Adsorption and Desorption Characteristics of Vanadium (V) on Coexisting Humic Acid and Silica

Vanadium (V) has been progressively studied due to its potential toxicity in the environment as a trace metal. A coexistence system of humic acid (HA) and silica was employed to simulate the main organic and inorganic components of soil. The adsorption and desorption characteristics of V by the system and the effects of several environmental conditions were investigated. The adsorption data were well described by the Langmuir and Freundlich models, illustrating that the adsorption of V on HA + silica was a monolayer adsorption. The kinetic study indicated that the main adsorption controlling step was a chemical reaction. The thermodynamic study showed that the adsorption was exothermic and spontaneous. The adsorption-desorption process was strongly dependent on the solution pH and HA concentration, while temperature (4–75 °C) and ionic strength (< 1 mol L−1) showed limited effect on overall adsorption performances. In general, the results revealed a considerable V fixation ability of HA-silica coexistence system. The mobility and bioavailability of V in soil was effectively reduced by coexisting HA and silica.