A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science, School of Environment, Resources and Development

Thesis (M.Sc.) - Asian Institute of Technology, 1997

Batch experiments for heavy metal removal by adsorption using chitosan and desorption of adsorbed metal from chitosan were conducted. Adsorption and desorption isothermal results indicated that multilayer adsorption of heavy metal on chitosan took place. Both adsorption and desorption for copper and chromium are favorable whereas those of lead are also acceptable. 66%,45%and 47% desorption was observed for copper, chromium and lead. Kinetic studies verified that desorption occured within 24 hour. Effects of influencing parameters such as pH, particle size, temperature, agitation speed were investigated. The optimum pH values for adsorption on chitosan were 5.5,6 and 4, likewise, the optimum pH values for desorption were 2.41, 2.5 and 2.5 for Cu Cr and Pb respectively. The amount of Cu sorbed on 710 æm chitosan particles and 425 æm chitosan particles were 2 mg/g and 7 mW/g for the equilibrium concentration of 1 mg/L. The amount of Cu sorbed at 37.5 ° C and 50 C were 6.5 mg/g and 11 mg/g respectively for the equilibrium concentration of 0.5 mg/L. The amount of Cu sorbed at the agitation speed of 50 rpm and 250 rpm were 16 mg/g and 17 mg/g for the equilibrium concentration of 5 mg/L. In the case of desorption, when the initial Cu sorbed was 2.5 mg/g, Cu desorbed from 710 æm chitosan particles and 425 æm chitosan particles were 1.05 mg/g and 1.19 mg/g respectively. When the initial amount sorbed was 5 mg/g, Cu desorbed at 37.5 ° C and 50 °c were 3.5 mg/g and 4.5 mg/g. When the initial Cu sorbed was 17 mg/g, the amount of Cu desorbed at the agitation speed of 50 rpm and 250 rpm were 1.9 mg/g and 10 mg/g respectively. Similar trend was observed for Cr and Pb. Lower particle size, higher temperature and higher agitation speed enhanced both adsorption and desorption.