In this study, batch and column experiments were conducted to investigate the effect of MgO nanoparticles (NPs), humic acid and biochar for boron (B) immobilization in contaminated soil. Results showed that the fate and mobility of B was controlled by adsorption reactions and the amount of B adsorption increased in soil treated with MgO at 2% wt while the amount of B adsorption declined in presence of humic acid and biochar treatments. Maximum adsorption on the basis of isothermal curves was 85.9, 94.0, 50.9 and 83.6 mg kg−1 for control, MgO, humic acid and biochar treatments, respec- tively. Fractionation of isotherm experiments in soil treated by MgO NPs, humic acid and biochar indicated that compared to control soil the exchangeable fractions decreased in all treatment at initial B concentration of 2 mg L−1 while an increase was observed at initial B concentration of 10 mg L−1. Boron in organic fraction has also enhanced by biochar and humic acid application while this fraction reduced in presence of MgO NPs. Residual fraction showed an increase in presence of MgO NPs and biochar at low initial concen- tration of B while it reduced in soil treated with humic acid. Column breakthrough testing indicated the outlet concentration becomes equal to the inlet concentration after pore volumes of 4, 26, 3 and 1 for soil control, soils treated by MgO NPs, humic acid and biochar, respectively.
