Performance of granular activated carbon/nanoscale zero valent iron for removal of humic substances from aqueous solution based on Experimental Design and Response Surface Modeling

Abstract

Response surface methodology has been used to design experiments and to optimize the effect of independent variables responsible for higher adsorption of humic substances by activated carbon supported nanoscale zero-valent iron from aqueous solutions. The variables of initial concentration, time, pH, adsorbent dose was examined. The characterization of NZVI/AC was carried out by SEM-EDS and XRD analysis. The adsorption isotherms and kinetics of humic substances on AC and NZVI/AC were studied. The findings showed that the particle size of synthesis NZVI were in the range 20-50nm. The experimental data followed the Langmuir isotherm and pseudo-second kinetic model. For AC, optimum conditions of initial concentration, pH, contact time, and adsorbent dose were 5 mg L-1, 4.43, 46.28 min, and 1.5 g L-1, respectively. For NZVI/AC, optimum conditions of initial concentration, pH, contact time, and adsorbent dose were 5.48 mg L-1, 5.44, 44.7 min, 0.65 g L-1, respectively. Predicted removal efficiency by Box-Benken models for activated carbon and NZVI were 60 and 100 percent, respectively.