以顆粒活性碳吸附全氟丁烷磺酸及其微波再生之研究

Abstract

全氟化合物為具有良好的疏水及疏油特性，被廣泛運用於工業與民生用品中，但長碳鏈全氟化合物 (C8) 被證實具有持久性、生物累積性、毒性而逐漸被淘汰，轉而使用毒性及生物累積性較小的短碳鏈替代品 (C4)，如全氟丁烷磺酸 (Perfluorobutane sulfonate, PFBS)。然而，隨著使用量的上升，C4在環境中陸續被檢測出來，且因相關資料的缺乏導致風險評估困難，使得發展去除C4技術成為重要的議題。 本研究以A、MU、F400三種廠牌之顆粒活性碳在不同pH值下吸附PFBS，探討其吸附動力學及等溫吸附線。結果顯示，在pH值為3時皆有最大的吸附速率 (F400>MU>A) 及吸附量 (F400>A>MU)。吸附動力模式中，皆較符合擬二階動力模式；等溫吸附模式中，A與F400較符合Langmuir等溫吸附理論，而MU較符合Freundlich等溫吸附理論。 在活性碳再生的部分，將吸附飽和之活性碳透過調整微波功率及時間，探討最佳再生效率之條件。結果顯示，A、MU在功率450 W、微波時間5分鐘，F400在功率450 W、微波時間15分鐘時有最大再生效率，分別為77.95、92.64、81.06 %。 在BET分析中，A、F400的比表面積有下降、MU有上升的現象；EDS分析中，吸附飽和之活性碳在微波後，F元素有下降的趨勢。 再生效率以及吸附量皆會隨著再生次數越多而降低。A在第2次微波後再生效率下降，MU呈現隨再生次數增加而緩慢下降，第4次微波仍有76.95 %，F400在第4次微波後下降至71.77 %。以吸附量來看，每次微波由大至小皆為F400>MU>A。

Perfluorinated chemicals (PFCs) which have great hydrophobic and oleophobic properties are widely used in industrial and household products. Among these, long-chain PFSs (C8) have been eliminated gradually due to their persistent, bioaccumulation and toxicity. Instead, C8 are substituted with short-chain PFSs (C4) such as perfluorobutane sulfonate (PFBS), with low toxicity and bioaccumulation. However, with the increase in usage, C4 has been detected in the environment, and the lack of relevant information has led to difficulties in risk assessment, making the development of C4 removal technology an important issue. In this study, three brands of granular activated carbon, A, MU, and F400, were used to adsorb PFBS at different pH, and kinetics and isotherms were discussed. The results show that all had the maximum adsorption rate (F400>MU>A) and adsorption capacity (F400>A>MU) at pH 3. In the adsorption kinetics, the pseudo-second order model fitted all the adsorption data well; in adsorption isotherms, A and F400 were better described by the Langmuir isotherm, and MU was better described by the Freundlich isotherm. In microwave regeneration part, the power and time would be adjusted and applied to the saturated activated carbons to find the best regeneration efficiency. The results show that A and MU at 450 W for 5 minutes, and F400 at 450 W for 15 minutes had the maximum regeneration efficiency. The regeneration efficiency were 77.95, 92.64 and 81.06%, respectively. In the BET analysis, the specific surface area of A and F400 decreased, and MU increased; in the EDS analysis, the F element on the saturated activated carbons had a tendency to decline after microwave regeneration. Both the regeneration efficiency and the adsorption capacity would decrease as the time of regeneration increased. The regeneration efficiency of A decreased after the second microwave, and MU showed a slow decline with the increase of the times of regeneration. The fourth microwave still had 76.95 %, and F400 decreased after the fourth microwave. In terms of adsorption capacity, the order was F400>MU>A in each regeneration.