A Size Effect of Nanoparticles for Arsenic Removal and Fischer-Tropsch Reaction

Abstract

Metal oxide nanoparticles have become an area of growing interest and importance in a wide range of fundamental studies and technological applications, due to their unique optical, electronic, magnetic, chemical, and mechanical properties. Furthermore, metal oxides nanoparticles are increasingly being associated with important environmental processes occurring in water and catalysts in synthetic fuel processes. In this thesis, we demonstrate Iron and cobalt oxide nanoparticle for environmental and catalytic application. In Chapter 1, we briefly summarized magnetic iron oxide nanoparticle, nano for oil and gas, and Design, synthesis, and use of cobalt-based Fischer-Tropsch synthesis catalysts. In Chapter 2, Magnetic multi-granule nanoclusters (MGNCs) were investigated as an inexpensive means to effectively remove arsenic from aqueous environment, particularly groundwater sources consumed by humans. Various size MGNCs were examined to determine both their capacity and efficiency for arsenic adsorption for different initial arsenic concentrations. The MGNCs showed highly efficient arsenic adsorption characteristics, thereby meeting the allowable safety limit of 10 g/L (ppb), prescribed by the World Health Organization (WHO), and confirming that 0.4 g/L and 0.6 g/L of MGNCs were sufficient to remove 0.5 mg/L and 1.0 mg/L of arsenate (AsO43−) from water, respectively. Adsorption isotherm models for the MGNCs were used to estimate the adsorption parameters. They showed similar parameters for both the Langmuir and Sips models, confirming that the adsorption process in this work was active at a region of low arsenic concentration. The actual efficiency of arsenate removal was then tested against 1 L of artificial arsenic-contaminated groundwater with an arsenic concentration of 0.6 mg/L in the presence of competing ions. In this case, only 1.0 g of 100 nm MGNCs was sufficient to reduce the arsenic concentrations to below the WHO permissible safety limit for drinking water, without adjusting the pH or temperature, which is highly advantageous for practical field applications. In Chapter 3, Fischer-Tropsch synthesis (FTS) reaction is a reaction used for producing hydrocarbon compounds from a gas mixture (syngas) containing carbon monoxide and hydrogen generated by reforming natural gas, gasification of coal, or biomass. This study provides a novel cobalt-based catalyst having an improved catalytic activity and stability, concurrently with an enhanced selectivity for liquid and high melting point hydrocarbons, at the expense of a low methane selectivity over conventional cobalt-based Fisher-Tropsch catalysts. We report on the conversion of synthesis gas to C5+ with enhanced FTS activity by a factor of 5, applying catalysts that constitute cobalt nanoparticles (using a polyether and promoters) homogeneously dispersed on silica supports.