Researches Of The Flocculability,Stability And Mechanism Of Polysilicate-metals Compound Flocculants

With the development of flocculants, polysilicate-metals flocculants (PSMS) have been a focus of research because of their higher stability than polysilicic acid's and higher coagulating properties than IPFs'. PSMS have been developed rapidly. Their property and general coagulation behavior have been extensively investigated. The differences between traditional coagulants and PSMS have been gradually examined. However, previous studies paid most attention to the preparation, characterization, and application of PSMS. Little study has been focused directly on their images and structures. There exist few established conclusions as to why their efficiency is superior to the tradition coagulants. It is generally thought that the pre-produced products contain species superior quality and possess structure fairly stable to further hydrolysis and solution chemistry, resulting in higher coagulation efficiency. The action and mechanism of PSMS are not fully understood. PSMS are actually clusters or aggregates of a combination of intermediate products with various anions, during hydrolysis of metal salts under suitable conditions. Hence, the study of their images and structures, would build the theoretical basis for Si-IPFs and their further improvement. Therefore, for improving the the stability of polysilicate-metals flocculants, discussing the coagulating mechanism of PSMS, extending the scale of polysilicate-metals flocculants, this thesis focuses on the following works.In this paper, to solve the stability of polysilicate-metals flocculants arising in the progress of commercialization, the effect of various factors, including the concentration of sodium ion in the industry water glass, kinds of acidifier, boron added, aluminum and iron ions introduced is observed respectively. The experimental results show that the stability of polysilicic acid is effected greatly by the pH value, and by reducing the concentration of sodium ion in pH value near neutral area and introducing acetic acid, B, Al and Fe, the stability of polysilicic acid can be enhanced. And then the stability of PSMS is improved. The stability of PFSS is little better than PASS.The coagulating properties were tested by jar tests using PASS and PFSS to treat wastewater, such as Yangzi river water, coking–plant wastewater and oil/water emulsion. Compared with inorganic polymer flocculants, polysilicate-metals flocculants(PSMS) are characterized by having higher turbidity removal, oil removal, better coagulating efficiency, broadly appropriate scope pH values, lower dosage. The the applied range of PSMS is not only in the field of drinking water treatment, but also in the field of wastewater.The flocculants are studied roundly by using many modern techniques. The interactions between polysilicic acid, aluminum ion, ferric ion and the hydrolysate of aluminum and iron are examined...