Preparation of New Type Poly-silicate Coagulant and Its Coagulation Property

A new poly-silicate coagulant named poly-aluminum-calcium-silicate sulfate coagulant (PACSS) was prepared to effectively eliminate suspended solids and organic matter in the wastewater. It was prepared by calcium carbide residue, sodium silicate, aluminum sulfate and sulfate as raw materials. The effects of silica acid activation pH, poly-condensation reaction time, mass fraction of SiO2, molar ratio of Al/Si and molar ratio of Ca/Si on the coagulant preparation were studied. The optimal preparation conditions of this coagulant are as follow: the silica acid activation pH is 2; the poly-condensation reaction time is 1 h; the mass fraction of SiO2 is 6%, the molar ratio of Al/Si is 0.8; the molar ratio of Ca/Si is 0.5 and the curing time is 6 h. The results indicate that the removal rates of turbidity and CODCr of wastewater can reach up to 96.2%, 84.3% respectively. PACSS coagulant has a better coagulation effect compared with aluminum (AS) and polymeric aluminum sulfate (PAC).