| In view of Lou soil modified with dodecyl-dimethyl-betaine(BS-12) have good results on adsorption of heavy metals and organic pollutants, and clay mineral modified with two modifiers have better results than single modifier on adsorption of organic pollutants. Using Lou soil as sample, Lou soil is modified with different proportions mixture of BS-12 and sodium dodecyl sulfate(SDS) according to the soil cation exchange capacity. The kinetics and thermodynamics adsorption of phenol and cadmium ions on soil samples modified with different ratio modifiers are studied, the modified mechanism of the modifier on soil and adsorption mechanism of cadmium ions and phenol on modified soils was indicated. The main study conclusions were as follows:1. After Lou soil clay layer soil samples modified by mixture of BS-12 + SDS, the adsorption velocity of cadmium ions and phenol on them are increased obviously than that of CK. Their adsorption kinetic curves reach balance with 24 hours. The adsorption process of cadmium ions and phenol are both divided into two stages, fast adsorption and slow adsorption, in which the total adsorption velocity is primarily decided by the fast adsorption while it is affected little by slow adsorption respectively. The Elovich kinetic model is the best model to describe the adsorption kinetic curves of cadmium ions and phenol on modified soil, furthermore, the fitted parameter A,B are both the characteristics value that can be used to describe their adsorption velocity on modified soils.2. The adsorption velocity parameters of phenol, initial-adsorption-velocity(V0.17), fast- adsorption-velocity(Vf),total-adsorption-velocity (Vt) and conversion-adsorption-velocity (Vc) have a same sequence in different modification treatments, i.e. ordered by 100B+25S>100B+50S>50B+25S>50B+50S>CK at two experimental temperature, and the adsorption velocity parameters V0.17,Vf,Vc,Vt of phenol on modified soils are bigger than that on CK. The orders of slow-adsorption-velocity (Vs) are 100B+25S>50B+25S≈CK>50B+50S≈100B+50S. The time of conversion (tc) on modified soils are less than that on CK. The adsorption velocity parameters V0.17,Vf,Vc,Vt are increased by the increase of the temperature, and the ratio of the modifier BS-12 and SDS have different influences on adsorption velocity parameters V0.17,Vf,Vc,Vt of phenol on modified soils respectively.3. The adsorption velocity parameters of cadmium ions, V0.17,Vf,Vt,Vc have a same sequence in different modification treatments, i.e. ordered by 100B+50S>100B+25S>50B+50S>50B+25S>CK at two experimental temperature, and the adsorption velocity parameters V0.17,Vf,Vc,Vt of cadmium ions on modified soils are bigger than that on CK. The consistences of Vs are worse and the differences of tc are little. The temperature has little influence on adsorption velocity parameters V0.17,Vf,Vc,Vt of cadmium ions on modified soils respectively. The adsorption velocity V0.17,Vf,Vc,Vt of cadmium ions on modified soils are increased respectively by the increase of the ratio of the modifier BS-12 and SDS.4. After Lou soil clay layer soil samples modified by mixture of BS-12 + SDS, the adsorption capacity of phenol and cadmium ions are increased obviously than that of CK. The equilibrium adsorption capacity of phenol exists the following order: 100B+25S>100B+50S>50B+25S>50B+50S>CK with single and complex treatment at two experimental temperature. The equilibrium adsorption capacity of cadmium ions exist the following order: 100B +50 S> 100B +25 S> 50B +50 S> 50B +25 S> CK with single and complex treatment at two experimental temperatures. The adsorption isotherms are linear, Henry model is the best model to describe the equilibrium adsorption isotherm of phenol on modified soils, and which is same that the orders of partition coefficients k and equlibrium adsorption capacity. The adsorption isotherms are L tape, the single-point Langmuir model is the best model to describe the equilibrium adsorption isotherm of cadmium ions on modified soil. And that is same that the orders of adsorption intensity b and equlibrium adsorption capacity on the ratio of the modifier.5. The adsorption of single treatment phenol shows warming effect, and that of complex treatment phenol shows "thermal passivation" phenomenon on modified soils. The adsorption capacity of complex treatment phenol is bigger than that of single treatment on experimental soils, indicating the presence of cadmium ions could promote phenol adsorption on experimental soils. The adsorption capacity of phenol on experimental soils is decreased by the increasing of SDS modified ratio, and that is increased by the increasing of BS-12 modified ratio.6. The adsorption capacity of complex treatment cadmium ions is smaller than that of single treatment on experimental soils, indicating the presence of phenol could impede cadmium ions adsorption on experimental soils. The adsorption capacity of cadmium ions on experimental soils is increased by the increasing of the modified ratio of the modifier. The adsorption of cadmium ions shows little warming effect in single treatment and cadmium ions + phenol complex treatment on experimental soils. The adsorption rates show that the adsorptions of cadmium ions have two stages, and the cut-off point of two stages is that the initial concentration of cadmium ions is 100 mg·L-1. 7. The modification mechanism of the modified soils are that the positive charge side of BS-12 connect to the negative charge side of the soil surface through electrostatic force, whose long carbon chain and the negative charge side extend outward. SDS connects with BS-12 through hydrophobic bonding, whose negative charge side extends outward. The adsorption of phenol on modified soils is primarily decided by the hydrophobic adsorption. The cadmium ions connect the negative charge side of BS-12,SDS after the complex treatment, and to lower the repellent action of the soils surface and improve the hydrophobic adsorption of phenol, leading to equilibrium adsorption capacity of complex treatment is bigger than that of single treatment. The adsorption of cadmium ions on modified soils is primarily decided by the electrostatic adsorption. The phenol connect the organic phase of BS-12,SDS after the complex treatment, and to higher the hydrophobicity of the soils surface and the resistance of cadmium ions adsorption, leading to equilibrium adsorption capacity of complex treatment is lower than that of single treatment.
|
PDF Full Text Request