二氧化鈦修飾乳清分離蛋白澱粉樣纖維於亞甲基藍光催化降解之應用

Abstract

二氧化鈦具化學穩定性及良好的光催化活性，常用於光催化反應中，當粒子降為奈米尺寸時，具有較高的表面能量及原子比例，使奈米粒子的催化活性提升，但高的表面能量同時造成奈米粒子易產生聚集現象，為了提升奈米粒子的分散性及回收率，將二氧化鈦奈米粒子固定於乳清分離蛋白類澱粉纖維上，以製備具有催化能力的奈米粒子-類澱樣蛋白原纖維複合材料。將乳清分離蛋白溶於去離子水中，以鹽酸調整pH至2，於80 ℃及60 rpm攪拌下，培養24小時形成乳清分離蛋白類澱粉纖維(WPI-AF)，將乳清分離蛋白類澱粉纖維與硫酸氧鈦混合，以尿素為沉澱劑，經由水熱法於110 ℃合成TiO2NP/WPI-AF複合材料。TEM結果顯示當使用WPI-AF載體時，TiO2NP粒子間的聚集明顯減少。在35 ℃下，以0.0075 mM的亞甲基藍為反應物，進行光催化降解亞甲基藍反應。以5 mM TiO2NP/WPI-AF或TiO2NP作為催化劑時，光降解2.5小時，亞甲基藍的降解率分別約為82 %和45 %，經過固定化程序的 TiO2NP催化活性大幅提升，光照3.5小時的條件下，TiO2NP/WPI-AF重複進行光催化反應10次，亞甲基藍光降解率仍達90 %，說明TiO2NP/WPI-AF複合材料具良好的光穩定性。

Titanium dioxide exhibits chemical stability and photocatalytic activity, and is often used in photocatalytic reactions. When the particles are reduced to nanometer size, they have high surface energy, which improves the catalytic activity of nanoparticles. However high surface energy of nanoparticles also leads to aggregation. In order to improve the dispersibility and recovery of titanium dioxide nanoparticles, we deposited titanium dioxide nanoparticles (TiO2NP) on whey protein isolate amyloid fibrils (WPI-AF) to produce the nanoparticle-amyloid fibril hybrid materials with catalytic capability.Whey protein isolate amyloid fibrils (WPI-AF) were first prepared at pH 2 and 80°C with 60 rpm stirring for 24 hr. Next, WPI-AF were mixed with titanium oxysulfate, and urea was used as a precipitant to synthesize TiO2NP/WPI-AF composites by the hydrothermal method. In addition, TiO2NP was produced by mixing titanium oxysulfate, and urea at the temperature of 110 °C. TEM results revealed that aggregation of TiO2NP was greatly reduced when WPI-AF support was used. The photocatalytic degradation of methylene blue was carried out at 35 °C with methylene blue at 0.0075 mM as the reactant. When 5 mM TiO2NP/WPI-AF or TiO2NP was used as the catalyst, the percentage photodegradation of methylene blue irrdiated by UV-C light for 2.5 hr was ~82 % or ~45 %, respectively, indicating that the catalytic activity of TiO2NP after immobilization was significantly improved. Irradiated by UV-C light for 3.5 hr, the percentage degradation of methylene blue photocatalyzed by the 10-time reused TiO2NP/WPI-AF still reached ~90%, indicating the nice photostability of synthesized TiO2NP/WPI-AF composite materials. The outcome of this study provide a nice example of applying amyloid fibrillary aggregates in catalysis.