Chromium (VI) Retrieval from Chromium Ore Processing Residues by Electrokinetic Treatment
Abstract
Electrokinetics (EK) was investigated as a
possible technique for in-situ treatment of leachable
chromium at a built site contaminated with chromium
ore processing residues (COPR). A preliminary EK
experiment was carried out at the laboratory scale on
an undisturbed COPR core sample. Methods applied for
material and pore water characterization before and after
EK treatment addressed physical aspects by laser diffraction
granulometry, pycnometry and pore water
content, mineralogical aspects by X-ray diffraction,
scanning electron microscopy coupled with energy dispersive
X-ray spectroscopy, and chemical aspects by
inductively coupled plasma-atomic emission spectroscopy
and atomic absorption spectroscopy for elemental
composition, spectrophotometry for Cr(VI) analysis,
and potentiometry for pH determination. EK was run
at 1 V/cm with no external constraints on current intensity.
The EK experiment reached an extraction of 72%
of the total leachable Cr(VI) after only 10 days of
treatment and 84% after 20 days. Material texture, composition,
and pH remained similar. These results indicate
that EK presents a potential solution for extracting
leachable Cr(VI) from COPR sites. The impounded
COPR material appeared to be heterogeneous in composition
at all scales, from field to lab sample, adding to
the challenge of in-situ treatment.