Sulfuric acid treated biopolymers (STB) were prepared from a lignocellulosic-based agricultural byproduct. The STB has been used as an effective adsorbent in a batch experiment for the removal of methyl parathion (MP) from aqueous solution. The as-prepared STB has been characterized by using surface area analyzer, scanning electron microscope (SEM), elemental analyzer, and proximate analysis methods. A batch adsorption study was carried out to investigate the adsorption equilibrium, kinetics, and thermodynamics as a function of agitation time, initial concentration of MP, initial pH, temperature, and carbon dose. Adsorption data were used to perform the kinetic models. The adsorption data was found to obey the Langmuir adsorption isotherm. Thermodynamic parameters of the adsorption process ΔG, ΔS, and ΔH were calculated, and their negative values indicate the feasible exothermic and spontaneous nature of the process. The diffusion of the MP molecule onto the biopolymer was confirmed by using the Weber–Morris equation. Reichenberg's equation shows the film diffusion of MP.