3.3. Effects of pH
The highest COD and color removal efficiency values were
attained by applying alum as the coagulant were achieved with
a pH 4.80 as presented in Fig. 3. The percentage of COD removal at
pH 4.80 was 68.9%, while the percentage of color removal was 89%
at the same pH level. This phenomenon is in agreement with
previous experiments that showed the extent of pH not only
depends on the type and concentration of the coagulant but also on
the characteristics of the wastewater itself (Aziz et al., 2007b).
Under acidic conditions, the amount of cationic ions (Al3þ)
increased, resulting in high coagulation activity because the charge
neutralization effect between negatively charged suspended or
colloidal particles was maximized. Alternatively, the best pH value
for the lateritic soil used as a coagulant is at a pH of 2.00 and is
displayed in Fig. 4, where the percentages of COD and color removal
were 40% and 61.9%, respectively. The treatment of leachate using
lower pH values shows better results Wang et al. (2002). The soils
generally act as ion exchangers because they are alumino silicates.
In water solution, exchange may take place releasing the hydrogen
ions which is responsible for the acidic pH. Then, the pH was
3.3. Effects of pHThe highest COD and color removal efficiency values wereattained by applying alum as the coagulant were achieved witha pH 4.80 as presented in Fig. 3. The percentage of COD removal atpH 4.80 was 68.9%, while the percentage of color removal was 89%at the same pH level. This phenomenon is in agreement withprevious experiments that showed the extent of pH not onlydepends on the type and concentration of the coagulant but also onthe characteristics of the wastewater itself (Aziz et al., 2007b).Under acidic conditions, the amount of cationic ions (Al3þ)increased, resulting in high coagulation activity because the chargeneutralization effect between negatively charged suspended orcolloidal particles was maximized. Alternatively, the best pH valuefor the lateritic soil used as a coagulant is at a pH of 2.00 and isdisplayed in Fig. 4, where the percentages of COD and color removalwere 40% and 61.9%, respectively. The treatment of leachate usinglower pH values shows better results Wang et al. (2002). The soilsgenerally act as ion exchangers because they are alumino silicates.In water solution, exchange may take place releasing the hydrogenions which is responsible for the acidic pH. Then, the pH was
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