The removal of heavy metals from aqueous solution using fish bones

In this study, the adsorption and removal of copper, chromium, cobalt, nickel, cadmium and lead ions from aqueous solutions were investigated using fish bones which are of natural origin, cost-effective and industrial by-product waste. Pretreated fish bones obtained from engraulis European anchovy (Engraulis encrasicolus, L., 1758), European pilchard (Sardine pilchardus, W., 1792), bogue (Boops boops, L., 1758), bluefish (Pomatomus saltatrix, L., 1766) and gilthead seabream (Sparus aurata, L., 1758) were used for the adsorption and removal of metal ions. In order to remove fatty acids and other contaminants, the fish bones were pretreated with nitric acid, sodium hydroxide, hexane, alcohol, hydrogen peroxide and water. The removal efficiency of fish bones were investigated as a function of pH, contact time, initial metal concentration, temperature, cleaning process, fish species, mixing rate and adsorbent dose. The maximum adsorption capacity of Cu+2, Cr+3, Co+2, Ni+2, Cd+2 and Pb+2 was 150.7, 114.6, 83.7, 58.8, 131.6 and 323.6 mg/g, respectively at optimum conditions (P<0.05). The kinetic results of adsorption obeyed a pseudo second-order model. Copper, cobalt, nickel, cadmium and lead adsorption fitted the Langmuir isotherm, while chromium adsorption fitted the Freundlich adsorption isotherms. Thermodynamic parameters such as Ea, ?G, ?H and ?S were calculated to determine the feasibility of the adsorption mechanism. ?H value was found to be positive indicating that the adsorption mechanism of all metals was endothermic. Weber-Morris and Urano-Tachikawa diffusion models were also applied to the experimental equilibrium data. It was concluded that fish bones can be effectively used as a sorbent for the removal of heavy metals from aqueous solutions.