Characterization And Flocculation Performance Evaluation Of Polyaluminum Chlorides Hydro-Thermal Synthesized At 150℃

In this thesis, according to a large number of hydrothermal synthesis experiments and chemical analytical data, the solid-liquid equilibrium diagram of AlCl₃-Al₂O₃-H₂O at 150℃was drawn firstly by means of wet dregs. From which five hydrolysates of aluminum were identified. Under the guidance of the phase diagram, these five polyaluminum chloride crystals were prepared. They were Al₂₄O₁₁(OH)₄₄Cl₆, AlOOH, Al₁₇O₁₆(OH)₁₆Cl₃, AlCl₃·4Al(OH)₃·7.5H₂O and AlCl₃·4Al(OH)₃·4H₂O with the purity of 90.92%, 97.51%, 78.21, 92.65% and 61.25% respectively.These polyaluminum hydrochlorides products, if purified, could be used for their structure determination, from which the law of their formations and transformations in the hydrolysis process of aluminum salts could be explored.Al₂₄O₁₁(OH)₄₄Cl₆ with such high polymerization degree as 24 was synthesized firstly at home. It was confirmed that the ultimate hydrolysis product boehmite (AlOOH) could be prepared using aluminum powder, AlCl₃·6H₂O and water or poly aluminum compounds and water as raw materials at the suitable ratio, aging temperature and aging time. The well-crystallized boehmite with high-purity was a needle-like and porous cluster. Furthermore, the preparation of boehmite with hydrothermal synthesis method had not been reported in literatures.Flocculation performance of Al₂₄O₁₁(OH)₄₄Cl₆ was evaluated using Kaolin suspending solution as simulated water sample. The results showed that Al₂₄O₁₁(OH)₄₄Cl₆ possessed flocculating property under weak acidic, neutral or alkaline conditions. Particularly, its flocculation performance under alkaline and neutral conditions was excellent. For example, the residual turbidity could reached zero at the dosage of 10^-3.07 mol[Al]/L. Thus, Al₂₄O₁₁(OH)₄₄Cl₆ would be used as an excellent flocculant.This thesis enriched the content of polyaluminum structure and its perperties, established the connection between them, and opened up new routes for the preparation of the boehmite that was used frequently in some fields such as catalytic field.