The Effect Of The Presence Of SO₄～(2-) And/or SiO₃～(2-) On Polyaluminum Properties And Flocculation Efficiency

The influence of SO₄^2- and /or SiO₃^2- on Al (III) properties and flocculation efficiency is explored in this paper. Meanwhile, Al (III) species calculation, interactions of SO₄^2- and/or SiO₃^2- with Al (III) species, surface morphology, hydrolysis and flocculation dynamic of Polyaluminum flocculants containing SO₄^2- and /or SiO₃^2- are investigated. The main research and conclusions are as follows:1. A new Al-Ferron kinetics method was developed to monitor and calculate Al speciation. The results showed that the Al-Ferron kinetics fit a binary pseudo 1st order rate equation. Sulfate and silicate had different influences on Al-Ferron kinetics. Al-Ferron complexation timed spectrophotometry is the commonly used method of determining Al speciation but this new Al-Ferron kinetics calculation method shows different species distributions. For all the flocculants except polyaluminum silicate chloride (PASiC), the new method yielded higher Alb and lower Al_a values. The Al (III) chemical species calculated using Al-Ferron kinetics is more consistent with the Al-Ferron reaction results and ²⁷Al NMR results.2. The results of Al (III) speciation calculated using Al-Ferron kinetics and ²⁷A1 NMR method showed, on one hand , that the presence of SO₄^2- and /or SiO₃^2- inhibited forming Al_b/or Al₁₃ species during polyaluminum prehydrolysis. And this effect of the presence of SO₄^2- was more obvious than that of SiO₃^2- On the other hand, the inhibition of SO₄^2- and SiO₃^2-on Al_b/or Al₁₃ formation was in different direction. SO₄^2- tended to aggregate and form larger polymers while SiO₃^2- tended to disaggregate and form smaller polymers.