Chuang Xie

Formation and Transformation Behavior of Sodium Dehydroacetate Hydrates

The effect of various controlling factors on the polymorphic outcome of sodium dehydroacetate crystallization was investigated in this study. Cooling crystallization experiments of sodium dehydroacetate in water were conducted at different concentrations. The results revealed that the rate of supersaturation generation played a key role in the formation of the hydrates. At a high supersaturation generation rate, a new sodium dehydroacetate dihydrate needle form was obtained; on the contrary, a sodium dehydroacetate plate monohydrate was formed at a low supersaturation generation rate. Furthermore, the characterization and transformation behavior of these two hydrated forms were investigated with the combined use of microscopy, powder X-ray diffraction (PXRD), Raman spectroscopy, Fourier transform infrared (FTIR), thermal gravimetric analysis (TGA), scanning electron microscopy (SEM) and dynamic vapor sorption (DVS). It was found that the new needle crystals were dihydrated and hollow, and they eventually transformed into sodium dehydroacetate monohydrate. In addition, the mechanism of formation of sodium dehydroacetate hydrates was discussed, and a process growth model of hollow crystals in cooling crystallization was proposed.

Design and synthesis of core–shell Fe 3 O 4 @PTMT composite magnetic microspheres for adsorption of heavy metals from high salinity wastewater

In this study, a novel magnetic nanoparticles (MNP) modified by an organodisulfide polymer (PTMT) was designed for adsorption of heavy metals (Hg(II), Pb(II) and Cd(II)) from simulated coal chemical high salinity wastewater. The MNP-PTMT nano-composite was synthesize and characterized by SEM, TEM, FTIR, BET, VSM, TGA and XRD. The results indicate that the wanted MNP-PTMT magnetic nanoparticles were successfully obtained by modification. Adsorption experiments were systematically carried out to evaluate the performance of the obtained nanoparticles and to build up the adsorption models. The results demonstrate that the adsorption kinetic and isotherms thermodynamic followed the pseudo-second-order model and the Freundlich equation, respectively. In the presence of the inorganic salt in high salinity wastewater, the adsorption efficiency of MNP-PTMT for heavy metals was still excellent. The magnetic adsorbent could be recovered from aqueous solution by an external magnetic field in 20s and the subsequent regeneration of Hg(II)/Pb(II) loaded MNP-PTMT can be efficiently achieved by using EDTA-2Na solution as desorbent. The novel MNP-PTMT nanoparticles could be used reproductively for five times without apparent decrease in sorption capacity.

Confirmation of More Stable Polymorphic Form of Etoricoxib at Room Temperature

Polymorphic forms of etoricoxib have been reported in the literature, and form I was considered to be the most stable one. However, in this work, it was found that form I and form V are enantiotropic by differential scanning calorimetry analysis, solubility measurements, and solution-mediated polymorphic transformation experiments with form V being more stable than form I at room temperature. Thermodynamic transition temperature is determined as (353.45 ± 0.10) K. Besides, form V would transform to form I with the seeding effect of form I at high temperature below the melting point of form V. The crystal structure of form V was solved for the first time. The molecules in form V are linked by weak hydrogen bond C-H⋯O to form ring motif, which is nonexistent in form I.