Yalan Liu,Zhihao Zhong,Xinxin Yu,jiageng Xiong,Shantang Liu
The degradation of Chlorinated volatile organic compounds (CVOCs) by catalytic oxidation forms toxic products, and catalysts may be poisoned by chlorine at low temperatures. To address this, a Cu-assisted strategy is proposed for enhancing the catalytic degradation of chlorobenzene (CB) over cobalt oxide nanosheets. The Cu-doped Co 3 O 4 catalysts exhibited lower T 90 values (temperatures with 90 % conversion) and improved stability compared to the unmodified catalyst. These results were attributed to strong metal-metal interactions between Cu species and cobalt oxide nanosheets, which showed a high specific surface area, reduced binding energy of lattice oxygen, higher surface oxygen concentration, and more surface Co 3+ species. These properties promoted low-temperature catalytic activity. In addition, the disappearance of Cu 2+ satellite peak after the catalyst is used, indicating that the Cu 2+ also contributes to the catalytic activity. Furthermore, the in situ FTIR spectra provided details about the reaction mechanism of CB degradation over Cu-doped cobalt oxide nanosheets. The oxygen vacancy generation and the surface absorption of chlorine-containing intermediates were calculated using density functional theory calculations. This study provides new insight into novel pathways for catalyst design aimed at CB degradation.
Yi Liu,Fanyu Wang,Fei Xie,Jiamin Zheng,Jintong Lan,Furong Guo,Yifei Sun,Lizhi Zhang,Xiao Liu
The degradation of chlorine-containing volatile organic compounds (Cl–VOCs) utilizing catalytic combustion technology is subject to the paradox of toxic byproduct formation and catalyst chlorine poisoning. Herein, a CaO-assisted strategy is proposed to resolve the awkward stuff for improving the catalytic combustion performance of chlorobenzene on SmMn2O5. The CaO-collaborated SmMn2O5 exhibits a significant decrease in T90 by 142 and 125 °C compared with unmodified and inert SiO2-composited SmMn2O5, respectively. The integrated characterization results confirm that CaO collaboration causes electron transfer from CaO to SmMn2O5, resulting in a reduction of the orbital overlap between Mn and O atoms to activate lattice oxygen (Olatt). The activated Olatt enables chlorobenzene to combust completely at a lower temperature of 275 °C at which toxic byproducts are not generated. Furthermore, the switching of the dechlorination site from SmMn2O5 to CaO avoids chlorine poisoning of active sites on SmMn2O5 and thus endows CaO-collaborated SmMn2O5 with prominent stability.
The high salinity and coexistence of scaling ions (Ca 2+ , Mg 2+ , HCO 3 − ) in wastewater challenge the efficacy and durability of palladium (Pd)-mediated electrocatalytic hydrodechlorination (EHDC) reaction for chlorinated organic pollutant detoxification, due to the accompanying Cl − poisoning at Pd sites and scaling on electrode. In a concentrated NaCl solution (5.8 g L − 1 ) with Ca 2+ (80.0 mg L − 1 ), Mg 2+ (30.0 mg L − 1 ) and HCO 3 − (180.0 mg L − 1 ), the EHDC efficiency of Pd towards 2,4-dichlorophenol decreases significantly from 67.8% to 33.1% in 72.0 h of reaction, and the electrode is covered with layers of fluffy aragonite precipitate. Herein we demonstrate the inclusion of a commercial antiscalant 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC) can prevent both scale formation and Cl − poisoning, leading to an efficient and steady EHDC process. A mechanistic study reveals that the unique dual function of PBTC primarily originates from the bearing phosphonate and carboxyl groups. With the large affinity of these groups (especially the phosphonate group) for scaling cations and Pd, the PBTC can chelate and stabilize the scaling cations in water and replace Cl − at Pd surface. It can also release protons, and trigger the formation of more electron-deficient Pd δ+ species via PBTC-Pd binding, leading to an enhanced EHDC. This work provides effective solutions to the scaling/poisoning issues that commonly encountered in real wastewater and paves a solid road for EHDC application in pollution abatement.
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