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年度	106	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	中原大學	申請系所	環境工程學系
專案主持人	趙煥平	職等/職稱	教授
專案中文名稱	利用層狀複合金屬氫氧化物即時合成特性去除地下水中鉻酸鹽之研究
中文關鍵字	狀複合金屬氫氧化物、鉻酸鹽、吸附、記憶效應、即時合成
專案英文名稱	Removal of chromate in groundwater by layer double hydroxides in situ
英文關鍵字	Layered double hydroxides, chromate, adsorption, structural memory, synthesized in situ
執行金額	800,000元
執行期間	2017/1/9 至 2017/11/30
計畫中文摘要	在過去地下水中的鉻酸鹽一直無法找到適當的現地處理方法，因此大部分地下水中鉻酸鹽是以抽出處理的方式將污染物去除，但抽出處理需耗費高處理成本，因此在本研究中期望發展出一種成本低且可以現地處理地下水中鉻酸鹽的技術。層狀複合金屬氫氧化物一種新興的材料，在過去較少被用於吸附污染，但其具有表面帶正電的特性，因此可有效吸附陰離子污染物，且合成之成本遠較陰離子交換樹脂便宜。除此之外，層狀複合金屬氫氧化物尚具備即時合成與記憶效應等特性，可以被應用於現地處理地下水中之鉻酸鹽，因此本計畫中將以此為基礎發展出現地處理地下水中鉻酸鹽之方法，同時測試吸附後鉻酸鹽在不同條件下的脫附狀況。 層狀複合金屬氫氧化物的主要成分為二價與三價金屬離子以及陰離子，在本研究中考慮使用常見的Mg2+與Al3+為陽離子金屬，NO3-、CO32-或Cl-做為可能測試之陰離子，利用即時合成之特性，在控制不同的溶液pH值下，將Mg2+與Al3+配置莫耳比3:1之濃度配合陰離子加入溶液中與不同濃度之鉻酸鹽混合，測試在不同時間下鉻酸鹽濃度變化，計算出吸附速率與最大吸附量。對於記憶效應方面，先以水熱合成法製作出層狀複合金屬氫氧化物，再將合成材料放在不同溫度下鍛燒，冷卻後將產品與鉻酸鹽混合攪拌，在不同時間下測定鉻酸鹽濃度變化，同樣計算出吸附速率與最大吸附容量。脫附實驗則是將已吸附鉻酸鹽之材料加入土壤與水混合系統，並於不同pH下進行脫附實驗，觀察脫附狀況，最後評估此方法在現場應用之可行性。 本研究目前所獲得的結果顯示，由XRD圖譜顯示以有效合成LDHs，且在表面性質分析中可以證實記憶效應的存在，LDHs由於表面帶正電荷可以吸附水中帶負電的鉻酸鹽，未鍛燒的LDHs對鉻酸鹽的最大吸附量可達192 mg/L，鍛燒後LDHs之吸附量超過308mg/g，即時合成對高濃度鉻酸鹽去除率可達70%，溶液的 pH值增加將使鉻酸鹽去除效率增加，LDHs對於鉻酸鹽的吸附量已接近離子交換樹脂，但成本卻遠低於離子交換樹脂，除此之外，經過脫附實驗後顯示，吸附於 LDHs之鉻酸鹽不易被脫附，因此可考慮應用於實場。 關鍵字: 層狀複合金屬氫氧化物、鉻酸鹽、吸附、記憶效應、即時合成
計畫英文摘要	In the past years, the most common method for chromate remediation in groundwater was the pump-and-treat proess. The proess is high cost in operation. Thus, the objective of this study is to develop a new method with low operation cost to remove chromate in groundwater in situ. The Mg-Al layered double hydroxides (LDHs) is a new adsorbent in the recent years. The LDHs with exchangeable anions can effectively adsorb chromate in the groundwater. The operation cost for LDHs is quite lower than that for anion exchange resin. In addition, the characteristics of LDHs possessing structural memory and synthesized in situ facilicate removing chromate in groundwater in-situ. The LDHs are intended to apply in adsorbing chromate in groundwater. Moreover, the desorption for chromate adsorption on LDHs under various environmental conditions are also investigated. The LDHs consist of metal ions with two and three valence electrons, and anions including NO3-、CO32-or Cl-. In this study, Mg2+ and Al3+ with molar ratio 3:1 and anions are added to solution containing chromate under the various pH values to synthesize LDHs. The adsorption rates and adsorption amounts for chromate are evaluated. For the structural memory effect, the LDHs can be synthesized using hydrothermal method, and then calcine them under different temperatures. The calcined LDHs mixed with chromate solution. The changes in chromate concentration in given period are analyzed. The adsorption rates and adsorption amounts for chromate can be estimated in the pr℃ess. For the desorption experiments, the LDHs adsorbing chromate are added in a soil-water system. The pH values of solutions are controlled ranged from 5 to 9. The released amounts of chromate from adsorbents can be mesaured. The obtained results indicated that LDHs with positive charge could adsorb chromate in the solution. The structural memory LDHs can be demonstrated using XRD patterns. The maximum adsorption capacity of chromate on LDHs is 192 mg/g. The adsorption amount of chromate in the structural memory experiment is more than 291 mg/g. LDHs synthesized in situ to remove chromate in the solution generated 70% of removal efficiency. The removal efficiency increased with the increasing pH of solution. According to cost and desorption, LDHs can be applied to remove dichromate in groundwater. Keywords: Layered double hydroxides, chromate, adsorption, structural memory, synthesize