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Using conventional coagulant, low turbidity water is difficult to achieve standard. This research uses aluminum chloride, titanium tetrachloride, and sodium silicate as raw materials for the preparation of polyaluminum titanium silicate chloride (PATC). PATC is used to treat low turbidity. The synthetic PATC showed the best coagulating effect in treated water under the following experimental conditions: Reaction temperature of 50 °C, and n(Ti)/n(Al), n(-OH)/n(Ti+Al), and n(Si)/n(Ti+Al) were 0.3, 0.2, and 1.0, respectively. The species distribution and the transformation of PATC showed that the interaction between titanium tetrachloride, sodium silicate, and the hydrolysate of Al influenced the morphology distribution of Al. Temperature and -OH greatly affected the distribution of Alb in PATC. The analysis of infrared spectra and X-ray diffraction indicated that both titanium tetrachloride and sodium silicate had complex chemical reactions with aluminum chloride. Si-O-Ti and Si-O-Al produced by the reaction affected the PATC treatment of low-turbidity water. Scanning electron microscopy showed, that compared with polyaluminum chloride(PAC), the PATC cluster was more compact, showed greater pore structure, and presented better flocculation precipitation. The optimal reaction conditions were an initial turbidity of 10 nephelometric turbidity unit(NTU), PATC dosage of 9 mg/L, pH of 8 for the simulated water sample, stirring speed of 50 r/min, and settling time of 50 min, which were determined by Orthogonal experiment. The zeta potential of the reaction process was analyzed. In the treatment of low-turbidity water, PATC mainly functioned by adsorbing, bridging, and sweeping flocculation. Electrical neutralization played an auxiliary role.
Liao et al. (Sat,) studied this question.