| Summary: | 碩士 === 淡江大學 === 水資源及環境工程學系 === 87 === Ⅰ. Determination of the Chemical Oxgen Demand in the Wastewater Using Microwave Energy — The Comparison Between the Closed Method And the Open Focus Reflux Method.
In environmental analytic chemistry microwave-assisted methods for sample preparation have been increased rapidly in recent years .The closed vessel method and open focus reflux method were used for the determination of chemical oxygen demand (COD) in the digestion-oxidation step which was by using microwave energy.
The goals of this study are to develop the mercury-free microwave assisted,digestion for COD determination and to compare between the open focus microwave and the closed vessel sample preparation methods.
The optimized conditions for the closed vessel method are： sample, 5ml； sulfuric acid(0.55﹪Ag+), 7ml；0.0705M silver nitrate,1ml； 0.0417M potassium dichromate, 2ml； power(using domestic microwave oven): 512 W, reaction time: 5mins. The optimized conditions for the open focus reflux method are： sample, 5ml； sulfuric acid(0.55﹪Ag+), 7ml；0.0705M silver nitrate,1ml； 0.0417M potassium dichromate, 2ml； power(using open focus microwave oven): 300W, reaction time: 5mins. The average recovery of the closed vessel method for quality control samples were 98.3﹪and S. D. 1.8﹪.The average recovery of the open focus reflux method for quality control samples was 98.7﹪and S. D. 1.2﹪The ratio between COD values, determined by the open focus method and the closed vessel methods is 0.9360. The results show that both methods are comparable.
Ⅱ. Determination the Efficiency of Detection Chemical and Physical Components for the Rainwater in Chung-Li Area by Acid rain Automatic Monitoring.
The aims of this study are to characterize the rainfalls by physical and chemical parameter Chung-Li area and to compare the data from acid rain monitor with the results obtained in the laboratory.
The physical and chemical parameters included temperature, rainfalls intensity, electrical conductivity, turbidity, pH value cation concentration (Na+,K+,NH4+,Ca2+,Mg2+) and anion concentration( Cl-,NO3-,SO42-).The results showed that the pH values, temperature, rainfalls intensity and electrical conductivity were very good as compared with that from the lab. However, the sulfate and nitrate by acid rain monitor, s spectrophotometer were poor probably because of bubbles and contamination in the line .
Ion chromatography with conductivity detector has been used to determine cations and anions separately. The nitric acid solution(0.5mM) was used with cation-exchange column (MCI GEL SCK01) having low cation exchange capacities. The dilute 3mM Vanillin Acid and 2.8mM N-Methydiethanolamine(pH6.2) have been the main eluent species used for anions.
The result shows the range of ratios (SO42 /NO3-)was 1~5 and the range of pH values were 4~7 for the rainwater in Chung-Li area.
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