Pac And Polymer-si-al-coagulant High Al_b Content

AlCl₃, Na₂CO₃, NaHCO₃, Ca(AlO₂), Na₂SiO₃ and HCl have been used as raw materials to prepare Poly-aluminum chloride(PAC) containing high proportion Al_b by a novel Solid-Solid preparation process, and to prepare Poly-aluminum silicate chloride(PASC) by adding active silicate into PAC. A series of PAC and PASC, which has different basicity (B) and Si/Al molar ratio, was studied. The method of Solid-Solid preparation to produce high proportion Al_b has been studied. The aging process is inspected carefully. Then the PAC and PASC were studied by using many kinds of chemical analysis methods and modern techniques. The structure and morphology of PAC and PASC were studied by Transmission Electron Microscope (TEM). The electrokinetic properties and diameter distribution of PAC and PASC were measured by Zetasizer3000HS. And the polymer species distribution was studied by Ferron complexation timed spectrophotometry and ²⁷Al-NMR. The interactions between silicate and hydrolysate of aluminum were examined by IR. Finally, the coagulating properties of PASC with different B and Si/Al molar ratio under different dosage were tested by jar tests, including turbidity removal and color removal.The experiment results show that: Solid-Solid preparation can easily and efficiently produces PAC with high Al_b proportion. There are interactions between silicate acid and the hydrolysate of aluminum in PASC, which can affect the hydrolysis-polymerization process of aluminum in PASC solution, and the interactions are mainly affected by the Si/Al molar ratio and B. The structure and morphology of the polymer, the diameter distribution of the polymer, the electrokinetic property of the PASC also were affected by the Si/Al molar ratio. Compared with PAC under the same preparation condition, PASC is characterized by having higher turbidity and color removal efficiency. Finally, the coagulation mechanism of PASC was summarized, which mainly contains charge neutralization and adsorption bridging mechanisms. In a word, PASC with high Al_b concentration is a novel, high-effectiveness, inorganic polymer coagulant.