[Utilizing fly ash to prepare polysilicon acid and compounded PFS and the study of its properties]

Fly ash which is a kind of solid waste of power station in Dalian was prepared as polysilicon acid, and compound polymerized ferric sulphate and its properties was studied. Fly ash was dipped in NaOH solution. The effects of temperature, concentration of NaOH solution and reactive time were examined respectively on the conversion efficiencies of silicon. Then the solution which was rich in silicon was used to compound polymerized ferric sulfate (PFS) and got compounded polymerized ferric sulphate (F-PFS), and evaluated the effects of slaking time and Fe3+/Si molar ratio on conversion efficiencies of silicon. Then used Na2SiO3 to prepare polysilicon acid compounded polymerized ferric sulphate (N-PFS) with the same silicon concentration at the best condition. The best ratio of dissolved silicon 0.207 9 g x g(-1) was attained at the condition of 4 mol x L(-1) NaOH solution, 120 degrees C for 4 h. The coagulant was attained at the condition of Fe3+/Si molar ratio of 1:0.2 and slaking time of 2 h. The reducing turbidity by F-PFS is the same as N-PFS, but F-PFS is better than N-PFS and PFS is in the stabilization, sedimentation,and the property of treating with urban sewage.