Thermally reduced ruthenium nanoparticles as a highly active heterogeneous catalyst for hydrogenation of monoaromatics.

We report here a thermal reduction method for preparing Ru catalysts supported on a carbon substrate. Mesoporous SBA-15 silica, surface-carbon-coated SBA-15, templated mesoporous carbon, activated carbon, and carbon black with different pore structures and compositions were employed as catalyst supports to explore the versatility of the thermal reduction method. Nitrogen adsorption, X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, scanning transmission electron microscopy, thermogravimetric analysis, and X-ray absorption near-edge structure techniques were used to characterize the samples. It was observed that carbon species that could thermally reduce Ru species at high temperatures played a vital role in the reduction process. Ru nanoparticles supported on various carbon-based substrates exhibited good dispersion with an appropriate particle size, high crystallinity, strong resistance against oxidative atmosphere, less leaching, lack of aggregation, and avoidance of pore blocking. As such, these catalysts display a remarkably high catalytic activity and stability in the hydrogenation of benzene and toluene (up to 3-24-fold compared with Ru catalysts prepared by traditional methods). It is believed that the excellent catalytic performance of the thermally reduced Ru nanoparticles is related to the intimate interfacial contact between the Ru nanoparticles and the carbon support.

Copolymer-controlled homogeneous precipitation for the synthesis of porous microfibers of alumina.

Mesoporous aluminas with a uniform fibrous morphology were synthesized using a copolymer-controlled homogeneous precipitation method under hydrothermal conditions. Scanning electron microscopy, X-ray diffraction, solid-state magic-angle spinning nuclear magnetic resonance, transmission electron microscopy, thermogravimetric analysis, nitrogen adsorption, Fourier transform infrared spectrometry, and elemental analysis techniques were used to characterize the samples. The effect of various synthesis conditions on the morphology and mesoporous structure of the alumina fibers was investigated. Such porous alumina microfibers may find applications in nanotechnology and catalysis. They can also be used as advanced high-temperature composite materials and templates for fabrication of fibrous materials of various compositions, such as carbon, transition-metal oxides, and polymers.

Sorption and biodegradation of phthalic acid esters in freshwater sediments.

Pathalic acid esters (PAEs) have been used as plasticizers in many products so that they could enter the aquatic environment. Three freshwater sediments in Taiwan were selected to explore the sorption and biodegradation processes of PAEs. Results indicated that di-n-butyl phthalate (DBP) and di-2-ethylhexyl phthalate (DEHP) are the only detectable PAEs which ranged in 24.9-68.3 mg/kg and 39.1-71.9 mg/kg in this study. The adsorption capacities of DBP and DEHP were identified by Kf values of the nonlinear Freundlich model associated with R2 values more than 0.90. This is expected that partition is the main mechanism controlling the transfer of PAEs between water and sediment phases. After 30 days contact, much of DBP and DEHP were removed immediately within 1 day in the desorption process. Because microorganism is as the major routes of breakdown of PAEs in the environment, much lower degraded amounts of DBP and DEHP occurred in the sterilized sediment than those in the unsterilized sediments.

Performance of subsurface flow constructed wetland taking pretreated swine effluent under heavy loads.

Subsurface flow constructed wetlands (SSFCW) subjected to changing of loading rates are poorly understood, especially when used to treat swine waste under heavy loads. This study employed a SSFCW system to take pretreated swine effluent at three hydraulic retention times (HRT): 8.5-day HRT (Phase I), 4.3-day HRT (Phase II), and 14.7-day HRT (Phase III). Results showed that the system responded well to the changing hydraulic loads in removing suspended solids (SS) and carbonaceous oxygen demands. The averaged reduction efficiencies for four major constituents in the three phases were: SS 96-99%, chemical oxygen demand (COD) 77-84%, total phosphorus 47-59%, and total nitrogen (TN) 10-24%. While physical mechanisms were dominant in removing pollutants, the contributions of microbial mechanisms increased with the duration of wetland use, achieving 48% of COD removed and 16% of TN removed in the last phase. Water hyacinth made only a minimal contribution to the removal of nutrients. This study suggested that the effluent from SSFCW was appropriate for further treatment in land applications for nutrient assimilation.