The nonylphenol (NP) biosorption and desorption potential for fungal biomass used under batch conditions was investigated using kinetics and isotherm models. Fungal biomass of Rhizopus arrhizus TISTR 3610 exhibited preferential uptake of NP, an endocrine disrupting chemicals. Sporangiospores, asexual spores, were immobilised in chitosan beads. The biosorption data of NP on the moist heat inactivated R. arrhizus-chitosan beads were analyzed using four popular adsorption isotherms and, by using non-linear least-regression with the solver add-in in Microsoft Excel, correlated in order with the Fritz-Schluender > Redlich-Peterson > Freundlich > Langmuir isotherms. The pseudo first-order kinetics was found to have the best fit with the experimental data. The diffusivity of NP in the R. arrhizus-chitosan beads was calculated using the shrinking core model, and the diffusivity values were in the ranges of 2.3736 x 10(-4)-1.8950 x 10(-4) cm(2) s(-1). Desorption to recover the adsorbed NP from the beads was performed in methanol and was best described using a pseudo second-order kinetic model (C) 2009 Elsevier Ltd. All rights reserved