Insight into enhanced Fenton-like degradation of antibiotics over CuFeO2 based nanocomposite: To improve the utilization efficiency of OH/O2- via minimizing its migration distance

Efficiently catalytic ozonation of 2,4-dichlorophenoxyacetic acid by natural ferrihydrite: A pH dependent and surface -OH group involved reaction mechanism

The heterogeneous catalytic ozonation with natural iron oxides has been proven to be a powerful technology for the removal of recalcitrant organics in water due to the involvement of reactive oxygen species. However, little information can be obtained about the performance of Ferrihydrite in catalytic ozonation especially the relavant reaction mechanism. In this study, Ferrihydrite was synthesized via a simple precipitation method and 2,4-Dichlorophenoxyacetic acid (2,4-D) degradation was used to evaluate its catalytic ozonation performance. Compared with sole ozonation, Ferrihydrite had an excellent activity in catalytic ozonation and 2,4-D was always efficiently degraded (>90%) at a wide pH range (3.0-8.0). Electron spin resonance (ESR) and radical scavenging tests proved that •OH and O2•- were the dominant reactive oxygen species (ROS) in 2,4-D degradation (92.33% vs. 77.4% in ozone alone) and mineralization (63% vs. 16.2% in ozone alone). Based on a series of characterizations, Ferrihydrite processed a higher BET area and surface -OH groups than other iron oxides such as FeOOH, Fe2O3 and Fe3O4. The efficiently exposed surface -OH group with a high density was the reactive centers for the generation of ROS. Importantly, pHPZC of Ferrihydrite (6.3) and pKa of 2,4-D (2.73) induced a pH-dependent 2,4-D removal patterns (surface reaction at pH < 6.3 and reaction in bulk solution at pH > 6.3) were proposed via the electrostatic attraction or repulsion between the hydrogenated/hydroxylated surface of Ferrihydrite and negative charged 2,4-D.

Photoelectrochemical Conversion of Sewage Water into H2 Fuel over the CuFeO2/CuO/Cu Composite Electrode

This study describes the synthesis of delafossite, CuFeO2, as a primary photocatalytic material for hydrogen generation. A photoelectrode, CuFeO2/CuO/Cu, was prepared by combusting a Cu foil dipped in FeCl3 in ambient air. This photoelectrode showed excellent optical behavior for the hydrogen generation reaction from sewage water, producing 90 µmol/h of H2. The chemical structure was confirmed through XRD and XPS analyses, and the crystalline rhombohedral shape of CuFeO2 was confirmed using SEM and TEM analyses. With a bandgap of 1.35 ev, the prepared material displayed excellent optical properties. Electrochemical measurements for H2 gas generation were carried out using the CuFeO2/CuO/Cu photoelectrode, comparing the effect of light and dark and monochromatic wavelength light. The electrode exhibited significant enhancement in light compared to dark, with current density (Jph) values of −0.83 and −0.1 mA·cm−2, respectively. The monochromatic light also had a noticeable effect, with the Jph value increasing from −0.45 to −0.79 mA·cm−2 as the wavelength increased from 640 to 390 nm. This system is cheap and durable, making it a promising solution for hydrogen gas fuel generation in the industry.

Catalytic activity and mechanism of typical iron-based catalysts for Fenton-like oxidation

Heterogeneous Fenton-like systems were exploited for the degradation of Reactive Red X-3B (RR X-3B) using iron-carbon composite, sponge iron, chalcopyrite and pyrite as catalysts. The effect of operational variables on the catalytic activity and metal leaching behavior of catalysts was evaluated and the catalytic mechanism was discussed. The experimental results showed that under the optimum conditions, chemical oxygen demand (COD) removals by Fenton-like systems could reach 89.91%, 86.84%, 80.11% and 60.02% with iron-carbon composite, sponge iron, chalcopyrite and pyrite, respectively. Micro-electrolysis of iron-carbon composite and sponge iron resulted in higher COD removal at acid pH range. Electron Paramagnetic Resonance (EPR) analysis and quenching tests showed that ^•OH was the main reactive oxygen species responsible for the degradation of RR X-3B. A large amount of Fe²⁺ leached from iron-carbon composite and sponge iron, which served as a homogeneous Fenton catalyst during the degradation of RR X-3B. In contrast, much lower amount of Fe²⁺ was leached from chalcopyrite and pyrite, and surface catalysis of the minerals played more important role in the generation of ^•OH. Surface characterization and density functional theory (DFT) calculation results illustrated that ≡Fe(II) was the primary surface catalytic site during the reaction. The reduction of ≡Fe(III) and ≡Cu(II) can be facilitated by sulfides on the mineral surface. The Fenton-like systems catalyzed by iron-based materials exhibited higher H₂O₂ utilization and COD removal than classical Fenton system. With the lower metal leaching concentration and stable surface property, chalcopyrite and pyrite may be more practical applicable from a long-term catalytic activity point of view.

Mechanisms of biochar enhanced Cu2O photocatalysts in the visible-light photodegradation of sulfamethoxazole

Cu₂O nanoparticles are decorated with biochars derived from spent coffee grounds (denoted as Cu₂O/SCG) and applied as visible-light-active photocatalysts in the sulfamethoxazole (SMX) degradation. The physicochemical properties of Cu₂O/SCG are identified by various spectral analysis, electrochemical and photochemical techniques. As a result, the Cu₂O/SCG exhibits the higher removal efficiency of SMX than the pristine Cu₂O under visible light irradiation. We can observe that Cu₂O could be incorporated onto the SCG biochars with rich oxygen vacancies/adsorbed hydroxyl groups. In addition, the Cu₂O/SCG has the lower charge transfer resistance, faster interfacial electron transfer kinetics, decreased recombination of charge carriers and superior absorbance of visible light. The construction of band diagrams for Cu₂O/SCG and pristine Cu₂O via UV-vis spectra and Mott-Schottky plots suggest that the band energy shifts and higher carrier density of Cu₂O/SCG may be responsible for the photocatalytic activity enhancements. From the radical scavenger experiments and electron paramagnetic resonance spectra, the aforementioned energy shifts could decrease the energy requirement of transferring photoinduced electrons to the potential for the formation of active superoxide radicals (·O₂^-) via one and two-electron reduction routes in the photocatalytic reaction. A proposed degradation pathway shows that ·O₂^- and h⁺ are two main active species which can efficiently degrade SMX into reaction intermediates by oxidation, hydroxylation, and ring opening. This research demonstrates the alternative replacement of conventional carbon materials for the preparation of biochar-assisted Cu₂O photocatalysts which are applied in the environmental decontamination by using solar energy.