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|標題:||Carbon Tetrachloride Degradation by Alkaline Ascorbic Acid Solution||關鍵字:||Ascorbic Acid;Carbon;Carbon Tetrachloride||Project:||Environmental science & technology, Volume 47, Issue7, Page(s) 3299-3307.||摘要:||
Ascorbic acid (AA) mediated electron transfer mayinduce reductive dechlorination of carbon tetrachloride (CCl4). Thisstudy investigated the role of AA in conjunction with the presence ofiron minerals over a wide pH range for the reduction of CCl4 inaqueous systems. The results indicate that CCl4 was reduced by AA ata pH of 13 (>pKa2, AA of 11.79) and chloroform (CHCl3) was atransformation byproduct of CCl4. When CCl4 levels were reduced tonear complete disappearance, the decrease of CHCl3 was thenobserved. The degradation rate of CCl4 and also the formation rate ofCHCl3 increased with increased AA concentrations. Analysis ofreaction kinetics between CCl4 and AA revealed an overall secondorderreaction with a rate constant of 0.253 ± 0.018 M−1 s−1.Furthermore, the reduction rate of CCl4 by AA at pH of 13 could beenhanced with the presence of iron minerals (Fe3O4, Fe2O3, FeOOH,and FeS2). In the absence or presence of iron minerals, the fraction of CCl4 transformed to CHCl3 was less than 1, indicatingsimultaneous one- and two-electron transfer processes. The end-products of AA at a pH of 13 included threonic acid and oxalicacid. This study highlights the potential of an alkaline AA solution for remediating chlorinated solvents.
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