The plant powder of Kammoni (L. Solanum nigrum) were activated with sulphuric acid and used as low cost easily available and renewable biological adsorbent for the removal of acid dyes (acid blue, acid red and malachite green) from aqueous solution. Batch experiments were carried out for adsorption kinetics and isotherms. Operating variable studied were pH, temperature, adsorbent dose, initial concentration of adsorbate. Adsorption capacity seems to be enhanced by increasing temperature, adsorbent dose and for pH. Maximum dye adsorption was found to be in acidic range. Kammoni leaf powder (KLP) treated with Sulphuric acid (H2SO4) solution increased the adsorption efficiency upto 80 percent. Equilibrium data represented by the Freundlich Langmuir isotherm model for all adsorption systems. Beside these the thermodynamic study has showed that the acid dye adsorption onto the surface of acid activated Kammoni leaf powder (KLP) was physical adsorption and the process was spontaneous and exothermic