Study On The Retardation Effect Of Nitrobenzene In River Sediments

Nitrobenzene is an important chemical raw material,but it is a kind of organic pollutant which is harmful to human body.Once nitrobenzene enters the environment,it will cause serious pollution to the environment.The blocking effect of nitrobenzene in river sediment has a great influence on its migration.Block through the adsorption and desorption experiments and soil column infiltration experiments of nitrobenzene in sediments of Weihe,the retardation factor,which provide important parameters for migration of nitrobenzene in river sediments.First of all,the adsorption behavior of nitrobenzene in Weihe sediments and its influencing factors were studied.The results showed that the adsorption kinetics of different particle size of sand sediments of Weihe experienced rapid adsorption,slow adsorption and adsorption equilibrium phase.In the concentration range of 0-10.07mg/L,the isothermal equilibrium adsorption experiments with different adsorption isotherm fitting of the experimental data,calculate the relevant adsorption parameters,different media size by using a variety of experimental results show that the adsorption isotherm fitted the experimental data,the adsorption type is composed of a linear equation and the fitting degree of Langmuir(H-L)better.At the same time to calculate the distribution coefficient of Kd in different media size.To calculate the static retardation factor of Rd,sand A(<0.1mm)Rd=38.52,sand B(0.1mm-0.3mm)Rd=30.93,sand C(0.3mm-0.5mm)Rd=23.07.At the same time in different pH,temperature,initial concentration,on the adsorption effect was studied,the results show that pH=1.2-11.3 range,with the increase of p H,the adsorption capacity of nitrobenzene increased first and then decreased,in the range of pH=6.8-7.6,the adsorption capacity of nitrobenzene is the largest,i.e.about 9.47 mg/kg.The higher the temperature,sediment the equilibrium adsorption of nitrobenzene was slowly increased at first and decreased at 15 ?-17 ?,maximum adsorption capacity,i.e.about 9.39 mg/kg.Nitrobenzene concentration in a certain range,with the increase of concentration,was adsorbed by the sediment volume increases and reaches the maximum at the equilibrium adsorption amount when the concentration of 6.69mg/L,9.42mg/kg.Secondly,the desorption behavior of nitrobenzene in Weihe sediments and its influencing factors were studied.The desorption kinetics results show that with the increase of nitrobenzene desorption time increases gradually,until the adsorption desorption equilibrium.The adsorption desorption hysteresis coefficient HI is calculated by the experimental data of isothermal equilibrium adsorption and desorption.According to the different media size lag coefficient HI,sand A> sand B> sand C.The factors affecting the desorption experiment results show that with the increase of pH,desorption increased first and then decreased,pH=6.8-7.6,desorption equilibrium reached the maximum,i.e.about 2.72 mg/kg.With the increase of temperature of desorption of nitrobenzene increased gradually,the temperature is about 17 degrees,the maximum desorption equilibrium i.e.about 2.76 mg/kg.The initial concentration of nitrobenzene in a certain range,the higher the concentration of nitrobenzene nitrobenzene,the desorption amount is larger,when the concentration is 6.78mg/L,the desorption of nitrobenzene reached the maximum,2.78mg/kg.The calculation formula of the retardation factor can be seen,the bigger the Kd,the retardation factor is bigger,the bigger the Kd,the adsorption amount of sand is also bigger.The calculation formula of lag coefficient,the more the adsorption,desorption of relatively small lag coefficient is larger.Therefore,the retardation factor and hysteresis coefficient have similar effects on the migration law of nitrobenzene in sediments.At the end of the soil column infiltration experiments,the highest percentage of sand B.Using sodium chloride as a tracer.The breakthrough curve has been obtained.Then the nitrobenzene column infiltration experiment is carried out.According to the experimental data,the migration curve of nitrobenzene is obtained.The migration velocity of nitrobenzene is calculated,and the dynamic retardation factor Rd=14.8 is calculated.The static and dynamic retardation factor difference of nitrobenzene in sand B in large.This is because the static retardation factor is obtained under laboratory conditions,and site conditions are quite different,and the dynamic retardation factor is obtained in the simulations under natural conditions,is closer to the reality,so the dynamic block factor is more accurate.