ADSORPTION OF CADMIUM (II) BY CHITIN

Abstract

The feasibility of using chitin as an adsorbent for cadmium (II) was examined. The adsorption characteristics were studied as a function of solution pH, temperature, contact time et. al., Maximum uptake amount of cadmium (II) was estimated to 93.9 mg/g·chitin by saturated capacity method at pH 5.41 in the HAc-NaAc system. The isotherm data for cadmium (II) at pH 5.41 fitted well to a Langmuir equation with a sorption capacity of 94.3 mg/g·chitin which was in accordance with the maximum uptake amount by means of the saturation method. The apparent adsorption rate constant was k₂₈₈K = 3.34×10⁻⁵s⁻¹, k298K = 4.60×10⁻⁵s⁻¹, k308K = 6.35×10⁻⁵s⁻¹ and k318K = 9.89×10⁻⁵s⁻¹. The apparent activation energy was 63.1 kJ/mol. Thermodynamic parameters, ΔG₂₉₈K was calculated to be -19.5 kJ/mol, ΔH and ΔS were found to be 10.6 kJ/mol and 101 J/mol·K, respectively. Adsorption mechanism was also proposed using infrared spectroscopy technique(IR).