Hydrolysis Of CS Research Articles

DFT calculation of hydrothermal mechanism on preparation of MoS2.

Basing on the simplest hydrothermal system containing deionized water, hexa-ammonium molybdate, and thiourea, hydrothermal mechanism on preparation of MoS2 was studied by DFT calculation. Hydrothermal process was divided into four steps which covered ionization equilibrium, the hydrolysis of CS(NH2)2, the formation of intermediates, and the formation of MoS2. Ionization equilibrium occurs at normal condition and determines the existence of Mo in the form of molybdic acid. Thiourea hydrolysis is rate-determining step in the process of hydrothermal which contains 10 elementary reactions. The formation of intermediates includes hydrogen transfer, dehydration, and vulcanization three steps which contain 18 elementary reactions, and the energy barrier of vulcanization is the highest. The formation of MoS2 is divided into two steps, the first step is that MoO(OH)(SH)3.H2O reacts with MoO (SH)4.H2O to form layer MoS2, and the second step is a very fast process that can affect the morphology of the products.

Adsorption capacities of poly-γ-glutamic acid and its sodium salt for cesium removal from radioactive wastewaters

Cesium removal from radioactive wastewaters was examined using water-insoluble poly-γ-glutamic acid (γ-PGA) and water-soluble sodium salt form poly-γ-L-glutamic acid (γ-PGANa) as biosorbents. The maximum adsorption capacities at equilibrium of γ-PGA and γ-PGANa for Cs were 345 mg-Cs(g-γ-PGA)−1 at pH 6.0 and 290 mg-Cs(g-γ-PGANa)−1 at pH 9.0, respectively. At lower pH < pKa, the carboxyl groups of γ-PGA primarily remained in the protonated form and adsorption of Cs only slightly occurred. At higher pH > pKa, the adsorption of Cs was significantly facilitated due to ionization of carboxyl groups to carboxylate ion. Adsorption of Cs at pH > 9.0 was inhibited due to the hydrolysis of Cs. The Langmuir model could successfully describe the isotherm data. For γ-PGA and γ-PGANa, the maximum adsorption capacities at equilibrium in the Langmuir model were 446 and 333 mg-Cs(g-adsorbent)−1, respectively. The high adsorption capacities confirmed a potential utilization of γ-PGA and γ-PGANa for Cs removal. The adsorption of Cs by both γ-PGA and γ-PGANa attained the equilibrium within 0.5 min. The very quick equilibration is a benefit from the viewpoint of practical application. The spectra of FT-IR and XPS before and after adsorption confirmed the adsorption of Cs onto γ-PGA and γ-PGANa via electrostatic interaction with carboxylate anions.

Recovery of Nitrifier Populations from Inhibition by Nitrapyrin or CS2

Nitrifying bacteria from four different soils took approximately 40 days to recover from a 1 μg ml−1 addition of nitrapyrin to aqueous suspensions of the soils, even when the bacteria were cultured under favourable conditions. No evidence was obtained for the development of nitrapyrin-resistant nitrifiers, even after prolonged incubation. Repeated large doses (25μg ml−1) of CS2 had little effect on nitrification by Nitrosolobus sp. and only partially inhibited nitrification by Nitrosomonas sp. Recovery of nitrifying activity was rapid, due to evaporation and hydrolysis of CS2 and not to the development of CS2-resistant nitrifiers. CS2 was an effective nitrification inhibitor at low (ca. 4 μg ml−1) concentrations if a constant concentration could be maintained. Recovery of nitrification after inhibition by a low constant level of CS2 took 40–60 days. Die nitrifizierenden Bakterien aus vier verschiedenen Böden benötigten etwa 40 Tage, um sich von der hemmenden Wirkung einer Gabe von Nitrapyrin in wäßrigen Aufschwemmungen der Böden zu erholen, trotzdem die Bakterien unter günstigen Bedingungen gewachsen waren. Auch nach längerer Bebrütung wurde kein Beweis für die Entwicklung von Nitrapyrin-resistenten Nitrifikanten erhalten. Wiederholte große Gaben von CS2 (25 μg ml−1) hatten nur wenig Wirkung auf die von Nitrosolobus sp. verursachte Nitrifikation und hemmten nur teilweise die von Nitrosomonas sp. verursachte. Auf Grund von Verdunstung und Hydrolyse des CS2, jedoch nicht der Entwicklung von CS2-resistenten Nitrifikanten, war die Erholung der Nitrifikationsaktivität ziemlich rasch. Bei niedrigen Konzentrationen (ca. 4 μg ml−1) war CS2 ein wirksamer Hemmstoff der Nitrifikation, wenn nur die Konzentration konstant gehalten werden konnte. Die Erholung der Nitrifikation nach einer Hemmung durch eine niedrige, aber konstante Konzentration von CS2 dauerte 40–60 Tage.