- 學位論文
鐵基金屬有機骨架於光觸媒薄膜反應器中移除有機廢水之應用
Utilization of Iron-based Metal–Organic Framework for Organic Wastewater Removal in Photocatalytic Membrane Reactor
摘要
近年因工業蓬勃發展，用水需求日漸上升，水資源又十分有限，因此廢水處理技術成為備受重視的議題；本研究將針對薄膜過濾程序及光觸媒氧化法進行探討，因其分別具有容易形成薄膜結垢及不易回收等缺點，故於實驗中將光觸媒材料固定於基材上，形成光觸媒薄膜反應器(Photocatalytic-membrane reactor, PMR)，提高觸媒回收率、降低膜汙染並提升系統穩定性，以實現連續處理程序。 本實驗利用溶熱法合成鐵基金屬有機骨架材料，MIL-53(Fe)，此材料具有良好光催化活性，為可見光觸媒材料(band gap=2.6 eV)，故可於照光180分鐘後達到約95%以上的苯酚移除率，但粉體觸媒回收率差，因此將MIL-53(Fe)塗佈不同次數於氧化鋁基材上，將其命名為xMIL@ (x為塗佈次數)，並在相同條件下光降解苯酚水溶液，其中以塗佈一次之效果最佳，可於照光180分鐘後達到98%以上的苯酚移除率，且具有良好的回收效率，在經過五次反應後，亦可以維持苯酚移除率約95%的穩定度。 接著，利用氧化鋁中空纖維膜(hollow fiber membrane reactor, HMR)過濾苯酚水溶液，僅達到約20%的移除率，且滲透通量穩定程度差，因此利用xMIL@與氧化鋁中空纖維膜以串聯的方式結合。並用金屬鹵素燈照射，形成光觸媒中空纖維膜反應器(Photocatalytic hollow fiber membrane reactor, PHMR)，可以發現相較於HMR系統，通量穩定度明顯上升，且再經過3次反應後依舊可達90%的苯酚移除效率且通量穩定，為4250±100 L/m2hbar，因此可以說明將光觸媒與薄膜結合具有實驗連續式廢水移除程序之可能性。 最後，利用xMIL@作為平板膜於金屬鹵素燈照射下，形成光觸媒平板膜反應器(Photocatalytic flat sheet membrane reactor, PFMR)，並在不同操作條件下進行掃流過濾程序，可以發現與單純氧化鋁平板膜之苯酚過濾程序相比，其苯酚移除率提升了2.6倍，在經過光源照射後，可以移除約73%的苯酚，且滲透通量亦更加穩定，反之，若xMIL@於PFMR中未經光源照射，則無法有效移除苯酚且滲透通量之穩定程度下降，故可以證明光催化反應的發生，有助於提升薄膜自潔效率。 因此，本研究成功將光觸媒與薄膜過濾系統相結合，所形成之光觸媒薄膜過濾反應器，可有效降低薄膜結垢且提升觸媒回收效率，並實現連續過程。
並列摘要
Water resources on earth are very limited, and the development of wastewater treatment technologies receives increasing attention. In this study, photocatalytic oxidation and membrane filtration system were integrated to overcome their disadvantages, for examples, difficult to be recycled and membrane fouling. In this experiment, the photocatalyst material was coated on the substrate to form a photocatalytic-membrane reactor (PMR) to improve the catalyst recovery efficiency, reducing membrane fouling and improving system stability to achieve a continuous operation in the process. In this work, MIL-53(Fe) was prepared by a solvothermal method as the iron-based metal organic framework. This material has good catalytic activity and visible light activity (band gap=2.6 eV). The batch-type system containing suspended MIL-53(Fe) can remove 95% of phenol under light irradiation after 180 minutes, however, it is difficult to be collected and recovered. Therefore, coating of MIL-53 (Fe) onto the alumina substrate, denoted as xMIL@ (x=coating times), can be used for phenol removal under light irradiation. The phenol removal efficiency using 1MIL@ shows the highest value of over 95% under light irradiation after 180 minutes among all the samples. The 1MIL@ also exhibited high stability for phenol removal efficiency of 95% after 5 cycles. In the following section, the hollow fiber membrane reactor (HMR) was used to remove phenol aqueous solution through filtration. And only 20% of phenol can be removed, and the flux was decreased gradually and unstable. Therefore, the series-integrated xMIL@ and the hollow fiber membrane as a photocatalytic hollow fiber membrane reactor (PHMR) was used, and it shows 90% of phenol removal rate and high flux, which are much higher than those of HMR. After 3 cycle test, PHMR maintained its removal rate of over 90%,and the flux of around 4250±100 L/m2-h-bar Finally, we simply used xMIL@ as a flat sheet membrane for phenol removal in a photocatalytic flat sheet membrane reactor (PFMR). Compared with alumina flat sheet membrane filtration system, PFMR has higher phenol removal efficiency and permeation flux stability. The 1MIL@ in PFMR also exhibits a higher phenol removal efficiency and flux under light irradiation, suggesting the MIL-53(Fe) enables to improve the self-cleaning property on the membrane. And we can prove that in the PFMR system, the occurrence of photocatalytic reaction is the main reason for improving the stability of flux. This study successfully combined the photocatalyst with the membrane filtration system to form a photocatalyst membrane filtration reactor. It can effectively reduce membrane fouling and improve catalyst recovery to achieve a continuous process.
參考文獻
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