Defluorination behaviors using different types of aluminum salts: The effect of SO42–
2021
Wang, Bin | Huo, Lixin | Wang, Dongsheng
In order to explore the effect of SO₄²– in natural water on the defluorination behaviors of different types of aluminum salts, a coagulation experiment by simulating raw water in the laboratory was conducted. After jar tests, the aluminum forms in supernatant were analyzed by ESI-TOF-MS, and the precipitation was characterized by solid-state NMR and XPS. The results show that when AlCl₃ is used as a coagulant, as the rise of SO₄²– content, the production of Al(OH)₃ is almost unaffected. In addition, AlCl₃ can be hydrolyzed to form a small amount of polyaluminum species, and they also have a defluorination function. When these polyaluminum species encounter SO₄²–, they react with it to generate Al-SO₄ co-precipitation, which reduces the content of Al-F complex and hinders the defluorination. When Al₁₃ is used as the coagulant, the low content of SO₄²– enhances the attack of F⁻ on Al₁₃, and reacts with a large number of Al-F complexes to produce Al-SO₄ co-precipitation, releasing F–, and rapidly decreasing the defluorination rate. The high content of SO₄²– reacts weakly with Al-F complex. As its content rises, the defluorination rate slowly decreases.
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