The effect of leonardite on the adsorption and desorption characteristics of boron in calcareous soils

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Document Type : Research Paper

Authors

1 . Department of Soil Science, Faculty of Agriculture, University of Urmia, Urmia

2 Department of Soil Science, Faculty of Agriculture, Urmia University, Urmia, Iran

Abstract

The adsorption and desorption processes play a crucial role in the solubility of boron (B) in soil solutions. To investigate the effect of leonardite on the adsorption and desorption processes of B, an experiment was conducted on four calcareous soil samples at three weight levels of 0%, 2%, and 4%, along with nine B concentration series (0-120 mg/L) using a 0.03 M sodium chloride background solution. A 0.03 M sodium chloride solution was utilized for the desorption of boron. The B adsorption data were fitted to Langmuir (R² = 0.85-0.96), Freundlich (R² = 0.62-0.88), Temkin (R² = 0.77-0.98), and Dubinin-Radushkevich (R² = 0.94-0.99) models. The results indicated that the addition of leonardite reduced the adsorption parameters of B, including the maximum single-layer adsorption of Langmuir (qmax) and the Langmuir adsorption energy (KL), as well as the maximum adsorption capacity of Dubinin-Radushkevich (qs). Applying 4% of leonardite resulted in a 32% reduction in qmax in soil 1. The average adsorption energy (E) calculated using the Dubinin-Radushkevich equation indicates a physical adsorption of B in soils, as E is less than 8 kJ/mol. Furthermore, application of leonardite inceased desorption of B in soils, leonardite's effect was 4% more than 2%. Therefore, the application of leonardite can increase the boron toxicity levels in soils, especially in calcareous soils.

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Iranian Journal of Soil and Water Research

Articles in Press, Accepted Manuscript
Available Online from 06 November 2024

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