Development of response surface methodology for optimization of phenol and p -chlorophenol adsorption on magnetic recoverable carbon

The powdered activated carbon impregnated with Fe3O4 magnetic nanoparticles (MNPs) was synthesized by a facile in situ chemical co-precipitation method. The response surface methodology (RSM) with central composite design (CCD) was used to investigate the adsorption properties of phenol and p-chlorophenol (PCP) onto as-synthesized composite. The RSM was also applied to study the main and interactive effects of the parameters (pH, adsorbent dosage, contact time, and initial pollutant concentration) investigated, as well as to obtain the optimum operating conditions for this novel adsorbent. Magnetic powdered activated carbon (MPAC) showed an excellent magnetic response to the magnetic field and was easily separated from the solution. Moreover, the RSM model obtained (R2 > 0.98) revealed a satisfactory correlation between the experimental results and predicted values of phenol and PCP adsorption. The adsorbent dose was indicated as having the strongest positive influence on adsorption. The identified optimum conditions of adsorption was 6, 118 min, 1.6 g/L and 200 mg/L for pH, contact time, adsorbent dose, and initial phenol and PCP concentration, respectively. The adsorption kinetics fitted well with pseudo-second-order model and the adsorption capacity of phenol and PCP on MPAC inferred from the Langmuir model was 123.45 and 120.48 mg/g, respectively, at 20 °C. In addition, the adsorption activity of MPAC was preserved effectively even after five successive cycles of use owing to its good stability. The thermodynamic parameters indicated that the adsorption of phenol and PCP onto modified PAC was an exothermic and spontaneous process.