Study On Adsorption-Desorption Characteristics Of Ammonia Nitrogen In The Sediment Of Black Odorous Water

Black odorous water body not only seriously affects the city's cityscape.It also poses a huge hazard to the living environment and health problems of residents in the basin.Ammonia nitrogen plays an important role in water.Directly affect water quality.Therefore,it is of great practical significance to study the adsorption-desorption characteristics of ammonia nitrogen in water by black odorous water sediment.This paper takes the 0²0cm sediment of the surface of Xianren River,a typical black-smelling water tributary of Dongliao River,as the research object.Through laboratory simulation tests,The adsorption-desorption characteristics of ammonia nitrogen in the bottom of black odor water body were discussed.The physicochemical analysis of the overlying water,interstitial water and sediment in the four sampling points of the Xianren River?upstream of Tianjiabing Middle School,downstream of Tianjiabing Middle School,Taiyangsheng,and Liaohekou?shows that the pollution of the Xianren River is extremely serious.Exceeding the national V-class water standard,the total nitrogen content of the overlying water on the Xianren River is between 8.52 and 13.97 mg·L^-1,with an average value of 8.23 mg·L^-1.The content of ammonia nitrogen was between1.71⁹.17 mg·L^-1,and the average value reached 6.38mg·L^-1.The content of ammonia nitrogen in the interstitial water is much higher than that of the overlying water,which is between 1.45 and 39.52 mg·L^-1,and the average value is 26.41 mg·L^-1.Under the same point conditions,the ammonia nitrogen content in the 10²0cm interstitial water is greater than the ammonia nitrogen content in the 0¹0cm interstitial water.Four sediment samples from two sampling points?upstream of Tianjiabing Middle School and into Liaohekou?at 0¹0cm and 10²0cm were taken to study the characteristics of adsorption-desorption of ammonia nitrogen in Black odorous water body sediment.The results show that the kinetic adsorption process of ammonia nitrogen adsorption in the sediment of Black odorous water body is mainly completed within the first 30 minutes,and the adsorption rate decreases after 60 minutes until it basically tends to adsorb equilibrium.The adsorption amount of each sampling point was between 2.94³.93g·kg^-1,and the average value was 3.53g·kg^-1.Under the same depth of sediment conditions,the maximum adsorption capacity of the sediment in the Liaohekou is greater than the maximum adsorption of the sediment in the upstream of Tianjiabing Middle School.Under the same point conditions,the maximum adsorption capacity of 10²0cm sediment is greater than the maximum adsorption of0¹0cm sediment.The experimental data were fitted with the first-order reaction kinetics model,the quasi-secondary kinetic model and the intraparticle diffusion kinetics model.The fitting results showed that the kinetic adsorption process and quasi-secondary dynamics of ammonia nitrogen in the sediment of Black odorous water body has a good simulation effect,and its equilibrium adsorption capacity is between3.255³.723g·kg^-1,and the change trend is 10²0cm Liaohekou>10²0cm upstream of Tianjiabing Middle School>0¹0cm into the Liaohekou>Tian Jiabing.The adsorption kinetics of ammonia nitrogen in the sediments of Black odorous water body are inferior to the first-order reaction kinetics model and the intra-particle diffusion model.It indicates that the adsorption process of ammonia nitrogen by sediment is affected by many factors and controls the rate of ammonia nitrogen adsorption.Not internal diffusion.In the experimental concentration range(0-200mg·L^-1),as the ammonia-nitrogen equilibrium concentration of the solution increases,the adsorption amount of ammonia nitrogen in the sediment increases linearly,and desorption occured in the sediment of the low concentration zone(<6mg·L^-1).Under the same depth conditions,the adsorption capacity of the upstream sediment of Tianjiabing Middle School is stronger than that of the sediment in the Liaohekou.Under the same point condition,the adsorption capacity of 10²0cm sediment is stronger than that of0¹0cm sediment.The Langmuir model was used to fit the experimental data of sediment adsorption thermodynamics,and the fitting effect was good?R²>0.91?.The maximum adsorption capacity of the sediment to ammonia nitrogen was 17.575⁷2.464g·kg^-1,and the maximum appeared in Tianjiabing Middle School 0¹0cm;the Henry model can also be used to fit the adsorption process of ammonia nitrogen in the sediment of Black odorous water body?R²>0.97?.The concentration of ammonia-nitrogen adsorption-desorption equilibrium concentration varies greatly from 1.42 to5.73g.kg^-1,the adsorption-desorption equilibrium concentration of the sediment in the Liaohekou is greater than Tianjiabing Middle School.The Freundlich model can also describe the thermodynamic adsorption of ammonia nitrogen on the sediment?R²>0.95?.The fitting result coefficient is 1/n>1,which indicates that the adsorption process of ammonia on the sediment is not easy.The desorption process of ammonia nitrogen in Black odorous water body is a composite kinetic process,which is characterized by rapid desorption within 100 min,which is a fast reaction phase.After 150 min,the desorption rate gradually decreases until it basically desorbs the equilibrium,which is the slow reaction stage.The maximum desorption amount is between 0.19⁰.38g·kg^-1,and the variation range is large,and the average value is 0.27g·kg^-1.The trend is 10²0cm Liaohekou>0¹0cm Liaohekou>10²0cm in the upper reaches of Tianjiabing Middle School>0¹0cm in Tianjiabing Middle School.Under the same point condition,the maximum desorption of 10²0cm sediment is greater than 0¹0cm sediment.The sediment desorption data was fitted using a first-order reaction kinetics model,a quasi-secondary kinetic model,and an intraparticle diffusion kinetics model.The relevant parameters of the first-order reaction kinetics model are 0.6377<R²<0.8893.The relevant parameter of the quasi-secondary kinetic model is 0.9953<R²<0.9990.The relevant parameter of the intraparticle diffusion kinetic model is 0.8264<R²<0.9853.The quasi-second-order kinetic equation can well represent the desorption process of ammonia nitrogen in the sediments of Black odorous water body.The equilibrium analytical amount is between 0.208⁰.384mg·kg^-1,and the trend is 10²0cm Liaohekou>0¹0cm Liaohekou>0¹0cm upstream of Tianjiabing Middle School>0¹0cm Tianjiabing Middle School.At the same point,the equilibrium suction of 10²0cm sediment is greater than 0¹0cm sediment.