Hydrolysis and coagulation behavior of polyferric sulfate and ferric sulfate

摘要

The hydrolysis behaviors of polyferric sulfate (PFS) and ferric sulfate (FS) under conditions similarnto raw wastewater were investigated and the coagulation of biologically pretreated molassesnwastewater using PFS and FS was evaluated by studying coagulation efficiency, zeta potentialnand microscopic surface morphology of flocs. Experimental results show that the hydrolysisnbehavior of PFS is different from that of FS on the basis of ferron assay. In the case of FS, fast-nreacting Fe(III) polymers were the dominant polynuclear species while large fraction of slow-nreacting iron polymers is present in PFS. Despite slightly fewer dosages of PFS required asncompared to FS, there is no marked difference in the coagulation of molasses effluent betweennPFS and FS, especially at the optimum dosages. Both coagulants destabilize organic compoundsnpredominantly through charge neutralization-precipitation mechanism. Hydrolysis rate of PFS innsynthetic solution is appreciably different from that in raw wastewater. This may due to the effectnof sulfate anion introduced as counter-ion as well as depolymerization of larger polymeric Fe(III)nspecies by the organic ligands present in molasses effluent.