鐵錳摻雜二氧化鈦奈米管對砷之去除

Abstract

本研究將二氧化鈦(P25)搭配三種鐵氧化物(FeO(OH)、α-Fe2O3、γ-Fe2O3)及水合二氧化錳(MnO2-H2O)於150℃下進行水熱合成，製備出二氧化鈦奈米吸附材，本研究針對TNT(100 wt.% P25)、α-Fe(10)(90 wt.% P25 + 10 wt.% α-Fe2O3)、FeO(OH)(10)(90 wt.% P25 + 10 wt.% FeO(OH))、γ-Fe(5)(95 wt.% P25 + 5 wt.% γ-Fe2O3)、Mn(2.5) (92.5 wt.% P25 + 5 wt.% γ-Fe2O3+ 2.5 wt.% MnO2)等五種奈米吸附材進行比表面積(BET)、傅立葉轉換紅外光譜(FTIR)、穿透式電子顯微鏡(TEM)、X射線光電子能譜儀(XPS)、X-ray繞射分析儀(XRD)等物性分析，並進行水中砷污染去除試驗，藉此比較各材料於相異毫克數、砷濃度與pH值下對三價砷及五價砷之吸附效率。研究結果顯示鐵摻雜較容易使吸附材結構形成管狀，提高吸附材之比表面積，經過水熱反應後奈米吸附材比表面積較原材料P25高出4-6倍，而鐵錳摻雜之比表面積又較無摻雜TNT高出18-28%。γ鐵摻雜能夠使吸附材形成更多氧空缺，這些結構缺位更容易使砷酸根吸附。20 mg之TNT、α-Fe(10)、FeO(OH)(10)、γ-Fe(5)、Mn(2.5)對15 ppm(100 ml)五價砷之吸附效果分別約為32%、33%、33%、38%及36%；20 mg之TNT、α-Fe(10)、FeO(OH)(10)、γ-Fe(5)、Mn(2.5)對15 ppm(100 ml)三價砷之吸附效果分別約為15%、16%、16%、19%及20%，所有材料皆於60分鐘達95%吸附飽和，而在不同pH值條件下對五價砷以及三價砷去除效率隨著pH值增加而降低。Mn(2.5)在避光吸附下對15 ppm之三價砷具38%之氧化效果，γ-Fe(5)具有最佳之吸附效率且粉末具有磁性有助於粉末快速沉澱及回收再利用。

In this study, Fe/Mn-doped TiO2 nanotubes were synthesized via hydrothermal process at 150oC by using P25, FeO(OH),α-Fe2O3, γ-Fe2O3, and MnO2-H2O at different ratios (0 wt.%, 2.5 wt.%, 5 wt.%, and 10 wt.%). After hydrothermal synthesis, physical properties were examined by using Brunauer-Emmett-Teller surface area analyzer (BET), Fourier-transform infrared spectroscopy (FTIR), Transmission electron microscope (TEM), X-Ray Photoelectron Spectroscopy (XPS), and X-ray diffraction analysis (XRD). TNT, α-Fe(10), FeO(OH)(10), γ-Fe(5), and Mn(2.5) were applied to remove arsenate (As5+) and arsenite (As3+) in the aqueous. As5+ and As3+ adsorption tests were carried out at different sample weight, arsenic concentration, and pH conditions. Experimental results show that higher specific surface area and better tubular shape were observed after hydrothermal synthesis. Specific surface area of Fe/Mn-doped material increases by 18%-28%, compared with TNT without Fe/Mn-doped. A more structural vacancy was observed in γ-Fe-doped materials, which could increase the arsenic adsorption efficiency. The adsorption efficiency of per 20 mg TNT, α-Fe(10), FeO(OH)(10), γ-Fe(5) and Mn(2.5) for 15 ppm (100 ml) arsenic aqueous are 32%, 33%, 33%, 38% and 36%, respectively. In the same test condition, the adsorption efficiencies of those materials for As3+ are 15% (TNT), 16% (α-Fe(10)), 16% (FeO(OH)(10)), 19% (γ-Fe(5)), and 20% (Mn(2.5)), respectively. In a dark experiment, Mn(2.5) can oxidize 38% As3+ into As5+. γ-Fe(5) is the best material for arsenic adsorption compared to the other material in this study. Moreover, the magnetic γ-Fe(5) properties of the powder contribute to precipitate and recycle more easily.