| Summary: | 博士 === 國立成功大學 === 化學工程學系碩博士班 === 97 === This dissertation concerns the application of functional magnetic nano-adsorbent in enzyme separation and heavy metal ions recovery and PAA-coated multiwalled carbon nanotube in electrochemical detection. The adsorption of lipase from an aqueous solution by PAA-bound iron oxide magnetic nanoparticles was studied. Then the PAA-coated magnetic nanoparticles were further amino-functionalization using diethylenetriamine via carbodiimide activation and used for the recovery of heavy metal ions from aqueous solution. Finally, using PAA to dispersion carbon nanotube and PAA-coated multiwalled carbon nanotube composite modified Screen printed carbon electrode for the simultaneous determination ascorbic acid (AA)、Norepinephrine (NE) and Uric acid (UA).
The feasibility of the polyacrylic acid (PAA)-bound magnetic nano-adsorbent for the recovery of Candida rugosa lipase from aqueous solutions was studied. The adsorption percentage was strongly dependent on the solution pH. With decreasing pH, the adsorption percentage increased rapidly from 20% to 90% at pH 7-5.5 and 98% adsorption could be achieved at pH 4.5-3.5. The adsorption behavior followed the Langmuir isotherm with a maximum adsorption amount of 0.605 mg mg-1 and a Langmuir adsorption equilibrium constant of 14.5 mL mg-1 in 0.03 M phosphate buffer at pH 3.5 and 25�薡. The adsorbed lipase could be desorbed in 0.03 M phosphate buffer at pH 9, and no significant activity loss was observed after adsorption/desorption. According to the investigations on the pH effect, desorption, and activity assay, it was suggested that the lipase used in this work might contain 20% impure or inert protein. In addition, the electrostatic interaction between lipase and PAA was not significantly affected by the temperature at 15-35�薡, and both the adsorption and desorption of lipase were quite fast due to the absence of internal diffusion resistance. The whole result demonstrated that the PAA-bound magnetic nano-adsorbent could be practically used for the efficient and fast recovery of lipase.
A novel magnetic nano-adsorbent has been developed by the covalent binding of polyacrylic acid (PAA) on the surface of Fe3O4 nanoparticles and the followed amino-functionalization using diethylenetriamine (DETA) via carbodiimide activation. Transmission electron microscopy image showed that the amino-functionalized Fe3O4 nanoparticles were quite fine with a mean diameter of 11.2±2.8 nm. X-ray diffraction analysis indicated that the binding process did not result in the phase change of Fe3O4. Magnetic measurement revealed they were nearly superparamagnetic with a saturation magnetization of 63.2 emu/g Fe3O4. The binding of DETA on the PAA-coated Fe3O4 nanoparticles was demonstrated by the analyses of Fourier transform infrared (FTIR) spectroscopy and zeta potential. After amino-functionaliztion, the isoelectric point of PAA-coated Fe3O4 nanoparticles shifted from 2.64 to 4.59. The amino-functionalized magnetic nano-adsorbent shows a quite good capability for the rapid and efficient adsorption of metal cations and anions from aqueous solutions via the chelation or ion exchange mechanisms. The studies on the adsorption of Cu(II) and Cr(VI) ions revealed that both obeyed the Langmuir isotherm equation. The maximum adsorption capacities and Langmuir adsorption constants were 12.43 mg/g and 0.06 L/mg for Cu(II) ions and 11.24 mg/g and 0.0165 L/mg for Cr(VI) ions, respectively.
The use of PAA-coated multiwalled carbon-nanotubes (PAA-MWNTs) composite modified Screen printed carbon electrode (SPE) for the simultaneous determination ascorbic acid (AA)、Norepinephrine (NE) and Uric acid (UA). PAA-MWNTs composite was prepared by mixing of MWNTs powers into PAA aqueous solution under sonication. SPE surface was modified with PAA-MWNTs film by casting. The PAA-MWNTs/SPE is of a high surface area and of affinity adsorption via ion exchange for NE and hydrogen bonding mechanisms for UA, respectively. The PAA-MWNTs/SPE displayed excellent electrochemical catalytic activity towards AA、NE and UA, the oxidation overpotentials of AA was decreased and the enhanced oxidation peak currents significantly for NE and UA were observed at the PAA-MWNTs/SPE in phosphate buffer solution (0.1 M, pH 7.5). Differential pulse voltammetry was used for the simultaneous dertermination of AA, NE and UA in their ternary mixture. The peak separation between NE and AA, UA and NE was 228mV and 112mV, respectively. Therefore, the voltammetric responses of three compounds can be well resolved on the PAA-MWNTs/SPE, and simultaneous dertermination of these three compounds can be achieved. The calibration curves for AA, NE, UA were obtained in the range of 100~1000μM, 0~10μM, 0~30μM, respectively. The lowest detection limits (S/N=3) were 49.772μM, 0.131μM and 0.458μM for AA, NE and UA, respectively.
|
|---|
