Synthesis of chitosan based semi-IPN hydrogels using epichlorohydrine as crosslinker to study the adsorption kinetics of Rhodamine B

The present study is focused on the preparation of chitosan (CS)/polyacrylonitrile (PAN) blend and semi-interpenetrating polymer network (sIPN) hydrogel films, and their application to the adsorption of Rhodamine B dye. The CS/PAN blend hydrogel films were prepared by solution casting technique. To prepare sIPN, CS was cross-linked with epichlorohydrin (ECH). The developed CS/PAN blends and sIPN hydrogels were characterized with field emission scanning electron microscope (FESEM) and Fourier transform infrared (FT-IR) spectroscope. The FESEM micrographs showed no phase separation between CS and PAN. The cross-linking of CS in the sIPN was confirmed by FT-IR. The degree of swelling, W-UB water content, and aqueous stabilities of the blends and sIPN hydrogels were examined at room temperature. Blend film (C8/P2) showed highest % degree of swelling (similar to 2,400%), increased % unbound water (W-UB) (52%), and fair degree of aqueous stability. The swelling of the blends decreased not only with an increase in PAN content but also with cross-linking. At the same CS and PAN composition (C8/P2), sIPN hydrogel exhibited a relatively low degree of swelling (similar to 245%), W-UB, and a high degree of aqueous stability. The potential of the optimized hydrogel film as an adsorbent was evaluated. The q(max) value for c-sIPN was much higher compared to C8/P2 blend film. The adsorption kinetics of Rhodamine B (RB) was observed to follow pseudo-second-order equation and the equilibrium adsorption obeyed Langmuir isotherm equation. The kinetics and adsorption isotherm indicated that the mechanism of adsorption is chemical. However, the FTIR spectra after adsorption showed hydrogen bonding.