306
N. Narkis et al.
]
l
i.
~
J:I5
i ~
=2
E 0
6
4
1
0
-2
0.4
0.3
--0- CP400
....... CP401
0.2
0.1
o.o+-.-.... ~....,....,..,.::~i;IdjI!~~L...,--,r--r-t
o 1 1 3 .. 5 , 7 8 , 10 11 12
POLYMER DOSE mg/L
Fig. 3. Flocculation and electrophoretic mobility curves for Separan Cp-400 and
Cp-402 when used as primary flocculants
Some characteristics of the combined flocculation of Al (III) with different
polymers can be summarized as follows:
• The effect of the "combination" in reducing the aluminium nitrate optimal dose
in the copolymers' case was more pronounced. Reducing the aluminium nitrate
optimal flocculant dose by 50%, i.e. to 5 . 10 5 M required the use of one third of
the cationic polyelectrolyte copolymer optimal dosages, when used alone .
• With the two constant underdose aluminium nitrate concentrations, 2 . 10 5 M and
5 . 10 5 M, in combination with the copolymers, the EM at the optimal polymer
doses, was changed only slightly. As previously mentioned, considerable
reduction in the EM was noticed at the copolymer optimal flocculant dose, when
used alone. When Separan Cp-400 and constant aluminium nitrate 5 . 10 5 M were
-1 -1
-1
employed, an EM of -1.8 f.l s V cm at the polymer optimal dose was obtained,
-1 -1
-1
as compared to -0.6 f.l s V cm ,when the polymer was used alone (Fig. 4).