|摘要: ||本提案之研究目標，主要是針對含砷之飲用水對人體健康所造成之危害，此一國際性議題，提出一新穎處理技術，並評估該技術之有效性與經濟性。本技術之特點，乃串聯利用零價鐵在二氧化碳曝氣下之氧化還原機制，以及衍生自反應系統之氧化鐵覆膜的吸附機制，兩階段連續交互處理地下水中所含之砷。研究中將調查不同來源之水質影響效應，包括純水水質、實驗室模擬水質、以及現地之地下水水質。另外，本研究也將針對奈米鐵及微米鐵之顆粒大小，探討其對於砷去除之影響效應。最後，基於未來本技術之實用性考量，本研究亦將針對反應系統，進行槽體之水力及反應動力分析，進一步進行系統操作條件之最適化，以提供經濟性評估所需資料。本計畫預計以三年時間，完成上述目標，預期本計畫順利完成後，其具體成果，將包括以下四方面： (1).材料選擇：奈米級與微米級零價鐵在本研究系統之成效比較，以及其在砷去除機制中所扮演的角色，特別是在二氧化碳曝氣下，其綜合效應將可得到深入之瞭解。 (2).背景水質：砷之去除成效，除了其本身在不同pH 條件下，會以不同形態存在，因而，決定其被去除之難易度外，其存在於不同背景水質條件下，例如，硬度、鹼度、各種鹽類以及溶解性有機質等，對於砷在本系統中之去除成效，亦將得到進一步的釐清。 (3).反應動力：基本上來說，本研究對於砷之去除動力，主要包括有第一階段(Fe0/CO2)之氧化還原反應，以及第二階段之吸附反應(氧化鐵覆膜)；另外，在這兩階段中，因水中溶氧之存在(第二階段有空氣曝氣並迴流至第一階段反應槽)，對於從零價鐵所溶解出來之亞鐵，將被氧化產生氧化鐵，並與砷產生吸附或共沉澱，這些複雜之去除途徑，透過本計畫，將可清楚瞭解兩階段彼此間之反應動力關係。 (4).應用潛力：本研究之反應系統反應槽，屬於連續流之設計，它可以是封閉式之操作，也可以是開方式之連續操作，或者部份迴流/部份放流之組合操作，這樣的反應系統，很容易經由操作最佳化以及操作自動化實驗資料之取得，開發具商品化價值之新穎處理系統。|
In view of the international issue of arsenic-contaminated drinking water, which causes the hazard to human health, the goal of this proposal is to propose an innovative treatment technology and to evaluate its cost-effectiveness. The proposed technology for treating arsenic-contaminated groundwater features a serial combination of redox mechanism within the Fe0/CO2 unit as well as the adsorptive mechanism within the iron oxide-coated sand. This study will investigate water quality of various sources effect on the proposed system, including pure water, simulated water, and real groundwater. In addition, the iron particle size effect on arsenic removal will be also studied. Finally, considering future application of this treatment technology, both hydraulic and reaction kinetic analyses will be performed for the purpose of system operation optimization and economical evaluation. The proposed project is expected to be completed in three years. The anticipated outcomes of this proposal can be addressed in the following four aspects: (1). Iron material choice: both nano- and micro-scale zero-valent iron will be used in this study for their performance comparison, and their roles in the reaction system in the presence of carbon dioxide will be illustrated; (2). Background water quality: arsenic speciation controlled by pH conditions can lead to different degree of its being removed from the system. In addition, with the presence of other background species such as calcium, carbonate, anions, and dissolved organic substances can pose significant effect on the removal of arsenic species. These are to be demonstrated through this project. (3). Reaction kinetics: In general, the arsenic removal kinetics consists of redox reaction in the first stage (Fe0/CO2 process) and adsorptive reaction in the second stage (iron oxide coated sand process). Additionally, due to the presence of dissolved oxygen in the first and second stages, the ferrous ions dissolved from zero-valent iron will be oxidized into iron oxides, which may result in adsorption or co-precipitation of arsenic. Such complicated removal pathways between these two stages will be revealed through this project. (4). Potential of application: The studied reaction system was designed in a way of continuous flow. Hence the treatment system can be operated in a way of either closed or open system, or operated in a recycled mode. In other words, such system can be commercialized easily if operation optimization and automation information are available from the experimental data of this project.