A spongy, porous nano calcium oxide (NC) with point zero charge of 11.80 was synthesized using the shell of a Gastropod (Achatina achatina) via the sol-gel technique. The ability of the NC to adsorb Cr (VI) from aqueous solution was assessed systematically in a batch process via isothermal, kinetic, and variable process optimization procedure. The sorption data had the best fitting for the Langmuir isotherm model and the monolayer sorption capacity (q(m), mg/g) value of 125 mg/g was obtained. The initial solution pH had no palpable effect on the monolayer sorption capacity. The amount of sorbed Cr (VI) increased with contact time and initial Cr (VI) concentration and attained equilibrium within 120 min. The fitting of the different kinetic models to the sorption data, by error analysis, using the linear coefficient determinations (r(2)) and the Chi-square statistical analysis (chi(2)), showed that the mechanism of the sorption process is better described by the pseudo second order kinetic model. Thermodynamic evaluation showed that the sorption process was spontaneous (Delta G degrees: -15.27; -14.87 and -14.45 kJ/mol at 303, 313, and 333 degrees C, respectively), exothermic (Delta H-0 = -22.568 kJ/mol) and increased disorder (Delta S-0 = 0.0244) appeared on the NC-solution interface. during the adsorption process.