2. ENVIRONMENTAL ChEMISTRy & TEChNOLOGy 2.1. Lectures

Chem. Listy, 102, s265–s1311 (2008) Environmental Chemistry & Technology
concentration range 0.5–10 g dm –3 . The results are presented
in Table II. Increase of the sorbent dose in solution caused
a decrease of akaganeite sorption capacity. However, this is
not a good indicator of sorption ability, because with bigger
sorbent concentrations all the available active sorption sites
are not occupied. It is important to see what is the remaining
As (V) concentration after treatment. In a real system this is
the important factor; the remaining concentration should be
below the limits. In the last column of Table III the remaining
concentrations are given. It is observed a significant decrease
of the remaining As (V) conc. with increase of the sorbent
dose. It seems that a good dose is 5 g dm –3 , which gives a
96 % removal and a satisfactory final As concentration of
4 mg dm –3 .
Table III
The effect of sorbent dose
C S [g dm–3 ] Q [mg g –1 ] C eq [mg dm –3 ]
0.5 43.0 78.5
1.0 41.4 58.6
2.0 36.3 27.4
5.0 19.2 4.0
10.0 9.6 4.0
Conclusions
Synthetic akaganeite is a suitable sorbent for arsenic
removal, especially at acidic environment. It is a low cost
sorbent, as it is prepared from easily available cheap inorganic
materials and has a good efficiency (above the average
s473
reported in the literature). It removes arsenic by chemical
sorption favored by an increase of temperature and the best
results are obtained at pH 3.5. However, at pH 7.0, gives
also satisfactory results. This is important for the treatment
of drinking water. The capacity of the material was not affected
significantly with increased ionic strength (up to 0.1 M
nanO 3 ). The experimental data follow (with good agreement)
the Freundlich isotherm.
Acknowledgement (This work has been supported by
Slovak Research and Development Agency project No APVT-
51-017104 and Scientific Grant Agency VEGA, project no.
2/0087/08)
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