Hongying Zhao

Three-Dimensional Homogeneous Ferrite-Carbon Aerogel: One Pot Fabrication and Enhanced Electro-Fenton Reactivity

This work focuses on constructing a high catalytic activity cathode of an electro-Fenton system, to overcome the defects of low activity, poor stability, and intricate fabrication of supported catalysts. A series of ferrite-carbon aerogel (FCA) monoliths with different iron/carbon ratios was synthesized directly from metal-resin precursors accompanied by phase transformation. Self-doped ferrite nanocrystals and carbon matrix were formed synchronously via moderate condensation and sol-gel processes, leading to homogeneous texture. An optimal 5% ferric content FCA was composed of coin-like carbon nano-plate with continuous porous structure, and the ferric particles with diameters of dozens of nanometers were uniformly embedded into the carbon framework. The FCA exhibited good conductivity, high catalytic efficiency, and distinguished stability. When it was used as an electro-Fenton cathode, metalaxyl degradation results demonstrated that 98% TOC elimination was realized after 4 h, which was 1.5 times higher than that of the iron oxide supported electrode. It was attributed to self-doped Fe@Fe(2)O(3) ensuring Fe(II) as the mediator, maintaining high activity via reversibe oxidation and reduction by electron transfer among iron species with different valences. Meanwhile, an abundance of independent reaction microspaces were provided for every ferric crystal to in situ decompose electrogenerated H(2)O(2). Moreover, the possible catalytic mechanism was also proposed. The FCA was a promising candidate as potential cathode materials for high-performance electro-Fenton oxidation.

Continuous Bulk FeCuC Aerogel with Ultradispersed Metal Nanoparticles: An Efficient 3D Heterogeneous Electro-Fenton Cathode over a Wide Range of pH 3–9

Novel iron-copper-carbon (FeCuC) aerogel was fabricated through a one-step process from metal-resin precursors and then activated with CO2 and N2 in environmentally friendly way. The activated FeCuC aerogel was applied in a heterogeneous electro-Fenton (EF) process and exhibited higher mineralization efficiency than homogeneous EF technology. High total organic carbon (TOC) removal of organic pollutants with activated FeCuC aerogel was achieved at a wide range of pH values (3-9). The chemical oxygen demand (COD) of real dyeing wastewater was below Chinas discharge standard after 30 min of treatment, and the specific energy consumption was low (9.2 kW·h·kg(-1)COD(-1)), corresponding to a power consumption of only ∼0.34 kW·h per ton of wastewater. The enhanced mineralization efficiency of FeCuC aerogel was mostly attributable to ultradispersed metallic Fe-Cu nanoparticles embedded in 3D carbon matrix and the CO2-N2 treatment. The CO2 activation enhanced the accessibility of the aerogels pores, and the secondary N2 activation enlarged the porosity and regenerated the ultradispersed zerovalent iron (Fe(0)) with reductive carbon. Cu(0) acted as a reduction promoter for interfacial electron transfer. Moreover, activated FeCuC aerogel presented low iron leaching (<0.1 ppm) in acidic solution and can be molded into different sizes with high flexibility. Thus, this material could be used as a low-cost cathode and efficient heterogeneous EF technology for actual wastewater treatment.

Introduction of a Fe3O4 Core Enhances the Photocatalytic Activity of MIL‐100(Fe) with Tunable Shell Thickness in the Presence of H2O2

Metal–organic frameworks (MOFs) are a new class of porous crystallized materials, which have attracted great interest for sustainable energy and environmental remediation. The functionalization of MOF‐based catalysts has been investigated to improve their photocatalytic ability. Here, we present a way of enhancing a magnetic MOF‐based photocatalyst composed of MIL‐100(Fe) and Fe3O4. The photocatalytic performance of the MOFs was significantly enhanced by the simultaneous introduction of a Fe3O4 core and H2O2, as the photoinduced holes and electrons of the MOF were relayed to the core F3O4 and reacted with H2O2, respectively. The optimal thickness of the MOF shell is ≈50 nm for core–shell Fe3O4@MIL‐100 microspheres to achieve the highest photocatalytic ability. Moreover, core–shell Fe3O4@MIL‐100(Fe) can be easily recycled without significant loss of photocatalytic ability after being used several times.

Enhanced Oxidative and Adsorptive Removal of Diclofenac in Heterogeneous Fenton-like Reaction with Sulfide Modified Nanoscale Zerovalent Iron

Sulfidation of nanoscale zerovalent iron (nZVI) has shown some fundamental improvements on reactivity and selectivity toward pollutants in dissolved-oxygen (DO)-stimulated Fenton-like reaction systems (DO/S-nZVI system). However, the pristine microstructure of sulfide-modified nanoscale zerovalent iron (S-nZVI) remains uncovered. In addition, the relationship between pollutant removal and the oxidation of the S-nZVI is largely unknown. The present study confirms that sulfidation not only imparts sulfide and sulfate groups onto the surface of the nanoparticle (both on the oxide shell and on flake-like structures) but also introduces sulfur into the Fe(0) core region. Sulfidation greatly inhibits the four-electron transfer pathway between Fe(0) and oxygen but facilitates the electron transfer from Fe(0) to surface-bound Fe(III) and consecutive single-electron transfer for the generation of H2O2 and hydroxyl radical. In the DO/S-nZVI system, slight sulfidation (S/Fe molar ratio = 0.1) is able to nearly double the oxidative removal efficacy of diclofenac (DCF) (from 17.8 to 34.2%), whereas moderate degree of sulfidation (S/Fe molar ratio = 0.3) significantly enhances both oxidation and adsorption of DCF. Furthermore, on the basis of the oxidation model of S-nZVI, the DCF removal process can be divided into two steps, which are well modeled by parabolic and logarithmic law separately. This study bridges the knowledge gap between pollutant removal and the oxidation process of chemically modified iron-based nanomaterials.

Reinvestigating the role of reactive species in the oxidation of organic co-contaminants during Cr(VI) reactions with sulfite

Experimental work was undertaken in this study to re-investigate the mechanisms and active species responsible for oxidation of co-contaminants in the Cr(VI)/HSO3- reaction system. Batch experiments showed that the degradation rates of 4-chlorophenol (4-CP) correlated well with the rates of Cr(VI) reduction by sulfite in the same solutions, and that O2(aq) was necessary for the oxidation of 4-CP. Multiple lines of evidences indicate that Cr(VI)/HSO3- reaction is a SO4--based oxidation process. SO3- was generated in Cr(VI)/HSO3- system based on the electron spin resonance spectra, which could be transformed to secondary radicals (SO4-, SO5-, and HO). The contribution of SO5- was ruled out through almost complete inhibition of methanol (MeOH) on 4-CP degradation. Considering the negligible inhibition of tert-butanol (TBA) on 4-CP degradation, SO4- was identified to be reactive species in Cr(VI)/HSO3- process. This result was further verified by almost no degradation of nitrobenzene and the inhibiting effect of Cl- in Cr(VI)/HSO3- process. This mechanism is beneficial to application of Cr(VI)/HSO3- system in wastewater treatment.