Liping Wei,Kexin Zhou,Hui-qiang Li,Ping Yang,Baicang Liu
Most of the materials studied as catalysts in the electro-Fenton system are variants of iron oxide or iron hydroxide. However, iron-based catalysts often exhibit weak catalytic capabilities under neutral and alkaline conditions. In this work, we synthesized three cobalt based bimetallic oxides, Co2CuOx, Co2AlOx, and Co2NiOx, using hydrothermal method and evaluated them as catalysts for the heterogeneous electro-Fenton system to remove 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) and Methylisothiazolinone [2-methyl-4-isothiazolin-3-one] (MIT). Co2NiOx has the highest catalytic degradation activity for HEDP, and Co2CuOx has the best catalytic degradation effect for MIT. Based on characterization results of the catalysts, the reasons for the differences in the pollutant removal efficiency were analysed, and the optimal pH for the three cobalt based oxides to remove HEDP and MIT was investigated. The results showed that the optimal pH values of the three cobalt based bimetallic oxides are not only influenced by the second metal type, but also by the properties of pollutants. Therefore, suitable cobalt based catalysts can be selected based on the different properties of pollutants, or the composition of cobalt based catalysts can be adjusted to meet the different pH requirements of target wastewater. The three cobalt based bimetallic oxides exhibited good degradation of HEDP and MIT under neutral conditions, which to some extent solved the problem of narrow pH range in the practical application of the electro-Fenton process.
Min Chen,Can Wang,Yingcai Wang,Xiaoyang Meng,Zefang Chen,Weiqiu Zhang,George Tan
In this study, a novel Ti-enhanced nanotube arrays/SnO 2 -Sb electrode was prepared by the sol-gel method on enhanced TiO 2 nanotube arrays (ENTA). The characterization, degradation performance, oxidation mechanism and mass transfer impact of the novel electrode was investigated. Compared with the conventional Ti/SnO 2 -Sb electrode, our novel electrode has higher oxygen evolution potential and electrochemical stability, due to the fabrication of ENTA structure. Its application for the destruction of a common biocide of MIT (2-methyl-4-isothiazolin-3-one), the first-order rate constants were determined from 0.01 min −1 to 0.505 min −1 during the electrochemical process. The radical oxidation and non-radical oxidation of the MIT degradation contribution were quantitatively identified as 87.8% and 12.1%, respectively. Furthermore, the second-rate constant between hydroxyl radical and MIT was estimated at 3.72 × 10 9 M − 1 S − 1 . The mass transfer impact was investigated with a differential column batch reactor (DCBR) under the conditions of various electrode spacing and fluid velocities. It indicated that reducing the electrode spacing and increasing the fluid velocity would enhance the mass transfer process and increase the overall oxidation rate. Meanwhile, the EE/O decreased from 17.7 kWh m −3 to 9.7 kWh m −3 , and the mass transfer coefficients increased dramatically from 0.52 × 10 −6 m s −1 to 2.48 × 10 −6 m s −1 .
Hui-qiang Li,Mei-yu Zhang,Ke-xin Zhou,Ping Yang,Zhi-wei Gan,Zhi Li
s Iron-based catalysts are widely used in the electro-Fenton technology, which are limited by strict acidic conditions. Cobalt-based catalysts can undergo Fenton-like reactions with H 2 O 2 under neutral conditions. In this study, a CF@Co 2 NiO x @MgAl-LDH cobalt-based bimetallic catalyst was prepared to study 1-hydroxyethylidene-1 (HEDP) and methylisothiazolinone (MIT) degradation performance in a heterogeneous electro-Fenton system. Cobalt-based bimetallic oxides were first modified with magnesium-aluminum hydrotalcite (MgAl-LDH) and subsequently loaded onto carbon felts (CF) to reduce metal ion leaching and improve catalyst recyclability. The experimental results showed that CF@Co 2 NiO x @MgAl-LDH could effectively remove 93.06% of HEDP and 92.42% of MIT after 2 hours of reaction. Removal of HEDP and MIT was still achieved at 78.62% and 81.09% after four cycles of experiments. Based on the catalyst characterization results, the reasons for the differences in the pollutant removal performance were analyzed and the optimal operating parameters of the CF@Co 2 NiO x @MgAl-LDH for the removal of HEDP and MIT were investigated. This study provides a novel and sustainable strategy for the design and application of cobalt-based catalysts.
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