微波電漿火炬製備氧化鋅與氧化鋅/鋁系複合粉體於染料移除之研究

本研究以硝酸鋅或硝酸鋅/鋁水溶液為前驅物，利用超音波霧化器將其霧化為微米尺度之液滴後，再經由載氣將其攜入電漿火炬中反應，形成氧化鋅（ZnO）或氧化鋅/鋁系複合粉體（ZAO），並應用於染料的移除。研究內容為探討電漿操作參數（功率、載氣與電漿氣體流率）與前驅物進料位置改變對產物之表面特性、結晶性、粒徑分佈、熱重損失、化學組成及比表面積之影響，並測試與探討其吸附與光催化的行為。在研究中發現前驅物所受的反應溫度扮演著重要的角色，當前驅物由下游端進入溫度較低的火炬焰尾中反應，所得到的ZnO與ZAO粉體皆以微米等級的球狀粉體為主，且結晶性與比表面積不佳導致光催化效果皆較差。但卻發現ZAO粉體對於陰離子型的染料具有極佳的吸附效果，但對於陽離子型染料則無吸附效果，經過各種材料分析與吸附實驗測試後，得知ZAO粉體具有層狀雙氫氧化物（LDHs）材料的特性，故對於陰離子型染料具有特殊的親和性，ZAO粉體對於甲基橙染料之最大吸附量可達355.87 mg/g。將前驅物進料位置改為由上游端進入溫度較高的火炬中心反應後，ZnO與ZAO粉體中奈米粉體所佔的比例會大量提升，且隨著提供的溫度愈高，則微米粉體所佔的比例會下降而奈米粉體則是增加，故得知溫度為微米粉體破碎並形成奈米粉體之關鍵因素。此外，ZnO粉體之結晶性與比表面積皆增加，使得其可供光催化反應之活性位置增加，故光降解染料的能力明顯提升。對於ZAO粉體原本對陰離子染料具有吸附效果之層狀結構會被破壞，使得其可供吸附的活性位置減少，故吸附效果會明顯下降，但其光催化效果則是大幅提升，因此為同時具備光催化與陰離子汙染吸附的材料。故本研究成功地利用微波電漿火炬分別製備出良好的陰離子汙染物吸附劑、光觸媒及同時具備光催化與陰離子汙染物吸附之材料。

關鍵字

微波電漿火炬、氧化鋅/鋁系複合材料、氧化鋅、光觸媒、吸附劑

並列摘要

In this study, ZnO and ZnO/Al2O3 composite particles (ZAO) were directly synthesized by spraying a mixed solution of zinc and aluminum nitrates in an atmospheric microwave plasma torch. The influences of plasma parameters on the properties of particle were investigated. In addition, the effects of precursor inlet position (downstream or upstream) were also discussed. The plasma-synthesized ZnO and ZAO particles were used for removing various dyes in solutions by adsorption and photodegradation. The results revealed that the temperature played an important role to particles preparation. As precursor was injected into lower-temperature region of flame tail in the ‘downstream’ process, the main structure of both ZnO and ZAO were micron-sized hollow particles and the performance of photocatalysis was weak due to lower crystallinity and surface area. Interestingly, ZAO particles showed excellent adsorption efficiency for anionic dyes but almost no adsorption for cationic dyes. Furthermore, it was confirmed that the properties of ZAO particles were similar to layered double hydroxides (LDHs). Therefore, ZAO particles had a good affinity to anionic dyes and the maximal uptake of anionic methyl orange was 355.87 mg/g in this study. When precursor droplets were injected upstream from the plasma, the precursor passed through high-temperature region, there were more nanoparticles formation and less micron-sized hollow particles for both ZnO and ZAO. As a result, gas temperature was identified as a key parameter that controls micron-sized hollow particles shattering into nanoparticles. It was also shown that the photocatalytic activities of ZnO were increased because of higher crystallinity and surface area. On the other hand, adsorption capability of ZAO decreased but photocatalytic activities of ZAO increased due to collapsing of LDHs structure and more stable ZnO or ZnAl2O4 formation. In summary, fine adsorbent and photocatalyst had been produced by microwave plasma torch.

並列關鍵字

plasma torch ； ZnO ； ZnO/Al2O3 composite particles ； photocatalyst

參考文獻

90.台灣歐姆龍健康事業股份有限公司, 超音波式噴霧劑,

91.蔡坤龍, 環境檢驗電子報第二十二期, 行政院環境保護署.

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微波電漿火炬製備氧化鋅與氧化鋅/鋁系複合粉體於染料移除之研究

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