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.