Interaction between Cu^(2+) and different types of surface-modified nanoscale zero-valent iron during their transport in porous media

摘要

This study investigated the interaction between Cu^(2+)and nano zero-valent iron(NZVI)coated with three types of stabilizers(i.e., polyacrylic acid [PAA], Tween-20 and starch) by examining the Cu^(2+) uptake, colloidal stability and mobility of surface-modified NZVI(SM-NZVI) in the presence of Cu^(2+). The uptake of Cu^(2+)by SM-NZVI and the colloidal stability of the Cu-bearing SM-NZVI were examined in batch tests. The results showed that NZVI coated with different modifiers exhibited different affinities for Cu^(2+), which resulted in varying colloidal stability of different SM-NZVI in the presence of Cu^(2+). The presence of Cu^(2+)exerted a slight influence on the aggregation and settling of NZVI modified with PAA or Tween-20. However, the presence of Cu^(2+)caused significant aggregation and sedimentation of starch-modified NZVI, which is due to Cu^(2+)complexation with the starch molecules coated on the surface of the particles. Column experiments were conducted to investigate the co-transport of Cu^(2+) in association with SM-NZVI in water-saturated quartz sand. It was presumed that a physical straining mechanism accounted for the retention of Cu-bearing SM-NZVI in the porous media. Moreover, the enhanced aggregation of SM-NZVI in the presence of Cu^(2+)may be contributing to this straining effect.