Batch sorption experiments were performed to remove an anionic dye, acid blue, from it aqueous solutions using chemically modified barley straw. The chemical modification was performed using a cationic surfactant hexadecylpyridinium chloride monohydrate (CPC) to enhance its adsorptive performance. The characterization study performed using C and N analysis and FTIR confirm the impregnation of CPC on the modified barley straw. A preliminary experiment which was conducted found that the unmodified barley straw did not give any measurable dye removal when compared to the modified straw. For the modified straw, batch experiments were carried out as a function of contact time, Initial dye concentration and adsorbent dosage. The equilibrium isotherm models such as Langmuir and Freundlich were used to evaluate the equilibrium data.