| Summary: | 碩士 === 淡江大學 === 水資源及環境工程學系碩士班 === 93 === A simple method for determination of chemical oxygen demand
using microwave digestion in wastewater is proposed. Chemical oxygen demand (COD) is a widely used parameter used to measure water quality, as well as to control the treatment process. It is one of the important index in water monitoring. This parameter is defined as the amount of oxygen required for, or equivalent to, the oxidation of all chemically oxidizable matter in water. The traditional method for COD determination consists of oxidizing the organic matter of the sample, is done by adding a known amount of oxidant, refluxing at high temperature on open containers and titrating the excess oxidant. However, the method require the time-consuming process of heating samples to achieve more complete oxidation. It also consume some expensive(Ag2SO4) and toxic(HgSO4) chemicals.
Therefore the goal of this study is to develop continuous and rapid determination of COD by microware digestion. In this system, the absorbance of Cr3+ generated during sample oxidation is measured at 600 nm, Chemical oxygen demand can be obtained in just 23 second. The optimal experimental condition are: 0.5 mL 0.141 M silver nitrate solution; 3 mL 0.55 % sulfuric acid solution; 0.75 mL 0.0417 M potassium dichromate solution and 2 mL sample.
The calibration graph is liner in the range of 0~500 mg/L. The interference of Cl- can be removed up to be moved up to 4700mg/L. The method has a good precision and accuracy for KHP solution , glucose solution and sodium oxalate solution. There is results for a COD certified reference materials were in good agreement with the certified COD value. The viability of this method is demonstrated by analyzing four kinds of industrial wastewater, and the results obtained by using the method presented exhibit good agreement with those given by the standard method of COD determination, and the relative error is less than 10 %.
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