Selective reduction of nitrate to nitrogen by Fe0-Cu0-CuFe2O4 composite coupled with carbon dioxide anion radical under UV irradiation

Construction of an S-scheme electron transfer channel in Cu0/CuFe2O4 magnetic plate column reactor for the LEV degradation: New strategy of visible Photo-Fenton system application

The complicated loading process and easy falling off of powder catalysts still restrict the wide application of Photo-Fenton technology in practical water treatment. In this study, a magnetic fixed film plate column water treatment equipment is designed as a visible Photo-Fenton reactor to remove levofloxacin (LEV). The effect of magnetic force can ensure that the catalyst is firmly fixed, and the multi-level shallow column plate structure achieves full contact and efficient reaction between the catalyst and wastewater. Simultaneously, the Cu0/CuFe2O4 (STCCF) utilizes Cu0 to construct an S-scheme electron transfer channel, which improves the separation efficiency of photo-generated carriers and provides sufficient photo-generated electrons for the reduction of Fe (Ⅲ) and Cu (Ⅱ). The pseudo-first-order reaction kinetic constant k for the degradation of LEV in the visible Photo-Fenton system is 0.0349 min-1, which is 15.9 times that of the photocatalytic system and 4.8 times that of the Fenton system. After continuous operation for 72 h, the magnetic fixed film plate column reactor can still remove more than 90 % of LEV and 82 % of COD in the secondary effluent of simulated antibiotic pharmaceutical wastewater treatment process, and the effluent is stable and meets the standard. The magnetic fixed film plate column reactor can be used for advanced treatment of antibiotic pharmaceutical wastewater. This study provides a new insight into the application of the Photo-Fenton process.

Electrochemical Redox Conversion of Formate to CO via Coupling Fe-Co Layered Double Hydroxides and Au Catalysts

Formate has been considered an inactive molecule and thus cannot be further reduced under CO2 reduction conditions, which limits its widespread application as feedstock. Here we present an electrochemical redox conversion of formate to CO through the potential-dependent generation of carbon dioxide radical anions (CO2 ⋅- ) on Fe-Co layered double hydroxides (Fe-Co LDHs) and the subsequent reduction of CO2 ⋅- to CO on Au catalysts. We present an electrodeposition protocol for the synthesis of Fe-Co LDHs with precise composition control and find that Fe1 Co4 exhibits a promising potential window for CO2 ⋅- formation between 1.14 and 1.4 V and an optimized potential at 1.24 V at a neutral pH condition. We further determined the formation of CO2 ⋅- at 1.24 V via electron paramagnetic resonance and CO2 at >1.4 V through differential electrochemical mass spectrometry. This work provides a redox chemistry route for converting formate into CO through a coupled slit parallel-plate electrode system.

Micro-electrolysis based nitrate reduction from aqueous solution by CNTs-Al-Cu composite under alkaline environment

CNTs-Al was prepared by ball milling combined with sintering process and then used for CNTs-Al-Cu synthesis with chemical deposition method. The obtained CNTs-Al-Cu composite was systematically characterized and its NO₃^--N reduction performance under alkaline condition was also evaluated. As indicated by the reduction batch experiment, 80.2% of NO₃^--N removal efficiency was obtained in 90 min at pH of 9. The product of the reduction process was dominated by NO₂^--N, which was further reduced to harmless N₂. The reusability of CNTs-Al-Cu composite was evaluated, and the experiment results showed that 68.1% of NO₃^--N removal efficiency was maintained after 3 cycles of regeneration. Finally, based on the characterization results and kinetic analysis, it was concluded that micro-electrolysis was mainly responsible for the removal of NO₃^--N by CNTs-Al-Cu.