Humic acid (HA) is an ubiquitous substance in the earth environment and is very important regarding soil fertility. It has been shown that HA can be used as a depressant for hematite in iron ore flotation. However, its removal from water is important in many circumstances, because the treatment of the water with chlorine results in the formation of trihalomethanes that are carcinogenic products. In this work the precipitate flotation of HA was studied. The experiments were carried out with the use of cetyl trimethyl ammonium bromide (CTAB) and dodecylamine (DDA) as precipitant collectors. The mean diameter of the particles were determined by light scattering for both precipitates (HA/CTAB and HA/DDA). The electrophoretic mobility studies showed that the interaction HA/CTAB was much stronger than HA/DDA. The precipitate flotation experiments carried out in a column cell showed that over 90% of the HA can be removed from water without the additional use of any other reagents. (c) 2007 Elsevier Ltd. All rights reserved.