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1.
Artículo en Inglés | MEDLINE | ID: mdl-39251537

RESUMEN

This study focused on investigating thermal degradation behaviors, kinetics, reaction mechanisms, synergistic effects, and thermodynamic parameters of wood sawdust (WSD), linear low-density polyethylene (LLDPE), and their blends (LW1:3, LW1:1, and LW3:1) during co-pyrolysis in a thermogravimetric analyzer (TGA). Thermal behavior exhibited a LW1:3 blend (25 wt.% LLDPE) showing significant mass loss at lower temperatures (150 to 300 °C) compared to the individual feedstocks, such as 150 to 400 °C and 300 to 520 °C for WSD and LLDPE, respectively. The iso-conversional methods (KAS, FWO, and FM) were used to determine the kinetic parameters (Ea and A), and the activation energy drop was highest for the LW1:3 blend. According to the master plots, the third-order reaction (O3), nucleation (P2/3), and diffusional model (D4) were the predominant reaction mechanisms for the co-pyrolysis of the LW1:3, LW1:1, and LW3:1 blend, respectively. The thermodynamic parameters demonstrate that a small amount of plastic addition into WSD can improve the reactivity of the blend, shorten the reaction time, and cause less energy-intensive reactions. The values of ΔH, ΔG, and ΔS also confirmed the co-pyrolysis process's spontaneity and endothermic nature. The Fourier transforms infrared spectrometer (FTIR) spectra of raw feedstock, blends, and their biochar revealed some of the peaks were shifted, the intensity was reduced, and disappearance can happen when the temperature was increased. Using the experimental and theoretical/predicted activation energies, the parity chart illustrates the synergistic effects of co-pyrolysis of different blends, and the LW1:3 blend has a favorable synergistic impact. These results could be helpful in process optimization and designing an effective reactor system for co-pyrolysis.

2.
Appl Radiat Isot ; 212: 111473, 2024 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-39167985

RESUMEN

The study of complex phases in nuclear fuels is necessary to understand the physicochemical properties of the fuel. Na6Mo7O24⋅14H2O (1) was prepared via a simplified method and the crystal structure was improved. Upon thermal degradation, 1 decomposes into Na2Mo2O7 and MoO3. Additionally, novel Ba3Mo7O24⋅12H2O (2) was isolated via an aqueous synthetic route and characterized via FTIR and elemental analysis. PXRD pattern of 2 was determined. Thermal degradation of 2 indicates formation of BaMoO4, BaMo3O10, MoO3, and an unidentified phase.

3.
Materials (Basel) ; 17(9)2024 Apr 23.
Artículo en Inglés | MEDLINE | ID: mdl-38730747

RESUMEN

Cementitious materials are used to construct an engineered barrier in repositories for radioactive waste. The cement matrix may contain a variety of organic compounds, some of which are polymeric admixtures used as plasticizers. Superplasticizers (SPs) are highly effective organic cement additives for reducing water amount, increasing workability, homogeneity, plasticity and the non-segregation of mortars and grouts, improving mechanical properties and resistance to destructive environments. SPs in cement could have an impact on the long-term safety of the disposals of radioactive waste. These organic agents can leach from the cementitious matrix into groundwater and may affect the migration behaviour of radionuclides. The detailed chemical composition and other characteristics of the cement (CEM I 42.5 R, Sweden) used for the leaching experiments were evaluated. It contained mainly CaO (52.51 ± 1.37, %), and the surface area of the cement particles was 13.2 ± 1.3 m2/g. An insignificant increase in pH (from 12.6 ± 0.1 to 12.8 ± 0.1) was observed for the leachates over 10 days. A commercially available cement superplasticizer based on polymelamine sulphonate (PMS) Peramin SMF10 (Peramin AB, Sweden) was chosen for the research. The product's chemical composition was analysed using wavelength-dispersive X-ray fluorescence (WD-XRF) spectroscopy, while other physico-chemical properties of the PMS superplasticizer were assessed by Raman spectroscopy and thermo-gravimetric analysis. In aqueous solutions and powders of PMS, the same most intensive features were observed at 774 cm-1 (ring out-of-plane deformation), 977 cm-1 (C-N-C bending, SO stretching) and 1055 cm-1 (C-N=C bending) in the Raman spectra. At up to 270 °C, the polymer was thermally stable. Raman and UV/Vis spectroscopies were used to assess the rate of the alkaline degradation of PMS superplasticizer in different aqueous solutions. No changes were observed in the hydrolytic solutions with any of the above analytical methods over a period of 3 years. The results obtained revealed a good thermal and chemical stability (in highly alkaline media, pH = 9.9-12.9) of the PMS polymer.

4.
Heliyon ; 10(1): e23840, 2024 Jan 15.
Artículo en Inglés | MEDLINE | ID: mdl-38192763

RESUMEN

Metal-organic frameworks (MOFs) are promising materials offering exceptional performance across a myriad of applications, attributable to their remarkable physicochemical properties such as regular porosity, crystalline structure, and tailored functional groups. Despite their potential, there is a lack of dedicated reviews that focus on key physicochemical characterizations of MOFs for the beginners and new researchers in the field. This review is written based on our expertise in the synthesis and characterization of MOFs, specifically to provide a right direction for the researcher who is a beginner in this area. In this way, experimental errors can be reduced, and wastage of time and chemicals can be avoided when new researchers conduct a study. In this article, this topic is critically analyzed, and findings and conclusions are presented. We reviewed three well-known XRD techniques, including PXRD, single crystal XRD, and SAXS, which were used for XRD analysis depending on the crystal size and the quality of crystal morphology. The TGA profile was an effective factor for evaluating the quality of the activation process and for ensuring the successful investigation for other characterizations. The BET and pore size were significantly affected by the activation process and selective benzene chain cross-linkers. FTIR is a prominent method that is used to investigate the functional groups on pore surfaces, and this method is successfully used to evaluate the activation process, characterize functionalized MOFs, and estimate their applications. The most significant methods of characterization include the X-ray diffraction, which is utilized for structural identification, and thermogravimetric analysis (TGA), which is used for exploring thermal decomposition. It is important to note that the thermal stability of MOFs is influenced by two main factors: the metal-ligand interaction and the type of functional groups attached to the organic ligand. The textural properties of the MOFs, on the other hand, can be scrutinized through nitrogen adsorption-desorption isotherms experiments at 77 K. However, for smaller pore size, the Argon adsorption-desorption isotherm at 87.3 K is preferred. Furthermore, the CO2 adsorption isotherm at 273 K can be used to measure ultra-micropore sizes and sizes lower than these, which cannot be measured by using the N2 adsorption-desorption isotherm at 77 K. The highest BET was observed in high-valence MOFs that are constructed based on the metal-oxo cluster, which has an excellent ability to control their textural properties. It was found that the synthesis procedure (including the choice of solvent, cross-linker, secondary metal, surface functional groups, and temperature), activation method, and pressure significantly impact the surface area of the MOF and, by extension, its structural integrity. Additionally, Fourier-transform infrared spectroscopy plays a crucial role in identifying active MOF functional groups. Understanding these physicochemical properties and utilizing relevant characterization techniques will enable more precise MOF selection for specific applications.

5.
Chemosphere ; 343: 140225, 2023 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-37742771

RESUMEN

Polypropylene composites find widespread application in industries, including packaging, plastic parts, automotive, textiles, and specialized devices like living hinges known for their remarkable flexibility. This study focuses on the manufacturing of polypropylene composite specimens by incorporating varying weight percentages of fly ash particles with polypropylene using a twin-screw extruder and injection molding machine. The composites were comprehensively tested, evaluating tensile, compressive, and flexural strength, solid-state and polymer melt properties, modulus, damping, and thermal response. The findings reveal that the compressive strength of polypropylene increases up to 2 wt% of added fly ash particles and subsequently exhibits a slight decline. Tensile strength demonstrates an increase up to 1 wt% of fly ash, followed by a decrease with a 2 wt% addition, and then a subsequent increase. Flexural strength shows improvement up to 3 wt% fly ash addition before declining. The storage modulus curve is categorized into three regions: the glassy region (up to 0 °C), the glass transition region (0-50 °C), and the glass transition region of polypropylene (>50 °C), each corresponding to different molecular motions. Weight loss curves exhibit similar trends, indicating uniform pyrolysis behavior attributed to consistent chemical bonds. Plastic degradation commences around 440 °C and concludes near 550 °C. Additionally, elemental mapping of fly ash composition identified various elements such as O, Si, K, Mg, Ca, Cl, Na, P, Al, Fe, S, Cu, Ti, and Ni. These findings offer valuable insights into the mechanical and thermal properties of polypropylene composites reinforced with fly ash, rendering them suitable for a wide range of industrial applications necessitating strength and durability across temperature variations.

6.
Int J Biol Macromol ; 186: 125-134, 2021 Sep 01.
Artículo en Inglés | MEDLINE | ID: mdl-34246666

RESUMEN

Marine microorganisms are reported to produce polyhydroxybutyrate (PHB) that has wide range of medical and industrial applications with the advantage of biodegradability. PHBs are synthesized as an energy and carbon storage element under metabolic pressure. The scope of this work is enhancing PHB production using marine microbial isolate, Micrococcus luteus by selectively optimizing various growth conditions such as different media components and growth parameters that influence the cell growth and PHB production were sampled. Micrococcus luteus produced 7.54 g/L of PHB utilizing glucose as a carbon source and ammonium sulphate as a nitrogen source with maximum efficiency. The same optimized operational conditions were further employed in batch fermentation over a time span of 72 h. Interestingly higher cell dry weight of 21.52 g/L with PHB yield of 12.18 g/L and 56.59% polymer content was observed in batch fermentation studies at 64 h. The chemical nature of the extracted polymer was validated with physio-chemical experiments and was at par with the commercially available PHB. This study will spotlight M. luteus as a potential source for large-scale industrial production of PHB with reducing environmental pollutions.


Asunto(s)
Butiratos/metabolismo , Sedimentos Geológicos/microbiología , Hidroxibutiratos/aislamiento & purificación , Microbiología Industrial , Micrococcus luteus/metabolismo , Butiratos/química , Fermentación , Concentración de Iones de Hidrógeno , Micrococcus luteus/crecimiento & desarrollo , Estructura Molecular , Temperatura , Factores de Tiempo
7.
Environ Sci Pollut Res Int ; 28(45): 63516-63522, 2021 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-32748356

RESUMEN

Biomass waste contributes 14% of the total global energy. And 15-20% of the coal-fine waste from coal mines are deposited in the rivers, ponds, etc., unused, which leads to resource wastage and environmental pollution. The present study aims utilizing biomass and coal-fine waste for producing biomass-coal briquettes without using a binding material. Three different average sizes 50, 134.3, and 199.7 µm of biomass mixture (bagasse, groundnut shell, and woodchips) and coal-fines were used to make different ratios of biomass and coal mixture briquettes. Then, it is subjected to proximate, scanning electron microscope/elemental (SEM/EDX) and thermo-gravimetric analysis (TGA) to understand its property. Proximate analysis results revealed that the biomass waste has the low ash, sensible fixed carbon, and high volatile matter content. A briquette of biomass: coal = 7:1 ratio 50-µm particle size case was chosen for SEM/EDX and TGA analysis since it holds reasonable fixed carbon value comparatively. SEM analysis revealed irregular surfaces, cracks, cavities and longitudinal cracks, veins distribution all around, ups and shallows on the surface and it is the most favorable condition for fuel combustion since oxidant reaches the core of the fuel with less resistant. TGA reconfirms the spontaneous burning characteristics of the entire volatiles and fixed carbon. EDX analysis shows that the carbon and potassium are the two major elements present in the tested briquettes.


Asunto(s)
Carbono , Carbón Mineral , Biomasa , Energía Renovable , Termogravimetría
8.
Recent Pat Nanotechnol ; 14(4): 351-359, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-32875993

RESUMEN

Drug delivery for a long time has been a major problem in the pharmaceutical field. The development of a new Nano-carrier system called nanosponge has shown the potential to solve the problem. Nanosponge has a porous structure and can entrap the drug in it. It can carry both hydrophilic and hydrophobic drugs. They also provide controlled release of the drugs and can also protect various substances from degradation. Nanosponge can increase the solubility of drugs and can also be formulated into an oral, topical and parenteral dosage form. The current review explores different preparation techniques, characterization parameters, as well as various applications of nanosponge. Various patents related to nanosponge drug delivery system have been discussed in this study.


Asunto(s)
Sistemas de Liberación de Medicamentos , Nanopartículas/química , Animales , Liberación de Fármacos , Humanos , Nanopartículas/ultraestructura , Tamaño de la Partícula , Patentes como Asunto , Polímeros/química
9.
Waste Manag ; 117: 114-123, 2020 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-32823076

RESUMEN

Safe disposal of the sludge generated from sewage treatment plant is a major challenge worldwide. Hydrothermal carbonization (HTC) is considered a potential pretreatment alternative for sewage sludge to facilitate the improved resource recovery. In the present study, the mixed centrifuged sewage sludge (CSS) was subjected to the HTC pretreatment to determine characteristics of the solid hydrochar (HC) and liquid fraction (LF) with a purpose of energy recovery and extraction of value-added compounds, respectively. HTC was performed in a high pressure batch reactor at 200 °C temperature for 1-8 h duration. The HC produced after HTC resembled with the low quality peat coal whereas the LF contained value-added chemicals such as humic acid (HA) and phosphate phosphorous (PO43-P). Using ammonium sulphate as 'salting out' agent, ~70% of the total HA (~15-16 g/L) could be recovered from the LF. Using the recovered HA, an improvement in the root and shoot lengths of the seeds could be observed. In the subsequent step, the total PO43--P recovery of ~80% was obtained as struvite from the residual wastewater.


Asunto(s)
Aguas del Alcantarillado , Aguas Residuales , Carbono , Fosfatos , Fósforo , Estruvita
10.
Molecules ; 25(10)2020 May 21.
Artículo en Inglés | MEDLINE | ID: mdl-32455570

RESUMEN

Here we focus on the thermal and variable temperature electrochemical stabilities of two ionic liquids (ILs) having a common tributyloctyl phosphonium cation [P4,4,4,8]+ and two different orthoborate anions: bis(mandelato)borate [BMB]- and bis(salicylato)borate [BScB]-. The thermo-gravimetric analysis data suggest that [P4,4,4,8][BScB] is thermally more stable than [P4,4,4,8][BMB] in both nitrogen atmosphere and air, while the impedance spectroscopy reveals that [P4,4,4,8][BScB] has higher ionic conductivity than [P4,4,4,8][BMB] over the whole studied temperature range. In contrast, the electrochemical studies confirm that [P4,4,4,8][BMB] is more stable and exhibits a wider electrochemical stability window (ESW) on a glassy carbon electrode surface as compared to [P4,4,4,8][BScB]. A continuous decrease in the ESWs of both ILs is observed as a function of operation temperature.


Asunto(s)
Aniones/química , Electroquímica , Líquidos Iónicos/química , Boratos/química , Conductividad Eléctrica , Calor/efectos adversos , Temperatura
11.
Materials (Basel) ; 13(7)2020 Apr 06.
Artículo en Inglés | MEDLINE | ID: mdl-32268537

RESUMEN

Flame retardant cables were investigated using thermo-gravimetric analysis to measure the reference temperature and reference rate required for a fire spread simulation using a Fire Dynamics Simulator (FDS). Sensitivity analysis was also performed to understand the effects of the reference temperature and rate on the pyrolysis reactions. A two-step pyrolysis reaction was typically observed regardless of the cable type, and each pyrolysis reaction could be attributed to single or multiple components depending on the cable type and reaction order. Although the structures, compositions, and insulation performances of the cables differed considerably, the reference temperatures of the two-step pyrolysis reaction were extremely similar regardless of the cable type. Conversely, the reference rates of the different types of cables varied significantly. The sensitivity analysis results indicate that the mean values of the reference temperature and rate are sufficient to simulate the pyrolysis reactions of flame retardant cables. The results obtained herein also suggest that the heat transfer and pyrolysis reaction path associated with the multi-layered cable structure may be more important for accurately determining the ignition and fire spread characteristics, which are attributable to differences in cable structure, composition, and insulation performance.

12.
Waste Manag Res ; 38(6): 689-695, 2020 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-32026752

RESUMEN

We report here alumina-substituted Keggin tungstoborate/kaolin clay composite materials (KAB/kaolin) as polyethylene cracking catalysts. KAB/kaolin composites with varying concentrations of KAB (10-50 wt.%) were synthesized by the wet impregnation method and successfully characterized by Fourier-transform infrared spectroscopy, powder X-ray diffraction, thermo-gravimetric analysis and scanning electron microscopy with energy dispersive X-ray spectroscopy analytical techniques. Use of KAB loaded kaolin composites as the catalyst for low-density polyethylene (LDPE) cracking exhibited a higher percentage of polymer conversion (99%), producing 84 wt.% of fuel oil and negligible amount (˂ 1 wt.%) of solid residue while thermal cracking produced ~22 wt.% residue. Furthermore, gas chromatography-mass spectrometry analysis of oil obtained by non-catalytic cracking exhibited a high selectivity to high molecular weight hydrocarbons (C13-C23) compared to the catalytic cracking where 70 mol.% of gasoline range hydrocarbons (C5-C12) were produced. We propose that higher cracking ability of our prepared catalysts might ensue from both Brønsted and Lewis acid sites (from KAB and kaolin respectively), which enhanced the yield of liquid fuel products and reduced the cracking temperature of LDPE. These findings suggest that the prepared composites were cost-effective and excellent cracking catalysts that could be recommended for highly efficient conversion of waste plastic materials to petrochemicals at an industrial scale.


Asunto(s)
Caolín , Polietileno , Catálisis , Pirólisis , Compuestos de Tungsteno
13.
J Environ Manage ; 240: 293-302, 2019 Jun 15.
Artículo en Inglés | MEDLINE | ID: mdl-30953982

RESUMEN

This study investigated the dual application of Scenedesmus obliquus for wastewater phycoremediation and biochemical component accumulation in microalgal cells. The microalgae grown in wastewater showed micro-elements uptake and removal efficiencies of 71.2 ±â€¯3.5% COD, 81.9 ±â€¯3.8% NH4+, ∼100.0% NO3-, and 94.1 ±â€¯4.7% PO43-. The growth profile of Scenedesmus obliquus indicated a specific growth rate of 0.42 ±â€¯0.02 1·d-1 and carrying capacity of 0.88 ±â€¯0.04 g L-1. The lipid, protein, and carbohydrate yields (w·w-1 of dry weight) were 26.5 ±â€¯1.5%, 28.5 ±â€¯1.5%, and 27.5 ±â€¯1.6%, respectively. The de-oiled biomass was subjected to biochemical extraction, achieving protein and carbohydrate yields of 25.3 ±â€¯1.4% and 21.4 ±â€¯1.2%, respectively. Fourier transform infrared spectroscopy showed several functional groups (e.g., NH, CH3, CH2, CO, CN, PO, and SiO) on the biomass surface, confirming the accumulation of biochemical elements in microalgae. The thermal analysis of microalgal biomass depicted sequential stages of dehydration (60-190 °C), devolatilization (200-490 °C), and solid residue decomposition (490-600 °C). The cost-benefit analysis of microalgae cultivated in wastewater was derived regarding amortization and operating costs and energy and environmental benefits. The net profit of phycoremediation was 16885 US$·y-1, resulting in a payback period of 14.8 years (i.e., shorter than the project lifetime). Accordingly, the proposed phycoremediation process was economically viable.


Asunto(s)
Microalgas , Scenedesmus , Biocombustibles , Biomasa , Aguas Residuales
14.
Materials (Basel) ; 12(3)2019 Feb 05.
Artículo en Inglés | MEDLINE | ID: mdl-30764508

RESUMEN

In this investigation, the age-dependent hydration development of blended pastes containing Portland cement (PC), pulverized fuel ash (PFA) and silica fume (SF) was assessed by quantifying the amount of CH and non-evaporable water using thermo-gravimetric analysis (TGA). Microstructure was investigated using scanning electron microscope (SEM). It was observed that the amount of liberated CH increases up to three-days in PC-PFA binary blended pastes, after which it progressively decreases and this reduction was proportional to the PFA dosage. The introduction of SF to PC-PFA binary mixtures to form ternary blended pastes has caused an early reduction of CH at one day where the majority of SF has been consumed during the first seven-days. The incorporation of 10% SF to PC-PFA pastes altered the low rate of hydration at early age. In addition, the presence of PFA showed insignificant influence on the non-evaporable water content until three-days then its effect became significant after seven-days. On the other hand, SF increased the non-evaporable water content from early ages up to seven-days. However, beyond 28 days, the presence of SF did not exhibit further pozzolanic activity. Furthermore, the ternary blended systems significantly increased the non-evaporable water content within three to seven days compared to the reference paste. Moreover, prediction nonlinear models of these hydration parameters were developed using the simplex-lattice design and validated against the experimental results. The latter have been further supported with SEM microstructural analysis showing good agreement between the predicted and realistic hydration.

15.
Environ Sci Pollut Res Int ; 25(33): 33140-33152, 2018 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-30251046

RESUMEN

The disodium salt of Rose Bengal [4, 5, 6, 7-tetrachloro-2', 4', 5', 7'-tetraiodofluorescein] commonly finds application in medical procedures and its removal from aqueous solution is difficult owing to its high molecular weight of 1017.67 g/mol. Activated carbon was prepared from Prosopis juliflora and immobilized into sodium alginate beads and doped with aniline for enhanced adsorption of Rose Bengal. The effect of initial dye concentration, beads' dosage, contact time, and the temperature over the adsorption of Rose Bengal dye were studied. The optimum conditions derived for maximum dye uptake capacity were 4 mg/L of initial dye concentration, contact time of 60 min with the adsorbent dosage of 0.2 g, and temperature of 303 K at neutral pH. The equilibrium data were found to be best fitted for Langmuir -1 model, whereas the kinetics were interpreted through Ho-Mckay's pseudo-second-order equation. The adsorbents were subjected to thermo-gravimetric studies to determine the activation energy under a heating rate of 20 °C/min. The activation energy was computed using Broido's plot and was found to be 35.21 ± 0.84 kJ/mol for the activated carbon, and 16.77 ± 2.19 kJ/mol for the dye-adsorbed beads. The heat capacity was determined through differential scanning calorimetry and was calculated to be 19.41 J/g °C for activated carbon and 39.43 J/g °C for beads post-adsorption of Rose Bengal dye.


Asunto(s)
Alginatos/química , Carbón Orgánico/química , Colorantes/química , Fuentes Generadoras de Energía , Prosopis/química , Administración de Residuos/métodos , Adsorción , Estudios de Factibilidad , Cinética , Termodinámica , Termogravimetría
16.
J Food Sci Technol ; 55(6): 2130-2142, 2018 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-29892114

RESUMEN

In this study, the effects of different pulverizing methods on the chemical attributes and thermal properties of black, white and green pepper were evaluated. Cryogenic grinding minimally damaged the lipid, moisture, crude protein, starch, non-volatile ether extract, piperine, essential oil and the typical pepper essential oil compounds of the spices. The pulverizing methods and storage significantly affected the compositions of the fatty acid in the peppers, except for palmitic acid and lignoceric acid. The amino acid contents and the thermo-gravimetric analysis curve were hardly influenced by the grinding techniques. The use of cryogenic grinding to prepare pepper ensured the highest quality of pepper products. Regardless of grinding technique, the values of moisture, piperine, unsaturated fatty acids, essential oil, monoterpenes, and the absolute concentrations of typical pepper essential oil constituents (except caryophyllene oxide) decreased, whereas the amino acid, lipid, protein, starch, and non-volatile ether extract content as well as the thermal properties were insignificantly changed after storage at 4 °C for 6 months.

17.
Chem Cent J ; 11(1): 49, 2017 May 31.
Artículo en Inglés | MEDLINE | ID: mdl-29086833

RESUMEN

Morphologically controlled synthesis of ferric oxide nano/micro particles has been carried out by using solvothermal route. Structural characterization displays that the predominant morphologies are porous hollow spheres, microspheres, micro rectangular platelets, octahedral and irregular shaped particles. It is also observed that solvent has significant effect on morphology such as shape and size of the particles. All the morphologies obtained by using different solvents are nearly uniform with narrow size distribution range. The values of full width at half maxima (FWHM) of all the products were calculated to compare their size distribution. The FWHM value varies with size of the particles for example small size particles show polydispersity whereas large size particles have shown monodispersity. The size of particles increases with decrease in polarity of the solvent whereas their shape changes from spherical to rectangular/irregular with decrease in polarity of the solvent. The catalytic activities of all the products were investigated for both dry and wet processes such as thermal decomposition of ammonium per chlorate (AP) and reduction of 4-nitrophenol in aqueous media. The results indicate that each product has a tendency to act as a catalyst. The porous hollow spheres decrease the thermal decomposition temperature of AP by 140 °C and octahedral Fe3O4 particles decrease the decomposition temperature by 30 °C. The value of apparent rate constant (kapp) of reduction of 4-NP has also been calculated.

18.
Materials (Basel) ; 10(2)2017 Jan 26.
Artículo en Inglés | MEDLINE | ID: mdl-28772470

RESUMEN

Red pottery clay (RPC) was modified using a silane coupling agent, and the modified RPC (mRPC) was then used to enhance the performance of high-density polyethylene-based wood-plastic composites. The effect of the mRPC content on the performances of the composites was investigated through Fourier transform infrared spectrometry, differential mechanical analysis (DMA) and ultraviolet (UV)-accelerated aging tests. After adding the mRPC, a moisture adsorption hysteresis was observed. The DMA results indicated that the mRPC effectively enhanced the rigidity and elasticity of the composites. The mRPC affected the thermal gravimetric, leading to a reduction of the thermal degradation rate and a right-shift of the thermal degradation peak; the initial thermal degradation temperature was increased. After 3000 h of UV-accelerated aging, the flexural strength and impact strength both declined. For aging time between 0 and 1000 h, the increase in amplitude of ΔL* (luminescence) and ΔE* (color) reached a maximum; the surface fading did not became obvious. ΔL* and ΔE* increased more significantly between 1000 and 2000 h. These characterization results indicate that the chromophores of the mRPC became briefly active. However, when the aging times were higher than 2000 h, the photo-degradation reaction was effectively prevented by adding the mRPC. The best overall enhancement was observed for an mRPC mass percentage of 5%, with a storage modulus of 3264 MPa and an increase in loss modulus by 16.8%, the best anti-aging performance and the lowest degree of color fading.

19.
Int J Pharm ; 530(1-2): 364-376, 2017 Sep 15.
Artículo en Inglés | MEDLINE | ID: mdl-28779986

RESUMEN

Commercial grades of magnesium stearate have been analysed by nitrogen adsorption having been pre-treated at temperatures between 30°C and 110°C and in the as-received state. Characteristics of nitrogen adsorption/desorption isotherms are assessed through the linearity of low relative pressure isotherm data and the BET transform plot together with the extent of isotherm hysteresis. Comparison is made between thermal gravimetric analysis and mass loss on drying. Features of gas adsorption isotherms considered atypical are identified and possible causes presented. It is shown that atypical isotherm features and issues of applying BET theory to the calculation of SBET are linked to the presence of hydrated water and that these depend on the hydration state: being more pronounced for the di-hydrate than the mono-hydrate. Dehydration reduces the extent of atypical features. SBET of a mono-hydrate sample is 5.6m2g-1 and 3.2m2g-1 at 40°C and 100°C degassing respectively but 23.9m2g1 and 5.9m2g-1 for di-hydrate containing samples under comparable degassing. Di-hydrated samples also show SBET >15m2g1, BET C-values <7 and BET correlation coefficients <0.98 before dehydration. Possible mechanisms for atypical isotherms are critically discussed together with the suitability of applying BET theory to nitrogen adsorption data.


Asunto(s)
Magnesio/química , Nitrógeno/química , Ácidos Esteáricos/química , Adsorción , Agua
20.
J Food Sci Technol ; 54(4): 973-986, 2017 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-28303048

RESUMEN

Rice bean (Vigna umbellata) is grown in South and Southeast Asia, and the bean has gained importance due to its nutritional strength in terms of dietary fiber, quality protein and minerals. In current study, the nutritional and functional components, cooking and thermo-gravimetric properties of eleven rice bean varieties from NE India were investigated. Results revealed that the major nutrients among the varieties ranged as follows: 54.21-60.49% carbohydrates, 15.64-21.60% protein, 1.22-2.3% fat, 5.53-6.56% crude fibre, 3.34-3.8% ash; while the functional, anti-nutritional factors and mineral were present as 1189.32-1645.8 mg gallic acid equivalent (GAE)/100 g polyphenols, 205.38-432.14 mg/100 g phytic acid, 23.14-34.12 mg/100 g oxalate, 690.7-1589.5 mg/100 g saponins, 49.90-158.17 µg/100 g hydrocyanide, 111.51-168 calcium, 5.50-10.44 zinc, 3.72-8.37 iron. Principal component analysis revealed that varieties with higher calcium, iron and ash content had lower cooking time, swelling ratio, and cooked grain hardness. It is also revealed that varieties with higher weight loss at sixth stage in thermogravimetric graph had lower carbohydrate and higher protein content. Nagadal variety had higher fat, potassium, magnesium, calcium, sodium, iron, copper and chromium content and better cooking quality as compared to the other varieties. The study revealed that Nagadal variety was superior to other varieties with respect to mineral content, cooking and thermal properties and hence have better potential in the development of value added products.

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