The degradation of an azo dye, acid orange 7 (AO7), caused by different high voltage pulsed electrical discharge modes (spark, streamer and corona discharge) induced by the various initial conductivities was investiga...The degradation of an azo dye, acid orange 7 (AO7), caused by different high voltage pulsed electrical discharge modes (spark, streamer and corona discharge) induced by the various initial conductivities was investigated. A new type of pulsed high voltage source with thyratron switch and Blumlein pulse forming net (BPFN) was used. The typical discharge waveforms of voltage, current, power, pulse en-ergy and the pictures of spark, streamer and corona discharge modes were presented. The results in-dicated that pulsed electrical discharges led to complete decolorization and substantial decrease of the chemical oxygen demand (COD) of the dye solution. The main intermediate products were monitored by GC-MS. The discharge modes changed from spark to streamer and to corona discharge, and the streamer length decreased with the liquid conductivity increasing. At a constant input power, the peak voltage, peak current, peak power and energy per pulse of the three discharge modes ranked in the following order: spark > streamer > corona. The effective energy transfer efficiency of AO7 removal was higher for spark discharge (57.2%) than for streamer discharge (40.4%) and corona discharge (27.6%). Moreover, the energy utilization efficiency of AO7 removal for spark discharge was 1.035×10^(-9) mol/J, and for streamer and corona discharge they were 0.646×10^(-9) and 0.589×10^(-9) mol/J. Both the energy transfer efficiency and the energy utilization efficiency of spark discharge were the highest.展开更多
Liquid conductivity (EC) measurement was conducted for the samples collected from several snow pits and ice cores over the Qinghai-Xizang (Tibet) Plateau, with their time range covering seasonal, decadal and centennia...Liquid conductivity (EC) measurement was conducted for the samples collected from several snow pits and ice cores over the Qinghai-Xizang (Tibet) Plateau, with their time range covering seasonal, decadal and centennial scales. Unlike the previous attention mostly focused on the acidity (H+) responding to the solid conductance (ECM) of glacial ice, we introduce the alkalinity (OH?) of snow and ice to show how it responds to EC. Strong linear relationship was established between EC and OH? for these snow pits and ice cores. Positive correlation is also established between EC and major cations (Ca2+, Mg2+, Na+ and K+). Since the cations are known as the proxies for the intensity of mineral dust influx onto glaciers of the northern Qinghai-Xizang Plateau, we believe that EC could be used as an indicator for the history of dust input in deep ice core study. In fact, records in Guliya ice core since the Little Ice Age (LIA) indicate that dust load in glacier may depend on the combination of temperature and humidity. "Cold-dry" combination favors the dust arising, and results in higher EC and OH- values, while "warm-wet" combination prevents dust form and EC and OH- values are lower. In the past century, with the atmospheric warming and precipitation increasing over the northern plateau, which means an atmospheric condition of dust decreasing, both EC and OH- displayed rapid decline.展开更多
基金National Natural Science Foundation of China (Grant Nos.20336030, 90610005,20576120 and U0633003)Distinguished Youth Foundation of Zhejiang Province (Grant No.RC 02060)
文摘The degradation of an azo dye, acid orange 7 (AO7), caused by different high voltage pulsed electrical discharge modes (spark, streamer and corona discharge) induced by the various initial conductivities was investigated. A new type of pulsed high voltage source with thyratron switch and Blumlein pulse forming net (BPFN) was used. The typical discharge waveforms of voltage, current, power, pulse en-ergy and the pictures of spark, streamer and corona discharge modes were presented. The results in-dicated that pulsed electrical discharges led to complete decolorization and substantial decrease of the chemical oxygen demand (COD) of the dye solution. The main intermediate products were monitored by GC-MS. The discharge modes changed from spark to streamer and to corona discharge, and the streamer length decreased with the liquid conductivity increasing. At a constant input power, the peak voltage, peak current, peak power and energy per pulse of the three discharge modes ranked in the following order: spark > streamer > corona. The effective energy transfer efficiency of AO7 removal was higher for spark discharge (57.2%) than for streamer discharge (40.4%) and corona discharge (27.6%). Moreover, the energy utilization efficiency of AO7 removal for spark discharge was 1.035×10^(-9) mol/J, and for streamer and corona discharge they were 0.646×10^(-9) and 0.589×10^(-9) mol/J. Both the energy transfer efficiency and the energy utilization efficiency of spark discharge were the highest.
基金This work was supported by the Chinese National Basic Research Programme and CAS Innovation Project (Grant Nos. G1998040802 and CACX210046).
文摘Liquid conductivity (EC) measurement was conducted for the samples collected from several snow pits and ice cores over the Qinghai-Xizang (Tibet) Plateau, with their time range covering seasonal, decadal and centennial scales. Unlike the previous attention mostly focused on the acidity (H+) responding to the solid conductance (ECM) of glacial ice, we introduce the alkalinity (OH?) of snow and ice to show how it responds to EC. Strong linear relationship was established between EC and OH? for these snow pits and ice cores. Positive correlation is also established between EC and major cations (Ca2+, Mg2+, Na+ and K+). Since the cations are known as the proxies for the intensity of mineral dust influx onto glaciers of the northern Qinghai-Xizang Plateau, we believe that EC could be used as an indicator for the history of dust input in deep ice core study. In fact, records in Guliya ice core since the Little Ice Age (LIA) indicate that dust load in glacier may depend on the combination of temperature and humidity. "Cold-dry" combination favors the dust arising, and results in higher EC and OH- values, while "warm-wet" combination prevents dust form and EC and OH- values are lower. In the past century, with the atmospheric warming and precipitation increasing over the northern plateau, which means an atmospheric condition of dust decreasing, both EC and OH- displayed rapid decline.
