Removal of cadmium (II) and lead (II) from aqueous systems with pretreated fish bone waste by ethanol

Due to its availability in large quantities, fish bone waste was treated by ethanol and used as adsorbent for Cd (II) and Pb (II) removal from aqueous solutions. The removal efficiency of the heavy metal ions using ethanol-modified fish bone (EFB) was investigated as a function of dosage of adsorbent and pH. For Pb (II) and Cd (II) removal, the adsorbent optimum dosages were found to be 1.0 and 0.3 g·L^-1, respectively. The maximum adsorption capacities of Cd (II) and Pb (II) were achieved at pH 6.0 and were 33.05 and 32.67 mg·g^-1, respectively. The adsorption behavior could be described well by the pseudo-second-order model and the adsorption process was endothermic, as indicated by the increase of the pseudo-second-order rate constant with the temperature increasing to 40°C. The adsorption of the Cd (II) and Pb (II) on the EFB is the boundary layer adsorption with intra-particle diffusion. The adsorption isotherms were well fitted by Freundlich model, suggesting the multilayer adsorption for Cd (II) or Pb (II). The Cd (II) and Pb (II) removal process naturally presents chemical, indicated by the sorption energy, which was determined from Dubinin-Radushkevich isotherm. The adsorption process is spontaneous, favorable, endothermic and random, indicated by the thermodynamic equilibrium. With the use of a Scanning Electron Microscope (SEM), a large amount of Cd (II) and Pb (II) were seen as adsorbed on the surface of EFB. The maximum adsorption capacities of EFB were compared with other adsorbents reported. The results showed the possibility of utilizing natural wastes as lowcost and effective alternative absorbents to remove Cd (II) or Pb (II) from aqueous solutions.