Studies On The Adsorption Of Phenol And Cd²⁺ In Soil Modified With BS-18

The adsorption of phenol and Cadmium ion on Lou soil modified with amphoteric surface modifying agent-Octadecane-Betaine(BS-18) were conducted in single and complex condition. The mechanism of adsorption kinetics and the thermodynamic characters were analysed, the conclusions were showed as following:1. After modified with BS-18, the results showed that the single treatment and complex treatment at 20 and 40℃, all the velocity parameters of modified soil samples were greater than the unmodified soil samples, and the velocity increased as the increase of the modified proportion as a whole. It was showed that the adsorption velocity of the soil samples on Cadmium ion could be accelerated significantly by BS-18. Adsorption reaction was divided into two stages: fast adsorption and slow adsorption, total-adsorption-velocity of the overall reaction was decided both by reaction rate of the fast-adsorption-velocity and the slow-adsorption-velocity jointly. As the temperature rising, the total average speed of the single treatment to Cadmium ion remained basically unchanged, on the contrary, that of the complex treatment decreased. The average rate of the overall reaction could be speed up when phenol was added at 20℃, but it was slowed down at 40℃. As for the description on the experimental data of the adsorption kinetics, the two-constant equation model was the best one, and the model parameters A and B could be used to describe the adsorption rate.2. After modified with BS-18, the adsorption of Cadmium ion was increased obviously, the adsorption capacity order was as follows: 150%BS-18>100%BS-18>50%BS-18>25%BS-18>CK. And the adsorption amount in same soil decreased when temperature rising in complex treatments, on the contrary, that of the single treatment increased. The adsorption amount could be slowed down when phenol was added, but it was correlated with equilibrium concentration at 40℃. BET model was the best model to describe the equilibrium adsorption curves of Cadmium ion on modified soil. The results of thermodynamics showed that adsorption is spontaneous with entropy increment and enthalpy that decreased in single treatment and increased in complex treatment.3. The results showed that all the velocity parameters of phenol of modified soil samples were greater than the unmodified soil samples, and the velocity increased as the increase of the modified proportion as a whole. It was showed that the adsorption velocity of the soil samples on phenol could be accelerated significantly by BS-18. Adsorption reaction was divided into two stages: fast adsorption and slow adsorption, total-adsorption-velocity of the overall reaction was decided by reaction rate of the fast-adsorption-velocity. As the temperature rising, the total average speed were decreased. The average rate of the overall reaction could be slowed down when Cadmium ion was added. As for the description on the experimental data of the adsorption kinetics, the two-constant equation model was the best one, and the model parameters A and B could be used to describe the adsorption rate.4. The adsorption of phenol was increased obviously after modified with BS-18, the adsorption capacity order was as follows: 150%BS-18 > 100%BS-18 > 50%BS-18 >25%BS-18>CK. And the adsorption amount in same soil decreased when temperature rising. The adsorption amount could be slow down when Cadmium ion was added. Henry model was the best model to describe the equilibrium adsorption curves of phenol on modified soil. The results of thermodynamics showed that adsorption is spontaneous with entropy increased and enthalpy decreased.5. The adsorption mechanism of Cadmium ion on soil samples modified with BS-18 was mainly the electric adsorption by the negative charge on the hydrophilic groups and the adsorption mechanism of phenol was primarily decided by the hydrophobic adsorption of organic phase.