2. ENVIRONMENTAL ChEMISTRy & TEChNOLOGy 2.1. Lectures

Chem. Listy, 102, s265–s1311 (2008) Environmental Chemistry & Technology
Table I
The regression equation for different selected systems
U (VI) Solution regression equation
Basic a y = 4.48x + 1.29
Septonex b y = 4.49x + 0.23
Dodecylsulphate c y = 5.37x + 1.08
0.75 mol dm –3 HnO3 y = 4.04x + 2.18
1 mol dm –3 HCl y = 3.75x + 3.18
PAR d y = 4.95x + 1.32
APDC e y = 4.83x + 0.43
a calibration plots for 1 mg dm –3 –15 mg dm –3 U without orga-
nic reagents ;
b 3 × 10 –3 mol dm –3 Septonex;
c 3 × 10-3 mol dm –3 sodium dodecylsulphate;
d 2 × 10 –5 mol dm –3 PAR;
e 3 × 10 –5 mol dm –3 APDCin solution
Al 3+ . The 10 : 1 excess of multicomponent standards containing
Br – , Cl – , Br – , SO 4 2– , PO4 3– or Cd 2+ , Co 2+ , Cr 3+ , Cu 2+ ,
Mn 2+ , Pb 2+ , V 5+ and Zn 2+ (each of metal ion) in the absence
or presence of Y 3+ internal standard (1 mg dm –3 ) did not
interfere. 10 : 1 excess of Fe 3+ interferes strongly by the 50%
signal decrease in the presence of Y 3+ .
D e t e r m i n a t i o n o f U r a n i u m b y I C P -
A E S A f t e r t h e P r e c o n c e n t r a t i o n o n
M o d i f i e d A m b e r l i t e X A D 4
Prior to the sorption, the column was conditioned by
10 ml of 5 × 10 –3 mol dm –3 Septonex whose pH was adjusted
by hydrochloric acid and sodium hydroxide. This procedure
was always used for the sorption.
E f f e c t o f S u r f a c t a n t s a n d O r g a n i c
R e a g e n t s
The retention efficiency of 3 mg dm –3 U from 50 ml
volume with the optimal pH 9 without surfactants and organic
reagents was 56 % only. The elution of uranium from the
column was carried out with 10 ml acetone and 1 mol dm –3
nitric HnO3 (1 : 1). The various surfactants were used such
as non-ionic Brij 35, cationic Septonex or Zephyramine
and anionic dodecyl sulphate respectively, from which
5 × 10 –3 mol dm –3 of Septonex was optimal for conditioning
and allowed the recovery of 96 % U. The recovery with
dodecylsulphate was 81 % U. Brij 35 produced a foam in the
column and Zephyramine did not prevent turbidity during
evaporation, when HnO3 was used for elution.
Moreover the sorption of 1.5–15 mg dm –3 of U was
quantitative by using 6 × 10 –5 mol dm –3 PAR and 9 × 10–5
– 1.8 × 10 –4 mol dm –3 APDC which corresponds with the 5 or
10 fold excess of reagent and the recovery nearly 100 % was
obtained in the presence of 1.3 × 10 –4 mol dm –3 8-HQS and
1.4 × 10 –4 mol dm –3 PYR. Thus, 6 × 10 –5 mol dm –3 of PAR was
recommended for following preconcentration.
s433
Fig. 1. Effect of organic reagents. pH = 5; pH = 7;
pH = 9; a 6 × 10 –5 mol dm –3 PAR, b 1.2 × 10 –4 mol dm –3 PAR,
c 9 × 10 –5 mol dm –3 APDC, d 1.8 × 10 –4 mol dm –3 APDC,
e 6.7 × 10 –5 mol dm –3 8-hQS, f 1.3 × 10 –4 mol dm –3 8-hQS,
g 1.4 × 10 –4 mol dm –3 PyR; h 2.7 × 10 –4 mol dm –3 PyR, 3 mg dm –3 u
was sorbed after conditioning the sorbent with 5 × 10 –3 mol dm –3
Septonex solution
E f f e c t o f p H
The influence of pH on the sorption follows from Table II.
The sorption was quantitative in the interval of pH 7–9.
Table II
Effect of pH on the sorption a
pH recovery [%]
9 100.0 ± 3.6
8 99.5 ± 3.7
7 100.6 ± 2.4
6 89.6 ± 4.8
5 88.6 ± 5.3
4 82.7 ± 0.9
a From 50 ml of sample with 3 mg dm –3 U, in the presence
of 6 × 10 –5 mol dm –3 PAR and after conditioning the sorbent
with 5 × 10 –3 mol dm –3 Septonex solution. The sorption was
carried out in triplicate
E f f e c t o f E l u e n t s
For the quantitative elution of the complex of uranium
(VI) with the used reagents, acetone, ethanol and methanol
in different ratio with 1 mol dm –3 nitric acid were tested. The
most effective eluent with 100% recovery of U was 10 ml of
1 : 1 acetone and 1 mol dm –3 nitric acid or the 1 : 1 mixture of
acetone and 4 mol dm –3 HnO 3 mixtures. The best eluents are
compared in Table III.
Conclusions
The sorbent XAD-4 in the presence of 4-(2pyridylazo)resorcinol
or pyrrollidincarbodithioate was
observed for the separation and preconcentration of Uranium
(VI) at pH 9. The column of Amberlite XAD 4 of
particle size 0.32–0.63 µm was washed with 10 ml of acetone
and 10 ml of distilled water, and conditioned with