Study On Characters Of Nitrogen And Phosphorus Adsorption And Desorption Of Sediment In Ganjiang Rive

Water is the source of life, the key of production, and the foundation of ecology. However, with the development of social economy, water environment is under constantly threat. Among them, the eutrophication is a major aspect. While nitrogen and phosphorus are the important factors of eutrophication, so the key to prevent and control eutrophication is to control the concentration of nitrogen and phosphorus in water.Sediment has strong adsorption ability to the chemicals in water, including nitrogen and phosphorus, so sediment can adjust the concentration of nitrogen and phosphorus in water. According to solid adsorption theory and adsorption principle, by taking the sediment in Ganjiang Rive as the research object first, the paper designs adsorption and desorption dynamic experiments and equilibrium adsorption experiments in the static condition, and adsorption experiments under the dynamic condition, all about the nitrogen and phosphorus adsorption of sediment. Then according to the results of the experiments, draw the adsorption dynamic curves, adsorption isotherms and desorption dynamic curves, fit the experimental results by Henry, Langmuir and Freundlich models correspondingly, and obtain the following conclusions:Firstly, the nitrogen adsorption of sediment reaches balance basically in about 4～6 h, and the phosphorus adsorption of sediment reaches balance basically in about 2～4 h. The nitrogen and phosphorus desorption of sediment achieve basic balance in about 8 h. Adsorption and desorption processes are both made of rapid reaction and slow reaction, the former happens at the beginning of experiments (a few minutes to hours), and the latter happens later and lasts for a long time.Secondly, the initial concentration of nitrogen and phosphorus, and the concentration of sediment affect the adsorption and desorption of sediment. The adsorption capacity increases when the initial concentration increases. And when sediment concentration increases, the adsorption and desorption capacity decrease.Thirdly, in the adsorption dynamic experiments under the static condition, the processes of adsorption of nitrogen and phosphorus by sediment can be fitted preferably by Langmuir model, the fitting correlation coefficients for nitrogen are above 0.85, and the fitting correlation coefficients for phosphorus are above 0.8. In equilibrium adsorption experiments, Henry and Langmuir models can fit isothermal adsorption of nitrogen by sediment preferably, correlation coefficients are above 0.9 basically; it is better to fit isothermal adsorption of phosphorus by sediment by Langmuir model than Freundlich model, the fitting correlation coefficients by Langmuir model are above 0.9, and the fitting correlation coefficients by Freundlich model are above 0.8.Fourthly, the processes of nitrogen and phosphorus desorption of sediment can be simulated preferably by Langmuir model, the fitting correlation coefficients for nitrogen are above 0.8, and the fitting correlation coefficients for phosphorus are above 0.75. In addition, the higher the sediment concentration is, the better the result of fitting is.Fifthly, when the velocity is 0.03 m/s, the concentration of nitrogen and phosphorus are degressive tendency and the adsorption capacity are increasing trend with time, and both tend to a numerical. At the beginning of experiments, adsorption process is relatively quick, then adsorption process gradually slow until to be basically equilibrium state.Sixthly, the dynamic adsorption of nitrogen and phosphorus processes can be fitted preferably by Langmuir model, the fitting correlation coefficients are above 0.85.