以奈米碳管催化之臭氧處理程序降解布洛芬及乙酰磺胺甲噁唑之動力評估

Abstract

在自然水體中，藥物和個人保健用品(pharmaceuticals and personal care products, PPCPs)時常被發現，並已經成為現今相當重要的議題。為了去除水中的藥物和個人保健用品，臭氧高級氧化處理(advanced oxidation process)是ㄧ項十分有效並被應用的方法。對於較難被臭氧分子降解的污染物，在系統中催化劑可以提高臭氧產生氫氧自由基(hydroxyl radical, .OH)的效率。 在本研究之中，多壁奈米碳管(multi-walled carbon nanotubes, CNTs)作為催化臭氧處理程序的催化劑。並將奈米碳管以不同的硝酸濃度(20%、40%以及70%)進行前處理，比較不同濃度的硝酸前處理的奈米碳管以及未改質之奈米碳管(pristine CNT)之催化效果。在本實驗中，分別去除兩種藥物和個人保健用品，包括ibuprofen以及acetylsulfamethoxazole。奈米碳管可直接與臭氧反應，亦可以在臭氧降解過程中的氫氧自由基鍊狀反應中扮演起始劑(initiator)、促進劑(promoter)以及抑制劑(inhibitor)的角色。在本研究中，未改質的奈米碳管及被不同濃度硝酸前處理過的奈米碳管之臭氧直接反應、起始反應(initiation)、促進反應(promotion)以及抑制反應(inhibition)的速率常數皆被測定。並發現直接反應及起始反應的速率常數隨著前處理的硝酸濃度的升高而增加，而促進反應及抑制反應的速率常數隨著前處理的硝酸濃度的升高而減少。此外，直接反應及起始反應的速率常數也會隨著pH值升高而增加，促進反應及抑制反應的速率常數則隨著pH值升高而減少。利用奈米碳管的四個速率常數、Rct概念以及臭氧的擬ㄧ階速率模式結合，可建立ㄧ個模擬污染物在催化臭氧中去除情況的模型，並有良好的去除效率預測。

The ubiquitous presence of pharmaceuticals and personal care products (PPCPs) in natural waters has been a major concern nowadays. To conquer this problem, ozone-based advance oxidation process has been applied to remove PPCPs. To improve the performance of ozonation, various catalysts have been introduced to enhance the formation of hydroxyl radical (.OH) to remove ozone-recalcitrant compounds. In this study, the performances of multi-walled carbon nanotubes (CNTs) pre-treated by different concentrations of HNO3 (20%, 40% and 70%) to catalyze the formation of .OH and the effectiveness to remove two PPCPs, namely ibuprofen and acetylsulfamethoxazole were evaluated. The rate constants of pristine CNT and four HNO3-pretreated CNTs in terms of direct ozone reaction, initiation, promotion and inhibition reactions were determined. It was found that the rate constants of direct ozone reaction and initiation increased with the increasing HNO3 concentrations used in the pretreatment while the rate constants of promotion and inhibition decreased with the increasing HNO3 concentrations used in pretreatment. In addition, the rate constants of direct ozone reaction and initiation increased with the increasing pH values while the rate constants of promotion and inhibition decreased with the increasing pH values. A model considering the determined rate constants was established to predict the catalytic effects of CNTs on the removal of ibuprofen and acetylsulfamethoxazole. The removal of these two PPCPs was enhanced when CNT was used as the catalyst in ozonation and the kinetics can be fairly well modeled by the developed model.