The degradation of metoprolol(MTP)by the UV/sulfite with oxygen as an advanced reduction process(ARP)and that without oxygen as an advanced oxidation process(AOP)was comparatively studied herein.The degradation of MTP...The degradation of metoprolol(MTP)by the UV/sulfite with oxygen as an advanced reduction process(ARP)and that without oxygen as an advanced oxidation process(AOP)was comparatively studied herein.The degradation of MTP by both processes followed the first-order rate law with comparable reaction rate constants of 1.50×10^(-3)sec^(−1)and 1.20×10^(-3)sec^(−1),respectively.Scavenging experiments demonstrated that both e^(−)_(aq)and H·played a crucial role in MTP degradation by the UV/sulfite as an ARP,while SO_(4)^(·−)was the dominant oxidant in the UV/sulfite AOP.The degradation kinetics of MTP by the UV/sulfite as an ARP and AOP shared a similar pH dependence with a minimum rate obtained around pH 8.The results could be well explained by the pH impacts on the MTP speciation and sulfite species.Totally six transformation products(TPs)were identified from MTP degradation by the UV/sulfite ARP,and two additional ones were detected in the UV/sulfite AOP.The benzene ring and ether groups of MTP were proposed as the major reactive sites for both processes based on molecular orbital calculations by density functional theory(DFT).The similar degradation products of MTP by the UV/sulfite process as an ARP and AOP indicated that e^(−)_(aq)/H·and SO_(4)^(·−)might share similar reaction mechanisms,primarily including hydroxylation,dealkylation,and H abstraction.The toxicity of MTP solution treated by the UV/sulfite AOP was calculated to be higher than that in the ARP by the Ecological Struc-ture Activity Relationships(ECOSAR)software,due to the accumulation of TPs with higher toxicity.展开更多
This article, for the first time, provides a novel advanced oxidation process based on sulfate radical （SO^4·-） to degrade organic pollutants in wastewater： microwave （MW）-activated persulfate oxidation （AP...This article, for the first time, provides a novel advanced oxidation process based on sulfate radical （SO^4·-） to degrade organic pollutants in wastewater： microwave （MW）-activated persulfate oxidation （APO） with or without active carbon （AC）. Azo dye acid Orange 7 （AO7） is used as a model compound to investigate the high reactivity of MW-APO. It is found that AO7 （up to 1000 mg/L） is completely decolorized within 5-7 min under an 800 W MW furnace assisted-APO. In the presence of chloride ion （up to 0.50 mol/L）, the decolorization is still 100% completed, though delayed for about 1-2 min. Experiments are made to examine the enhancement by AC. It is exciting to find that the 100% decolorization of AO7 （500 mg/L） is achieved within 3 min by MW-APO using 1.0 g/L AC as catalyst, while the degradation efficiency maintains at 50% by MW energy without persulfate after about 5 min. Besides the destruction of visible light chromophore band of AO7 （484 nm）, during MW-APO, two bands in the ultraviolet region （228 nm and 310 nm） are rapidly broken down. The removal of COD is about 83%-95% for 500 mg/L AO7. SO^4·- is identified with quenching studies using specific alcohols. Both SO^4·- and ·OH could degrade AO7, but SO^4·- plays the dominant role. In a word, MW-APO AC is a new catalytic combustion technology for destruction of organic contamination even for high concentration.展开更多
Nano-TiO2 photocatalytic oxidation was used to perform the advanced treatment of biologically treated chemical comprehensive wastewater. The effects of reaction time,nano-TiO2 dosage and initial p H of the wastewater ...Nano-TiO2 photocatalytic oxidation was used to perform the advanced treatment of biologically treated chemical comprehensive wastewater. The effects of reaction time,nano-TiO2 dosage and initial p H of the wastewater on the removal rate of COD were tested. The GC/MS and EEM techniques were used to qualitatively analyze organic compounds in the wastewater before and after treatment. The result showed that after the biologically treated chemical comprehensive wastewater was treated by nano-TiO2 photocatalytic oxidation under the conditions of reaction time 3 h,nano-TiO2 dosage 8 g/L,and pH 8. 0,the effluent COD was 61. 9 mg/L and its removal rate was 63. 8%. Additionally,the species of organic pollutants reduced from 12 to 6. Meanwhile,the content of humic-like and fulvic-like substances dropped dramatically.展开更多
A method for oxidative degradation of 1,4-dioxane （1,4-D） in waste water using a combination of ozone oxidation with UV irradiation （ozone/UV） treatment was investigated. The results showed that 1,4-D was degraded...A method for oxidative degradation of 1,4-dioxane （1,4-D） in waste water using a combination of ozone oxidation with UV irradiation （ozone/UV） treatment was investigated. The results showed that 1,4-D was degraded by ozone/UV treatment up to 90 min. The optimum concentration for the injected ozone gas was about 40 g·m^3 under a constant level of UV irradiation. Furthermore, solid phase extraction and GC-MS analysis showed no specific or reproducible peaks due to by-products of 1,4-D. It was therefore concluded that 1,4-D was completely degraded by ozone/UV treatment. In contrast, the amount of 1,4-D remaining decreased slowly in the presence of HCOf or CI. It was suggested that the degradation of 1,4-D, which results from .OH oxidation, was retarded by the presence of HCO3 or CI, which act as radical scavengers.展开更多
Sulfur removal from liquid fuels has increased in importance in recent years. Although hydrodesulfurization is the usual method for removing sulfur, the elimination of thiophene compounds using this process is difficu...Sulfur removal from liquid fuels has increased in importance in recent years. Although hydrodesulfurization is the usual method for removing sulfur, the elimination of thiophene compounds using this process is difficult. Photocatalysis is an alternative method being developed for thiophene removal at ambient conditions. Among semiconductors, titania has shown good potential as a photo-catalyst; however, quick recombination of electron holes hinders its commercial use. One way to decrease the recombination rate is to combine carbon nanotubes with a semiconductor. In this work, multiwall carbon nanotube （MWCNT） / titania composites were prepared with different mass ratios of MWCNT to titania using tetraethyl orthotitanate （TEOT） and titanium tetra isopropoxide （TTIP） as precursors of titania. Dibenzothiophene （DBT） photocatalytic removal from n-hexane was measured in both the presence and absence of oxygen. The results indicated that the best removal occurred when the MWCNT to titania ratio was 1. When the ratio exceeded this number, DBT removal efficiency decreased due to light scattering. Also, the composites prepared by TEOT exhibited better efficiency in DBT removal. The research findings suggested that the obtained composite was a visible light active photocatalyst and exhibited better performance in the presence of oxygen. Kinetics of photocatalytic DBT removal was a first-order reaction with removal rate constant 0.7 h–1 obtained at optimum conditions.展开更多
基金This study was supported by the Guangdong introducing innovative and entrepreneurial teams(No.2019ZT08L213)the Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)(No.GML2019ZD0403)+2 种基金the National Natural Science Foundation of China(Nos.51979044 and 42177045)the Young Talent Project of Beijing Normal University at Zhuhai(No.310432101)We also thank the support received from China Scholarship Council(CSC)for providing a graduate fellowship to Y.C.(No.202006120356).
文摘The degradation of metoprolol(MTP)by the UV/sulfite with oxygen as an advanced reduction process(ARP)and that without oxygen as an advanced oxidation process(AOP)was comparatively studied herein.The degradation of MTP by both processes followed the first-order rate law with comparable reaction rate constants of 1.50×10^(-3)sec^(−1)and 1.20×10^(-3)sec^(−1),respectively.Scavenging experiments demonstrated that both e^(−)_(aq)and H·played a crucial role in MTP degradation by the UV/sulfite as an ARP,while SO_(4)^(·−)was the dominant oxidant in the UV/sulfite AOP.The degradation kinetics of MTP by the UV/sulfite as an ARP and AOP shared a similar pH dependence with a minimum rate obtained around pH 8.The results could be well explained by the pH impacts on the MTP speciation and sulfite species.Totally six transformation products(TPs)were identified from MTP degradation by the UV/sulfite ARP,and two additional ones were detected in the UV/sulfite AOP.The benzene ring and ether groups of MTP were proposed as the major reactive sites for both processes based on molecular orbital calculations by density functional theory(DFT).The similar degradation products of MTP by the UV/sulfite process as an ARP and AOP indicated that e^(−)_(aq)/H·and SO_(4)^(·−)might share similar reaction mechanisms,primarily including hydroxylation,dealkylation,and H abstraction.The toxicity of MTP solution treated by the UV/sulfite AOP was calculated to be higher than that in the ARP by the Ecological Struc-ture Activity Relationships(ECOSAR)software,due to the accumulation of TPs with higher toxicity.
文摘This article, for the first time, provides a novel advanced oxidation process based on sulfate radical （SO^4·-） to degrade organic pollutants in wastewater： microwave （MW）-activated persulfate oxidation （APO） with or without active carbon （AC）. Azo dye acid Orange 7 （AO7） is used as a model compound to investigate the high reactivity of MW-APO. It is found that AO7 （up to 1000 mg/L） is completely decolorized within 5-7 min under an 800 W MW furnace assisted-APO. In the presence of chloride ion （up to 0.50 mol/L）, the decolorization is still 100% completed, though delayed for about 1-2 min. Experiments are made to examine the enhancement by AC. It is exciting to find that the 100% decolorization of AO7 （500 mg/L） is achieved within 3 min by MW-APO using 1.0 g/L AC as catalyst, while the degradation efficiency maintains at 50% by MW energy without persulfate after about 5 min. Besides the destruction of visible light chromophore band of AO7 （484 nm）, during MW-APO, two bands in the ultraviolet region （228 nm and 310 nm） are rapidly broken down. The removal of COD is about 83%-95% for 500 mg/L AO7. SO^4·- is identified with quenching studies using specific alcohols. Both SO^4·- and ·OH could degrade AO7, but SO^4·- plays the dominant role. In a word, MW-APO AC is a new catalytic combustion technology for destruction of organic contamination even for high concentration.
文摘Nano-TiO2 photocatalytic oxidation was used to perform the advanced treatment of biologically treated chemical comprehensive wastewater. The effects of reaction time,nano-TiO2 dosage and initial p H of the wastewater on the removal rate of COD were tested. The GC/MS and EEM techniques were used to qualitatively analyze organic compounds in the wastewater before and after treatment. The result showed that after the biologically treated chemical comprehensive wastewater was treated by nano-TiO2 photocatalytic oxidation under the conditions of reaction time 3 h,nano-TiO2 dosage 8 g/L,and pH 8. 0,the effluent COD was 61. 9 mg/L and its removal rate was 63. 8%. Additionally,the species of organic pollutants reduced from 12 to 6. Meanwhile,the content of humic-like and fulvic-like substances dropped dramatically.
文摘A method for oxidative degradation of 1,4-dioxane （1,4-D） in waste water using a combination of ozone oxidation with UV irradiation （ozone/UV） treatment was investigated. The results showed that 1,4-D was degraded by ozone/UV treatment up to 90 min. The optimum concentration for the injected ozone gas was about 40 g·m^3 under a constant level of UV irradiation. Furthermore, solid phase extraction and GC-MS analysis showed no specific or reproducible peaks due to by-products of 1,4-D. It was therefore concluded that 1,4-D was completely degraded by ozone/UV treatment. In contrast, the amount of 1,4-D remaining decreased slowly in the presence of HCOf or CI. It was suggested that the degradation of 1,4-D, which results from .OH oxidation, was retarded by the presence of HCO3 or CI, which act as radical scavengers.
文摘Sulfur removal from liquid fuels has increased in importance in recent years. Although hydrodesulfurization is the usual method for removing sulfur, the elimination of thiophene compounds using this process is difficult. Photocatalysis is an alternative method being developed for thiophene removal at ambient conditions. Among semiconductors, titania has shown good potential as a photo-catalyst; however, quick recombination of electron holes hinders its commercial use. One way to decrease the recombination rate is to combine carbon nanotubes with a semiconductor. In this work, multiwall carbon nanotube （MWCNT） / titania composites were prepared with different mass ratios of MWCNT to titania using tetraethyl orthotitanate （TEOT） and titanium tetra isopropoxide （TTIP） as precursors of titania. Dibenzothiophene （DBT） photocatalytic removal from n-hexane was measured in both the presence and absence of oxygen. The results indicated that the best removal occurred when the MWCNT to titania ratio was 1. When the ratio exceeded this number, DBT removal efficiency decreased due to light scattering. Also, the composites prepared by TEOT exhibited better efficiency in DBT removal. The research findings suggested that the obtained composite was a visible light active photocatalyst and exhibited better performance in the presence of oxygen. Kinetics of photocatalytic DBT removal was a first-order reaction with removal rate constant 0.7 h–1 obtained at optimum conditions.
