Adsorption behaviour of Pb~(2+) in aqueous solution on bentonite modified by chitosan

A series of different molar ratio of bentonite modified by chitosan were prepared from bentonite using chitosan as modified agent.This paper studied the structure of them by means of scanning electron microscopy,infrared spectroscopy and X-ray diffraction.The results showed that the chitosan was adsorbed on the surface of bentonite to form a composite adsorbent.It was applied in treatment of Pb2+ in aqueous solution by a single factor affecting the adsorption experiments to determine the suitable reaction conditions.The results showed that when the initial concentration of Pb2+ is 20 mg/L,with the conditions of bentonite and chitosan quality ratio of 1︰0.01,reaction time was 45 min,pH was 5.5,adsorbent dosage was 1 g/L,the removal rate Pb2+ was over 90%.The removal ratio of using chitosan modified bentonite was higher than bentonite.At the same time,the equilibrium isotherms for adsorption were correlated to the Langmuir equation and Freundlich equation.The saturation adsorption capacity of bentonite modified by chitosan was almost unchanged after regeneration for several times.Through the calculation of the thermodynamic parameters △G,△H,△S values under different temperature,indicated that the adsorption process was a spontaneous endothermic process.