هم‌دماهای جذب سطحی و رهاسازی بور روی کلسایت: اثر قدرت یونی و pH محلول

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشجوی سابق دکتری دانشکدة کشاورزی دانشگاه تربیت مدرس

2 استادیار دانشکدة کشاورزی دانشگاه تربیت مدرس

3 استاد دانشکدة کشاورزی دانشگاه تربیت مدرس

چکیده

به‌ منظور تبیین نقش کلسایت در رفتار شیمیایی بور در خاک‌های آهکی، جذب ‌سطحی و رهاسازی بور روی کلسایت در چهار نسبت فاز جامد به محلول، در سه سطح قدرت‌ یونی و در محدودة pH 5/7 تا 5/11 بررسی شد. داده‌های آزمایشی نشان داد جذب سطحی بور با افزایش نسبت فاز جامد به محلول و با افزایش غلظت تعادلی بور افزایش می‌یابد. همچنین افزایش قدرت‌ یونی موجب افزایش جذب‌ سطحی بور شد که احتمالاً ناشی از مکانیزم جذب‌ سطحی درون‌کره‌ای بور و کاهش ضخامت لایة دوگانة الکتریکی است. جذب ‌سطحی بور با افزایش pH افزایش یافت و در pH 2/9 به حداکثر رسید. افزایش مجدد pH موجب کاهش جذب‌ سطحی شد. چهار مرحلة متوالی عصاره‌گیری با محلول زمینة نیترات کلسیم موجب رهاسازی حدود 20 تا 40 درصد از بور جذب‌سطحی‌شده شد. به طور کلی، نتایج نشان داد اگرچه کلسایت کانی غالب خاک‌های آهکی است، نقش ضعیفی در کنترل غلظت بور در فاز محلول دارد.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

Isotherms of Adsorption on and Desorption from Calcite of Boron: pH and Salt Dependency

نویسندگان [English]

  • AZIZ MAJIDI 1
  • RASOUL RAHNEMAIE 2
  • MOHAMMAD JAFAR MALAKOUTI 3
1 Former Ph.D. student, Faculty of Agriculture, Department of Soil Science, Tarbiat Modares University
2 assistant professor, Faculty of Agriculture, Department of Soil Science, Tarbiat Modares University
3 professor, Faculty of Agriculture, Department of Soil Science, Tarbiat Modares University
چکیده [English]

The role of calcite as related to the chemical behavior of boron (B) in calcareous soils was investigated through an assessment of B adsorption and desorption reactions on and from calcite in four ratios of solid to solution rate, three levels of ionic strength, and within a pH range of 7.5 to 11.5. Experimental data indicated that B adsorption is increased by an increase in the solid to solution ratio and by increase in its equilibrium concentration. Further, an increase in ionic strength strongly stimulated B adsorption, which is likely due to the formation of boron inner-sphere surface complexes and as well shrinkage in the electrical double layer thicknesses. Boron adsorption increased by increase in pH getting maximized at about 9.2. Any further increase in pH reduced B adsorption. After four successive desorption stages with calcium nitrate as background solution, approximately 20-40% of the initially adsorbed B was released. In general, it could be concluded that even though calcite is the major mineral in calcareous soils, however, boron-calcite adsorption interactions influence B concentration in the soil solution as by weakly.

کلیدواژه‌ها [English]

  • Calcareous soil
  • Double layer
  • Soil solution
  • Chemical behavior

مراجع

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