增強鉛離子吸附於EDTA-矽烷修飾氧化石墨烯之感應耦合電漿原子發射光譜儀檢測研究

Abstract

氧化石墨烯(Graphene Oxide, GO)由於它擁有大比表面積與豐富含氧官能基，因此具備了高效率、高吸附量的優秀吸附劑條件，是目前研究中，重金屬鉛離子吸附量最大的奈米材料。本研究利用矽烷化學法將GO表面的羥基(-OH)與材料乙二胺四乙酸-矽烷(EDTA-Silane)中的矽形成共價鍵結，將合成材料命名為GO-EDTA，利用修飾後表面豐富的羧基群，增加吸附點位，進一步提升吸附量與吸附效率。 本研究設計四種實驗方式探討GO與GO-EDTA對於鉛離子之吸附能力，實驗一：等溫吸附平衡實驗，探討初始濃度對於吸附量的影響 ; 實驗二：吸附動力學實驗，探討時間對於吸附量的影響 ; 實驗三：不同pH值之吸附平衡實驗，探討在不同pH值下對於吸附量的影響 ; 實驗四：不同溫度下之吸附平衡實驗，探討不同溫度下對於吸附量的影響，四種實驗吸附前後的鉛離子濃度皆透過感應耦合電漿原子放射光譜儀(Inductively Coupled Plasma with Atomic Emission Spectroscopy, ICP-AES)進行測量。 合成材料的表面特性分析，採用傅立葉轉換紅外線光譜儀(Fourier-Transform Infrared Spectrometer, FTIR)與掃描式顯微鏡(Scanning Electron Microscope, SEM)進行驗證。並將吸附實驗數據以不同吸附模式進行分析，使用的模式有：Langmuir等溫吸附模式、Freundlich等溫吸附模式、偽一階吸附動力學模式、偽二階吸附動力學模式、Van’t Hoff吸附熱力學模式。 本研究成功運用矽烷鍵結法合成出GO-EDTA材料，於25°C下，GO與GO-EDTA之最大吸附量分別為251.05 mg/g、416.78 mg/g，提升約1.66倍，GO與GO-EDTA吸附達飽和時間由40分鐘降至約30分鐘，吸附時間縮短，初始吸附速率從42.88 mg/g.min提升至72.46 mg/g.min，另外，在25°C、45°C、65°C下，GO-EDTA之最大吸附量分別為416.78 mg/g、603.90 mg/g、713.07 mg/g，從25°C至65°C吸附量共提升1.71倍，總體而言，吸附點位的增加同時提升了吸附量與吸附效率，經判斷其吸附機制主要為化學吸附之離子交換吸附，而GO-EDTA吸附Pb2+過程為自發性的吸熱反應。期盼此GO-EDTA材料未來能應用於水質淨化、污水處理或生醫光電等多種領域。Graphene Oxide (GO) is an excellent adsorbent with high efficiency and high adsorption capacity, due to it’s large specific surfacearea and abundant oxygen-containing functional groups. Until to current study, GO is the largest adsorption capacity adsorbent of nano-material. In this study, using the hydroxyl group on graphene oxide surfaces through a silanization reaction between N-(trimethoxysilylpropyl) ethylenediamine triacetic acid to form a covalent bonding. The synthetic material named GO-EDTA. After modified, the abundant carboxyl groups on GO-EDTA which increase the adsorption sites. Further more to increase the adsorption capacity and adsorption efficiency. In this study, the adsorption ability of GO and GO-EDTA for lead ion was designed by four experimental methods. Experiment I : Isotherm equilibrium adsorption experiment, to study the effect of initial concentration on adsorption capacity. Experiment II : Equilibrium adsorption kinetics experiment, to study the effect of time on adsorption capacity. Experiment III : Differential pH value equilibrium adsorption experiment, to study the effect of different pH values on adsorption capacity. Experiment IV : Differential temperature equilibrium adsorption experiment, to study the effect of different temperature on adsorption capacity. The concentration of lead ions before and after the experiment was measured by Inductively Coupled Plasma with Atomic Emission Spectroscopy (ICP-AES). The Fourier transform infrared spectroscopy (FTIR) and Scanning Electron Microscope (SEM) were used to verify the surface properties of the composites. The experimental data were analyzed by different adsorption models, including Langmuir isotherm model, Freundlich isotherm model, Pseudo-first order model, Pseudo-second order model, Van't Hoff thermodynamics model. In this study, successfully using silanization to synthesis GO-EDTA. At 25 ° C, the maximum adsorption capacity of GO and GO-EDTA was 251.05 mg/g and 416.78 mg/g, which is 1.66 times higher than GO. The adsorption time of GO and GO-EDTA decreased from 40 min to 30 min. The initial adsorption rate was increased from 42.88 mg/g min to 72.46 mg/g min. Moreover, at 25 °C、45 °C and 65 °C, the maximum adsorption capacity of GO-EDTA were 416.78 mg/g、603.90 mg/g and 713.07 mg/g, which increase 1.71 times from 25 ℃ to 65 ℃. The mechanism of adsorption is ion exchange adsorption and GO-EDTA is spontaneous endothermic reaction process to adsorb Lead ions. It’s expected that GO-EDTA will be used in various application such as water purification, sewage treatment or Biophotonics.