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1.
Bioresour Technol ; 300: 122700, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31918293

RESUMO

The objective of this study was to evaluate pyrolysis and co-pyrolysis behavior of cellulose and poly(methyl methacrylate) (PMMA) and examine the kinetics of the processes by using thermogravimetric analysis (TGA) coupled with FT-IR spectrometry. For this purpose, non-isothermal experiments were carried out using different heating rates and three prominent iso-conversional methods were used to obtain kinetic parameters at various extents of conversions from 0.1 to 0.9. Blending PMMA with cellulose had a marked effect on the process. The results of co-pyrolysis using a blending ratio of 50 wt% PMMA indicated that the highest rate of pyrolytic transformation was achieved at a conversion degree of 0.5 while activation energy ranged from 188.1 to 364.3 kJ/mol. The most intensive gas release during cellulose pyrolysis was CO2. Co-pyrolysis was more complicated than that of pyrolysis of cellulose and PMMA due to depolymerization and radical interactions.


Assuntos
Celulose , Polimetil Metacrilato , Cinética , Pirólise , Espectroscopia de Infravermelho com Transformada de Fourier , Termogravimetria
2.
Bioresour Technol ; 301: 122732, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31972399

RESUMO

In this work, the thermal degradation behaviors of two kinds of biomasses (pinewood and rice husk) with powder and pellet under three oxygen concentrations were investigated by a self-designed macro-thermogravimetric analyzer. An obvious hysteresis of thermal degradation of biomass pellets was observed under three conditions. The maximum activation energy of biomass pellets was significantly greater than that of biomass powders, while their average activation energies were almost equal based on distributed activation energy model. For the oxygen-rich combustion, the comprehensive combustion character index of powdered and pelletized biomasses ranged from 3.92 × 10-7 to 5.16 × 10-7%2·min-2·°C-3 and from 1.82 × 10-7 to 1.91 × 10-7%2·min-2·°C-3, respectively. Furthermore, the derived biochar of powdered biomass has a higher caloricity than that of pelletized biomass during combustion by TG-DSC analysis. The performances of thermal degradation observed by macro-thermogravimetric analyzer could factually reveal the influence of mass and heat transfer on the thermochemical conversion of powdered and pelletized biomasses.


Assuntos
Temperatura Alta , Biomassa , Cinética , Pós , Termogravimetria
3.
Bioresour Technol ; 297: 122490, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31812595

RESUMO

The effects of torrefaction pretreatment on corncobs properties and its pyrolysis kinetic parameters were investigated in this study. Proximate and ultimate analyses indicated that torrefaction increased the H/Ceff ratio and higher heating value of corncobs, and reduced its oxygen content. Although the mass yield was also reduced, the corresponding energy yield was relatively higher. The crystallinity index of biomass showed a first upward and then downward trend with the torrefaction temperature. Kinetic parameters obtained from three models indicated that both the activation energy and the pre-exponential factor increased with the elevated torrefaction temperature and it's better to calculate the activation energy by the OFW method and to use the KAS and DAEM methods to calculate the pre-exponential factor. In addition, it was found that the optimum pretreatment temperature of corncobs was 240 °C.


Assuntos
Zea mays , Biomassa , Cinética , Temperatura Ambiente , Termogravimetria
4.
Waste Manag ; 102: 270-280, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-31698229

RESUMO

Solid recovered fuel (SRF) has the characteristics of high calorific value and low chlorine and mercury content. The thermal decomposition of SRF collected from a municipal solid waste (MSW) incineration power plant in Hangzhou was investigated in this study. The study exhibits far-reaching significance for the design and commercial operation of SRF pyrolysis facilities and circulating fluidized bed (CFB) power plants. The pyrolysis behavior of SRF and its sorted components was evaluated by thermogravimetric analysis (TG). Five heating rates of 10, 15, 20, 25 and 30 °C·min-1 were conducted to analyze the effect of heating rate. The interactive effect of the sorted components was discussed by comparing the experimental and theoretical curves. Furthermore, the kinetic parameters were determined by using the Coats-Redfern (CR), Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO) methods. The activation energies of SRF and its sorted components in the pyrolysis process were obtained. The main reaction stages of the SRF and its sorted components were described by different mechanism functions. However, it was found that the KAS and FWO methods were not applicable for SRF according to the comparison results. The results provide useful information for the design and commercial operation of SRF pyrolysis facilities and CFB power plants.


Assuntos
Incineração , Resíduos Sólidos , Calefação , Cinética , Termogravimetria
5.
Waste Manag Res ; 38(1): 100-106, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31603400

RESUMO

Thermal treatment offers an alternative method for the separation of aluminum foil and cathode materials during spent lithium-ion batteries recycling. In this work, the combustion kinetic of cathode was studied based on six model-free (isoconversional) methods, namely Flynn-Wall-Ozawa (FWO), Friedman, Kissinger-Akahira-Sunose, Starink, Tang, and Boswell methods. The possible decomposition mechanism was also probed using a master-plots method (Criado method). Thermogravimetric analysis showed that the whole thermal process could be divided into three stages with temperatures of 37-578°C, 578-849°C, and 849-1000°C. The activation energy (Eα) derived from these model-free methods displayed the same trend, gradually increasing with a conversion range of 0.002-0.013, and significantly elevating beyond this range. The coefficients from the FWO method were larger, and the resulted Eα fell into the range of 10.992-40.298 kJ/mol with an average value of 20.228 kJ/mol. Comparing the theoretical master plots with an experimental curve, the thermal decomposition of cathode could be better described by the geometric contraction models.


Assuntos
Fontes de Energia Elétrica , Lítio , Eletrodos , Cinética , Termogravimetria
6.
Waste Manag Res ; 38(2): 202-212, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31405341

RESUMO

Due to a huge increase in polymer production, a tremendous increase in municipal solid waste is observed. Every year the existing landfills for disposal of waste polymers decrease and the effective recycling techniques for waste polymers are getting more and more important. In this work pyrolysis of waste polystyrene was performed in the presence of a laboratory synthesized copper oxide. The samples were pyrolyzed at different heating rates that is, 5°Cmin-1, 10°Cmin-1, 15°Cmin-1 and 20°Cmin-1 in a thermogravimetric analyzer in inert atmosphere using nitrogen. Thermogravimetric data were interpreted using various model fitting (Coats-Redfern) and model free methods (Ozawa-Flynn-Wall, Kissinger-Akahira-Sunose and Friedman). Thermodynamic parameters for the reaction were also determined. The activation energy calculated applying Coats-Redfern, Ozawa-Flynn-Wall, Kissinger-Akahira-Sunose and Friedman models were found in the ranges 105-148.48 kJmol-1, 99.41-140.52 kJmol-1, 103.67-149.15 kJmol-1 and 99.93-141.25 kJmol-1, respectively. The lowest activation energy for polystyrene degradation in the presence of copper oxide indicates the suitability of catalyst for the decomposition reaction to take place at lower temperature. Moreover, the obtained kinetics and thermodynamic parameters would be very helpful in determining the reaction mechanism of the solid waste in a real system.


Assuntos
Poliestirenos , Resíduos Sólidos , Calefação , Cinética , Termogravimetria
7.
Chemosphere ; 239: 124745, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31521939

RESUMO

A novel three dimensional MnO2 modified biochar-based porous hydrogel (MBCG) was fabricated to overcome the low sorption capacity and difficulty in solid-liquid separation of biochar (BC) for Cd(II) and Pb(II) removal. BC was initially modified by a rapid redox reaction between KMnO4 and Mn(II) acetate, and then incorporated into a polyacrylamide gel network via a rapid and facile free-radical polymerization. A foaming method was deliberately introduced during the fabrication to establish interpenetrated porous structure inside the network. Various characterizations were employed to examine the morphology, porous structures, chemical compositions, and mechanical properties of the samples. Adsorption performance of MBCG on Cd(II) and Pb(II) (isotherms and kinetics) as well as its desorption and reusability were also investigated. The results indicated that MnO2 modified biochars (MBC) were successfully introduced and homogeneously distributed in the porous bulk hydrogel, endowing MBCG with more uniform pore structure, excellent thermostability, remarkable mechanic strength, and superior adsorption performance. The maximum Langmuir adsorption capacity on Cd(II) and Pb(II) is 84.76 and 70.90 mg g-1, respectively, which is comparable or even larger than that of MBC. More importantly, MBCG can be rapidly separated and easily regenerated with an excellent reusability, which could retain 92.1% and 80.5% of the initial adsorption capacities of Cd(II) and Pb(II) after five cycles. These new insights make MBCG an ideal candidate in practical applications in water treatment and soil remediation contaminated with various heavy metals.


Assuntos
Cádmio/isolamento & purificação , Carvão Vegetal/química , Hidrogéis/química , Chumbo/isolamento & purificação , Compostos de Manganês/química , Óxidos/química , Resinas Acrílicas/química , Adsorção , Cádmio/química , Poluentes Ambientais/química , Poluentes Ambientais/isolamento & purificação , Chumbo/química , Microscopia Eletrônica de Varredura , Microscopia Eletrônica de Transmissão , Polimerização , Porosidade , Impressão Tridimensional , Espectroscopia de Infravermelho com Transformada de Fourier , Termogravimetria
8.
Bioresour Technol ; 299: 122602, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31869633

RESUMO

Sida cordifolia L. (Sida) is an annual invasive plant that remains underutilized in Niger. The goal of this study was to characterize the thermal decomposition of Sida for its valorisation as a source of energy through thermogravimetric analysis (TGA). TGA was carried out under nitrogen and air atmospheres. Thus, five different heating rates were used as 10, 20, 30, 40, 50 °C min-1. Kinetic and thermodynamic parameters were determined by isoconversional models of Kissenger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO). The results showed that the average activation energy (Ea) of Sida calculated by KAS and FWO in pyrolysis was found to be 74.74 and 80.74 kJ mol-1 respectively, while it was 51.08 and 58.91 kJ mol-1 in combustion respectively. Kinetic and thermodynamic parameters such as Ea, ΔH, ΔS, and ΔG obtained by KAS and FWO show that Sida is a remarkable feedstock for bioenergy.


Assuntos
Calefação , Pirólise , Cinética , Níger , Termogravimetria
9.
Chemosphere ; 239: 124736, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31494326

RESUMO

In this work, a novel process involving the preparation of nanochitosan-grafted flocculants (CPAM-g-NCS) to treat low turbid and salmonella suspensions simultaneously was introduced. Nanotechnology was employed to enhance the adsorption-adhesion and sterilization abilities of dual-functional flocculants. The monomers of chitosan, acrylamide, methacryloyl ethyl trimethyl ammonium chloride, and sodium tripolyphosphate were utilized for flocculants copolymerization. Then, using fourier-transform infrared spectroscopy, nuclear magnetic resonance hydrogen spectrum, and thermogravimetric and differential scanning calorimetry analysis, the successful synthesis of CPAM-g-NCS was verified. Scanning electron microscopy and size analysis suggested that nanostructured flocculants with irregular morphology and nanocolloids of 60.44 nm were formed. CPAM-g-NCS was applied to treat a series of simulated low turbid and salmonella suspensions. The simulation results showed that the minimum residual turbidity of 1.97 NTU and optical density of 0.16 (initial 0.89) can be achieved at dosages of 2.5 and 8.75 mg L-1, respectively, which were superior to conventional organics flocculants. Mechanistic studies suggested that the excellent adsorption property, and large numbers of quaternary ammonium and amino groups of nanoflocculants contributed to the superior flocculation and antibacterial performance of CPAM-g-NCS.


Assuntos
Anti-Infecciosos/química , Anti-Infecciosos/farmacologia , Nanoestruturas/química , Purificação da Água/métodos , Acrilamida/química , Varredura Diferencial de Calorimetria , Quitosana/química , Floculação , Espectroscopia de Ressonância Magnética , Metacrilatos/química , Microscopia Eletrônica de Varredura , Polimerização , Salmonella typhimurium/efeitos dos fármacos , Espectroscopia de Infravermelho com Transformada de Fourier , Suspensões , Termogravimetria , Microbiologia da Água
10.
Int J Nanomedicine ; 14: 6645-6659, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31686804

RESUMO

Introduction: It is well known that the grafted multiwalled carbon nanotubes (MWCNTs) have antibacterial activity and lower cytotoxicity. Moreover, pyrazole derivatives have a broad spectrum of biological activity due to their fertile template for many medicinal drugs. On view of these findings we report herein the hybridization between MWCNTs and some pyrazole derivatives as antibacterial agents. Materials and methods: Pyrazole and pyrazolone derivatives were grafted onto the surface of carboxylated MWCNTs via the reaction of carboxylated MWCNTs and the diazonium salts of pyrazoles and pyrazolones using mixed acid treatment. The insertion of the pyrazole and pyrazolone moieties was characterized by Fourier transform infrared (FTIR) spectroscopy, energy dispersion spectroscopy, transmission electron microscopy, X-ray diffraction and thermogravimetric (TGA). Results: The results indicate that pyrazole and pyrazolone moieties successfully attached on carboxylated MWCNTs surface. The neat pyrazole and pyrazolone derivatives and their corresponding carbon nanotubes were tested against Staphylococcus aureus, Bacillus subtilus, Escherichia coli, and Candida albicans bacteria, and Aspergillusniger fungi. The results showed that the grafted carbon nanotubes of pyrazole and pyrazolone derivatives have better antimicrobial activity than the neat pyrazole and pyrazolone derivatives. The molecular docking studies were performed on the most potent antimicrobial compounds to investigate the existence of the interactions between the most active inhibitors and Farnesyl pyrophosphate synthase (FPPS). Conclusion: The surface of the carboxylated MWCNTs was successfully grafted with some pyrazole derivatives. The antibacterial activity was investigated for the newly synthesized compounds and indicated that the grafted MWCNTs have good antibacterial activity toward some pathogenic types of bacteria.


Assuntos
Antibacterianos/farmacologia , Simulação de Acoplamento Molecular , Nanotubos de Carbono/química , Pirazóis/química , Pirazóis/farmacologia , Bactérias/efeitos dos fármacos , Domínio Catalítico , Fungos/efeitos dos fármacos , Ligantes , Testes de Sensibilidade Microbiana , Nanotubos de Carbono/ultraestrutura , Pirazóis/síntese química , Espectroscopia de Infravermelho com Transformada de Fourier , Termogravimetria , Difração de Raios X
11.
Environ Sci Technol ; 53(22): 13495-13505, 2019 Nov 19.
Artigo em Inglês | MEDLINE | ID: mdl-31644877

RESUMO

Biomass, a renewable energy source, via available thermo-chemical processes has both engineering and environmental advantages. However, the understanding of the kinetics, evolved gases, and mechanisms for biomass pyrolysis is limited. We first propose a novel temperature response mechanism for the pyrolysis of sugar cane residue using thermogravimetric analysis-Fourier transform infrared spectrometry-mass spectrometry (TG-FTIR-MS) combined with Gaussian model and two-dimensional correlation spectroscopy (2D COS). The existence and contribution of distinct peaks in TG-FTIR spectra were innovatively distinguished and quantified, and the temperature-dependent dynamics of gas amounts were determined using Gaussian deconvolution. The 2D-TG-FTIR/MS-COS results revealed for the first time that the primary sequential temperature responses of gases occurred in the order: H2O/CH4 > phenols/alkanes/aromatics/alcohols > carboxylic acids/ketones > CO2/ethers > aldehyde groups/acetaldehyde. Subtle sequential changes even occurred within the same gases during pyrolysis. The quantity dynamics and sequential responses of gases were fitted to the combined effects of the order-based, diffusion, and chemical reaction mechanisms for the component degradation. The combination of TG-FTIR-MS, Gaussian model, and 2D COS is a promising approach for the online monitoring and real-time management of biomass pyrolysis, providing favorable strategies for pyrolysis optimization, byproduct recovery, energy generation, and gas emission control in engineering and environmental applications.


Assuntos
Gases , Saccharum , Biomassa , Cinética , Pirólise , Espectroscopia de Infravermelho com Transformada de Fourier , Termogravimetria
12.
Mar Pollut Bull ; 145: 153-160, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31590772

RESUMO

As a global pollutant, microplastics have attracted attention from the public and researchers. However, the lack of standard and time-saving methods for analysis has become one of the bottlenecks in microplastics research. Here, we demonstrate TGA coupled to FTIR to identify and quantify certain microplastics in environment. Samples were pyrolyzed in TGA and the pyrolysis gases were analyzed by FTIR. Combining TGA and FTIR data adds discriminatory power as temperature profiles and absorption spectra differ among several common plastics. To quantify on a mass basis, we calibrated on characteristic IR peaks at temperatures of maximum weight loss for individual polymers. The method can distinguish PVC, PS and was validated by spiking samples with known quantities of microplastics. The result of field sample experiments showed that TGA-FTIR can be used to identify and quantify PVC and PS in bivalves, seawater and soil. And the method may be applicable to environmental samples.


Assuntos
Plásticos/análise , Espectroscopia de Infravermelho com Transformada de Fourier/métodos , Termogravimetria/métodos , Poluentes Químicos da Água/análise , Animais , Bivalves/química , China , Monitoramento Ambiental/métodos , Plásticos/química , Polímeros/análise , Polímeros/química , Reprodutibilidade dos Testes , Água do Mar/química , Poluentes do Solo/análise , Poluentes do Solo/química , Poluentes Químicos da Água/química
13.
Int J Nanomedicine ; 14: 7309-7322, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31571855

RESUMO

Introduction: The only treatment for aseptic loosening is the replacement of the prosthesis through revision surgery. A preventive approach, achieved through anti-inflammatory drugs released from the device, has shown to be a viable strategy; however, the performance of these devices is not yet satisfactory thus further improvements are necessary. Methods: We used titanium nanoparticles as a model for implant surfaces and developed a coating containing dexamethasone (DEX) using layer-by-layer deposition. Results: The amount of deposited drug depended on the number of layers and the release was sustained for months. The efficiency of the released DEX in reducing inflammation markers (tumor necrosis factor alpha and IL-6) produced by human monocytes and macrophages was similar to the pure drug at the same concentration without negative impacts on the viability and morphology of these cells. Conclusion: These coatings were not inferior to medical grade titanium (the standard material used in uncemented devices) regarding their ability to sustain osteoblasts and fibroblasts growth.


Assuntos
Anti-Inflamatórios/farmacologia , Cimentos para Ossos/farmacologia , Materiais Revestidos Biocompatíveis/farmacologia , Liberação Controlada de Fármacos , Nanopartículas/química , Falha de Prótese , Linhagem Celular , Forma Celular/efeitos dos fármacos , Dexametasona/farmacologia , Fibroblastos/efeitos dos fármacos , Humanos , Interleucina-6/metabolismo , Lipopolissacarídeos/farmacologia , Ativação de Macrófagos/efeitos dos fármacos , Mitocôndrias/efeitos dos fármacos , Mitocôndrias/metabolismo , Monócitos/efeitos dos fármacos , Nanopartículas/ultraestrutura , Osteoblastos/efeitos dos fármacos , Osteoblastos/patologia , Tamanho da Partícula , Termogravimetria
14.
Int J Nanomedicine ; 14: 8149-8159, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31632024

RESUMO

Introduction: Recently several new approaches were emerging in bone tissue engineering to develop a substitute for remodelling the damaged tissue. In order to resemble the native extracellular matrix (ECM) of the human tissue, the bone scaffolds must possess necessary requirements like large surface area, interconnected pores and sufficient mechanical strength. Materials and methods: A novel bone scaffold has been developed using polyurethane (PE) added with wintergreen (WG) and titanium dioxide (TiO2). The developed nanocomposites were characterized through field emission scanning electron microscopy (FESEM), Fourier transform and infrared spectroscopy (FTIR), X-ray diffraction (XRD), contact angle measurement, thermogravimetric analysis (TGA), atomic force microscopy (AFM) and tensile testing. Furthermore, anticoagulant assays, cell viability analysis and calcium deposition were used to investigate the biological properties of the prepared hybrid nanocomposites. Results: FESEM depicted the reduced fibre diameter for the electrospun PE/WG and PE/WG/TiO2 than the pristine PE. The addition of WG and TiO2 resulted in the alteration in peak intensity of PE as revealed in the FTIR. Wettability measurements showed the PE/WG showed decreased wettability and the PE/WG/TiO2 exhibited improved wettability than the pristine PE. TGA measurements showed the improved thermal behaviour for the PE with the addition of WG and TiO2. Surface analysis indicated that the composite has a smoother surface rather than the pristine PE. Further, the incorporation of WG and TiO2 improved the anticoagulant nature of the pristine PE. In vitro cytotoxicity assay has been performed using fibroblast cells which revealed that the electrospun composites showed good cell attachment and proliferation after 5 days. Moreover, the bone apatite formation study revealed the enhanced deposition of calcium content in the fabricated composites than the pristine PE. Conclusion: Fabricated nanocomposites rendered improved physico-chemical properties, biocompatibility and calcium deposition which are conducive for bone tissue engineering.


Assuntos
Osso e Ossos/fisiologia , Poliuretanos/farmacologia , Engenharia Tecidual/métodos , Tecidos Suporte/química , Osso e Ossos/efeitos dos fármacos , Calcificação Fisiológica/efeitos dos fármacos , Cálcio/metabolismo , Sobrevivência Celular/efeitos dos fármacos , Hemólise/efeitos dos fármacos , Humanos , Teste de Materiais , Nanocompostos/química , Nanocompostos/ultraestrutura , Espectroscopia de Infravermelho com Transformada de Fourier , Resistência à Tração , Termogravimetria , Titânio/farmacologia , Molhabilidade , Difração de Raios X
15.
Bioresour Technol ; 294: 122099, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31520856

RESUMO

In this study, the pyrolysis behavior and kinetics of raw biomasses and their pellets were studied by Coats Redfern and DAEM methods. The results demonstrated that the similar activation energies obtained by both methods confirmed accuracy of the kinetics calculation. The activation energy of the pellets was 132.49-232.44 kJ mol-1, slightly higher than those of raw biomasses, which was 120.58-210.55 kJ mol-1. The results from Coats Redfern method showed that the pyrolysis of all the samples were controlled by mass and heat diffusion. DAEM revealed that the activation energies of the pellets were higher than those of raw biomasses during hemicellulose and cellulose decomposition stages, and was opposite for the lignin decomposition stage. Physical structure characterization indicated that the pellets had smaller surface area and more compact surface than those of their raw biomasses. Hence, the mass and heat diffusion were suppressed and more cross-linking reactions occurred during pellets pyrolysis.


Assuntos
Lignina , Pirólise , Biomassa , Cinética , Termogravimetria
16.
Int J Nanomedicine ; 14: 6869-6889, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31507318

RESUMO

Introduction: Biodegradable polymers that contain radioactive isotopes such as Holmium 166 have potential applications as beta particle emitters in tumor tissues. Also, Ho(III) is paramagnetic, which makes it suitable as a contrast agent for magnetic resonance (MR) images. Methods: Holmium acetylacetonate (Ho(acac)3) loaded poly(3-hydroxy-butyrate-co-3-hydroxy-valerate) microspheres, with 5% or 8% of 3-hydroxy-valerate (HV), were prepared by emulsification/evaporation process within 20-53 µm size. Microspheres characterization was done using scanning electron microscopy, energy-dispersive X-ray, and infrared spectroscopies. The release of holmium(III) in sodium phosphate buffer (pH 7.4) was followed for 9 days with inductively coupled plasma. Finally, T2 and T2* magnetic resonance images (MRI) were acquired and compared with the MRI of the inclusion complex of holmium acetylacetonate in some ß-cyclodextrins. Results: Holmium acetylacetonate loading, evaluated by thermogravimetry, was up to 20 times higher for copolymer with 5% of HV. It was shown that microspheres loaded with Ho(acac)3 exhibited an accumulation of Ho(III) on their surfaces but were stable over time, as no expressive release of holmium(III) was detected in 9-day exposition to sodium phosphate buffer. Holmium acetylacetonate in both microspheres or inclusion complexes was very efficient in obtaining T2 and T2* weighted images in magnetic resonance, thus, might be used as contrast agents. Conclusion: This is the first description of the use of inclusion complexes of holmium acetylacetonate in biodegradable polymers as contrast agents. New investigations are underway to evaluate the resistance of PHB-HV polymer microparticles to nuclear activation to assess their potential for use as radiopharmaceuticals for the treatment of liver cancer.


Assuntos
Meios de Contraste/química , Hólmio/química , Hidroxibutiratos/química , Imagem por Ressonância Magnética , Microesferas , Pentanonas/química , Poliésteres/química , Radioisótopos/química , Calibragem , Humanos , Espectrometria por Raios X , Termogravimetria , Difração de Raios X
17.
Waste Manag ; 100: 122-127, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31536922

RESUMO

In the leather industry, considerable amounts of non-recyclable solid leather wastes (SLWs) are produced and accumulated in factories. In this work, the non-isothermal thermochemical analysis (TGA) test was used to analyse the thermal degradation behaviour of chromium-tanned leather shaving, which is one of the main SLWs. The pyrolysis experiments were carried out under nitrogen atmosphere from 30 to 800 °C at different heating rates of 5, 10, 15 and 20 °C/min. Three different kinetic models, including the Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS) and Kissinger methods, were used to calculate the kinetic parameters. The activation energy values calculated by FWO and KAS methods were 391.79 and 348.77 kJ/mol, respectively. In consideration of the high HHV (14.15 MJ/kg) and carbon productivity (10.15%), SLWs could represent a potential candidate material for bioenergy production and carbon preparation. These results could be used for the design of thermochemical conversion processes utilizing SLWs as feedstock.


Assuntos
Pirólise , Resíduos Sólidos , Calefação , Cinética , Termogravimetria
18.
Bioresour Technol ; 294: 122089, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31526932

RESUMO

The aim of this study was to understand the influence of catalyst in thermal degradation behavior of rice husk (RH) in catalytic fast pyrolysis (CFP) process. An iso-conversional Kissinger kinetic model was introduced into this study to understand the activation energy (EA), pre-exponential value (A), Enthalpy (ΔH), Entropy (ΔS) and Gibb's energy (ΔG) of non-catalytic fast pyrolysis (NCFP) and CFP of RH. The study revealed that the addition of natural zeolite catalyst enhanced the rate of devolatilization and decomposition of RH associated with lowest EA value (153.10 kJ/mol) compared to other NCFP and CFP using nickel catalyst. Lastly, an uncertainty estimation was applied on the best fit non-linear regression model (MNLR) to identify the explanatory variables. The finding showed that it had the highest probability to obtain 73.8-74.0% mass loss in CFP of rice husk using natural zeolite catalyst.


Assuntos
Oryza , Cinética , Pirólise , Termodinâmica , Termogravimetria , Incerteza
19.
Waste Manag ; 100: 91-100, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31525677

RESUMO

The replacement of fossil fuels by renewable sources has been discussed globally, because fossil fuels account for a large portion of the pollutant emissions into the atmosphere. Several cities along the Brazilian coast produce a variety of fish types, generating a large amount of waste, including viscera and fish scales, which are already used in several industrial processes. However, these cities still face a large environmental problem, i.e., residue disposal from commercial establishments, e.g., fishmongers, which are often discarded in a disordered and/or unplanned manner in inappropriate places. Within this scenario, the energy utilization of an animal biomass supplied by a fishery in the city of São Luís was investigated, submitting samples to combustion (synthetic air) and pyrolysis (100% N2) processes for the bioenergy generation. Physicochemical properties from fish scales were evaluated by proximate and ultimate analyzes, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-Ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and inductively coupled plasma - optical emission spectroscopy (ICP-OES). The thermal behavior of samples was evaluated by thermogravimetry/derivative thermogravimetry (TG/DTG), differential thermal analysis (DTA) and calorimetry (HHV/LHV). It was verified that the fish scales have carbon and oxygen the major elements, and insignificant amounts of sulfur and heavy metals (lead, copper, chromium, lithium, zinc). This material also presented a large amorphous region (89%), in addition to the presence of collagen fibers and hydroxyapatite crystals. The thermal and physicochemical characteristics of this material were evaluated and compare it to other biomasses already in use, predicting its use for the bioenergy generation.


Assuntos
Combustíveis Fósseis , Animais , Biomassa , Brasil , Cidades , Espectroscopia de Infravermelho com Transformada de Fourier , Termogravimetria
20.
Mater Sci Eng C Mater Biol Appl ; 104: 109845, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31500034

RESUMO

The facile preparation of macroporous, super water absorbing, biocompatible hydrogels of chitosan involving the hydrothermal reaction of a mixture of chitosan (CH), succinic acid (SA) and urea (UR), all of which are sustainable materials, is reported. The structure of the dry CHSAUR was ascertained by CP MAS-SS NMR spectroscopy, Fourier transform infrared (FTIR) spectroscopy, powder x-ray diffraction analysis (PXRD), and thermogravimetric analysis (TGA). The principle role of UR in the synthesis was identified as the source of ammonia, which increased the pH of the acidic chitosan solution with reaction time, leading to the formation of the insoluble hydrogel of chitosan accompanied by the formation of pores of different sizes and volumes. In addition, a small fraction of urea participated in chemical reaction with the primary hydroxyl groups in the sixth position of the glucosamine repeat units of chitosan resulting in carbamate linkages. The as-prepared hydrogel, following workup and methanol extraction, was found to be chitosan crosslinked with succinic acid through electrostatic interaction. It was macroporous with percentage porosity varying between 49.4% to 64.2%. It also exhibited different extents of water uptake with the maximum of 760 ±â€¯20 g/g being for the one prepared with the weight ratio of 1: 4: 4 of chitosan: succinic acid: urea. The absorption of water is found to arise out of the porosity as well as presence of water attracting chitosan ammonium cation-succinate electrovalent bonds that are formed by the reaction between SA and ammonium cation of the chitosan backbone. The absorption of saline water was relatively poor suggesting that the saline water absorption might be arising largely due to the presence of micropores and specific interaction. The hydrogels exhibited Herschel-Bulkley rheological behavior. The extraction of CHSAUR with 0.1 N NaOH in methanol resulted in the removal of the physical crosslinks, consisting of succinate anions; the presence of chitosan with porous morphology was confirmed additionally by copper (+2) adsorption. In contrast to the widely reported method of preparing microporous chitosan scaffold of cylindrical shape that takes several days to a week, the present method offers a simple means of preparing macroporous chitosan of any shape and size in very large scale with soft foam-like morphology. With its biocompatibility towards mouse fibroblast cells it could find applications in drug delivery, biodegradable super water absorbency and haemostatic applications.


Assuntos
Materiais Biocompatíveis/síntese química , Quitosana/química , Hidrogéis/síntese química , Temperatura Ambiente , Ureia/química , Água/química , Células 3T3-L1 , Animais , Sobrevivência Celular , Reagentes para Ligações Cruzadas/química , Hidrogéis/química , Espectroscopia de Ressonância Magnética , Camundongos , Porosidade , Reologia , Espectroscopia de Infravermelho com Transformada de Fourier , Termogravimetria , Viscosidade , Difração de Raios X , Microtomografia por Raio-X
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