Quan Gan,Huijie Hou,Sha Liang,Jingjing Qiu,Shuangyi Tao,Liang Yang,Wenbo Yu,Keke Xiao,Bingchuan Liu,Jingping Hu,Yanfei Wang,Jiakuan Yang
Fe-rich biochar with multivalent iron compounds (Fe 0 , Fe 0.95 C 0.05 , Fe 3 O 4 , and FeAl 2 O 4 ) pyrolyzed from sludge cake conditioned with Fenton's reagent and red mud was utilized as an efficient Fenton catalyst for the degradation of 4-chlorophenol (4-CP). Effects of pyrolysis temperature and sludge conditioner composition on the transformation of iron compounds were studied. Both homogeneous Fenton reaction initiated by Fe 2+ leached from both low-valent Fe 0 and Fe 0.95 C 0.05 , and heterogeneous Fenton reaction initiated by solid iron phases of Fe 3 O 4 and FeAl 2 O 4 were revealed to contribute to the degradation of 4-CP. The removal efficiency of 4-CP remained 100% after five successive degradation rounds. The homogeneous Fenton reaction mainly works in the first degradation round, and the heterogeneous Fenton reaction dominates in subsequent degradation rounds. The findings of this study suggest that sewage sludge derived Fe-rich biochar could be utilized as an efficient Fenton catalyst for recalcitrant organics degradation .
Water contamination caused by organic dyes has become a significant concern, and catalytic degradation of dye pollutants is an effective solution. However, developing an affordable, easy-to-prepare, high-catalytic-activity, and renewable catalyst has proved challenging. The current study addresses this issue by introducing an efficient heterogeneous Fenton catalyst, known as multivalent iron-based magnetic porous biochar (mFe-MPB). This catalyst comprises multiple iron species, such as Fe 3 O 4 , γ-Fe 2 O 3 , zero-valent Fe (Fe 0 ), and Fe 3 C. The mFe-MPB was easily prepared by utilizing a straightforward crosslinking-pyrolysis strategy with natural peach gum polysaccharide (PGP), which has a unique structure and composition that facilitates the creation of multivalent iron species. The mFe-MPB demonstrates high catalytic activity in the degradation of an array of dyes, including cationic dyes such as methylene blue (MB) and methyl violet (MV), as well as anionic new coccine (NC) dye. Its mass standardized rate constant value for catalytic degradation of MB can reach as high as 1.65 L min −1 g −1 . Additionally, the catalyst can be easily recovered through magnetic separation and possesses remarkable structural stability, enabling several reuses without compromising its efficiency. Therefore, this study offers a viable strategy to fabricate low-cost, efficient and sustainable Fenton catalyst for removal of dye pollutants from water.
Yi Li,Xiaolin Zhao,Qinwen Cui,Yaxin Huang,Youwei Wang,Erhong Song,Zhengyang Zhou,Yong Yang,Jianjun Liu
Phase stability of high-nickel layered materials is crucial for enhancing the cyclic performance of lithium-ion batteries. The successive phase transition, accompanied by lattice contraction and stretching in high-nickel cathodes, results in continuous accumulation of lattice strain and structural destruction. Here, we propose a novel approach of adaptively-generated multivalent transition metal disordering to inhibit the destructive phase transitions in layered materials. To demonstrate feasibility, we design a binary high-nickel cathode material, LiNi 0.85 Fe 0.15 O 2 (LNF8515), which utilizes the variable valence of Fe to prevent the successive phase transition through charge delocalization. Effective regulation of the redox mechanism of transition metals through potentiostatic control is essential to mitigate significant continuous phase changes resulting from polarization. In LNF8515, the absence of Li + /Ni 2+ anti-site defects enables the material to achieve an initial capacity of 217.8 mAh g −1 . LNF8515 does not undergo continuous phase transition, resulting in improved cycling stability and reduced strain. In-situ XRD, grazing incident wide angle X-ray scattering and first-principles studies indicate that adaptively-generated multivalence of Fe 2+ , Fe 3+ , and Fe 4+ prevent charge localization, suppressing the continuum phase transition. This study paves a new avenue to improve the cyclic stability of high-nickel oxide cathodes.
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