University of Tehran Press Iranian Journal of Soil and Water Research 2008-479X 56 1 2025 03 21 The effect of leonardite on the adsorption and desorption characteristics of boron in calcareous soils The effect of leonardite on the adsorption and desorption characteristics of boron in calcareous soils 43 54 101487 10.22059/ijswr.2024.382955.669798 FA Reyhaneh Abbasi Esakan . Department of Soil Science, Faculty of Agriculture, University of Urmia, Urmia 0000-0002-8423-6672 Behnam Dovlati Department of Soil Science, Faculty of Agriculture, Urmia University, Urmia, Iran 0000-0002-7452-5278 Ebrahim Sepehr Department of Soil Science, Faculty of Agriculture, Urmia University, Urmia, Iran 0000-0001-5843-0669 Marziyeh Piri Department of Soil Science, Faculty of Agriculture, Urmia University, Urmia, Iran 0000-0003-0042-5060 Journal Article 2024 09 28 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 (q_max) and the Langmuir adsorption energy (K_L), as well as the maximum adsorption capacity of Dubinin-Radushkevich (q_s). 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. 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 (q_max) and the Langmuir adsorption energy (K_L), as well as the maximum adsorption capacity of Dubinin-Radushkevich (q_s). 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. https://ijswr.ut.ac.ir/article_101487_c05e0a5cc7651ff7660aec86f3f28a97.pdf