Decoration of Citrus limon wood carbon with FeO to enhanced Cd removal: A reclaimable and magnetic nanocomposite.

In the present study, the activated carbon of lemon (ACL) was generated from Citrus limon wood waste and composited with FeO nanoparticles. The ACL/FeO magnetic composite was effectively used to eliminate Cd from an aqueous solution. The active surface area values for ACL and ACL/FeO magnetic composite were 25.99 m/g and 38.70 m/g, respectively indicating the effectiveness of FeO 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/FeO dose, contact time, and Cd concentration on the decontamination efficiency. The Langmuir and Freundlich isotherm models had more potential to describe the adsorption process using ACL and ACL/FeO, respectively. The Langmuir-based adsorption capacity was obtained as 28.2 mg/g (ACL) and 39.6 mg/g (ACL/FeO). A pseudo-second order (PSO) model was successfully applied to evaluate the adsorption process kinetic behavior. A higher value of α parameter for ACL/FeO (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 Cd. 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 Cd and no significant change in their performance has been made up to 4 times of reuse. Our results showed that ACL modification using FeO nanoparticles improved the adsorption efficiency of ACL to remove Cd from the aqueous solutions.