- 學位論文
含汞活性碳生物溶出程序之可行性探討
Investigation of Removing Mercury from Activated Carbon Using Bioleaching Processes
摘要
全球固定污染源排放重金屬汞一直備受重視，而傳統空氣污染設備對於汞難以有效去除，容易影響人體健康與環境危害。現階段針對汞污染防治方法，主要以吸附劑的噴入為最可行之技術，因此產生許多廢棄活性碳，一般業者在活性碳吸附飽和後，處置方式多為掩埋，以環境的觀點來看，若處理不當，便有可能造成二次污染。然而，本研究之主要目標為研發新的硫化活性碳生物之再生技術，利用硫氧化菌之氧化及產酸能力，建立活性碳中汞生物溶出程序，將還原態的硫氧化，使汞從活性碳中溶出，提昇汞之脫附效率，以達到硫化活性碳再生及回收再利用之目的。 利用土壤馴養結果顯示，隨著馴養次數增加，其硫氧化菌之活性增加且越穩定，可將馴養時間縮短至10到15天。使用活性碳馴養方面，硫氧化菌較難以利用活性碳上的硫，因此添加培養基和可溶性營養源，有助於馴養的效率。另外，活性碳再生實驗中發現，當活性碳濃度越高時，pH值下降速率較快，但硫酸鹽生成量卻減少，而汞的去除率約為20到40%之間。將數據收集完成建立反應曲面圖，可得知最佳操作條件為活性碳濃度10%，接種菌液濃度20%時，汞之去除效率可以達到40%左右。經由物化分析後，發現活性碳表面中的含硫基質，藉由硫氧化菌直接氧化，或是產生硫酸使pH值下降，氫離子與活性碳中的汞進行置換反應，因此造成氫含量上升，而硫含量下降之情形，證實生物淋洗的直接反應與間接反應有在發生。當活性碳生物淋洗後，其比表面積從588.5 m2 g-1上升至757 m2 g-1，且孔徑從1 nm變大並集中於2 nm，其硫氧化菌的氧化反應對於表面具有相當影響，有助於未來再利用之可行性。
並列摘要
People have been paying attention to the emission of heavy metals (mercury) from stationary sources of air pollution; the traditional air pollution control facilities, however, is so difficult to have a great effect on removing mercury that human health and environment are facing a huge jeopardy. At present, the main prevention method of mercury pollution is adsorbent injection which is the most feasible way today. By such method, an amount of discarded activated carbon would be produced and then be buried or burned. From the environmental point of view, it might cause secondary pollution when the activated carbon was dealt with improperly. Therefore, this study attempted to develop a new bioregeneration technology of presulfurized activated carbon. The bioregeneration technology relied on the oxidization and acidification of Acidithiobacillus thiooxidans to carry out a bioleaching process of activated carbon. That means in the activated carbon, sulfur was oxidized and mercury was leached then. It could advance the desorption efficiency of the mercury and regenerate/recover the presulfurized activated carbon. This study includes the acclimation of soil and the acclimation of activated carbon. According to the results of this study, the more times of acclimation soil had; the better activity of At. thiooxidans performed. The period of soil acclimation decreased to 10-15 days. As to the acclimation of activated carbon, At. thiooxidans was difficult to utilize sulfur-impregnated activated carbon, so medium and soluble nutrition were added in order to increase the efficiency of acclimation. Moreover, in the experiment on activated carbon regeneration it was showed that when the concentration of activated carbon was high, the value of pH decrease rapidly, and the production of sulfate is reduced (the removal efficiency of mercury was 20-40%). The response surface graph showed that the removal efficiency of mercury reached a peak of 40% around when the concentration of activated carbon was 10% and the concentration of culture was 20%. Through the physicochemical analysis, the study found that the sulfide on the surface of activated carbon was oxidized via At. thiooxidans or lowered the value of pH by the production of sulfuric acid. Finally, the washing flow’s direct response and indirect response were verified in this study. After washing flow, the specific area of the activated carbon was from 588.5 m2 g-1 to 757 m2 g-1. The finding is helpful for the recycling research and technology in the future.