| Summary: | 碩士 === 國立宜蘭大學 === 環境工程學系碩士班 === 107 === The problem of the large amounts of waste products deriving from stone industrial affects not only the environmental impact but also the resources maintenance and the problem of waste management. This study presents the essential features of an environmentally attractive reuse of what is currently considered limestone sludge and marble sludge. A research is currently carried out in order to join this by-product with possible industrial. Accordingly, the aim of this study is to convert limestone sludge and marble sludge into nanocrystalline HA and to achieve control over the size and morphology of the HA crystals by hydrothermal technique, and utilize as an adsorbent for the removal of Pb and Cu from aqueous media. X-ray diffraction analysis confirmed that all powders were composed of a hydroxyapatite phase. The powders were of crystallinity (Xc =98.48-99.54%) The surface morphologies of the hydroxyapatite were examined via SEM and TEM analysis. That consist of aggregates of rod-shaped nanoparticles with a narrow size distribution. That the actual size of the precipitated crystals were 114-201 nm in length. The hydroxyapatite was classified as a typical IUPAC type-IV isotherm with an H3 hysteresis loop, indicating a mesoporous structure based on capillary condensation of N2 in mesopores, which was also confirmed by the measured average pore diameter of 10.25-20.45 nm. The BET surface area and total pore volume of the HAP were estimated to be 74.69-115.04 m2/g and 0.5339 cm3/g. Langmuir isotherm model (R2=0.98-0.99) seems to be the most accurate model and provides a better description for the equilibrium data compared to the other models. According to the Langmuir fitting, the theoretical maximum adsorption capacity was found to be 245.45 mg/g, and more than 99% of Artificial wastewater can be removed by the Hydroxyapatite. Thermodynamic analysis indicated that the process is thermodynamically spontaneous and endothermic process. Kinetic studies revealed that the adsorption process follows the pseudo-second-order model and that the overall adsorption rate is controlled by film diffusion as the dominant mechanism.
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