A study on the removal of prednisone from aqueous solutions by adsorption onto a vegetal activated carbon.

This study evaluated the prednisone removal from aqueous solutions using adsorption by an activated carbon of vegetal origin (VAC). A central composite rotatable design (CCRD) and the response surface methodology (RSM) were used to verify the influence of the parameters: pH, adsorbent dose and prednisone concentration in a batch adsorption process. Among the analyzed parameters, only the adsorbent dose and the prednisone concentration were statistically significant (α = 0.05) and the critical values obtained were adsorbent dose: 1.87 g/L, pH 7.56 and prednisone concentration: 3.66 mg/L with 77.51% of prednisone removal by VAC. The kinetic study of the adsorption of prednisone reached the equilibrium in 4 h. The pseudo-first-order model described adequately the kinetics data behavior. The equilibrium experimental data obtained at different temperatures showed that the VAC has a maximum adsorption capacity of 18.04 mg/g at a temperature of 30 °C. The prednisone removal decreased by the increasing temperature and the Langmuir isotherm well described the experimental data (R² > 0.98). Thermodynamic results shown that the prednisone removal of aqueous solutions by VAC is spontaneous and favorable process.