Study On Species Distribution Of Aluminum And Properties Of Poly-Aluminum Silicate Chloride

AlCl₃, NaAlO₂ and Na₂SiO₃ have been used as raw materials to prepare the high-concentration(2.0mol/L) Poly-aluminum chloride (PAC) and Poly-aluminum silicate chloride (PASC) with different Si/Al molar ratio by feeding the alkali slowly.Compared with the reference sample PAC_ref(0.1mol/L), the PAC and PASC were studied by using many kinds of chemical analysis methods and modern analysis techniques.The polymer species distribution was studied by Ferron complexation timed spectrophotometry and ²⁷Al-NMR. The hydrolysis-polymerization process of aluminum in PASC solution was investigated by NaOH titration method. The interactions between silicate and hydrolyzed aluminum species were examined IR measurements. The Zeta electric potential and diameter distribution of PAC and PASC were measured by Zetasizer3000HS and MASTERSIZER 2000. And the change difference of forming and increasing of coagulant in the coagulation process of PAC and PASC were studied by transparency pulse examine technique. Finally, the flocculation efficiency of PASC with different preparation method and Si/Al molar ratio under different dosage were tested by jar tests..The experiment results show that: The high-concentration PASC can be prepared by feeding the alkali slowly under high-shearing force. 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. The structure and morphology of the polymer, the diameter distribution of the polymer, the electric potential 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 COD removal efficiency. Finally, the coagulation mechanism of PASC was summarized, which mainly contains charge neutralization and adsorption bridging mechanisms. In a word, high-concentration PASC is a novel, high-effectiveness, inorganic polymer coagulant.