تاثیر شدت بخشی با هیدروکسید سدیم بر جامدسازی بنتونیت آلوده

اوحدی, وحید رضا; دیرانلو, مرتضی

تاثیر شدت بخشی با هیدروکسید سدیم بر جامدسازی بنتونیت آلوده

نوع مقاله : مقاله پژوهشی

نویسندگان

¹ گروه عمران، دانشکده مهندسی، دانشگاه بوعلی سینا، عضو هیئت علمی وابسته دانشکده عمران، پردیس دانشکده های فنی، دانشگاه تهران

² گروه عمران، دانشکده مهندسی، مجتمع آموزش عالی اسفراین

چکیده

تثبیت/جامدسازی پایه سیمانی روشی متداول برای نگهداری فلزات سنگین در خاک‌های آلوده است. تأثیر یون فلزی در تأخیر هیدراتاسیون سیمان، کارایی این روش را با چالش مواجه کرده‌است. استفاده از NaOH باعث رسوب بخشی از آلاینده فلز سنگین شده و از تأثیر منفی یون فلزی بر گیرش سیمان کاسته می‌شود. این فرایند شدت‌بخشی نامیده می‌شود. هدف این تحقیق تعیین تأثیر شدت‌بخشی بر جامدسازی خاک آلوده در شرایط pH ‌های قلیائی و اسیدی شدید است.
نمونه‌های بنتونیت آلوده به سرب، در دو حالت شدت‌بخشی شده با NaOH و بدون شدت‌بخشی، با استفاده از سیمان به میزان 10 الی 50% درصد وزنی خاک، جامدسازی شده‌اند. شرایط قلیایی و اسیدی شدید با آزمایش‌های تعادل آبشویی و آبشویی پیشرونده در نمونه‌های جامدسازی شده شبیه‌سازی شده‌است. نتایج نشان داده‌است که در شرایط اسیدی و قلیائی شدید، شدت‌بخشی با NaOH، موجب کاهش مقادیر Pb آبشویی شده از نمونه‌ها شده‌است. در شرایط قلیائی شدید با شدت‌بخشی بنتونیت آلوده در نمونه‌های S/S شده، آبشویی یون Pb تا 96% کاهش یافته است. از سوی دیگر، در نمونه‌های آلوده به غلظت‌های زیاد سرب، شدت‌بخشی با NaOH سبب افزایش میزان تشکیل C-S-H شده‌است. با استفاده از راهکار شدت‌بخشی در شرایط قلیائی و اسیدی شدید می‌توان مقادیر سیمان کمتری برای جامدسازی استفاده کرد.

کلیدواژه‌ها

موضوعات

زمین شناسی مهندسی محیط زیست

عنوان مقاله [English]

Impact of Enhancement by NaOH on Solidification/Stabilization of Contaminated Bentonite

نویسندگان [English]

Vahid Reza Ouhadi ¹
Morteza Deiranlou ²

¹ Civil Eng. Department,, Faculty of Eng., Bu Ali Sina University, and Adjunct Prof., School of Civil Eng., University of Tehran.

² Civil Eng. Department, Faculty of Eng., Esfarayen University

چکیده [English]

Cement-based solidification/stabilization is one of the common methods for increasing the stability of heavy metals in contaminated soils. However, the presence of some of the heavy metals such as lead ions causes a delay and prevention in cement hydration which makes this method as an inapplicable. Enhancement of contaminated clayey soils by NaOH can remove the problems associated with cement hydration delay in presence of heavy metal ions. The main objective of this paper is to determine the impact of enhancement on solidification/stabilization of contaminated soils in extreme acidic and alkaline environment. To achieve the above mentioned objective, samples of contaminated bentonite by 50 and 100 cmol/kg-soil of lead nitrate at two different conditions of enhancement by NaOH and without enhancement were solidified/stabilized by 10 and 50 percentages of cement. The extreme acidic and alkaline conditions simulated by performing of equilibrium soil washing, endorsed TCLP test in solidified/stabilized cured samples. In addition, series of XRD experiments were performed to address the rate and quantity of CSH formation. The achieved results indicate that at extreme alkaline conditions the enhancement of contaminated bentonite has decreased the leach-ability of lead ions around 96%. With a decrease in pH of samples to the quantities less than 5, the use of enhanced samples has reduced the quantity of leachate in enhanced samples in comparison to unenhanced samples around 90%. This is attributed to the contaminant retention by clay fraction of bentonite and contaminant solidification by CSH gels.

کلیدواژه‌ها [English]

Cement
Solidification/Stabilization
Enhancement
Bentonite
Heavy Metal Contaminant

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