液相非熱電漿備製含氮二氧化鈦降解偶氮染料並結合陶瓷膜回收光觸媒之研究

LPNTP Prepared N-doped TiO2 for Azo Dye Degradation with the Catalyst Recovering System by Ceramic Membrane

鄭亦彣(Yi-Wen Cheng)

指導教授 ： 陳孝行

國立臺北科技大學/工程學院/環境工程與管理研究所/碩士(2009年)

摘要

本研究以液相非熱電漿技術來備製含氮二氧化鈦，同步改善光觸媒於可見光源下之光催化效益，並發展一新之連續式光催化反應槽；同時更進一步利用UF陶瓷薄膜 (孔徑為10 nm) 系統回收含氮二氧化鈦可行性探討。後續針對備製所得之含氮二氧化鈦其應用前後之光催化活性與其物理特性，如能隙變化、晶相結構、氮吸附等；是否會因降解汙染物之後有所變動等疑慮，連同含氮二氧化鈦之回收率及使用壽命等一併進行探討研究之。
本研究備製出淡黃色之含氮二氧化鈦 (TiOxNy) 光觸媒，分別進行、ESCA、XRD、TEM及EDS分析，由UV/Visible觀察到含氮二氧化鈦之吸收光譜紅位移至439 nm之可見光區域，能隙從原本3.2eV (DP-25) 降低至2.82eV (TiOxNy)，亦由XRD分析中發現，常溫常壓放電過程 (14.1W、40 min) 並不會改變二氧化鈦晶相，仍舊維持原來Anatase晶相。製備出之TiOxNy於可見光下 (光波長為419 nm) 進行偶氮染料 (Acid Orange 7) 降解，經12小時後，在氮掺雜比為TiO2：NH4Cl = 1：6時，其反應速率常數為0.1519 h-1；已明顯優於DP-25之反應速率常數 0.045 h-1之光催化活性，其TiOxNy光催化反應速率為DP-25的3.4倍。因此，備製出最佳之TiOxNy-1:6並加入曝氣源於可見光 (光波長419 nm) 下進行批次偶氮染料 (Acid Orange 7) 降解，約在10小時後，均可有效降解，最佳實驗條件為光觸媒添加量0.15 g/L、曝氣含氧量40%、曝氣流量200 mL/min。
在連續式可見光光催化系統中，於水力停留時間均控制在10小時，經反應16小時後，隨著曝氣含氧量增加反應去除效果增加，於曝氣含氧量40% O2時去除效果達61%，然在本研究光觸媒添加量範圍內，隨著光觸媒添加量增加反應效果亦增加，於光觸媒添加量為0.5 g/L時，反應去除率達96%，而光催化反應於pH = 2時反應去除效果為最佳。在陶瓷膜回收部分，反應在60分鐘之前，光觸媒TiOxNy顆粒回收率已達64%以上，在80分鐘後，光觸媒TiOxNy顆粒回收率超過83 %以上，當系統操作超過90分鐘以上，則回收率可達99.5%以上，且光觸媒於陶瓷膜分離程序中，光觸媒TiOxNy顆粒可被完全分離濃縮。回收後之光觸媒經光催化再利用後仍可再處理偶氮染料，然經回收多次後之光觸媒，其表面將會被染料佔據，而產生觸媒毒化現象，直接影響觸媒的重複使用性。然於曝氣條件下，則能延緩光觸媒毒化現象發生，增加其光觸媒回收再利用效率，亦讓光觸媒使用壽命可再次被延長。

關鍵字

液相非熱電漿 ； 含氮二氧化鈦 ； 可見光 ； 偶氮染料 ； 陶瓷膜

並列摘要

This study strives to improve the photocatalytic activity by liquid-phase non-thermal plasma (LPNTP) technology for preparing N-doping TiO2 and to develop a new continuous photocatalytic reactor. The study further attempts to recover N-dope TiO2 particles by using ceramic membranes system. The obtained yellow colour N-doped TiO2 photocatalysts was characterized with UV-Vis spectrophotometer, XRD, ESCA, TEM, and EDS, respectively. The UV-Vis spectrum of N-doped TiO2 showed that the absorption band was shifted to 439 nm and the band gap was reduced to 2.82 eV. The structure analysis of XRD spectra showed that the peak positions and the crystal structure were not changed by plasma-treating at 14.1 W for 40 min. The photocatalytic activity of N-doped TiO2 was evaluated by conventional decolorization method using Acid Orange 7 and visible-light (λ = 419 nm). Eighty-five percent of Acid Orange 7 was degraded under visible light irradiation for 12 hours. In the batch photocatalytic system, ninety percent of azo dyes were degraded under visible light irradiation for 10 hours in the optimum condition of TiOxNy-1:6 with oxygen.
In the continuous photocatalytic system, sixty-one percent of AO7 concentration was degraded under visible light irradiation for 16 hours. In the initial period of ultrafiltration, the recovery rate of N-doped TiO2 particles achieved 64%. After 80 min, the recovery rate for TiOxNy particles was more than 83%. When the ultrafiltration experiment was carried out for 90 min, the recovery rate reached 99.5%. This result indicated that the photocatalyst was recovered completely.
The lifetime assessment of photocatalyst was evaluated by reusing the photocatalyst experiment 10 times. The decrease in efficiency of the recycled catalyst is due to the deposition of azo dye molecule on the photocatalysts surface, resulting in the blocking of its active sites as well as poisoning of the catalyst. Under aeration condition, the photocatalysts reused lifetime was longer than that in without aeration which reduces catalyst poisoning.

並列關鍵字

Liquid-phase non-thermal plasma ； N-dope TiO2 ； Visible light ； Azo dyes ； Ceramic membranes

參考文獻

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