Inorganic polymeric coagulating chemicals applied in water
treatment can achieve rapid flocculation and sedimentation of
colloidal particles in water bodies (Zouboulis et al., 2007). The
modes of action of these chemicals are generally explained in
terms of two distinct mechanisms: charge neutralization of
negatively charged colloids by cationic hydrolysis products and
incorporation of impurities in an amorphous hydroxide precipitate
(“sweep flocculation”) (Duan and Gregory, 2003). These coagulation
mechanisms may be used to overcome the high dispersion of
hard saline–sodic soils and promote the formation of aggregate
structures, thereby eventually improving soil porosity, water
holding capacity, and permeability. Furthermore, many inorganic
polymers can produce H+ ions by hydrolysis (Zouboulis et al.,
2007), which results in considerable reduction in soil pH and
facilitates the dissolution of CaCO3 to provide Ca2+ ions for
ameliorating saline–sodic soils.