大氣電漿熔射法製備二氧化鈦膜及其於腐植酸與葡聚糖光分解之應用

Photodegradation of Humic Acid and Dextran Using a TiO2 Membrane Fabricated by Atmospheric Plasma Spray Coating

曾宇生(Yu-Sheng Tzeng)

指導教授 ： 童國倫

中原大學/工學院/化學工程研究所/碩士(2011年)

https://doi.org/10.6840/cycu201100689

摘要

本研究是利用大氣電漿熔射技術並結合高溫水蒸氣誘導機制（high temperature vapor induced mechanism, HTVIM），於氧化鋁基材上製備一層多孔二氧化鈦薄膜。研究中，主要藉由熔射參數的改變來探討其對薄膜結構和過濾效能之影響，並找到一最適化參數製備出具有光催化效能及抗污塞性能之薄膜。
研究結果發現，隨電漿功率的增加，粒子的飛行速度和溫度都會提升，使得沉積效果愈好。相較於噴塗氧化鋁粉末，當改變電漿功率且噴塗趟數為一趟時，由於二氧化鈦粒子與氧化鋁基材的熱膨脹係數不同及送粉量不足，導致粒子無法覆蓋完全而使基材部分裸露。隨著噴塗趟數的增加，膜厚逐漸上升，平均孔徑和純水透過量也隨之衰減。此外，研究中發現，噴塗趟數為2趟以上時，銳鈦礦比例明顯下降，將造成光催化效能降低，故不適合作為光觸媒材料。在送粉量的參數調整上，隨著送粉量的增大，使得基材上扁平粒子數增加，不僅造成膜厚度增加使得平均孔徑和純水透過量下降外，還使得銳鈦礦相的比例下降，降低催化效能。對於噴塗距離的大小，主要是影響粒子撞擊基材的強度和粒子飛行的時間，隨著噴塗距離的拉長，熔融粒子受大氣環境的影響愈大，雖然可使膜厚下降，平均孔徑和純水透過量上升，但銳鈦礦的比例也會隨之下降，影響催化性能。因此，由實驗結果可得知，當功率為21 kW且送粉量為0.135 g/s時，在噴塗距離為10公分下，可獲得一最適化的純水透過量、平均孔徑及銳鈦礦相比例之薄膜，並進行後續之過濾效能分析。
將最適化的熔射參數製備而成的二氧化鈦薄膜應用於光催化的效能測試和抗污塞性能實驗。研究結果發現，二氧化鈦薄膜在經過紫外光70分鐘照射下，RB5染劑可加速完全被分解，其反應速率常數為0.0764 min-1。此外，以單成分之聚葡萄糖及腐植酸分別進行抗污塞性能的過濾實驗，其結果發現，相較於一般過濾，在有光催化的過濾中，可使穩定透過量提升2倍以上，且薄膜阻力值也有明顯的降低。在濃度為2 ppm的腐植酸和平均分子量為450 kDa之聚葡萄糖有著較佳的分解效果，但腐植酸濃度達4 ppm時，由於薄膜污塞速度過快，導致二氧化鈦薄膜無法快速分解污染物，造成光催化效果降低。在阻擋率方面，藉由光催化的作用下，也對腐植酸的去除率有所助益，其去除效果最高可達至90 %。故藉由大氣電漿噴塗所製備的二氧化鈦薄膜，不僅能提高薄膜過濾效能，也同時具有抗污塞特性現象。

關鍵字

無機薄膜 ； 電漿熔射 ； 抗污塞 ； 光催化 ； 二氧化鈦

並列摘要

The membrane technology has been increasingly used for water treatment and wastewater reclamation due to the recent problems of the environmental pollution. To further improve the effectiveness of membrane process and reduce membrane fouling, photocatalytic TiO2 membranes with high porosity were prepared on macroporous Al2O3 support by the atmospheric plasma spraying（APS）approach. In order to enhance membrane porosity, commercial TiO2 particles were sprayed on the water implanted macroporous Al2O3 substrate to form TiO2 microfiltration membranes.
In this study, the optimized TiO2 membranes were prepared by tuning the spray parameters and applied for photocatalysis and anti-fouling test. The velocity and surface temperature of the flight TiO2 particles were enhanced as increasing the plasma power, resulting in the better deposition efficiency. However, the deposition efficiency was declined at the plasma power from 15 kW to 24 kW due to the different thermal expansion coefficient of TiO2 and Al2O3. The increase in the spray times and powder feeding rates result in the increase in membrane thickness and the decrease in average pore size and pure water flux of the TiO2 membrane. The photocatalytic efficiency was declined because the ratio of anatase to rutile phase was decreased at the spray time above 2 times or the larger powder feeding rates. In contrast, the increase in the spray distance cause the decrease in membrane thickness and the ratio of anatase to rutile phase and the increase in average pores size and pure water flux. As a result, the optimized parameters for the preparation of TiO2 membrane are 21 kW, 0.135 g/s and 10 cm for plasma power, powder feeding rate and spray distance, respectively.
The optimized TiO2 membrane was further used for the photocatalytic and anti-fouling test. The RB5 dyes were decomposed completely using TiO2 membrane after 70 min UV illumination, and photocatalytic rate constant is 0.0764 min-1. For the study of anti-fouling property, the permeable flux for the filtration of humic acid and dextran under UV light illumination is two times larger than that without UV light illumination. In addition, the photocatalytic efficiency at two different molecular weights of dextran (70 and 450 kDa) and three different concentrations of humic acid (1, 2 and 4 ppm) were also measured for comparison. The results show the best photocatalytic efficiency was occurred at the molecular weight of dextran of 450 kDa and the concentration of humic acid of 2 ppm, respectively. This work presents a simple and rapid way to prepare photocatalytic TiO2 membranes with a high permeate flux of pure water that can be used for the elimination of pollutants in water.

並列關鍵字

titanium dioxide ； anti-fouling ； atmospheric plasma spray ； photocatalysis ； inorganic membrane

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