| Mn2+(cation)﹑Cr (Ⅵ)(anion) and2,4-dichlorophenol (numerator) are environmentalpollutants with existence of different forms. They have a high toxicity, long residual time, lowvolatility, and other non-degradable or biodegradable characteristics. Zhongwei region islocated in the Loess Plateau. Loess soil is an important venue in the area of agriculture,industry, forestry, animal husbandry and urban construction, the area is an importantproduction base of manganese,and there are many processing enterprises of chromium and2,4–dichlorophenol here.Study of the adsorption, transport, transformation rules of Mn2+﹑Cr(Ⅵ) and2,4-dichlorophenol in Loess soil, can provide important theoretical and practicalvalue for predicting their potential contamination in Zhongning loess soil and groundwater.We selected two differences soils(TM-1and TS-2) from Zhongwei for the study, Analyzed thecomposition and basic physical and chemical properties of the two soils. Studied the kineticsand thermodynamics laws of the loess soil adsorpiting the Mn2+﹑Cr (Ⅵ) and2,4-dichlorophenol. Tested the adsorption enthalpy change process, entropy, Gibbs freeenergy and other important thermodynamic state function and determined the adsorptionmodels. Throμgh the one-dimensional diffusion test, established a mathematical model ofMn2+transport and transformation in saturated loess soil, Determining the modelparameters.Moreober, the results determined form those modes has a well coherence with theexperiments,which indicated that the diffusion modes can be used to simulate of Mn2+in theloess soil well. Specific results are as follows:1.There is a big difference of the loess siol adsorpiting the Mn2+﹑Cr (Ⅵ) and2,4-dichlorophenol.①The adsorption capatiy of the loess soil is Mn2+>2,4–dichlorophenol> Cr (Ⅵ). Forthe same pollutants,the adsorption capacity is TM-1>TS-2. Calculated by Langmuir equationthe average absorption quantity of lossial soil to Mn2+is1250mg/kg to TM-1and714mg/kgto TS-2.②Both△G0and△H0are negative, so the adsorption of2,4-dichlorophenol and Mn2+inloess belongs to an exthernal spontaneous rection.and it also says the adsorption can beautomatically.△S of the2,4-dichlorophenol is negative, indicating that the adsorbed molecules tend to make micro-ordered; earth△S of the Mn2+is positive, indicating anincrease of the degree of disorder in the reaction system.2.The migration rate of Mn2+﹑Cr (Ⅵ) and2,4-dichlorophenol in the loess soil isdifferent. The migration of Mn2+,Cr (Ⅵ) and2,4–dichlorophenol in loessial soil relate toThe soil itself. The order of migration are TS-2>TM-1, Mn2+<2,4–dichlorophenol<Cr (Ⅵ).The soil purification capacity to Mn2+is much greater than2,4-dichlorophenol and Cr (Ⅵ).3.The Mn2+vertical migration in loess soil by the hydrodynamic dispersion, adsorptioninteraction.For the TM-1, the adsorption coefficient Kdl=5.15cm3/g, retardation factor R1=25.75,diffusion coefficient D1=0.00618m2/d, the average velocity V1=2.08m1/min; adsorptioncoefficient Kd2=2.41cm3/g, retardation factor R2=18.64, diffusion coefficient D2=0.00368m2/d, the average velocity V2=2.3ml/min. The establishment of a mathematicalmodel of Mn2+ground water distribution in space and time, and the simulated andexperimental measured values are compared and found that both coincide better, indicatingthat the hydrodynamic dispersion model can simulate and predict good Mn2+in groundwaterin porous media the spatial and temporal distribution. |
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