Polyethyleneimine (PEI) was first grafted on the surfaces of micro-sized silica gel particles in the manner of the coupling graft, forming the grafting particles PEI/SiO2. Afterward, for the grafted PEI, two polymer reactions, tertiary amination reaction and quaterisation, were allowed to be carried out in turn, and a kind of functional composite particles, QPEI/SiO2. was obtained. QPEI/SiO2 particles were used as solid adsorbent in the removal of chromate anions from aqueous solution. The static adsorption experiments (batch method) were performed, the effects of various factors on the adsorption capacity of QPEI/SiO2 were examined, and the dynamic desorption experiments were also carried out. The experimental results show that QPEI/SiO2 particles have strong adsorption ability for CrO42-ions by right of electrostatic interaction, and the saturated adsorption amount actually reach up to 0.14 g/g. The isothermal adsorption behaviour is fitted to Langmuir model. The adsorption ability of QPEI/SiO2 particles for CrO42- ions is affected greatly by the quaterisation degree of the grafted PEI macromolecules. The QPEI/SiO2 particles with higher quaterisation degrees have greater adsorption capacities. The adsorption ability of QPEI/SiO2 particles for CrO42- ions is nearly independent of pH values of the medium. QPEI/SiO2 particles have excellent eluting and regenerating property as a mixed solution of NaOH and NaCl is used as eluent. (C) 2009 Elsevier B.V. All rights reserved.