Adsorption of Rhodamine B onto a yellow–brown soil: Kinetics, thermodynamics, and role of soil organic matter

Abstract

The environmental behavior of organic pollutants in soils depends on their adsorption properties onto soils. In this article, the adsorption process of Rhodamine B (RhB) from an aqueous solution onto a yellow-brown soil in Central China was studied. The isotherms and the kinetic data of the RhB adsorption onto the soil were well approached by the Freundlich isotherm model (R 2 > 0.999) and the pseudo-secondorder kinetic model (R 2 > 0.99). The adsorption process of RhB onto the soil was endothermic and increased temperature was conducive to the adsorption process. The adsorption percentage of RhB onto the soil decreased with increasing pH in the range from 2.32 to 10.96. With an increase in the ratio of soil to water, the desorption rate of RhB in the soil clearly decreased. Soil organic matter is the main contribution to RhB adsorption onto the soil. A possible complex mechanism of the adsorption was suggested on the basis of concurrent operation of electrostatic attraction, and hydrogen and chemical bonding forces.

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