Pore structure and metal adsorption ability of chitosans prepared from fishery wastes

The degree of deacetylation, molar mass, and the yield of chitosans prepared from four fishery wastes (shrimp shell, lobster shell, crab shell, and cuttlebone) under the same conditions were compared. The adsorption capacities and rates of Cu(II), Ni(II), and Cd(II) from water on chitosans were measured at 30 °C. It was shown that the equilibrium isotherms of Cu(II) could be fitted by the Langmuir equation and those of Ni(II) and Cd(II) by the Freundlich equation. The rates of adsorption, analyzed by a plot of amount of adsorption vs. the square root of time, indicated different controlling mechanisms. The differences in metal adsorption among the four types of chitosans could be generally interpreted by their different pore structures such as pore size distribution and pore diameter.