Preparation and Evaluation of Titanium-Based Xerogel as a Promising Coagulant for Water/Wastewater Treatment

The nontoxicity of titanium (Ti) and the potential to produce valuable photocatalysts from the final coagulated sludge constitute the main advantages of Ti-based coagulants over conventional ones. However, the low effluent pH and the too-fast hydrolysis limit the wide application of Ti-salt coagulants. Prehydrolysis, to some extent, is helpful to improve the coagulation performance of Ti-salt coagulants. However, the prehydrolyzed polytitanium chloride (PTC) still suffers from narrow applicable dose/pH range. A novel and efficient Ti-based coagulant, denoted as titanium xerogel coagulant (TXC), was successfully prepared by the sol–gel method with TiCl4 as the precursor and acetylacetone as a modifying agent. Compared with TiCl4, a PTC, and a commercial polyferric sulfate, the resulting TXC possessed a larger floc size, better settling property, and wider applicable coagulant dose/pH range. Moreover, the effluent pH after TXC coagulation was not significantly reduced, avoiding the corrosion problem sometim...