Effect of pH on Green Synthesis of Reduced Graphene Oxide Using Lemon Extract and Application of Fe۳O۴/RGO nanocomposites for the removal of Pb (II) from aqueous solution

Here, graphene oxide was synthesized and reduced by lemon extract (source of vitamin C) in an aqueous solution under different pH (۳ and ۱۰). The lemon extract was prepared using a solvent-free method. The proposed mechanisms for the reduction of GO may be due to the nucleophilic attack of oxygen anion of ascorbic acid to the epoxy or hydroxyl groups of GO sheets. Based on Raman spectra, with increasing the solution pH, the repair of the graphitic sp۲ domain of the RGOs decreased. Reduced graphene oxide was successfully used to synthesize Fe۳O۴/RGO nanocomposite and remove Pb ions from aqueous media. The obtained Fe۳O۴/RGO nanocomposite was characterized by XRD, FTIR, SEM, and BET analysis. Based on these characterization techniques, reduced graphene oxide is distinguishably coated by Fe۳O۴ nanoparticles. The effect of different parameters: contact time (۱-۶۰ min), initial lead concentration (۲۵-۲۰۰ mg/L), adsorbent dosage (۰.۰۱-۰.۰۷ g), and the solution’s initial pH (۱-۸) on the removal of lead ions was studied using batch-scale tests. The maximum lead ion removal was achieved up to ۹۰ % for Pb ions, respectively at optimum operating conditions viz. pH ۵, Pb initial concentration ۱۰۰ mg/L, Fe۳O۴/RGO dose ۰.۰۵ g, and contact time ۳۰ min. Obtained results showed that the maximum adsorption capacity of Fe۳O۴/RGO for lead ion was ۱۰۷.۵۲ mg/g within ۶۰ min of contact time. The adsorption behavior can be well described with the Langmuir isotherm and the pseudo-second-order models, indicating that the adsorption process was a monolayer and chemisorption adsorption. 

کلیدواژه ها:

Adsorption ، Fe۳O۴ nanoparticles ، Green reduction ، Lemon extract ، Reduced graphene oxide