石墨相氮化碳應用於太陽光-UV/Chlorine氧化處理廢水中新興污染物效能之探討

Abstract

水資源利用是近年來備受關注的議題；其中，處理後廢（污）水回收再利用已蔚為世界潮流。然而，傳統廢水處理程序並不具備足夠的去除效能，導致藥品及個人保健品(PPCPs)不斷被引入環境水體中，而即使是微量的PPCPs也可能對生態系統和人類健康構成潛在危害。近年來，以陽光取代紫外線的可能性被提出，太陽光驅動的遊離氯系統(Solar/Chlorine)作為一種高級氧化處理(AOP)引起了越來越多的關注，也被視為水中消毒及PPCPs降解上相當具有前途的AOP。 太陽能是一種取之不盡用之不竭、乾淨、可再生的自然資源；其中的困難在於，到達地球表面的太陽輻射僅包含約3-5%的紫外線輻射。因此，石墨相氮化碳(g-C3N4)作為一種光觸媒，因其低成本和環境友善的特性而被用於本研究中，以期有效利用太陽能，支持Solar/Chlorine AOP的高效應用。 本研究建立了一種以g-C3N4作為光觸媒的太陽能驅動UV/Cl2 AOP。結果顯示，基於太陽能的AOP可以完全且快速地降解廢水中的acetaminophen和naproxen。光觸媒的存在也導致ibuprofen和fenoprofen的去除增強以及ketoprofen的降解減少。經過Solar/fine g-C3N4/Chlorine處理，ibuprofen和fenoprofen可移除達29% 和57%，相較於未添加觸媒，分別增加9% 和23%；而ketoprofen的移除效率則降低61%（在Solar/Chlorine AOP 中去除達89%）。 Solar/Chlorine AOP的應用可能會導致DBPs生成增加，其中，相較於UV/Cl2，DBPs的形成延時趨勢更長，DBPs濃度最初會先增加，再隨時間減少或是穩定。除了選擇合適的水源進行處理外，異質光觸媒（例如 g-C3N4）的存在也很重要，因為它可能透過產生大量的氫氧自由基來平衡鹵化反應，使DPBs的形成趨勢加速及濃度減緩。 本研究的結果表明，基於太陽能的AOP對於去除複雜基質中的PPCPs具有良好的有效性及可行性。透過一些策略，包含更有效率的異質光觸媒（例如改性g-C3N4）、太陽光聚焦系統或是更好的太陽輻射分佈等，可以達到更高的PPCPs去除效率，支持太陽能的AOP在未來的全面應用。

Pharmaceutical and personal care products (PPCPs) might pose potential hazards to the ecosystem and human health, even at trace levels. Due to the extensive use and incomplete removal by conventional wastewater treatment processes, PPCPs are continuously introduced into the water. Sunlight irradiation has been proposed as an alternative to conventional UV-driven advanced oxidation processes (AOPs). The solar photolysis of free chlorine system (Solar/Chlorine) has drawn increasing attention these years and has been considered a promising AOP in water treatment for disinfection and PPCP degradation. Solar energy is an inexhaustible, clean, and renewable natural resource; however, solar radiation reaching the surface of the earth contains only about 3–5% UV radiation. Therefore, graphitic carbon nitride (g-C3N4), as a photocatalyst, was applied in the present study due to its low-cost and environmentally benign feature for efficient solar energy utilization to support the application of Solar/Chlorine AOP. The present study established a solar-driven UV/Cl2 AOP with g-C3N4 as a photocatalyst. Solar-based AOPs could completely and rapidly degrade acetaminophen and naproxen in wastewater. The presence of the photocatalysts resulted in an enhancement in eliminating ibuprofen and fenoprofen and a decrease in ketoprofen. After the Solar/fine g-C3N4/Chlorine process, ibuprofen and fenoprofen could be removed by 29% and 57% with a 9% and 23% increase, respectively, while it was 61% lower in ketoprofen than without photocatalyst (89% removed in Solar/Chlorine AOP). The application of Solar/Chlorine AOP may lead to increased DBP formation, in which the formation trend of DBPs is drawn into a longer scale compared to UV/Chlorine, first increasing and then decreasing or stabilizing later. In addition to selecting the appropriate source waters for treatment, the presence of heterogeneous photocatalysts such as g-C3N4 is also essential since it may potentially balance the halogenation by producing a large amount of hydroxyl radicals, resulting in a decreasing trend and a lower concentration of DBP formation. The results of the present study showed the promising effectiveness and feasibility of Solar-based AOPs for removing PPCPs in complex matrices. Several strategies, such as a more efficient modified g-C3N4, a sunlight-focusing system, or a better distribution of solar irradiation, have shown improved effectiveness in the literature, supporting full-scale applications in the future.