In this study, a novel perspective has been proposed as aUltrasonic Hydrolysisa for hydrogen generation from ammonia borane (NH3BH3) with cobaltaboron (CoaB) catalysts. The CoaB catalysts are ...prepared by the sol-gel reaction of boron oxide (B2O3) with cobalt(II) chloride hexahydrate (CoCI2.6H2O) in the presence of citric acid (C6H8O7). Two types of CoaB catalysts, amorphous and crystalline, are obtained after calcination at 500 and 700ANB degree C respectively. The hydrolysis reactions are carried out in a batch reactor under ultrasonic conditions (frequency of irradiation of 35ANBkHz) at temperatures of 22, 40, 60 and 80ANB degree C using 0.12ANBM NH3BH3 solution with amorphous and crystalline CoaB catalysts. The experimental data is fitted to zero-, first-, and second-order kinetic models and zero model gives good behavior description of the hydrogen generation rate. The maximum hydrogen generation rate is observed with amorphous CoaB catalyst (9157.20 ml.min-1 .g cat-1) and amount optimization, reusability and recyclability test are performed; TOF values forANBcatalytic reactions were calculated. The corresponding activation energy (Ea) is only 47.50 kJ.mol-1 under ultrasonic conditions. In conclusion, the hydrogen generation rate has been increased by 37.79, 21.99, and 21.85% under ultrasonic conditions when the results are compared with 500, 750, and 1000ANBrpm magnetic stirring hydrolysis, respectively.
In this paper, we report an effective approach to the fabrication of hollow titaniaanickel composite spheres, hollow zirconiaanickel composite spheres, and hollow silicaanickel composite spheres. In ...this approach, metal oxideanickel composite shells were coated on polystyrene particles by the sol-gel method and the polystyrene templates were dissolved subsequently, or even synchronously, in the same medium to form hollow spheres. Neither additional dissolution nor a calcination process was needed to remove the polystyrene templates. The as-prepared hollow metal oxideanickel composite spheres were characterized by transmission electron microscopy. The catalytic activities of hollow titaniaanickel composite spheres, hollow zirconiaanickel composite spheres, and hollow silicaanickel composite spheres for hydrolytic dehydrogenation of aqueous NaBH4/NH3BH3 solution were compared. The evolutions of 64, 58, and 18 mL hydrogen were finished in about 49, 69, and 162 min in the presence of the hollow titaniaanickel composite spheres, hollow zirconiaanickel composite spheres, and hollow silicaanickel composite spheres from aqueous NaBH4/NH3BH3 solution, respectively. The molar ratios of the hydrolytically generated hydrogen to the initial NH3BH3 both in the presence of hollow titaniaanickel composite spheres, hollow zirconiaanickel composite spheres, and hollow silicaanickel composite spheres are 2.8, 2.4, and 0.1 (the theoretical value of 3.0), respectively, indicating that the hollow titaniaanickel composite spheres and hollow zirconiaanickel composite spheres show much higher hydrogen evolution rates and the amount of hydrogen evolution via hydrolytic dehydrogenation of ammonia borane than the hollow silicaanickel composite spheres. From the results of ATR-IR spectra, a certain amount of residual PS templates exists in hollow silicaanickel composite spheres, and the amount of the residual PS templates were able to be reduced by increasing the amount of aqueous ammonia solution used for the preparation. The catalytic activity of hollow silicaanickel composite spheres increases when the amount of residual PS templates decreases.
Many fishes are ammonotelic but some species can detoxify ammonia to glutamine or urea. Certain fish species can accumulate high levels of ammonia in the brain or defense against ammonia toxicity by ...enhancing the effectiveness of ammonia excretion through active NH4+transport, manipulation of ambient pH, or reduction in ammonia permeability through the branchial and cutaneous epithelia. Recent reports on ammonia toxicity in mammalian brain reveal the importance of permeation of ammonia through the blood-brain barrier and passages of ammonia and water through transporters in the plasmalemma of brain cells. Additionally, brain ammonia toxicity could be related to the passage of glutamine through the mitochondrial membranes into the mitochondrial matrix. On the other hand, recent reports on ammonia excretion in fish confirm the involvement of Rhesus glycoproteins in the branchial and cutaneous epithelia. Therefore, this review focuses on both the earlier literature and the up-to-date information on the problems and mechanisms concerning the permeation of ammonia, as NH(3), NH4+ or proton-neutral nitrogenous compounds, across mitochondrial membranes, the blood-brain barrier, the plasmalemma of neurons, and the branchial and cutaneous epithelia of fish. It also addresses how certain fishes with high ammonia tolerance defend against ammonia toxicity through the regulation of the permeation of ammonia and related nitrogenous compounds through various types of membranes. It is hoped that this review would revive the interests in investigations on the passage of ammonia through the mitochondrial membranes and the blood-brain barrier of ammonotelic fishes and fishes with high brain ammonia tolerance, respectively.
To develop novel inorganic red pigments without harmful elements, we focused on the band structure of Casub.2(Mg, Co)WOsub.6 and attempted to narrow its bandgap by replacing the Wsup.6+ sites in the ...host structure of Mosup.6+. Casub.2Mgsub.1−xCoxWsub.1−yMoyOsub.6 (0.10 ≤ x ≤ 0.30; 0.45 ≤ y ≤ 0.60) samples were synthesized by a sol-gel method using citric acids, and the crystal structure, optical properties, and color of the samples were characterized. The Casub.2Mgsub.1−xCoxWsub.1−yMoyOsub.6 solid solution was successfully formed, which absorbed visible light at wavelengths below 600 nm. In addition, the absorption wavelength shifted to longer wavelengths with increasing Mosup.6+ content. This is because a new conduction band composed of a Cosub.3d-Wsub.5d-Mosub.4d hybrid orbital was formed by Mosup.6+ doping to reduce the bandgap energy. Thus, the color of the samples gradually changed from pale orange to dark red, with a hue angle (h°) of less than 35°. Based on the above results, the optical absorption wavelength of the Casub.2Mgsub.1−xCoxWsub.1−yMoyOsub.6 system can be controlled to change the color by adjusting the bandgap energy.
Nitrification is a key process of the nitrogen (N) cycle in soil with major environmental implications. The recent discovery of ammonia-oxidizing archaea (AOA) questions the traditional assumption of ...the dominant role of ammonia-oxidizing bacteria (AOB) in nitrification. We investigated AOB and AOA growth and nitrification rate in two different layers of three grassland soils treated with animal urine substrate and a nitrification inhibitor dicyandiamide (DCD). We show that AOB were more abundant in the topsoils than in the subsoils, whereas AOA were more abundant in one of the subsoils. AOB grew substantially when supplied with a high dose of urine substrate, whereas AOA only grew in the Controls without the urine-N substrate. AOB growth and the amoA gene transcription activity were significantly inhibited by DCD. Nitrification rates were much higher in the topsoils than in the subsoils and were significantly related to AOB abundance, but not to AOA abundance. These results suggest that AOB and AOA prefer different soil N conditions to grow: AOB under high ammonia (NH₃) substrate and AOA under low NH₃ substrate conditions.
Nitrification is a central component of the global nitrogen cycle. Ammonia oxidation, the first step of nitrification, is performed in terrestrial ecosystems by both ammonia‐oxidizing bacteria (AOB) ...and ammonia‐oxidizing archaea (AOA). Published studies indicate that soil pH may be a critical factor controlling the relative abundances of AOA and AOB communities. In order to determine the relative contributions of AOA and AOB to ammonia oxidation in two agricultural acidic Scottish soils (pH 4.5 and 6), the influence of acetylene (a nitrification inhibitor) was investigated during incubation of soil microcosms at 20 °C for 1 month. High rates of nitrification were observed in both soils in the absence of acetylene. Quantification of respective amoA genes (a key functional gene for ammonia oxidizers) demonstrated significant growth of AOA, but not AOB. A significant positive relationship was found between nitrification rate and AOA, but not AOB growth. AOA growth was inhibited in the acetylene‐containing microcosms. Moreover, AOA transcriptional activity decreased significantly in the acetylene‐containing microcosms compared with the control, whereas no difference was observed for the AOB transcriptional activity. Consequently, growth and activity of only archaeal but not bacterial ammonia oxidizer communities strongly suggest that AOA, but not AOB, control nitrification in these two acidic soils.
A novel Mn/TiOsub.2 catalyst, prepared through modification with the rare-earth metal Dy, has been employed for low-temperature selective catalytic reduction (SCR) denitrification. Anatase TiOsub.2, ...with its large specific surface area, serves as the carrier. The active component MnOsub.x on the TiOsub.2 carrier is modified using Dy. Dysub.xMn/TiOsub.2, prepared via the impregnation method, exhibited remarkable catalytic performance in the SCR of NO with NHsub.3 as the reducing agent at low temperatures. Experiments and characterization revealed that the introduction of a suitable amount of the rare-earth metal Dy can effectively enhance the catalyst’s specific surface area and the gas–solid contact area in catalytic reactions. It also significantly increases the concentration of Mnsup.4+, chemisorbed oxygen, and weak acid sites on the catalyst surface. This leads to a notable improvement in the reduction performance of the DyMn/TiOsub.2 catalyst, ultimately contributing to the improvement of the NHsub.3-SCR denitrification performance at low temperatures. At 100 °C and a space velocity of 24,000 hsup.−1, the Dysub.0.1Mn/TiOsub.2 catalyst can achieve a 98% conversion rate of NOsub.x. Furthermore, its active temperature point decreases by 60 °C after the modification, highlighting exceptional catalytic efficacy at low temperatures. By doubling the space velocity, the NOsub.x conversion rate of the catalyst can still reach 96% at 130 °C, indicating significant operational flexibility. The selectivity of Nsub.2 remained stable at over 95% before reaching 240 °C.
S3336 An Unusual Cause of Encephalopathy Tripathi, Shalini; Khuttan, Akhilesh
The American journal of gastroenterology,
10/2022, Letnik:
117, Številka:
10S
Journal Article
PDF
