The behavior of small inorganic particles at the fiber/water interface has been analyzed from the kinetics and isotherms of adsorption of CaCO3 particles onto cationic fibers, The introduction of cationic moieties onto cellulosic fibers leads to a copolymer that can easily adsorb negatively charged particles, At equilibrium, the adsorption ratio of CaCO3 particles on a cationic copolymer of cellulose and poly(2-acryloxyethyltrimethylammonium chloride) is related closely to the particle size, the temperature, the agitation, and the ionic strength of the suspension. Kinetic models have shown that the weakly charged copolymers present a high-affinity-type kinetics when the CaCO3 particle average diameter is small (20 to 30 mu m). For an average particle diameter equal to 72 mu m, the kinetics corresponds to an adsorption with a lower affinity. The rate constants are 6.6 x 10(-12), 2.9 x 10(-12), and 1.2 x 10(-12) m(3)/s for particles with average diameters of 20, 30, and 72 mu m, respectively. We have also noted that the adsorption increases with agitation and reaches a plateau after 5 min. The ionic strength influences the electrostatic interactions between the positive sites of the graft and the anion of the adsorbate. Indeed a decreasing adsorption is observed when the ionic strength increases.