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 alpha-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), Xray 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.

Automated summary

The study developed chitosan/hematite nano-composite hydrogel capsules for the removal of Congo red dye, showing high Langmuir adsorption capacity and strong affinity for the dye molecules. The adsorption process involves both physisorption and chemisorption, with pH dependence and excellent potential for wastewater treatment.