The Determination of Active Site, Capacity, Energy and Rate Constant on the Adsorption of Zn(II) and Cd(II) on Chitin

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Active sites, capacity, energy, and rate constant on the adsorption of Zn (II) and Cd (II) on chitin isolated through deproteination followed by demineralization processes of crab (Portunus pelagicus Linn) shell have been investigated. The chitin possessed acetamide functional group that was suggested to exist in two different chemical forms of NHC (O) CH3 and NHC (OH) =CH2. It means that one hydrogen ion in CH3 in the acetamide can be conjugated to oxygen carbonyl to form C-OH. The active site responsible for the adsorption of Zn (II) and Cd (II) would be nitrogen on the acetamide functional group. The adsorption dataa for both metal ions were fit quite well with the Langmuir isotherm model, resulting the adsorption capacities of 3.2×10-4 and 2.8×10-4 molg-1 for Zn (II) and Cd (II), respectively, and adsorption energies of 15.1 kJ mol-1 for Zn (II) and 17.9 kJ mol-1 for Cd (II) . It was also revealed that Zn (II) was adsorbed slightly faster than Cd (II) with first order adsorption rate constants of 2.7×10-3 min-1 for Zn (II) and 2.6×10-3 miri-1 for Cd (II) .
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