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Anisotropic CoFe₂O₄@Graphene Hybrid Aerogels with High Flux and Excellent Stability as Building Blocks for Rapid Catalytic Degradation of Organic Contaminants in a Flow-Type Setup

Yu, Xiao-Jie, Qu, Jin, Yuan, Zuoying, Min, Peng, Hao, Shu-Meng, Zhu, Zhong-Shuai, Li, Xiaofeng, Yang, Dongzhi, Yu, Zhong-Zhen
ACS applied materials & interfaces 2019 v.11 no.37 pp. 34222-34231
acid orange 7, aerogels, anisotropy, catalysts, catalytic activity, foams, freeze drying, graphene, indigo carmine, isotropy, malachite green, metal ions, methyl orange, nanomaterials, norfloxacin, phenol, pollution, wastewater, wastewater treatment
Macroscopic three-dimensional catalytic materials could overcome the poor operability and avoid secondary pollution of common powdery counterparts, especially in flow-type setups. However, conventional isotropic graphene-based aerogels and foams have randomly distributed graphene sheets, which may cause stream erosion and reduce the flux seriously. Herein, for the first time, we design and fabricate a novel anisotropic CoFe₂O₄@graphene hybrid aerogel (CFO@GA-A) with a hydrothermal synthesis followed by directional-freezing and freeze-drying for a tube-like flow-type setup analogous to a wastewater discharge pipeline. The long and vertically aligned pores inside the aerogel provide an exceptional flux of 1100 L m–² h–¹, 450% higher than that of the rough and zigzag paths in the isotropic CoFe₂O₄@graphene hybrid aerogel (CFO@GA-I), and the leaching of metal ions is obviously inhibited by relieving the erosion of CoFe₂O₄. Besides, the CFO@GA-A could sustain the scour of high-speed flowing wastewater and maintain its structural stability. Therefore, organic contaminants of indigo carmine, methyl orange, orange II, malachite green, phenol, and norfloxacin could readily flow over the nanocatalysts and be degraded rapidly within 7.5–12.5 min at varied flow rates from 60 to 120 mL h–¹. The CFO@GA-A also exhibits a much better long-term stability with removal efficiencies toward indigo carmine at 100%, 91%, and 85% for at least 30 h (60 mL h–¹), 25 h (90 mL h–¹), and 21 h (120 mL h–¹), respectively. On the contrary, the CFO@GA-I exhibits unsatisfactory removal efficiencies of <40%. Interestingly, CFO@GA-A could also serve as building blocks to stack on each other for degrading intense flowing wastewater, exhibiting an outstanding composability. The high-flux and long-term stability make the CFO@GA-A promising as an ideal catalytic material for wastewater treatments.