Removal of atrazine from aqueous solutions onto a magnetite/chitosan/activated carbon composite in a fixed-bed column system: optimization using response surface methodology

Abstract

In this study, a magnetite/chitosan/activated carbon (MCHAC) composite is proposed as an efficient adsorbent for the removal of atrazine from aqueous solutions. The prepared composite was characterized using Fourier-transform infrared (FTIR) and X-ray diffraction (XRD) methods. Response surface methodology (RSM) coupled with composite central design (CCD) were used to optimize the effects of the four independent variables, pH, initial concentration of atrazine (<i>C</i> ₀), bed depth (<i>H</i>), and flow rate (<i>Q</i>), which influence the adsorption process. The experimental results modeled using response surface methodology (RSM) coupled with central composite design (CCD) (RSM-CCD) indicated a quadratic relationship with <i>p</i> < 0.0001 for adsorption capacity at saturation (<i>q</i> _s) and fraction of bed utilization (FBU). The results of the experiments performed under the optimized conditions, pH = 5.07, <i>C</i> ₀ = 137.86 mg L^-1, <i>H</i> = 2.99 cm and <i>Q</i> = 1.038 mL min^-1, showed a <i>q</i> _s value of 62.32 mg g^-1 and FBU of 72.26%, with a deviation value of less than 0.05 from the predicted <i>q</i> _s and FBU values. The obtained breakthrough curves were fitted with four mathematical models, Thomas, Bohart-Adams, Yan and Yoon-Nelson, in order to determine the limiting step of the mass transfer of the atrazine adsorption onto the composite. A desorption study of the composite revealed the high reuse potential for MCHAC, thus, the prepared material could be used as a low-cost and efficient adsorbent for the decontamination of polluted wastewater.