Transport and distribution of surface-modified Fe-Mn binary oxides in heterogeneous porous media and their arsenic stabilization performance

Column experiments were designed and conducted to study the transport of starch- and starch-xanthan gum modified Fe-Mn binary oxide particles (SFM and SXFM) in saturated heterogeneous porous media and to evaluate the influence of the heterogeneity structure; to determine the improved particle distribution uniformity enhanced by shear thinning fluid delivery; and to evaluate the arsenic (As) stabilization performance of these remedial amendments. Fine-in-coarse (FIC) and coarse-in-Fine (CIF) patterns of heterogeneous packings were set up in the columns. Column effluent breakthrough analysis, visual observation during injection, and column sectioning and sand pack sampling were applied to study the transport, distribution, and As immobilization of the particulate amendments. Results indicated that (1) SFM was more mobile than SXFM; (2) Starch-xanthan gum dual modification on Fe-Mn binary oxide particles successfully improved their migration capability in heterogeneous porous media and the distribution uniformity attributed to the shear thinning behavior of xanthan gum solution; (3) both SFM and SXFM stabilized As in heterogeneously packed soil collected from a contaminated site, with SXFM showing better immobilization performance than SFM.