利用高溫過程藉由形成尖晶石以穩定化模擬的含銅鋁汙泥

Abstract

重金屬污泥在台灣為一產量甚大的有害事業廢棄物，其中含銅污泥產量為最大宗；若未加以處理及棄置，將嚴重汙染土壤及地下水，進而對人體健康與環境生態帶來負面的影響。因此本研究嘗試藉由高溫燒結，將模擬的含銅污泥轉變為尖晶石結構(CuAl2O4)，達到安定化的目的；並進一步藉由將所得之最佳燒結條件運用在實場污泥，探討其可行性。 實驗中探討之影響因子為：燒結溫度、燒結持溫時間、氯鹽含量，及銅鋁莫耳比。除了觀察重金屬溶出濃度外，並探討其與結晶形成效果和各影響因子間之關連。 結果顯示存在於試體中的氯鹽量會影響CuAl2O4的生成，沒有經過洗鹽的試體是無法形成CuAl2O4，並且在銅的溶出濃度亦沒有降低的趨勢；當針對洗鹽後擁有相同導電度之試體進行燒結，會發現當燒結溫度為1000℃時，尖晶石的形成效率越高，且有最低的銅溶出濃度；同樣的反應環境中的CuAl2O4濃度會隨氯鹽量的減少而增加，但氯鹽含量亦會影響試體燒結後之比表面積大小，因而雖然尖晶石的形成確實能夠明顯的降低銅的溶出濃度，但並非銅的溶出濃度僅與CuAl2O4形成的多寡有關；在配比上，當銅、鋁的莫耳配比為一比三時，在銅的溶出濃度和CuAl2O4的晶相生成上都有較好的表現。 將由模擬污泥所得一部分最佳燒結條件套用到實場污泥的燒結程序，包括燒結溫度1000℃、燒結持溫時間3hr，以及導電度範圍451~800 μs/cm。由燒結前後之TCLP結果可看出燒結確實大幅降低銅的溶出濃度；並且燒結後之溶出濃度比上試體的總銅濃度皆不到1%，顯示試體中的銅大部分都能夠藉由燒結被拘限在試體之中，達到安定化之目的。

According to the declaring statistics of the Environmental Protection Administration in Taiwan, 185,172 tons heavy metal sludge were produced in 2007, and the copper-containing sludge were the main part of all. Without suitable treating, the heavy metal may pollute soil and groundwater, then lead to some damages to human and environment. Therefore, the aim of this study is to stabilize the simulated copper-containing sludge by transforming the sludge into spinel structure (CuAl2O4) through sintering process, and the optimum sintering conditions of the simulated sludge were applied to the field sludge to evaluate the feasibility of performing. The result indicated that the amount of salts in the sludge influenced the formation efficiency of CuAl2O4. Without desalinating, CuAl2O4 was not found by sintering. In contrast, the CuAl2O4 can be found after sintering at 800 - 1100oC for 3hr with proper desalinating procedure, and there was the best formation efficiency of CuAl2O4 at 1000oC. Similarly, increasing of desalinating led to the higher formation efficiency of CuAl2O4, but the different amount of salts led to different surface area of CuAl2O4 crystal. Therefore, the leaching concentration of copper was not only related to the formation of CuAl2O4 crystal, but also influenced by different surface area. Furthermore, there was better performance of leaching result and CuAl2O4 crystal formation with the mole ratio between copper and aluminum was 1:3. The sintering conditions including the temperature 1000℃, the isothermal time 3hr, and the conductivity range 451~800 μs/cm were used on field sludge. To compare the TCLP results between the samples before and after sintering, there was a great amount of decreasing leaching concentration that confirmed the spinel structure can effectively decrease the leaching concentration of copper by fixing the copper ion in the spinel structure.