Removal of lead and cadmium with an optimized composite of expanded graphite/g-C3N4/phenylenediamine

In this study, an optimized composite of expanded graphite /g-C3N4 /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 Pb2+ and Cd2+. Under the optimum adsorption conditions for Pb2+ and Cd2+ (pH:5, adsorbent dosage:2 g/L, and Time:60 min), elimination efficiencies were 78.4% for Cd2+ and 71.35% for Pb2+. 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 (5 cycles) was directed to evaluate the adsorbent reusability. The results presented that it was a suitable adsorbent for heavy metal uptake from aquatic solutions.