Synthesis of graphene oxide-modified porous chitosan cross-linked polyaniline composite for static and dynamic removal of Cr(VI).

A novel ternary composite was synthesized comprising graphene oxide-modified porous chitosan cross-linked polyaniline (GO@CS-PANI) by improved Hummers method, followed by cross-linking and grafting. The morphological, structural, and electrical properties of the composite were characterized by FESEM, BET, XRD, RAMAN, FTIR spectra, and zeta potential. It was found that the composite shows excellent Cr(VI) removal performance both in static and dynamic adsorption. The optimal adsorption parameters were solution at pH of 2.0, adsorbent dosage of 0.4 g/L, time of 45 min, and temperature of 35 °C. The Langmuir isotherm model was the best-fitted model, indicating homogeneous adsorption with maximum uptake of 539.83 mg/g. Pseudo-second-order was the best-fitted kinetic model, and the rate was controlled by film diffusion. Thermodynamic data demonstrated that the process was spontaneous, endothermic, and feasible. From the dynamic study, it was witnessed that a lower flow rate and a higher bed height were suitable for maximum adsorption performance. The Thomas model was the best-fitted model for data obtained from the dynamic study. Competition from interfering ions showed that anions have little effect on Cr(VI) removal, whereas cations have no such effect. The adsorption mechanism involved electrostatic attraction, π-π interaction, ion exchange, and metal ion complexion. After five cycles of adsorption-desorption study, the composite still removed 76% Cr(VI). These findings of the present study and the reusable nature of GO@CS-PANI composite signify the innovative and excellent adsorbent for wastewater treatment.