Sorption isotherms and kinetics of Crystal Violet dye uptake from aqueous solution by using polyaniline nanocomposite as adsorbent

The ZnFe₂O₄-PANI nanocomposite has been developed as an adsorbent for the removal of Crystal Violet (CV) dye from aqueous solutions in the present study. The structural and functional characteristics of this material were systematically evaluated through various characterization techniques such as BET, FTIR and XRD. Fourier-transform infrared spectroscopy (FTIR) revealed significant vibrational bands associated with key functional groups that facilitate dye adsorption and confirmed the successful synthesis of the zinc-ferrite polyaniline nanocomposite, as evidenced by shifts in the peaks corresponding to ZnFe₂O₄ and PANi. The adsorption efficiency demonstrated a pH-dependent behaviour, increasing from 42 % at pH 3.0 to 88 % at pH 9.0, while a decline was observed above pH 9, attributed to electrostatic repulsion effects. The adsorption kinetics were effectively described by the pseudo-second-order model, with a maximum removal efficiency of 89 % achieved after a contact period of 60 mins. The analysis of the adsorption isotherm corroborated the applicability of the Langmuir model, indicative of a monolayer adsorption mechanism. Under optimal conditions (pH 9, 0.5 g of adsorbent in 50 ml of solution, and a 60-minute contact time), the ZnFe₂O₄-PANi nanocomposite exhibited endothermic and spontaneous adsorption characteristics. These findings suggest that this material possesses a high capacity and strong affinity for CV, thereby positioning it as a viable adsorbent for dye removal.