Synthesis of biopolymer chitosan-based hydrogels with and without a crosslinker for the removal of industrial dye procion blue HERD: a comparative study

ABSTRACT The current study reports the preparation and application of bio-based polymer composite hydrogel with and without a crosslinker for the removal of industrial dye procion blue HERD (PB). Biopolymer chitosan, acrylic acid as a monomer and potassium persulphate (K2S2O8) as an initiator synthesise composite hydrogel. The crosslinked composite hydrogel is synthesised by the microwave irradiation technique using thiourea (CH4N2S) as a crosslinker. Chitosan-based hydrogel synthesised without crosslinker (CH) and with crosslinker thiourea (CH-T) is analysed using techniques, such as Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), differential thermal analysis (DTG) and derivative thermogravimetric analysis (DTA). The adsorption capacity of CH and CH-T for the removal of PB from an aqueous solution is investigated. The removal efficiency of hydrogel is 90% in a solution of pH 7 for a constant dose of PB (5 mg L−1). The experimental data attained for the adsorption of industrial dye (PB) onto CH and CH-T showed a perfect fit for Freundlich and Langmuir isotherms. The perfect fit of experimental data for PB decolorisation is observed for pseudo-second-order kinetic equation with k values 10.17 × 10−3 mg−1 min−1 and 6.719 × 10−3 mg−1 min−1 with CH and CH-T, respectively. GRAPHICAL ABSTRACT