Synthesis and characterization of magnetic organic montmorillonite: efficient adsorption of hexavalent chromium.

This research compared two potential adsorbents for the efficient adsorption of toxic hexavalent chromium. The non-magnetic material STAC-Mt and the magnetic material FeSO4-STAC-Mt were synthesized by a simple impregnation method using montmorillonite (Mt), octadearyl dimethyl ammonium chloride (STAC) and ferrous sulfate as raw materials. The structural and morphological characteristics of both adsorbents were investigated by BET, XRD, FTIR, Zeta, VSM, TEM, SEM and XPS techniques. SEM and TEM results clearly revealed that FeSO4-STAC-Mt had a more loosely curled structure than STAC-Mt and the existence of well dispersed diamond-shaped magnetic particles. The saturation magnetization intensity of 17.949 emu/g obtained by VSM further confirmed the presence of magnetite particles in FeSO4-STAC-Mt. Due to the superparamagnetic properties of magnetite, the adsorption performance of FeSO4-STAC-Mt was better than STAC-Mt. FeSO4-STAC-Mt adsorbed up to 43.98 mg/g of Cr(VI), meanwhile it was easily separated from the reaction mixture by an external magnetic field. Intermittent adsorption studies at pH, adsorbent dosage and time revealed a rapid Cr(VI) adsorption process. In combination with response surface optimization analysis, a removal rate of 98.03% of Cr(VI) was obtained at pH 5-6. The adsorption process was properly described by the pseudo-second-order kinetic equation and the Langmuir equation, and the adsorption process was chemisorption and single molecular layer adsorption. In addition, the removal of Cr(VI) reached 72.68% after five cycles, demonstrating the good stability of the FeSO4-STAC-Mt.

Catalytic wet peroxide oxidation degradation of magenta wastewater and preparation of FeOCl/montmorillonite.

The iron oxychloride/pillared montmorillonite (FeOCl/MMT) catalyst was prepared by wet impregnation method and solid melting method. Various characterization techniques were used to analyze the microscopic morphology and structure of a series of catalysts. Moreover, the catalysts were used to treat magenta-simulated dye wastewater through catalytic wet peroxide oxidation (CWPO) degradation. The magenta removal rate and chemical oxygen demand (COD) removal rate of the magenta-simulated dye wastewater were used to evaluate the catalytic performance of the catalyst, and the optimal catalyst preparation conditions were selected. The results showed that the solid melting method was more favorable to the preparation of the catalyst, and the COD removal rate of wastewater can reach 70.8% when the FeOCl load was 3%. Moreover, 96.2% of the magenta in the solution was removed. The COD removal rate of the magenta wastewater decreased by only 12.4% after the catalyst was repeatedly used six times, indicating that the catalyst has good activity and stability. The Fermi equation can simulate the reaction process of the catalyst treating magenta wastewater at high temperature.