Effect of Surfactants on Zero‐Valent Iron Nanoparticles (NZVI) Reactivity

Abstract

Abstract Zero‐valent iron nanoparticles (NZVI) were synthesized and dispersed in solutions of sodium oleate (SO), sodium laurate (SL), sodium dodecyl phosphonate (SDP), and sodium dodecyl sulfate (SDS). The reactivity of these dispersions was evaluated to assess the impact of surfactants on the reduction rate of hydrophilic reactive black 5 (RB5) and hydrophobic carbon tetrachloride (CT) model contaminants. SO and SL, used at their critical micelle concentration (CMC), lowered the reduction rate of RB5 by two and three orders of magnitude, respectively. SO and SL also decreased the reduction rate of CT by up to one order of magnitude. SDS and SDP, at their CMC, decreased the reduction rate of RB5 by approximately 50‐fold, but increased the reduction rate of CT. The decrease in RB5 reduction rate might be explained by the formation of adsorbed surfactant species on the surface of NZVI that could hinder the transport of RB5 and other hydrophilic species. For SO and SL, the inhibition of RB5 and CT reduction might also be explained by the binding of carboxylates to NZVI. The increase in CT reduction rate with SDS and SDP suggests that providing a non‐binding lipophilic environment on the surface of NZVI would improve the reduction rate and selectivity towards the reduction of hydrophobic contaminants.