نوع مقاله : مقاله پژوهشی

نویسندگان

پژوهشکده‌ی مواد و سوخت هسته‌ای، پژوهشگاه علوم و فنون هسته‌ای، سازمان انرژی اتمی ایران، صندوق پستی: 8486-11365، تهران ـ ایران

چکیده

کاهش و رسوب­گذاری اورانیم با استفاده از باکتری­های بی­هوازی، یکی از راهکارهای مؤثری است که در دو دهه­ی گذشته با هدف کاهش انتشار اورانیم در محیط، مورد توجه بسیاری از پژوهش­گران قرار گرفته است. در این پژوهش، قابلیت یک باکتری بی­هوازی اختیاری با نام شیوانلا اس پی 8GCWx در کاهش و حذف اورانیم از محلول­های آبی مورد بررسی قرار گرفته است. برای این منظور، محلول اورانیل استات در حضور سدیم لاکتات به عنوان الکترون­دهنده، با باکتری 8­GCWx در شرایط بی­هوازی در تماس قرار داده شد. نتیجه­ی این واکنش، حذف اورانیم از محلول و تشکیل یک رسوب قهوه­ای رنگ حاوی باکتری و اورانیم بود. تجزیه­ی رسوب با استفاده از طیف دیدگانی- فرابنفش و دستگاه پتانسیواستات/ گالوانواستات (شرکت اتولب هلند) نشان داد که بیش­تر اورانیم موجود در رسوب به شکل کاهیده­ی U(IV) است. بنابراین سازوکار حذف اورانیم از محلول توسط این باکتری در شرایط بی­هوازی، سازوکار کاهش است. بهترین pH برای حذف اورانیم توسط 8GCWx برابر با 6.8 و حداکثر درصد حذف اورانیم از محلول در چگالی سلولی-1 mL 109 برابر با %90 به­دست آمد. تغییرات غلظت اورانیم در محلول نسبت به زمان در روز اول با سینتیک واکنش درجه­ی اول تطابق مناسبی داشت. بر همین مبنا، ثابت سرعت واکنش کاهش میکروبی اورانیم توسط سویه­ی 8GCWx برابر با 0.06 hr-1 محاسبه شد. در نتیجه، سویه­ی شیوانلا اس پی 8GCWx به عنوان یک باکتری توانمند در کاهش میکروبی اورانیم تعیین شد.

کلیدواژه‌ها

عنوان مقاله [English]

Microbial reduction and precipitation of uranium using anaerobic bacteria Shewanella sp GCWx8

نویسندگان [English]

  • A Zaheri
  • A Keshtkar
  • F Fatemi

چکیده [English]

The microbial reduction and precipitation of uranium using anaerobic bacteria are one of the effective methods considered during the last two decades to prevent permeation of the uranium to the environment. In this study, the capability of a facultative anaerobic bacterium, Shewanella spGCWx8, for reduction and removal of the uranium from the aqueous solutions are investigated. Thus, uranyl acetate is introduced into the bacteria anaerobically in the presence of the sodium lactate as an electron donor. This process resulted in the removal of the uranium from the solution and the formation of a precipitate containing uranium and cells. The analysis of the precipitate, using both Auto-lab and UV-vis spectra, confirmed that most of the uranium in the precipitate was in the from of reduced uranium, U(IV). Therefore, the mechanism of uranium removal by the strain GCWx8 in the aerobic condition is a reduction process. The best pH for a uranium removal by the GCWx8 was obtained 6.8, and the maximum removal percent at the cell density of 109 (cells per milliliter) has gained 90%. The first order of the reaction rate was satisfactory for bioreduction at the first day of the incubation. Based on the first order of the reaction rate assumption for the uranium bioreduction, the reaction rate constant was obtained 0.06 hr-1. As a result, strain Shewanella spGCWx8 was found as an able bacterium for the uranium bioreduction.

کلیدواژه‌ها [English]

  • Reduction
  • Precipitation
  • Uranium
  • Anaerobic bacteria Shewanella sp GCWx8
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