1,5 diphenyl carbazide immobilized cross-linked chitosan films: An integrated approach towards enhanced removal of Cr(VI)

Present study illustrates the significant enhancement in the adsorption capacity of glutaraldehyde cross-linked chitosan (C) films through immobilization of 1,5-diphenyl carbazide (D) towards Cr(VI). TGA studies reveal incorporation of about 11% D within the pores of the film while FESEM analysis further confirm thread like nature containing hydrophobic voids. Contact angle measurements suggest the appropriate balance of hydrophilic/hydrophobic nature of film through successive modifications with glutaraldehyde (G) and D. It is observed that Cr(VI) uptake by films is substantially improved by about 25% at pH 2 that follows pseudo first order kinetics with a rate constant value of 0.085 h(-1). Adsorption studies suggest that removal of Cr(VI) is a spontaneous process occurring mainly through pore diffusion process with removal capacity of 166 mg g(-1). XPS analysis of Cr(VI) treated C + G + D film indicate formation of Cr-D complex on the surface of film as well as presence of predominantly adsorbed Cr(III) species. It is interesting to note that there exists strong binding of Cr(III) with D present within the pores of film in a quantitative manner. Thus, it can be argued that incorporation of a selective chelating agent like D has substantial effect on removal efficiency of C + G + D for Cr(VI); an approach possessing potential applications in membrane technology. (C) 2017 Elsevier B.V. All rights reserved.