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 (C₀), bed depth (H), and flow rate (Q), 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 p < 0.0001 for adsorption capacity at saturation (q_s) and fraction of bed utilization (FBU). The results of the experiments performed under the optimized conditions, pH = 5.07, C₀ = 137.86 mg L⁻¹, H = 2.99 cm and Q = 1.038 mL min⁻¹, showed a q_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 q_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.