零價鐵技術袪除三氯乙烯之研究; Study on Trichloroethylene Elimination by Zero-Valent Iron Technology

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题名:	零價鐵技術袪除三氯乙烯之研究;Study on Trichloroethylene Elimination by Zero-Valent Iron Technology
作者:	蔡璨樺;Tsann-Hwa Tsai
贡献者:	環境工程研究所
关键词:	零價鐵;三氯乙烯;反應動力;硝酸盬;腐植酸;zero-valent iron;trichloroethylene;reaction kinetic;nitrate;humic acid
日期:	2000-07-18
上传时间:	2009-09-21 12:12:50 (UTC+8)
出版者:	國立中央大學圖書館
摘要:	本研究之目的為針對零價鐵技術去除三氯乙烯（TCE）之反應行為進行探討。其中，藉由批次實驗的進行，本研究就不同溶氧態、起始TCE濃度、起始pH值、鐵粉添加量、硝酸鹽濃度及腐植酸濃度等因子，探討其對於零價鐵去除TCE之反應的影響。此外，實驗中並以SEM進行微觀分析，以觀察前處理及反應前後之鐵粉表面型態。實驗結果顯示，當鐵粉添加量為250g/L時，溶氧起始濃度(2.5~7mg/L)、TCE起始濃度(70~130mg/L)和起始pH值(3~9)，對於零價鐵還原TCE之去除率及反應速率常數皆沒有明顯影響，其平均反應速率常數為0.084h-1，半生期為8.26hr。不過，TCE去除速率會隨著鐵粉添加量的增加而提高，當增加1mg/L時，反應速率常數會增加0.03h-1。此外，本研究結果亦顯示，鐵粉經由酸洗及真空乾燥之前處理，具有相當優異的TCE去除能力，其基準化速率常數（KSA）為1.2 10-3 h-1m-2L，基準化半生期(t1/2,N, for 1m2/L)為0.58hr。而SEM觀察亦發現這些鐵粉表面具有許多的坑洞，推測可能具有較大的可反應表面。另一方面，在硝酸鹽與腐植酸同時存在的情況下，零價鐵去除TCE之反應會受到抑制。其中，當硝酸盬濃度介於20~100mg/L時，其抑制效果並無明顯的差異，此時，反應速率常數介於0.05~0.06h-1之間，然而，當硝酸鹽完全轉化為氨氮後，其K值則會回升至0.07~0.09 h-1之間，與未存在硝酸鹽時之速率常數值相近。此外，腐植酸對於零價鐵去除TCE的抑制效果，則會隨著腐植酸濃度的增加而提升，當腐植酸濃度為100mg/L時，其反應速率常數僅為未添加腐植酸時之30%左右。 The purpose of this study was aimed to investigate the reaction behavior of trichloroethylene (TCE) by zero-valent iron technology. By the batch tests, effect of dissolved oxygen, initial concentration of TCE, initial pH, amounts of zero-valent iron, nitrate and humic acid were studied to understand the performance and reaction kinetics of TCE elimination. Furthermore, the analysis of scanning electron microscopy (SEM) was carried out to observed the figure of iron surface with pretreatment of removing TCE. Experimental results indicated the effect of dissolved oxygen (2.5~7mg/L), initial concentration (1.3~61mg/L), and initial pH (3~9) was minimal for the removal and reaction rate constant of TCE elimination as the added amounts of iron was 250g/L. The average value of reaction rate constant and half-life was 0.084h-1 and 8.26hr respectively. However, the removal efficiency of TCE increased as the amounts of iron was increased. The reaction rate constant would increase 0.03h-1 per increasing 1mg/L of iron. Moreover, results revealed the removal of TCE was superior when the zero-valent iron was pretreated with the acid-washed method combining vacuum drying. The normalized rate constant (KSA) and half-live (t1/2,N, for 1m2/L) was estimated to be 1.2 10-3 h-1m-2L and 0.58hr respectively. The image of SEM also showed these grains of iron seemed to be gave greater specific surface. In addition, the reaction of TCE elimination was inhibited when the TCE coexisted with the nitrate or humic acid. As the nitrate concentration was maintained between 20 to 100 mg/L, the inhibition condition was similar and the reaction rate constant was in the range of 0.05 to 0.06h-1. However, when the nitrate was reduced to ammonia completely, the reaction rate constant of TCE elimination increased to 0.07 ~ 0.09h-1 as well as that without the coexistence of nitrate. Also, the inhibition of TCE elimination increased with the increase of humic acid concentration. When the humic acid concentration was controlled at 100mg/L, the reaction rate constant was reduced to 30% of that without the inhibition of humic acid.
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