Abstract
The first establishment of the 35 Cl qNMR method was achieved in this study. The calibration curves showed that extremely high linearity was established over a wide chloride concentration range from 1.0 × 10 −3 to 3.6 mol L −1 . The various Al hydrolysis products were detected nondestructively by 27Al qNMR, and their concentrations were determined. The K-Al 13 was not detected in the solutions containing a large amount of SO 4 2− ions, and K-Al 13 was observed at pH 3–6. The K-Al 13 concentration reached a local maximum when the aging time was approximately one day to one week. The highly charged K-Al 13 (i.e., 7 + ) and DLVO theory revealed an efficient coagulation mechanism for the model sludge. The aggregation rate of the PACS-0.15 model sludge containing SO 4 2− ions with an SO 4 2− /Al molar ratio of approximately 10% was high over a wide Al concentration range owing to the formation of large flocs. If the model sludge water contains excess SO 4 2− ions, the SO 4 2− ions contribute minimally to the growth of large flocs of model sludge, hence, the model sludge did not aggregate efficiently. • Hydrolysis reaction of Al polynuclear complex was investigated by 27 Al and 35 Cl qNMR. • 35 Cl qNMR was essentially established for the first time in this study. • Keggin complex was not confirmed in the solution contain a large amount of SO 4 2− ion. • Keggin complex was formed very slowly from colloidal polynuclear Al oligomer. • 10 mol% SO 4 2− ion accelerates the growth of large flocs.
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