Green rusts are Fe(II)-Fe(III) layered double hydroxides with a pyroaurite-type structure having alternating positively charged Fe(II)-Fe(III) hydroxide layers and hydrated anion (commonly Cl -, SO4 2-, or CO3 2-) layers . Green rusts are key components of the biogeochemical cycling of Fe in aquatic and terrestrial systems and are found in Fe(II)-Fe(III) transition zones in a variety of natural and engineered environments . They are highly redox-active, and over the past 30 years have been shown to reduce a wide range of organic and inorganic pollutants including transition metals (V(V), Cr(VI), Cu(II), Tc(VII), Ag(I), Pt(VI), Au(III), and Hg(II)) , metalloids (Se(VI) and Te(VI)/(IV)) , actinides (U(VI) and Np(V)) , nitrate , azo dyes , nitroaromatics (PNP and TNT) , organo-nitrogen explosives (NTO, DNAN, HMX, and RDX) , and halogenated organics .