Conversion of biomass to N, S co-doped porous graphene as an adsorbent for mercury vapor removal: optimization and DFT study

This study is devoted to optimization synthesis conditions of the N, S co-doped porous graphene via a single step thermal chemical activation process from agricultural wastes such as cabbage waste. To this end, the response surface method (RSM) was considered, and the synthesis parameters were varied in specific ranges. By doing so, the optimum conditions in terms of the best performance in mercury removal was determined which was characterized by TEM, SEM, BET, XRD, XPS, and FTIR techniques. The chosen key process parameters were Activation agent to carbon precursor ratio (A: KOH/C), Reaction time (B: Time), Activation temperature (C: Temperature), and (Dopant to carbon precursor ratio (D: Dopant/C). Each parameter was investigated in 3 levels with lower and upper bounds being A: 2-6; B:30-90 min.; C: 600-800 C; D:2-10. The optimum conditions of the process were determined to be as: A: 2; B: 30 min.; C: 600 C and D: 2. The optimized sample was prepared in repeated runs with reproducible results with Hg vapor adsorption capacity of 2100 mu g/g at 40 C and 2266 mu g/g at 90 C. In addition to the experiments, DFT calculations were also carried out which elucidated the positive role of N and S co-doping in improving the mercury adsorption intensity.

Automated summary

This study focused on optimizing the synthesis conditions of N, S co-doped porous graphene from agricultural waste through a single-step thermal chemical activation process. The response surface method (RSM) was utilized to determine the best parameters for mercury removal performance. Experimental results showed an excellent mercury adsorption capacity, and DFT calculations confirmed the positive impact of N and S co-doping on enhancing mercury adsorption intensity.