Zero-valent iron (ZVI) aerogels have been synthesized by sol-gel method and supercritical CO2 drying, followed by H2 reduction in the temperature range of 350-500 ℃. When applied to trichloroethylene (TCE) dechlorination, the ZVI aerogel reduced at 370 ℃ showed the highest performance in the conditions employed in this study. Thus, the effect of reduction temperature in preparing ZVI aerogels has been investigated by several characterizations such as BET, XRD, TPR, and TEM analyses. As the reduction temperature decreased from 500 to 350 ℃, the BET surface area of the resulting aerogels increased from 6 to 30 m2/g, whereas their Fe^(0) content decreased up to 64%. It was also found that H2 reduction at low temperatures such as 350 and 370 ℃ leads to the formation of ZVI aerogel particles consisting of both Fe^(0) and FeOx in the particle cores with a different amount ratio, where FeOx is a mixture of maghemite and magnetite. It is, therefore, suggested that reduction at 370 ℃ for ZVI aerogel preparation yielded particles_x000D_ homogeneously composed of Fe^(0) and FeOx in the amount ratio of 87/13, resulting in high TCE dechlorination rate. On the other hand, when Pd- and Ni-ZVI aerogels were prepared via cogellation and then applied for TCE dechlorination, we also observed a similar effect of reduction temperature. However, the reduction at 350 or 370 ℃ produced Pd- or Ni-ZVI aerogel particles in which Fe^(0) and Fe3O4 co-exist homogeneously. Since both Fe^(0) and Fe3O4 are advantageous in TCE dechlorination, the activities of Pd- and Ni-ZVI aerogels reduced at 350 ℃ were comparable to those of both aerogels reduced at 370 ℃, although the former aerogels have less Fe^(0) content.

Zero-valent Iron Aerogel Dechlorination Trichloroethylene Thermal Reduction

Kao CM, Chen SC, Liu JK, Chemosphere, 43, 1071 (2001)
Scherer MM, Richter S, Valentine RL, Alvarez PJJ, Critical Reviews in Environmental Science and Technology, 30, 363 (2000)
Meyer DE, Bhattacharyya D, J. Phys. Chem. B, 111(25), 7142 (2007)
Ponder SM, Darab JG, Mallouk TE, Environ. Sci. Technol., 34, 2564 (2000)
Ponder SM, Darab JG, Bucher J, Caulder D, Craig I, Davis L, Edelstein N, Lukens W, Nitsche H, Rao L, Shuh DK, Mallouk TE, Chem. Mater., 13, 479 (2001)
Schrick B, Blough JL, Jones AD, Mallouk TE, Chem. Mater., 14, 5140 (2002)
Wang CB, Zhang WX, Environ. Sci. Technol., 31, 2154 (1997)
Nurmi JT, Tratnyek PG, Sarathy V, Baer DR, Amonette JE, Pecher K, Wang C, Linehan JC, Matson DW, Penn RL, Driessen MD, Environ. Sci. Technol., 39, 1221 (2005)
Glavee GN, Klabunde KJ, Sorensen CM, Hadjipanayis GC, Inorg. Chem., 34(1), 28 (1995)
Duxin N, Stephan O, Petit C, Bonville P, Colliex C, Pileni MP, Chem. Mater., 9, 2096 (1997)
Duxin N, Pileni MP, Wernsdorfer W, Barbara B, Benoit A, Mailly D, Langmuir, 16(1), 11 (2000)
Carpenter EE, Calvin S, Stroud RM, Harris VG, Chem. Mater., 15, 3245 (2003)
Uegami M, Kawano J, Okita T, Fujii Y, Okinaka K, Kakuya K, Yatagai S, US Patent 7,022,256 (2006)
Liu Y, Choi H, Dionysiou D, Lowry GV, Chem. Mater., 17, 5315 (2005)
Mackenzie PD, Horney DP, Sivavec TM, J. Hazard. Mater., 68, 1 (1999)
Liu CC, Tseng DH, Wang CY, J. Hazard. Mater., 136(3), 706 (2006)
Johnson TL, Fish W, Gorby YA, Tratnyek PG, J. Contam. Hydrol., 29, 379 (1998)
Williams AGB, Scherer MM, Environ. Sci. Technol., 38, 4782 (2004)
Zhang WX, Wang CB, Lien HL, Catal. Today, 40(4), 387 (1998)
Nyer EK, Vance DB, Ground Water Monit. Rem., 21, 41 (2001)
Gash AE, Tillotson TM, Satcher Jr. JH, Poco JF, Hrubesh LW, Simpson RL, Chem. Mater., 13, 999 (2001)
Wimmers OJ, Arnoldy P, Moulijn JA, J. Phys. Chem., 90, 1331 (1986)
Tiernan MJ, Barnes PA, Parkes GMB, J. Phys. Chem., 105, 220 (2001)
Carpenter EE, Long JW, Rolison DR, Logan MS, Pettigrew K, Stroud RM, Kuhn LT, Hansen BR, Morup S, J. Appl. Phys., 99, 08N711 (2006)