Enhanced adsorption
of Congo red dye by CS/ZnO nanocomposite: Synthesis, characterization and performance
evaluation
Dhawan Monika, Yadav Sashi, Kumar Vineet, Bala Kiran and Chhikara Sunil Kumar
Res. J. Chem. Environ.; Vol. 29(11); 62-73;
doi: https://doi.org/10.25303/2911rjce062073; (2025)
Abstract
The need for effective and sustainable techniques to remove dye contamination from
various ecosystem has been identified by increasing concerns about environmental
pollution. This study synthesized novel zinc oxide nanocomposite derived from crab
shell (CS/ZnO). Field emission scanning electron microscopy (FE-SEM), Fourier transform
infrared spectroscopy (FTIR), X-ray diffraction (XRD) and Zeta potential were used
to characterize the nanocomposite structure. Batch adsorption studies were used
to determine the congo red (CR) adsorption effectiveness utilizing adsorbent dose,
contact duration, pH and temperature variables. The maximum adsorption capacity
(qmax) of 62.88 mg/g CS/ZnO composite was consistent with the Langmuir model based
on the data obtained for CR adsorption equilibrium. The kinetics study verified
that the pseudo 2nd order rate kinetic model was most effective and the qmax was
evaluated at pH 6.0 and 90 minutes.
Thermodynamic analysis exposed that the adsorption phenomenon was endothermic, spontaneous
and physical in nature. The protonation of the -NH2 groups in the CS/ZnO composite,
which increased its electro-positivity, is primarily responsible for the high adsorption
efficiency. The adsorption mechanism is controlled by the creation of hydrogen bonds
and electrostatic attraction between dye and nanocomposite. The CS/ZnO composite
may be regarded as an effective, advantageous and promising adsorbent for environmental
cleanup.
