Comparison of coagulation behavior and floc characteristics of titanium tetrachloride (TiCl<inf>4</inf>) and polyaluminum chloride (PACl) with surface water treatment

Coagulation behavior of Titanium tetrachloride (TiCl4) and polyaluminum chloride (PACl) was comparatively investigated in terms of the removal of turbidity and natural organic matter (NOM) with surface water. The growth, breakage and re-growth nature of flocs were also compared. The results show that the removals of chemical oxidation demand (CODMn) and dissolved organic carbon (DOC) were 51.5% and 78.4% at optimal dosage for TiCl4 and 29.8% and 41.0% for PACl, respectively. The floc breakage and re-growth indicated that TiCl4 and PACl coagulation occurred not only by charge neutralization but also by a form of sweep flocculation. Besides, flocs formed by PACl had better recoverability than the flocs formed by TiCl4. Sludge produced from TiCl4 flocculation was calcined at 600°C to produce TiO2, and the photocatalytic activity in removing reactive brilliant red (K-2BP) was evaluated in comparison with commercially available TiO2 (P-25). The photocatalytic oxidation rates of K-2BP after 2h photocatalytic reaction were 91.4% and 92.9% for as-prepared TiO2 and P-25, respectively. © 2010 Elsevier B.V