Artocarpus altilis (breadfruit) skin as a potential low-cost biosorbent for the removal of crystal violet dye: equilibrium, thermodynamics and kinetics studies

Artocarpus altilis (Breadfruit) skin shows great potential as an effective low-cost biosorbent for the removal of toxic crystal violet (CV) dye. Curve fitting of adsorption equilibrium data obtained under optimized conditions, followed by error analysis, for different isotherms, namely Langmuir, Freundlich, Temkin, Dubinin–Radushkevich, Redlich–Peterson, and Sips, demonstrates that the Langmuir and the Sips adsorption isotherm models show the best agreement with maximum biosorption capacities (q _max) of 145.8 and 150.1 mg g⁻¹, respectively, which are superior to most reported biosorbents. Breadfruit skin, whose point of zero charge is at pH 4.7, characterized by X-ray fluorescence (XRF) spectroscopy, scanning electron microscopy (SEM) and Fourier transform infra red (FTIR) spectroscopy before and after treatment of CV provides further support for adsorption. Thermodynamic studies indicate that the adsorption of CV by BS was both spontaneous and endothermic, while kinetics studies show that the sorption of CV on BS follows the pseudo-second-order kinetics with a contribution from intraparticle diffusion.