorption kinetics fitted the pseudo-second-order model. Adsorption isotherm followed the Langmuir model and, to a lesser extent, the Freundlich model, with estimated maximum adsorption capacity of 30.5 µg/g. The adsorbed Cd easily desorbed from the MPs. Energy-dispersive X-ray spectroscopy (EDS) analysis confirmed Cd adsorption to and desorption from MPs. Fourier transform infrared (FTIR) spectroscopy analysis showed no new functional groups formed during the adsorption and desorption processes, suggesting physical interaction may dominate the Cd adsorption onto MPs. The present study findings provide evidence that MPs can accumulate Cd, and the adsorbed Cd may be highly available, thus posing risks to the organisms exposed to these MPs.


Assuntos
Cádmio/química , Plásticos/química , Água/química , Adsorção , Cinética , Tamanho da Partícula , Polietileno/química , Soluções , Espectroscopia de Infravermelho com Transformada de Fourier
19.
Bioengineered ; 10(1): 397-408, 2019 12.
Artigo em Inglês | MEDLINE | ID: mdl-31526157

RESUMO

Nowadays, there is an increasing concern toward substituting the scarce wood fibers with alternative lignocellulosic fibers that originate from crop residue to reinforce biocomposites. In this paper, the potential application of coffee hull (CH) of the reinforced polyethylene (PE) matrix composites was studied for the first time. Experiments of composite that enhanced with CH on mechanical properties, hydroscopicity, thermogravimetric analysis, fiber treatment, and microstructures were tested in this study. The PE matrix was reinforced with varying volume fractions of CH and was studied. The results show that incorporation of coffee hull markedly improved the mechanical properties of the reinforced high-density polyethylene (HDPE) matrix composites. Micrographs show a strong interfacial adhesion between the CH fiber particles. This property may be the main reason for the stability between composites. At the same time this work investigated the effect of different treatments on the mechanical properties and water absorption behavior of composites. The fiber surface treatments were done using active chemicals such as calcium hydroxide (Ca(OH)2), silane coupling agent (SCA), maleic anhydride grafted polypropylene (MA-g-PP), stearic acid (SA), ethylene bis stearamide (EBS) and the combination (MA-g-PP, SA, EBS). The results show that (Ca(OH)2)treatment is the best way to improve its properties. Probably because attributed to removal of surface active functional groups (-OH) from the CH fiber and induction of hydrophobicity that in turn improved the compatibility with the polymer matrix. As a result, the use of coffee hull in composites could have great significance for the industry.


Assuntos
Café/química , Manufaturas , Plásticos/síntese química , Polietileno/química , Hidróxido de Cálcio/química , Humanos , Interações Hidrofóbicas e Hidrofílicas , Anidridos Maleicos/química , Teste de Materiais , Plásticos/química , Silanos/química , Ácidos Esteáricos/química , Temperatura Ambiente , Resistência à Tração , Resíduos , Molhabilidade
20.
Mater Sci Eng C Mater Biol Appl ; 105: 110088, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31546431

RESUMO

The antibacterial PE cling films were successfully obtained through precipitation polymerization and UV polymerization of N,N'-[(4,5-dihydroxy-1, 2-phenylene)bis(methylene)] bisacrylamide (OHABA) monomers, respectively. The inhibition rates of the PE cling films using UV polymerization method against E. coli and B. subtilis were 85.1% and 92.1% respectively, whilst the inhibition rates of the antibacterial PE cling films prepared by precipitation polymerization method against E. coli and B. subtilis were 97.7% and 91.4% respectively. The antibacterial PE cling films using precipitation polymerization method was found to have more excellent antibacterial ability than that using UV polymerization method probably due to the larger surface coverage of OHABA. The POHABA modified PE cling films have great potential in food packaging.


Assuntos
Antibacterianos , Bacillus subtilis/crescimento & desenvolvimento , Escherichia coli/crescimento & desenvolvimento , Membranas Artificiais , Polietileno , Antibacterianos/química , Antibacterianos/farmacologia , Polietileno/química , Polietileno/farmacologia
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