Polypyrrole-Reinforced N,S-Doping Graphene Foam for Efficient Solar Purification of Wastewater

Solar vapor generation is a sustainable and cost-effective approach to addressing the issue of water shortage. However, the challenges of solar steam generation still exist for achieving a high evaporation efficiency combined with long-term stability in the wastewater containing heavy metal ions and wide degrees of acidity and alkalinity (pH = 1–14). Herein, polypyrrole (PPy) loading on the N,S-doped graphene oxide (N,S-GO) foam is used for high-efficiency solar evaporation of treating wastewater. With the advantages of excellent broadband solar absorption (>97%), extremely low emissivity (0.70), and outstanding hydrophilicity, the N,S-GO/PPy foam achieves a high evaporation efficiency of 90.5% under 1 sun illumination. More notably, the N,S-GO/PPy foam has strong adsorption of heavy metal ions (Fe³⁺, Cu²⁺, and Cr⁶⁺) for treating wastewater synchronously evaporates at higher efficiencies of 94.7–98.4%. Interestingly, the high-toxicity Cr⁶⁺ can be reduced to low-toxicity Cr³⁺ effectively by the synergistic effect of N,S-GO and PPy. In addition, the N,S-GO foam shows a better long-term resistance of acidity and alkalinity for 45 days. A new insight is offered into high-efficiency solar evaporation for treating wastewater and water purification.