| The release of large quantities of cadmium into the aquatic environment can be deleterious to human health as well as to environments. The method for remove the cadmium from the water is getting more and more attention. Removal of heavy metal by agricultural waste produced from water is a promising approach. Sugarcane bagasse is a kind of agricultural waste produced by sugar industry. The annual yield of sugarcane bagasse is great and most of them are abandoned. There is the adsorption capacity of heavy metals by sugarcane bagasse. The adsorption capacity of heavy metals by sugarcane bagasse could be improve through modification treatment.In this study, sugarcane bagasse was modified by ethanol and sodium hydroxide solution to produce adsorbent which had a good performance of Cd2+adsorption. Then the surface morphology characterization of unmodified and modified sugarcane bagasse could be obtained by used scanning electron microscope, infrared spectrometer and X-ray diffraction.The effect of different experimental conditions on the adsorption of Cd2+by modified sugarcane bagasse was investigated. The adsorption isotherms and thermodynamics, kinetics on the adsorption of Cd2+by modified sugarcane bagasse had been analyzed. The results show:(1) Many cracks and large number of cellulose appeared on the surface of modified sugarcane bagasse. The specific surface area of modified sugarcane bagasse was increased. The lattice structure of sugarcane bagasse was destroyed after modified. Hydrogen bonding structure was destroyed and the hydroxyl activity was increased. Those phenomena on the modified sugarcane bagasse made an enhancement of Cd2+adsorption capacity for the adsorbent.(2) The optimum pH was ranged from 4 to 6, the adsorption equilibrium time was 20 minutes, The maximum removal of cadmium (II) metal ions was observed at pH 6 with initial metal ions concentration of 20 mg-L"1 with an adsorbent dose of 8 g·L-1 of the test solution. The maximum removal capacity of modified sugarcane bagasse was 98.26%. The removal of cadmium (Ⅱ) metal ions by modified sugarcane bagasse increased with the initial metal ions concentration increase and reduced with the temperature increase. The coexistence cations (Ca2+, Mg2+and Na+) affected the adsorption of Cd2+in the follow the order:Na+< Ca2+ < Mg2+(3) The result for simulation of isotherm shows that the adsorption rate was controlled by chemical adsorption and the maximum adsorption capacities of Cd2+was 14.450 mg·g-1. The adsorption kinetic data followed a pseudo-second order model. The thermodynamic results show that the adsorption of cadmium (Ⅱ) by modified sugarcane bagasse was spontaneous and exothermic. |
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