Synthesis of submicron spherical Fe-MCM-48 with actual gyroid like structure.

Highly ordered submicron spherical Fe-MCM-48 was successfully synthesized by a mixed surfactant method using cheap water glass as silica source. The gyroid like structure of MCM-48 was captured by a TEM image for the first time, and it was corresponded well to the previous simulated gyroid model. A tentative mechanism of homogenization cooperative process involving the Helmholtz double electrical layer was purposed. After the loading of metal Ag, the resulting Ag/Fe-MCM-48 catalyst showed good catalytic performance in the catalytic combustion of benzene.

One-step synthesis of Ti-MSU and its catalytic performance on phenol hydroxylation.

In this study, high-quality Ti-MSU was synthesized by a convenient one-step hydrothermal synthesis procedure. This is the first detailed study on the role of addition time of a Ti source. We found that the addition time of the Ti source can effectively influence the structure and morphology of the product by adjusting the balance of hydrolysis-polymerization and nucleation-aggregation in different self-assembly steps. The optimum synthesized Ti-SMU sample showed a good catalytic performance on the phenol hydroxylation.

Synthesis of high quality MCM-48 with binary cationic-nonionic surfactants.

Highly ordered MCM-48 was synthesized in the hydrothermal system of a mixture of cationic cetyltrimethylammonium bromide (CTAB) and nonionic poly(ethylene glycol) monooctylphenyl ether (Tx-100) using water glass as the silicon source. The effect of various factors, such as the amount of surfactant, CTAB/Tx-100, Si source, crystallization temperature, and crystallization time, on the synthesis were discussed in detail. The local effective surfactant packing parameter theory and the charge balance theory were used to explain the reason that various factors can affect the product structure reasonably. Especially, the role of Tx-100 was expounded. The optimum synthesis conditions for MCM-48 were obtained.

[Simultaneous determination of impurities in K2CrO4 by ICP-AES].

The trace elements, Ca, Mg, Ba, Co, Cd, Cu, Mn, Pb, Sr, Zn, Al, Fe, Ni, Ti, Si and V, in K2CrO4 were simultaneously determined by inductively coupled plasma atomic emission spectrometry (ICP-AES). Optimum spectral lines were selected for each analyzed element. The matrix effect was studied and eliminated through matrix matching. The results show that the linear correlations of standard curves are good (R2 = 0.998 6-1.000) under the determined conditions. The recoveries of standard addition are in the range of 83.7%-113.0%, and the relative standard deviations are lower than 9.48% (n = 9). Detection limits of these impurities are in the range of 0.075-2. 625 mg x kg(-1). The method is rapid, simple, accurate and credible, so it can be used for the determination of impurities in K2 CrO4 product. The results also show that there is relatively high content of Ca, Mg, Al and Si in K2 CrO4 product, so the K2 CrO4 product can't be directly used for the ion membrane electrochemical synthesis of chromic anhydride and the product must be taken for further purification.

Removal of Ca(II) and Mg(II) from potassium chromate solution on Amberlite IRC 748 synthetic resin by ion exchange.

Experimental measurements have been made on the batch ion exchange of Ca(II) and Mg(II) from potassium chromate solution using cation exchanger of Amberlite IRC 748 as K+ form. The ion exchange behavior of two alkaline-earth metals on the resin, depending on contact time, pH, temperature and resin dosage was studied. The adsorption isotherms were described by means of the Langmuir and Freundlich isotherms. For Ca(II) ion, the Langmuir model represented the adsorption process better than the Freundlich model. The maximum ion exchange capacity was found to be 47.21 mg g(-1) for Ca(II) and 27.70 mg g(-1) for Mg(II). The kinetic data were tested using Lagergren-first-order and pseudo-second-order kinetic models. Kinetic data correlated well with the pseudo-second-order kinetic model, indicating that the chemical adsorption was the rate-limiting step. Various thermodynamic parameters such as Gibbs free energy (DeltaG degrees ), enthalpy (DeltaH degrees ) and entropy (DeltaS degrees ) were also calculated. These parameters showed that the ion exchange of Ca(II) and Mg(II) from potassium chromate solution was feasible, spontaneous and endothermic process in nature. The activation energy of ion-exchange (E(a)) was determined as 12.34 kJ mol(-1) for Ca(II) and 9.865 kJ mol(-1) for Mg(II) according to the Arrhenius equation.