The comparative study of a homogeneous and a heterogeneous system with green synthesized iron nanoparticles for removal of Cr(VI)

Abstract

Green iron nanoparticles (G-nZVI) were synthesized in situ by adding grape-seed extracts and Fe2+ solution simultaneously. The performances for the removal of Cr(VI) were compared in a homogeneous system by original G-nZVI (in suspension) with in a heterogeneous system by treated G-nZVI. The characterization of TEM, SEM, XRD, FTIR and XPS show that G-nZVI is the formation of Fe°-iron oxide core-shell nanoparticles with organic matters in the extracts as capping/stabilizing agents. The same excellent performances on the removal of Cr(VI) were observed in the both systems and the adsorption capacity was from 78.3 to 166.7 mg (Cr)·g−1 (Fe) with the increase of initial Fe2+ concentrations. The pseudo second-order model described the adsorption process excellently and both pseudo first-order and pseudo second-order models fit the reduction process well. It illustrated that the reaction included prompt adsorption and simultaneous redox process. Moreover, the results of thermodynamics study (ΔG° < 0, ΔH° > 0, ΔS° > 0) revealed that the adsorption was a spontaneous and endothermic process. It is obvious that the systhesis of original G-nZVI in the homogeneous system is more simple, rapid, cost-effective and suitable for in situ uses. It holds a great potential for remediation of soil and water.