Preparation,Characterization And Coagulation Behavior Of Polyferric Magnesium Silicate (PFMSi) Coagulant

Coagulation is a processing technique in treating the wastewater.In comparison with traditional metal salts,inorganic polymeric coagulants are most commonly used in water treatment due to its superior coagulation efficiency and high resistance to breakage.The preparation and application of coagulant are studied extensively all the time.Currently,research is focused on the development of composite inorganic-organic coagulants with the advantages of both inorganic and organic coagulants to improve the characterization of coagulation.The polysilicate coagulant is prepared by bringing metal salts into polysilicic acid,which has the advantages of simple preparation method,abundant raw materials and low costs.Additionally,it is a kind of new and efficient inorganic polymer coagulant,which contains the mechanisms of charge-neutralization,adsorption-bridging and sweeping.In this paper,the polyferric magnesium silicate(PFMSi)is prepared by the method of co-polymerization with the materials of water glass,FeSO4,MgSO4,NaClO3,NaHCO3,concentrated sulfuric acid and so on.The preparation conditions of molar ratio of metal ion and silicon(M/Si),basicity(OH/)and aging time(T)are researched.Meanwhile,the structure and morphology are analyzed by X-ray diffraction,FT-InfraRed spectra and scanning electron microscopy microphotographs.Finally,the coagulation performance of PFMSi and conventional coagulants are compared by treating the raw water and the simulation of printing and dyeing wastewater.The followings are the main conclusions:(1)The single factor experiment shows that the best preparation conditions of PFMSi are Fe/Si = 1:1,Mg/Si = 1:2,OH/M = 0.35,T = 4d,in this case,the coagulant is more stable.And the removal rates of turbidity and UV254 are 98.4% and 58.5%,which are higher than the conditional coagulants.(2)The result of Fe-Ferron complexation timed spectrophotometry shows that the monomeric iron compounds possesses the maximum content in the Fe species distribution,the appropriate basicity(OH/M)can improve the content of colloidal iron compounds and the stability of coagulant.The results of X-ray diffraction indicate that PFMSi is a kind of amorphous material;the result of FT-InfraRed spectra shows that PFMSi contains the bonds of Si-O-Fe and Si-OH-Mg.(3)PFMSi shows better coagulation performance than the conventional coagulants in treating the raw water and the simulation of dyeing wastewater,in terms of turbidity,UV254,TOC,chromaticity and COD.With the measurement of flocculation index(FI)and Zeta potential value,the coagulation mechanisms of PFMSi are explored,contain charge-neutralization,adsorption-bridging and sweeping.In conclusion,PFMSi is a type of new and efficient coagulant.