جذب سطحی رقابتی آرسنات و فسفات روی کلسایت

نوع مقاله : مقاله پژوهشی

نویسندگان

1 گروه خاکشناسی، دانشکده کشاورزی، دانشگاه تربیت مدرس، تهران، ایران

2 گروه علوم و مهندسی خاک، دانشکده کشاورزی و منابع طبیعی، دانشگاه محقق اردبیلی، اردبیل، ایران

3 گروه علوم و مهندسی خاک، دانشکده کشاورزی، دانشگاه شهید باهنر کرمان، کرمان، ایران

چکیده

کلسایت، پایدارترین شکل کربنات کلسیم در خاک، یکی از اجزای مهم فاز جامد خاک­های مناطق خشک و نیمه‌خشک است. این کانی بر رفتار شیمیایی یون­ها از جمله اکسی آنیون­ها و فلزات انتقالی در خاک اثرات مهمی دارد. آرسنات و فسفات از اکسی آنیون­های مهم در سیستم­های طبیعی نظیر خاک هستند و به دلیل تشابه یونی، معمولاً برای بار سطحی ذرات کلوییدی خاک از طریق واکنش‌های جذب سطحی و رهاسازی به شدت با هم رقابت می‌کنند. با توجه به اهمیت این واکنش در کنترل غلظت تعادلی آرسنات و فسفات در خاک، در این تحقیق جذب سطحی آرسنات روی کانی کلسایت در غلظت‌های مختلف آرسنات و در قدرت­­های یونی مختلف و در رقابت با فسفات بررسی و با مدلی شیمیایی توصیف شد. همچنین رفتار باری کلسایت به روش تیترسنجی اسید و باز در قدرت­های یونی مختلف اندازه­گیری گردید. بر اساس داده­های تیتراسیون، نقطه صفر بار الکتریکی کانی در pH2/8 تعیین شد. همدما­های جذب سطحی آرسنات نشان داد که جذب سطحی آرسنات متأثر از قدرت یونی و غلظت اولیه آن است. در قدرت­های یونی کم، جذب سطحی آرسنات حداکثر بود و با افزایش قدرت یونی از مقدار آن کاسته شد. جذب سطحی آرسنات با افزایش غلظت فسفات کاهش یافت اما آرسنات تأثیری بر جذب سطحی فسفات نداشت که نشان می‌دهد فسفات قوی‌تر از آرسنات جذب سطحی کلسایت می‌شود. داده­های آزمایشی با مدل شیمیایی CD-MUSIC توصیف و پیش‌بینی گردیدند. مدل داده­ها را با در نظر گرفتن دو کمپلکس درون کره­ای سطحی ≡Ca2O2AsO2 و  ≡Ca2O2PO2  با دقت بالا (R2=0.998) توصیف کرد. به‌طور کلی نتایج آزمایشی و ضرایب مدل نشان داد که برهم‌کنش بسیار قوی‌تر فسفات با کلسایت موجب افزایش زیست‌فراهمی آرسنات و تحرک آن در خاک‌های آهکی می‌شود.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

Competitive Adsorption of Arsenate and Phosphate on Calcite

نویسندگان [English]

  • Mojtaba Moghbeli 1
  • Rasoul Rahnemaie 1
  • Esmaiel Goli Kalanpa 2
  • Naser Broomand 3
1 Department of Soil Science,, Faculty of Agriculture, Tarbiat Modares University, Tehran, Iran
2 Department of Soil Engineering, Faculty of Agriculture and Natural resources, , University of Mohaghegh Ardabili,, Ardabil, Iran
3 Department of Soil Science Enginering, Faculty of Agriculture, Shahid Bahonar University, Kerman, Iran
چکیده [English]

Calcite, the most stable calcium carbonate in soil, is a major part of soil solid phase in arid and semiarid regions. This mineral significantly affects the chemical behavior of ions including oxyanions and transition metal ions in the soil. Arsenate and phosphate are two important oxyanions in natural systems like soil and because of similar ionic properties strongly compete for the colloids surface charge via adsorption and desorption reactions. Because of the importance of this reaction in controlling the equilibrium concentrations of arsenate and phosphate in soil, in this research, arsenate adsorption on calcite was measured and modeled as a function of arsenate concentration and ionic strength and also in competition with phosphate. In addition, charging behavior of calcite was measured by acid-base titration at various ionic strength. Based on the titration data, calcite point of zero charge (PZC) was obtained at pH=8.2. Adsorption isotherms showed that arsenate adsorption is affected by the ionic strength and the initial concentration of arsenate. Adsorption of arsenate was high at low ionic strength and was decreased with increasing the ionic strength. Arsenate adsorption was also decreased with increasing phosphate concentration, but arsenate had no effect on phosphate adsorption indicating phosphate is adsorbed stronger than arsenate on calcite. The experimental data were successfully (R2=0.998) described with a single set of parameters by CD-MUSIC model, considering two inner sphere surface complexes ≡Ca2O2AsO2 and ≡Ca2O2PO2. Overall, the experimental data and model parameters implied that the stronger interaction of phosphate with calcite increases bioavailability and mobility of arsenate in calcareous soils.

کلیدواژه‌ها [English]

  • Adsorption
  • Arsenate
  • Calcite
  • CD-MUSIC model
  • Phosphate

مراجع

Adam, N. (2017). A Wet-Chemical and Phosphorus K-edge X-ray Absorption Near Edge Structure Investigation of Phosphate Adsorption on Binary Mixtures of Ferrihydrite and Calcite: Implications for Phosphorus Bioavailability. Soil Science Society of America Journal 81:1079-1087.
Alexandratos, V.G., Elzinga, E.J. and Reeder, R.J. (2007). Arsenate uptake by calcite: macroscopic and spectroscopic characterization of adsorption and incorporation mechanisms. Geochimica et Cosmochimica Acta 71:4172-4187.
Antelo, J., Avena, M., Fiol S., López, R. and Arce, F. (2005). Effects of pH and ionic strength on the adsorption of phosphate and arsenate at the goethite–water interface. Journal of colloid and interface science 285:476-486.
Arai, Y. and Sparks, D.L. (2001). ATR–FTIR spectroscopic investigation on phosphate adsorption mechanisms at the ferrihydrite–water interface. Journal of colloid and interface science 241:317-326.
Celi, L., Barberis, E. and Marsan, F.A. (2000). Sorption of phosphate on goethite at high concentrations. Soil science 165:657-664.
Eriksson, R., Merta, J.v and Rosenholm, J.B. (2007). The calcite/water interface: I. Surface charge in indifferent electrolyte media and the influence of low-molecular-weight polyelectrolyte. Journal of colloid and interface science 313:184-193.
Eriksson, R., Merta, J. and Rosenholm ,J.B. (2008). The calcite/water interface II. Effect of added lattice ions on the charge properties and adsorption of sodium polyacrylate. Journal of colloid and interface science 326:396-402.
Goldberg, S. (2002). Competitive adsorption of arsenate and arsenite on oxides and clay minerals. Soil Science Society of America Journal 66:413-421.
Goldberg, S. and Johnston, C.T. (2001). Mechanisms of arsenic adsorption on amorphous oxides evaluated using macroscopic measurements, vibrational spectroscopy, and surface complexation modeling.
Griffin, R.A. and Shimp, N.F. (1978). Attenuation of pollutants in municipal landfill leachate by clay minerals Environmental Protection Agency, Office of Research and Development. 
Hiemstra, T. van Riemsdijk, W.H. (1996). A surface structural approach to ion adsorption: The charge distribution (CD) model. Journal of Colloid and Interface Science, 179(2): 488-508.
Kanematsu, M., Young, T.M., Fukushi, K., Green, P.G. and Darby, J.L. (2013). Arsenic (III, V) adsorption on a goethite-based adsorbent in the presence of major co-existing ions: modeling competitive adsorption consistent with spectroscopic and molecular evidence. Geochimica et Cosmochimica Acta 106:404-428.
Kosmulski, M. (2001). Chemical properties of material surfaces CRC press.
Kwon, K.D. and Kubicki J.D. (2004). Molecular orbital theory study on surface complex structures of phosphates to iron hydroxides: Calculation of vibrational frequencies and adsorption energies. Langmuir 20:9249-9254.
Li, Z., Sun X., Huang L., Liu D., Yu L., Wu H. and Wei D. (2017). Phosphate adsorption and precipitation on calcite under calco-carbonic equilibrium condition. Chemosphere, 183: 419-428.
Lin, H.-T., Wang, M. and Li G.-C. (2002). Effect of water extract of compost on the adsorption of arsenate by two calcareous soils. Water, Air, and Soil Pollution 138:359-374.
Lin, H.-T., Wang, M. and Li G.-C. (2004). Complexation of arsenate with humic substance in water extract of compost. Chemosphere 56:1105-1112.
Lin, H.T., Wang, M. and Seshaiah, K. (2008). Mobility of adsorbed arsenic in two calcareous soils as influenced by water extract of compost. Chemosphere 71:742-749.
Manning, B.A. and Goldberg, S. (1996). Modeling arsenate competitive adsorption on kaolinite, montmorillonite and illite. Clays and clay minerals 44:609-623.
Masue-Slowey, Y., Loeppert, R.H. and Fendorf, S. (2011). Alteration of ferrihydrite reductive dissolution and transformation by adsorbed As and structural Al: Implications for As retention. Geochimica et Cosmochimica Acta 75:870-886.
Millero, F., Huang, F., Zhu, X., Liu, X. and Zhang, J.-Z. (2001). Adsorption and desorption of phosphate on calcite and aragonite in seawater. Aquatic Geochemistry, 7(1), 33-56.
Mohapatra, D., Mishra, D., Chaudhury, G.R. and Das, R.P. (2007). Arsenic adsorption mechanism on clay minerals and its dependence on temperature. Korean Journal of Chemical Engineering 24:426-430.
Nelson, H., Sjöberg, S. and Lövgren, L. (2013). Surface complexation modelling of arsenate and copper adsorbed at the goethite/water interface. Applied geochemistry 35:64-74.
Rahnemaie, R., Hiemstra, T. and van Riemsdijk, W.H. (2006). A new surface structural approach to ion adsorption: Tracing the location of electrolyte ions. Journal of colloid and interface science 293:312-321.
Rahnemaie, R., Hiemstra, T. and van Riemsdijk, W.H. (2007). Geometry, charge distribution, and surface speciation of phosphate on goethite. Langmuir 23:3680-3689.
Sherman, D.M. and Randall, S.R. (2003). Surface complexation of arsenic (V) to iron (III)(hydr) oxides: structural mechanism from ab initio molecular geometries and EXAFS spectroscopy. Geochimica et Cosmochimica Acta 67:4223-4230.
Smith, E., Naidu, R. and Alston, A. (2002) Chemistry of inorganic arsenic in soils. Journal of Environmental Quality 31:557-563.
Sø, H.U., Postma, D., Jakobsen, R. and Larsen, F. (2008). Sorption and desorption of arsenate and arsenite on calcite. Geochimica et Cosmochimica Acta 72:5871-5884.
Sø, H. U., Postma, D., Jakobsen, R. and Larsen, F. (2011). Sorption of phosphate onto calcite; results from batch experiments and surface complexation modeling. Geochimica et Cosmochimica Acta, 75(10), 2911-2923.
Sø, H.U., Postma, D., Jakobsen, R. and Larsen, F. (2012). Competitive adsorption of arsenate and phosphate onto calcite; experimental results and modeling with CCM and CD-MUSIC. Geochimica et Cosmochimica Acta 93:1-13.
Song, S., Lopez-Valdivieso, A., Hernandez-Campos, D., Peng C., Monroy-Fernandez, M. and Razo-Soto, I. (2006). Arsenic removal from high-arsenic water by enhanced coagulation with ferric ions and coarse calcite. Water research 40:364-372.
Wolthers, M., Charlet, L. and Van Cappellen, P. (2008). The surface chemistry of divalent metal carbonate minerals; a critical assessment of surface charge and potential data using the charge distribution multi-site ion complexation model. American Journal of science 308:905-941.
Yokoyama, Y., Tanaka, K. and Takahashi, Y. (2012). Differences in the immobilization of arsenite and arsenate by calcite. Geochimica et Cosmochimica Acta 91:202-219.
تحقیقات آب و خاک ایران
دوره 51، شماره 9
آذر 1399
صفحه 2247-2257

فایل ها

هم رسانی

ارجاع به این مقاله

آمار