Study On The Coagulation Of The Stabilized Titanium Dioxide Nanoparticles Byaluminum Sulfate

TiO₂nanoparticles has been widely used in catalysis, cosmetics, coatings,electronics and pharmaceutical fields now. It must pollute the source water in theprocess of production, transport and use, posing the potential threats to people.Coagulation as the most frequently used method is effective to remove theparticulate pollutants in water. Therefore, the study were undertaken to explore theeffect of aluminum sulfate to remove TiO₂nanoparticles and the coagulationmechanism were discussed. The Nano-TiO₂adopted in this study is stabilized bytwo dispersions respectively for the mode of the nano-TiO₂in its application process.There are theoretical and practical significance for the study. In the first place, theunderstanding of the relevant colloidal flocculation theory is deepened. In thesecond place, the coagulation flocculation process of the nanoparticles in water isbetter understood.To get the best mode nano-TiO₂whose state is closest to the actual one, thenano-TiO₂was dispersed and characterized firstly. It became more stable then andthe dispersant was found to adsorp on the surface of nano-TiO₂. The average particlesize of the stabilized nano-TiO₂was508.4nm and228.2nm respectively.The effects of aluminum sulfate to remove the stabilized nano-TiO₂by thecoagulation and the coagulation mechanism was discussed under neutral, acidic,alkaline, high temperature and low temperature conditions. The influence of thetwo dispersants, pH value and water temperature on coagulation and mechanismwas also investigated. By the flocs dynamic monitoring, the analysis of the flocformation process under different conditions is studied at last. The result showedthat when the temperature was20℃under neutral and alkaline conditions, thenano-TiO₂could be removed by more than90percent by a certain amount ofaluminum sulfate; The law of different stabilized nano-TiO₂removal by aluminumsulfate was different; The removal of nano-TiO₂by aluminum sulfate was lesseffective under acidic conditions; when the temperature was high, the optimumdosage of aluminum sulfate extended in neutral, so it was conducive to remove thenano-TiO₂under the high temperature, and the impact of the dispersant was notobvious; Under the low temperature, there was a very small range of optimumdosage of aluminum sulfate, so it was not effective to remove the nano-TiO₂; Underthe neutral conditions, the polyelectrolyte dispersants could promote thecoagulation when aluminum sulfate was more than80mg/L, and the smallmolecule type dispersants impeded it. Under acidic conditions, the two dispersantshave played the role of promoting coagulation; when the pH was9.0, two kinds of dispersants can be appropriate to promote coagulation. When the pH is10.0, theeffect was not obvious; The polyelectrolyte dispersants slowed down the speed ofnano-TiO₂flocs, and the growth rate of nano-TiO₂was improved by the smallmolecule type dispersants.