Dispersion-regulated, entropy-controlled synthesis of polytitanium coagulants for advanced water treatment

Polytitanium coagulants have significant potential for water treatment owing to their superior floc settleability, biocompatibility, and sludge recyclability. However, the industrial application of these coagulants is limited by the uncontrolled hydrolysis and polymerization of highly reactive precursors. To address this challenge, this study presents a dispersion-regulated, entropy-controlled synthesis strategy. In this approach, TiCl₄ was dispersed in an inert solvent to increase system entropy, which reduced both the thermodynamic driving force and kinetic rate of hydrolysis. The subsequent controlled addition of H₂O and acetylacetone (AcAc) enabled precise regulation of the hydrolysis-polymerization process. The resulting coagulant, dispersion-polymerized titanium coordinated with AcAc (DPTC-AcAc) outperformed conventional TiCl₄ and pre-hydrolyzed polytitanium chloride (PTC). Mechanistically, AcAc coordination enabled DPTC-AcAc to form hydrolysis products with a narrow size distribution (100 kDa-0.22 μm) and extended network-like structures. Compared with PTC, DPTC-AcAc demonstrated a 179 % higher surface charge density, an increased isoelectric point (4.50 vs. 5.14), a 258 % faster floc growth rate, and a 127 % larger floc size. These properties synergistically enhanced charge neutralization capacity and sweeping flocculation efficiency. In lead-laden industrial wastewater treatment, DPTC-AcAc outperformed conventional polyaluminum chloride and polyferric sulfate in both efficacy and stability. This study provides a sustainable approach for the industrial-scale production of polytitanium coagulants and enables their practical application.