The adsorption percentage of Cu(II) ions from aqueous solution in the absence and in the presence of different concentration of hydrochloric acid on rice straw (SIII) and its ash (R400) were studied in a modified batch adsorption technique. The kinetic data was analyzed using various kinetic models particularly pseudo-first-order, pseudo-second-order and intra-particle diffusion. The pseudo-second-order kinetic model was found to agree well with the experimental data. Thermodynamic parameters such as enthalpy (DH^°), free energy (DG^°) and entropy (DS^°) changes towards calculated and adsorption process was spontaneous at R400 in the absence and in the presence of 0.005 M HCl and exothermic in nature.