مطالعه انتقال و کارایی نانوذرات آهن صفر ظرفیتی پایدار شده در حذف کروم در ستون شن

نوع مقاله : مقالات پژوهشی

نویسندگان

• محمدتقی کوهیان افضل
• احمد فرخیان فیروزی
• مهدی تقوی

شهید چمران اهواز

https://doi.org/10.22067/jsw.v33i1.75059

چکیده

نانوذرات آهن صفر ظرفیتی طی سال­های اخیر به دلیل دارا بودن خواص منحصر و قابلیت بالا در حذف آلاینده­های مختلف مانند یون کروم شش ظرفیتی از محیط­های شنی و آب مورد استفاده قرار گرفته­اند. در این مطالعه از روش احیای شیمیایی سولفات آهن توسط بوروهیدرید­سدیم برای سنتز نانوذرات آهن صفر ظرفیتی استفاده گردید. خصوصیات نانوذرات آهن صفر ظرفیتی توسط دستگاه­های میکروسکوپ الکترونی روبشی، میکروسکوپ الکترونی عبوری و زتاسایزر تعیین شد. جهت پایدارسازی نانوذرات آهن صفر ظرفیتی از پلیمر سبز، طبیعی و غیرسمی گوارگام و نیز پلیمر زیست تخریب پذیر پلی­اکریل­آمید استفاده شد. میزان پایداری نانوذرات آهن صفر ظرفیتی سنتز شده از طریق محاسبه مقادیر پتانسیل زتا و قطر هیدرودینامیک نانوذرات سنتز شده توسط دستگاه زتا‌سایزر تعیین گردید. به منظور مقایسه تأثیر تیمارهای مختلف بر انتقال نانوذرات آهن صفر ظرفیتی و احیای کروم شش ظرفیتی در ستون‌های شن از آزمایش‌های فاکتوریل جداگانه 3*3 در قالب طرح کاملاً تصادفی با دو فاکتور و سه تکرار استفاده گردیده و مقایسات میانگین از طریق آزمون دانکن در سطح احتمال 5 درصد انجام شد. شبیه­سازی انتقال نانوذرات آهن صفر ظرفیتی توسط نرم­افزار هیدروس یک بعدی و مدل سینتیک جذب- واجذب تک مکانی در ستون­های شن انجام گردید. نتایج نشان داد که با افزایش غلظت اولیه کروم و غلظت نانوذرات، درصد احیای کروم شش ظرفیتی به ترتیب کاهش و افزلیش یافت. همچنین با افزایش قدرت یونی و غلظت نانوذرات، انتقال آنها در ستون­های شن کاهش یافت. نتایج حاکی از آن بود که نانوذرات آهن صفر ظرفیتی با پوشش پلی‌اکریل‌آمید، گوارگام و بدون پوشش به ترتیب دارای بیشترین کارایی در احیای یون کروم از محیط متخلخل بودند. نتایج حاصل از منحنی­های رخنه انتقال نانوذرات آهن صفر ظرفیتی سنتز شده نشان داد که با افزایش مقادیر غلظت نانوذرات (1، 2 و 3 گرم در لیتر) و قدرت یونی (1، 10 و 100 میلی­مولار)، مقادیر غلظت نسبی (C/C0) نانوذرات آهن صفر ظرفیتی سنتز شده کاهش یافته و بیشترین درصد انتقال نانوذرات سنتز شده به ترتیب در غلظت نانوذرات برابر 1 گرم در لیتر و قدرت یونی 1 میلی­مولار کلرید رخ داد. همچنین نانوذرات آهن صفر ظرفیتی با پوشش­های پلی‌اکریل‌آمید، گوارگام و بدون پوشش به ترتیب بیشترین تا کمترین مقادیر غلظت نسبی و انتقال نانوذرات را به خود اختصاص دادند.

کلیدواژه‌ها

• نانوذرات آهن صفر ظرفیتی
• کروم
• انتقال
• احیاء

20.1001.1.20084757.1398.33.1.11.2

عنوان مقاله [English]

Transport Study and Efficiency of Stabilized Nanoscale Zerovalent Iron Particles for Hexavalent Chromium Removal from Sand Column

نویسندگان [English]

• Mohammad Taghi Kouhiyan Afzal
• Ahmad Farrokhian Firouzi
• Mehdi Taghavi

Shahid Chamran University of Ahvaz

چکیده [English]

Introduction: Nowadays pollution of sand columns and water resources with hexavalent chromium is enhancing due to the increase of industrial and agricultural activities. In recent years nanoscale zerovalent iron particles (nZVIP) have been used according to special properties comprising of high surface area, high reaction sites, non-toxic, non-expensive and high potential for removal of pollutants such as hexavalent chromium from sand columns and water. The size range of Zerovalent iron nanoparticles is less than 100 nm. So they could potentially be transported into the subsurface and finally be mixed with the target pollutants. Chromium is one of the steely-grey, lustrous and toxic heavy metals with high toxicity potential. Upon chromium (VI) toxicity this element is classified as a primary contaminant. Chromium (III) compounds is not toxic and hazardous and are grouped as one of the beneficial elements for human and other animals, while the toxicity and carcinogenic properties of hexavalent chromium have been realized for a long time in all over the world. Application of polymers as nZVIP stabilizers diminishes flocculation and sedimentation of nanoparticles. So usage of such polymers may lead to decreasing of particle size, enhancing reactivity and increasing particle transport in column and continuous medium studies. The objectives of this study were: (1) synthesis and characterization of different surface modified nZVIP with some polymers including Polyacrylamide (PAM) and Guar gum (GG), (2) the removal of hexavalent chromium ions from sand columns by application of different stabilized nZVIP, (3) investigation the impacts of different experimental situations on hexavalent chromium removal from sand columns including primary nZVIP dosages and primary hexavalent chromium dosages, and (4) evaluation nZVIP transportation in sand columns.
Material and Methods: In this research, nZVIP were synthesized using chemical reduction of ferrous sulfate by sodium borohydride. Guar gum (GG) as a green and environmentally friendly coating and polyacrylamide (PAM) as an anionic and biodegradable polymer were applied for stabilizing of nanoparticles. Zeta potential values were determined by a ZetaPlus zeta-potential analyzer from Brookhaven Instruments Corporation and the measured values were gathered from a suspension containing 5 mg zero valent iron nanoparticles in 100 mL of 1 mM NaCl solution, at room temperature. The hydrodynamic diameter of nanoparticles was determined using a ZetaPlus zeta potential analyzer and the Brownian movement of particles was related to nanoscale zerovalent iron particles hydrodynamic diameter. The morphology of zerovalent iron nanoparticles was determined by scanning electron microscope (SEM). Furthermore, the size of the synthesized nanoparticles was considered using a transmission electron microscope (TEM) via image measuring software.
 Results and Discussions: The results showed by increasing of nanoparticle and hexavalent chromium dosage the removal efficiency of chromium increased and decreased from sand columns, respectively. Increasing of hexavalent chromium dosage from 40 to 80 mg/L in sand columns lead to more excessive chromium ions at sand columns and diminishing of hexavalent chromium removal efficient from sand particles. When the dosage of nanoscale zerovalent iron particles raised from 1 to 3 g/L and while the concentration of Cr (VI) was on a constant value of 100 mg/L, the effective reaction sites for hexavalent chromium removal would increase and so the removal performance would enhance according to the nanoparticle dosages. The findings of the current study also revealed when ionic strength and nZVIP dosage enhanced, the transportation of nZVIP decreased in sand columns. By enhancing the concentration of nZVIP, the surface reaction sites of nZVIP increased and hence the efficiency of chromium removal raised from sand columns.
 Zeta potential is a good parameter for evaluating the colloidal stability. This parameter is an index of stability that reflects the electrostatic repulsion forces between charged particles. By shifting the zeta potential values to the higher records (more negative) the magnitude of repulsion forces among the particles will increase and the stability of them will enhance as a result. In this research the achieved zeta potential records for synthesized nZVIP showed that PAM-stabilized nZVIP and non-stabilized nZVIP had the most and the least stability values respectively.
Conclusion: The final results of this study revealed that increasing dosages of synthesized zerovalent iron nanoparticles enhanced the removal efficiency of nitrate and hexavalent chromium from sand columns. When dosages of Cr (VI) increased the removal efficiency of current pollutants decreased. TEM results showed the order of particle sizes were upon to the following trend: PAM-nZVIP < GG- nZVIP < Bare- nZVIP. So PAM stabilized zerovalent iron nanoparticles and the bare nanoparticles were the smallest and largest sizes of all. The efficiency of hexavalent chromium removal and nanoparticle transormation were according to the following trend:  polyacrylamide (PAM)- nZVIP> Guar gum (GG)- nZVIP> Bare- nZVIP

کلیدواژه‌ها [English]

• nanoscale zerovalent iron particles
• Chromium
• Transportation
• removal

مراجع

1. Arildii D., Davaasambuu S., and Batchuluun S. 2018. Equilibrium and kinetic study on hexavalent chromium sorption on bentonite supported zerovalent iron. Journal of Chemical Technology and Metallurgy 53(2): 218- 231.

2. Duan R., Dong Y., and Zhang Q. 2018. Characteristics of aggregate size distribution of nanoscale zero-valent iron in aqueous suspensions and Its effect on transport process in porous media. Water 10(6): 1-14.

3. Fan G., Cang L., Qin W., Zhou C., Gomes H., and Zhou D. 2013. Surfactants-enhanced electrokinetic transport of xanthan gum stabilized nanoPd/Fe for the remediation of PCBs contaminated soils. Separation and Purification Technology 114: 64-72.

4. Jiao C., Cheng Y., Fan W., and Li J. 2015. Synthesis of agar-stabilized nanoscale zero-valent iron particles and removal study of hexavalent chromium, International Journal of Environmental Science and Technology 12: 1603–1612.

5. Jiemvarangkul P., Zhang W.X, and Lien H.L. 2011. Enhanced transport of polyelectrolyte stabilized nanoscale zero-valent iron (nZVI) in porous media. Chemical Engineering Journal 170: 482–491.

6. Koohiyan Afzal M.T., Farrokhian Firouzi A., and Taghavi M. 2017. Synthesis of bare and four different polymer- stabilized zero-valent iron nanoparticles and their efficiency on hexavalent chromium removal from aqueous solutions, Journal of Water and Environmental Nanotechnology 2(4): 278-289.

7. Phenrat T., Saleh N., Sirk K., Kim H-J., Tilton R.D., and Lowry G.V. 2007. Stabilization of aqueous zerovalent iron dispersions by anionic polyelectrolytes: adsorbed anionic polyelectrolyte layer properties and their effect on aggregation and sedimentation. Nanoparticle Research 10: 795-814.

8. Prema P., and Selvarani M. 2012. Use of zerovalent iron nanoparticles as low cost adsorbent in the removal of hexavalent chromium from aqueous solution: equilibrium and kinetics study, International Journal of Research in Chemistry and Environment 2(4): 115- 124.

9. Ramazanpour Esfahani A., and Farrokhian Firouzi A. 2016. Synthesis and application of stabilized zero-valent iron nanoparticles for hexavalent chromium removal in saturated sand columns: experimental and modeling studies, Desalination and Water Treatment 57(33): 1-11.

10. Ramazanpour Esfahani A., Hojati S., Azimi A., Alidokht L., Farzadian M., and Khataee A. 2015. Reductive removal of hexavalent chromium from aqueous solution using sepiolite-stabilized zero-valent iron nanoparticles: process optimization and kinetic study, Korean Journal of Chemical Engineering 31: 630–638.

11. Raychoudhury T., Tufenkji N., and Ghoshal S. 2012. Aggregation and deposition kinetics of carboxymethyl cellulose-modified zero-valent iron nanoparticles in porous media, Water Research 46: 1735-1744.

12. Siciliano A. 2016. Removal of Cr(VI) from water using a new reactive material: magnesium oxide supported nanoscale zero-valent iron., Journal of Materials 9(666): 2-19.

13. Singh R., Misra V., and Singh R.P. 2011. Synthesis, characterization and role of zero-valent iron nanoparticle in removal of hexavalent chromium from chromium-spiked soil. Journal of Nanoparticle Research 13: 4063–4073.

14. Singh R., and Misra V. 2015. Stabilization of zero-valent iron nanoparticles: role of polymers and surfactants. In Aliofkhazraei M. (eds) Handbook of Nanoparticles. Springer International Publishing Switzerland.

15. Tiraferri A., and Sethi R. 2008. Enhanced transport of zerovalent iron nanoparticles in saturated porous media by guar gum. Journal of Nanoparticle Research 11(3): 635-645.

16. Xue D., and Sethi R. 2012. Viscoelastic gels of guar and xanthan gum mixtures provide long-term stabilization of iron micro- and nanoparticles. Nanoparticle Research 14: 1239.

17. Yang Z., Qiu X., Fang Z., and Pokeung T. 2015. Transport of nano zero-valent iron supported by mesoporous silica microspheres in porous media. Water Science and Technology 71(12): 1800-1805.