The performance of supported catalysts is significantly affected by the dispersion degree of the active components on the support.In this study,citric acid(CA)was used as a modifier to prepare Al_(2)O_(3)supported Mn-...The performance of supported catalysts is significantly affected by the dispersion degree of the active components on the support.In this study,citric acid(CA)was used as a modifier to prepare Al_(2)O_(3)supported Mn-Ce oxides(Mn-Ce/CA-Al_(2)O_(3))by the impregnation-calcination method.The characterization results showed that adding citric acid enhanced the dispersion of Mn-Ce oxides on the support,rendering Mn-Ce/CA-Al_(2)O_(3)with a larger specific surface area and abundant surface hydroxyl groups,thereby providing more reaction sites for catalytic ozonation.The Mn-Ce/CA-Al_(2)O_(3)exhibited excellent catalytic ozonation performance in degrading Reactive Black 5(RB5)dye.It achieved nearly complete decolorization of RB5 within 60 min,with a COD removal efficiency of 60%,which was superior to the sole ozonation(30%).Furthermore,the Mn-Ce/CA-Al_(2)O_(3)system demonstrated significant degradation of RB5 over a wide pH range of 3e11.Based on the XPS and EPR analysis results,a preliminary mechanism of catalytic ozonation over the Mn-Ce/CA-Al_(2)O_(3)was proposed.The redox cycle of Mn^(3+)/Mn^(4+)and Ce^(3+)/Ce^(4+)effectively accelerated the electron transfer process,thus promoting the generation of reactive oxygen species(ROS)and improving the degradation of RB5.Meanwhile,the Mn-Ce/CA-Al_(2)O_(3)exhibited superior catalytic stability and effective treatment capabilities for real dye wastewater.展开更多
To reduce energy costs,minimize secondary pollution from undecomposed ozone,and improve the efficiency of ozone use,a novel process of cycled storage‐ozone catalytic oxidation(OZCO)was employed to remove formaldehyde...To reduce energy costs,minimize secondary pollution from undecomposed ozone,and improve the efficiency of ozone use,a novel process of cycled storage‐ozone catalytic oxidation(OZCO)was employed to remove formaldehyde(HCHO)at low concentrations in air.We applied Al2O3‐supported manganese oxide(MnOx)catalysts to this process,and examined the HCHO adsorption capacity and OZCO performance over the MnOx catalysts.Owing to the high dispersion of MnOx and low oxidation state of manganese,the MnOx/Al2O3catalysts with a manganese acetate precursor and10%‐Mn loading showed good performance in both storage and OZCO stages.The presence of H2O led to a decrease of the HCHO adsorption capacity owing to competitive adsorption between moisture and HCHO at the storage stage;however,high relative humidity(RH)favored complete conversion of stored HCHO to CO2at the OZCO stage and contributed to an excellent carbonbalance.Four low concentration HCHO storage‐OZCO cycles with a long HCHO storage period and relatively short OZCO period were successfully performed over the selected MnOx/Al2O3catalyst at room temperature and a RH of50%,demonstrating that the proposed storage‐OZCO process is an economical,reliable,and promising technique for indoor air purification.展开更多
Dielectric barrier discharge （DBD） plasma was utilized to oxidize NO contained in the exhaust gas to NO2, ultimately improve the selective catalytic reduction of nitrogen oxides （NOx）. In the one case, DBD was cre...Dielectric barrier discharge （DBD） plasma was utilized to oxidize NO contained in the exhaust gas to NO2, ultimately improve the selective catalytic reduction of nitrogen oxides （NOx）. In the one case, DBD was created directly in the exhaust gas （direct application）, and in the an other case, ozone produced by DBD was injected into the exhaust gas （indirect application）. A comparative study between such direct and indirect applications of DBD plasma was made in terms of the NOx removal efficiency and the energy consumption. The NO2 content in the exhaust gas was changed by the voltage applied to the DBD device （for direct application） or by the amount of ozone added to the exhaust gas （for indirect application）. In both cases, NO was easily oxidized to NO2, and the change in NO2 content largely affected the NOx removal performance of the catalytic reactor placed downstream, where both NO and NO2 were reduced to N2 in the presence of ammonia as the reducing agent. The experiments were primarily concerned with the effect of reaction temperature on the catalytic NOx reduction at various NO2 contents. The direct and indirect applications of DBD were found to remarkably improve the catalytic NOx reduction, especially at low temperatures.展开更多
Novel Mn–Fe–Mg-and Mn–Fe–Ce-loaded alumina（Mn–Fe–Mg/Al2O3 and Mn–Fe–Ce/Al2O3） were developed to catalytically ozonate reverse osmosis concentrates generated from petroleum refinery wastewaters（PRW-ROC）. Hi...Novel Mn–Fe–Mg-and Mn–Fe–Ce-loaded alumina（Mn–Fe–Mg/Al2O3 and Mn–Fe–Ce/Al2O3） were developed to catalytically ozonate reverse osmosis concentrates generated from petroleum refinery wastewaters（PRW-ROC）. Highly dispersed 100–300-nm deposits of composite multivalent metal oxides of Mn（Mn^2＋）, Mn^3＋,and Mn^4＋, Fe（Fe^2＋）and Fe^3＋ and Mg（Mg^2＋）, or Ce（Ce^4＋） were achieved on Al2O3 supports. The developed Mn–Fe–Mg/Al2O3 and Mn–Fe–Ce/Al2O3 exhibited higher catalytic activity during the ozonation of PRW-ROC than Mn–Fe/Al2O3, Mn/Al2O-3, Fe/Al2O3, and Al2O3. Chemical oxygen demand removal by Mn–Fe–Mg/Al2O3-or Mn–Fe–Ce/Al2O3-catalyzed ozonation increased by 23.9% and23.2%, respectively, in comparison with single ozonation.Mn–Fe–Mg/Al2O3 and Mn–Fe–Ce/Al2O3 notably promoted áOH generation and áOH-mediated oxidation. This study demonstrated the potential use of composite metal oxide-loaded Al2O3 in advanced treatment of bio-recalcitrant wastewaters.展开更多
基金supported by the National Key Research and Development Program(2023YFC3207003)the National Natural Science Foundation of China(51878448).
文摘The performance of supported catalysts is significantly affected by the dispersion degree of the active components on the support.In this study,citric acid(CA)was used as a modifier to prepare Al_(2)O_(3)supported Mn-Ce oxides(Mn-Ce/CA-Al_(2)O_(3))by the impregnation-calcination method.The characterization results showed that adding citric acid enhanced the dispersion of Mn-Ce oxides on the support,rendering Mn-Ce/CA-Al_(2)O_(3)with a larger specific surface area and abundant surface hydroxyl groups,thereby providing more reaction sites for catalytic ozonation.The Mn-Ce/CA-Al_(2)O_(3)exhibited excellent catalytic ozonation performance in degrading Reactive Black 5(RB5)dye.It achieved nearly complete decolorization of RB5 within 60 min,with a COD removal efficiency of 60%,which was superior to the sole ozonation(30%).Furthermore,the Mn-Ce/CA-Al_(2)O_(3)system demonstrated significant degradation of RB5 over a wide pH range of 3e11.Based on the XPS and EPR analysis results,a preliminary mechanism of catalytic ozonation over the Mn-Ce/CA-Al_(2)O_(3)was proposed.The redox cycle of Mn^(3+)/Mn^(4+)and Ce^(3+)/Ce^(4+)effectively accelerated the electron transfer process,thus promoting the generation of reactive oxygen species(ROS)and improving the degradation of RB5.Meanwhile,the Mn-Ce/CA-Al_(2)O_(3)exhibited superior catalytic stability and effective treatment capabilities for real dye wastewater.
基金supported by the National Natural Science Foundation of China(21673030)the Higher Education Development Fund(for Collaborative Innovation Center) of Liaoning Province,China(20110217004)~~
文摘To reduce energy costs,minimize secondary pollution from undecomposed ozone,and improve the efficiency of ozone use,a novel process of cycled storage‐ozone catalytic oxidation(OZCO)was employed to remove formaldehyde(HCHO)at low concentrations in air.We applied Al2O3‐supported manganese oxide(MnOx)catalysts to this process,and examined the HCHO adsorption capacity and OZCO performance over the MnOx catalysts.Owing to the high dispersion of MnOx and low oxidation state of manganese,the MnOx/Al2O3catalysts with a manganese acetate precursor and10%‐Mn loading showed good performance in both storage and OZCO stages.The presence of H2O led to a decrease of the HCHO adsorption capacity owing to competitive adsorption between moisture and HCHO at the storage stage;however,high relative humidity(RH)favored complete conversion of stored HCHO to CO2at the OZCO stage and contributed to an excellent carbonbalance.Four low concentration HCHO storage‐OZCO cycles with a long HCHO storage period and relatively short OZCO period were successfully performed over the selected MnOx/Al2O3catalyst at room temperature and a RH of50%,demonstrating that the proposed storage‐OZCO process is an economical,reliable,and promising technique for indoor air purification.
文摘Dielectric barrier discharge （DBD） plasma was utilized to oxidize NO contained in the exhaust gas to NO2, ultimately improve the selective catalytic reduction of nitrogen oxides （NOx）. In the one case, DBD was created directly in the exhaust gas （direct application）, and in the an other case, ozone produced by DBD was injected into the exhaust gas （indirect application）. A comparative study between such direct and indirect applications of DBD plasma was made in terms of the NOx removal efficiency and the energy consumption. The NO2 content in the exhaust gas was changed by the voltage applied to the DBD device （for direct application） or by the amount of ozone added to the exhaust gas （for indirect application）. In both cases, NO was easily oxidized to NO2, and the change in NO2 content largely affected the NOx removal performance of the catalytic reactor placed downstream, where both NO and NO2 were reduced to N2 in the presence of ammonia as the reducing agent. The experiments were primarily concerned with the effect of reaction temperature on the catalytic NOx reduction at various NO2 contents. The direct and indirect applications of DBD were found to remarkably improve the catalytic NOx reduction, especially at low temperatures.
基金supported in part by the National Science and Technology Major Project of China (No. 2016ZX05040-003)
文摘Novel Mn–Fe–Mg-and Mn–Fe–Ce-loaded alumina（Mn–Fe–Mg/Al2O3 and Mn–Fe–Ce/Al2O3） were developed to catalytically ozonate reverse osmosis concentrates generated from petroleum refinery wastewaters（PRW-ROC）. Highly dispersed 100–300-nm deposits of composite multivalent metal oxides of Mn（Mn^2＋）, Mn^3＋,and Mn^4＋, Fe（Fe^2＋）and Fe^3＋ and Mg（Mg^2＋）, or Ce（Ce^4＋） were achieved on Al2O3 supports. The developed Mn–Fe–Mg/Al2O3 and Mn–Fe–Ce/Al2O3 exhibited higher catalytic activity during the ozonation of PRW-ROC than Mn–Fe/Al2O3, Mn/Al2O-3, Fe/Al2O3, and Al2O3. Chemical oxygen demand removal by Mn–Fe–Mg/Al2O3-or Mn–Fe–Ce/Al2O3-catalyzed ozonation increased by 23.9% and23.2%, respectively, in comparison with single ozonation.Mn–Fe–Mg/Al2O3 and Mn–Fe–Ce/Al2O3 notably promoted áOH generation and áOH-mediated oxidation. This study demonstrated the potential use of composite metal oxide-loaded Al2O3 in advanced treatment of bio-recalcitrant wastewaters.
