Desferrioxamine-B adsorption to and iron dissolution from palygorskite and sepiolite

Dissolution weathering of minerals can be greatly affected by the presence of siderophores and their adsorption in soil environments. In this research, adsorption equilibria and kinetics of desferrioxamine-B (DFO-B) siderophore on palygorskite and sepiolite, minerals of arid and semiarid soils, were investigated. Iron (Fe) release pattern in the presence of increasing concentrations of DFO-B was also studied. Palygorskite represented a higher capacity but lower affinity for DFO-B adsorption compared to sepiolite. Retention of DFO-B by the minerals was initially rapid and then slowed down as time progressed. Time-dependent DFO-B adsorption to palygorskite and sepiolite was best described by the pseudo second-order and parabolic diffusion models, respectively. The presence of DFO-B enhanced the amount of Fe released from the clay minerals suggesting that siderophore-promoted dissolution might be one of the weathering mechanisms acting on these fibrous clay minerals. Iron concentrations measured in the equilibrium solutions with palygorskite and sepiolite were in the adequate Fe nutrition range for microorganisms and plant roots in soil environments. (C) 2010 Elsevier B.V. All rights reserved.