Advances in coagulation/flocculation field: Al- and Fe-based composite coagulation reagents

Abstract

Currently, the research in the field of coagulation/flocculation process is focused on the synthesis of new composite coagulants, which are constituted of both inorganic and organic materials, so as to utilize within one reagent the advantages of both inorganic and organic components. Among possible organic additives, an anionic polymer can be used by introducing it into a pre-polymerised metal (i.e. Al or Fe) coagulant. In this study, a co-polymer of acrylamide and sodium acrylate is combined with two widely used Al or Fe based coagulants, i.e. polyaluminium chloride (PACl), and polyferric sulphate (PFS), thus producing novel composite coagulation reagents. The coagu¬lants were characterised in terms of typical physico-chemical properties, such as the degree of polymerisation, pH, conductivity, turbidity. Finally, coagulation experiments (jar-tests) enable the comparable assessment/evaluation of coagulants efficiency, when treating model kaolin-humic acid suspensions or pre-treated tannery wastewater.