Abstract
Aluminium ions hydrolyse and polymerise into different species in water. Main aluminium species in aluminium coagulant solutions are monomeric Al species (Al
1) and polymeric Al species
Al
13
O
4
(
OH
)
24
7
+
(Al
13). The aluminium species distribution in coagulant solutions can be influenced by many parameters. This paper studies influences of concentrations of total aluminium species (Al
t) and other species—OH
−, polysilicic acid and ferric species, which were added in aluminium coagulant solutions, on the aluminium species distribution through
27Al nuclear magnetic resonance (NMR) analysis. Results show that only Al
1 and no Al
13 exist in coagulant solutions at higher Al
t concentrations (over 1
mol
l
−1), while both species exist at lower Al
t concentrations (0.1
mol
l
−1). The increase of OH/Al value (molar ratio) increases the concentration of Al
13 in coagulant solutions, while the addition of polysilicic acid and ferric species decreases the concentration of Al
13.