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A novel nano-adsorbent prepared by hydrothermal carbonization of chitosan was used for removing molybdenum (Mo(VI)) from groundwater. Optimal adsorption parameters were determined via varying pH, time, concentrations, and temperatures. The results indicated that the removal rate of Mo(VI) by chitosan carbonization nanoparticles (CCN) was depended on pH values and the maximum adsorption efficiency could be achieved when the pH is in the range of 1.5-3.3. Kinetic studies showed that Mo(VI) could be removed rapidly, and the experimental results fitted pseudo-second- order kinetic model well. Mo(VI) adsorbed by CCN was described well by Langmuir model and the theoretical maximum adsorption capacity reached 192.308 mg g-1 at 303.15 K. Thermodynamic parameters indicated that the adsorption process was endothermic, entropy increasing, and spontaneous. Electrostatic interaction and hydrogen bonding were the major adsorption mechanisms. Regeneration and real groundwater treatment experiments revealed that Mo(VI) could be removed efficiently by CCN, and CCN could be recycled for a long term. Altogether, CCN might be a green, efficient, and recyclable adsorbent for Mo(VI) removal from groundwater. [ABSTRACT FROM AUTHOR]

Molybdenum (Mo) is an important pollutant in surface water. Removal of Mo from aqueous solutions by adsorption using low-cost and environmental friendly adsorbents has gained wide acceptance. Drinking water treatment residue (DWTR) is an inevitable by-product during potable water production that has the high capability of adsorption of heavy metals. However, the characteristics and mechanisms of Mo adsorption by DWTR still remain unclear. In this study, we showed that Mo(VI) adsorption by DWTR followed the pseudo-second-order rate. The adsorption isotherms for Mo(VI) were best described by the Langmuir model. Thermodynamic parameters indicated that the adsorption process was endothermal, entropy increasing, and spontaneous. Electrostatic interaction and surface complexation were found to be major adsorption mechanisms. The adsorption rate of Mo(VI) by DWTR was dependent on pH values and lineally increased as pH decreased from 10 to 4. The estimated maximum adsorption capacity was 31.06 mg/g at 318 K at pH 2.0. Desorption experiments were also performed to evaluate the potential of DWTR regeneration. These results suggested that DWTR was a green, efficient, and recyclable adsorbent for Mo(VI) and could be used for removal and recovery of Mo from polluted environments. [ABSTRACT FROM AUTHOR]

Oxidative radical addition/cyclization cascade of o-cyanoarylacrylamides with a-keto acids as well as aldehydes is reported. This transformation exhibits a wide substrate scope and significant functional group tolerance and provides a convenient and highly efficient access to carbonyl-containing quinoline-2,4(1H,3H)-diones. A possible mechanism for the transformation is proposed. [ABSTRACT FROM AUTHOR]

The objective of this study is to establish a centrifugal partition chromatography (CPC) method for determination of the urea ingredient in urea cream. The mechanism of this method is that urea is determined by UV detector at 430 nm after being extracted from the cream and derivatized on line via Ehrlich reaction in rotor of CPC, where the reaction products dissolve in the mobile phase and the cream matrix retains in the stationary phase. The mixed solvent consisting of n-hexane, methanol, hydrochloric acid and p-dimethylaminobenzaldehyde with a ratio of 1000 mL:1000 mL:18 mL:2.0 g is used for solvent system of CPC. The CPC method proposed offers good precision and convenience without complex sample pretreatment processes. [ABSTRACT FROM AUTHOR]

To study the chemical constituents of aerial part of Gentiana scabra Bunge, the plant material was extracted with ethanol, and the constituents were separated and purified from the ethanol extraction by silica gel column chromatography. Their structures were identified as 6-demethoxy-7-methylcapillarisin (VI) and five other compounds, β-Amyrin (I ), β-Sitosterol (II), β-Amyrin acetate (III), Uvaol (IV) and Oleanolic acid (V) on the basis of physicochemical properties and spectral methods. Among them, Compound VI was isolated from Gentianaceae family for the first time. Its characterization of 1D and 2D NMR spectra and possible fragmentation pathway in El-MS were discussed. The crystal structure of Compound VI was determined to be orthorhombic and Pbca space group by X-ray crystallographic analysis. Crystal data are as follows: a = 1. 291 83(19) nm, b = 0.72119 (15) nm, c = 2.923 7 (5) nm, a = 90°, β = 90°, γ = 900, V = 2.723 9 (8) nm3, Z = 8, De = 1. 464 g/m3, μ = 0. 114 mm-1, F(000) = 1 248. The dihedral angle between B ring and A/C ring is 99. 6°. There are π-π stacking interactions between molecules. [ABSTRACT FROM AUTHOR]