Determination of landfill leachate COD by UV-1200 ultraviolet spectrophotometry

Determination of COD in landfill leachate by ultraviolet spectrophotometry

UV spectrophotometric determination of landfill leachate COD Keywords: UV spectrophotometry; landfill leachate; U.S. instrument UV-1200
The main characteristics of landfill leachate are high COD concentration, CODcr up to 80,000 mg / L, complex composition, in addition to a certain color and suspended matter, if directly discharged, will cause serious pollution, so the treatment of landfill leachate More and more people are paying attention. An important indicator for evaluating the treatment effect is the COD value of landfill leachate.
The standard method for COD determination, potassium dichromate method, is reliable and reproducible. However, the method is cumbersome to operate, time-consuming, power-consuming, large amount of reagents, and the use of highly toxic mercury sulfate, the secondary pollution is more serious. Therefore, it has become a goal of people to explore a method that is fast, energy-saving, reagent-saving, less polluting, reliable, and suitable for batch determination of COD in water samples.
Ultraviolet spectrophotometry uses a wavelength range of 200 to 400 nm and can be used for unsaturated hydrocarbons and compounds with asymmetric electrons (including some inorganic compounds), especially for the analysis and study of compounds containing conjugated systems. Most of the components of landfill leachate have unsaturated hydrocarbon bonds or asymmetric electrons. The composition of the material contained in landfill leachate generally does not change much, so UV absorbance can be used as a comprehensive indicator for evaluating organic pollution of water quality. If the UV absorbance of the landfill leachate can be measured to replace the cumbersome COD measurement or as an approximate estimate of the COD value, the measurement time can be shortened, chemical reagents are eliminated, and the COD measurement procedure is simplified, thereby saving costs.
We obtained the landfill leachate water sample from the regulation tank of a garbage sanitary landfill without filtering. At the same time, the absorbance of the UV spectrophotometer was directly measured and the COD value was determined by the national standard method. The mathematical statistics method was used to obtain the two. A linear regression equation between.
1 test
1.1 Main instruments and reagents UV-visible spectrophotometer UV-1200, produced by Meifang (China) Instrument Co., Ltd. 1cm quartz cuvette. Distilled water.
1.2 Test method The obtained leachate water sample was diluted with distilled water by a certain multiple. At a wavelength of 254 nm, the absorbance of the diluted water sample was measured with a 1 cm cuvette and distilled water as a reference, and the absorbance of the diluted water sample was measured with a 752 type UV-visible spectrophotometer. The COD value of raw water is determined by the national standard method.
2 results and discussion
2.1 Determination of absorption wavelength When the absorbance of the solution to be tested is determined by ultraviolet spectrophotometry, the absorption wavelength should first be selected. When the absorption wavelength is selected, the solution to be tested should generally be scanned at full wavelength, and the wavelength at the absorption peak on the scan curve is preferably selected according to the scanning result. To this end, the landfill leachate with a COD concentration of 1814.4 mg/L was selected, diluted 10 times, and 3 mL was placed in a cuvette with a path length of 1 cm. The distilled water was used as a blank water sample, and the full wavelength was performed in 200-400 nm. Scan, the scan results are shown in Figure 1.