Acid formaldehyde pretreated chestnut shell was as adsorbent and the influence of initial cation concentration, temperature and pH was investigated to optimize Pb2+, Cu2+ and Zn2+ removal from aqueous solutions [189]. The maximum adsorption capacity was obtained as 8.5 mg/g for Pb2+ ions and the order of cation affinity was Pb2+ > Cu2+ > Zn2+. The sorption of Cu(II) onto chestnut shell in a batch adsorber has been studied [190]. The adsorption capacity of chestnut shell for Cu(II) was found to be 12.56 mg/g at 293 K. The kinetic data were found to follow the pseudo-second-order model.