Adsorption And Desorption Of Surfactants And The Effects On Activities Of Microbe And Enzymes In Soils

In order to use surfactants reasonably and to find out the environmental effects of typical surfactants, adsorption and desorption of anion surfactant SDBS (sodium dodecyl benzene sulfonate) and non-ion surfactant AE (alkylethoxylate) in two typical soils (red soil and paddy soil) in Hunan, southern China, were studied by using oscillatory equilibrium methods and the effects on surfactants activities of microbe and enzymes in the tested soils were studied through incubation experiments. The main results showed as the follows:1. Adsorption processes and desorption processes of SDBS in the tested soils reached equilibrium within 1-1.5 h. Under the experimental condition (amount of SDBS added was from 0 to 2000 mg/L), adsorption capacities increased with the increasing amount and equilibrium concentration of SDBS added and adsorption capacities near to saturation at 1000 mg/L (red soil) or 800 mg/L (paddy soil). Freundlich adsorption model and two-step adsorption model could be used to describe SDBS isotherm adsorption curves. Adsorption capacities in the red soil were more than those of paddy soil under the same condition. It was very difficult to desorb SDBS, which was adsorbed in the soils. There was a positive correlation between adsorption and desorption, and under the same conditions SDBS adsorbed in paddy soil was desorbed more easily than that in red soil. Temperature and pH affected the adsorption capacity of SDBS: adsorption capacities decreased with the increasing of temperatures and pH values, but isotherm adsorption curve forms similituded.2. Adsorption processes and desorption processes of AE in the tested realized very quickly and it could reach equilibrium within 1-2 h. Under the experimental condition (amount of AE added was from 0 to 600 mg/L), adsorption capacities increased with the increasing amount and equilibrium concentration of AE added then near to saturation. Langmuir adsorption model, Freundlich adsorption model and two-step adsorption model could be used to describe AE isotherm adsorption curves. Adsorption capacities in the red soil were more than those of paddy soil under the same condition. It was very difficult to desorbe AE adsorbed in the soils. There was a positive...