Abstract
A series of polymerized ferric titanium coagulants (PFTC) with different basicity and Ti/Fe molar ratio were prepared, aiming to remove natural organic matters (NOM) as the main pollutants causing membrane fouling in water treatment process. The effects of basicity and Ti/Fe molar ratio on the structure of PFTC hydrolysates were preliminarily explored through the changes in peak intensity in Fourier transform infrared spectra and peak displacement in X-ray photoelectron spectroscopy spectra. The hydrolysis processes of Fe (III) and Ti (IV) were proposed based on hydrolysis polymerization curve and chemical distribution of PFTC. The coagulation results indicated that PFTC with low basicity and moderate Ti/Fe molar ratio could efficiently remove UV254, DOC and turbidity. When the amount of OH– or Ti (IV) was excessively high, the hydrolysates of PFTC transferred from oligomers to medium polymerized or colloidal species. PFTC could efficiently remove small hydrophilic substances through hydrogen bonding or sweeping effects of amorphous hydroxyl complexes, while PFTC with high basicity exhibited relatively low efficiency for UV254 and DOC removal. Finally, it was found that the control performance of PFTC on membrane fouling mainly depended on its efficiency in removing NOMs. This study will provide new insight into the development of composite coagulant and the precise control of membrane fouling.
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