Adsorption of [meso-tetrakis(4-sulfonatophenyl)porphyrinato]oxovanadate(IV)(4-), [VO(tpps)], onto chitosan 7B in aqueous solution was investigated in a batch system. The effects of solution pH, initial concentration of [VO(tpps)], and temperature were studied. Adsorption kinetic data obtained from different batch experiments was modeled using both pseudo first- and second-order kinetic equations. Freundlich, Tempkin, and Langmuir models were used for the description of adsorption equilibrium data. The best results were achieved with the pseudo second-order kinetic and Langmuir isotherm equilibrium models, respectively. The equilibrium adsorption capacity (q (e)) increased with increasing the initial concentration of [VO(tpps)], showing maximum adsorption capacity of 441.21 mu mol/g. The activation energy (E (a)) of sorption kinetics was estimated to be 19.84 kJ/mol in the temperature range 25-40 A degrees C. Thermodynamic parameters such as changes in free energy (Delta G), enthalpy (Delta H), and entropy (Delta S) were also evaluated by applying the Van't Hoff equation. The values of thermodynamic parameters of [VO(tpps)] adsorption onto chitosan 7B indicate its spontaneous and endothermic nature. The present work provides a first example for the preparation of chitosan-[VO(tpps)] complex in aqueous solution.