Nanometer zinc oxide （ZnO） powders were used as a catalyst to enhance the ozonation for the degradation of dichloroacetic acid （DCAA） in aqueous solution. The batch experiments were carded out to investigate the e...Nanometer zinc oxide （ZnO） powders were used as a catalyst to enhance the ozonation for the degradation of dichloroacetic acid （DCAA） in aqueous solution. The batch experiments were carded out to investigate the effects of key factors such as catalyst dosage, ozone dosage, solution pH and tert-butyl alcohol （t-BuOH） on the degradation efficiency of DCAA. Density functional theory （DFT） was adopted to explore the mechanism of generating hydroxyl radical （＇OH） on the ZnO surface. The results showed that adsorption and ozonation processes were not effective for DCAA removal, and the addition of ZnO catalyst improved the degradation efficiency of DCAA during ozonation, which caused an increase of 22.8% for DCAA decomposition compared to the case of ozonation alone after 25 min. Under the same experimental conditions, the DCAA decomposition was enhanced by increasing catalyst dosage from 100 to 500 mg/L and ozone dosage from 0.83 to 3.2 mg/L. The catalytic ozonation process is more pronounced than the ozonation process alone at pH 3.93, 6.88, and 10. With increasing the concentration of t-BuOH from 10 to 200 rag/L, the degradation of DCAA was significantly inhibited in the process of catalytic ozonation, indicating that ZnO catalytic ozonation followed ＂OH reaction mechanism. Based on the experimental results and DFT analysis, it is deduced that the generation of ＂OH on the ZnO surface is ascribed to the adsorption of molecule ozone followed by the interaction of adsorbed ozone with active sites of the catalyst surface. It is also concluded that ZnO may be an effective catalyst for DCAA removal, which could promote the formation of .OH derived from the catalytic decomposition of ozone.展开更多
The contents of acetic acid,chloroacetic acid and dichloroacetic acid as well as chloride ion in the chemicals were rapidly determined by ion chromatography.The analytical conditions were also optimized ,consequently,...The contents of acetic acid,chloroacetic acid and dichloroacetic acid as well as chloride ion in the chemicals were rapidly determined by ion chromatography.The analytical conditions were also optimized ,consequently,excellent precision and analytical results could be obtained.The detection limits of each component were less than 2.0×10 -3 μg/ml with the recorveries within range of 95% and 104%.展开更多
An anion-exchange chromatography method combined solid phase extraction （SPE） was developed for the simultaneous analysis of glycolate acid （GL）, monochloroacetic acid （MCA） and dichloroacetic acid （DCA） in sy...An anion-exchange chromatography method combined solid phase extraction （SPE） was developed for the simultaneous analysis of glycolate acid （GL）, monochloroacetic acid （MCA） and dichloroacetic acid （DCA） in synthetical betaine products. The analytes and unknown anionic impurities were well separated on a Metrosep A supp5 anion-exchange column （150 mm×4 mm） with 2.0 mmol/L Na2CO3＋2.0 mmol/L NaHCO3 solution as eluent. Suppressed conductivity detection was used. A strong cation exchange （SCX） solid phase extraction （SPE） cartridge was used to reduce the concentration of matrix betaine and a Cleanert IC-Ag pretreatment cartridge was used to remove high Cl- concentration. The detection limits of GL, MCA and DCA were 0.09, 0.017 and 0.05 μg/L, respectively. The relative standard deviations （RSDs） of the retention times and peak areas were less than 0.09% and 0.49%, respectively. The recoveries of the three analytes were between 90.6% and 100.8%. The analytical results showed that GL and DCA were present in high concentration and no MCA was found when the proposed ion chromatography method was applied to three synthetical betaine samples. The proposed method is simple, sensitive and timesaving, and is also suitable for routine analysis in quality control of synthetical betaine products.展开更多
基金support by the National Natural Science Foundation of China(No.50638020)the High Technology Research and Development Program(863)of China (No.2007AA06Z339)+1 种基金the National Important Science and Technology Specific Project for the Control and Treatment of Water Pollution(No.2009ZX07424-004)the National Key Technology R&D Program during the 11th Five-Year Plan Period(No.2006BAJ08B02)
文摘Nanometer zinc oxide （ZnO） powders were used as a catalyst to enhance the ozonation for the degradation of dichloroacetic acid （DCAA） in aqueous solution. The batch experiments were carded out to investigate the effects of key factors such as catalyst dosage, ozone dosage, solution pH and tert-butyl alcohol （t-BuOH） on the degradation efficiency of DCAA. Density functional theory （DFT） was adopted to explore the mechanism of generating hydroxyl radical （＇OH） on the ZnO surface. The results showed that adsorption and ozonation processes were not effective for DCAA removal, and the addition of ZnO catalyst improved the degradation efficiency of DCAA during ozonation, which caused an increase of 22.8% for DCAA decomposition compared to the case of ozonation alone after 25 min. Under the same experimental conditions, the DCAA decomposition was enhanced by increasing catalyst dosage from 100 to 500 mg/L and ozone dosage from 0.83 to 3.2 mg/L. The catalytic ozonation process is more pronounced than the ozonation process alone at pH 3.93, 6.88, and 10. With increasing the concentration of t-BuOH from 10 to 200 rag/L, the degradation of DCAA was significantly inhibited in the process of catalytic ozonation, indicating that ZnO catalytic ozonation followed ＂OH reaction mechanism. Based on the experimental results and DFT analysis, it is deduced that the generation of ＂OH on the ZnO surface is ascribed to the adsorption of molecule ozone followed by the interaction of adsorbed ozone with active sites of the catalyst surface. It is also concluded that ZnO may be an effective catalyst for DCAA removal, which could promote the formation of .OH derived from the catalytic decomposition of ozone.
文摘The contents of acetic acid,chloroacetic acid and dichloroacetic acid as well as chloride ion in the chemicals were rapidly determined by ion chromatography.The analytical conditions were also optimized ,consequently,excellent precision and analytical results could be obtained.The detection limits of each component were less than 2.0×10 -3 μg/ml with the recorveries within range of 95% and 104%.
文摘An anion-exchange chromatography method combined solid phase extraction （SPE） was developed for the simultaneous analysis of glycolate acid （GL）, monochloroacetic acid （MCA） and dichloroacetic acid （DCA） in synthetical betaine products. The analytes and unknown anionic impurities were well separated on a Metrosep A supp5 anion-exchange column （150 mm×4 mm） with 2.0 mmol/L Na2CO3＋2.0 mmol/L NaHCO3 solution as eluent. Suppressed conductivity detection was used. A strong cation exchange （SCX） solid phase extraction （SPE） cartridge was used to reduce the concentration of matrix betaine and a Cleanert IC-Ag pretreatment cartridge was used to remove high Cl- concentration. The detection limits of GL, MCA and DCA were 0.09, 0.017 and 0.05 μg/L, respectively. The relative standard deviations （RSDs） of the retention times and peak areas were less than 0.09% and 0.49%, respectively. The recoveries of the three analytes were between 90.6% and 100.8%. The analytical results showed that GL and DCA were present in high concentration and no MCA was found when the proposed ion chromatography method was applied to three synthetical betaine samples. The proposed method is simple, sensitive and timesaving, and is also suitable for routine analysis in quality control of synthetical betaine products.
