TITLE:
Application of Iron Nanoparticles Synthesized by Green Tea for the Removal of Hexavalent Chromium in Column Tests
AUTHORS:
C. Mystrioti, A. Xenidis, N. Papassiopi
KEYWORDS:
Nanoscale Zero Valent Iron, nZVI, Hexavalent Chromium, Reductive Capacity, Column Tests
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.2 No.4,
July
11,
2014
ABSTRACT: Nano zero valent iron particles (nZVI) are
popular the last few years because of the numerous applications in remediation
of a wide range of pollutants in contaminated soils and aquifers. The nZVI
particles can be 10 - 1000 times more reactive than granular or micro-scale ZVI
particles due to the small particle size, large specific surface area and high
reactivity. An alternative green synthesis procedure was used for the
production of nano zero valent iron particles (nZVI) using green tea (GT)
extract, which is characterized by its high antioxidant content. Polyphenols in
green tea extract possess double role in the synthesis of nZVI, because they
not only reduce ferric cations, but also protect nZVI from oxidation and
agglomeration as capping agents. The objective of current study was to simulate
ata laboratory scale the attachment of GT-nZVI particles on soil material and
study the effectiveness of attached nanoparticles for removing hexavalent
chromium (Cr(VI)) from contaminated groundwater flowing through the porous soil
bed. Column tests were carried out with various flowrates in order to examine
the effect of contact time between the attached on porous medium nZVI and the
flow-through solution on Cr(VI) reduction. After the completion of column tests
the soil material in each column was split in 5 vertical sections, which were
further subjected to chemical analyses and leaching tests. According to the
results of the study increasing the contact time favors the reduction and
removal of Cr(VI) from the aqueous phase. The reductive precipitation of Cr can
be described as a reaction that follows a pseudo-first order kinetic law, with
rate constant equal to k = 0.0243 ± 0.0011 min-1. Leaching tests indicated that
precipitated chromium is not soluble. In the examined soil material, the total
amount of precipitated Cr was found to range between 280 and 890 mg/(kg soil),
while soluble Cr was less than 1.4 mg/kg and most probably it was due to the
presence of residual Cr(VI) solution in the porosity of soil.