Structure Regulation and Performance Optimization of Porous Carbon and Iron Phosphide Catalysts for Heterogeneous Fenton-like Reactions

非均相類芬頓反應多孔碳及磷化鐵催化劑的結構調控與性能優化

Student thesis: Doctoral Thesis

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Author(s)

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Detail(s)

Awarding Institution
Supervisors/Advisors
  • Hanqing YU (External person) (External Supervisor)
  • Chi Kit Andy SIU (Supervisor)
  • Zhengtao XU (Supervisor)
Award date1 Dec 2022

Abstract

Heterogeneous Fenton-like technology is an important solution for water pollution control. It can efficiently degrade organic water pollutants by producing strong oxidative reactive oxygen species through the catalytic activation of peroxides. In heterogeneous Fenton-like reactions, the catalyst is the key to the quick generation of reactive oxygen species and efficient degradation of pollutants. However, the study of heterogeneous Fenton catalysts still faces some key challenges. First, porous catalysts can promote heterogeneous Fenton catalysts by enriching the reactants, but the relationship between the pore structure and catalytic performance is not clear, which hinders the development of efficient porous catalysts. Second, many existing heterogeneous catalysts cannot efficiently produce strongly oxidative radicals, leading to unsatisfying performance for the treatment of many emerging refractory pollutants. In addition, most of the current heterogeneous catalysts for Fenton-like reactions are powder materials, which are not easy to separate and recycle during use. Therefore, these powder catalysts can hardly be used in practical water treatment. To solve the above problems, this dissertation conducted research from three aspects. First, accurate regulation of the pore structure of porous carbon materials was achieved through the assembly strategies to reveal the influence of pore structure on the catalytic performance. Then, a catalyst with good electron transfer capability was developed for the efficient catalytic generation of hydroxyl radicals. Finally, a method for molding the powder material was developed to prepare a porous catalyst of macroscopic size, and the performance of the catalyst for the adsorptive enrichment and catalytic oxidation of refractory organic pollutant was demonstrated. The main research contents and achievements of this paper are summarized as follows:

1. The catalytic removal of organic water pollutants was enhanced by tuning the internal structure of porous carbon spheres. To reveal the influence of internal structure on the catalytic performance of porous carbon material, we developed a sequential assembly strategy to prepare a series of porous carbon spheres with hollow or core-shell structures. Through systematic comparison of their performance for pollutants oxidation through catalytic activation of peroxymonosulfate, we found that the hollow spheres exhibited over three times the catalytic activity of the core-shell counterparts, and confirmed the enrichment of pollutants in porous structures through adsorption and the superiority of the hollow structure in the catalytic reactions. Through further analysis of the material structure and catalytic mechanism, the superiority of the hollow structure could be attributed to its enrichment of short-lived reactive oxygen species such as singlet oxygen generated in the catalytic process. By reducing the cavity size of the hollow structure, the reaction between the pollutant and the singlet oxygen could be further promoted, thus enhancing the removal of the pollutant.

2. The quantitative relationship between the pore structure of porous carbon spheres and their performance in the catalytic removal of pollutants was revealed. A quantitative co-assembly strategy was developed for precise regulation of the pore structures of porous nanoparticles. This strategy utilized the co-assembly of resin and silica to prepare resin/silica composite nanoparticles. By adjusting the amount of ammonia in the synthesis system, the growth kinetics of the composite nanoparticles could be regulated and the pore structure of the derived porous particles could be quantitatively controlled. A series of porous carbon spheres with precise and tunable pore size and pore length were prepared. These porous carbon spheres were applied in the catalytic degradation of sulfonamide pollutant. By quantitatively analyzing the relationships between the catalytic performance for pollutants removal and the size and length of the pores, the enhancement effect of the small and long pores on the catalytic performance for pollutants oxidation was accurately revealed.

3. An iron-based catalyst was developed for the efficient activation of hydrogen peroxide to degrade organic pollutants. To achieve efficient catalytic production of radicals, we prepared FeP with good electron transfer capability as a catalyst for the Fenton-like reaction. By comparing with the conventional Fe-based catalysts such as Fe2O3, Fe3O4, and FeOOH, we found that FeP showed lower electron transfer resistance, and had a higher ability to produce hydroxyl radicals through activating hydrogen peroxide for pollutant degradation. Hydroxyl radicals were identified as the active species for pollutant removal in the system and FeP showed better performance than the traditional iron-based catalysts for the catalytic production of radicals. Moreover, the FeP catalysts exhibited good catalytic performance in real water samples and showed good stability during recycling use.

4. Porous catalyst with macroscopic size was prepared for Fenton-like reactions. As powder catalyst is not suitable for practical application, we prepared iron-carbon composite catalysts with macroscopic size. First, we conducted mass preparation of the powder of porous polyacrylonitrile nanospheres, and then molded and calcined the powder to obtain centimeter-sized porous carbon. Then, we took the porous carbon as support to immobilize iron phosphide to obtain an iron-carbon composite catalyst with a centimeter size. This composite catalyst exhibited good performance for adsorptive enrichment and catalytic oxidation of p-nitrophenol and showed good application potential.

    Research areas

  • Fenton-like reactions, porous material, persulfate, hydrogen peroxide, structure-performance relationship, catalyst molding