title: Coagulation of humic acid by ferric chloride in saline (marine) water conditions.
abstract: The coagulation of a model seawater-humic acid solution with a hydrolysis metal salt (FeCl3) has been studied by monitoring floc size, solution pH, and zeta potential. The kinetic features of the orthokinetic coagulation have been demonstrated in relation to coagulant dosages, solution pH and zeta potential. Humic acid removal and floc charge reduction increased with coagulant dosage. Adjusting the solution pH prior to coagulation had a substantial effect on the treatment performance. By pH adjustment to pH 6, the greatest humic acid removal (by coagulation and subsequent membrane filtration) and the largest floc size was achieved at a FeCl3 dosage of 200 micromol l(-1). It is believed that the coagulation is characterised by competition between OH- ions and humic acid for ferric ions in the co-precipitation process. In acidic pH, where the concentration of OH- ions is low, humic acid molecules may compete more favourably for bonding sites in the co-precipitation, which leads to a more compact precipitation and a higher overall humic acid removal.
authors.affiliation: Ian Wark Research Institute, University of South Australia, Mawson Lakes, South Australia 5095, Australia.
authors.forename: J
authors.initials: J
authors.lastname: Duan
authors.forename: N J D
authors.initials: NJ
authors.lastname: Graham
authors.forename: F
authors.initials: F
authors.lastname: Wilson
mesh_terms: D011232:Chemical Precipitation; D002712:Chlorides; D005290:Ferric Compounds / Q000737:chemistry*; D005374:Filtration; D006812:Humic Substances / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D018508:Water Purification / Q000379:methods*
chemical_list: D002712:Chlorides; D005290:Ferric Compounds; D006812:Humic Substances; C024555:ferric chloride