Adsorption and Desorption Characteristics of Vanadium (V) on Silica

With the extensive mining of vanadium (V) ore, much attention has been focused on soil V pollution and its hazards. This study was conducted to investigate the adsorption-desorption properties of V on silica under various conditions, such as initial vanadate (V(V)) concentration, reaction time, pH, ionic strength, and temperature. The Langmuir and Freundlich isotherm models were applied to describe the adsorption of V(V) on silica and the results indicate that the adsorption was mainly monolayer adsorption. The kinetic studies show that the mechanisms of V adsorption on and desorption from silica were different from one another. The main adsorption-desorption-controlling step was chemical reaction, whereas V adsorption on silica also involved the diffusion. The adsorption-desorption procedure was highly dependent on the initial V(V) concentration and solution pH. Adsorption of V(V) increased with an increase in initial concentration and the maximum adsorption capacity was observed at solution pH 3.0–5.0. At 29.1 mg L −1 initial V(V), and silica dosage 36.4 g L −1 at 25 °C, the adsorption amount reached maximum of 82.7 mg kg −1 and the corresponding desorption rate was 5.44%. Therefore, silica is an effective adsorbent which can fix V in the soil.