成果專區 - 土壤及地下水污染整治基金補助研究與模場專案宣導網

專案基本資料

年度	99	專案性質	實驗性質
專案類別	研究專案	研究主題	整治
申請機構	國立成功大學	申請系所	地球動力系統研究中心
專案主持人	游鎮烽	職等/職稱	教授
專案中文名稱	利用磁性奈米鐵氧磁體尖晶石移除水體砷污染之研究
中文關鍵字	磁性奈米鐵氧磁體；磁性分離；五價砷
專案英文名稱	Removal of arsenic in aqueous solution using magnetic spinel ferrite Fe3O4
英文關鍵字	Magnetic nano-ferrite；Magnetic separation；Arsenate
執行金額
執行期間	2010/12/29 至 2011/12/28
計畫中文摘要	“砷(Arsenic)”，在自然水體及飲用水的污染事件中長久以來一直危害著人體生命安全，由於其廣泛被應用於除草劑、殺蟲劑、殺菌劑、乾燥劑和木材防腐劑、玻璃器皿製造、木材防腐劑、陶瓷製造業、冶金工業、製革廠、紡織業、染料廠、煉油工業、稀土金屬工業等用途，若不適當管制含砷廢棄物之流向，所造成的危害將導致環境與生態之浩劫，尤以飲用水及地下水汙染問題最令人頭痛，台灣雲林地區地下水即遭受嚴重威脅。“磁鐵礦(Magnetite, Fe3O4)”，又稱“鐵氧磁體 (Ferrite)”，近年來被應用於吸附含砷污染之水體在國際上已漸受重視，國內相關研究則寥寥無幾。本研究團隊即以水熱合成法(hydrothermal synthesis)自行合成奈米級之鐵氧磁體尖晶石，測詴其對水體中含砷污染之吸附效能。相關之研究成果為：1.完成磁性奈米鐵氧磁體生成條件之最適化研究；2.完成磁性奈米鐵氧磁體基本特性分析；3.完成鐵氧磁體(Fe3O4)吸附砷之最適化研究；4.五價砷之脫附及鐵氧磁體再生特性測詴；5.完成等溫吸附曲線及反應動力參數之求得；6.以磁性奈米鐵氧磁體處理受砷污染之地下水。研究成果顯示，在酸性環境下(pH 2 ~ pH 7)，吾人自製的奈米級鐵氧磁體吸附劑對砷有較佳的吸附移除效能，於不到 5 分鐘的時間內，即可有效的將液相中的五價砷吸附移除達 95 %以上，尤其在 pH 3 ~ pH 4 的條件下，吸附移除效率更可達 99.99 %以上。由等溫吸附曲線得知， pH 3、7、11 的飽和吸附量分別可達 14.35 mg/g、10.12 mg/g 及 4.88 mg/g，在 pH 3 至 pH 11 的操作區間，pH 愈低，As(V)的吸附移除效率有明顯增加的趨勢，吸附平衡參數結果顯示以 Langmuir Model 有較佳之模擬結果，反應動力部分，自製鐵氧磁體吸附五價砷較適合以擬二階動力模式來表示。此外，由 As K-edge XANES 研究結果發現，被吸附於鐵氧磁體上的五價砷並不會被其晶格內的二價鐵還原成更具毒性的三價砷，進而對水體環境產生更大的危害。在五價砷之脫附及鐵氧磁體再生特性測詴方面，本研究測詴常見的六種酸類及鹽類作為五價砷之脫附劑，於脫附條件為五價砷初始濃度 10 mg/L、溫度 25 oC、脫附劑濃度 0.1 M、鐵氧磁體 0.05 g、脫附劑體積 10 mL、脫附時間 30 分鐘的情況下，進行鐵氧磁體之砷脫附測詴，結果顯示吾人測詴之六種脫附劑的脫附效能以磷酸(H3PO4)最佳，磷酸鈉(Na3PO4)次之，硝酸(HNO3)最差，脫附效能之排序為 H3PO4 > Na3PO4 > H2SO4 > Na2SO4 > HCl > HNO3，其相應之五價砷脫附效率分別為 83.52 %、63.26 %、52.80 %、43.34 %、1.56 %、0.61 %。再生特性測詴結果發現，在初始五價砷濃度 500 µg/L，溫度 25 oC、磷酸濃度 0.02 M、鐵氧磁體 0.002 g、磷酸體積 10 mL、鐵氧磁體吸附時間 30 分鐘、磷酸脫附時間 30 分鐘的情況下，連續三次的吸脫附實驗發現，於吾人設定之操作環境下，鐵氧磁體隨著再生次數的增加對五價砷的吸附移除率有些微的降低，但移除效率仍可達 93 %以上，顯示自製磁性奈米鐵氧磁體具再生之可行性。為評估自製鐵氧磁體應用於實際受砷污染地下水之整治，吾人以磁性奈米鐵氧磁體處理受砷污染之地下水體。結果發現所採集之六口井砷的濃度範圍從 21.6 µg/L 至 84.3 µg/L，皆高於世界衛生組織(WHO) 對砷所規定的飲用水標準值 10 µg/L，若不經適當處理，則嚴重影響民眾健康。吾人於操作條件為吸附劑 Fe3O4 重量 0.05 g，地下水體積 10 mL，吸附時間 4 小時的條件下，測詴處理六口受砷污染之地下水水樣，結果發現，不論於中性(pH 6.84-7.65)或酸性(pH 1.61-3.30)吸附環境下，砷的移除效率皆達 91.7 %以上，所有地下水水樣之砷濃度均可降低至 WHO 所規定的飲用水標準值 10 µg/L 以下(最高的殘餘砷濃度為 7.0 µg/L)。此外，雖然鐵氧磁體於酸性環境下(pH < 2)有些許鐵的溶出，仍然顯示吾人自製之鐵氧磁體吸附劑有應用於受砷污染地下水整治之潛力。
計畫英文摘要	Arsenic (As) in groundwater and contaminated drinking water has been a major health risk impact in Taiwan and southeast Asia countries. Arsenic has been a common added ingredient in production of various industries, including herbicide, pesticide, antiseptic, wood preservative, glass and ceramic-ware, metallurgy, leather, textile, dye, and rare metals. This can easily cause serious impacts on surrounding environments, in particular groundwater and drinking water contamination, and ecological systems if no proper waste managing strategy or controlling policy. Similar high level of As in groundwater has been reported in the Yun-Lin county in central and Chia-Nan costal plan in southwestern Taiwan. Magnetite (Fe3O4), so-called Ferrite, is a common Fe oxide with spinel structure. It has received wide attention internationally in recent year for its capability to adsorb As in aqueous solutions. However, paucity effort was dedicated to related researches in science community in Taiwan. In this proposal, we apply well developed hydrothermal method to synthesize nano-particle size of ferrite and to conduct a series of batch experiments to evaluate its capability to remove As in aqueous solution under various pH, T, solution/ferrite ratio and ion concentration conditions. Our major efforts in the past year are: (1) accomplish the optimal synthesizing conditions of magnetic nano-ferrite; (2) accomplish the characteristics analysis of magnetic nano-ferrite; and (3) accomplish some adsorption experiments for As removal by magnetic nano-ferrite. The preliminary results showed the synthesized magnetic nano-ferrite has a great potential for removal of As even under acidic conditions, where the As(V) removal efficiency could reach more than 95 % in five minutes. In pH 3-4, the As(V) removal efficiency could reach than 99.99 %. From the adsorption isotherm, As(V) adsorption capacities were determined to be 14.35, 10.12 and 4.88 mg/g at pH 3, pH 7, and pH 11, respectively. In order to investigate the feasibility of magnetic nano-adsorbents in natural groundwater, six As contaminated groundwaters were sampled and tested for As removal in the laboratory. The total dissolved As concentration ranges from 21.6 to 84.3 µg/L, indicating all of the these groundwaters were potentially As contaminated groundwater (WHO limit: 10 µg/L). Our synthesized nano-ferrite were applied to remove As in these samples in the laboratory and found As removing efficiency of more than 91.7 % in all cases. Currently we are further evaluating the feasibility in ferrite treatment of the polluted groundwaters in natural sites.

跳到主要內容 :::