Microwave induced beta-cyclodextrin modification of chitosan for lead sorption

Microwave induced copolymerization of beta-cyclodextrin (beta-CD) and chitosan (Ch) resulted in copolymer Ch-g-beta-CD synthesized without any radical initiator or catalyst. Copolymer samples of different performances in terms of Pb(II) binding were synthesized by changing beta-CD concentration at fixed microwave power and exposure time. To understand the advantage of using microwaves in the adsorbent synthesis, the copolymer synthesized using a K2S2O8/ascorbic acid redox pair at identical beta-CD and Chitosan concentrations (% G 103) was also evaluated as Pb(II) sorbent, and the results obtained were compared with that of microwave synthesized copolymer. A representative sample of microwave synthesized adsorbent was characterized using FTIR spectroscopy, X-ray diffraction, TGA, SEM analysis and using this sample adsorption of lead (II) was studied as a function of pH, initial Pb(II) concentration. The adsorption data followed both Freundlich and Langmuir isotherms. On the basis of the Langmuir model, Q(max) was calculated to be 434.78 mg/g for microwave synthesized copolymer (Ch-g-beta-CD) in comparison to 294.11 mg/g for conventionally synthesized copolymer (Ch-g-beta-CD). In order to investigate dynamic behaviour of Ch-g-beta-CD as an adsorbent, the kinetic data were modelled using pseudo-second-order and second-order. The regeneration experiments revealed that the Ch-g-beta-CD can be successfully reused for seven cycles. (C) 2010 Elsevier B.V. All rights reserved.