Rice straw contains large amounts of cellulose, hemi-cellulose,lignin and silica. Those compounds provide binding sites for metals. Therefore, rice straw should be a good candidate for the scale-up treatment of wastewater containing Cd pollutant. In the present study, the biosorption of Cd2+ by unmodified rice straw was systematically studied, using a combination of mathematical modeling, ion-exchange experiments and infrared (IR) spectroscopy