Characteristics and behaviour of vanadium(V) adsorption on goethite and birnessite

Ferromanganese oxides, as abundant minerals in natural waters and soils, would affect the transport and fate of vanadium(V) in the environment. The adsorption behaviour of V(V) on synthesized goethite and birnessite under environmental factors including pH, ionic strength, coexisting substances such as anions, cations, and fulvic acid (FA) was investigated by batch experiments. The results indicated that the kinetics model of V(V) adsorption on goethite and birnessite well fitted with pseudo-second-order, and the adsorption equilibrium was achieved in 60 min and 120 min, respectively. The V(V) adsorption isotherms for goethite and birnessite conformed to the Langmuir isotherm with maximum adsorption amount of 8.24 and 9.11 mg center dot g(-1), respectively. The higher V(V) adsorption capacity on goethite was observed at pH 4-8, while that on birnessite occurred at pH 2 owing to their different point of zero charge pH. The V(V) adsorption amounts of the synthesised materials were decreased with the increase in ionic strength of NaNO3 but increased with the elevating FA concentration in solution. The inhibitory effect on V(V) adsorption was found in the presence of anions of PO43- and SO42-, while cations like Ca2+ and Mg2+ facilitated the adsorption. The obtained results are of great importance to understand V(V) mobility in soil and aqueous environment.