Author(s)

P. Jassal, V. Raut

Abstract

The crab shell chitosan (CSC) and the medium molecular weight chitosan (MMWC) beads are cross-linked with ethylene glycol diglycidyl ether (EGDE) solution to get EGDE-CSC and EGDE-MMWC beads. The adsorption of CSC and MMWC beads at pH 2–4 show the adsorption of crystal violet (CV) was not significantly affected. Langmuir’ isotherm study provides an equilibrium parameter R_L, from the linear plots of C_e/X versus C_e for the adsorption of CV dye on MMWC beads and CSC beads. The adsorption is favourable if R_L lies within the range, i.e. 0<R_L<1. The TGA plots were performed on CV dye, and CV was absorbed on the MMWC powder, MMWC bead, and the EGDE-MMWC beads. Degradation takes place in two steps. The thermogravimetric analysis (TGA) of CV absorbed on MMWC, cross-linked with EGDE show that there is a decrease in the thermal stability of the cross-linked chitosans. Fourier Transform Infrared Spectrometer (FT-IR) gives a band at 1586 cm⁻¹ for –N(CH₃)₂ and aromatic ring stretching (-C=C-) clear band at 1363 cm.⁻¹ for CV. The IR of pure chitosan shows a broad band at 3433 cm⁻¹ due to –NH₂ stretching and –OH stretching at 1640 cm⁻¹ and the band between 720 and 590 cm⁻¹ shows –OH out-of-plane bend. The CV absorbed on CSC at different time intervals, MMWC powder, beads and 10–20% cross-linked EGDE-MMWC has also been studied.

Keywords

equilibrium parameter R_L, thermal stability, cross-linked chitosans, Langmuir’ isotherm