optimized conditions (alum: pH 4.80, dosage 10,000 mg/L; lateritic
soil: pH 2.0, dosage 14,000 mg/L). Although the removal percentage
was higher using alum, the lateritic soil also provided an ideal
removal percentage for ammoniacal nitrogen.
The possible mechanism for the removal of ammoniacal
nitrogen might be the adsorption of ammonium ion (NH4
þ) on the
coagulated material (lateritic soil) that contains high iron clay
(Umapriya and Shrihari, 2010) and presents of potential of ion
exchange for charged pollutant (Vimonses et al., 2009), especially
for material which have negative charges on the surface. The
ammonium ion being positively charged species are probably
acting as complementary species to extend the effect of Al3þ and
Fe3þ for the coagulation of suspended particles which can be presented