Enhanced adsorption of congo red from aqueous solution using chitosan/hematite nanocomposite hydrogel capsule fabricated via anionic surfactant gelation

In this study, chitosan/hematite nano-composite hydrogel capsules (HC-H) was developed via anionic surfactant gelation occurring simultaneously with immobilization and impregnation of α-Fe2O3 nanoparticles (HNPs) within the gel matrix. The nanocomposite adsorbent was characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), inductively coupled plasma optical emission spectrometry (ICP-OES), X-ray diffractometry (XRD) and elemental analyzer. The HC-H was successfully used for the removal of Congo red (CR) from aqueous solution. The CR adsorption isotherm data fitted to the non-linear forms of the Langmuir, Freundlich and Redlich–Peterson isotherm models indicated that both physisorption and chemisorption were essential in the overall adsorption process. The maximum Langmuir adsorption capacity of HC-H was 4705.6 mg/g (26.7 times more that of the pristine chitosan hydrogel capsule (176.5 mg/g)). The adsorption kinetics data were fitted with the non-linear forms of pseudo first-order and pseudo second-order and intraparticle diffusion models. The overall adsorption process was pH dependent. The HC-H represents a chitosan-based nano-composite adsorbent with stupendous affinity for CR dye molecules and thus, has huge prospect to be considered in wastewater treatment.