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REMOVAL
OF HEXAVALENT CHROMIUM FROM AQUEOUS SOLUTIONS BY SCRAP IRON FILINGS
Suwannee Junyapoon* and Suttawadee Weerapong
Department
of Chemistry, Faculty of Science
King Mongkut's Institute of Technology Ladkrabang
Chalongkrung Road, Ladkrabang District, Bangkok 10520, Thailand
ABSTRACT
Chromium
is an important industrial metal used in various products and processes.
Hexavalent chromium is relative mobile in the environment and is
acutely toxic, mutagenic, teratogenic and carcinogenic. The impacts
of chromium on human health and the environment is of wide concern.
Therefore, it is imperative that hexavalent chromium be removed
from wastewater. A removal of hexavalent chromium using scrap iron
filings was studied in both synthetic wastewater, containing 30
mg l-1 of hexavalent chromium, and chromium plating wastewater.
All experiments were evaluated in batch experiments. Effective conditions
for removal of hexavalent chromium were found to be pH of 3, iron
particle sizes of 35 - >200 mesh, agitating rate at 250 rpm,
contact time at 180 mins., iron dosage of 1 g. According to the
experiment results, almost all of hexavalent chromium was transformed
to trivalent chromium. Trivalent chromium and total iron in the
aqueous solution were then removed by precipitation with alkaline
solutions. In this work, sodium hydroxide and calcium hydroxide
were used. It was found that the use of sodium hydroxide was more
effective than that of calcium hydroxide. The reaction rate constants
from the results following first order reaction were calculated.
In addition, it was found that nickel and copper in the aqueous
solution did not affect on the reduction of hexavalent chromium.
KEYWORDS:
chromium
plating wastewater, hexavalent chromium, scrap iron filings
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