Mesoporous molecular sieve MCM-41 and zeolite-P were synthesized from natural clinoptilolite zeolite and cetyltrimethylammonium bromide under hydrothermal conditions in alkaline media. The formation path of MCM-41 and zeolite-P from natural clinoptilolite was investigated using XRD, TG, SEM, and FT-IR for the samples obtained in the course of the synthesis. XRD and TG results exhibited that in the first stage where the mixture of clinoptilolite and cetyltrimethylammonium bromide was treated in alkaline media at ambient temperature, crystal structure of clinoptilolite did not change significantly. In the second stage where the mixture was subsequently treated under hydrothermal conditions, dissolution of clinoptilolite and formation of zeolite-P were observed, while mesophase with 2d hexagonal structure of MCM-41 was not detected. In the third stage, mesostructure with 2d hexagonal symmetry was gradually formed by the adjustment of pH of the reaction mixture between 10.5 and 8.5. Structural integrity of 2d hexagonal assembly of as-synthesized MCM-41 was improved by controlling pH of the reaction mixture to 8.5 followed by the hydrothermal treatment. In contrast, the structure of zeolite-P was not affected by these treatments. SEM images of the samples showed that small particles of MCM-41 were mainly formed on the surface of the zeolite-P particles and agglomerated to larger grains. Judging from the results of XRD patterns and FT-IR spectra of the samples, it is indicated that smaller crystallites or building units of clinoptilolite that were X-ray amorphous and IR detectable were probably incorporated in the pore walls of MCM-41.

抄録全体を表示

Paper sludge ash was converted into a zeolitic product with high cation exchange capacity (CEC) through acid leaching. The raw ash was treated with 1 M HCl, 1 M HNO₃ and 1 M CH₃COOH solutions. Ca and Mg were more easily extracted from the ash than Si and Al, and the Ca extractions using HCl and HNO₃ were higher than that from CH₃COOH. Element extractions and leachant pH in the HCl and HNO₃ solutions were similar and steady state was achieved after 2 hours of leaching. A zeolitic product was synthesized from the 2-hour 1 M HCl ash leach by reaction of the residue with 2.5 M NaOH solution (80°C, 24 hours). Zeolite-A was synthesized from leached ash, and the CEC of the zeolite produced from leached ash (130 cmol/kg) was higher that that from raw ash (40 cmol/kg), and similar to that obtained when leaching ash for 24 hours.

抄録全体を表示

TiO₂-SBA-15 mesoporous materials in which titanium oxide species were dispersed inside the pore channels of SBA-15 were prepared by a novel post-synthesis method. In this method, cetyltrimethylammonium bromide surfactant molecules were incorporated inside the channels of the mesopores of SBA-15 followed by the addition of titanium tetraethoxide. Effect of hydrolysis conditions of titanium tetraethoxide on the formation and properties of Ti oxides in TiO₂-SBA-15 materials was investigated. Physico-chemical properties of TiO₂-SBA-15 materials were characterized by XRD, N₂ adsorption, SEM and UV-vis. Size and morphology of Ti oxide species in TiO₂-SBA-15 materials were dependent on the hydrolysis conditions of titanium tetraethoxide, i.e., H₂O/Ti molar ratio. Dispersed titanium oxide species were mainly formed on the internal surface of SBA-15, i.e., on the surface of mesopore walls of the TiO₂-SBA-15 samples when synthesized at low H₂O/Ti ratios of 2 and 4, whereas large TiO₂ anatase particles were predominantly formed on the external surface of SBA-15 when the samples were prepared at high H₂O/Ti molar ratios. The photocatalytic activity of the TiO₂-SBA-15 samples was investigated for the degradation of methylene blue, MB, and compared with that of pure TiO₂, P25. The TiO₂-SBA-15 samples, in which titanium oxide species were dispersed on the internal surface of SBA-15, showed higher and more stable photocatalytic activity in the degradation and/or decolorization of MB than P25 and TiO₂-SBA-15 which has TiO₂ particles on the outer surface of SBA-15.

抄録全体を表示

A combustion flame method enables the synthesis of diamond using acetylene-oxygen gas (C₂H₂/O₂) combustion flame in ambient air. Recently, tungsten carbide (WC) is used as cutting tools in the machining industry. In this study, diamond films were synthesized by combustion flame on WC surfaces. However, it was difficult to synthesize the diamond films on the WC substrate surfaces. Therefore, in order to synthesize the diamond film, a two-step synthesis method was proposed. In this method, the film surface temperature and the distance of the flame inner cone from the surface for each step are changed during the synthesis. The first step was setting the film temperature to 1273 K, the second step was setting to 1223 K. The distance of the flame inner cone from the surface was changed for each step (Case 1 ;the first step: d=7.0 mm, the second step: d=7.0 mm, Case 2 ; the first step : d=7.0 mm, the second step : d=7.5 mm, Case 3 ; the first step : d=7.5 mm, the second step : d=7.0 mm). In the Case 1 and 2, the delamination-free film was synthesized on the WC surfaces, and diamonds were synthesized. However, in the Case 3, the film vvvvdelamination occurred, and good diamond films were not synthesized.

抄録全体を表示

Activated carbons from raw materials of lignocellulosic residues such as rice straws, cedar bark, and waste cardboard sludge were prepared by carbonizing the raw materials under N₂ atmosphere at 673-1273 K for 1-12 h, followed by activation under CO₂ atmosphere at 973-1173 K for 0.5-6 h. Zr-loaded activated carbons were also prepared from them by a conventional impregnation method using zirconium oxynitrate solution. The obtained carbon samples were characterized by N₂ adsorption and XRD. Development of microporosity in the activated carbons was dependent upon the precursors and the activation conditions employed. The α_s-plot and pore size distribution analyses exhibited that loading of Zr species on the activated carbons in this study did not give significant influences on the microporosity of the activated carbons. A quantitative adsorption of phosphate on the Zr-loaded activated carbons was achieved below pH 9. It was found that the adsorption of phosphate on both activated carbons and Zr-loaded samples was fitted satisfactorily to Langmuir adsorption isotherms. Phosphate adsorption capacities of Zr-loaded activated carbons from rice straws and waste cardboard sludge were evaluated to be 11.1 and 5.97 mg-P g^-1, respectively, which were larger than those of relevant activated carbons used as supports. Application of Dubinin-Radushkevich analysis to the phosphate adsorption isotherms indicates that the adsorption mainly proceeds through an ion exchange mechanism.

抄録全体を表示