| Recent studies found that heavy metals water accumulation in water intensifies and heavy metal pollution is becoming more and more serious with a large number of electroplating,metallurgy industries wastewater diacharging.Heavy metal pollution of water bodies,was designated as the first class pollutants.How to remove heavy metal in the water has become a major issue in the current field of environmental protection.Oxidation,adsorption and other appropriate processing method can treat that waster water which contains a large quantity of heavy metal complex ions and chelate content.Chitosan-?-cyclodextrinpolymer(CTS-CD),a kind of natural polymer,was synthesized by immobilizing-?-cyclodextrin(?-CD)onto the molecular structure of chiosan by the cross-linking function of glutar-aldehyde.The adsorption on properties of heavy metal complex ions on CTS-CD in water were invertigated.The adsorption mechanism and adsorbent regenerative and recycling were discussed.The infrared spectroscopy analysis(by the potassium bromide tablet method)results of prepared CTS-CD showed that,?-cyclodextrin has been successfully crosslinked to the chitosan chains.SEM and X-ray diffraction analysis of chitosan and prepared CTS-CD showed that,?-cyclodextrin has crosslinked to the chitosan molecule chains,increasing the surface area greatly.Thus,the adsorption capacity of CTS-CD significantly increased.The adsorption properties of chromate and cadmium on CTS-CD in water were investigared.The experiments showed that the solution pH significantly influenced the adsorption capacity,and the adsorption capacity got the maximum when pH value of 5.At 318 K,pH of 5,the equilibrium capacity of chromate and cadmium on CTS-CD were 104 mg/g?121 mg/g after 5 h.The adsorption rate and adsorption capacity increased with temperature,and raising temperature was beneficial for this adsorption reaction.The adsorption process could be modeled by pseudo second-order kinetics very well.The apparent activation energy of chromate and cadmium adsorption by CTS-CD were 32.291 kJ/mol?1.206 kJ/mol.The adsorption pattern fitted Langmuir isotherms well.The experiments indicated that ?H of chromate and cadmium were all above zero,and ?S of them were above zero too.At 288 K ~ 318 K,?G of the adsorption processes were below zero.The adsorption rate constant increased with temperature,and the adsorption pattern fitted Langmuir isotherms,which was monomolecular layer absorption.The regeneration and recycle of CTS-CD was studied to increase the utilization ratio.At room temperature,0.5 mol/L sodium hydroxide was used for CTS-CD's desorption,and 0.2 mol/L hydrochloric acid solution was uesd for activating treatment,then the regenerated CTS-CD was reused to adsorb chloro-acetic acids.The adsorption capacity of CTS-CD can still reach more than 90% of maxima.Owing to favorable regenerated and recycling ability,CTS-CD has a broad prospect of application.In this paper,the only nature of the cationic chitosan and widely used in industrial production of ?-cyclodextrin were used as raw materials for synthesis of CTS-CD,overcoming the weakness of chitosan recycling,introducing of the ?-cyclodextrin envelope in order to increase the adsorption capacity of pollutants,and CTS-CD regeneration and recycling performance is good.As a further study of CTS-CD,it will play more important role in the field of water pollution control. |
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