Preparation, Modification And Analytical Applications Of MCM-48

MCM-48 mesoporous molecular sieves contain two independent three-dimensional pore systems and large surface area, which is more conducive to the transmission of the metal ions in separation applications. However, the formation of MCM-48 requires very critical synthesis conditions and large amount of surfactant when using single cationic surfaetant as template in traditional methods. To the best of our knowledge, until now there is no report on the application of MCM-48 for removing heavy metal ions. In this study, the mesoporous silicon would be prepared and charaeterized. The surface of MCM-48 also consists of amounts of free silicon hydroxyl-SiOH and -Si(OH)2, which can react with siliconalkyls and introduce alkyl, amino and sulfur hydroxyl into MCM-48. Thus, the different functional groups can be introduced by these active groups. Theirs adsorption charaeter would be studied, especially on the adsorption of the main pollutants such as heavy metal ions. So as to they can be applied in the end environment treatment, and give theirs contribution to the sustainable development. This thesis consists of four parts.1.The Ti-MCM-48 was synthesized by cationic surfactant cetyltrimethylammon-ium bromide(CTAB). MCM-48, SH-MCM-48, NH2-MCM-48 mesoporous molecular sieve was synthesized using mixtures of cationic surfactant cetyltrimethylammonium bromide(CTAB) and nonionic poly (ehthylene oxide)-poly(propylene oxide)-poly (ethylene oxide) treblock copolymer surfactant(Pluronic 123) as co-templates and tetraethylorthosilicate (TEOS) as silicon source. And X-ray diffraction(XRD), Scanning electron microscopy(SEM), N2 physical adsorption and Infrared spectrop-hotometry(IR) were used for characterization of resulting samples.2. The Ti-MCM-48 was used to adsorb cadmium, cobalt, nickel, manganese, zinc, copper and lead. The effects of solution pH, temperature, concentration and time on the adsorption were investigated. Optimum pH values for maximum adsorption were determined as 8.00. The maximum adsorption capacity by the Langmuir model was found to be 83.57 mg/g,9.870 mg/g,22.94 mg/g,14.10 mg/g,21.19 mg/g,17.76 mg/g and 50.25 mg/g for cadmium, cobalt, nickel, manganese, zinc, copper and lead respectively at 25℃. The kinetic experimental data properly correlated with the pseudo-second-order kinetic model (r2>0.999) at different temperature and different concentration.3. The SH-MCM-48 successfully removed lead, cadmium, copper and nickel. It is observed that the adsorption data fitted the Langmuir isotherm. The maximum adsorption capacity was 263.16 mg/g,133.33 mg/g,108.70 mg/g,62.50 mg/g for lead, cadmium, copper and nickel respectively at 25℃. The linear form of pseudo-second-order kinetics was applied at 25℃to the obtained results. The measured coefficient values of the pseudo-second- order model exceeded 0.999 and the calculated sorption capacity values obtained from pseudo-second-order model were more consistent with the experimental values of sorption capacity. The competitive adsorption showed the SH-MCM-48 have a better selectivity for lead. HNO3 and HCl as elutions can recover metal ions.4. Lead, cadmium, copper and nickel was handled by NH2-MCM-48. The adsorption capacity was 322.6 mg/g,158.7 mg/g,96.15 mg/g,161.29 mg/g for lead, cadmium, copper and nickel respectively. The kinetic experimental data properly correlated with the pseudo-second-order kinetic model. HNO3 and HCl as elutions can recover metal ions.