Chitin was able to adsorb anionic silver-thiosulphate complexes at pH 2.2 within 5 min. The particle size affected adsorption capacity. The maximum adsorption capacity of chitin powder and flake was 4.37 and 3.61 mg Ag/g, respectively. A high concentration of thiosulphate had the strongest influence on silver-thiosulphate adsorption, because it could form stable-dissoluble silver complexes. The mechanism of silver adsorption was analysed from the effects of pH, contact time, agitation rate, thiosulphate concentration, adsorption isotherms and elution. Results indicated that the adsorption of silver-thiosulphate had two mechanisms: electrostatic interaction between protonated chitin and the anionic silver, and coordinate covalent bonding between lone pair electrons of nitrogen and/or oxygen and silver. Adsorbed silver was completely eluted by 3.0 M of sodium thiosulphate. The application of chitin for recovery of silver from photographic waste and the treatment of chitin to increase adsorption capacity, require further study. (C) 2003 Elsevier Ltd. All rights reserved.