Rice bran, an agricultural by-product, was used for the removal of zinc ions from aqueous solution. The work considered the determination of zinc-biomass equilibrium data in batch system. These studies were carried out in order to determine some operational parameters of zinc sorption such as the time required for the Zinc-biosorbent equilibrium, the effects of biomass particle size, pH, and temperature. The results showed that pH has an importance effect on zinc biosorption capacity. The biosorbent size also affects the zinc biosorption capacity. The sorption process follows pseudo-second-order kinetics. The intraparticle diffusion may be the rate-controlling step involved in the adsorption zinc ions onto the rice bran up to 30 min. The equilibrium data could be best fitted by the Langmuir sorption isotherm equation over the entire concentration range (40-160 mg/dm 3 ). Thermodynamic parameters, such as Delta G degrees, Delta H degrees, Delta S degrees, have been calculated. The thermodynamics of zinc ion/rice bran system indicate spontaneous and endothermic nature of the process.