(618ae) Synthesis of Carbonaceous Nano-Materials and Their Solid-Phase Adsorptivity

This study was intended to develop a solid-phase adsorbent based on carbonaceous materials embedded on zirconia (ZrO₂) spherical carriers. This study used thermal chemical vapor deposition (TCVD) process at atmospheric pressure for growth of carbon nano-material, including carbon nanosphere (CNS), carbon nanocapsule (CNC), carbon onion, and carbon web-like structures. In the preliminary study, wet impregnation process was conducted to coat nickel (Ni) as catalyst precursor on the surface of substrates, followed by using TCVD process with methane as carbon source, argon as carrier gas, and hydrogen as initiator. The structural and physical characteristics of the carbon products were determined using scanning electron microscopy, transmission electron microscopy, energy dispersive spectrometry, X-ray diffractometry, and Raman scattering spectroscopy. The results of these micro-analyses were used to evaluate the effects of individual process parameter on the carbonaceous material characteristics. The ensuing solid-phase adsorption studies were then performed to characterize the sorption properties of the materials associated with their physical characteristics. In this work, phthalic acid esters (PAEs) were used as the compounds of interest for the solid-phase adsorption studies. PAEs are commonly used in plastic industry, and are most widely used as plasticizer in products such as plastic toys, medical devices, food wrap, perfume and nail polisher. They are categorized as endocrine disrupting compounds (include sex hormone and the thyroxine) and some of them are suspected carcinogens. In Taiwan, PAEs reportedly exist in seawater and freshwater in very low concentration range (0.1 ~ 300 μg/L). The work therefore uses a representative PAE, namely diethyl phthalate (DEP) as the testing compound. Preliminary adsorption test results indicate that CNC and carbon onion materials both achieved DEP adsorptivity in the range of 80 μg/g at DEP solution concentration of 5 mg/L, and 110 μg/g at DEP solution concentration of 10 mg/L. The web-like carbon structure attained approximately 50 μg/g at DEP solution concentration of 5 mg/L. Additionally, DEP adsorption capacities of CNC and carbon onions were both higher (12.0 μg) than that of commercial adsorbent Tenax TA (4.1 μg).