Kinetics Of Adsorption And Desorption Of Copper In Reclaimed Soil By Small Molecular Organic Acids

Copper is one of the micro-toxic heavy metals,and excessive intake is easy to cause poisoning.The adsorption behavior of copper on soil is the main process affecting copper mobility,biological effects and fate.This paper takes the reclaimed soil of Panyi Mine in Huainan City as the research object,Choosing Cu as the typical representative of pollutants,and analyzes the basic physical and chemical properties and copper pollution of reclaimed soil.The adsorption-desorption mechanism and kinetic characteristics of heavy copper in reclaimed soils were studied,and the effects of small molecular organic acids on the adsorption-desorption of heavy copper were also studied.The main conclusions are as follows:1.The adsorption-desorption characteristics of copper in the soils(1)There is a strong correlation between copper concentration in equilibrium solution and copper adsorption capacity of reclaimed soil.With the increase of copper concentration in equilibrium solution,the adsorption capacity increases.The relationship between desorption amount is the same,but the increase of desorption amount is not as obvious as that of adsorption amount.We choose the most suitable isothermal model to fit the experimental data within the concentration range set by the experiment.It can be found that Langmuir model is basically suitable for describing the adsorption(desorption)of copper in the tested soils,and the number of fitting linear correlation(R~2)has reached a very significant correlation level.(2)Adsorption and desorption of copper in different types of soils have the same kinetic characteristics.The adsorption capacity of copper in soil increased sharply at the initial stage of the adsorption process,then the adsorption rate slowed down gradually,and the slope of the adsorption kinetics curve approached zero gradually,which accorded with the BET theory.The desorption kinetics is similar.Because the properties of different types of soils are different,the optimal kinetics models of copper adsorption are also different,which reflects the influence of soil properties on copper adsorption mechanism.Generally speaking,the parabolic diffusion model is the best model for both adsorption and desorption kinetics experiments.2.Effects of citric acid(malic acid)on Copper adsorption-desorption by reclaimed soils(1)The effect of citric acid(malic acid)on the adsorption-desorption isotherm of copper in soils showed that both citric acid and malic acid could reduce the adsorption of Cu by reclaimed soil under the given experimental conditions,and the inhibition degree of citric acid was higher than malic acid.Both malic acid and citric acid can promote the desorption of Cu by reclaimed soil,and the promotion of malic acid is higher than that of citric acid.By comparing the fitting parameters of soil adsorption-desorption copper isotherms,it was found that in the presence of small molecular organic acids,adsorption of Cu by reclaimed soils conforms to Langmuir EXT2 model,desorption conforms to Temkin model.all of them reached significant correlation level.(2)4 mmol/L citric acid reduced the adsorption of Cu on reclaimed soil more than 2 mmol/L citric acid;On the contrary,4 mmol/L malic acid promoted the desorption of Cu by reclaimed soil more than 2 mmol/L malic acid.Through a large number of data fitting and comparison,it was found that the sorption(desorption)of reclaimed soils for Cu in the presence of citric acid(malic acid)conformed to Langmuir model.Figure[30]table[16]reference[81]...