Enhanced adsorption of Congo red dye by CS/ZnO nanocomposite: Synthesis, characterization and performance evaluation

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.