Modeling the Effect of Temperature on Adsorption of Lead(II) and Zinc(II) onto Goethite at Constant pH

摘要: Abstract The influence of temperature and adsorbate concentration on the sorption Zn(II) Pb(II) by goethite was studied at fixed pH. Proton stoichiometry, measured direct titration, found to depend identity metal ion, pH, temperature. For proton stoichiometry ranged from 1.55 pH 6.5 10°C 1.95 7.5 70°C, while for 5.50 value varied 1.05 1.4 70°C. Three adsorption models—the Langmuir two-site model, surface precipitation model Farley, Dzombak, Morel (FDM), BET model—were applied data, fitted parameters were used determine enthalpy entropy adsorption. Although models assume rather different reactions, therefore generate correspondingly equilibrium constants, estimated enthalpies all positive, between 4 30 kJ/mol. There also fair agreement various estimates capacities. However, yield very entropies adsorption, these being positive (and generally in range 100 160 J K −1 mol ) but negative (in −80 −160 FDM model.