Mahboobeh Zarei - Environmental Engineering, Water and Wastewater, Kish International Campus, University of Tehran, Tehran, Iran.
Majid Baghdadi - Department of Environmental Engineering, Graduate Faculty of Envirenment, University of Tehran, Tehran, Iran.
Fatemeh Yazdian - Department of Life Science Engineering, Faculty of New Science and Technology, University of Tehran, Tehran, Iran.
Nasser Mehrdadi - Department of Environmental Engineering, Graduate Faculty of Envirenment, University of Tehran, Tehran, Iran.

In this study, an optimized composite of expanded graphite /g-C۳N۴ /phenylenediamine was synthesized and characterized by SEM, FESEM, EDS, XRD, and BET methods.The composite was prepared with an optimized combination using response surface methodology (RSM) as a proper adsorbent for eliminating heavy metals from water samples. The evaluation of the final adsorbent was accomplished by removing metal ions like Pb۲+ and Cd۲+. Under the optimum adsorption conditions for Pb۲+ and Cd۲+ (pH:۵, adsorbent dosage:۲ g/L, and Time:۶۰ min), elimination efficiencies were ۷۸.۴% for Cd۲+ and ۷۱.۳۵% for Pb۲+. pH was the most important factor that influenced the adsorption rate. A short contact time for maximum removal efficiency was reported because of the porous structure of the constructed composite. As a result of the absorptive construction, the equilibrium showed a satisfactory agreement with the Freundlich model. The kinetic evaluations showed that the adsorption process of both heavy metals fitted the pseudo-second-order model. Furthermore, the results of thermodynamic studies indicated that the adsorption was an endothermic and spontaneous process. A series of regeneration experiments (۵ cycles) was directed to evaluate the adsorbent reusability. The results presented that it was a suitable adsorbent for heavy metal uptake from aquatic solutions.

Response Surface Methodology, Expanded graphite, Adsorption, Cadmium, Lead