- 學位論文
含二氧化鈦分子膜中孔洞材料用於光催化回收還原貴金屬鈀之研究
Recovery of noble metal by photocatalytic reduction using layered TiO2 on mesoporous SiO2
摘要
本研究首先為製備高表面積、規則孔洞之中孔洞材料(SBA-15、KIT-6)，並利用有機物嵌入與無機離子交換的反應方法嫁接二氧化鈦分子膜，再將所製備之功能性複合材料(nTi/SBA-15,nTi/KIT-6)用於選擇性吸附水中貴金屬離子(Pd2+)。利用掃描式電子顯微鏡/能量散佈分析儀(SEM/EDX)、穿透式電子顯微鏡(TEM)、 X光繞射儀(XRD)、比表面積分析儀(BET)等，進行觸媒材料的表面分析與鑑定。透過氮氣等溫吸附之飽和量來推算樣品之比表面積(BET surface area)，其測量結果顯示SBA-15之比表面積為751 m2/g、孔洞直徑為6.80 nm、孔洞體積為0.60 cm3/g.nm，KIT-6之比表面積則為794 m2/g、孔洞直徑為5.23 nm、孔洞體積為1.04 cm3/g.nm。本研究透過批次實驗與競爭實驗的解析獲得此材料吸附水中貴金屬離子的動力、理論還原效率與實際回收效率，SBA-15、Ti/SBA-15、2Ti/SBA-15與3Ti/SBA-15其材料對貴金屬鈀(Pd)的實際回收效率分別為0、31.51、48.37及13.42%；而KIT-6材料在不同迴流次數下以Ti修飾後的反應能力無明顯差異，其對Pd之回收率皆為50%左右。 批次實驗結果顯示，在適當條件操作下，經修飾後中孔洞材料能有效透過其光催化性質將液相溶液中之貴金屬離子(Pd2+)還原為零價金屬粉末(Pd0)，其最佳條件為: (1)以PdCl2溶液為貴金屬來源，並設定初始反應濃度為25-50 mg/L，(2)批覆二氧化鈦分子膜之中孔洞材料與貴金屬之重量比例為100：1.5，(3)設定UV光(365 nm)曝光時間為一小時，(4)控制反應系統pH值1-3之間。本研究遠程目標為建立貴金屬回收系統並實際應用在貴金屬回收製程上，藉以促進貴金屬回收技術之發展。
並列摘要
The main purpose of this study is to enhance the metal adsorption efficiency by fabricating nTi/SBA-15 and nTi/KIT-6. A series of titania modified mesoporous silicate (SBA-15、KIT-6) samples with variable reflux times have been synthesized from Pluronic 123. The nano-materials were characterized by scanning electron microscopy/energy-dispersive X-ray spectrometer (SEM/EDX), transmission electron microscopy (TEM), X-ray diffraction (XRD), and nitrogen adsorption-desorption surface area analysis (BET). The BET surface area, pore diameter, and the pore volume of SBA-15 exhibits 751 m2/g, 6.80 nm, and 0.60 cm3/g.nm, respectively. Meanwhile KIT-6 exhibits 794 m2/g, 5.23 nm, and 1.04 cm3/g.nm. Different experimental conditions such as initial palladium concentration, reflux times of materials, pH value, and illumination time were controlled to analyze the kinetic of metal recovery by photodeposition with catalyst of monolayered TiO2 coating on mesoporous SiO2. The Pd separation rate of SBA-15, Ti/SBA-15, 2Ti/SBA-15 and 3Ti/SBA-15 were 0, 31.51, 48.37 and 13.42%. However KIT-6, Ti/KIT-6, 2Ti/KIT-6, 3Ti/KIT-6 were 0, 46.21, 55.52, 44.82%, respectively. As we expected, monolayered TiO2 on mesoporous SiO2 performed well recovery ability of noble metal. The optimum operating values of material reflux times, initial palladium concentration, illumination time, and pH value for maximizing the recovery of noble metal have been determined to be twice(2Ti/SBA-15, 2Ti/KIT-6), 25-50 mg/L, 60 mins, 1-3. This research can apply on the increasing demands of noble metals, and maintain sustainable use in the future.