Green-synthesized reduced graphene oxide@chitosan beads for the removal of polycyclic aromatic hydrocarbons

Reduced graphene oxide and iron nanoparticles were prepared through a one-pot green route with eucalyptus leaf extract as a reducing agent and immobilized into chitosan beads (m-rGO@CS). In this study, the adsorption performance of these m-rGO@CS beads towards anthracene (ANT) and fluoranthene (FLT) was assessed through adsorption equilibrium, adsorption kinetics and thermodynamic analyses. An adsorbent dosage of 0.5 g/L and pH 8 was determined as the best operating conditions through a full-factorial design. The adsorption kinetic data of the contaminants were well-described by the pseudo-second-order model and indicated that the process might involve film and intraparticle diffusions as the main controlling steps. The equilibrium time for ANT and FLT adsorption was 360 and 1320 min, respectively. The Sips isothermal model best fitted the equilibrium data. The maximum removal capacity towards ANT and FLT was 16.97 and 12.19 mg/g, respectively. The thermodynamic parameters showed that the ANT and FLT adsorption processes are spontaneous and exothermic. The regeneration tests indicated that the material presented a decrease of 2% and 8% in the adsorption capacity of ANT and FLT, respectively, after three adsorption-desorption cycles.