Characterization and coagulation performance of poly-silicic-ferric sulfate and its oxidizing modification coagulant

Key words:  poly-silicic-ferric sulfate  oxidizing modification  characterization  coagulation performance  ooagulatiai mechanism

Abstract:

A new type of inorganic coagulant，oxidizing pdy-silicic-ferric sulfate(PSF-I), was pr^ared by adding potassium permanganate and stabilizer M to poly-silicic-ferric sulfate (PSF). The micrcproperties of PSF-I was characterized with microsocpe, txansmissicai electroi miaDSOOpe(TEM) , ultraviolet/visible absorpticai(UVA.) scanning, alkalizaticai experiment, infrared(IR) spectrcmeter and oxidation-reducticai potential (ORP) meter, respectively, in comparison with that of PSF. The coagulaticn performance of PSF-I in treating different water was investigated cxxnpared to that of PSF. The results show that the species of PSF is characterized by having multi-branched structures with lai-ger size, wider mcJecular wdght and larger fractal dimension. While PSF~I is a kind of brown-yellow oonglanerate of larger size with lower fractal dimension and almost the similar size of ^ecies. The ORP of PSF-I is higher 550 mV than that of PSF. The micrc^ioperties of PSF have been changed greatly due to the additicxi of KMrOj，and there exists KMn04 unattached in PSF-I. A kind of tetrahedral structure sanewhat like the omnecticxi of Si-O-Si bends may be formed by the oorr^)lexation of Mn (maybe in various valence) with PSF. The ooagulaticxi effect has the same trend for various water by PSF-I and PSF. PSF-I has lower turbidity removal than PSF at lower dosage while the removal rate of UV254 by PSF-I is higher than that by PSF at entire dosage range with the largest difference of 17%. The removal of dissolved organic matters (DOMs) is caused not oily by adsorption/charge-neutralization and co-precipitation but also by oxidizaticn using PSF-工 as coagulant, in which catalysis/oxidizaticxi is dominant. While to PSF, adsorption/charge-neutralization and a>precipitation is the only coagulation mechanism, so there is an essential distincticai in mechanism for removing DOMs by PSF and PSF-I.