In the present study, the activated carbon of lemon (ACL) was generated from Citrus limon wood waste and composited with Fe3O4 nanoparticles. The ACL/Fe3O4 magnetic composite was effectively used to eliminate Cd2+ from an aqueous solution. The active surface area values for ACL and ACL/Fe3O4 magnetic composite were 25.99 m2/g and 38.70 m2/g, respectively indicating the effectiveness of Fe3O4 nanoparticles in improving ACL active surface area. The response surface methodology with central composite design (RSM-CCD) was used to determine optimal values of pH, ACL/Fe3O4 dose, contact time, and Cd2+ concentration on the decontamination efficiency. The Langmuir and Freundlich isotherm models had more potential to describe the adsorption process using ACL and ACL/Fe3O4, respectively. The Langmuir-based adsorption capacity was obtained as 28.2 mg/g (ACL) and 39.6 mg/g (ACL/Fe3O4). A pseudo-second order (PSO) model was successfully applied to evaluate the adsorption process kinetic behavior. A higher value of α parameter for ACL/Fe3O4 (5.7 mg/g.min) than that of ACL (3.5 mg/g.min) indicated that the magnetic composite had a greater tendency to absorb Cd2+. In addition, the Weber-Morris model showed that various mechanisms such as intraparticle diffusion and boundary layer effects may have a role in the adsorption process. The study of ad(de)sorption behavior showed that the adsorbents have a good ability to adsorb Cd2+ and no significant change in their performance has been made up to 4 times of reuse. Our results showed that ACL modification using Fe3O4 nanoparticles improved the adsorption efficiency of ACL to remove Cd2+ from the aqueous solutions.
Keywords: Cd(2+) adsorption; Isotherm models; Lemonwood carbon; Magnetic composite.
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