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Abstract  

The uranium(VI) biosorption by grapefruit peel was studied from aqueous solutions. Batch experiments was conducted to evaluate the effect of contact time, initial uranium(VI) concentration, initial pH, adsorbent dose, salt concentration and temperature. The equilibrium process was well described by the Langmuir, Redlich–Peterson and Koble–Corrigan isotherm models, with maximum sorption capacity of 140.79 mg g−1 at 298 K. The pseudo second order model and Elovish model adequately describe the kinetic data in comparison to the pseudo first order model and the process involving rate-controlling step is much complex involving both boundary layer and intra-particle diffusion processes. The effective diffusion parameter D i and D f values were estimated at different initial concentration and the average values were determined to be 1.167 × 10−7 and 4.078 × 10−8 cm2 s−1. Thermodynamic parameters showed that the biosorption of uranium(VI) onto grapefruit peel biomass was feasible, spontaneous and endothermic under studied conditions. The physical and chemical properties of the adsorbent were determined by SEM, TG-DSC, XRD and elemental analysis and the nature of biomass–uranium (VI) interactions was evaluated by FTIR analysis, which showed the participation of COOH, OH and NH2 groups in the biosorption process. Adsorbents could be regenerated using 0.05 mol L−1 HCl solution at least three cycles, with up to 80% recovery. Thus, the biomass used in this work proved to be effective materials for the treatment of uranium (VI) bearing aqueous solutions.

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Abstract

Mesoporous silica KIT-1 supported with active polytungstophosphate anion of PW x O y species was synthesized and successfully used to catalyze the alkene epoxidation in the environmentally benign solvent of ethyl acetate. The immobilized catalyst of KIT-N+-PW x O y was stable and robust for the epoxidation. In addition, the active species of PW x O y , the molecular sieve support of KIT-1 and the immobilized catalyst of KIT-N+-PW x O y were characterized by FT-IR, UV–vis, XRD, 31P MAS NMR, SEM, N2 adsorption/desorption, ICP and XPS in detail.

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Abstract  

The reaction of urea with ZnO was investigated by FTIR and TPD. It was found that urea was thermally decomposed into isocyanic acid on ZnO, and the adsorbed isocyanic acid reacted with ZnO to form zinc isocyanate. Catalytic evaluation showed that ZnO had high activity towards urea methanolysis in a batch reactor, and zinc element and isocyanate were all detected in the product solution. Furthermore, the soluble zinc content was proportional to the DMC yield. Sample analyses suggested that the soluble zinc existed in the form of Zn(NCO)2(NH3)2, which originated from the reaction of ZnO with urea. It was the complex (not ZnO) that catalyzed the urea methanolysis. Based on these observations, a possible mechanism was suggested.

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Abstract  

The enthalpies of solution of potassium chloride (KCl) in water and magnetically treated water (magnetized water) have been measured at 298.15 K using a LKB-8700 precision solution calorimeter. From the experimental results, it was observed that the effect of magnetic field on the enthalpy of solution is measurable. This is probably due to the distortion of the hydrogen bond of water resulting from magnetic treatment.

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Abstract

In this study, the solid-state shear pan-milling was employed to prepare a series of polymer/layered silicate (PLS) nanocomposites. During the process of pan-milling at ambient temperature, poly(vinyl alcohol)/organic montmorillonite (PVA/OMMT) can be effectively pulverized, resulting in coexistence of intercalated and exfoliated OMMT layers. The obtained PLS nanocomposites were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). TEM analysis indicated that OMMT dispersed homogeneously in PVA matrix and XRD results illustrated that pan-milling had an obvious effect on increase in the interlayer spacing of OMMT, and resulted in coexistence of intercalated and exfoliated OMMT layers formed. Thermal gravimetric analysis showed that thermal stability of PVA was improved owing to the incorporation of OMMT. Thermal decomposition kinetics of PVA/OMMT nanocomposites with different milling cycles of OMMT was also studied. Two types of OMMT are chosen to compare the effect of hydrophilicity of OMMT on PVA/OMMT nanocomposites.

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Abstract

A facile and reusable catalytic system for alcohol oxidation with hydrogen peroxide was designed based on a temperature-responsive catalyst. Several kinds of alcohols were efficiently oxidized in high yields under relatively mild conditions. The catalyst could be easily recovered and reused.

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Abstract

A novel temperature-controlled phase transfer catalytic system based on [(C18H37)2(CH3)2N]7[PW11O39] for olefin epoxidation was demonstrated. The reaction was conducted in a non-chlorinated solvent of ethyl acetate with hydrogen peroxide. The catalyst was easily recovered and reused even ten cycles without loss in activity and selectivity.

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Abstract

The CO2 adsorption capacity of the low-cost solid sorbents of waste tire char (TC) and chicken waste char (CW) was compared with commercial active carbon (AC) and 5 Å zeolite (ZA) using thermogravimetric analysis (TG), pressurized TG, and differential scanning calorimetry (DSC). The sorbents were degassed in a TG up to 150 °C to release all gases on the surface of the sample, then cooled down to the designed temperature for adsorption. TG results indicated that the CO2 adsorption capacity of TC was higher than that of CW, but lower than those of AC and ZA. The maximum adsorption rate of TC at 50 °C was 0.61% min−1, lower than that of AC, but higher than that of CW, 0.44% min−1. The maximum adsorption rate of ZA at 50 °C was 3.1% min−1. When the pressure was over 4 bar, the adsorption rate of ZA was lower than that of TC and AC. At 30 bar, the total CO2 uptake of TC was 20 wt%, higher than that of CW and ZA but lower than that of AC. The temperature, nitrogen concentration, and water content also influenced the CO2 adsorption capacity of sorbents to some extent. DSC results showed that adsorption was an exothermic process. The heat of CO2 adsorption per mole of CO2 of TC at 50 °C was 24 kJ mol−1 while the ZA had the largest heat of adsorption at 38 kJ mol−1. Comparing the characteristics of TC and CW, TC may be a promising sorbent for removal of CO2.

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Abstract

A series of CuO–V2O5/Al2O3 catalysts were prepared and characterized by various techniques such as XRF, BET, XPS and XRD. These catalysts were used for liquid-phase amination of toluene to toluidines. It was found that adding copper species to V2O5/Al2O3 catalyst showed a peculiar behavior, maintaining a high activity toward toluene amination. An optimum CuO content appeared at 1.6 wt% with a CuO/V2O5 molar ratio of 0.25. More than 60% total yield of toluidines was obtained over 1.6%CuO–15%V2O5/Al2O3 catalyst under optimized conditions. Catalyst characterizations revealed that the addition of copper improved the formation of V5+ species, thus enhancing the activity of the catalyst.

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Journal of Thermal Analysis and Calorimetry
Authors:
Hou-yin Zhao
,
Yan Cao
,
Song P. Sit
,
Quentin Lineberry
, and
Wei-ping Pan

Abstract

The pyrolysis behavior of bitumen was investigated using a thermogravimetric analyzer–mass spectrometer system (TG–MS) and a differential scanning calorimeter (DSC) as well as a pyrolysis-gas chromatograph/mass spectrometer system (Py-GC/MS). TG results showed that there were three stages of weight loss during pyrolysis—less than 110, 110–380, and 380–600 °C. Using distributed activation energy model, the average activation energy of the thermal decomposition of bitumen was calculated at 79 kJ mol−1. The evolved gas from the pyrolysis showed that organic species, such as alkane and alkene fragments had a peak maximum temperature of 130 and 480 °C, respectively. Benzene, toluene, and styrene released at 100 and 420 °C. Most of the inorganic compounds, such as H2, H2S, COS, and SO2, released at about 380 °C while the CO2 had the maximum temperature peaks at 400 and 540 °C, respectively. FTIR spectra were taken of the residues of the different stages, and the results showed that the C–H bond intensity decreased dramatically at 380 °C. Py-GC/MS confirmed the composition of the evolved gas. The DSC revealed the endothermic nature of the bitumen pyrolysis.

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