Studies On Preparation And Application Of Poly Silicate-Sulfate Aluminum Magnesium Composite Flocculant

This paper prepared the poly silicate-sulfate aluminum magnesium (PSAM for short) by using aluminum sulfate, magnesium sulfate, sodium silicate, sodium hydroxide as raw materials. The paper studied the influencing factors of M/Si molar rate, Al/Mg molar rate, Si content, basicity, aging time and flocculation condition by investigating the removing rate of chroma. The Al-ferron complex timed colormetric method was applied to research the appearance and distribute regulation of aluminum in PSAM; Using the X-ray diffraction analytical method to study the interaction among the polysilicate, aluminum salt, magnesium salt and their hydrolysates. Taking direct sky blue 5B simulated dye wastewater, printing and dying wastewater from Nanchang Huayuan dying and finishing limited company, domestic sewage from East China Jiaotong University as processing objects, the coagulation performance of PSAM was analyzed by coagulation and agitation test. Compared with conventional flocculants such as PAC,AS, magnesium sulfate, investigated the superiority of PSAM in treating the turbitiy, chroma and CODcr of printing and dying wastewater and domestic sewage. Probed into the flocculant mechanism of PSAM. Finally, analyzed the economic and social benefits of PSAM.The research results showed as follows: the M/Si molar rate, Al/Mg molar rate, Si content, basicity, aging time and flocculation condition had some effects to the flocculating property. When M/Si=1/1, Al/Mg=3/1, nSiO2=0.36mol/L, B=0.5, aging time=2d, PSAM had best treatment effect on direct sky blue 5B simulated dye wastewater, the decolouring ratio is 93.12%. Polysilicate, aluminum salt, magnesium salt and their hydrolysates had a certain extent of complexation. This complexation had some influences to the structure and morphology of PSAM, hydrolyticpolymerization process of aluminum salt and magnesium salt, hydrolyzate form of distribution of Al(III). Compared with other conventional flocculants ,coagulation and agitation test showed that PSAM had better removal capacity of turbitiy, chroma and CODcr in wastewater, especially in printing and dying wastewater, turbidity removal ratio can reach 88.99%, the decolouring ratio can reach 84.64%,CODcr removal ratio can reach 68.77%. The scope of application of PH is wide(7~11).According to the classical coagulation theory, the article discussed the coagulating principle of PSAM, it was considered that PSAM depended on the combined action of the electricity neutralization and adsorption birdging to flocculate the colloid. PSAM was a safe, effective inorganic polymer flocculants.