Organic modifier of poly-silicic-ferric coagulant: Characterization, treatment of dyeing wastewater and floc change during coagulation

► An organic modifier (PSFD) of poly-silicic-ferric (PSF) coagulant was prepared. ► The characterization and floc change of PSFD were also investigated. ► PSFD gave greater adsorption capacity and hydrolysis products size than PSF. ► The floc growth and settling velocity of PSFD were larger than those of PSF. ► The floc density of PSFD was greater than that of PSF.