One-pot synthesis and characterization of FeII-FeIII hydroxide (green rust) intercalated with C9-C14 linear alkyl carboxylates

Layered Fe-II-Fe-III hydroxides (green rusts GR) Intercalated with monovalent aliphatic carboxylate anions called GR-carboxylates possess hydrophobic interlayer regions which can adsorb non-polar organic compounds GRs are well known reductants and hence GR-carboxylates may have the potential to detoxify adsorbed compounds such as chlorinated solvents GR-carboxylates GR(CX) for the first time were precipitated directly by aerial oxidation of an ethanolic solution containing FeSO4 and linear alkyl carboxylate ions synthesis condition using monovalent carboxylic acids with X. the total number of carbon atoms in the acid varying from 5 (pentanoic acid) to 14 (tetradecanoic acid) synthesis conditions were tested GR(CX) formed for X >= 9 The syntheses were carried out at constant pH of 8 using 1 M NaOH as neutralizing agent and with a maximum duration of 3 5 h The basal spacings of GR(CX) increased with X and they were 2 68 nm (GR(C9)) 294 nm (GR(C10)) 359 nm (GR(C12)) and 416 nm (GR(C14)) The Mossbauer spectra measured at 80 K of different GR(C12) synthesized under identical chemical conditions resulted in hyperfine parameters close to those of other GRs The Fe-II/Fe-III ratios of the final products (R) ranged between 1 4 and 2 8 demonstrating that Fe-II in GR(CX) can be partly oxidized without degradation of the structure R at various stages of the synthesis decreased from 5 2 at the start of the reaction to 2 8 at the end of synthesis In the specific case of GR(C12) the optimum initial solution concentrations were [C12](0)=25 mM [Fe-II](0)= 30 mM and 40% (v/v) EtOH/H2O (C) 2010 Elsevier B V All rights reserved