Effect of Low-Molecular Organic Acids on the Migration Characteristics of Nickel in Reclaimed Soil from The Panyi Mine Area in China

This study investigated the effects of low molecular weight organic acids (citric acid and malic acid) on the migration properties of nickel in soil. A reclaimed soil sample was obtained from the Panyi Mine in Huainan City, China. The effects of adding different concentrations of Ni, citric acid (CA) and malic acid (MA) were assessed on the migration and transformation of soil Ni forms. The results showed: (1) An increase in soil Ni activity with increasing Ni concentrations. (2) An increased proportion of exchangeable forms of Ni in soil with increased malic acid and citric acid concentrations, effectively promoting Ni mobility. In addition, the active Ni fraction in reclaimed soil increased significantly with increasing concentrations of citric and malic acid. The nickel activation effect of citric acid was found to be higher than that of malic acid. (3) The activation effect of organic acids on Ni weakened with aging, exhibiting a gradual transformation from the loosely bound form of Ni, to the strongly bound form. The results of this study provide a theoretical basis for improving the effectiveness and efficiency of the phytoremediation techniques used for the treatment of Ni-polluted soils.