data were used to determine the maximum P adsorption capacity of
the Al-WTR and other parameters and presented in Table 3. From
Table 3, it can be seen that the adsorption capacity decreased with
an increase in pH from 4 to 9, indicating that the adsorption process
is more favoured under acidic conditions. A decrease in the Al-WTR
adsorption maxima with increasing pH can be attributed to change
of surface potential and competitive adsorption between phosphate
and hydroxyl ions. The pH at the point of zero charge (pHpzc)
also plays an important role in the adsorption phenomenon.