increase in the iron ions content in the source water to 5.0 and 7.0 mg/dm
3
, aeration for
10 minutes allows to reduce the residual the content to 0.47 and 0.52 mg/dm
3
,
respectively, with a permitted maximum of 0.3 mg/dm
3
. The degree of purification of
water is 73-85%, 60-71%, 70-85%, 70-90%, 75-93% for the initial concentrations of
0.65; 1.0; 2.0; 5,0 and 7,00 mg/dm
3
(Fig. 7).
Better conditions for oxidation of iron ions are provided in an electrolyzer with
flat electrodes located at a distance of 0.04-0.05 m. It is established that the residual
iron content with increasing current density decreases. To achieve the residual content,
which corresponds to the normative data, the current density should be greater than 2.0
mA/cm
2
. The results of studies at a constant current density of 2.7 mA/cm
2
using flat
electrodes are presented in Fig. 10. A further increase in the current strength is not
feasible because of a significant increase in voltage.
a
b
Figure 10. The dependence of the concentration of iron ions on the time of
electrolysis (1; 2) and the effect of iron removal of water (3, 4) at a concentration of
iron in the initial water of 0.65 mg/dm
3
(1, 3) and 7.00 mg/dm
3
(2, 4)
From Fig. 8 it is obvious that the permissible concentration of iron ions in water
was obtained at the electrolysis time of 1 and 3 minutes for the iron ions content in the
initial water 0.65 and 7.00 mg/dm
3
, respectively. In this case, the degree of purification
of water is 77-88% and 90-100% for the initial concentrations of 0.65 and 7.00 mg/dm
3
,
respectively.
In order to create low-waste technologies for the iron ions removal from waste
water, it is necessary to provide the recycling of formed sediments. To dewatering
sediments it is proper to apply polyacrylamide and calcium-containing substances, with
following mechanical dehydration, after which the sediments can be added to the
composition of building materials. Based on the results, scheme for iron ions removal
from water was proposed (Fig. 11).
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