Table 5 Change in the concentration of iron ions, depending on the area of
contact of the sample (within a day) (С
initial
= 5 mg/dm
3
, V
initial
=100 cm
3
)
Fe
3+
, mg/dm
3
Fe
2+
, mg/md
3
V after 24 h, cm
3
Contact area, cm
2
2,57
2,43
35
283,4
0,7
4,3
42,8
199,5
0,2
4,8
82,5
74,2
0,41
4,59
44
169
0,05
4,95
96
45,3
Analysis of obtained data it can be conclude that the larger the contact area, the
more intense the transition of Fe
2+
ions in Fe
3+
is observed. This is due to the greater
amount of oxygen entering the sample and intensifying the process of changing the
concentration of iron ions during the day. Thus, at contact area 283,4 cm
2
there is the
the smallest residual concentration of Fe
2+
ions (С(Fe
2+
) = 2,43 mg/dm
3
is observed.
Changing in the concentration of iron ions depending on the pH at different
concentrations of the model solution
The data of the processes of reduction of the content of iron ions (II) at various
pH values of model solutions are presented (Fig. 5). At values of pH > 4,5, bivalent
iron is oxidized to trivalent and precipitates in the form of hydroxide, while the fullness
of oxidation increases with increasing pH. In a reducing medium (at pH> 8.4) iron
carbonate can sediment.
A number of experiments were carried out for various initial concentrations of
model solutions С
initial
(Fe
2+
) = 1 mg/dm
3
, С
initial
(Fe
2+
) = 2 mg/dm
3
, С
initial
(Fe
2+
) = 5
mg/dm
3
. The results of the experiments are shown in the Fig. 7.
a
b
c
Figure 7. Reducing in the concentration of iron bivalent in samples with
different values рН at С
initial
(Fe
2+
)= 1 (а), 2 (b), 5 (c) mg/dm
3
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