The Development And Application Of COD Rapid Analysis Technology

Chemical oxygen demand(COD) refers to the acid environment, heat, oxidation of reducing substances such as organic matter in water, consumed by the quantity of oxidant, and conversion into oxygen concentration, in mg/L. Is to evaluate the comprehensive index of water body pollution degree, is a printing and dyeing, paper making, electroplating, chemical fiber, steel industry such as emissions of industrial waste water and living sewage water quality monitoring analysis shall be measured in a project, is also one of the important indicators of pollutant total amount control.At present, various cities, county environmental monitoring station, and analysis the method of chemical oxygen demand(cod) most of enterprises by national standard method, potassium dichromate method and coulomb method to use fewer(surface water) are commonly used to determine. Potassium dichromate method exists digestion time and high cost of experiment as well as the secondary pollution caused by mercury, chromium, etc. Coulomb’s law relative potassium dichromate method has the following advantages: short digestion time, the experiment of low cost, less secondary pollution, etc. But for complex samples containing chloride ion or composition, can cause contamination of platinum electrode, interfere with the finish. So developing a pollution-free COD quick analysis has theoretical significance and application value.This paper reference to potassium dichromate method and coulomb method, explore a fast method of determination of chemical oxygen demand(cod). After many experiments show that the rapid analysis of ingredients not complicated water samples with good accuracy and precision, save a lot of time(15 min) digestion and reagents. But for chloride ions content is higher, the complicated composition of water samples, fast analysis method is difficult to deal with. Therefore, rapid analysis method for the improvement, we first use silver nitrate to remove the chloride ions in water samples, and then increase the concentration of a solution of potassium dichromate and other reagent dosage, then switch to mixed acid(sulfuric acid-phosphoric acid) to digestion. Through many different types of water samples and standard samples were analyzed, and shows the result of improved rapid analysis method to measure the relative with potassium dichromate method results deviation is below 10%, shows that the method can basic reaction effluent COD of true value. At the same time, this paper research on the silver in waste recycling, make its can be recycled, reduce the cost analysis and test, to avoid secondary pollution.A statistical analysis of data, it is concluded that improved COD rapid analysis method detection limit and precision, and scale model of top- down technical method to analyze the statistics, the results showed that all the data in a controlled area, within the scope of the controllable, test results have a certain accuracy, and it is concluded that the method calculation formula of uncertainty.Modified rapid analysis with experimental device to take up the space is little, short analysis time, analysis the cost is low(less reagent dosage and recycling silver), simple operation, to avoid secondary pollution, the advantages of wide scope of application, this is a new clean analysis method for determination of COD, believe that can be used widely in the environmental monitoring system and the enterprise.