Iron(III) Hexamethylenedithocarbamate as a New Flotation Collector
for Separation of Total Chromium
Trajc ˇe Stafilov,
1
Gorica Pavlovska, and Katarina C
ˇ
undeva
Institute of Chemistry, Faculty of Science, Sts. Cyril and Methodius University,
P.O. Box 162, 91001 Skopje, Macedonia
Received January 21, 1998; accepted May 4, 1998
Total chromium is removed from dilute aqueous solutions by means of hexamethyleneammonium
hexamethylenedithiocarbamate (HMA-HMDTC) as a new reagent used for flotation. Amount of
collector-hydrated iron(III) oxide (Fe
2
O
3
xH
2
O) and iron(III) hexamethylenedithiocarbamate (Fe-
(HMDTC)
3
), pH, ionic strength, induction time, etc., necessary for the successful simultaneous
incorporation of Cr(III) and Cr(VI) traces into the structure of collectors was studied. At established
pH (6.0) and ionic strength (0.02 mol/L), using NaDDS as foaming reagent, total chromium can be
separated quantitatively with 10 mg Fe(III) and 0.0003 mol HMDTC
-
added to 1 L of water sample.
Electrothermal vaporization atomic absorption spectrometry (ETVAAS) was applied for determina-
tion of chromium concentration in tap and spring waters. The recoveries of total chromium from
natural water samples have been higher than 95.5%. The limit of detection of chromium by this
method is 0.01 g/L. © 1998 Academic Press
INTRODUCTION
Chromium, existing as trivalent and hexavalent in natural waters, is known as an
essential trace element in plants and warm-blooded animals. Its quantitative excess in
animal and human bodies has many negative consequences. Therefore, it is very important
to know the concentration of this element in environmental water which serves for
drinking or for irrigation. However, when its concentration is extremely low, its direct
determination by atomic absorption spectrometry (AAS) is often difficult or impossible
without any preconcentration. Compared with liquid–liquid extraction, sorption, ion-
exchange, and coprecipitation, flotation techniques have shown to be very much simpler
[1–3]. There are papers about Cr(III) enrichment by colloid precipitate flotation using as
precipitate collectors hydrated metal oxides Fe
2
O
3
xH
2
O[1–4], Al
2
O
3
xH
2
O[5], and
In
2
O
3
xH
2
O[6] and about the determination of Cr(VI) by ion flotation [7, 8]. In a
preceding study [9], sodium tetramethylenedithiocarbamate was found to be a reagent
which ameliorates the properties of the sublate for precipitate flotation of total chromium.
The scope of this work is to consider the possibility of the application of HMA-HMDTC
as a new reagent for chromium colloid precipitate flotation. This organic compound is a
well-known reagent for trace element extraction, coprecipitation, or sorption [10 –22]. Our
investigations have shown that Fe(HMDTC)
3
(a compound obtained during the reaction
between HMA-HMDTC and Fe
2
O
3
xH
2
O) is an insoluble precipitate with meaningful
hydrophobic characteristics, which are the most important criterion for a successful
precipitate flotation. ETVAAS is used as an instrumental method for total chromium
determination in the final solutions concentrated by the proposed flotation procedure.
1
To whom correspondence should be addressed.
MICROCHEMICAL JOURNAL 60, 32– 41 (1998)
ARTICLE NO. MJ981634
0026-265X/98 $25.00
Copyright © 1998 by Academic Press
All rights of reproduction in any form reserved.
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