تثبیت و جامدسازی بنتونیت آلوده به کادمیوم با استفاده از سیمان و تأثیر نانو سیلیس بر این فرآیند

نوع مقاله : پژوهشی اصیل (کامل)

نویسندگان
وحید رضا اوحدی 1
نسیم صحرایی 2
1 عضو هیئت علمی دانشکده مهندسی دانشگاه بوعلی سینا و عضو هیئت علمی وابسته دانشکده عمران دانشگاه تهران
2 دانشکده مهندسی دانشگاه بوعلی سینا
DOI: 10.22034/22.3.133
چکیده
در سال­های اخیر استفاده از نانو مواد در پروژه‌های مختلف علوم و مهندسی مورد توجه قرار گرفته است. در این راستا، مطالعه تأثیر نانو مواد در ترکیب با دیگر مصالح از زمینه­های نوین در علوم مهندسی ژئوتکنیک و ژئوتکنیک زیست‌محیطی است. این تحقیق به منظور تعیین مکانیزم نگهداشت آلاینده فلز سنگین کادمیوم در فرآیند تثبیت و جامدسازی پایه سیمانی بنتونیت آلوده درحضور نانو سیلیس انجام شده است. مکانیزم نگهداری آلاینده با بررسی نتایج آزمایش­های تعیین رفتار کادمیوم و نانو سیلیس با تغییر pH محیط، جذب، آبشویی آلودگی (TCLP) و منحنی­های پراش پرتو ایکس (XRD) تجزیه و تحلیل شده است. نتایج نشان می­دهد که قابلیت جذب و نگهداری فلز سنگین کادمیوم توسط بنتونیت، نسبت به سایر فلزات سنگین، از جمله سرب، مس و روی، کمتر است. با توجه به روند افزایش مقدار کادمیوم آبشویی­شده از آزمایش TCLP در نمونه­های حاوی درصدهای مختلف سیمان، می­توان نتیجه­گیری نمود که معیار 28 روز پیشنهاد شده توسط استاندارد EPA، برای تثبیت و جامدسازی کادمیوم، مناسب و مطمئن نبوده و لازم است این آزمایش را در فاصله زمانی بیشتری انجام داد و سپس نتایج آن مورد استفاده قرار گیرد. همچنین ارزیابی نتایج آزمایش‌های اشعه‌ایکس بیانگر پیشرفت موثرتر واکنش‌های پوزولانی در حضور نانو سیلیس است. میزان کادمیوم آبشویی شده از آزمایش TCLP، با توجه به حضور درصد زیاد سیمان و نانو سیلیس که به تبع دارای میزان قابل­توجهی C-S-H هستند، نشان می­دهد که نقش اصلی در نگهداشت آلاینده فلز سنگین کادمیوم، فرآیند رسوب هیدروکسید و مقدار pH قلیایی محیط به­طور توام با اثر جامدسازی C-S-H است.

کلیدواژه‌ها

موضوعات

عنوان مقاله English

Solidification/stabilization of cadmium contaminated bentonite by the use of cement, impact of nano-silica upon this process

نویسندگان English

Vahid Reza Ouhadi 1
Nasim Sahraie 2
1 Bu-Ali Sina University, Adjunct Prof. of School of Civil Eng., University of Tehran
2 Faculty of Eng., Bu-Ali Sina University
چکیده English

In recent years, the use of nano-materials in different engineering and science projects has increased. The study of the impact of nano-materials in combination with other civil engineering constituents in different geotechnical and geo-environmental engineering projects is very common. This study is aimed to investigate the mechanism of cadmium retention in the process of cement based solidification/stabilization of cadmium contaminated bentonite in the presence of nano-silica. The mechanism of contaminant retention is investigated with the evaluation of cadmium and nano-silica behaviour with change in pH of the environment, adsorption, TCLP results, and evaluation of XRD experimental achievements. The bentonite sample for this research is taken from Iran-Barit Company. To establish the availability of silica ions for interaction with cement and bentonite at different pH, a series of solubility experiments of nano-silica at different pH levels were performed. The results of solubility experiments show that as the pH increases to the alkaline range, the solubility of nano-silica noticeably increases. This fact proves that at the high range of pH due to the use of cement, the required pH conditions for solubility of nano-silica will be provided. Therefore, there will be more possibility for the formation of CSH component. Cadmium nitrate was used to contaminate the bentonite sample for the experimental part. For this purpose, bentonite samples were mixed with 10, 30, and 50 cmol/kg-soil of cadmium nitrate in the electrolyte soil ratio of 20:1. Then, these samples were shaken for two hours in every 24 hours. This process was repeated for 96 hours. After this equilibrium step, the soil suspension was centrifuged. After drying these laboratory contaminated samples, they were solidified/stabilized with different percentages of cement and nano-silica. The results of this paper indicate that the contaminant adsorption and retention of cadmium by bentonite is less than that of adsorption for zinc and lead. The achieved results of TCLP experiments for solidified/stabilized samples with different percentages of cement indicate that the EPA criteria for TCLP experiment which emphasizes for test performance after 28 days, is not suitable for solidification and stabilization of cadmium. In fact, a longer period is necessary to achieve equilibrium and stable results. Furthermore, the results show that due to the low adsorption of cadmium by bentonite and due to the noticeable reduction of pH at the presence of cadmium ions, the required percentages of cement for solidification/stabilization of cadmium contaminated bentonite is much more than the required quantity of cement for other heavy metal contaminated bentonite samples. In addition, the results of XRD experiments show that the pozzolanic interaction process is more efficient in the presence of nano-silica. Furthermore, based on the results of TCLP experiments, the formation of CSH in the presence of nano-silica contributes to the contaminant retention by solidification/stabilization of cement based cadmium contaminated bentonite. Finally, according to the results of this study, in solidified/stabilized samples by mixtures of cement and nano-silica, it is shown that due to the contribution of silica ions in pozzolanic interactions, the solidification is the governing phenomenon for the prevention of heavy metal leachate from solidified/stabilized samples.

کلیدواژه‌ها English

Cadmium
Bentonite
Cement
Nano Silica
Solidification
pH
[1] Xia, W. Y., Feng, Y. S., Du, Y. J., Reddy, K. R., & Wei, M. L. (2018). Solidification and stabilization of heavy metal–contaminated industrial site soil using KMP binder. Journal of Materials in Civil Engineering, 30(6), 04018080.
[2] Rajendran, S., Priya, T.A.K., Khoo, K.S., Hoang, T.K.A., Ng, Munawaroh, H.S.H., Karaman, C., Orooji, Y., Show, P.L., (2022), A critical review on various remediation approaches for heavy metal contaminants removal from contaminated soils, Chemosphere, Vol. 287, Part 4, 132369.
[3] Wang, H., Ju, C., Zhou, M., Chen, J., Dong, Y., Hou, H., (2022). Sustainable and efficient stabilization/solidification of Pb, Cr, and Cd in lead-zinc tailings by using highly reactive pozzolanic solid waste, Journal of Environmental Management, Vol. 306.
[4] USEPA (1997), Innovative site remediation technology: Volume 4, design and application, stabilization/solidification, Center for Environmental Research Information: Risk Reduction Engineering Laboratory, Office of Solid Waste and Emergency Response, US Environmental Protection Agency.
[5] Rupasinghe, M., San Nicolas, R., Mendis, P., Sofi, M., & Ngo, T. (2017). Investigation of strength and hydration characteristics in nano-silica incorporated cement paste. Cement and Concrete Composites, 80, 17-30.
[6] Rupasinghe, M., San Nicolas, R., Mendis, P., & Sofi, M. (2014). Analyzing the pozzolanic reactivity of nano-silica in cement paste.
[7] Said, A. M., Zeidan, M. S., Bassuoni, M. T., & Tian, Y. (2012). Properties of concrete incorporating nano-silica. Construction and Building Materials, 36, 838-844.
[8] García-Taengua, E., Sonebi, M., Hossain, K. M. A., Lachemi, M., & Khatib, J. (2015). Effects of the addition of nanosilica on the rheology, hydration and development of the compressive strength of cement mortars. Composites Part B: Engineering, 81, 120-129.
[9] Mitchell, J. K., & Soga, K. (2005). Fundamentals of soil behavior (Vol. 3). Hoboken, NJ: John Wiley & Sons.
[10] Yong, R. N. (2001). Contaminated soils, pollutant fate and mitigation.
[11] Mitchell, J. K., & Soga, K. (1993). Fundamentals of Soil Behavior, John Wiley & Sons. Inc., New York, 422.
[12] American Society for Testing and Materials, Annual Book of ASTM Standards, Soil and Rock; Building Stones, Vol. 4.08, Philadelphia, PA, (2016).
[13] Wang, L., Tsang, D. C., & Poon, C. S. (2015). Green remediation and recycling of contaminated sediment by waste-incorporated stabilization/ solidification. Chemosphere, 122, 257-264.
[14] Dermatas, D., & Meng, X. (2003). Utilization of fly ash for stabilization/solidification of heavy metal contaminated soils. Engineering Geology, 70(3-4), 377-394.
[15] Keller, W. D. (1963). The origin of high-alumina clay minerals—a review. Clays and Clay minerals, 12(1), 129-151.
[16] Yong, R. N., Galvez-Cloutier, R., & Phadungchewit, Y. (1993). Selective sequential extraction analysis of heavy-metal retention in soil. Canadian Geotechnical Journal, 30(5), 834-847.
[17] Taylor, H. F. (1997). Cement chemistry. Thomas Telford.
[18] Mehta, P. K., & Monteiro, P. J. (2006). Concrete: microstructure, properties, and materials (No. Sirsi) i9780071462891.
[19] Yong, R. N., Nakano, M., & Pusch, R. (2012). Environmental soil properties and behaviour. CRC Press.
[20] Xia, W. Y., Feng, Y. S., Jin, F., Zhang, L. M., & Du, Y. J. (2017). Stabilization and solidification of a heavy metal contaminated site soil using a hydroxyapatite based binder. Construction and Building Materials, 156, 199-207.
[21] Bates, E., & Hills, C. (2015). Stabilization and solidification of contaminated soil and waste: a manual of practice. September 2015.
[22] Bahmani, S. H., Huat, B. B., Asadi, A., & Farzadnia, N. (2014). Stabilization of residual soil using SiO2 nanoparticles and cement. Construction and Building Materials, 64, 350-359.
[23] Chakraborty, S.C., Qamruzzaman, M., Zaman, M.W.U., Alam, M.M., Hossain, M.D., Pramanik, B.K., et al., (2022), Metals in e-waste: Occurrence, fate, impacts and remediation technologies, Process Safety and Environmental Protection, Vol. 162.
[24] Bishop, P. L. (1988). Leaching of inorganic hazardous constituents from stabilized/solidified hazardous wastes. Hazardous Waste and Hazardous Materials, 5(2), 129-143.
[25] Yong, R. N., Warkentin, B. P., Phadungchewit, Y., & Galvez, R. (1990). Buffer capacity and lead retention in some clay materials. Water, Air, and Soil Pollution, 53(1-2), 53-67.
[26] Yong, R. N., & Phadungchewit, Y. (1993). pH influence on selectivity and retention of heavy metals in some clay soils. Canadian Geotechnical Journal, 30(5), 821-833.
[27] Ouhadi, V. R., & Amiri, M. (2011). Geoenvironmental behaviour of nanoclays in interaction with heavy metals contaminant. Amirkabir J, Civil, 42(3), 29-36.
[28] Nehdi, M. L. (2014). Clay in cement-based materials: Critical overview of state-of-the-art. Construction and Building Materials, 51, 372-382.
مهندسی عمران مدرس
دوره 22، شماره 3
خرداد و تیر 1401
صفحه 133-146