Biochar-Based Magnetic Nanocomposite for Dye Removal from Aqueous Solutions: Response Surface Modeling and Kinetic Study

In this study, a biochar-based magnetic nanocomposite (BMNC) was synthesized and employed as adsorbent for Eriochrome Black T (EBT) removal from aqueous solutions. The biochar was prepared from oleaster stones and composited with iron oxide nanoparticles produced through chemical co-precipitation technique. The magnetic nanocomposite was characterized by X-ray diffraction analysis, Fourier transform infrared spectrometry, and scanning electron microscopy. The experiments were carried out using the Box-Behnken experimental design (BBD) with four input variables of adsorbent dosage (0.4–2.4 g L –1 ), solution pH (3–9), contact time (30–50 min), and ionic strength (0.02–0.1 M). An initial EBT concentration of 50 mg L –1 was taken as the fixed input parameter. Regression analysis resulted in a quadratic response surface model whose statistical significance was verified by analysis of variance. The model predicted the optimum conditions for EBT removal from aqueous solution (adsorbent dosage of 2.29 g L –1 , pH 3.39, contact time of 48.6 min and ionic strength of 0.1 M) and removal efficiency of 98.11% was achieved. Results of the study showed that the dye adsorption onto the magnetic nanocomposite followed the pseudo-second order kinetic model.