Characterization and phosphorus removal of poly-silicic-ferric coagulant

An inorganic polymer, poly-silicic-ferric (PSF) coagulant was prepared by co-polymerization, and the hydrolysis products distribution of PSF was calculated from the pH changes during the hydrolysis process of PSF. The characterization of PSF and total phosphorus (TP) removal by PSF were studied in comparison with that of poly-ferric aluminum (PFA). The results revealed that PSF has more than 30% TP removal than PFA. The optimal metal/phosphorus molar ratio of TP removal by PSF is from 0.6 to 1.2 for the synthetic water and from 1 to 2 for the sewage water, respectively. PSF has higher TP removal at both neutral and higher pH sides from 7 to 12 for the synthetic water and from 7 to 13 for the sewage water, in comparison with PFA which has much higher pH side from 11 to 12 for the synthetic water and from 11 to 13 for the sewage water, respectively. PSF mainly removes TP by complexation or adsorption, in which FePO4 precipitation contributes a little.