| The process of congulation is an efficient pretreatment technology,which has been widely applied in the treatment of water and wastwater,and the development of floccuant's preparation and application is also very rapid at home and abroad. The overall development direction is from low molecular weight to high molecular weight and from simple to complex. Aluminum and iron salts of inorganic polymer flocculant are the most widely used flocculants in recent years, but there are still some shortcomings in application. In order to further improve its performance, aluminum-based and iron-based composite flocculants are given more and more attention. The polysilicate flocculant is prepared by bringing metal salts into polysilicic acid, which plays the role of charge neutralization,bridge and adsorption. and it is a new type of highly efficient inorganic polymer flocculants in the field of water treatment.In this paper, preparation conditions of PFMS is studied,and its physico-chemical properties is also discussed with instrumental analysis and chemical analysis methods. The main findings are as follows:1.The poly ferric magnesium silicate is first prepared by copolymerization in this thesis,using sodium silicate,ferric sulfate and magnesium suifate as raw materials. The flocculation efficiency and stability are influenced by the Si/M molar rate,n(SiO2), Fe/Mg molar rate and OH/M molar rate. And the physicochemical characteristics of the PFMS were studied by using many optical methods and modern chemical techniques.2.Fe-Ferron time by time complexation colorimetry method is used to classify the species distribution of Fe(III); 3.The interaction among the polysilicate acid, Mg(â…¡) ,Fe (â…¢) and its hydrolyzate is analysed by using Infrared Spectroscopy and X-ray diffraction; the macrostructure characteristics of PFMS is studied by transmission electronic microscope;the coagulation performance of PFMS is analyzed by coagulation-mixing experiments,4.Using dyeing wastewater as the object, the coagulation performance of PFMS is analyzed by coagulation-mixing experiments,and some advantages of PFMS are ascertained for the removal of colority, COD through the comparative experiments between PFMS, PAC, PFS and PFSS, the flocculation mechanism is also discussed:Through this research, the main conclusions are as follows:1.The results of flocculation and stability test of PFMS show that the stability of flocculant increases with increasing n(SiO2),Si/M molar rate,Fe/Mg molar rate and OH/M molar rate,that the flocculation efficiency increases with increasing n(SiO2), first increase and then decrease with the increase in alkali, remain good flocculation efficiency with Si / M ratio at 0.5 ~ 2 or Fe / Mg ratio at 0.25 ~ 2.2.Results of Fe-Ferron time by time complexation colorimetry show that the species distribution of Fe(III) is greatly influenced by OH/M molar rate,Si/M molar rate and aging time,in PFMS, the Fe(a) quantity is the most, that is the iron mainly existence in the form of free ion and the single nucleus hydroxyl/silicic acid complex compound, so suitable OH/M molar rate, Si/M molar rate and aging time can enhance the content of the polynuclear hydroxyl complex compound, reduces the content of single nucleus hydroxyl complex compound , in order to improve the abilities of charge neutralization,absorption-bridging, netting.and sweep function.3.X-ray diffraction analysis showes that the flocculant is not a simple blend, but Fe3+, SO42-and polysilicate forme amorphous polymer.4.The Infrared spectroscopy results show that there must be complexation between polysilicic acid and iron as well as its hydrolyzate.5.SEM analysis shows that the surface structure of polysilicic acid is changed by Fe3+,Mg2+ adding,and it is strongly influenced by Si/M and OH/M molar rate.6.Decolorization of wastewater experiments show that the performance of the PFMS is better than PFS, PFSS and the PAC in general, the removal efficiency of COD is also better than the above flocculants, and the treated wastewater can meet the required pH value (6 ~ 9).
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