Green Synthesis of Nanostructure CeO2 Using Tea Extract: Characterization and Adsorption of Dye from Aqueous Phase.

Nanostructure CeO2 powders were synthesized using tea waste extract as gel precursor. The as-prepared samples were characterized by thermogravimetric analyzer (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. Based on the TGA/DTG analysis, the intermediates of cerium chloride hydrates (CeCl3.4H2O and CeCl3.H2O) and cerium anhydrous (CeCl3) were produced, and the formation temperature of CeO2 was estimated to be 773 K. The cubic fluorite structure of CeO2 was detected to be the predominant species and was completely formed at the calcination temperature of 773K-1073 K with a crystal size between 8.8 and 11.4 nm based on the XRD measurement. Moreover, the main chemical state of ceria on the surface of the synthesized samples was confirmed to be tetravalent ceria by XPS. All samples show a strong Raman signal at a well-defined chemical shift of 463 cm-1 and a significant symmetry feature was observed, suggesting that the tetravalent ceria is the dominant species throughout the bulk sample. All the synthesized CeO2 calcined at different temperatures showed higher adsorption efficiency for Congo red (CR) compared with commercial CeO2. The adsorption efficiency maintained a steady state of more than 95% when the concentration of CR and adsorption temperature were varied in this study. The kinetic analysis showed that the second-order model was the appropriate model to interpret the adsorption behavior of synthesized CeO2. The calculated adsorption capacity derived from the second-order model is in good agreement with the experimental data. The isotherm analysis revealed that the Freundlich and D-R models fit well for the synthesized CeO2 and represent physisorption with a multilayer mechanism. The thermodynamic parameters, including the changes in Gibb's free energy, enthalpy, and entropy, suggested that the adsorption of CR on the synthesized CeO2 sample was a spontaneous and endothermic process.

Protein Expression Analysis in Reversible Photobleached Cells of Scenedesmus vacuolatus after High Temperature Stress.

We have analyzed protein expression in the bleached small vegetative cells of synchronous Scenedesmus vacuolatus to investigate how unicellular algae lived through stress. These cells were subjected to heat treatment (46.5 °C for 1h in dark condition) and then cultured under continuous illumination for 24 h. Flow cytometry analysis of the chlorophyll autofluorescence intensity of S. vacuolatus cells indicated that heat-treated cells were completely bleached within 24 h of light cultivation. Transmission electron microscopy (TEM) images showed that bleached cells maintained thylakoid membrane structure, but with lower contrast. The bleached cells regained green color after 72 h, along with a recovery in contrast, which indicated a return of photosynthetic ability. Two-dimensional gel electrophoresis (2DE) showed that the protein expression patterns were very difference between control and bleached cells. ATP synthase subunits and glutamine synthetase were down-regulated among the many differences, while some of phototransduction, stress response proteins were up-regulated in bleached cells, elucidating bleached cells can undergo changes in their biochemical activity, and activate some stress response proteins to survive the heat stress and then revive. In addition, small heat shock proteins (HSPs), but not HSP40 and HSP70 family proteins, protected the bleaching cells.

Measurement of Total Free Iron in Soils by H2S Chemisorption and Comparison with the Citrate Bicarbonate Dithionite Method.

Free iron is one of the major analytical items for soil basic properties. It is also an important indicator for understanding the genesis of soil, soil classification, and soil distribution behavior. In this study, an alternative analytical method (chemisorption) based on thermodynamic knowledge was proposed for measurement of total free iron oxides in soils. Several representative soil samples belonging to alfisols, ultisols, inceptisols, and entisols were collected from Taiwan and tested by the chemisorption, and the estimated total free iron oxides were compared with those measured from the traditional citrate bicarbonate dithionite (CBD) method. Experimental results showed that the optimal operating temperature was found to be at 773 K and the carbon monoxide (CO) is the best gaseous reagent to promote the formation of FeS. The estimated total free iron oxides for soil samples determined from the chemisorption in the presence of CO were very close to those from the CBD technique. The result of regression indicates that the estimated total free iron is strongly correlated with the CBD-Fe content (R2 = 0.999) in the presence of CO.

Nature and properties of lateritic soils derived from different parent materials in Taiwan.

The objective of this study was to investigate the physical, chemical, and mineralogical composition of lateritic soils in order to use these soils as potential commercial products for industrial application in the future. Five lateritic soils derived from various parent materials in Taiwan, including andesite, diluvium, shale stone, basalt, and Pleistocene deposit, were collected from the Bt1 level of soil samples. Based on the analyses, the Tungwei soil is an alfisol, whereas other lateritic soils are ultisol. Higher pH value of Tungwei is attributed to the large amounts of Ca(2+) and Mg(2+). Loupi and Pingchen soils would be the older lateritic soils because of the lower active iron ratio. For the iron minerals, the magnetic iron oxides such as major amounts of magnetite and maghemite were found for Tamshui and Tungwei lateritic soils, respectively. Lepidocrocite was only found in Soka soil and intermediate amounts of goethite were detected for Loupi and Pingchen soils. After Mg-saturated and K-saturated processes, major amounts of mixed layer were observed in Loupi and Soka soils, whereas the montmorillonite was only detected in Tungwei soil. The investigation results revealed that the parent materials would play an important role during soil weathering process and physical, chemical, and mineralogy compositions strongly affect the formation of lateritic soils.

A study of Zn-Mn based sorbent for the high-temperature removal of H2S from coal-derived gas.

Zn-Mn based sorbents supported on SiO2, gamma-Al(2)O(3) and ZrO2, prepared by the incipient wetness impregnation method with calcination at 973 K were investigated for the removal of H(2)S from coal derived gas at the temperature ranges of 773-973 K. Results reveal that the SiO2 and ZrO2 supports exhibit the better performance because better removal efficiency. The addition of manganese effectually improves the vaporization of zinc. In addition, some operating parameters were also considered in order to understand as well as screen the suitable conditions for the development of Zn-Mn based sorbents on the removal of H(2)S. Over 98% sorbent utilization was established for the use of SiO2 at 873 K. On the other hand, within the 5-15 wt% of Zn-Mn oxides, no significant change in the sorbent utilization was observed. Up to 30 wt% the sorbent utilization decreased slightly compared to lower contents, which may be attributed to the deficient dispersion. With increasing the H2 concentration, the sorbent utilization decreases and an adverse result is observed in the case of increasing CO concentration. The relationship between CO and H2 could be explained via the water-gas shift reaction. Moreover, the apparent activation energy and frequency factor as well as the predicted results were studied with a deactivation model. The results of regression fitting reveal the accurate prediction breakthrough behaviors for the removal of H(2)S.

Spectroscopic study on the zinc-contaminated soils for the determination of zinc speciation.

The purpose of this paper reported the zinc species in the highly contaminated soils from metallurgical area around Erh-Jen River in the southern of Taiwan. FTIR and XPS were used to investigate the zinc species in the contaminated soils. Through a FTIR analysis, appreciable of zinc bound by organic matter was found and their bonding structure consisted of antisymmetric and symmetric stretchings, Zn-HSsym and Zn-HSasym. With XPS analysis, the Angstrom scale depth scan was surveyed for investigation the zinc speciation. No signal of zinc was detected in the depth of 900A for the larger particle contaminated soils whereas the detectable signal of zinc was determined in the XPS experiment. With further regression and fitting results, the major zinc species presented in the surface of larger and fine particle contaminated soils consisted of reductive and oxidative zinc species. In the deeper depth of contaminated soils, an inverse spinel zinc ferrite was found in the case of larger particle soil. No inverse spinel zinc ferrite was detected in the case of fine particle soil and could be attributed to the relatively small particle size.

Study on photocatalytic degradation of gaseous dichloromethane using pure and iron ion-doped TiO2 prepared by the sol-gel method.

The synthesis of TiO2 and Fe-TiO2 by sol-gel method is demonstrated and characterized. The characterization of TiO2 and Fe-TiO2 is performed with instruments, including TGA/DTA, FTIR, UV-Vis, N2 adsorption and SEM. Dichloromethane is used for the photocatalytic activity test. From the results of dichloromethane photocatalytic degradation, the calcined temperature of TiO2 and the presence of water vapor influence the photocatalytic activity. The optimum doping amount of iron ions is 0.005 mol%, and this can enhance the photocatalytic activity, while too great an amount will make the iron ions become recombination centers for the electron-hole pairs and reduce the photocatalytic activity. UV-Vis diffuse reflectance spectra of Fe-TiO2 show an increase in absorbency in the visible light region with the increase in iron ions doping concentration The intermediate of dichloromethane photodegradation includes CHCl3, CCl4, CH2Cl2 and COCl2. The presence of iron ions may reduce the adsorption of Cl element on the surface of the photocatalyst.

X-ray absorption spectroscopy study of H2S sorption on iron-rich soil: characterization of iron-sulfur species.

Iron-rich soil after sorption of H(2)S was characterized using X-ray absorption near-edge structural (XANES) and extended X-ray absorption fine structure spectroscopy (EXAFS) for determination the possible products in the present work. EXAFS revealed that the main Fe-S species in the sulfided sample were FeS (troilite) and Fe(1-x)S (pyrrohotite). Iron in the sulfided sample was found to possess a Fe-S bond distance of 2.36 A and a Fe-O bond distance of 1.72 A in the Fe-K-edge spectra whereas the Fe-S bond distance of 2.25 A was determined in the sulfur K-edge spectra. In the second shells, the bond distance of Fe-O-Si or Fe-O-Al with 3.28 A was also observed. No FeS2 (pyrite) was included in the sulfided sample. The formation of Fe(1-x)S was probably attributed to the presence of Fe(3)O(4), a type of spinel structure with a lattice deficiency.

Feasibility study on high-temperature sorption of hydrogen sulfide by natural soils.

In this study, seven natural soils were tested for the sorption of hydrogen sulfide from coal gasification gas at high temperature. Results indicate that the LP natural soil has the best performance and the highest sulfur sorption capacity. After extracting free iron oxides, most natural soils have no sorption efficiency. The free iron oxides, therefore, proved to be the major components that react with hydrogen sulfide to form iron sulfides. The sulfur sorption capacity, either determined by EA or breakthrough time, is very close to the theoretical value based on the stoichiometric calculation with the content of free iron oxides. Moreover, the presence of CO is a positive effect while H2 is a negative effect. This can be explained via the water-shift reaction. On the basis of the results of temperature-programmed sulfidation (TPS), the starting temperature for the sorption of hydrogen sulfide is between 623-673 K. From the analyses of temperature-programmed oxidation (TPO) and XPS, the iron polysulfides are the major products and approximately 90% regeneration efficiency can be theoretically achieved while the temperature is controlled higher than 813 K. In the regeneration tests, the results show that the LP natural soil can be regenerated and thus reused after the oxidation process. No significant degeneration occurs on the LP natural soil after five sorption/regeneration cycles. The sulfur sorption capacity of the tenth regenerated soil can be achieved at least 80% compared to the fresh one. The experimental analyzed SO2 concentration from the regeneration process is almost identical to the theoretical calculated equilibrium concentration of the process. Maghemite is the main product after the regeneration process.

Red soil as a regenerable sorbent for high temperature removal of hydrogen sulfide from coal gas.

In this study, hydrogen sulfide (H(2)S) was removed from coal gas by red soil under high temperature in a fixed-bed reactor. Red soil powders were collected from the northern, center and southern of Taiwan. They were characterized by XRPD, porosity analysis and DCB chemical analysis. Results show that the greater sulfur content of LP red soils is attributed to the higher free iron oxides and suitable sulfidation temperature is around 773K. High temperature has a negative effect for use red soil as a desulfurization sorbent due to thermodynamic limitation in a reduction atmosphere. During 10 cycles of regeneration, after the first cycle the red soil remained stable with a breakthrough time between 31 and 36 min. Hydrogen adversely affects sulfidation reaction, whereas CO exhibits a positive effect due to a water-shift reaction. COS was formed during the sulfidation stage and this was attributed to the reaction of H(2)S and CO. Results of XRPD indicated that, hematite is the dominant active species in fresh red soil and iron sulfide (FeS) is a product of the reaction between hematite and hydrogen sulfide in red soils. The spinel phase FeAl(2)O(4) was found during regeneration, moreover, the amount of free iron oxides decreased after regeneration indicating the some of the free iron oxide formed a spinel phase, further reducting the overall desulfurization efficiency.

The kinetic of the catalytic decomposition of methyl isobutyl ketone over a Pt/gamma-Al2O3 catalyst.

Environmental catalysis also can refer to catalytic technologies for reducing emission of environmentally unacceptable compounds. Catalytic decomposition also is one of the cost-effective technologies to solve the troublesome volatile organic compounds. This study treated methyl isobutyl ketone (MIBK) by a commercial catalyst, Pt/gamma-Al(2)O(3), in an isothermal fixed bed differential reactor. The effects of O(2) and MIBK content in carrier gas on the catalysis's reaction rate are also observed. Three kinetic models, i.e. the Mars and van Krevelen model, Langmuir-Hinshelwood model and power-rate law were applied to best fit the experimental results. The results indicate that the kinetic behavior of MIBK oxidation with catalysis can be accounted for by using the rate expression of the Mars and van Krevelen model and Langmuir-Hinshelwood model. Kinetic parameters are also determined on the basis of the differential reactor data. The experimental results are compared with those of the model predicted.

The operating performance and products distribution of the catalytic oxidation of methyl-isobutyl-ketone over a Pt/gamma-Al2O3 catalyst.

Catalytic oxidation is one of the cost-effective technologies to solve the troublesome volatile organic compounds. This study treated methyl-isobutyl-ketone (MIBK) by a commercial catalyst, Pt/gamma-Al(2)O(3), in a fixed-bed reactor. The effects of operating factors, such as operating temperature, MIBK concentration, space velocity, and O(2) concentration, on the performance of the catalyst were investigated. The products and reactants distributions from the oxidation of MIBK over Pt/gamma-Al(2)O(3) were observed. The results show that the products containing carbon atoms are CO, CO(2), and C(3)H(6)O. Two catalyst life-tests were also carried out to characterize the deactivation effect of MIBK. The result shows that the deactivation effect may be due to the coke on the catalyst surface at 423 K. From the statistical analysis, the operating temperature is the most effective factor on the conversion of MIBK. The catalysts were also characterized by surface area analysis and elemental analysis before and after the test. The results show that the catalytic deactivation may be due to carbon coating. At low temperature (423 K), the phenomenon of carbon coating was more obvious than that at high temperature (573 K). The product distributions from the oxidation of MIBK over Pt/gamma-Al(2)O(3) were analyzed by GC. The results indicate that the C(3)H(6)O is formed from the beginning, presenting a peak at 423 K, 6.54 ppm. The CO concentration also peaked at the same temperature, 6.84 ppm.

The sorption of hydrogen sulfide from hot syngas by metal oxides over supports.

Six 5 wt.% metal sorbents including Mn, Fe, Cu, Co, Ce and Zn supported on gamma-Al2O3, prepared by the incipient wetness impregnation method with calcination at 700 degrees C for 2 h, have been investigated for sorption of hydrogen sulfide in the temperature range of 500-700 degrees C. The sorption experiments were conducted in a fixed-bed reactor in terms of breakthrough curves and characterized by X-ray powder diffraction. The results reveal that the copper and manganese sorbents exhibit the best performance because they provide nearly 100% utilization, but the copper sorbent has a lower sulfur sorption capacity compared with the manganese sorbent. The zinc and cerium sorbents are not good candidates attributed to the vaporization of zinc and unexpected product for cerium. Effects of support materials on 5 wt.% manganese were also investigated by using gamma-Al2O3, SiO2 and TiO2 in this study. Five weight percent Mn/gamma-Al2O3 shows the best performance among support candidates. On the basis of XRPD and BET surface area analysis, TiO2 appears a huge loss in BET surface area associated with a significant formation of rutile form.