Adsorption and desorption studies of cadmium by cross-linked chitosan/κ- carrageenan

The binding efficiency of cross-linked chitosan/ κ-carrageenan for Cd2+ has been evaluated in order to consider its application to remediate cadmiumcontaminated water. Adsorption and desorption of cadmium by the chitosan bioadsorbent was investigated using batch experiments. The experiments were conducted in the definite concentration of modified chitosan (1.11 g L-1) with different cadmium concentrations (0- 1.97 mmol L-1 of cadmium) at pH 7.6 and ionic strength 8mmol L-1. In order to determine desorption of Cd, the modified chitosan loaded with cadmium ions was treated with 90 ml of 0.1M EDTA. The data were described by using Freundlich and Langmuir models. The values of the correlation coefficient (r2) and root mean square error (RMSE) were calculated for determining the best model. The correlation coefficients for the adsorption of Cd2+ in water system are 0.99 and 0.99; the RMSE are 4.42 and 6.83 for Freundlich and Langmuir equations, respectively. The correlation coefficients for the desorption of Cd2+ in this system are 0.99 and 0.97 and the RMSE are 0.93 and 3.47 for Freundlich and Langmuir equations, respectively. As shown, the adsorption and desorption data at the ranged of the Cd2+ concentration studied can be well described by the Freundlich model. The maximum adsorption capacity of Cd2+ onto the bioadsorbent was determined 750 μmol/g. the results indicate that the present bioadsorbent as a great adsorbent for Cd2+. But, it should be noted that the adsorbent cannot be reused for the cadmium adsorption easily due to its low amounts of cadmium desorption

Keywords:

Chitosan , κ-carrageenan , Cadmium , Langmuir , Freundlich