Chitosan hydrogel beads impregnated with hexadecylamine for improved reactive blue 4 adsorption

•Chitosan beads impregnated with hexadecylamine (HDA) were prepared.•The impregnated chitosan beads are successfully applied to remove reactive blue 4.•Various models and isotherms were employed to describe the adsorption process.•The adsorption capacity of impregnated chitosan beads was 1.43 times higher.

Adsorption performance of chitosan (CS) hydrogel beads was investigated after impregnation of CS with hexadecylamine (HDA) as a cationic surfactant, for the elimination of reactive blue 4 (RB4) from wastewater. The CS/HDA beads formed with 3.8% HDA were the most effective adsorbent. The adsorption capacity was increased by 1.43 times from 317 mg/g (CS) to 454 mg/g (CS/HDA). The RB4 removal increased with decrease in the pH of dye solution from 4 to 9. The isotherm data obtained from RB4 adsorption on CS and CS/HDA are adequately described by Freundlich model (R2 = 0.946 and 0.934, χ2 = 22.414 and 64.761). The kinetic study revealed that the pseudo-second-order rate model (R2 = 0.996 and 0.997) was in better agreement with the experimental data. The negative values of ΔG° (−2.28 and −6.30 kJ/mol) and ΔH° (−172.18 and −101.62 kJ/mol) for CS beads and HDA modified CS beads, respectively; suggested a spontaneous and exothermic process for RB4 adsorption.