Adsorption/Desorption and Fate of Mercury (II) by Typical Black Soil and Red Soil in China

Abstract

Rapid industrial development in the old northeastern industrial region of China resulted in Hg pollution. A series of batch experiments were conducted to assess the adsorption/ desorption and transfer of Hg (II) within typical black soil in this region and typical red soil in south China as a comparison: both are typical soils in China. It was found that both soils had high affinity for Hg (II) and the absorbed amount was more than 95% of the added. Hg (II) adsorption isotherms were well fitted with the Langmuir and Freundlich equations. The affinity of Hg (II) for black soil was three times higher than that of red soil. Results demonstrated that soil organic matter had an important role in Hg (II) adsorption. Fifty-three and twenty-eight percent of the maximum sorption amount for Hg (II) was contributed by organic matter for black soil and red soil, respectively. Kinetic studies showed that Hg adsorption on both soils was characterized by a biphasic pattern, with a fast step followed by a slow step. Black soil completed 90% of total Hg (II) adsorption in 34 min and reached equilibrium in 321 min, compared to 91 min and 630 min on red soil, respectively.