Authors:W. Dong, X. Wang, J. Du, X. Bian, F. Ma, and Z. Tao
The batch method and the column method were simultaneously employed to study the sorption and desorption of Eu(III) on red
earth as a function of pH (4.6–6), the presence of a well-characterized fulvic acid (FA) and the iron oxides content of red
earth. The results from both methods were consistent qualitatively. The Eu(III) sorption showed significant dependences on
pH and FA, the sorption was increased with increasing pH and by addition of FA to the solutions, while the iron oxides content
of the red earth had a negative contribution to the sorption of Eu(III). Additionally, the sorption-desorption hysteresis
of Eu(III) on red earth occurred at a pH range of 4.6–6. Therefore, the humic substance and high pH have a great tendency
to immobilize Eu(III) on red earth.
Authors:J. Du, W. Li, H. Zhang, X. Wang, Z. You, C. Zhou, W. Dong, and Z. Tao
The stability constants for tracer concentrations of Co(II) complexes with both the red earth humic and fulvic acids were
determined at pH 5.9 and ionic strength 0.010 mol/l by using theArdakani-Stevenson cation exchange equilibrium method and the radiotracer60Co. It was found that the 1:1 complexes of Co(II) with the red earth humic and fulvic acids were formed and that the average
values of logβ (stability constant) of humic and fulvic acid complexes were 5.76±0.19 and 4.42±0.03, respectively.
Authors:Mingming Wang, Jun Qiu, Xinquan Tao, Cuiping Wu, Weibing Cui, Qiong Liu, and Songsheng Lu
Multiwalled carbon nanotubes (MWCNTs) have attracted multidisciplinary study because of their unique physicochemical properties.
Herein, the sorption of U(VI) from aqueous solution to oxidized MWCNTs was investigated as a function of contact time, pH
and ionic strength. The results indicate that U(VI) sorption on oxidized MWCNTs is strongly dependent on pH and ionic strength.
The sorption of U(VI) is mainly dominated by surface complexation and cation exchange. The sorption of U(VI) on oxidized MWCNTs
is quickly to achieve the sorption equilibrium. The sorption capacity calculated from sorption isotherms suggests that oxidized
MWCNTs are suitable material in the preconcentration and solidification of U(VI) from large volumes of aqueous solutions.
Authors:De-Xin Ding, Xi-Tao Liu, Nan Hu, Guang-Yue Li, and Yong-Dong Wang
Experiments on the removal and recovery of U(VI) from aqueous solution by tea waste were conducted. The adsorbent was characterized
by scanning electron microscope and energy dispersive spectrometer before and after the adsorption treatment. The removal
of U(VI) amounts to 86.80 % at optimum pH 6. The adsorption process reaches its equilibrium in 12 h at 308 K, and the kinetic
characteristic can be described by the pseudo-second-order kinetic equation. The amount of adsorption increases from 22.92
to 142.21 mg g−1 with the decrease of tea waste dosage from 100 to 10 mg for solution with an initial uranium concentration of 50 mg L−1. Desorption for the four strippants is higher than 80 %. The equilibrium data are more agreeable with Freundlich isotherm
than Langmuir isotherm.
Authors:Wang Mingming, Xie Hongqin, Tan Liqiang, Qiu Jun, Tao Xingquan, and Wu Cuiping
Herein, the sorption properties of Eu(III) on Na-attapulgite were performed by using batch sorption experiments under different
experimental conditions, such as contact time, pH, ionic strength, humic acid and temperatures. The results indicated that
the sorption of Eu(III) on Na-attapulgite was strongly dependent on pH and temperature. At low pH values, the sorption of
Eu(III) was influenced by ionic strength, whereas the sorption was not affected by ionic strength at high pH values. The sorption
of Eu(III) was mainly dominated by ion exchange or outer-sphere surface complexation at low pH values, and by inner-sphere
surface complexation or surface precipitation at high pH values. The sorption of Eu(III) onto Na-attapulgite increased with
increasing temperature. The Langmuir and Freundlich models were applied to simulate the sorption isotherms, and the results
indicated that the Langmuir model simulated the sorption isotherms better than the Freundlich model. The thermodynamic parameters
(∆Go, ∆So, ∆Ho) were calculated from the temperature dependent sorption isotherms at 293, 313 and 333 K, respectively, and the results indicated
that the uptake of Eu(III) on Na-attapulgite was an endothermic and spontaneous process. The results of high Eu(III) sorption
capacity on Na-attapulgite suggest that the attapulgite is a suitable material for the preconcentration and immobilization
of Eu(III) ions from large volumes of aqueous solutions.
Authors:W. Dong, W. Li, H. Zhang, X. Wang, Z. You, C. Zhou, J. Du, and Z. Tao
The stability constants for tracer concentrations of Co(II) complexes with the red earth fulvic acid were determined at pH
3.8–6.8 and ionic strength 0.0010–1.0 mol/l by using the cation exchange equilibrium method and the radiotracer60Co. The effects of ionic strength and pH on the stability constants of 1∶1 Co(II) complexes were investigated, and it was
found that the stability constants of complexes of humic substances do not vary with ionic strength and pH in a manner similar
to that of simple complexes.
Authors:X.K. Wang, W.M. Dong, H.X. Zhang, and Z.Y. Tao
The distribution coefficients,Kd of 36 elements from Na to Bi on a silica were determined at pH 4, 7, 9 and in the absence and presence of fulvic acid (FA) using a multitracer technique. The multitracer solution was prepared by irradiation of Th(NO3)4 with 40Ar ion beam. The effects of pH and fulvic acid on the Kd values of 36 elements were studied. It was found that the sequences of the Kd values of alkali elements (Cs>Rb>K>Na) and of alkaline earth elements(Ba>Ca>Mg) in the absence of FA can be qualitatively explained in terms of chemical bond formation and hydration. Various effects of pH and the negative or positive effect of FA on the adsorption of 36 elements were observed and are probably related to the species of 36 elements in the aqueous solutions containing CO32–, OH–, Cl– and FA. For most of the elements studied here the Kd values are increased with increasing pH and are decreased with adding FA.
Authors:Jing-Hua Li, Ning Zhang, Xiao-Tao Li, Jin-Yun Wang, and Sheng-Jun Tian
The stability of the inclusion complex of β-CD with cinnamic aldehyde was investigated by means of TG and DSC. The mass loss takes place in three stages: dehydration occurs at 50–120°C; dissociation of β-CD·C9H8O proceeds in the range 200–260°C; and decomposition of β-CD begins at 280°C. The kinetics of the dissociation of β-CD·C9H8O was studied by means of thermogravimetry both at constant temperature and with linearly increasing temperature. The results demonstrate that the dissociation of β-CD·C9H8O is dominated by a one-dimensional diffusion process. The activation energyE is 160 kJ mol−1, and the pre-exponential factorA is 5.8×1014 min−1. Scanning electron microscope observations and the results of crystal structure analysis are in good agreement with those of thermogravimetry.
Authors:Wang Zaihua, Li Xinjun, Song Wenji, Chen Jinfa, Li Tao, and Feng Ziping
A series of Ag-doped Ag–V/TiO2 catalysts with low vanadium loadings were prepared by one-step sol–gel methods and the effects of the Ag doping on the selective catalytic reduction (SCR) of NOx with NH3 were investigated. The catalytic activity of the catalysts increased about 20% by the addition of 1–3 wt% of Ag. The catalysts were characterized by XRD and H2-TPR. The results indicated that the V and Ag were well dispersed on the TiO2 support and the Ag doping inhibited the growth of TiO2 anatase crystallite and improved the oxidation ability of adsorption sites. The reduction temperature of vanadium oxide decreased and the activity for NH3-SCR enhanced. The doped Ag also had NH3-SCR activity, but it was very low. The durability of the catalysts was acceptable and the resistance to H2O was not very good. The effects of the calcination temperature and GHSV were also investigated; it was found that the optimal calcination temperature was 450 °C and the GHSV should not be higher than 48,000 h−1.
Authors:Na Zhou, Tao Li, Lianfeng Ai, Chunhai Guo, Juan Zhang, Shan Fu, and Qiao Wang
Lacosamide, a new type of antiepileptic drug, was subjected to forced degradation under the conditions of hydrolysis (acidic and alkaline), oxidation, dry heat, and photolysis to characterize its possible degradation products. The drug showed significant degradation under acidic, alkaline and oxidative conditions. The degradation products were separated on an Agilent Zorbax SB-C18 column with gradient elution using a mobile phase consisting of acetonitrile and ammonium acetate (0.002 mol/L) with formic acid as additive. A combination of liquid chromatography hybrid triple quadrupole-linear ion trap mass spectrometry (LC–QqLIT-MS) and liquid chromatography hybrid ion trap/time-of-flight mass spectrometry (LC-IT/TOF-MS) was used to identify degradation products. A total of 7 products including 4 novel degradation products were characterized. The mechanisms of degradation products of lacosamide were discussed. Application of the method to study degradation products of lacosamide provided fragment information, allowing further investigation of the degradation pathways and intrinsic stability of the drug.