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Adsorptive performance of MCM-41 towards hg(II) in water. Adsorption and desorption studies

Zhai Q. Z., Hu W.-H., Guo X.-Y.

Environment Protection Engineering

2016

Vol. 42, nr 1

5--15

MCM-41 mesoporous material was prepared under a standard conditions by using cetyltrime-thylammonium bromide as a structure-directing agent and tetraethyl orthosilicate as silica source from the liquid phase at 80 °C. Powder X-ray diffraction and scanning electron microscopy used to characterize the product, showed that the MCM-41material had an average particle size of 110 nm. The synthesized material was used to investigate the effects of acidity, adsorption time, the concentration of Hg2+, adsorbent dosage and temperature on the adsorption of Hg2+. The results showed that the optimal adsorptive conditions were: pH 5.0, m(MCM-41):mHg2+ 6.67, temperature 20 °C and contact adsorption time 60 min, for the initial Hg2+concentration of 1.0 mg/cm3. The maximum adsorptive amount of Hg2+ was 56.48 mg Hg2+/g MCM-41. The results of the desorptive effect of three desorption agents such as HCl, HNO3 and HAc showed that the best desorbent was HCl at the concentration of 0.10 mol/dm3. The highest desorption efficiency was 77.21% for the desorption time 2 h.

Research on the Mechanism and Kinetics of Polymorphic Transitions of ε CL-20 in Composite Systems

Guo X.-Y., Zhang P., Xu J.-J., Wang Z.-H., Jiao Q.-J.

Central European Journal of Energetic Materials

2015

Vol. 12, no. 4

689--702

In order to explore the polymorphic transition law for ε-CL-20 in composite systems, the polymorphic transition process of pure ε-CL-20 crystals stimulated by heat was investigated by the X-ray Diffraction (XRD) method, and the kinetic parameters of the polymorphic transition process were calculated (including the apparent activation energy Ea and the pre-exponential factor lnA). Meanwhile the effects of different additives on the polymorphic transition process and kinetics of ε-CL-20 were explored in detail. The experimental results showed that the ε-form tends to transform into the γ- form on heating and that the Ea and lnA for the transition process were 209.97 kJ/mol and 57.47, respectively. The first group of additives clearly promoted the polymorphic transition of ε-CL-20 and lowered the initial transition temperature and the activation energy. The second and third groups of additives inhibited the polymorphic transition of ε-CL-20 and raised the initial transition temperature and the activation energy.