Study on the Adsorption of Mixed Cd(II) and Pb(II) Ions by N,O-Carboxymethyl-Chitosan

The N,O-carboxymethyl-chitosan (N,O-CMC) was used to investigate the adsorptions of two metals of Cd(Ⅱ) and Pb(Ⅱ) ions in an mixed aqueous solution. The effects on adsorption capacities such as pH value, temperature, adsorbent dose and initial metal ion concentrations were investigated, and the dialysis method was applied to separate the materials after adsorption. The results revealed that the better adsorption of N,O-CMC for Cd(Ⅱ) and Pb(Ⅱ) ions at the pH 7-8; the effect of temperature on the adsorption was not significant; the absorption of Cd(Ⅱ) and Pb(Ⅱ) ions was enhanced with the increase of N,O-CMC amount; the adsorption capacity increasesed with the addition of the concentration of initial metal ions in the aqueous phase. The adsorption of Pb(Ⅱ) ion in Cd-Pb mixed solution on the N,O-CMC was well followed as the Langmuir isotherm equation under the concentration range studied, and Cd(Ⅱ) ion was corresponding to Langmuir adsorption equation in 100-200 mg/L and 200-500 mg/L, respectively. Conclusion: N,O-CMC was suitable for adsorbent to removal Cd(Ⅱ) and Pb(Ⅱ) ions, but it can selectively adsorption ions from the mixed solution, the adsorption capacity (Qm) for two metal ions was as follows: Pb(Ⅱ) > Cd(Ⅱ).