Preparation And Organic Modification Of Polyferric Sulfate And Polyferric Silicate Sulfate Flocculants

Coagulation is an effective technology for water treatment, and choice of coagulant is the key factor to improve treatment effects and reduce cost. Currently, more and more researches are focused on the synthesis of composite coagulations, which are constituted of both inorganic coagulants and organic coagulants. In this paper, the inorganic-organic synthesis of inorganic polymer coagulant-Polymeric ferric sulfate was investigated, including the inorganic-inorganic composite coagulants and inorganic-organic composite coagulants, by comparing synthesis through blending and copolymerization. This paper presented the study of synthesis theory of inorganic polymer coagulant the synthesis of inorganic-inorganic composite coagulant and the synthesis of inorganic-organic composite coagulant and the test of its performance.Firstly, the optimum condition of coagulant preparation was investigated, by comparing the preparation methods of polyferric sulfate. Method that ferric sulfate alkaline polymerizing polyferric sulfate (APFS) and orthogonal analyzing its balance of effect factors, with the single factor tests, got the optimum condition of APFS, operation temperature20℃, ageing temperature20℃and ageing4hour. Method that preparing polyferric sulfate (OPFS) by oxidizing ferrous sulfate and orthogonal analyzing its balance of effect factors, with the single factor tests, got the optimum condition of the synthesis, operation temperature20℃, ageing temperature20℃and ageing6hour. Under the optimum condition, two kinds of poly ferric sulfate were synthesized. What was more, by infrared spectrum, X-ray diffraction and scanning electron microscope analyzing its structure and valence-bond, results show that two kinds of polyferric sulfate had same valence-bond and different structure. By testing its distribution of polymeric ferric with the method of timed complexation spectroscopy of ferron, results shown that the structures of polymeric ferric in two inorganic polymer coagulants are different. Besides that, the coagulation experiments of high turbid water show that, OPFS has superior capacity to remove turbidity.Secondly, the modification of polysilicate to APFS was investigated. The balance of effect factors of blending method between polysilicate and APFS was measured by orthogonal analysis, which shows the optimum synthesis condition of polyferric silicate sulfate (APFSSm) silicate ageing1hour at45℃, APFSSm ageing2hour at45℃. Blending polysilicate and ferric sulfate, the polyferric silicate sulfate (APFSSc) was polymerized by alkaline process. The balance of effect factors was determined by orthogonal analysis and the optimum synthesis condition was determined by single factor tests, silicate ageing1hour at45℃, APFSSc ageing2.5hour at50℃. IR spectrum, XRD and SEM were used to characterize that APFSSm and APFSSc have same valence-bond composition and different valence-bond structure. Thus, APFSSm and APFSSc are two kinds of polymer coagulants that have different structure. The compositions of polymeric ferric and polymeric silicon were determined by timed complexation spectroscopy of ferron method and Mo-Si method, and then their capacity of turbidity removal and stability were compared. Result shows that two coagulants have optimum performance when the ratio of ferric to silicon is1and basicity is0.1.Thirdly, the modification of polysilicate to OPFS was investigated. The optimum synthesis conditions of copolymerization and blending were determined by orthogonal analysis, silicate ageing1hour at50℃,OPFSSm ageing2hour at50℃. What is more, the optimum synthesis condition of OPFSSc was refined by single factor tests, silicate ageing2hour at45℃, OPFSSc ageing2.5hour at40℃. By characterizing their structure, result shows two coagulations, OPFSSm and OPFSSc, have different structure. The experiments of determining optimum ratio of ferric to silicon and basicity show that, OPFSSm has superior stability and OPFSSc has superior coagulating performance.Fourthly, the composite experiment of macromolecular substance to PFS was investigated. By the modification of organic polymer coagulant-aid to OPFS and APFS, result shows only non-ionic polyacrylamide can composite with PFS. The performance detection and structural characterization of OPFS-PAM and APFS-PAM with various ratios show that, APFS-PAM has a major development respect to turbidity removal performance and OPFS-PAM has a major development respect to COD removal.Finally, the composite modification of macromolecular substance to PFSS was investigated. By the modification of organic coagulant-aid with various ratios to APFSS and OPFSS (Fe:Si=1; B=0.1), results show that OPFSS-PAM has a major development respect to coagulating performance and stability, only when non-ionic polyacrylamide within specific range was composited with PFSS and formed uniform solution. The modification of organic macromolecular substance to inorganic coagulant was achieved. Furthermore, the coagulant that both coagulating performance and stability are superior was obtained. These all make a contribution to related researches.