| In this work, a new type of inorganic polymer, poly-silicic-ferric (PSF) coagulant was prepared by co-polymerization. This paper inspected solid PSF, Si-Fe reaction mechanism, hydrolysis law, coagulation performance and coagulation dynamics by many experimental analysis ways such as jar test, X-ray diffraction (XRD), ultraviolet/visible absorption scanning (UV/VIS), transmission electron microscope (TEM), photon correlation spectra (PCS) and infrared spectrum (IR) and so on, and analyzed the mechanism of removing pollutants. This work probes the modification of PSF by adding KMnO4 to PSF to prepare solid-liquid poly-silicic-ferric (PSFN) coagulant. This research mainly conducts the following studies.The preparation of PSF includes the preparation of polysilicic acid (PS), the preparation of liquid PSF and the investigation of solid PSF. PS is one of the main materials for preparing PSF. The mathematical modeling on the preparation of PS is an important condition for preparing high quality PSF. PSF has better coagulation performance than the cooperation of Fe3+ and PS, or Fe2+ and PS and oxidant. PSF is a complexation compound of Si, Fe and many other ions, instead of a simple mixture of raw materials.The experiment inspected the surface morphology and coagulation performance of solid PSF solidified both under natural condition and at middle temperature. The results show that natural solidification can reduce the cost of PSF. Solidification after dilution favors the re-dissolution of PSF, and favors controlling the optimal species. The influence of reaction time on performance efficiency by liquid PSF is more evident than that by solid PSF. Reaction time needed in preparing solid PSF having excellent coagulation performance is shorter than that in liquid PSF, and.The experiment probed Si-Fe reaction mechanism and the optimal species by XRD, UV/VIS, TEM, PCS, IR, pH measurement and Ferron-Fe complexation timed spectrophtometric method, and studied the hydrolysis species distribution of PSF by both experiment and theoretical calculation for the first time. Different rection modes of Si-Fe in various Si/Fe molar ratios were proposed. The results show that the reacting rate, reaction mode and stability of bond between Si and Fe were different from various Si/Fe ratios; lower Si/Fe polymers with multi-branched structure based on Si-O-Fe-O-Fe-O-Si are may be formed, in which the formation rate of Fe-O-Fe bond is rapid and there is a mutual acceleration between Fe-O-Fe and Si-O-Fe bond. While higher Si/Fe ratio polymers with net-structure based on Si-O-Fe-O-Si-O-Si are may be formed, in which the formation rate of Si-O-Si is slow and there is a mutual retardation between Si-O-Fe and Si-O-Si bond. The stability of Fe-O-Fe bond is weaker than that of Si-O-Fe or Si-O-Si bond. The optimal reaction time of PSF reaching optimal coagulation species can be evaluated by measuring pH values during the polymerization process. Compared to multi-polymers of dissociate Fe3+ hydrolyzed, Fe bonded with Si reacts more quickly with Ferron reagent. PSF has stable species and does not hydrolyze easily. The dominant species of PSF are as follows: Fe(OH)2+ and Fe3+ at pH< 4; Fe(OH)3, Fe(OH)2+ and Fe3+ at pH from 5 to 9; Fe(OH)3 at pH>11.This paper investigated the coagulation efficiency of PSF in treating various waters, in comparison with that of polyferric sulfate (PFS) and polyferric aluminum (PFA), and analyzed coagulation mechanism. The results reveal that PSF has superior coagulant efficiency in treating near-neutral water samples with wider pH range to PSF and PFA. PSF is an oxidization coagulant and changes the molecular structure of organic matters (OMs, such as humid acid (HA) and so on), leading to the improvement of adsorption of OMs. Hydrolysis products (Fe(OH)2 and Fe3+) positively charged and large Si-Fe complexation polymer co-exist in solution over wide pH range (5 |
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