Natural polysaccharides such as starch, dextrin, guar gum, cellulose and th
eir derivatives are promising non-toxic organic depressants. Although gener
ally perceived as non-selective, these polymers have found use in commercia
l processes or have been tested in laboratories in practically all flotatio
n systems involving every type of minerals. In this communication, the adso
rption mechanisms of natural polysaccharides are reviewed, with the objecti
ve of promoting the wider applications of the polymers. While it seems gene
rally accepted that natural polysaccharides interact with minerals via surf
ace metal-hydroxylated species, an acid/base interaction model between the
natural polysaccharides and mineral surfaces is proposed to explain many ob
served adsorption and flotation phenomena. (C) 2000 Elsevier Science B.V. A
ll rights reserved.