کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
4547820 | 1627142 | 2006 | 19 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Investigation of gas production and entrapment in granular iron medium
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موضوعات مرتبط
مهندسی و علوم پایه
علوم زمین و سیارات
فرآیندهای سطح زمین
پیش نمایش صفحه اول مقاله
چکیده انگلیسی
A method for measuring gas entrapment in granular iron (Fe0) was developed and used to estimate the impact of gas production on porosity loss during the treatment of a high NO3â groundwater (up to â¼10 mM). Over the 400-d study period the trapped gas in laboratory columns was small, with a maximum measured at 1.3% pore volume. Low levels of dissolved H2(g) were measured (up to 0.07 ± 0.02 M). Free moving gas bubbles were not observed. Thus, porosity loss, which was determined by tracer tests to be 25-30%, is not accounted for by residual gas trapped in the iron. The removal of aqueous species (i.e., NO3â, Ca, and carbonate alkalinity) indicates that mineral precipitation contributed more significantly to porosity loss than did the trapped gases. Using the stoichiometric reactions between Fe0 and NO3â, an average corrosion rate of 1.7 mmol kgâ 1 dâ 1 was derived for the test granular iron. This rate is 10 times greater than Fe0 oxidation by H2O alone, based on H2 gas production. NO3â ion rather than H2O was the major oxidant in the groundwater in the absence of molecular O2. The N-mass balance [e.g., N2(g) and NH4+ and NO3â] suggests that abiotic reduction of NO3â dominated at the start of Fe0 treatment, whereas N2 production became more important once the microbial activity began. These laboratory results closely predict N2 gas production in a separated large column experiment that was operated for â¼2 yr in the field, where a maximum of â¼600 ml dâ 1 gas volumes was detected, of which 99.5% (v/v) was N2. We conclude that NO3â suppressed the production of H2(g) by competing with water for Fe0 oxidation, especially at the beginning of water treatment when Fe0 is highly reactive. Depends on the groundwater composition, gas venting may be necessary in maintaining PRB performance in the field.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Contaminant Hydrology - Volume 82, Issues 3â4, 10 January 2006, Pages 338-356
Journal: Journal of Contaminant Hydrology - Volume 82, Issues 3â4, 10 January 2006, Pages 338-356
نویسندگان
W. Kamolpornwijit, L. Liang,