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Paper Information

Journal:   ELECTRONIC JOURNAL OF SOIL MANAGEMENT AND SUSTAINABLE PRODUCTION   2016 , Volume 5 , Number 4; Page(s) 161 To 173.
 
Paper: 

BORON ADSORPTION ON BIOTITE: EFFECTS OF PH, IONIC STRENGTH AND NATURE OF BACKGROUND SOLUTION

 
 
Author(s):  ZAREPOUR F., HAMIDPOUR M.*
 
* DEPT. OF SOIL SCIENCE, VALI-E-ASR UNIVERSITY OF RAFSANJAN
 
Abstract: 

Background and Objectives: Boron is one of the essential micronutrients required for plant growth. The concentration of boron in irrigation water or in soil plays an important role in both quality and quantity characteristics of plants. The optimal concentration range for boron is narrower than for other plant essential nutrients. If boron concentration becomes slightly higher than the necessary levels for growth, its toxicity symptoms appear on plant leaves. Knowledge about factors affecting boron adsorption by minerals commonly found in soils of arid and semiarid areas may help us in management and reclamation of boron polluted soils. The main objective of this study was to investigate the adsorption characteristics of biotite for boron in batch experiments.
Materials and Methods: The adsorption of boron on the adsorbent was studied as a function of pH in the range of 6.5-9.0 with two boron concentrations of 5 mg L-1 and 15 mg L-1. To study the effect of cations and ionic strength on boron adsorption, Mg (NO3)2, Ca (NO3)2 and NaNO3 background electrolytes at three concentration levels (0.03, 0.09 and 0.18 M) were used. Adsorption isotherms were derived by adsorption of boron from solutions containing different concentrations in the range of 1-15 mgL-1 using a 24h batch equilibration. In order to interpret the adsorption behavior of boron, FTIR spectra of the adsorbent was recorded using FTIR spectrophotometer before and after adsorption experiments and species activities of boron were estimated using the Visual MINTEQ speciation program.
Results: The results showed that the amount of boron adsorption increased with increasing equilibrium pH and ionic strength of solution. Boron adsorption increased from 1.28 mmol kg-1 to 2.64 mmol kg-1 as the ionic strength of solution increased from 0.03 M to 0.18 M. Greater adsorption was observed in the presence of Ca2+ and Mg2+ions as compared with Na+ ions at the same concentrations. It thus seems that the much greater loss of B from solution observed in the Ca system was caused by Ca-borate ion pair (CaH2BO3 + and MgH2BO3 +) adsorption. Adsorption isotherms of boron were well described by the Freundlich and Langmuir isotherms. Maximum boron adsorption capacity (qmax) of biotite was obtained to be 27.2 mmol kg-1.
Conclusion: In general, the experimental data showed that less than 6% of initial boron concentration was adsorbed by biotite. Thus, it seems that this mineral does not have a reasonable adsorption capacity for B.

 
Keyword(s): ADSORPTION, MICACEOUS MINERALS, ISOTHERMS, ION SPECIATION
 
References: 
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